Application of Nanostructured Materials for Energy ...

Application of Nanostructured Materials for Energy and Environmental Technology


Editors V. Rajendran P. Manivasakan K.E. Geckeler

© KSR Group of Institutions, 2015 First Published, 2015 All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage or retrieval system, without prior permission in writing from the copyright holder. No responsibility for loss caused to any individual or organization acting on or refraining from action as a result of the material in this publication can be accepted by Bloomsbury India or the author/editor. BLOOMSBURY PUBLISHING INDIA PVT. LTD. New Delhi London Oxford New York Sydney ISBN: 978-93-85436-91-8 10 9 8 7 6 5 4 3 2 1 Published by Bloomsbury Publishing India Pvt. Ltd. DDA Complex LSC, Building No. 4, 2nd Floor Pocket 6 & 7, Sector – C Vasant Kunj, New Delhi 110070 Typeset by fortune graphics, Naraina, New Delhi Printed at anvi composers, Paschim Vihar, New Delhi

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Foreword The past few decades have seen unprecedented advancements in the field of nanotechnology with spectacular developments in a wide area of Material Science. Currently, nanotechnology is a fast growing field with a broad spectrum of applications and it is appreciated that the Centre for Nano Science and Technology (CNST) of the K.S. Rangasamy College of Technology (KSRCT) has undertaken an initiative to organize an International Conference on Nanomaterials and Nanotechnology (NANO-15) with a special topic on ‘Research to Innovations to Technology Transfer’ in India, especially at Tamil Nadu. Based on its good infrastructure and human resources, CNST develops R & D activities with international standards by many funded projects and research publications. KSRCT collaborates with academic institutions and national and international research laboratories/ industries of high reputation. The conference features many plenary and key note addresses presented by invited speakers and more than 1100 delegates from around the world are participating, interacting, and discussing the exciting and rapidly developing aspects of Nano Science and Technology. I trust that this conference will be an ideal platform for the presentation and discussion of new concepts and developments of new functional nanomaterials and their applications in new devices and sensors. NANO-15 provides a forum to discuss eco-friendly technologies and promote interactions and collaborations between the delegates. I appreciate that the organising team publishes peer reviewed papers in six independent books. The articles therein will describe new ideas in a rapidly developing field and so stimulate further progress. I am pleased to write a foreword for these books to be published during NANO-15 and wish the Conference participants a fruitful and enjoyable stay in India and I want to thank the organizing team for the their kind helpfulness and hospitality. 20.11.15

Dr. H.C. Mult Robert Huber FMRS Noble Laureate

Message MessaGe

Date : 21.11.2015

I am happy to note that our Centre for Nano Science and Technology (CNST) of K. S. Rangasamy College of Technology (KSRCT) is organising an International Conference on Nanomaterials and Nanotechnology (NANO-15) with a special topic on Research to Innovations to Technology transfer during December 07-10, 2015 at our campus. The CNST established with good infrastructure facilities to meet the Scientists and Academicians to an advanced level in the field of nanotechnology. It also focuses in organising such International conferences and workshops to recognize the research outcomes of the young researchers. NANO-15 is organized in KSRCT with plenary lectures by Noble laureates and distinguished scientists, Key note address, invited talks and more than 550 contributed papers. The plenary talk by Nobel Laureates and invited talks from reputed organizations of India and abroad would bring out the current status in material science and technology. I ensure that the participants will have effective deliberations through this conference. I thank Dr. K. Thyagarajah, Principal, KSRCT and Dr V. Rajendran, Director R&D, Organising Chair and his team to organise this event as a successful. The kind support from the various government and private organisations/agencies for the successful conduct of the conference is highly acknowledged. I extend my warm greetings to all the participants and best wishes for the success of the Conference.

Dr. K. S. Rangasamy MJF

Sponsors Science and Engineering Research Board, Department of Science and Technology, New Delhi

Defence Research and Development Organisation, New Delhi

Board of Research in Nuclear Sciences, Mumbai

Indian Council for Medical Research, New Delhi

Tamilnadu State Council for Science and Technology, Chennai

Indian Society for Technical Education, New Delhi

Axis Bank Limited, India

Co-Sponsors National Institute for Nanotechnology (NINT) Innovation Centre, Alberta, Canada NanoCanada, Canada

Silver Sponsor Shimadzu India Pvt. Ltd, Chennai

x Sponsors

The Professor Venkatachalam Rajendran Research Foundation

Exhibitors

CSIR - Central Glass and Ceramics Research Institute, Kolkata

Tekna Plasma India, Chennai, India Lark Innovative Fine Teknowledge, Chennai

Industrial Partners Exigo Knowledge Ventures Private Limited, Bangaluru

Global Connect Inc., Saskatoon, Canada

Higginbothams Private Limited, Chennai, Tamil Nadu

Samraj Constructions, Tamil Nadu

Talent2Success Learning Pvt. Ltd, India Zealtech Electromec India Private Limited, Tamil Nadu

Sponsors xi

Publication Partners Bloomsbury Publishing India Pvt. Ltd, New Delhi The Higher Education Review, Bangalore

Journal Partners Polymer International

Nano System : Physics, Chemistry, Mathematics

Synthesis and Reactivity in Inorganic, Metal Organic and Nano-Metal Chemistry IET Nanobiotechnology

Media Partner The Hindu

Hospitality Partner Radisson 5 Star Hotel, Salem

xiv International Organising Committee

Editors’ Profile Dr. V. Rajendran FUSI, FASI, FInstP, is Director, Research & Development, K S R Group of Institutions and Centre for Nano Science and Technology, K.S Rangasamy College of Technology, Tamil Nadu, India. Under his able guidance, 20 scholars have completed and 09 scholars are pursuing their Ph.D. degrees. He has published more than 200 research papers in reputed international and national journals, 60 papers in conference proceedings, 32 refereed books, 4 R&D books and 11 patents. He has won many awards including the UNESCO visiting Scientist Fellowship, South Africa (2016), Fulbright Fellowship (2015), USA, PSN National Award for Excellence in Science (2013), Prof. K. Arumugam National Award in 2011, Best faculty award in 2010, Raman-Chandra Sekhar silver medal (2010), Tamil Nadu Scientist Award, NDT Man of Year 2004, Indo-Australia Senior Scientist Science and Technology visiting fellowship (2013), DAAD from Germany (2002), INSA, TNSCST Young Scientist, DAE/ BRNS Visiting Scientist, Best paper award from MRSI, ASI, ASA and USI and Outstanding Organiser Award for the 7th National Symposium on Ultrasonics, 1996. Dr. P. Manivasakan is an Associate Professor, Centre for Nano Science and Technology (CNST), K.S. Rangasamy College of Technology. He obtained his Master of Philosophy Degree in Chemistry (2007) from Madurai Kamaraj University, Madurai. He has received his Ph.D. Degree in Chemistry (2012) from Anna University, under the guidance of Prof. Dr. V. Rajendran and he has completed his postdoctoral studies in the field of nanostructured electro catalysis for catalyzing renewal energy, under the supervision of Prof. Dr. Jinkwon Kim, Nano Molecular Materials Laboratory, Kongju National University, South Korea. He has carried out extensive research work in the field of solid state chemistry of nanomaterials and molecular level electro catalysis. He has published 40 research papers in the peer reviewed international journals and eight papers in international conference proceedings and presented his research work in five international conferences. Dr. K.E. Geckeler is affiliated with the Gwangju Institute of Science and Technology (GIST), South Korea. and is a Professor at the School of Materials Science and Engineering. He has been the Founding Chair of the Department of Nanobio Materials and Electronics, World Class University (WCU), Gwangju, South Korea. In addition, he serves as Vice Director of the Gruenberg Center for Magnetic Nanomaterials (GCMN). He received his Ph.D. and M.D. degrees from the University of Tuebingen, Germany (both degrees: “magna cum laude”) and spent sabbatical leaves at Harvard University, University of Montana, Clemson University (USA), and at the University of Montpellier (France). He received a series of prestigious awards including the “Fonds of the Chemical Industry”, the “Fritz-Ter-Meer Award”, and the “Science Prize of the President of Korea”. The biannual international IUPAC symposium series on “Macro- and Supra¬molecular Architectures and Materials (MAM)” has been initiated and coorganized by him. Prof. Geckeler is Editor-in-Chief of the journal “Polymer International”, published by John Wiley & Sons, and is also on editorial boards of a series of other international journals. He has published more than 350 research articles and short communications, 12 book chapters, 15 books, and over 130 patents. His recent books cover different aspects of nanomaterials including the two standard references: “Advanced Nanomaterials” and “Functional Nanomaterials” published by Wiley.

Preface The International Conference on Nanomaterials and Nanotechnology (NANO-15) with a special topic on Innovations to Technology transfer during December 07-10, 2015 is organised by Centre for Nano Science and Technology (CNST) of K. S. Rangasamy College of Technology. CNST is a well established center equipped with world class infra structure facilities to carry out innovative researches in thrust areas of nanotechnology. CNST offers undergraduate (B.Tech.), post-graduate (M.Tech.) and research (Ph.D.) programmes. More than 950 abstracts have been received from India and abroad. Out of which 600 full papers, 450 have been selected and peer reviewed by the expert committee for the publication in conference books. All the received papers are classified under six titles namely Synthesis and Fabrication of Nanomaterials, Advanced Nanomaterials: Synthesis and Applications, Nanoelectronics and Sensors, Applications of Nanostructured Materials for Energy and Environmental Technology, Bio-nanomaterials for Biomedical Technology and Industrial Applications of Nanostructured Materials. Out of total 450 full papers accepted for NANO-15, a total of 56 have been identified for the inclusion in the book entitled Application of Nanostructured Materials for Energy and Environmental Technology after peer review. This book has the collection of contributed papers containing an overview of energy and environmental applications of nanostructured materials with unique physical and chemical properties. All the contributed authors are extended by our sincere thanks for their timely submission and cooperation in carrying out suggestions by the referees. The most effort and care have been taken in getting the review of all the contributed papers. The various government funding agencies, private organizations and industries are thankful for their munificent support and sponsor for the successful conduct the conference. We owe our special thanks to members of technical committee for peer review of contributed papers. The various committee chairs and members are highly acknowledged for making this event a grant success. The support extended by Bloomsbury Publishing India Pvt. Ltd in bringing out this book on time is highly appreciated. V. Rajendran P. Manivasakan Kurt E. Geckeler

Contents Foreword v Message vii Sponsors ix International Organising Committee xiii Editors’ Profile xv Preface xvii

Plenary Speakers 1. Multi-Functional Nano-Structured Oxides M. Maaza

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Keynote Speakers 2. Nanomaterials for Energy Storage Pedro Gomez-Romero 3. Functional Polymers and Polymer-Clay Nanocomposite for Oxyanions Removal Bernabé L. Rivas, Mónica Pérez, Julio Sánchez and Bruno F. Urbano 4. Energy Harvesting Clear Glass for Sustainable Glass Greenhouses Kamal Alameh, Mikhail Vasiliev, Mohammad Nur-E-Alam and Victor Rosenberg

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Invited Speakers 5. Effects of Nanostructured Silicate Based Material on Enhancing the Specific Heat Capacity of Nitrate Salt for Solar Thermal Energy Storage Application Josu López-López,Mani Karthik, Abdessamad Faik and Bruno D’Aguanno 6. P-N-Junction-Based Organophotocatalysis Keiji Nagai and Toshiyuki Abe 7. Systematic Material Design and Development for Fuel Cells Takeo Yamaguchi 8. Functional Semiconducting Nanostructures Based on Oxides (TiO2, BiVO4, NiTiO3) for Photocatalysis and Photovoltaic Applications Abdel Hadi Kassiba 9. Carbon Nanostructures and Flexible Platforms for Energy Storage Manjusha Shelke 10. Droplet Based LOC Technology for Point of Care Diagnostics Karan V.I.S. Kaler

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Contributed Papers 11. Development of Copper Modified Titanium Dioxide for Photoreduction of CO2 25 Nikita Singhal, AsgarAli, L.N. Sivakumar Konathala, Sandeep Saran and Umesh Kumar

xx Contents 12. Photo-Responsive Applications of Coumarin Dye Sensitized RGO-TiO2 Nanocomposites Alaka Samal, B.K. Mishra, J. Das and Dipti P. Das 13. Synthesis, Characterization and Photocatalytic Activity of Undoped and Mg-Doped Ceria Nanoparticles V. Ramasamy, V. Mohana and G. Suresh 14. Synthesis, Spectral and Morphological Characterization, and Photocatalytic Property of Bismuth Tungstate Nanoflakes S. Muthamizh, K. Giribabu, R. Manigandan, S. Munusamy, S. Praveen Kumar, T. Danasekaran, A. Padamanaban, R. Suresh and V. Narayanan 15. Production of Y-Shaped Multi-Walled Carbon Nanotubes Using Trimetallic Catalyst Supported on Silica and Their Application of As (V) Removal S. Mageswari, T. Maiyalagan, K. Gopal and S. Karthikeyan 16. Angelica glauca Root Extract Mediated Synthesis of Silver Nanoparticles and Their Investigations for Biological and Electrical Applications Madhulika Bhagat, Shayana Rajput, Saleem Khan, Sahil Gupta and Sandeep Arya 17. Effect of Excess Selenium in Formation of Cu2Zn1.5Sn1.2 (S0.9 + Se0.1)4 Alloys for Solar Cell Applications Sripan Chinnaiyah, Annamraju Kasi Viswanath and R. Ganesan 18. Controlled Synthesis of Novel Urchin Like Morphology of 1-D α-MnO2: Evolution and Catalytic Activities Ayonbala Baral, Malay Kumar Ghosh and Dipti P. Das 19. Ni3S2-Swcnhs Nanocomposite as an Efficient Catalytic Counter Electrode for Dye Sensitized Solar Cell Application K. Susmitha and M. Raghavender 20. Bio Mediated Synthesis of Dy3+ Doped Y2O3 Nanophosphor: Structural and Luminescence Studies J.B. Prasanna Kumar, G. Ramgopal, K.S. Anantharaju, B. Daruka Prasad, S.C. Prashantha, H. Nagabhushana and C. Suresh 21. Synthesis and Characterization of CZTS Nanoparticles for Photovoltaic Applications Ajay Dumasiya and N.M. Shah 22. Preparation and Characterization of Porous Silicon Photoelectrode for Dye Sensitized Solar Cells K. Gangadevi, K. Ramachandran and R. Srinivasan 23. TiO2 Based Dye-Sensitized Solar Cell Using Natural Dyes J. Kalaivani, K. Renukadevi, K. Ramachandran and R. Srinivasan 24. Grating Influence Study of GaAs Solar Cell Structures S. Saravanan, R.S. Dubey and S. Kalainathan 25. Preparation of Hole Transporting Layer Material CuNiOnanocomposite for Organic Solar Cells Surekha Podili, D. Geetha and P.S. Ramesh 26. Electrochemical Evaluation of RuO2, MnO2, (Ru:Mn)O2 Composite Thin Film Electrodes P.S. Joshi, S.D. Gothe, S.G. Madale and D.S. Sutrave

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Contents xxi

27. Comparative Study of MnO2, Co3O4 and MnO2: Co3O4 Stacked Thin Film Electrodes for Super Capacitor S.S. Dattatraya, M.J. Sangeeta and S.G. Sagar 28. Effect of Calcium Oxide Nanoparticles on the Performance of Polyethersulfone Ultrafiltration Membranes K. Rambabu and S. Velu 29. Prediction on Flashover Voltage of Bamboo Leaf Ash Blended Ceramic Electrical Insulator M. Shanmugam, G. Sivakumar and S. Barathan 30. High Voltage Solid State Symmetric Supercapacitor Based on Graphene-Poyoxometalates Hybrid Electrode with Quinone Doped Hybrid Gel Elecetrolyte Bhawna Nagar, Deepak P. Dubal and Pedro Gomez-Romero 31. Facile Synthesis and Characterization of Nano Andmicro Structured Lead Telluride for Thermoelectric Applications B. Khasimsaheb, S. Neeleshwar and B.K. Panigrahi 32. Phytogenic Nanosilver Incorporated with Epoxy Coating on PVC Materials and Their Antibiofilm Properties N. Supraja, S. Adam, T.N.V.K.V. Prasad and E. David 33. Synthesis and Characterization of ZnO NRs and Different QDs for Solar Cells Fabrication M. Kamruzzaman, J. Schneider and J.A. Zapien 34. Preparation and Characterisation of Nickel Aluminate—A Solid Acid Catalyst N. Neelakandeswari, N. Rajasekaran, K. Uthayarani and M. Chitra 35. Comparison of Pure CdS and Mg Doped CdS Films with Chemical Bath Deposition for Solar Cell Applications S. Rajathi, K. Selvaraju and K. Kirubavathi 36. Electrochemical Synthesis of P-Type Copper Oxides C.V. Niveditha, M.J. Jabeen Fatima and S. Sindhu 37. Application of Gel Electrolyte in Dye Sensitized Solar Cells P. Nijisha, N.M. Bhabhina and S. Sindhu 38. Hydrothermal Synthesis of Nanosized (Fe, Co, Ni)-TiO2 for Solar Hydrogen Generation K.R. Anju and T. Radhika 39. Facile Preparation of 3D-Interconnected Porous Metal Oxide Aerogels for Super Capacitors and Fuel Cell Applications Santhana Sivabalan Jayaseelan, Kesavan Devarayan and Byoung-Suhk Kim 40. Synthesis and Studies of Carbazole Based (A-D-A) Polymers for Organic Solar Cell Applications Govindasamy Sathiyan, Ramasamy Ganesamoorthy, E.K.T. Sivakumar, Rangasamy Thangamuthu and Pachagoundar Sakthivel 41. Synthesis of 1,7-Disubstituted N,N’-Bis(hexyl)Perylene-3, 4:9, 10-Tetracarboxylic Acid Diimide (PDI) Small Molecule for Organic Solar Cell Application Ramasamy Ganesamoorthy, Govindasamy Sathiyan, E.K.T. Sivakumar, Rangasamy Thangamuthu and Pachagoundar Sakthivel

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xxii Contents 42. Investigation on Structural Properties of Gadolinium Doped Barium Cerate Electrolyte A. Senthil Kumar, R. Balaji, P. Agalya, S. Bhuvanasundari and R. Venkateswaran 43. Facile Synthesis of (CdZn)Se Nanocrystalline thin Films via Arrested Precipitation Technique (APT) for Photovoltaic Application Chaitali S. Bagade, Vishvnath B. Ghanwat, Kishorkumar V. Khot, Pallavi B. Patil, Rahul M. Mane and P.N. Bhosale 44. Synthesis of LEEH Capped CdTe Quantum Dots for Solar Cell Application Shilpa Patel, Bijendra Thakur and Sukanta K. Tripathy 45. Hydrothermally Prepared Porous Titanium Dioxide Nanorods/Nanoparticles and Their Influence in Dye Sensitized Solar Cells R. Govindaraj, M. Magesh, N. Santhosh, M. Senthil Pandian and P. Ramasamy 46. SERS Enhancement of Glucose Molecules on Layered Hybrid Ag/ZnO/Ag Nanostructure Anil Kumar Pal and D. Bharathi Mohan 47. Ag Nanoparticles Decorated on ZnO Nanrods Array Based SERS Substrate for Label Free Detection of DNA Anil Kumar Pal and D. Bharathi Mohan 48. Facile Synthesis of Nanostructured Lithium Titanate for Battery Applications M. Selvamurugan, R. Dhilip Kumar and S. Karuppuchamy 189 49. Zinc Oxide/Palladium Nanocomposites an Efficient Solar Active Photocatalyst for Environment Remediation Application Karuppannan Rokesh, Kulandaivel Jeganathan and Kandasamy Jothivenkatachalam 50. Development of Polymeric Film Dosimeter Using Gamma Radiation Priyanka Oberoi, Chandra B. Maurya and Prakash A. Mahanwar 51. Vanadium (Oxide, Nitride and Carbide) Nanostructures Based Counter Electrodes in Dye Sensitized Solar Cell (DSSC) Applications P. Vijayakumar, M. Senthil Pandian, S. Mukhopadhyay and P. Ramasamy 52. Fabrication and Characterization of DSSC Using Agaricus Bisporus with Citrus Limonum as a Natural Metal Free Sensitizer A. Arulraj, S. Veeramani , B. Subramanian, G. Senguttuvan and V. Sivakumar 53. Green Synthesis, Characterization of CUO Nano Particles Using Mimosa Pudica Leaf Extract as Fuel and Their Antibacterial Activity H.J. Amith Yadav, B. Eraiah, H. Nagabhushana, R.B. Basavaraj, K. Lingaraju, H. Rajanaika and B. Daruka Prasad 54. Chemosynthesis, Characterization and PEC Performance of CdZn(SSe)2 Thin Films by Arrested Precipitation Technique (APT) S.K. Jagadale, D.B. Shinde, R.M. Mane, K.V. Khot, V.B. Ghanwat, P.N. Bhosale and R.K. Mane 55. Synthesis of Reduced Graphene-TiO2 Photocatalyst for Hydrogen Evolution Neha Singh, Rahul Kumar, Ratan Kumar Dey and Gajendra Prasad Singh 56. Analysing the Electrical Properties of Electron Beam Evaporated CdSe Thin Films for PEC Solar Cells K.S. Rajni

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Contents xxiii

57. Scrutiny of Nano Technology Applications for Diesel Engine Performance Enhancement and Emission Control N. Tiruvenkadam, P.R. Thyla, M. Senthil Kumar, P.R. Senthil Murugan, D. Sridhar and T. Vijay Ananth 58. Integral Approach to Improve Hybrid Supercapacitors: From Hybrid Electrode Materials Based on Reduced Graphene Oxide-Polyoxometalates (rGO-POMs) to Hybrid Electrolytes Containing Quinones Deepak P. Dubal and Pedro Gomez-Romero 59. Chlamydomonas – A Green Micro Sized Nano Synthesizer: Phyco Solution to Nano Problems Vidhyasri Subramaniyam, Suresh Ramraj Subashchandrabose, Palanisami Thavamani, Mallavarapu Megharaj, Zuliang Chen and Ravi Naidu 60. Synthesis of Spray Deposited ZnO Nanoparticle Thin Film for the Application of Dye-Sensitized Solar Cell A. Amala Rani and Suhashini Ernest 61. Heavy Metal Analysis on Mamandur Lake Sediments, Tamilnadu, India M. Sundarrajan and V. Arulesan 62. Electro Chemical and Photo Catalytic Enactment of Recovered MnO2 from Consumed Dry Cell Batteries M. Mylarappa, V. Venkata Lakshmi, L.S. Nandeesh, K.R. Vishnu Mahesh, H.P. Nagaswarupa, K.N. Shravana Kumara, N. Raghavendra and D.M.K. Siddeswara 63. Optically Tuned Poly (3-Hexylthiophene-2, 5-DIYL)P3HT/PCBM (Modified Fullerene) Blend for Plastic Solar Cell Ishwar Naik, Rajashekhar Bhajantri, Lohit Naik, B.S. Patil, Pragasam, Sunil Rathod and Jagadeesh Naik 64. Graphene Based Surface Plasmon Resonance to Differentiate Metallic Nanoparticles from Their Solutions; Theoretical and Experimental Approach Nasih Hma Salah, David Jenkins, Richard Handy and Larissa Panina 65. Titanium Dioxide Supported Ruthenium Nanoparticles for Carbon Sequestration Reaction Praveenkumar Upadhyay and Vivek Srivastava 66. Water Suspended Graphene-Draped MnO2 for High Performance Supercapacitor P. Siva, M. Selvam, M. Vinoth, V. Rajendran and K. Saminathan Author Index

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PLENARY SPEAKERS

Multi-Functional Nano-Structured Oxides M. Maaza UNESCO UNISA Africa Chair in Nnaosciences and Nanotechnology, 1 Preler, Street, Pretoria 0001, Pertorin, South Africa NANO Sciences African NET Work, iThemba LABS-National Research, Foundation, POBox 722, Somerset West 7129, South Africa

ABSTRACT As well defined by Woodword et al and in an additional series of major literature library, binary or multi-component metal oxides play a significant role in several physics, materials science, electrical engineering and recently the trans-disciplinary sector of nanosciences and nanotechnology. The significance of metal oxides, especially, resides in their variety, their chemical stability, and their diverse chemicals as well as their physical properties. Metal oxides display properties ranging from piezoelectricity, multiferoicity to superconductivity, from negative thermal expansion to super-ionic conductivity. Metal oxides arte used as optical coatings among the large variety of applications. Vanadium dioxide [VO2]. the alpha phase of Chromium oxide 9a-Cr2O30, Zinc oxide 9ZnO0 and their oxides by green chemistry are attracting more interest in view of their multi-functionalities in their nano-scaled form. This contribution reports on novel linear and nonlinear properties of such nano-structured oxides by standard and green chemistry proceedings.

V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 3–3 (2015)

KEYNOTE SPEAKERS

Nanomaterials for Energy Storage Pedro Gomez-Romero Catalan Institute of Nanoscience and Nanotechnology, ICN2 (CSIC-ICN), Campus UAB, E-08193 Bellaterra, Barcelona, Spain E-mail: [email protected]

ABSTRACT If climate change concerns were not enough, the end of cheap oil [1] and the need for energy security are finally boosting a long overdue change towards a new and sustainable model of generation, management, storage and consumption of energy. Recent efforts to tap unconventional oil and gas will soon be perceived as attempts to scoop out the final remains of an obsolete model. Regardless of how long this final stage will hinder our transition, we will finally have to shift from a society of “energy gatherers” (collecting fossils for fuel) to one of “energy farmers”, storing energy in the form of energy vectors such as electricity, biofuels, hydrogen or other synthetic fuels. Energy storage has been essentially absent from the equation of the conventional energy model dominant in the 20th Century. The perception of counting with an uninterrupted supply of cheap energy led to the consequent renounce to storage. However, energy storage in all its modalities will play an increasingly important role as a key factor of a sustainable model in which energy generation is neither cheap nor uninterrupted. Yet, the storage of large amounts of energy is an unresolved challenge. We are presently unable to store any amount of energy coming close to a 10% of our daily consumption in a cost-effective way whether in the form of electrical, chemical or thermal energy. All three varieties will strongly benefit from nanomaterials developments, but we will center on the first one which has reached by now a greater maturity level. Indeed, ElectroChemical Energy Storage (ECES) has come a long way from the heavy and contaminating lead-acid battery (introduced by Planté in 1859) to the last generation of rechargeable Lithium-ion batteries, ruling now the Kingdom of consumer electronics, and the new generation of supercapacitors. But our problem is that these technologies have been focused on small power applications related to power supply for consumer electronics (see Figure 1). Yet, when it comes to high-power storage applications Pumped Hydro (and to a lesser extent compressed air) is presently the only technology with a capacity high enough to respond to our oversized collective needs of power. On the other hand, ECES will predictably be a key player within the framework of distributed energy generation and storage networks. But before letting utility companies know about the good news of consumers turning into producers-storers-consumers (and distrusting any support from policy makers), a few giant breakthroughs need to take place within the field of ECES itself. In short, ECES systems should be able to store more energy and do it at a much faster rate (i.e. higher power), all of it at a lower cost and topped with environmental friendliness. Batteries and supercapacitors as well as hybrid systems are quickly advancing in that direction [2]. From mechanical (yellow) or magnetic (grey) physical techniques to chemical (in purple), electrochemical (green) or electrophysical (cyan) methods. However, in the past only small power V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 7–9 (2015)

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applications such as power supply for consumer electronics have been widely implemented. When it comes to bulk energy storage only pumped hydroelectric is presently practical. Yet, in order to implement a sustainable energy model, novel smart grid and bulk energy storage technologies will have to be developed.

Fig. 1: The Collection of Energy Storage Technologies is Quite Large and Varied

Among ECES systems, batteries and supercapacitors are complementary concerning energy and power densities. Batteries are characterized by relatively high specific energy and low specific power whereas supercapacitors feature greater specific power but with low specific energy (Figure 2).

Fig. 2: Ragone Plot with Specific Energy and Power for Different Energy Storage Devices

Supercapacitors lay in middle grounds between batteries and conventional capacitors. Double layer electrochemical capacitors (EDLCs) take advantage of the electro-ionic charge storage induced

Nanomaterials for Energy Storage

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in the electrochemical double layer of high-surface area carbons, whereas electrochemical supercapacitors rely on electroactive phases which undergo faradaic redox processes limited to the electrode-electrolyte interface leading to a so called pseudocapacitance. All these different mechanisms for charge storage have been traditionally exploited separately. Yet, in the same way that a combination of batteries and capacitors can power and reinforce each other in a circuit, different materials and charge storage mechanisms can be combined in a single device in order to improve overall performance. Hybrid nanocomposite materials, made of dissimilar but complementary components are the natural target for this purpose. Generally speaking, hybrid materials offer opportunities for synergic behavior and improved properties with respect to their individual components. Among many possible combinations, those formed by electroactive and conducting components are of particular interest for energy storage applications.[3] As a matter of fact, hybrid composite electrodes integrating electroactive oxides (or phosphates) and conducting carbons have long been prepared and optimized for rechargeable lithium batteries. In this case, the hybrid approach is limited to the physical integration of an electroactive but poorly conducting phase and graphitic carbon materials providing inter-grain electronic conductivity. Needless to say that not any mixing approach is good enough to lead to an optimal configuration. The right proportions concerning relative concentration and particle sizes are keys to provide the required percolation paths. But in any event, each of the components of a hybrid composite electrode keeps its chemical nature, crystal structure and even its physical and electrochemical properties. In this conference we will present an overview of some of the energy storage technologies which could benefit from the development of nanomaterials with special emphasis on batteries and supercapacitors. From nanocarbons to nanofluids there is an unexpected variety of materials. We will discuss in some detail hybrid nanomaterials made of capacitive and faradaic components which could contribute to the advancement of power and energy densities, along the diagonal of the Ragone plot in Figure 2.

REFERENCES [1] Murray, J. and King, D., Climate policy: Oil's tipping point has passed. Nature, 2012, 481, 433–435. [2] Dubal, D.P., Ayyad, O., Ruiz, V. and Gomez-Romero, P., Hybrid energy storage: The merging of battery and supercapacitor chemistries. Chem. Soc. Rev. 2015, 44, 1777–1790. [3] Gomez-Romero, P., Ayyad, O., Suarez-Guevara, J. and Munoz-Rojas, D., Hybrid materials: From Child’s play to energy storage and conversión. J. Sol. State Electrochem., 2010, 14, 1939–1945.

Functional Polymers and Polymer-Clay Nanocomposite for Oxyanions Removal Bernabé L. Rivas, Mónica Pérez, Julio Sánchez and Bruno F. Urbano Polymer Department, Faculty of Chemistry, University of Concepción, Chile E-mail: [email protected]

ABSTRACT Metal ions and oxyanions pollution in water concern to worldwide due the toxic effect on humans. They are introduced into the environment during industrial processes, refining of ores, mining, disposal of industrial and domestic waters, etc. Currently, there are available several technologies to remove metals from aqueous sources, such as; differential precipitation, solvent extraction, distillation, ion exchange, flotation, and filtration membranes, etc. Adsorption and ion exchange are the most developed due the easy operation, sledge-free, etc., being the polymer-based the widely studied and recently the polymer nanocomposites [1]. Polymer-clay nanocomposites researches have presented a great attention from scientific community because nanocomposites materials present enhanced properties (mechanical, thermal, and barrier properties) compared with starting material (unloaded polymers) [1, 2]. Diverse clays materials have been used as filler in nanocomposites; montmorillonite, kaolinite, vermiculite, among others. The use of polymer matrix with organic functional with capability to retain ion and filler such as clays lead to nanocomposite ion exchange resins. Recently, we have studied polymer nanocomposite loaded with layered double hydroxide (LDH) as sorbents for oxyanions from aqueous solution such as arsenate (AsO43-), chromate (CrO42-), and vanadate (VO43-). Under different experimental conditions, the composite exhibited a high sorption reaching almost a 100% of removal. Also, the sorption of oxyanions presented a fast kinetics reaching the maximum sorption after less than 30 min of contact. Selectivity experiments were carried out using an arsenic solution in the presence of sulfate anions and the nanocomposite did not exhibit significant decrease in sorption capacity. The authors thank to FONDECYT (Grant No 1150510) and REDOC (MINEDUC UCO1202).

REFERENCES [1] Zagorodni, A.A., Ion Exchange Materials Properties and Applications, 1st ed., Elsevier BV, Amsterdam, 2007. [2] Urbano, B.F., Rivas, B.L., Martinez, F. and Alexandratos, S.D., Reactive and Functional Polymers 2012, 72, 642–649.


Energy Harvesting Clear Glass for Sustainable Glass Greenhouses Kamal Alameh, Mikhail Vasiliev, Mohammad Nur-E-Alam and Victor Rosenberg1 Electron Science Research Institute, Edith Cowan University, 270 Joondalup Drive, Joondalup, WA, 6027, Australia 1 ClearVue Technologies, Ltd, Western Australia E-mail: [email protected]

ABSTRACT Photosynthesis is the key process governing crop growth and yield. Variations in both light intensity and its spectral components have a major influence on photosynthesis. However, high levels of solar energy illuminating crops typically lead to photosaturation and photoinhibition, which can harm the crops. Conventional shading from intense sun can protect the crop from heat damage; however, this typically reduces the crop yield, since it blocks both the visible (needed for photosynthesis) and invisible (heat generating) parts of the solar spectrum. We report the development of anovel “Intelligent Glass” technology that converts the Ultraviolet (UV) and Infrared (IR) components of sunlight into electricity whilst allowing visible light to pass through the glass. The glass panels comprise spectrally-selective optical structures and inorganic nano-particles incorporated into a polyvinyl butyral (PVB) interlayer that is fixed between two sheets of clear glass. Most of the visible light passes through the glass while more than 90% of the UV and a large part of IR radiation energy is scattered and routed to the edges of the glass where it is collected by Photo Voltaic (PV) cells to produce electricity. The glass panels have superior insulation properties compared to conventional glass, and can substantially reduce the heating, cooling and lighting costs in glass greenhouses. More than 50% savings in energy can be achieved using the novel “Intelligent Glass” technology.


INVITED SPEAKERS

Effects of Nanostructured Silicate Based Material on Enhancing the Specific Heat Capacity of Nitrate Salt for Solar Thermal Energy Storage Application Josu López-López,Mani Karthik, Abdessamad Faik and Bruno D’Aguanno CIC Energigune, Albert Einstein 48, 01510 Miñano (Álava), Spain E-mail: [email protected]

ABSTRACT The effects of nanostructured silicate based composite material on specific heat capacity (Cp) enhancement of nitrate salt were investigated in this study. Nanostructured Si-MCM-41 and Si-AlMCM-41 (Si/Al ratios 10, 25, 50) were synthesised by hydrothermal treatment method. The obtained nanostructured Si-MCM-41 or Si-Al-MCM-41 materials were dispersed in the aqueous solution of the salt followed by drying process to obtain the resultant salt based nano composite (molten salt/nanostructured silicate based material mixture).The surface morphology and dispersion of nanostructured materials on the salt surface were analysed by transmission and scanning electron microscopes.A modulated differential scanning calorimeter wasemployed to measure the Cp of salt nanocomposite in the both solid and liquid phases. The obtained results demonstrate that the addition of a small concentration (1.0 wt.%) of nanostructured material into the base salt increases the Cpin the both solid and liquid phases. For comparison, commercial silica or alumina nanoparticles were also chosen and their influence on the Cp of salt-based nano-composites was investigated and the obtained results are discussed. Keywords: Nano Materials, Specific Heat, Nanostructured Materials, Molten Salt, Thermal Energy Storage.


P-N-Junction-Based Organophotocatalysis Keiji Nagai and Toshiyuki Abe1 Chemical Resources Laboratory, Tokyo Institute of Technology, R1-26 Suzukake-dai, Yokohama, Japan 1 Hirosaki University, Aomori, Japan E-mail: [email protected]

ABSTRACT A full-spectrum visible-light-responsive organophotocatalyst membrane array is designed and employed for a one-pass-flow water purification system. Whereas previous photocatalyst systems required strong light source, the present design manages with natural sunlight intensity, owing to multi-layerization of a newly optimized low-absorbance organophotocatalyst. The design of the system is to utilize natural-sunlight equivalent visible light with 1 m2 of irradiation area to process 1 ton/day of water. A 1/3300 scale module of the system was constructed and experimentally demonstrated its viability. The reactor part of the flow system contains 24 stacked layers of organicsemiconductor-laminated Nafion film. The organic semiconductor is abilayer of metal-free phthalocyanine (H2Pc, p-type semiconductor) and 3, 4, 9, 10-perylenetertacarboxylicbisbenzimidazole (PTCBI, n-type semiconductor). Transparent Nafion functions as mechanical support and absorbent of trime thylamine, which was chosen as a typical contaminant of underground water in coastalareas. The reactor was irradiated for only 1 h/day by visible light (10 mW/cm2). The light intensity at the bottom layer was estimated to be 0.1 mW/cm2, which was sufficient intensity (Internal quantum efficiency was0.15.) for the photocatalytic reaction, due to the optimized absorbance and photocatalytic quantum efficiency of each layer. The inlet TMA concentration was 3 ppm, while that of the outlet was less than 0.03 ppm for the first day of the operation of the system with and without the bilayer. Without the bilayer, the TMA concentration of the outlet flow increased after the 20 days. With the bilayer, the TMA concentration of the outlet flow remained at less than 0.03 ppm for the 40day experimental period due to its photocatalysis. The turnover number of photocatalytic reaction was calculated to be 1.8 × 104.


Systematic Material Design and Development for Fuel Cells Takeo Yamaguchi Tokyo Institute of Technology, Chemical Resources Laboratory, Japan CREST, Japan Science and Technology Agency, Japan Kanagawa Academy of Science and Technology (KAST), Japan E-mail: [email protected]

ABSTRACT In the current state-of-the-art technology, the conversion efficiency of fossil fuels to work remains lower; while polymer-electrolyte fuel cells (PEFCs) represent a superior system that exhibits portability and high-efficiency, offering better power generation, meeting the desired levels of demand. However, in order to facilitate widespread use of fuel cells, cost and lifetime problems must be resolved. Solid alkaline fuel cells (SAFCs) are another system that holds the potential to achieve high-energy conversion efficiency without Pt catalysts. Although most of metal catalysts can be used under alkaline environment, development of durable electrolyte membranes in alkaline media is the key for this technology. We are systematically designing and developing new materials from the molecular level to the device level. In the fuel cell systems, different components such as membrane, catalysts, and catalyst layer share significant functions and work in a well-coordinated manner, and hence, the total cell system must be optimized for the best performance. Global warming issues and the systematic design and developing approaches concerning PEFCs and SAFCs will be discussed. Specifically, packed acid type electrolyte membranes, porous Pt alloy capsules for carbon free catalysts and durable anion-exchange membranes will be introduced.


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REFERENCES [1] Ogawa, T., Aonuma, T., Tamaki, T., Ohashi, H., Ushiyama, H., Yamashita, K. and Yamaguchi, T., Chem. Sci., 5(12), 4878-4887 (2014). [2] Ogawa, T., Kamiguchi, K., Tamaki, T., Imai, H. and Yamaguchi, T., Anal. Chem., 86(19), 9362-9366 (2014). [3] Hara, N., Ohashi, H., Ito, T. and Yamaguchi, T., J. Phys. Chem. B., 113(14), 4656-4663 (2009). [4] Jung, H.M., Fujii, K., Tamaki, T., Ohashi, H., Ito, T. and Yamaguchi, T., J. Memb. Sci., 373(1-2), 107-111 (2011). [5] Miyanishi, S., Fukushima, T. and Yamaguchi, T., Macromolecules, 48(8), 2576-2584 (2015) [6] Tamaki, T., Minagawa, A., Arumugam, B., Kakade, B.A. and Yamaguchi, T., J. Power Sources, 271, 346– 353 (2014). [7] Arumurgan, B., Kakade, B., Tamaki, T., Arao, M., Imai, H. and Yamaguchi, T., RSC Advances., 4(52), 27510-27517 (2014).

Functional Semiconducting Nanostructures Based on Oxides (TiO2, BiVO4, NiTiO3) for Photocatalysis and Photovoltaic Applications Abdel Hadi Kassiba Institute of Molecules and Materials of Le Mans (I3M) – UMR-CNRS 6283, Faculté des Sciences et Techniques – Université du Maine - 72085 Le Mans, France

ABSTRACT Applications of semiconducting oxides in new generations of solar cells or in photocatalytic processes for environment preservation are challenging tasks for wide material science community during the last two decades. As examples, photovoltaic (PV) efficiency of titanium dioxide based solar cells was intensively investigated as function of the morphology, structure, electronic and optical features. Exhaustive studies were dedicated also to the doping of titanium dioxide by suitable elements contributing to narrow the band gap leading then to the absorption of large rate of solar spectrum. In parallel to such development, the use of organic dyes to sensitize titanium dioxide is currently under consideration in the quest of highly efficient solar cells. However, not only the photovoltaic effect is matter of intensive investigations but the photocatalysis applications are also worthy of interest. Polluted waste water and hydrogen production for sustainable source of energy are some important problems to be faceted by suitable photocatalysts as titanium dioxide. In this context, bismuth vanadium oxides were also demonstrated as promising photocatalytic material due to their band gap ~2.5 eV. Nanostructures with high specific surfaces or textured thin films with rough morphologies can contribute to enhance the PC activity. The talk will be devoted to outline selected insights on our work performed on titanium dioxide and bismuth vanadium oxides materials for PV [1,2] and PC [3,4] applications. Mesoporous structures, nanoparticles or textured thin films were designated with optimized physical features. New generation of solar cell was realized from TiO2 while visible light driven PC reactions were conducted on bismuth vanadium oxide through the degradation of organic dye molecules for environmental applications.

REFERENCES [1] [2] [3] [4]

Ruiz-Preciado, M., Morales-Acevedo, A., et al. RSC Adv., 5 ( 23), (2015), 17396. Bellam, J., Ruiz-Preciado, M., Edely, M., et al. RSC Adv., 5 (14), (2015), 10551. Makowska-Janusik, M., Gladii, O., Kassiba, A., et al., J. Phys. Chem. C 118 (12) (2014), 6009. Melhem, H., Pardis, S., Wang, J., Jin et al., Sol. En. Mat. SolCell., 117 (2013), 624.


Carbon Nanostructures and Flexible Platforms for Energy Storage Manjusha Shelke CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune

ABSTRACT Efficiency of nanotechnology based energy conversion and storage devices is primary concern for clean energy applications. Different forms of nanostructured carbon are identified as potential electrode materials for energy storage devices like supercapacitors or batteries. Supercapacitor devices are important because of their higher power density, longer cycle life than secondary batteries and their higher energy density compared to conventional dielectric capacitors. However, electrode materials play crucial role in performance of supercapacitor. Graphitic nanostructures like carbon nanotubes (CNTs), graphene, carbon nanofibers, carbon nanohorns (CNH), carbon nanoonions (CNOs) are being researched, either in an electric double layer capacitor as the carbon electrode or in pseudocapacitors that employ a composite of highly conducting carbon with a material such as metal oxides, polymers. This talk will focus on our research on synthesis of carbon nanostructures and composites as electrode materials for high performance electrochemical supercapacitor [1–3]. I will further talk about our work on fabrication of a solid state flexible supercapacitor [4].

REFERENCES [1] Azagan, V.K., Vaishmpayan, M.V. and Shelke, M.V., Journal of Materials Chemistry A, 2, 2152–2159 (2014). [2] Wanga, Qi, Plylahan, N., Shelke, M.V., Devarapalli, R.R., Li, M., Subramanian, P., Djenizian, T., Boukherroub, R. and Szunerits, S., Carbon, 68, 175–184 (2014). [3] Deshmukh, A.B. and Shelke, M.V., RSC Advances, 3, 21390–21393 (2013). [4] Unpublished results.


Droplet Based LOC Technology for Point of Care Diagnostics Karan V.I.S. Kaler Department of Electrical and Computer Engineering, Schulich School of Engineering, 2500 University Drive, N.W. University of Calgary, Calgary, Alberta, Canada (T2N1N4) E-mail: [email protected]

ABSTRACT Point of care testing and diagnostics is emerging as a critical requirement in the health care and life sciences sector. It has the potential to revolutionize the delivery of health by providing rapid and cost effective testing and diagnostics at the bed-side or remote location. To address this need, requires the development of portable, automated and low cost instrumentation capable of handling and processing raw clinical sample to facilitate the rapid and cost effective detection of specific biomarkers or agents in patient sample. My presentation will focus on the development and application of a droplet based microfluidic LOC device, in addressing the health care for the rapid and cost effective means of detecting and quantification of clinically relevant pathogens. To illustrate the capabilities of this droplet technology, we will demonstrate its utility and capabilities in the detection of one or more strains of influenza virus in clinical patient samples, using a spatially multiplexed sample handling scheme. Our findings suggest that droplet based LOC devices is capable of carrying out on a single substrate both sample preparation, involving extraction and purification of nucleic acids obtained from the viral particles as well as performing real-time quantitative PCR using sample and reagents volumes that are an order of magnitude smaller than used by conventional bench top nucleic acid extraction and PCR equipment without compromising either sensitivity or specificity of detection.


CONTRIBUTED PAPERS

Development of Copper Modified Titanium Dioxide for Photoreduction of CO2 Nikita Singhal1, AsgarAli2, L.N. Sivakumar Konathala2, Sandeep Saran2 and Umesh Kumar1,2 1

AcSIR – Academy of Scientific and Innovative Research, Dehradun Chemical Science Division, CSIR-Indian Institute of Petroleum, Dehradun E-mail: [email protected]

2

INTRODUCTION Fossil fuels are going to deplete in nearby future and energy demand is continuously increasing day by day, there is a huge interest in developing alternative sustainable renewable energy resources [1–3]. In this field, Photocatalytic reduction is a one of greener approach to mitigate CO2 as well as to harness solar energy [4–6]. First, in 1979 Inoue et al. reported photoreduction of CO2 in aqueous media to produce methanol, formic acid, and formaldehyde using different semiconductors [7]. Various semiconductors had been reported till date for CO2 reduction. Among them TiO2 has engrossed a great concern due to its stability, non-toxicity, availability and cost-effectiveness [8–10]. But TiO2 is a wide band gap semiconductor which can utilize only UV radiation. As well as massive recombination of generate excitons causes lower activity toward CO2 reduction [11]. Different strategies can be used to modify TiO2 to extent its band gap and suppress recombination process [12]. Metal impregnation is one of technique to modify TiO2 for delayed recombination which further enhances the catalytic activity. Copper is a low cost material which has tremendous electron trap/transfer capacity and also enhance the basic sites on catalyst to attract protons to get better photocatalytic performance. Liu et al. [13] reported copper-loaded titaniaphotocatalyst and observed 10-fold rate-enhancements in CO2 reduction to CO. Slamet et al. [14] synthesized copper TiO2 in different oxidation state of copper and tested CO2 reduction to methanol under UV irradiation. Here, we developed Cu/TiO2 using copper metal over TiO2 to trap electron and suppress recombination process. The developed catalyst were well characterized and evaluated for CO2 reduction under UV radiation. CO was found to be as major product. EXPERIMENTAL Copper nanoparticles were prepared by chemical reduction route. 0.2 M aqueous CuCl2 was reduced by 0.5 M ascorbic acid at 80°C for 24 h followed by centrifugation at 4000 rpm and supernatant was used further. Here the color of copper chloride was changed from green to dark brown [15]. Cu/TiO2: Freshly prepared copper nanoparticles were impregnated over commercial TiO2 according to required loading. Obtained material was dried in air oven at 80°C. Finally one part was calcined under air at 600°C for 4 h to get Oxi-Cu TiO2 and second part was reduced under 20% H2at 350°C for 2 h to obtain Red-Cu TiO2. Photocatalytic reaction: Photocatalytic reduction of CO2 was carried out under UV irradiation in a continuous gas reactor. Reactor was illuminated by high pressure mercury lamp with the radiation V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 25–28 (2015)

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A Application of Nanostructured N M Materials for Eneergy and Enviroonmental Technoology

peak centered c at 254 nm. The reaactor was tighttly closed during reaction with w one inlet and a outlet. CO O2 was passed p through h water bubbleer to reactor for f UV illuminnation and ouutlet was connnected to onlinne GC equipped with TCD and FIID. The catallytic activity of different catalysts c weree compared by b C in a period of 3 h. Blannk experimennts were carrieed outin absennce of light, in i formaation rate of CO absencce of catalystt, and in absence of CO2 to ensure thee product forrmation is onnly due to CO O2 photorreduction.

RESU ULT AND DIISCUSSION N Coppeer nanoparticlles were sepaarately preparred and impreegnate over commercial c TiiO2 to develoop Cu/TiO2. XRD wass recorded to analyze the crystalline c natuure and phasee content of material. m Figurre 1a) shhows commerccial TiO2 was purely in anaatase form andd copper impreegnation does not alter phasse contennt of TiO2 (JC CPDS Card Noo. 21–1272). Figure F 1b) shoows UV-vis abbsorption specctra of TiO2 annd Cu/TiO2 were recorrded in range of 200–800 nm. n The absorrption spectra of all sampless exhibit stronng 4 nm. Oxi-C Cu/TiO2 show ws a slight hum mp around 6000–800 nm duue to Cu+2 [166]. absorpption below 400 Red-C Cu/TiO2 exten nts its band gaap to visible region. r SEM images ofTiO O2, 2% Oxi-Cuu/TiO2 and 2% % Red-C Cu/TiO2are shown in Figuree 2(1) a-c. A little agglomeeration is also observed mayy be due to thhe calcinnation process.. Presence of Copper C in devveloped catalyysts was confirrmed by EDX X equipped witth SEM, Figure 2(1) d. d TEM imag ges of copperr nano particcles and 2% % Red-Cu/TiO O2 are show wn

in Figgure 3. The synthesizedd Copper nanno particles are sphericaal in shape and a their sizze lies inn the range of 2.5–10 nm m Figure 3aa, but mostlyy ca. 5 nm. TEM T resultss in Figure 3b 3 show w that the pho otocatalyst TiO T 2 has the particle sizee of 40–200 nm. n

Fig. 1: a) XR RD Pattern b) UV-Visible U Speectra of TiO2, 2% % Oxi-Cu/TiO2 and 2% Red-C Cu/TiO2

Fiig. 2: (1) SEM Images of a) TiiO2 b) 2%Oxi-C Cu/TiO2 c) 2%R Red-Cu/TiO2 d)) EDX of 2%Reed-Cu/TiO2 (2) CO Productionn from CO2 Redduction under UV U Irradiation ovver Cu/TiO2

Deveelopment of Copp pper Modified Titanium Dioxide for f Photoreducttion of CO2

2 27

Fig. 3: TEM Im mages of a) Coppper Nano Partiicles b) 2% Redd-Cu/TiO2

Catallytic Evaluattion Synthhesized catalyssts were testedd for photocataalytic reductioon of CO2 in presenceof p watter vapor undeer UV irrradiation at atmospheric pressure and room temperature. CO2 is i reduced too CO as majoor produuct.TiO2 and 1% 1 Oxi-Cu/T TiO2,2% Oxi-C Cu/TiO2, 1% Red-Cu/TiO2and 2% Redd-Cu/TiO2 werre testedd for CO2 redu uction in a coontinuous flow w reactor. Waater saturated CO2(10 ml/m min) was passeed over 250 2 mg catalyst spread in thhe reactor. Thee results presennted here Figuure 2 (2) show ws that 2% ReddCu/TiO2 exhibits hiighest catalytiic activity till 3 hr of irradiaation. It givess maximum yiield of CO 20.8 R g maximuum 15.9 ppm/gg CO. 1% Oxxi-Cu/TiO2, 2% % Oxi-Cu/TiO O2 ppm/gg. While 1% Red-Cu/TiO 2 gives gives maximum 3.0 03 and 5.53 pppm/g CO respeectively. CONCLUSION Coppeer impregnateed TiO2 photoocatalyst has successfully s b been preparedd by impregnaation of ex-sittu syntheesized Cu-NPss for the photoocatalytic reduuction of CO2. The 2% Cu-R Red/TiO2 has performed beest in term ms CO formaation rate. Thhe copper present at the suurface play a very importaant role for thhe retarddation of phottoinduced elecctron hole paair recombinaation. Our preesent work offfers promisinng aspectts of CO2 redu uction to CO. ACK KNOWLEDG GEMENTS We arre grateful to Director, IIP for his kind permission p to publish the reesults. N.S. thhanks CSIR foor researrch funding. Authors A are thaankful to ASD D-IIP for their analytical a support. REFE ERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9]

Roy, S.C., Varg R ghese, O.K., Paaulose, M. and Grimes, G C.A., ACS A Nano, 20100, 4, 1259. Gratzel, M., Ino org. Chem, 20005, 44, 6841. Guines, S., Neu ugebauer, H. annd Sariciftci, N.S S., Chem. Rev., 2007, 107, 13224. I Indrakanti, V.P P., Kubicki, J.D.., Schobert, H.H H., Energy Enviiron. Sci., 2009,, 2, 745. J Jiang, Z., Xiao,, T., Kuznetsov, V.L. and Edw wards, P.P., Phill Trans Royal Sooc. A, 2010, 368, 3343. N Navalon, S., Dh hakshinamoorthhy, A., Alvaro, M. and Garcia, H., ChemSusC Chem, 2013, 6, 562. 5 I Inoue, T., Fujisshima, A., Koniishi, S. and Honnda, K., Nature,, 1979, 277, 6377. L G., Hoivik Liu, k, N., Wang, K. and Jakobsen, H., Solar Energgy Mater. and Solar S Cells, 2012, 105, 53. J Jayalakshmi, V., V Mahalakshm my, R., Krishnam murthy, K.R. and a Viswanathaan, B., Ind. J. Chem., C 2012, 51, 1263. [10] Dhakshinamoo D rthy, A., Navaloon, S., Corma, A. A and Garcia, H., Energy Envviron. Sci., 20122, 5, 9217.

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[11] [12] [13] [14] [15] [16]

Izumi, Y., Coord. Chem. Rev., 2012, 257, 171. Kumar, S.G. and Devi, L.G., J. Phys. Chem. A, 2011, 115, 13211. Liu, L., Gao, F., Zhao, H. and Li, Y., Appl. Catal., B-Environ., 2013, 134–135, 349. Slamet, H.W., Nasution, E., Purnama, S., Kosela, J., Gunlazuardi, Catal. Commun., 2005, 6, 313. Xiong, J., Wang, Y., Xue, Q. and Wu, X., Green Chem., 2011, 13, 900. Colon, G., Maicu, M., Hidalgo, M.C. and Navio, J.A., Appl. Catal. B-Environ., 2006, 67, 41.

Photo-Responsive Applications of Coumarin Dye Sensitized RGO-TiO2 Nanocomposites Alaka Samal1,2, B.K. Mishra1,2, J. Das2 and Dipti P. Das1,2 1

Academy of Scintific and Innovative Research, New Delhi CSIR—Institute of Minerals and Materials Technology, Bhubaneswar, Odisha

2

INTODUCTION Since early 1970s, Honda and Fujishima reported the effective photocatalytic activity of TiO2. TiO2 has received widespread response as one of the promising semiconductor photocatalyst, because of its high chemical stability, low cost and non-toxicity [1]. But due to its wide band gap (3.2–3.4 eV), it is useful under only UV light only which is very much expensive and harmful and also insufficiently available in whole solar range. So, development of visible light active catalyst is the most limelight job in material science in order to exploit the plentily available solar light. Tremendous steps were taken to enhance the photocatalytic activity of TiO2 Ca. deposition of noble metal which acts as electron shrink to suppress the electron-hole recombination [2]. Recently, the π-conjugative systems like C60, polyaniline and graphene etc. have taken the lead all over the globe [3]. Owing to a very unique sp2 hybridisation, graphene exhibits very high thermal conductivity, excellent charge mobility and high specific surface area. So, graphene is the most studied material now-a-days towards its adsorptivity and catalytic activity [4,5]. Kamat et al. [6], Akhavan et al. [7] and Bell et al. [8] fabricated TiO2-graphene composites by carrying out UV assisted photocatalytic reduction of graphite oxide (GO) using TiO2 nanoparticles. Lambert et al. [9] studied the synthesis of TiO2-graphene composites by hydrolysis of TiF4 in the presence of an aqueous dispersion of GO. In this work, we have fruitfully synthesize reduced graphene oxide (RGO) based TiO2 composites via microwave-assisted route, varying the wt.% of RGO. The composites were tested for the reduction of Cr (VI) under visible light (VISL) irradiation and also compared with coumarin dye (C334) sensitised RGO-TiO2. EXPERIMENTAL Synthesis of RGO-TIO2 RGO-TiO2 nanocomposites were prepared by microwave assisted combustion method using titanyl nitrate and urea as oxidizer and fuel, respectively. Solution A contains tetra-n-butyl titanate in 18 ml isopropyl alcohol which should be kept in an ice bath. The Solution B contains the different wt.% of GO dispersed in a mixture of deionized water and isopropanol which was sonicated for 30 mins. The Solution B is added to Solution A under stirring slowly in ice bath. After 1 h stirring, 37% nitric acid and Urea was added. The precursor solution was heated on a hot plate at 100oC to remove the solvent until the gel like precursor was obtained. The precursor was introduced into a domestic microwave oven (720 W) and irradiated for 20 mins. The samples were calcined at 300oC for 2 h in a half closed alumina crucible. The pristine titania can be prepared in the similar method without GO. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 29–32 (2015)

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All the synthesised samples were well characterised by PXRD, Raman, TEM, PL, DRUV-Vis, C NMR etc.

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Photocatalytic Activity Evaluation The photocatalytic performance of RGO-TiO2 were evaluated towards the photoreduction of Cr (VI) under visible light irradiation. The activated photocatalysts of 0.02 g were added to 10 mL of 20 ppm of Cr (VI) solution and a certain concentration of coumarin dye (C334) was also added into the mixture. Thereafter, it was exposed to VISL irradiation in an irradiation chamber (BS-02, Germany) for 3 h. Thereafter, the suspension was centrifuged to remove the photocatalyst from it. Then the supernatant Cr (VI) content was analysed using Cary 100 (Agilent) UV-Vis spectrophotometer. The experiments were also carried out without the addition of C334 to compare the activity. RESULTS AND DISCUSSION XRD Patterns of xRGO-TiO2 The XRD pattern of the composites is represented in Figure 1(a). The anatase phase of titania was marked asterisks. The XRD analysis further displays that the main diffraction peaks of RGO–TiO2 composites are similar to those of pure TiO2, which demonstrates that the presence of RGO does not result in the development of new crystal orientations of TiO2, which may be due to the low amount and relatively low diffraction intensity of RGO. Raman spectra (Figure 1(b)) confirm the formation of RGO-TiO2 composites. The spectra showed a strong interaction between TiO2 and RGO forming the nanocomposites. This shows a shifting the spectra of titania after doping with RGO. Surprisingly, the rutile titania which is present in the pristine titania is getting converted into anatase after RGO doping. Intensity ratio of D- to G- band is 0.89 (Figure 1(b)).

(a)

(b)

Fig. 1: (a) PXRD (b) Raman Shift of xRGO-TiO2

The TEM micrograph (Figure 2), shows the morphology of TiO2 and xRGO-TiO2. The formation of anatase TiO2 nanoparticles which are distributed evenly onto the surface of RGO sheets can be observed from figures. The large crystallite is identified as TiO2 nanoparticles. The interplannar

Photo-Responsive Applications of Coumarin Dye Sensitized RGO-TiO2 Nanocomposites

31

distance was observed to be 0.34 nm, which correspond to the [101] plane of anatase TiO2 (JCPDS#21–1272). Also, it’s evidenced from TEM micrographs that with increase in the RGO loading, there is a decrease in the particle size from 10-4 nm.

(a)

(b)

(c)

Fig. 2: TEM Image of (a) TiO2 (c) 2RGO-TiO2 (f) HRTEM of 4RGO-TiO2

Catalytic Activity of Dye Sensitised RGO-TiO2 The photocatalytic activity of the nanocomposites was studied towards the photoreduction of Cr (VI) in presence of VISL. The results in the Table 1 illustrate that the coumarin dye (C334) used as sensitizer which absorbs the visible light and improves the catalytic activity of the semiconductor by pushing electron to its conduction band (Scheme 1). Table 1: Catalytic Activity of Dye Sensitized RGO-TiO2

Catalyst (20 mg)

[C334] (mmol)

VISL (h)

2RGO-TiO2

0

4

2RGO-TiO2/C334

0.025

3

2RGO-TiO2/C334

0.0124

3

Photo-Reduction Cr (VI) (%) 100% 93.6% 100%

Scheme 1: Plausible Mechanism for Cr (VI) Photoreduction over C334 Sensitised RGO-TiO2

32


Remarkably complete photoreduction of Cr (VI) was achieved by the dye sensitized photocatalysts with C334 concentration of 0.0124 mmol in 3 h as compared to the catalyst without sensitizer which shows in 4 h. Though, the photoreduction of Cr (VI) is strongly pH dependent, the present photocatalyst is effective for photoreduction of Cr (VI) without any pH adjustment.

CONCLUSIONS RGO–TiO2 composites are successfully synthesized via microwave-assisted reduction of GO in the TiO2 suspension using a microwave system and their photocatalytic performances were investigated. The experimental results indicate that C334-dye sensitized RGO-TiO2 composites exhibit a better photocatalytic performance than pure TiO2 and RGO-TiO2 towards photo-reduction of Cr (VI) under VISL illumination. REFERENCES [1] [2] [3] [4] [5] [6] [7] [8]

Fujishima, A. and Honda, K., Nature 1972, 238, 37–38. Jing, D., Zhang, Y. and Guo, L., Chem. Phys. Lett. 2005, 415, 74–78. Xu, Y.-S. and Zhang, W.-D. Dalton Trans. 2013, 42, 1094–1101. Xu, J., Chen, M. and Wang, Z. Dalton Trans. 2014, 43, 3537–3544. Han, L., Wang, P. and Dong, S.J. Nanoscale 2012, 4, 5814–5825. Kamat, P.V. J. Phys. Chem. Lett. 2010, 1, 520–527. Akhavan, O. and Ghaderi, E. J. Phys. Chem. C 2009, 113, 20214–20220. Bell, N.J., Ng, Y.H., Du, A., Coster, H., Smith, S.C. and Amal, R. J. Phys. Chem. C 2011, 115, 6004–6009. [9] Lambert, T.N., Chavez, C.A., Hernandez-Sanchez, B., Lu, P., Bell, N.S., Ambrosini, A., Friedman, T., Boyle, T.J., Wheeler, D.R. and Huber, D.L. J. Phys. Chem. C 2009, 113, 19812–19823.

Synthesis, Characterization and Photocatalytic Activity of Undoped and Mg-Doped Ceria Nanoparticles V. Ramasamy, V. Mohana and G. Suresh Department of Physics, Annamalai University, Annamalai Nagar, Chidambaram E-mail: [email protected]

ABSTRACT The undoped and Mg doped CeO2 nanoparticles were synthesized by sol-gel technique. The prepared nanoparticles were characterized using X-ray diffraction pattern(XRD), UV-Vis and PL spectroscopy (UV-Visible and Photoluminescence), Fourier transform infrared spectroscopy (FTIR). The XRD results revealed that the nanoparticles are free fromsecondary phases and the nanocrystallites are in the cubic structure of size about 30 nm. The functional groups of the nanoparticles were analyzed through FTIR spectra. The photocatalytic activity of the synthesized nanoparticles was evaluated based on the photodegradation of methylene blue (MB) in crude UVlight. Keywords: CeO2, Sol-Gel, XRD, UV-Visible, PL and FTIR.

INTRODUCTION As one of the most important rare earth oxides,CeO2 has such in trisect chemical properties as high oxygen storage capacity and high oxygen mobility, which originate from variable valence state (+3 and +4) of cerium element. Many other rare earth or transition metal oxides are introduced to improve the physical and chemical properties of CeO2 [1]. The cerium dioxide (CeO2) has been attracting great interest in the recent years[2].Theundoped and doped CeO2have been widely used for various applications like semiconductor materials in ultra violet absorbers, fuel cells, oxygen sensors, optical devices [3]. One important application of photocatalyst is excited;it produces photogenerated holes in the valence band and the photogenerated electrons in the conduction band.Recently, CeO2 is widely use as catalysts [4]. CeO2nanoparticles can be synthesized by different methods, such as hydrothermal, reverse micellar, electrochemical synthesis, precipitation, and sol-gel technique [5]. The sol-gel technique exploits the advantages of cheaper precursors, a simple preparation method, and a resulting ultrafine, homogenous high active powder[6]. The aim of this work is to prepare undoped and Mg doped CeO2 nanoparticles by sol-gel method. The prepared nanoparticles were characterized and their photocatalytic activity was studied for the photodegradation of methylene blue (MB). EXPERIMENTAL TECHNIQUES Methods (synthesis of Mg doped CeO2 nanoparticles) The undoped and Mg doped CeO2 nanparticles were synthesized in deionized water. In this experiment, 5.2g (0.3M) of Ammonium Cerium (IV) nitrate (NH4)2[Ce(NO3)6] in 25 ml of deionized V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 33–38 (2015)

34


water aqueous and Magnesium acetate Tetrahydrate (CH3COO)2Mg.4H2O) (5wt%) in 25 ml of deionized water were poured into the above solution, under constant stirring for 10 min.Two solutions were mixed together, and the saturated solution of citric acid was added drop wise in to the mixture. Then, NH3 was added to the precursor solution in order to maintain the pH of the solution to 10.3. After continuous stirring for 4 hours at 70°C, the clear sol was completely turned to a gel. Then, the gel was dried and grained into powder. Then the powder was annealed at 700°C for 2 hrs in furnace under an air atmosphere.

RESULT AND DISCUSSION X-ray Diffraction (structure properties) The X-ray diffraction pattens of undoped and Mg (5wt %) doped ceria nanoparticles are shown in Figure 1.The planes such as (111), (200), (220), (311) and (400) are clearly identified in both doped and undoped ceria nanoparticles. All diffraction peaks can be indexed according to a pure cubic phase ofceria [space group:Fm3m] using the standard JCPDS data [34–0394] [7]. The diffraction peaks of Mg doped ceria nanoparticles are slightly shifted from their original position. This is due to the indication of Mg doped in to ceria nanoparticles. The crystallite size of the nanoparticles is measured by Scherrer’s formulaD = 0.9λ/βcosθ [8].

Fig. 1: X-ray Diffraction Patterns of Undoped and Mg-Doped CeO2 Nanopaerticles

where, D is the crystallinesize, the wavelength of the X-ray, θ the diffraction angle and β is the halfwidth. The calculated value of the crystallite size of ceria is about 30 nm.

Optical Properties UV-Visible Spectroscopy UV-Vis absorption spectral study may be assisted in understanding electronic structure of the optical band gap of the material. Absorption in the near ultraviolet region arises from electronic transitions

Synthesis, Characterization and Photocatalytic Activity of Undoped and Mg-Doped Ceria Nanoparticles

35

associated within the sample. The optical absorption spectra of undoped and Mg doped CeO2nanoparticles were recorded and are shown in Figure 2.

Fig. 2: UV-Visible Absorption Spectrum of Pure and Mg Doped CeO2 Nanoparticles

The CeO2 shows a broad absorption band located at 266–269 nm in the UV range, originating from the charge transfer transition from O2– (2p) to Ce4+ (4f) orbital’s in CeO2. These spectral profiles indicate that the charge transfer transition of Ce4+ overlaps with the 4f1–5d1transition of Ce3+. The absorption peak of sol-gel derived CeO2 nanoparticles is significantly blue-shifted compared to the bulk CeO2, due to the decreasing in particle size [9]. The optical band gap ( ) can be calculated based on the optical absorption spectra by the followingEqu.1 ( hν) = K (hν– )(1) [10].Plotting ( hν) 2as a function of photon energy (hν) and extrapolating the linear portion of the curve gives the value of the direct band gap energy shows in Figure 3. The absorption coefficient α was calculated from the following Equ. 2 [11]. α=

.

… (2)

Fig. 3: Band Gap Grap of Undoped and Mg Doped CeO2 Nanoparticles

36


Where A is thee absorbance of W o a sample, is the densityy of CeO2 (7.28 g/cm–3), iss the pathlengtth of thee quartz cell (1 1cm), and C is i the concentrration of the ceria c suspensiions. The bandd gap values of o pure and a Mg (5wt %) % doped ceria nanoparticlees are 4.74 andd 4.71 respecttively. The redduction of bannd gap iss observed in Mg M doped ceriia nanoparticles (Figure 3). Moreover, thee band gap vaalue of pure annd Mg dooped ceria nan noparticles aree higher compared to that off reported valuue Eg (3.19ev))[10]. The sam me value has already obtained (S. Gnanam ett al.,) by Innfluence of various v surfacctants on size, ptical propertiies of CeO2 naanostructures via v facile hydrrothermal routte, which is duue morphhology, and op to the effect of quan ntum confinem ment.

Photooluminescencce Spectroscoopy (PL) The PL P emission sp pectra of pure and Mg doped CeO2 nanopparticles with excitation e wavvelength of 2666 and 2660 nm are sho own in the Figgure 4. PL em mission spectraa have been widely w used to investigate thhe efficieency of chargee carrier trappping and migraation and to unnderstand the fact of electroon-hole pairs in i semiconductors fro om Figure 4,,five emissionn peaks are observed forr pureand Mgg doped CeO O2 nanopparticles.

Fig. 4: PL P Emission Sppectra of Undopped and Mg (5w wt %) Doped CeeO2 Nanoparticcles

Itt exhibits stron ng and sharp blue emissionn peaks at 4500, 452 and 4667 nm and, wiith relative low w intensse peaks at 368 and 371 nm m. Which mayy be are attribuuted to the peersistence of electron-phono e on interacction between n Ce4f and O2p band, becauuse the oxygenn defect level is i located on thhe site betweeen Ce4f and a O2p band d[12].

Fouriier Transform m Infrared Sppectroscopy (FTIR) ( The FTIR F spectra of o pure and Mg M doped ceriaa nanoparticles were recordded in the rangge of 400–40000 cm–1are a shown in Figure F 5. For CeO C 2 nanopartticles, the appearance of absorption bandd at 3412cm–1 is – attribuuted to the O-H mode, where as the bandds at 2929cm–1 and 2858 cm m–1 are due to the C-H bandds of the organic comp pounds.

Synthesis, Characterization and Photocatalytic Activity of Undoped and Mg-Doped Ceria Nanoparticles

37

The band at 1627cm–1 corresponds to the bending of H-O-H which is partly overlapping the O-CO stretching band [13]. The bands at 1045cm–1 are due to ν (Ce-O-Ce) vibration [14]. The absorption band of 712cm–1 and 855 cm–1 are due to the stretching frequency of Ce-O [15].

Fig. 5: FTIR Spectroscopy of Undoped and Mg Doped CeO2 Nanoparticles

Photocatalytic Degradation and Decolourization of MB The photocatalytic activity of the synthesized catalysts cerium oxide nanoparticles and Mg doped CeO2 were studied by degrading methylene blue dye. In 100 mL of 5 ×10–3 M concentrated dye, 0.2 g of the catalyst was added, degradation was carried out as mentioned above, and the effect of time on the degradation of MB dye was examined under solar light irradiation in the reaction time ranging from 0 to 60 minutes. It can be seen from UV-visible spectra changes, the strong adsorption peak of MB solution at 636 nm steadily decreased and degraded with increasing the light irradiation time, and the initial blue colour of the solution gradually turned to light – colored.

Fig. 6: Photodegradation and Decolourization of MB over CeO2 and Mg/CeO2 at pH 7, MB Concentration; 0.005/l, Catalyst Content; 0.2 g/l

38


The comparative study of photocatalytic activity of CeO2 and Mg/CeO2 photocatalysts for photodegradation of MB was shown in Figure 6. Results show that as time increases the percentage degradation increases. It has been observed that the degradation and decolourization of the compound proceeds much more rapidly in the presence of Mg/CeO2 doped catalyst in solar light. The reason for better photoactivity could be attributed to the fact that the catalyst is composed of nano size and nanocrystalline form. The presence of dopant prevents the recombination of photogenerated electrons and holes leading to better photocatalytic activity [16].

CONCLUSION The undoped and Mg doped CeO2nanoparticles were successfully synthesized by sol-gel technique. The XRD patterns confirm that the obtained product is cubic phase CeO2 with crystallite size of 30nm. The UV-Vis absorption spectra are blue-shifted for undoped and doped CeO2 nanoparticles due to quantum confinementeffects. The strong and sharp blue emission peaks are observed from PL measurements due to the presence of oxygen defects in CeO2 lattice. The varies bond vibrationmodes are assigned with for both doped and undoped the help of ceria FTIR spectra. A better performance of photocatalytic activity was found to 60 min irradiation time for Mg doped CeO2 nanoparticles.Thusis concluded that the synthesized Mg/CeO2 is one of the best candidate for environmental applications as a photocatalyst. REFERENCES [1] Zhang, D., Qian, Y.i, Shi, Liyi, Mai, H., Gao, R., Zhang, J., Yu, W. and Cao, W., Catalysis communication 26 (2012), 164–168. [2] Elaziouti, A., Laouedj, N., Bekka, A. and Vannier, R.N., J. King Saud university-science, 27 (2015), 120–135. [3] Deus, R.C., Foschini, C.R., Spitova, B., Moura, F., Moura, E., Longo, E. and Simoes, A.Z., Ceramics International, 40 (2014), 1–9 [4] Mohamed, R.M. and Azam, E.S., Int. J Photoenergy, 9 (2012), 928760. [5] Soren, S., Bessoi, M. and Parhi, P., Ceramics International, 41 (2015), 8114–8118. [6] Gao, J., Qi, Y., Yang, W., Guo, X., Li, S. and Li, X., J Materials chemistry and physics, 82 (2003), 602– 607. [7] Deus, R.C., Foschini, C.R., Spitova, B., Moura, F., Longo, E. and Simoes, A.Z., J Ceramics International, 40 (2014), 1–9. [8] Cullity, B.D., Reading: Addition –Wesley pub., 1978. [9] Anis-ur-Rehman, M., Saleem, A.S. and Abdullah, A., J Alloys and Compounds, 579 (2013), 450–456. [10] Gnanam, S. and Rajendran, V., J Nanoparticles, 6 (2013), 839391. [11] Tao, Y., Wang, H., Xia, Y., Zhang, G., Wu, H. and Tao, G., J Materials Chemistry and Physics, 124 (2010), 541–549. [12] Suresh, R., Ponnuswamy, V. and Mariappan, R., J Ceramics International, 40 (2014), 13515–13527. [13] Phoka, S., Laokul, P., Swatsitang, E., Promarak, V., Seraphin, S. and Maensiri, S., J Materials chemistry and Physics, 115 (2009), 423–428. [14] Kargar, H., Ghasemi, F. and Darroudi, M., Bioorganicpolymer, Ceramics International, 41 (2015), 1589– 1594. [15] Wang, G., Mu, Q., Chen, T. and Wang, Y., J Alloys and Compounds, 493 (2010), 202–207. [16] Bahadar, S. Khan, Khan, M. and Alamry, K.A., Int. J Electrochem. Sci., 8 (2013), 7284–7297.

Synthesis, Spectral and Morphological Characterization, and Photocatalytic Property of Bismuth Tungstate Nanoflakes S. Muthamizh, K. Giribabu, R. Manigandan, S. Munusamy, S. Praveen Kumar, T. Danasekaran, A. Padamanaban, R. Suresh and V. Narayanan Department of Inorganic Chemistry, University of Madras, Guindy Campus, Chennai E-mail: [email protected]

INTRODUCTION During the past decades, in order to remove the organic pollutants semiconductor photocatalysts have been regarded as one of most efficient and economical alternatives for solving environmental pollution problems. The enhancement of higher efficient photocatalytic activity of photocatalysts is still important work because exploiting the new high-efficiency photocatalysts is very difficult. It is well known that there are close correlations between the physical/chemical properties of semiconductor photocatalysts and their morphology, size and structure. Therefore, the increasing interest concentrates on improving the photocatalytic activity by means of designing and preparing hierarchical photocatalytic materials with unique nano/micro-structure units. As a kind of promising photocatalytic material, Bi2W2O9 can be constructed in diverse hierarchical architectures to improve its photocatalytic activity owing to its superior intrinsic physical and chemical properties [1]. To date, many considerable efforts have focused on preparing Bi2W2O9 micro- and nano-crystals with various morphologies to enhance its photocatalytic activity, such as nanoparticles,[2] nanoplates,[3] microspheres,[4] clew-like,[5] porous thin films,[6] hollow spheres[7] and so on. In the present work we have synthesized Bi2W2O9 nanoflakes by simple precipitation method and utilized for the degradation of Rhodamine B dye. EXPERIMENTAL Reagent Bismuth nitrate and sodium tungstate were purchased from Qualigens and used as received. Other chemicals used were of analytical reagent grade. Double distilled water was used throughout the experiment. All chemicals were used without further purification. Synthesis of Bi2W2O9 Nanoflakes Bi2W2O9 was prepared by reacting 1 mmol of Bi(NO3)3·5H2O and 1 mmol of sodium tungstate in 25 mL of distilled water at room temperature. The solution was stirred separately for 15 min and source of bismuth were mixed with source of tungstate drop by drop and stirred for2 h atroom V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 39–42 (2015)

40


temperature. Then the solution was filtered, the resulting precipitate was washed with deionized water and ethanol for several times. The filtered product was annealed at 600°C for 2 h.

Instrumentation The structure of Bi2W2O9 was analyzed by a Rich Siefert 3000 diffractometer with Cu-Kα1 radiation (λ = 1.5418 Å). DRS UV–Vis absorption spectrum was recorded using Perkin–Elmer lambda 650 spectrophotometer. The morphology of synthesized Bi2W2O9 was analyzed by HITACHI SU6600 (SEM) Scanning Electron Microscopy. RESULT AND DISCUSSION Structural Characterization The XRD pattern of Bi2W2O9 (Figure 1) shows the diffraction peaks that are well matched with standard file card (JCPDS.00-033-0221). The synthesized Bi2W2O9 has orthorhombic geometry with space group of Pbn22 with the lattice parameter of a = 5.413 Å, b = 5.413 Å c = 23.69 Å. The sharp peaks show the high crystalline nature of the synthesized nano flakes without any impurity.

Fig. 1: XRD Pattern of Bi2W2O9 Nanoflakes

Optical and Morphological Analysis Synthesized Bi2W2O9was subjected to DRS-UV-Vis analysis to examine the optical property and to find out the band gap of the material. Observed spectrum is shown in Figure 2 and the inset shows the band gap plot of Bi2W2O9. An absorption shoulder peak appeared at 350 nm is due to excitation from O 2p to Wt2g in the (WO42–). The band gap value (Eg) of nanoflakes was determined by using Tauc’s plot. (hυα)1/n = A(hυ-Eg) where, h – Planck’s constant, υ – frequency of vibration, a – absorption coefficient, Eg – band gap, A – proportional constant. n = 2 (for direct band gap), or n = 1/2 (for indirect band gap). Bi2W2O9 show the band gap of 3.0 eV. Figure 2b shows the SEM image of Bi2W2O9 produced under above said experimental condition. Which clearly indicates the flake like morphology of the synthesized Bi2W2O.9 [8].

Synthesis, Speectral and Morphhological Charaacterization, andd Photocatalytic Property...

4 41

Fig. 2: (a) DRS-UV V-Vis Spectrum of Bi2W2O9 Naanoflakes and Innsert Shows thee Tauc’spolt of Bi2W2O9 (b) SEM Image off Bi2W2O9 Nanooflakes

Photoocatalytic Acctivity The photocatalytic p activity of thee fabricated puure Bi2W2O9 investigated i o the degradaation of organic on dyeRhhodamine Bun nder visible liight irradiationn was shown in Figure 3. 25 mg of phootocatalyst waas taken and transferreed into a beakeer which contaains 100 ml off 1 × 10–5 RhB B dye solution..

Fig. 3: UV-Viss Absorption Sppectra of Aqueoous RhB at (a) 0 min, (b) 10 miin, (c) 20 min, (d) ( 30 min, ((e) 40 min (f) 50 (g) 60 min Duuring Photodeggradation by Usiing Bi2W2O9 Naanoflakes as Phhotocatalyst

Prrior to light ex xposure, the mixture m of dye and photocataalyst was keptt under dark inn order to attaiin adsorpption – desorp ption equilibrrium between the photocattalyst and dyee. After 30 min m the reactioon mixtuure is exposed d to visible light l under constant c magnnetic stirring. The reactionn mixture waas colleccted every 10 min and subbjected to UV V-Vis analysiss. It can be seeen that the intensity i of thhe absorpption peaks deecreased as thhe reaction proogressed with Bi2W2O9 nannoflakes as thee catalyst undeer irradiaation. After 60 0 min of irraddiation, the intensity of the absorption a peaaks decreased to almost 10% %

42


of that of the initial RhB solution. This indicates that the Bi2W2O9nanoflakes exhibit good photocatalytic activity. [8]

SUMMARY AND CONCLUSION Bismuth tungstate nanoflakes were synthesized by simple precipitation method. The Bi2W2O9 nanoflakes were characterized by XRD, DRS-UV –Vis spectroscopy and the morphology of the Bi2W2O9 was confirmed by SEM. The synthesized nanoflakes were utilized for the degradation of organic dye Rhodamine B in visible light irradiation within 60 min which shows the good efficient of Bi2W2O9nanoflakes towards the degradation of the organic pollutant. ACKNOWLEDGMENTS We acknowledge the SEM and DRS-UV facility provided by the National Centre for Nanoscience and Nanotechnology, University of Madras and UGC-UPE Phase II for the funding. REFERENCES [1] [2] [3] [4] [5] [6]

Zhang, N., Ciriminna, R., Pagliaro, M. and Xu, Y.J., Chem. Soc. Rev., 2014, 43, 5276–5287 Jiang, L., Wang, L.Z. and Zhang, J.L., Chem. Commun., 2010, 46, 8067–8069. Zhang, C. and Zhu, Y.F., Chem. Mater., 2005, 17, 3537–3545. Li, Y.Y., Liu, J.P., Huang, X.T. and Li, G.Y., Cryst. Growth Des., 2007, 7, 1350–1355 Zhang, L.S., Wang, W.Z., Zhou, L. and Xu, H.L., Small, 2007, 3, 1618–1625. He, D.Q., Wang, L.L., Li, H.Y., Yan, T.Y., Wang, D.J. and Xie, T.F., Cryst Eng Comm, 2011, 13, 4053–4059. [7] Zhang, L.W., Wang, Y.J., Cheng, H.Y., Yao, W.Q. and Zhu, Y.F., Adv. Mater., 2009, 21, 1286–1290. [8] Zhang, L. and Zhu, Y., Catal. Sci. Technol., 2012, 2, 694–706.

Production of Y-Shaped Multi-Walled Carbon Nanotubes Using Trimetallic Catalyst Supported on Silica and Their Application of As (V) Removal S. Mageswari, T. Maiyalagan1, K. Gopal2 and S. Karthikeyan3 Department of Chemistry, Vivekanandha College of Engineering for Women, Tiruchengode, Tamil Nadu, India 1 Division of Chemical and Biomolecular Engineering, Nanyang Technological University, Singapore 2 Department of Chemistry, Erode Arts and Science College, Erode, Tamil Nadu, India 3 Department of Chemistry, Chikkanna Govt. Arts College, Tirupur, Tamil Nadu, India

ABSTRACT Multi-walled carbon nanotubes (MWNTs) have been synthesized by simple method of spray pyrolysis using Rosmarinusofficinalisoilon Fe/Co/Mo catalyst supported on silica under nitrogen atmosphere. Multi-walled carbon nanotubes were synthesized at different temperatures ranging from 550°C to 750°C. The as-grown MWNTs were characterized by scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), and Raman spectral studies. The possibility of use of as-grown MWNTs asan adsorbent for removal of As (V) an ion from drinking water was studied. Adsorption isotherm data were interpreted by the Langmuir and Freundlich equations. Kinetic data were studied using pseudo-first order and pseudo-second order equations in order to elucidate the reaction mechanism. Keywords: Adsorption, As (V) Ions, Catalyst, Multi-Walled Carbon Nanotubes, Spraypyrolysis.

INTRODUCTION Carbon nanotubes (CNTs) are a new form of carbon molecules with many outstanding properties [1]. These properties make them potentially useful in various applications, including in the areas of electronic, mechanical, composite, etc. [2]. Majority of the synthetic methods such as arch-discharge, laser ablation, chemical vapor deposition (CVD) and spray pyrolysis are directly or indirectly based on the petroleum products [3]. Considering the environmental effects and decreasing petroleum product sources, efforts are currently directed to away from them and switch over to reproducible natural carbon sources such as camphor [4], Turpentine oil [5], Eucalyptus oil [6], Coconut oil [7] and Pine oil [8]. Transition metals are typically used as catalyst owing to their catalytic decomposition of carbon source, ability to form carbides and possibility for carbon to diffuse through and over the metals extremely rapidly [9]. Arsenic in natural waters is a worldwide problem. Arsenic is listed as a carcinogenic contaminant also liable for different health effects like stillbirth and polygenic disorder. Among methods developed to remove the arsenic from contaminated water such as coagulation, flocculation, precipitation, ion exchange, membrane filtration, and adsorption is the most widely used V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 43–48 (2015)

44


because it is simple, cost-effective, and sludge free. In this article, we report the synthesis of MWNTs using Rosmarinusofficinalisoil being a natural source that is renewable and low-cost. The possibility of the use of MWNTs as an adsorbent for the removal As (V) ions and adsorption capacity of chosen adsorbents was studied.

EXPERIMENTAL TECHNIQUE Synthesis of Multi-Walled Carbon Nanotubes The synthesis was carried out using a set up similar to Afre et al. [10]. A desired amount of Fe/Co/Mo supported with silica catalyst on a quartz boat was placed in a quartz tube inside an electric furnace. Synthesis was conducted at 650°C in nitrogen atmosphere, with a typical reaction time of 60 min. Rosmarinusofficinalisoil were supplied at a rate of 0.1g/min. The grown carbon nanotubes were characterized by SEM, HRTEM and Raman spectroscopy. The stock solution of As (V) was prepared by dissolving Na2HAsO4.7H2O in distilled water. The residual As (V) concentration in the solution after adsorption was analyzed using a flame atomic adsorption spectrometer (AAS). The solution pH was adjusted with HCl and NaOH. Adsorption Process As (V) adsorption capacity of MWNTs was firm in a batch reactor. The As (V) solutions of required concentration were prepared by diluting appropriate volume of a stock solution. The solution was further diluted to the required concentrations (10–100 mg/L) before its use. The pH of the solutions was adjusted by adding 0.1 M HNO3 or 0.1 M NaOH. All the experiments were performed by agitating 50 mL of the As (V) solution at the desired concentration and 50 mg MWNTs in 100 mL bottles. Agitation was performed for a predetermined time at room temperature in a reciprocating shaker. The suspension was filtered through 0.45 µm filters and the residual As (V) concentration was determined in the liquid phase using atomic absorption spectrometer (AAS, Shimadzu, Japan model AA-6800). The percentage of adsorption was calculated using the relationship:

R% =

(C0 − C t ) ×100 C0

… (1)

where C0 and Ct are initial (inlet) and final concentrations of arsenic at time t. Then the amount of arsenic adsorption per unit mass of adsorbent at time t(qt) was calculated using the relationship:

qt =

C 0 −C t ×V W

… (2)

where V is the volume of solution (L) and W is the mass of the adsorbent (g).

RESULT AND DISCUSSION Scanning electron microscopy, high resolution transmission electron microscope and Raman spectroscopic techniques were used to characterize the carbon nanotube produced. Figures 1, 2 shows the SEM and TEM images of MWNTs synthesized. The results of Raman spectroscopy analysis (not

Production of Y-Shaped Multi-Walled Carbon Nanotubes Using Trimetallic Catalyst ...

45

shown) represent the MWNTs grown on the catalyst surface at 650°C, indicating two characteristic peaks at 1354 cm–1 and 1582 cm–1 which correspond to D and G bands, respectively.

Fig. 1: SEM Image of MWNTs

Fig. 2: HRTEM Image of MWNTs

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Adsorption Isotherm The experimental data for As (V) adsorption onto MWNTs could be evaluated by the Langmuir and Freundlich isotherm models.

Q 0b C e 1+ Q 0 C e

Q=

… (3)

Q = K F Cen

… (4)

Where Ce is the equilibrium concentration of as (V) (mg/L), Q0 (mgg–1) and b (Lmg–1) are Langmuir constants and KF (mg g–1) and n are Freundlich constants. The constants of Langmuir and Freundlich models are obtained from fitting the adsorption equilibrium data and are listed in Table1. Table 1: Langmuir and Freundlich Models for Adsorption of As (V) onto Purified Chosen MWNTs Langmuir Models

Freundlich Models

Adsorption Isotherm Models

Q0 (mgg )

b (L mg )

R

As (V)

32.64

0.26

0.995

–1

–1

2

KF (mg g–1)

n

R2

11.86

0.248

0.966

Kinetics of Adsorption Adsorption kinetics is used to investigate the mechanism and the rate controlling steps of adsorption. The kinetic information obtained is then applied to totally different models to explain the interaction between the As (V) and also the chosen adsorbents. The pseudo-first order and pseudo-second order were used to elucidate the complex dynamics of the adsorption process. To determine the equation that best describes the adsorption of As (V), a standard error of estimate was calculated for every kinetic equation, viz. pseudo first order and pseudo second order. A relatively high value of the regression coefficient (R2) was used as the criteria for the most effective work [11].

R = 2

2 ∑ q 2 - ∑ (q − q′ )

∑q

2

… (5)

Where q & q' are the measured and calculated amounts of As (V) adsorbed on a chosen adsorbent at time t.

Pseudo-First Order Kinetic Model The pseudo first order equation [12] is generally expressed as first order rate expression as shown below.

dq t dt

= k1(q e - q t )

… (6)

Where qe and qt are the adsorption capacity (mg g–1) at equilibrium and at time t respectively, k1 is the rate constant of pseudo-first order adsorption (min–1).

Production of Y-Shaped Multi-Walled Carbon Nanotubes Using Trimetallic Catalyst ...

47

Pseudo-Second Order Kinetic Model The pseudo-second order equation [13] has been considered for describing the adsorption of As (V) on chosen adsorbates. The linearized form of the pseudo-second order rate equation is given as,

t 1 t = + q t k q2 qe

… (7)

2 e

where k2 is the rate constant of pseudo second order adsorption (g mg–1 min–1), qe and q t are the values of the amount of As (V) adsorbed per unit mass of adsorbate at equilibrium and at any time t, respectively

Effect of Temperature on Kinetic Rate Constant and Rate Parameters Adsorption experiments were carried out with fixed initial As (V) concentration (50 mg/L) at pH 3 and at different temperatures, viz. 30°C, 45°C and 60°C. The analysis of the data collected in Table 2, reveals that the increases in temperature on As (V) removal have a significant effect on the pseudo first order rate constants. The results reveal also that the influence of temperature on pseudo second order rate constant is appreciable. The value of correlation coefficient R2 (0.992) for pseudo second order rate equation, shows that the adsorption of As (V) ions by MWNTs was better than first order equation. Table 2: The Adsorption Kinetic Model Rate Constants for Chosen MWNTs at Different Temperatures Adsorbent

MWNTs

Initial Temperature

Pseudo First Order –1

K1 (min )

R

2

Pseudo Second Order –1

K2 (g mg min)

h (mg g–1 min–1)

R2

35°C

0.136

0.916

0.124

21.614

0.987

45°C

0.138

0.918

0.016

14.213

0.996

60°C

0.167

0.922

0.128

11.226

0.985

CONCLUSION Multi-walled carbon nanotubes were obtained by chemical vapour deposition technique using Rosmarinusofficinalisoil, as an unconventional natural precursor. The experimental diameter of CNT was found to be about 20–30 nm and the achieved yield was 60 % at 650°C, confirming the possibility and reliability of obtaining MWNTs as a major adsorbent source to be applied in the process of eliminating As (V) from aqueous solution. The kinetic study also revealed that elimination of As (V) takes place through a film diffusion process at all the concentrations and temperatures of MWNTs obtained from Rosmarinusofficinalisoil. The saturation percentage was found to be 93% for the MWNTs and the As (V) adsorption on adsorbent was found to follow the pseudo second-order rate equations. REFERENCES [1] Forro, L. and Schonenbergerand C., Springer, 12, 329–384, 2001. [2] Baughman, R.H., Zakhidov, A.A. and de Heer, W.A., Science, 297, 787–792, 2002.

48 [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]


Jaybhaye, S., Maheshwar Sharon and Singh, L.N., Madurai Sharon, SRIMNC, 36, 37, 2006. Maheshwar Sharon, Mukhopadhyay, K. and Krishna, K. M., Phys. Rev. Lett., 72, 3182, 1994. Afre, R.A., Soga, T., Jimbo, T., Mukul, K., Ando, Y. and Sharon, Maheshwar, Chem. Phys. Lett., 3, 6, 2005. Ghose, P., Afre, R.A., Soga, T. and Jimbo, T., Mater. Lett., 61, 3786, 2007. Paul, S. and Samdarshi, S.K., New Carbon Mater., 26, 85, 2011. Karthikeyan, S. and Mahalingam, P., Inter. J. Nanotechnol. Appl., 4, 189, 2010. Fonesseca, A., Harnadi, A., Nagy, J.B., Bernaetrs, J. B. and Lucas, A. A., J. Mol. Cat. A. Chem., 7, 159–168, 1996. Rakesh, A., Afre, T., Soga, T., Jimbo, Mukul Kumar, Y., Ando, M., Sharon, Chem. Phys. Lett., 414, 6, 2005. Chien, S.H. and Clayton, W.R., Soil Sci. Soc. Am. J., 44, 265, 1980. Lagergren, S. and Kungliga Svenska Vetenskapsaka Demiens. Handlingar, 24, 130–139, 1898. Ho, Y.S., John-Wase, D.A. and Forster, C.F., Adsorption Sci. Technol., 18, 639, 2000.

Angelica glauca Root Extract Mediated Synthesis of Silver Nanoparticles and Their Investigations for Biological and Electrical Applications Madhulika Bhagat, Shayana Rajput, Saleem Khan1, Sahil Gupta and Sandeep Arya1 School of Biotechnology, University of Jammu, Jammu, J&K Department of Physics & Electronics, University of Jammu, Jammu, J&K E-mail: [email protected]; [email protected]

1

ABSTRACT In our work, silver (Ag) nanoparticles were synthesized bio-chemically at room temperature using aqueous extract from roots of Angelica glauca plant. The roots were collected, thoroughly washed, dried at room temperature and then grinded into powder. The powder was then utilized to synthesize its aqueous extract and silver nanoparticles using AgNO3. The as-synthesized silver nanoparticles were further studied for their morphological, biological and electrical characterization. The morphological studies, such as scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and UV-Vis spectrum confirmed their successful synthesis. Biological analysis revealed their antioxidant activity both by (2, 2-diphenyl-1-picrylhydrazyl) DPPH assay and lipid peroxidation inhibition assay (LPA). Electrical characterization has also been studied that showed interesting results. Keywords: Angelica glauca, Silver Nanoparticles, DPPH, Lipid Peroxidation Inhibition, Electrical Characterization.

INTRODUCTION Nanoscience and nanotechnology are one of the renowned areas of research that concern with the development of experimental processes including the synthesis of nanoparticles of different sizes, shapes and controlled dispersity [1]. They have their uses in optoelectronics, recording media, device based sensors, catalysis etc. However, in biological system, silver is gaining much more importance for synthesizing nanoparticles due to its least toxic effect on humans [2]. Synthesis of silver nanoparticles usually involves toxic chemicals that may get adsorbed on the surface causing adverse effects. This leads to develop environmental friendly techniques for their synthesis. In this regard, a green synthesis technique is reported for preparation of silver nanoparticles. Green synthesis of nanoparticles is based on utilization of micro-organisms, plant leaf extracts etc. that avoids use of harmful chemicals. This technique is desired due to its ecofriendly and cost-effective approach [3]. In our studies, we synthesised nanoparticles using biological approach. Silver nitrate (AgNO3) and aqueous extract of Angelica glauca are employed for synthesising nanoparticles. Plant extracts V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 49–54 (2015)

50


contain valuable compounds like saponins, terpenoids, proteins, polyphenols and flavonoids. These compounds have the properties of stabilizers/emulsifiers which help in the production of silver nanoparticles. The free radical scavenging potential of as synthesised silver nanoparticles are estimated by using DPPH assay and Lipid peroxidation inhibition assay. Further, morphological and electrical characterizations have also been done.

MATERIALS AND METHODS Collection and Preparation of Plant Material For experimental studies roots part of A. glauca plant were collected from high altitudes of Bhaderwah region of Jammu and Kashmir. The collected plant material was shade dried, grinded and crushed into powder. The powder thus obtained was dissolved in double distilled water to make aqueous extract. After 24 hours, the dissolved powder was filtered and dried at room temperature to make extract. Green Synthesis of Silver Nanoparticles In order to synthesize silver nanoparticles, plant roots were used. 5 gm of extract from root was dissolved in 50 ml double distilled water. AgNO3 was used which contains free ions and is present in oxidized form. The plant acts as reducing agent and thus reduces AgNO3 into metallic form. 20 ml of this extract was mixed with 80 ml of 5mM AgNO3 solution. The prepared solution was kept in dark for about 24 hours. The formation of reddish brown color was the evidence for the formation of nanoparticles. After 24 hours, the reaction mixture was centrifuged at 20,000 rpm for 20 minutes at 25°C temperature. The supernatant thus obtained was discarded and pellet was washed twice with double distilled water using centrifugation. The pellet obtained was collected using ethyl acetate [4]. Finally, the synthesized nanoparticles were dried at room temperature for further studies. Antioxidant Properties DPPH Radical Scavenging Assay DPPH assay was used to determine the radical scavenging activity of plant extracts and silver nanoparticles with slight modifications in the method discussed by N. Abe et al. [5]. 1 mL of 0.5 mM DPPH solution prepared in methanol was mixed with plant extract and silver nanoparticles to four different concentrations (50 µl, 100 µl, 150 µl and 200 µl). Then, 2.0 mL of 0.1 M sodium acetate buffer (pH5.5) was added. The final volume was made to 4 mL using methanol. The mixtures were kept in dark for 30 minutes at room temperature. Methanol was used as a negative control. 50% inhibition (IC50) of the samples was calculated from the graph by plotting %age inhibition against sample concentrations [6]. The radical scavenging activity (RSA) was calculated as a percentage of DPPH radical discoloration, using the equation: … (i) %RSA = [(A0–AS)/A0] × 100 where, A0 is the absorbance of the control and AS is the absorbance of the test compound. Lipid Peroxidation Inhibition Assay Thiobarbituric acid reactive substances (TBARSs) estimation is the most commonly used method to detect lipid peroxidation with slight modifications in the method [6]. Brain homogenate (100 µl) was mixed with different concentrations of extracts and its nanoparticles (5 mg/ml) and the volume of mixture was then raised to 1.0 ml using PBS. The reaction mixture was then incubated at 37ºC for 15

Angelica glauca Root Extract Mediated Synthesis of Silver Nanoparticles...

51

min. After incubation, 500 µl of Fenton reagent was subjected to the reaction mixtures. Followed by an incubation of 1 h at 37ºC, the equivalent volume of 10% trichloroacetic acid (TCA) and 0.7% thiobarbituric acid (prepared in 0.025 N NaOH) was added. The resultant mixture was incubated at 80ºC for 1 h in water bath. A pink-colored chromogen complex formed was read at 534 nm. The protection index of the extract and nanoparticles was compared based on percentage inhibition in the colour chromogen complex formation correspond to the reduction in absorbance at 534 nm [6].

RESULTS SEM Characterization The morphological properties of the as-synthesized Ag nanoparticles were studied using Zeiss EVO 40 Scanning Electron Microscope. After the preparation of the nanoparticles, the suspension of nanoparticles in double distilled water was used for SEM analysis by fabricating a drop of suspension onto a clean electric Stubs and allowing water to completely evaporate. The dried sample was then mounted on a clean aluminium stub. The sample was then viewed under scanning electron microscope at an accelerating voltage of 20 kV. Figure 1 shows the SEM micrograph of as-synthesized Ag nanoparticles. SEM studies confirmed the development of nanoparticles with almost same shapes and dimensions and have diameter 50 nm (approx).

Fig. 1: SEM of Silver Nanoparticles with X = 100K

EDX Characterization Elemental compositional analysis has also been done through EDX (Energy Dispersive X-ray study) to find out the purity of silver nanoparticles. The graphical results for EDX are shown in Figure 2. This is an automated generated graph by built-in software and shows the highest counts of silver.

52


The main and intense peak in the graph is for silver. Other elements observed in the obtained graph are carbon, oxygen, magnesium and chlorine. Silver and Oxygen, atomic number contrast of these two element is a plays a vital role in identifying the weight percentage.

Fig. 2: EDX Compositional Intensity of the As-Synthesized Silver Nanoparticles

Antioxidant Studies The free radical scavenging activity of samples performed by using DPPH assay was analyzed by calculating IC50 values as is summarized in Table 1. The silver nanoparticles were found more potent antioxidant with IC50 value of (123.62 µg/ml) whereas the plant extract has IC50 value of (655.59 µg/ml). AgNO3 itself has not radical scavenging activity. Table 2: Antioxidant Activity of A. glauca Extract and Its Nanoparticle Conc. (µg/ml)

DPPH Radical Scavenging Activity (%age)

Lipid Peroxidation Inhibition

Extract

Nanoparticles

AgNO3

Extract

50

13.05

26.37

–

19.91

50.87

–

100

15.18

37.51

–

28.04

64.73

–

150

19.21

62.22

–

40.18

70.32

–

200

23.96

75.83

–

46.65

83.51

–

655.59

123.62

NA

213.29

41.15

NA

IC50

Nanoparticles

AgNO3

So, the obtained results showed that the nanoparticles of an extract increase the radical scavenging activities by many folds. The IC50 values of extract and its silver nanoparticles is obtained to be 213.29 µg/ml and 41.15 µg/ml respectively. By comparing the IC50 values of both samples, it was calculated that silver nanoparticles showed higher ability to maintain membrane integrity by inhibiting the lipid peroxidation of the membranes.

Angelica glauca Root Extract Mediated Synthesis of Silver Nanoparticles...

53

VI Characteristics The schematic for experimental setup is shown in Figure 3. The current–voltage (I–V) characteristics shown in Figure 4 of the as-synthesized AgNPs dispersed over the solution of distilled water containing E. Coli are studied for its electrical characterization. The whole setup is made on a glass slide for electrical characterization.

Fig. 3: Experimental Set-Up for Evaluating Electrical Characterization

Fig. 4: VI Characteristics Showing Conductivity of Nanoparticles

The graph confirmed that with the increase in voltage, current increases in almost linear fashion but after sometime, when the experiment is repeated, and the value of current decreases a bit. This may be due to slower decay of E coli in distilled water. Hence, we can say that the decay rate of bacteria can be estimated by observing the VI characteristics shown in Figure 4.

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CONCLUSION Silver nanoparticles have been synthesized successfully by using aqueous extract of Angelica glauca plant. Investigations showed that plant extracted AgNPs showed a good antioxidant activity. The SEM analysis verified the successful synthesis of AgNPs with size less than 100 nm. EDX confirmed the elemental composition. Electrical characterization confirmed that the current increases faster with the increase in voltage with healthy bacteria as compared to the decayed one. Thus, it is possible to estimate the decay rate of bacteria by studying their electrical properties. REFERENCES [1] Khalil, M.H., Ismail, E.H., El-Baghdady, K.Z. and Mohamed, D., “Green synthesis of silver nanoparticles using olive leaf extract and its antibacterial activity,” Arabian Journal of Chemistry, Vol. 7, pp. 1131– 1139, 2013. [2] Bhagat, M., Rajput, S., Arya, S., Khan, S. and Lehana, P., “Biological and Electrical Properties of Biosynthesized Silver (Ag) Nanoparticles,” Bulletin of Material Science, Vol. 38, pp. 1253–1258, 2015. [3] Chen, D.H. and Hsieh, C.H., “Synthesis of nickel nanoparticles in aqueous cationic surfactant solutions,” Journal of materials chemistry, Vol. 12, pp. 2412–2415, 2002. [4] Aziz, M.S.A., Shaheen, M.S., El-Nekeety, A.A. and Wahhab, M.A.A., “Antioxidant and antibacterial activity of silver nanoparticles biosynthesized using Chenopodium murale leaf extract,” Journal of Saudi Chemical Society, Vol. 18, pp. 356–363, 2014. [5] Abe, N., Murata, T. and Hirota, A., “Novel DPPH Radical Scavengers- Bisorbicillinol and Demethyltrichodimerol, from a Fungus,” Bioscience, Biotechnology and Biochemistry, Vol. 62, pp. 661–666, 1998. [6] Srour, M.A., Bitto, Y.Y., Juma, M. and Irhimeh, M.R., “Exposure of human erythrocytes to oxygen radicals causes loss of deformability, increased osmotic fragility, lipid peroxidation, protein degradation”, Clin Hemorheol Microcircul, Vol. 23, pp. 13–21, 2000.

Effect of Excess Selenium in Formation of Cu2Zn1.5Sn1.2 (S0.9 + Se0.1)4 Alloys for Solar Cell Applications Sripan Chinnaiyah, Annamraju Kasi Viswanath and R. Ganesan1 Centre for Nanoscience and Technology, Pondicherry University, Pondicherry 1 Department of Physics, Indian Institute of Science, Bangalore, Karnataka

ABSTRACT Copper zinc tin sulphide/Selenide Cu2ZnSn(S, Se)4 (CZTSSe) is a alternative promising materials for solar cell. It exhibits high optical absorbance and tunable band gap. We have been investigated the effect of excess selenium to formation of CZTSSe phase and prepared by thermal molten method. The CZTSSe alloys were characterized by X-ray diffraction (XRD), Raman spectroscopy and UV-VIS spectroscopy. The crystallographic structure and phases were confirmed by X-ray diffraction and Raman spectroscopic technique. In Raman spectroscopy, we found that the phase shifts from 327 cm–1 to 338 cm–1when the selenium contentis 5% excess. In optical studies we have been found the band gap of CZTSSe alloys about 1.43 eV to 1.44 eV. Keywords: Cu2ZnSn(S, Se)4, Raman Spectroscopy, Solar Cell.

INTRODUCTION The development of clean energy resources as an alternative to the fossil fuel has become one of the most important tasks assigned to the researchers. Recently, the photovoltaic devices are demonstrated based on several semiconductor nanocrystal (NCs), including CdTe, Cu(In,Ga)Se2 and Cu(In,Ga)S2. Through this technologies have reached commercial module production with power conversion efficiency of 9%, their potential is restricted by the limited supply of In and Ga as well as by restrictions on the safe usage of Cd. Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) are two promising materials for Photovoltaic applications. Copper-Indium-Gallium-Selenide/Sulfide (CIGS) solar cell has achieved about 20% conversion efficiency in laboratory scale, which is one of the highest efficiency among various thin film solar cells. However, CIGS solar cell adopts rare earth materials. In this point of view, the Cu2ZnSn (S,Se)4 (CZTSSe) is very promising absorber material (1–4). It includes earth abundant materials Sn, Zn, moreover less toxic S and Se. In additions the CZTSSe exhibits excellent optical properties such as direct band gap of 1.1 to 1.5 eV and large absorption coefficient of 104 cm–1 in visible spectrum range.CZTS thin film has been prepared by various methods such as vacuum based synthesis and solution based synthesis. Band gap of CZTSSe thin film can be tuned by control of Stoichiometry composition. In this material theoretically predicted power conversion is 32.2%, but in experimentally they have been achieved 6.77% efficiency by vacuum based process (5) and other solution process method they have been showed 12.6%. However the device performance was greatly improved, basic researches on CZTSSe material itself are insufficient, for example fabrication of compositionally uniform CZTSSe film is still hard task due to loss of Sn V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 55–58 (2015)

56


during annealing process (7). Considering that high efficiency solar cell can be realized just with Cu poor and Zn rich CZTS (8), well adjustment of chemical compositions of CZTS is prerequisite. Based on these we adjusted the stoichiometry of Cu/(Zn+Sn) = 0.77 and Zn/Sn = 1.25 for well improve the grain size. Hence systematic sulfurization and experiments under controlled temperature and surrounding atmosphere came to be significant.

EXPERIMENTAL Polycrystalline Cu2Zn1.5Sn1.2(S0.9+Se0.1)4,x = 0% selenium and x = 5% selenium alloy was prepared by thermal molten technique using separate single source materials. The single source materials are prepared by taking elements in stoichiometry ratio of 2.0:1.5:1.2:4. Pure elements of Cu, Zn, Sn, S and Se (99.999% Alfa aeser) are weighed in atomic stoichiometry ratio and transferred to well cleaned quartz ampoule. The ampoules are sealed at 1 × 10–5 mbar vacuum and this ampoule was placed in electric furnace and slowly heated upto 500oC (5oC/min) and kept at 500oC for one hour. The temperature then further increased to 950oC. To ensure the homogeneity of the molten materials, the ampoules were rotated for 24 hrs at this temperature and gradually cool down to room temperature. Material Characterizations The structural analysis of the base material powder was done by XRD using Cu-Kα source (wavelength = 1.5405 Ao) with a diffraction angle from 10o to 80o degree (BRUKER D8-ADVANCE ), The investigation of the phase formation of CZTSe bulk materials are characterized by Raman spectroscopy using the excitation wavelength of 532 nm (HORIBA Jobin YVON Lab RAM HR800 spectrometer).The UV-Visible spectra of CZTSe alloy materials were recorded by Perkin Elmer UV/Visible spectrometer Lambda 35 in the range of 400 nm–1100 nm. RESULT AND DISCUSSION The structures of the as-synthesized alloys were characterized by XRD, as show in Figure 1a and 1b. The diffraction peaks of as-prepared CZTSSe alloys can be indexed to pure phase of kesterite structure (CZTSSe) (ICSD No: 184475). The major diffraction peak appeared at 2θ = 28.23o, 32.3o, 47.27o and 55.8oattributed to (112), (200), (220) and (312) hkl planes can be seen clearly. The lattice parametersa = b = 5.62 A0, c = 11.22 A° of the typical sample were similar to that described in the literature (8, 9). Also the secondary peaks SnSe and ZnS presented all excess selenium presented alloys. But in excess selenium content 5% the intensity of SnSe and ZnS very less compared to the 0% and 10% excess selenium.

Fig. 1: X-Ray Diffraction (XRD) Pattern of Synthesized CZTSSe Alloys in Different Excess Selenium

Effect of Exceess Selenium in Formation F of Cuu2Zn1.5Sn1.2 (S0.9 + Se0.1)4 Alloys for f Solar Cell Appplications

5 57

Fig. 2: X--Ray Diffractioon (XRD) Patterrn-Differentiatees the Peak Shift of o CZTSSe Alloys (0% and 5% % of excess seleenium)

A Also we have been b mentioned the differeentiation of (112) diffraction peaks shift of 0% and 5% % excesss selenium allloys. It has been b shown inn Figure 2. The T diffractionn peak shiftedd from smalleer 2θ vallues to higherr 2θ values ass the selenium m content incrreases, indicating that the replacement of o sulfurr with seleniu um (10). The Raman specctra of CZTS SSe and 5% of o excess sellenium of bullk materiials are shown n in Figure 3.. In bulk mateerials the prim mary vibration of Cu2Zn1.5Sn1.2(S0.9+Se0.1)4 was detected d at 32 27 cm–1 and 197 cm–1 duue to selenium m-selenium viibration, coulld not detecteed seconddary phases might m be due to the differrence in sensiitivity or its minute m presennce of CZTSS Se alloyss. InCu2Zn1.5Sn n1.2(S0.9 + Se0..1)4 + 5% exceess selenium thhe primary peaaks were deteccted at 337 cm m– 1 , 2877 cm–1 and 36 67 cm–1for CZ ZTS and 197 cm–1 and 2399 cm–1 for CZ ZTSe. The peaak shifted from m lower wave numberr to higher wavve number (100).

Fig. 3: Raman Sp pectroscopy of CZTSe C Alloys Indiffereent Excess Selennium

Fig. 4: Optical O Band Gaap of CZTSe Allloys in Differennt Exceess Selenium

The optical band gap (Eg) for f Cu2Zn1.5Snn1.2(S0.9+Se0.1)4 and 5% exxcess selenium m materials arre he absorbance co-efficient value v has >104 cm–1. The opptical band gap ap of material is calcullated where th determ mined by the Tauc T model annd the Davis and a Mott modeel [11]. It has been b shown inn Figure 4. (αhhν) = B(hν–Eg)n

… (33)

58


Where B is constant (Tauc parameter), h is Planck’s constant, ν is frequency, Eg is optical band gab and n is a number which related mechanism of transition process, the value of n is taken can be ½ for direct transition. In alloy with x = 0 alloy have a band gap of 1.44 eV is determined. If selenium content x = 5% the band gap decreased to 1.43 eV. Because of excess selenium may be attributed to the reduction in the number of unsaturated defect, which decreases the density of localized states in the band structure and consequently decreased the optical band gap.

CONCLUSION We have been investigated the effect of excess selenium to formation of CZTSSe phase and prepared by thermal molten method. The crystallographic structures of CZTSSe alloys phase were confirmed by X-ray diffraction and Raman spectroscopic technique. In Raman spectroscopy we found that the phase shifts from 327 cm–1 to 338 cm–1 when the selenium content is 5% excess. In optical studies we have been found the band gap of CZTSSe alloys about 1.43 eV to 1.44 eV. ACKNOWLEDGEMENT The authors thank Inorganic and Physical Chemistry and Department of Physics, Indian Institute of science, Bangalore, for XRD and UV-Visible characterizations. REFERENCES [1] Ito, K. and Nakazawa, T., Direct Liquid Coating of Chalcopyrite Light-Absorbing Layers for Photovoltaic Devices, Jpn. J. Appl. Phys., 27, p. 2094, 1988. [2] Katagiri, H., Saitoh, K., Washio, T., Shinohara, H., Kurumadani, T. and Miyajima, S., Development of thin film solar cell based on Cu2ZnSnS4 thin films, Sol. Energy Mater. Sol. Cells, 65, p. 141, 2001. [3] Seol, J.S., Lee, S.Y., Lee, J.C., Nam, H.D. and Kim, K.H., Electrical and optical properties of Cu2ZnSnS4 thin films prepared by rf magnetron sputtering process, Sol. Energy Mater. Sol. Cells, 75, p. 155, 2003. [4] Katagiri, H., Jimbo, K., Maw, W.S., Oishi, K., Yamazaki, M., Araki, H. and Takeuchi, A., Development of CZTS-based thin film solar cells, Thin Solid Films, 517, p. 2455, 2009. [5] Katagiri, H., Jimbo, K., Yamada, S., Kamimura, T., Maw, W.S., Fukano, T., Ito, T. and Motohiro, T., Enhanced Conversion Efficiencies of Cu2ZnSnS4 -Based Thin Film Solar Cellsby Using Preferential Etching Technique, Appl. Phys. Express, 1, p. 041201, 2008. [6] Todorov, T.K., Reuter, K.B. and Mitzi, D.B., Photovoltaic Devices: High-Efficiency Solar Cell with EarthAbundant Liquid-Processed Absorber, Adv. Mater., 22, p. E156, 2010. [7] Weber, A., Mainz, R. and Schock, H.W., On the Sn loss from thin films of the material system Cu–Zn–Sn– S in high vacuum, J. Appl. Phys., 107, p. 013516, 2010. [8] Mitzi, D.B., Gunawan, O.i., Todorov, T.K., Wang, K. and Guha, S., The path towards a high-performance solution-processed kesterite solar cell, Sol. Energy Mater. Sol. Cells, 95, pp. 1421, 2011. [9] Jiang, Chengyang; Lee, Jong-Soo and Talapin, Dmitri V., Soluble Precursors for CuInSe2, CuIn1–xGaxSe2, and Cu2ZnSn(S,Se)4Based on Colloidal Nanocrystals and Molecular Metal Chalcogenide Surface Ligands, J. Am. Chem. Soc., 134, pp. 5010–5013, 2012. [10] Yang, Wenbing; Duan, Hsin-Sheng; Bob, Brion; Zhou, Huanping; Lei, Bao; Choong-Heung; Li, ShengHan; Hou, William W. and Yang, Yang, Novel Solution Processing of High-Efficiency Earth-Abundant Cu2ZnSn(S,Se)4 Solar Cells, Adv. Mater. 24, 6323–6329, 2012. [11] Fischereder, Achi; Rath, Thomas; Haas, Wernfried; Amenitsch, Heinz; Albering, Jorg; Meischler, Dorith; Larissegger, Sonja; Edler, Michael; Saf, Robert; Hofer, Ferdinand and Trimmel, Gregor, Investigation of Cu 2ZnSnS 4 Formation from Metal Salts and Thioacetamide, Chem. Mater., 3399, 2010.

Controlled Synthesis of Novel Urchin Like Morphology of 1-D α-MnO2: Evolution and Catalytic Activities Ayonbala Baral, Malay Kumar Ghosh and Dipti P. Das CSIR—Institute of Minerals and Materials Technology, Bhubaneswar & Academy of Scientific and Innovative Research (AcSIR), IMMT, Bhubaneswar

INTRODUCTION Large volume waste water exit from textile, paint, pharmaceutical industries etc. are contaminated mostly with non-biodegradable organic compounds because such industries use organic and intermediate compounds for dyeing and colouring purposes [1–2]. Many techniques like advanced oxidation processes (AOP), catalytic adsorption, photocatalytic degradation, photochemical reaction process etc. have already been developed for wastewater treatment to reduce the dreadful effect of these organic dyes [3–5]. However, the most popular method for degradation of highly stable organic dyes is oxidation using solar energy and/or catalysts called as Advance Oxidation Process (AOP). The development of new and less expensive catalyst material for the treatment of dye containing waste water is rather challenging one considering the potential exploitation of the abundantly available solar light. In recent years, fabrication of hierarchical nano-structured metal oxides such as nanorods, nanofibers, nanobelts, nanosheets and nanospheres have attracted significant attention due to their wide application areas. Similarly nano-MnO2 has generated much interests due to its versatile and potential uses as catalyst, as magnetic materials, ion-sieves and energy carriers (super capacitor and batteries) [6-10]. MnO2 exists in several polymorphic forms such as α, β, γ and σ, each with distinct chemical and physical properties [6, 11]. In this study we report a synthesis procedure for urchin like α-MnO2 via simple chemical precipitation route without the use of any template. The photocatalytic activity of the synthesized product was tested through the photodegradation of two azo dyes - Congo Red (CR) and Methyl Orange (MO). The as-prepared catalyst effectively degrades both the dyes in a very short time period. EXPERIMENTAL Synthesis and Characterisation of α-MnO2 Analytical grade MnSO4.H2O and (NH4)2S2O8 in a ratio of 1:1.5 were added to 100 ml doubledistilled water, stirred for 1 h for homogenization, then transferred to a 250 mL capacity double-wall cylindrical glass reactor. The temperature of the solution in the inner vessel was maintained at 90°C for 4 h through hot water circulation from a thermostatic water bath to the outer compartment of the vessel. At the end of the experiment the black precipitate obtained was filtered and washed thoroughly with ethanol and then dried in oven at 70°C overnight. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 59–62 (2015)

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XRD patterns were generated in X’Pert PRO PAN Analytica diffractometer (Model: PW 1830) using Mo-Kα radiation in the 2θ range of 5–40o. Transmission Electron Microscope (Model: FEI, TECNAI G2 20, TWIN) operated at 200 kV was used to study the internal features of the sample. The surface morphology of the prepared sample was studied using Field Emission Scanning Electron Microscope (FESEM) (Model: Zeiss, SupraTM 55). The Raman spectrum was recorded in RENISHAW InVia Raman Spectrometer using argon ion laser beam at 540 nm.

Photocatalytic Activity Evaluation Photocatalytic efficiency of the synthesized sample was established based on the degradation of two azo dyes under visible light illumination. Experiments were carried out in 10 mL solution containing 30 mg of synthesized sample and 20 mg/L dye (MO, CR) solution in a closed pyrex flask of 100 mL capacity. The suspensions were centrifuged after irradiation and the dye concentration of the supernatant solution was measured using a UV-Vis spectrophotometer (Model: Cary-100, Agilent). RESULTS AND DISCUSSION Morphology and Crystal Orientations The phase purity of the as-synthesized sample was determined by XRD with Mo-Kα radiation. Figure 1 (a) shows that all the peaks of the XRD pattern are indexed to pure tetragonal phase of α-MnO2 (JCPDS 44–0141) with lattice constants a = 9.81 Å and c = 2.84 Å. Sharp diffraction peaks indicate the highly crystalline nature of the material. All the peaks belonging to α-MnO2 confirm the phase purity of the precipitated material.

Fig. 1: (a) XRD Pattern of α-MnO2, (b) FESEM Image of α-MnO2 in Lower Magnification, (c) FESEM Image of α-MnO2 in Higher Magnification

FESEM image of the as-prepared α-MnO2 at low magnification (Figure 1b) clearly indicates large numbers of microsphere with urchin like morphology. At high magnification it is observed that microsphere is assembled from many needle-like nanorods (Figure 1c). The nanorods are aligned and radially oriented with their growth axis perpendicular to the surface of the microsphere which results in the shape of urchin. Figures 2a and 2b are the TEM images of the synthesised product which also establish that the 3D urchin like α-MnO2 is composed of self-assembled 1D nanorods with average length of ~ 400–500 nm and diameter of ~ 30 nm. The structural features were further examined using Raman spectroscopic measurements presented in Figure 2c. Generally, Raman bands for α-MnO2 are found in three regions: 180–450, 450–550 and 550–700 cm–1 [6, 7]. The low frequency band near 185cm–1 is attributed to the external

Controlled Synthesis of Novel Urchin Like Morphology of 1-D α-MnO2

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vibration due translational motion of MnO6 octahedra while the band at 390 cm–1 is due to Mn-O bending vibrations of MnO2 lattice. The peaks at 574 and 649 cm–1 in the present sample are the characteristic Raman bands of α-MnO2 with 2×2 tunnel which are attributed to Mn-O stretching vibrations of MnO6 octahedra. Previous studies also indicate that α-MnO2 exhibits four main Raman bands at 185, 392, 582 and 649 cm–1 [6].

Fig. 2: (a) TEM Image of Urchin Like α-MnO2 (b) TEM Image of an Individual Nanoparticle (c) Raman Spectrum of the As-Prepared Material

Photodegradation of Azo Dyes In this study the urchin like α-MnO2 was used as catalyst for the degradation of azo dyes - Methyl Orange and Congo Red under visible light illumination. The results (Figure 3) indicate that α-MnO2 is a potential catalyst which can degrade these dyes within 10 min. Almost 95% degradation rate was observed in case of Methyl Orange and 100% in case of Congo Red using the α-MnO2 nanomaterial as photocatalyst. High photocatalytic activity of this catalyst is evidenced by more than 90% photodegradation in only 2 min of irradiation.

Fig. 3: Degradation Rates of (a) Methyl Orange, (b) Congo Red Over Urchin Like α-MnO2. Co and C are Initial and Final Dye Concentration in Solution (mg/L)

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CONCLUSIONS The template-free and low temperature simple precipitation method successfully prepared urchin-like α-MnO2 nanostructure. The phase purity is 100% because all the XRD peaks match well with α-MnO2 peaks. The sharp and intense peaks confirm well crystalline nature. The 3D urchin-like shape is composed of self-assembled 1D nanorods. High photocatalytic activity of as-synthesized α-MnO2 is established through the photodegradation of Methyl Orange and Congo Red dyes. About 100% CR and 95% MO degradation efficiency within 10 minutes suggests that α-MnO2 is a potential photocatalyst for photooxidation of azo dyes under visible light irradiation. REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]

Hachem, C., Bocquillon, F., Zahraa, O. and Bouchy, M. Dyes and Pigments 2001, 49, 117–125. Bejarano-Perez, J.N. and Suarez-herrera, F.M. Ultrason. Sonochem. 2007, 14, 589–595. Dogan, D. and Turkdemir, H. J. Chem. Technol. Biotechnol.2005, 80, 916–923. Kim, T.-H., Park, C., Yang, J. and Kim, S. J. Hazard. Mater. 2004, 112, 95–103. Soltani, N., Saion, E., Hussein, M. Z., Erfani, M., Abedini, A., Bahmanrokh, G., Navasery, M. and Vaziri, P. Int. J. Mol. Sci. 2012, 13, 12242–12258. Sun, M., Lan, B., Lin, T., Cheng, G., Ye, F., Yu, L., Cheng, X. and Zheng, X. Cryst. Eng. Comm. 2013, 15, 7010–7018. Li, Y., Wang, J., Zhang, Y., Banis, M. N., Liu, J., Geng, D., Li, R. and Sun. X. J. Colloid Interf. Sci. 2012, 369, 123–128. Wu, J., Huang, H., Yu, L. and Hu, J. Adv. Mater. Phy. Chem, 2013, 3, 201–205. Tompsett, A.D., Parker, C.S. and Islam, S.M. J. Mater. Chem. A 2014, 2, 15509–15518. Jaganyi, D., Altaf, M. and Wekesa, I. Appl. Nanosci. 2013, 3, 329–333. Wang, X. and Li, Y., J. Am. Chem. Soc. 2002, 124, 2880–2881.

Ni3S2-Swcnhs Nanocomposite as an Efficient Catalytic Counter Electrode for Dye Sensitized Solar Cell Application K. Susmitha and M. Raghavender Department of Physics, Yogi Vemana Univesity, Kadapa, Andhra Pradesh

ABSTRACT Ni3S2, Ni3S2-SWCNHs synthesized via facile glucose assisted hydrothermal method and were employed as a counter electrodes (CE) in dye sensitized solar cells (DSSCs). DSSC with Ni3S2SWCNHs CE exhibitsthe least charge transfer resistance and superior solar cell efficiency (η) (1.21%) than Ni3S2 and was confirmed by electrochemical impedance spectroscopy. The present study describes a novel selectiv approach and facile fabrication procedure for low cost counter electrode materials in DSSCs.

INTRODUCTION Dye sensitized solar cells (DSSCs) was an attractive photovoltaic form owing to their cost-effective and eco-benign fabrication, as well as constantly increasing power conversion efficiency up to 11%. Since the DSSC was invented by O’Regan and Gratzel in 1991 [1]. Typically, a DSSC composed of photo electrode (dye sensitized nanocrystilineTiO2 electrode), counter electrode (CE) and an electrolyte containing a tri-iodide/iodide (I3–/I–). Among various components of the DSSC, CE was crucial and indispensible component, whichserve to collect electrons from external circuit and accelerate the I3– reduction reaction. Noble metal Pt was the most effective CE material due to the excellent electrocatalytic activity toward I3–reduction. Nevertheless, Pt was relatively expensive, thus the high price of noble metal Pt restrains the widespread application of DSSC. Therefore, the exploration of many functional materials were introduced as an alternative CE to Pt with inexpensiveand highelectrocatalyticacitivity. These include carbonaceous materials [2], transition metal oxides [3], and sulfides [4]. Recently, the overture of single wall carbon nanohorns (SWCNHs) was used as CE in DSSC applications [6]. SWCNHs consists of tubular structures with 2–5 nm in dia and 30–50 nm in length that associate into roundish aggregates of dia 100 nm, with high surface area (ca. 300–350 m2 g–1). EXPERIMENTAL Synthesis of Ni3S2/SWCNHs as 7.5 mg of oxidized SWCNHs (7.5 mg) and glucose (90 mg) were added to the 10 ml mixture solution of ethanol and distilled water (9 :1). Nickel chloride (195 mg), thiourea (76 mg) were added to the ox-SWCNHs dispersionand then transferred to a stainless steel autoclave. After sealing, the autoclave was heated to 180°C for 12 h and then cooled to room temperature. Finally, the precipitate was filtered off, washed with distilled water and dried in air at 80°C. The Ni3S2 powder was also synthesized using the glucose assisted hydrothermal method. Except for the addition of SWCNHs, the synthetic procedures for Ni3S2 powder were the same as those for Ni3S2/SWCNHs. Photo electrodes were fabricated by screen printing of TiO2 paste of area 0.16 cm2 on pre-cleaned FTO, sintering at 500°C and followed by dipping in N719 dye solution for 16 h. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 63–64 (2015)

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Ni3S2/SWCNHs / an nd Ni3S2 counnter electrodess were prepareed by drop caast. DSSC waas fabricated by b sandw wiching of pho oto, counter eleectrode using surlynfilm, foollowed by fillling of electrollyte.

RESU ULTS AND DISCUSSIO D NS FESEM image of Ni N 3S2- SWCN NH is shown in Figure 1 inn which largee plates of Ni3S2and roughlly spheriical shaped SWCNHs S parrticles are obbsevered. Thee photocurrentt density (J) - voltage (V V) measuurements weree conducted using u a solarr simulator PE EC-L01 (PEC CCELL Inc., Japan and J-V V curvess of DSSCs arre shown in Figure 3.and coorresponding photovoltaic p p parameters weere summarizeed in Tabble 1. The dev vice with Ni3S2/SWCNHs CE C was show wn the photocuurrent density (JSC) of 7.55 ± 2 0.20 mA/cm m , an open o circuit vooltage (VOC) of o 0.58 ± 0.033 V, and fill factor f (FF) off 0.28 ± 0.03 to t yield power converrsion efficienccy (η) of 1.211%. Under sim milar test celll conditions, the t device witth Ni3S2 shown an effiiciency of 0.4998%.

F 1: SEM Imaage of Ni3S2Fig. SWCN NH

Fig. 2: EIS Characterizattion of Cs the Faabricated DSSC

Fig. 3: J-V Charactterization of thee Fabricated DSSCs D

EIS measuremeents were perfformed to study the electroo-catalytic actiivities the prisstine Ni3S2 annd Ni3S2/SWCNHs. / Figure 2 preseents the Nyquuist plots of DSSCs with Ni3S2 and Ni N 3S2/SWCNH Hs. Furtheermore, to ev valuate seriess resistance (R Rs), charge-trransfer resistance (Rct) annd capacitancce valuess, the equivaleent circuit useed to simulate the Nyquist plots p of cells and were pressented Table 1. The loower Rs, Rct of Ni3S2/SWCNH srevealss the larger ellectron injectiion associates the larger Jsc, whichh could result in improved efficiency. The T lower effi ficiency couldd be due to veery thin Ni3S2SWCN NHs, Ni3S2 fillms, further opptimization is in progress. DSSC CE D Ni3S2-SWCNHs Ni3S2

Table 1: 1 EIS and J-V Parameters of Fabricated F DSSCs Rs(KΩ) R (KΩ) Rct Js (mA/cm2) Jsc F Factor Fill Voc (V) 0.243 16.74 7.55 0.575 0 0.278 0.847 1 126 2 2.54 0.638 0 0.303

Efficiency (%) E 1.21 0.50

CONCLUSIONS Ni3S2 and Ni3S2/SW WCNHs synthhesized successsfully througgh a facile hyddrothermal meethod and useed for CE Ein DSSC. Nii3S2/SWCNHss DSSC show wn higher efficciency (1.21% %) than Ni3S2(00.498%) due to t largerr electron injecction associatees the larger Jsscin Ni3S2/SW WCNHsnanocoomposite C.E. REFE ERENCES [1] [2] [3] [4] [5]

O'regan, B. and d Gratzel, M., Nature, N 353, 7377–739, 1991. Chen J.K., et all., Carbon, 47, 2704–2708, 2 20009. W M.X. et all., Chem. Comm Wu, mun, 47, 4535–44537, 2011. X Xiaoli, D., et all., Electrochim. Acta., 114, 1733– 179, 2013. Cruz. R.z, et all., Int. J. Energyy Res. 37, 1498––508, 2013.

Bio Mediated Synthesis of Dy3+ Doped Y2O3 Nanophosphor: Structural and Luminescence Studies J.B. Prasanna Kumar1,2, G. Ramgopal3, K.S. Anantharaju4, B. Daruka Prasad5, S.C. Prashantha6, H. Nagabhushana7 and C. Suresh1,7 1

Department of Physics, GFGC Tumkur, Tumkur, Karnataka 2 Department of Physics, Sathyabama University, Chennai 3 Department of Physics, Maharani’s Science College, Bangalore 4 Dayanand Sagar University, Shavige Malleshwara Hills, Kumaraswamy Layout, Bengaluru 5 Department of Physics, BMS Institute of Technology, Bangalore 6 Research Center, Department of Science, East West Institute of Technology, Bangalore 7 Prof. CNR Rao Centre for Advanced Materials, Tumkur University, Tumkur E-mail: [email protected]; [email protected]

ABSTRACT We report the synthesis of Y2O3:Dy3+ (1mol %) nanoparticles (NPs) with different morphologies via eco-friendly, inexpensive and low temperature solution combustion method using Leucasaspera gel as fuel/surfactant. The prepared compounds were characterized by PXRD, SEM, PL techniques etc. The PXRD data confirms the formation of single phase, cubic structure. The morphology of sample is found to be spherical flaky shaped. NPs exhibit white light emission with CIE chromaticity coordinates (0.32, 0.33) and correlated color temperature values is 5525 K. These findings show a great promise of Y2O3: Dy3+ NPs as a phosphor in warm white LEDs. Keywords: Leucasaspera, Y2O3: Dy3+Nanophosphors, SEM, PXRD.

INTRODUCTION The nanostructures with unique morphology and novel properties were of great attention to material scientists since the physical, chemical, optical, luminescence and catalytic properties strongly depends on morphology of the nanostructures. Yttrium oxide (Y2O3) received significant attention in recent years due to its wide range of scientific and technological applications namely luminescent displays, photoelectric devices, optical communication, biological and chemical probes [1–2]. Yttrium oxide (Y2O3) is a versatile interesting material which exhibits interesting physical properties namely wide energy band gap (5.3eV), high dielectric constant (8–12), optically isotropic and refractive index of 1.91. A low temperature combustion method was used for the synthesis of Y2O3: Dy3+(1mol %) using Leucasasperagel as fuel. The solution combustion method is of low cost and large-scale production, which does not need expensive raw materials and complicated equipment. EXPERIMENTAL For the synthesis of Y2O3: Dy3+ (1 mol %), aqueous mixture of yttrium nitrate and dyrsposium nitrate solution was subsequently added to the required amount of Leucasasperagel (10 ml) by constant V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 65–68 (2015)

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stirring on a magnetic stirrer for ~10 min. The dish was introduced into a furnace preheated at 400 ± 10 °C. The solution immediately started to boil and undergoes dehydration followed by decomposition of the metal nitrates. Finally product obtained was grinded well to fine powder. The resultant products were calcinated at 750°C for 3 h for better crystallinity.

RESULTS AND DISCUSSION Figure 1 show the PXRD patterns of Y2O3: Dy3+ (1–11 mol%) NPs. All diffraction peaks were well indexed to cubic Y2O3 with JCPDS No. 88–1040 [3]. As the Dy3+ concentration increases, the diffraction peaks broadens and shifts towards lower angle side. The broadening and shifting in (222) peak positions with increase in Dy3+ ions indicate a small variation in lattice constant. The intensity of (222) plane increases with increase in Dy3+ concentration upto 3 mol % and thereafter it decreasesimplying the degeneration of crystallinity at higher doping concentration and no characteristic peaks of any impurities were detected in the patterns, which indicates that all the samples have high phase purity. The crystallite size (D) of NPs was estimated using Scherrer’s equation [4]. It is found be in the range of 19–30 nm. Y 2O 3: D y

3+

11 m ol %

Intensity (a.u)

9 m ol %

7 m ol %

5 m ol % J C P D F N o . 8 8 -1 0 4 0 3 m ol % (2 2 2 )

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(444)

(622)

40 50 2 θ (D e g r e e s)

(136)

(611)

(440)

(334)

(332)

(411)

(400)

(211)

20

1 m ol %

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Fig. 1: PXRD Patterns of Y2O3: Dy3+ (1–11mol%) NPs

Figure 2 shows the SEM picture of Y2O3: Dy3+ (1mol %) NPs in the presence of 10 ml of Leucasasperagel. It was observed that a spherical flaky shaped morphology was observed [5].

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Fig. 2: SEM Image of Y2O3: Dy3+ (1mol %) NPs

The PL measurements were performed to verify how the morphology of Dy3+ ion doping on Y2O3 affects their emission properties. Figure 3 presents the excitation spectrum of Y2O3: Dy3+ (1 mol %) monitored at 576 nm. The excitation spectra in the range 300–550 nm consists of different excitation bands centered at 303 (6H15/2→4D7/2), 351 (6H15/2→6P7/2), 389 (6H15/2→4M21/2), 450 (6H15/2→4J15/2). The remaining peaks 468, 482, 492 and 526 nm are corresponds to 4f-4f transitions of Dy3+ ions. A typical emission spectra of Y2O3: Dy3+ (1–11 mol %) NP prepared with green synthesis method under excitation wavelength of 351 nm is as shown in Figure 3 (a). The emission spectra of Y2O3: Dy3+ (1–11 mol %) under 351 nm excitation presents sharp bands at blue region 486 nm (4F9/2→6H15/2 transition), Yellow region 576 nm, 582 nm (4F9/2→6H13/2 transition) and red region 667 nm (4F9/2→6H11/2 transition). From the figure, it is observed that the yellow emission was prominent compared to blue and red emission [6].

6

2x10

6

1x10

6

3x10

350

400

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450

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Fig. 3: The Excitation Spectrum of Y2O3: Dy3+ (1mol %) NP

550

7

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2x10

ex

Y 2O 3: Dy

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10

1 mol % 3 mol % 5 mol % 7 mol % 9 mol % 11 mol %

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a

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Y 2 O 3 : Dy (7 mol %)

PL Intensity (a.u)

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F9/2−> H13/2

3+

λ ex = 576 nm 6

5x10

5x10

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468 nm 482 nm 492 nm

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8x10

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6

F9/2−> H11/2

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F9/2−> H15/2

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650

Fig. 3(a): The Emission Spectra of Y2O3: Dy3+ (1–11 mol %) under 351 nm

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The Commission Internationale de I’eclairage (CIE) coordinate of the NPs is calculated. It is found to be (0.32, 0.33) which is closed to that of the ideal white light. The emission of white light from this NP can be attributed to comparable intensities of Dy3+ emissions in the visible range of electromagnetic spectrum. Correlated color temperature (CCT) is determined from CIE coordinates and it is found to be 5525 K which corresponds to vertical day light. Figure 4(A-B) shows the CIE chromaticity and CCT diagram of Y2O3: Dy3+ (1–11 mol %) respectively[7]. 0.9

0.6

3+

A

Y2O3:Dy (λexc-351 nm)

0.5

3+

Y 2O 3:Dy (λ exc-351 nm)

B

~ 5525 K

0.6

Y

V'

0.4 0.3

0.3 X 0.34493 0.33646 0.33308 0.32914 0.32794 0.32333

0.0 0.0

0.2

0.4

X

0.6

Y 0.37821 0.34917 0.34366 0.34212 0.34044 0.33433

0.8

u' 0.2015 0.2065 0.2063 0.2042 0.204 0.2032

0.2 0.1

0.1

0.2

0.3

0.4

v' 0.497 0.4822 0.4789 0.4776 0.4766 0.4727

0.5

CCT 5074 5333 5471 5643 5699 5928

0.6

U'

Fig. 4 (A-B): The CIE Chromaticity and CCT Diagram of Y2O3: Dy3+ (1–11 mol %) Respectively

CONCLUSIONS In summary, Y2O3: Dy3+ (1mol %) NPs were synthesized by a facile, ecofriendly, inexpensive, bioapproach solution combustion route using Leucasasperagel as a fuel. The structural, optical, morphology and PL emissions were studied. Upon 351 nm excitation, Y2O3: Dy3+nanophosphor exhibit an intense white emission with CIE co-ordinates (0.32, 0.33) and CCT (5525 K) which corresponds to vertical day light. Thus the present nanophosphor can serve as a better candidate for WLEDs. REFERENCES [1] Mudavakkat, V.H., Noor-A-Alam, M., Bharathi, K. Kamala, AlFaify, S., Dissanayake, A., Kayani, A. and Ramana, C.V., Thin Solid Films, 519 (2011), 7947–7950. 21. [2] Li, C.X. and Lin, J., J. Mater. Chem. 20 (2010), 6831– 6847. [3] Shilpa, C.J., Dhananjaya, N., Nagabhushana, H., Sharma, S.C., Shivakumara, C., Sudheerkumar, K.H., Nagabhushana, B.M. and Chakradhar, R.P.S., Spectrochim. ActaA Mol. Biomol. Spectr. 128 (2014), 730–739. [4] Prasannakumar, J.B., Ramgopal, G., Vidya, Y.S., Anantharaju, K.S., Prasad, B. Daruka, Sharma, S.C., Prashantha, S.C., Premkumar, H.B. and Nagabhushana, H., Spectrochim. ActaA Mol. Biomol. Spectr. 141(2015), 149–160. [5] Prashantha, S.C., Lakshminarasappa, B.N. and Nagabhushana, B.M., J. Alloys Compd, 509 (2011), 10185–10189. [6] Prashantha, S.C., Lakshminarasappa, B.N. and Singh, Fouran, Curr. Appl. Phys. 11 (2011), 1274–1277. [7] Meetei, S.D. and Singh, S.D., J. Alloys Comp. 587 (2014), 143–147.

Synthesis and Characterization of CZTS Nanoparticles for Photovoltaic Applications Ajay Dumasiya and N.M. Shah AN Shah Science College at and Post Kamrej Char Rasta, Surat E-mail: [email protected]

ABSTRACT In recent past Kesterite phase Cu2ZnSnS4 (CZTS) has attracted many researchers due to its high absorption coefficient and direct energy band gap in the range of 1.3 to 1.5 eV suitable for photovoltaic applications. In this study we have synthesized CZTS nanoparticles using Ball MillingTechnique. As synthesized nanoparticles were characterized using X-ray diffraction technique and energy dispersive analysis of X-rays (EDAX). The analysis of XRD results shows the preferred orientation of the grains in (112), (220) and (312) direction confirming Kesterite structure of CZTS. EDAX analysis suggests stoichiometry of elements. Analysis of diffuse reflectance spectra of as synthesized nanoparticles suggests the band gap of 1.43 eV, very close to the optimum value of band gap needed for its use as an absorber material in CZTS based thin film solar cell applications. Keywords: CZTS Nanoparticles, XRD Analysis, EDAX analysis, Diffuse reflectance spectra

INTRODUCTION Cu2ZnSnS4 herein collectively denoted as CZTS is a p-type quaternary compound semiconductor with Kesterite crystal structure. CZTS has absorption co-efficient of the order of 104cm–1 and direct optical band gap in the range of 1.3–1.5eV. This is why it is useful as an absorber layer in thin film solar cells [1]. CZTS in the form of nanoparticles are useful to prepare high efficiency, low cost photovoltaic device using simple, easily scalable deposition techniques. In this study, we have synthesized CZTS nanoparticles using Ball Milling Technique. Structural compositional and optical properties of as synthesized nanoparticles are studied for its’ possible application as a starting material to deposit CZTS thin film using screen printing technique. EXPERIMENTAL CZTS bulk was synthesized by direct reactionof analytical grade Copper (Cu), Zinc (Zn), Tin (Sn) and Sulphar (S) purchased from Merck India. The elements weighed in stoichiometric proportion(with 20% excess S) were sealed in a quartz ampoule at pressure of10−5 mbar. The melting of elements mixed in ampoulewas then carried out in muffle furnace at heating rate of 4K/min up to 1300 K. To ensure homogeneity of the melt, the meltwasheld at 1300 K for 24 h. The melt was then cooled down to roomtemperature inside the furnace at a cooling rate of 6 K/min. The solidingot was then powdered using theprocess of grinding and then sieving. The as prepared CZTS powder was then reduced to nanosize using Ball milling Technique. The structural characterization ofas-prepared CZTS nanoparticles was studied carried out using an X-Ray diffractometer Rigakuminiflex-II in 2θ range of V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 69–72 (2015)

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10º–80ºusing Cu-Kα radiation [λ = 1.5405 Å].Chemical composition analysis of CZTS was carried out using Hitachi S 3400 Scanning Electron Microscope equipped with Energy Dispersive X-Ray Analysis(EDAX) facility. In order to study the optical properties of CZTS nanoparticles, diffuse reflectance spectraof CZTS nanoparticles were reorded in the wavelength range of 300–1800 using UV – Vis spectrophotometer.

RESULTS AND DISCUSSIONS Structural and Compositional Characterization Figure 1 shows the XRD spectrum of CZTS nanoparticles. The analysis of XRD data suggests strong peaks at 2θ values 28.68, 47.50, 56.30 corresponding to peaks at (112), (220) and (312) confirms the formation of Kesterite CZTS phase.

Fig. 1: XRD Spectrum of Synthesized CZTS Nanoparticles

The lattice parameters calculated for CZTS nanoparticles from XRD analysis come out to be a = 5.402 Å and c = 10.725 Å which are in the very good agreement with the reported values [2].Figure 2 shows EDAX spectrum of CZTS nanoparticles. Analysis of EDAX data suggests stoichiometry of elements.

Fig. 2: EDAX Profiles of CZTS Nanoparticles

Synthesis and Characterization of CZTS Nanoparticles for Photovoltaic Applications

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Optical Characterization In order to study the optical properties of synthesized CZTS nanoparticles, reflectance R for corresponding wavelength λ were measured in the wavelength range of 300–1800 nm. Absorption coefficient k was determined from reflectance data using Kubelka – Munk theory. Figure 4 shows the graph of (khυ)2versus hυ.

Fig. 3: Plot of ሺ݄݇‫ݒ‬ሻଶ ՜ ݄‫ݒ‬

Energy band gap estimated from straight line portion of the graph was1.43 eV, which is in close agreement to reported value [4].

CONCLUSIONS CZTS nanoparticles were successfully prepared from synthesized powder using Ball Milling Technique. Thestructural characterization of CZTS nanoparticlesrevealed the formation of single phase CZTS compound with good crystalline quality. The analysis of EDAX data confirms stoichiometry of the elements in the compound. The optical band gap of the CZTS nanoparticles was 1.43 eV. REFERENCES [1] Chen, Qinmiao; Cheng, Shuyi; Zhuang, Songlin and Dou, Xiaoming, Cu2ZnSnS4 solar cell prepared entirely by non-vacuum processes, Thin Solid Films, 520, 6256–6261, 2012. [2] Zhou, Min; Gong, Yanmei; Xu, Jian; Fang, Gang; Xu, Qingbo and Dong, Jiangfeng, Colloidal CZTS nanoparticles and films: Preparation and characterization, Journal of Alloys and Compounds, 574, 272–277, 2013.

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[3] Ebraheem, Saif and El-Saeed, Antar, Material science and applications, Band Gap Determination from Diffuse Reflectance Measurements of Irradiated Lead Borate Glass System Doped with TiO2 by Using Diffuse Reflectance Technique, 4,,324–329, 2013. [4] Lydia, R. and Reddy, P. Shreedhra, Journal of Nano and Electronic Physics, Structural and Optical Properties of Cu2ZnSnS4 Nanoparticles for Solar Cell Applications, 5(3), 03017–03019, 2013.

Preparation and Characterization of Porous Silicon Photoelectrode for Dye Sensitized Solar Cells K. Gangadevi, K. Ramachandran1 and R. Srinivasan Department of Physics, Thiagarajar College, Madurai School of Physics, Madurai Kamaraj University, Madurai E-mail: r_srini@[email protected]

1

ABSTRACT The nanostructured porous silicon (PS) samples were prepared by electrochemical anodic dissolution of doped silicon (p-Si) for (100) orientation at constant current density of 30mA/cm2 for different etching times 10 and 60 min. Then the samples were sensitized with chloroaluminium phthalocyanine (ClAlPc) to fabricate Dye-sensitized solar cells (DSSCs). The bandgap measurements from UV- Vis and photoluminescence measurements are in the range of 1.5 to 1.8 eV. The SEM images confirmed the porous formation of the samples. The photocurrent and photovoltage of the cells was measured using Keithely source meter. The maximum conversion efficiency of 2.8% is observed and results are discussed.

INTRODUCTION Dye-sensitized solar cells (DSSCs) are regarded as a promising low cost option to conventional solidstate semiconductor solar cells due to the use of relatively cheap materials and the easy manufacturing techniques. A very important component of DSSCs is the photoelectrode, which includes a nanocrystalline porous wide bandgap oxide semiconductor layer with large internal surface area. The Commercial solar cells are fabricated using crystalline silicon which is costly in nature, where the maximum efficiency of 24.5% is reported in literature [1]. In this work, we measured the conversion efficiencies of DSSCs prepared from porous silicon with different porosities. EXPERIMENTAL Porous silicon samples were prepared by electrochemical etching of p-type (100) silicon wafers (thickness 517 μm and resistivity 0.2–0.5 Ω cm) at a constant current density of 30 mA/cm2 for the etc.hing periods of 10 and 60 minutes. The dye solution was prepared by mixing the synthesized ClAlPc dye in 5 ml of ethanol and used to sensitize the nanostructured PS samples to prepare photoanode. The photoanodes were characterized by XRD, SEM, UV-vis and PL techniques. The prepared samples of PS/ClAlPc photoanode with different porosities were used to fabricate DSSCs and then I -V measurement was carried out.


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RESULTS AND DISCUSSION

a

20

30

PS (4 0 4)

PS ( 2 0 0)

( 2 0 0)

b

I (counts)

b

B

PS (4 0 4)

A

PS ( 2 0 0)

XRD Measurement The XRD patterns of PS and ClAlPc/PS prepared at constant current density of 30mA/cm2 and etching times 10 and 60 min is shown in Figure 1 A and B respectively.

a 40

50

60

10

20

30

40

50

60

70

2θ (deg)

Fig. 1: XRD Pattern of the Samples Prepared at 30 mA/cm2 for (a) 10 min (b) 60 min: (A) PS (B) ClAlPc/PS

The characteristic peaks at 2θ = 24.82° and 64.77º in Figure 1A depict porous nature of the silicon, which is identified as (111) and (404) plane respectively and in agreement with the JCPDS values. In Figure 1B, the peak 2θ = 6.31◦ for ClAlPc agree well with the reported value [10] and identified as the (2 0 0) plane of α-phase structure and the lattice spacing d = 12.88 A°. Further it is noted that the intensities of the peaks increase with etching time and hence the porosity, as the porosity increases with etching time [2]. The sample prepared at 30mA/cm2, 60 min shows a broadened peak indicating it is more nanostructured in nature. The crystallites sizes calculated from Scherrer’s approximation are in the range of 12 to 61 nm.

Scanning Electron Microscopy The SEM image of the PS sample is shown in Figure 2. The porosity of the sample increases with increasing etching time. a

b

Fig. 2: SEM Image of PS Samples Prepared at 30 mA/cm2 for Etching Time (a) 10 min (b) 60 min

Preparation and Characterization of Porous Silicon Photoelectrode for Dye Sensitized Solar Cells

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Optical Measurements Band gap measurements done by UV absorption measurements and photoluminescence (PL) emission for all the above PS and ClAlPc/PS samples at room temperature are in good agreement (Table 1). The PL emission spectra of PS and ClAlPc/PS samples are shown in Figures 3A and 3B respectively. The PL intensity of the PS sample increases with increasing etching time. It is observed that the band gap of PS is slightly blue shifted with increase in etching time. This shift in band gap (band gap widening) is because of quantum confinement due to reduction in the size of the Si nanocrystallites for increasing etching time [3]. The decrease in crystallite size is attributed to the increase in porosity with increase in etching time [4]. The porosities of the samples calculated grom gravimetric method are in the range of 55 % to 78%.

B

A

60000

PL Intensity (a.u)

4000

b

50000

a

3500 40000 3000 30000 2500

b

20000 2000 10000

a

0 400

500

600

1500 700

800

650

700

750

800

Wavelength (nm) Fig. 3: Photoluminescence Spectra of PS Samples Prepared at 30 mA/cm2 for (a) 10 min (b) 60 min: (A) PS (B) ClAlPc/PS. Table 1: Bandgap of Samples Etching Time a (10 minutes) b (60 minutes)

PS PL 1.81 2.02

Band Gap in eV ClAlPc/PS UV PL UV 1.81 1.60 1.59 2.05 1.76 1.77

For the dye sensitized PS (ClAlPc/PS), the PL emission is shifted to 735 nm which may due to the presence of chlorine in the dye. The PL emission intensity of ClAlPc/PS decreases with increasing etching time [5] and this is due to the enhanced absorption with an increase in porosity and confinement of particles into a lower dimension. The minimum emission intensity shown by

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ClAlPc/PS prepared at current density of 30mA/cm2 with etching time of 60 min (Figure 2B) indicates that it is a good absorber of radiation and can be used for solar cell application.

I-V Measurements Performance of DSSCs (1 cm2 size) was analyzed by current - voltage (I–V) characteristics. Photocurrents and voltages were measured using a Keithely source meter 2400, with an 80 W halogen lamp and AM 1.5 G. The conversion efficiency of the samples is given in Table 2. The literature value of conversion efficiency of ClAlPc is 2.1% [6]. Table 2: Conversion Efficiency of the Samples Efficiency (%)

Porosity of PS (%)

a (10 min)

0.84

55

b (60 min)

2.84

78

CONCLUSIONS Nanostructured porous silicon (PS) samples were prepared at constant current density 30mA/cm2 for etching times 10 and 60 min. The samples were characterized by XRD, UV-Vis and PL emission techniques. The band gap slightly increases with increase in etching time. To study the effect of dye sensitizer, the surface of these PS samples was sensitized with derivative of Chloroaluminum Pc (ClAlPc). The variation porosities are confirmed by SEM analysis. The dependence of absorption and emission intensities on these samples indicate that ClAlPc/PS prepared at current density of 30 mA/cm2 for etching time of 60 min indicate that it is good absorber of radiations and can be used for solar cell application. The maximum efficiency of the DSSC was 2.8%. ACKNOWLEDGMENT The authors acknowledge the University Grant Commission (UGC), India, for financial support in the form of Major research project (F.No.41-941/2012 (SR)). REFERENCES [1] [2] [3] [4] [5]

Regan, B.O. and Gratzel, M., Nature, 353, 737–739 (1991). Kim, H., Lee, C., Lee, D.H. and Hong, S.S., J Korean Phys. Soc. 53 (5), 2562–2565 (2008). Azim-Araghi, M.E., Karimi-Kerdabadi, E. and Jafari, M.J., Eur. Phys. J. Appl. Phys. 55, 302–303 (2011). Prabakaran, R., Kesavamoorthy, R. and Singh, Alok, Bull. Matter. Sci., 28, 219–221 (2005). Jayachandran, M., Paramasivam, M., Murali, K.R., Trivedi, D.C. and Raghavan, M., Mater Phys. Mech. 4, 143 (2001). [6] Walter, Michae G., Rudine, Alexandar B. and Wamser, Carl C., J. Porphyrins Pthalocyanine, 14, 759–762 (2010).

TiO2 Based Dye-Sensitized Solar Cell Using Natural Dyes J. Kalaivani, K. Renukadevi1, K. Ramachandran2 and R. Srinivasan Department of Physics, Thiagarajar College, Madurai Department of Physics, G.Venkataswamy Naidu College, Kovilpatti 2 School of Physics, Madurai Kamaraj University, Madurai

1

ABSTRACT Nanostructured TiO2 thin films were prepared for various thicknesses on indium - doped tin oxide (ITO) conductive glass by the spin coating method. The anthocyanins dye was used to sensitize the sample. The structural characterization was done by XRD. The bandgaps from UV- Vis and photoluminescence measurements are in the range of 2.41 to 2.59 eV. The photocurrent and photovoltage of the cells was measured using Keithely source meter. The maximum conversion efficiency of 0.24% is observed and the results are discussed.

INTRODUCTION Dye-sensitized solar cells (DSSC) are expected to be used for future clean energy [1, 2]. A dyesensitized solar cell is usually composed of a dye-capped nano crystalline porous semiconductor electrode, a metal counter electrode, and a redox electrolyte containing iodide and triiodide ions. The performance of the cell is primarily dependent on the material and quality of the semiconductor electrode and the sensitizer dye used for the fabrication of the cell. In DSSC, the sensitizer (dye) plays a key role in absorbing sunlight and transforming solar energy into electric energy. Numerous metal complexes and organic dyes have been synthesized and utilized as sensitizers. By far, the highest efficiency of DSSC sensitized by Ru-containing compounds absorbed on Nano crystalline TiO2 reached 11–12% [3, 4]. Although such DSCC have provided a relatively high efficiency, there are several disadvantages of using noble metals in them. Noble metals are considered as resources that are limited in amount, hence they are costly. On the other hand, organic dyes are not only cheaper but have also been reported to reach efficiency as high as 9.8% [5]. However, organic dyes have often presented problems as well, such as complicated synthetic routes and low yields. Thus, alternatively an organic dye such as natural dyes suggested with similar characteristic with high absorption coefficients [6]. The good side of natural dyes is includes their easy availability, environmental friendly nature and low cost. In this paper, we report the performance of the natural dye (anthocyanin) extracted from black rice. Black rice has been selected due to its widely available in local area and low cost. EXPERIMENTAL PROCEDURE The solvent used to extract dye was prepared by using ethanol, acetic acid, and distilled water with molarity ratio about 3:2:1. The blackrice was mixed into the solvent. Then the mixture was stirred at temperature of 50°C for 30 minutes. Then the solution was filtered by filter paper, dark-red solution of anthocyanin dye was obtained. The porous film of TiO2 is prepared using the technique reported by V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 77–80 (2015)

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Wongchare et al. [7]. Commercial TiO2 nanoparticles of 0.2 g is blended using an agitate mortar with 0.4ml nitric acid solution (0.1M), 0.8g of polyethylene glycol (MW 10,000) and one drop of nonionic surfactant, Triton X-100. Blending process continued using ultrasonic bath for 30 minutes until it forms thick paste without any clots. A piece of conductive glass (ITO) is selected and placed on a metal sheet. A scotch tape at four sides was used as masking material on the conductive layer restricts the thickness and area of the paste. Then various thicknesses of TiO2 thin films are coated over ITO plate by spin coating method for various rpm rates (3000, 4000, 5000 and 6000). Later, the glass is sintered at 450°C for 2 hours under thermal furnace module. Then the sintered TiO2 thin films were immersed in natural dyes for 24 hours, allowing the natural dye molecules to be adsorbed on the surface of TiO2 nanoparticles. The DSSC photo electrode (TiO2/Anthocyanine) was ready for testing. The samples were characterized by XRD, PL and UV. Finally, The DSSCs are fabricated with platinum as a counter electrode and potassium iodide as liquid electrolyte.

RESULTS AND DISCUSSION

(2 2 1)

(2 1 1)

(3 0 1)

(1 1 0)

B d

Intensity (counts)

Intensity (counts)

d

c

b

c

b

a

a 10

20

(1 1 0)

A

(2 1 1)

Structural Characterization (XRD) Various thickness of TiO2 on FTO plate were deposited using spincoating method and it was found that the thickness of the sample decreases with increase in rpm. The XRD patterns of the samples TiO2 and TiO2/Anthocyanine for various thicknesses are shown in Figure 1A and 1B respectively. In Figure 1A, The characteristic peaks at 27° (110), 37° (3 0 1), 54° (211) and 65º (2 2 1) reveal that the formation of rutile phase of TiO2 (JCPDF card No: 73–1765) [8]. The nature of XRD peaks of the sample reflects that the nanoparticles are crystalline in nature. It is seen from Figure 1A, that the intensity of peak corresponding to (1 1 0) plane increases with decrease in thickness. After the absorption of anthocyanine dye the peak corresponding to the plane (2 2 1) vanishes and the peak corresponding to (1 1 0) decreases due to filling of pores in the TiO2 films (Figure 1B). The thickness and the XRD parameters are listed in Table 1.

30

40

50

60

70

80

10

2θ (deg)

Fig. 1

20

30

40

2θ (deg)

50

60

70

80

TiO2 Based Dye-Sensitized Solar Cell Using Natural Dyes

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Table 1: Thickness, Lattice Constant, Crystallite size of TiO2 Sample Prepared at Different rpm Rotation Per Minute

Thickness (µm)

Lattice Constant

Crystallite Size (nm)

3000

18.62

4.58

27

4000

10.18

4.57

25

5000

7.36

4.56

22

6000

4.78

4.55

21

Optical Measurements The bandgaps calculated from UV-absorption and Photoluminescence emission spectra of the samples are shown in Table 2. The bandgaps of the prepared samples (2.59 to 2.41eV) are lies in the required range of preparation of solar cells. Table 2: Bandgap Values of Anthocyanine Dye Coated TiO2 Samples from PL and UV Measurement Rotation Per Minute

Band Gap in eV PL

UV

3000

2.57

2.59

4000

2.52

2.52

5000

2.47

2.46

6000

2.41

2.41

I-V Characterization The photovoltaic tests of the prepared DSSCs using natural dye extracts as sensitizer were carried out by I-V measurements. Photocurrents and voltages were measured using a Keithley source meter 2400, with a 80 W halogen lamp and AM 1.5 G. Quality of the solar cell is determined by a parameter called solar cell efficiency that is simply defined by a ratio: P η = max PL … (1) Where, Pmax is the maximum solar cell power and PL is power of the incident light. So, solar cell efficiency and Pmax are associated by a linear dependence. The conversion efficiencies were measured and calculated, the results are summarized in Table 3. Table 3: Conversion Efficiencies of the DSSCs Prepared by Natural Dyes Conversion Efficiency (%)

Rotation Per Minute

Thickness (µm)

Fill Factor

3000

18.62

0.46

0.1238

4000

10.18

0.58

0.1299

5000

7.36

0.70

0.1981

6000

4.78

4.28

0.2646

80


CONCLUSION The synthesized nanostructured porous TiO2 samples were sensitized by anthocyanine dye. The structural characterization was done by XRD. The XRD pictures showed the features of TiO2 and the effect of anthocyanine dye (blackrice). The band gaps calculated from the UV absorption spectrum are in the range 2.41 to 2.59 eV which is in agreement with PL measurements. The band gap decreases with increase in the rotation per minute. To study the suitability of these samples for solar cell applications and sensors, the samples were optimized using UV absorption. The DSSC prepared at the ratio 6000 rpm as shown maximum efficiency of 0.26 %. REFERENCES [1] Grätzel, M., J. Photochem. Photobiol., C Photochem. Rev., 4 (2003), 145. [2] Law, M., Greene, L.E., Johnson, J.C., Saykally, R. and Yang, P., Nat. Mater. 4 (2005), 455. [3] Chiba, Y., Islam, A., Watanabe, Y., Komiya, R., Koide, N. and Han, L.Y., Jpn. J. Appl. Phys. 45 (2006), L638–L640. [4] Buscaino, R., Baiocchi, C., Barolo, C., Medana, C., Grätzel, M., Md. Nazeeruddin, K. and Viscardi, G., Inorg. Chim. Acta 361 (2008), 798–805. [5] Zhang, G., Bala, H., Cheng, Y., Shi, D., Lv, X., Yu, Q. and Wang, P., Chem. Commun. (2009) 2198–2200. [6] Hara, K., Dan-Oh, Y., Kasada, C. and Arakawa, H., Langmuir 20 (2004), pp. 4205–4210. [7] Kim, S., Lee, J.K., Kang, S.O., Ko, J.J., Yum, J.H., Fantacci, S., Angelis, F. De, DiCenso, D., Md. Nazeeruddin, K. and Grätzel, M., Journal of American Chemical Society 128 (2006), pp. 16701–16707. [8] Chakane, Sanjay; Gokarna, Anisha and Bhoraskar, S.V., J. Sensors and Actuators B 92 (2003) 1–5. [9] Hagberg, D.P., Yum, J.-H., Lee, H., Angelis, F. De, Marinado, T., Karlsson, K.M. and others, Journal of American Chemistry Society, 130 (2008), pp. 6259–6266.

Grating Influence Study of GaAs Solar Cell Structures S. Saravanan, R.S. Dubey and S. Kalainathan1 Department of Nanotechnology, Swarnandhra College of Engineering and Technology, Seetharampuram, Narsapur, A.P. 1 School of Advanced Sciences, VIT University, Vellore, T.N.

ABSTRACT Thinner solar cells are having problem of low absorption of light particularly in longer wavelength and hence, efficient light trapping engineering is dem&ed. Here, we propose a design of ultra thin GaAs solar cell with enhanced light absorption due to use of dual (dielectric and metal) gratings. In this way, light trapping can be enhanced in longer wavelength for both TE and TM polarization modes.

INTRODUCTION Presently, GaAs solar cells have shownhigh power conversion efficiency as comparison to various solar cell technologies.Among other semiconductor material, GaAs have greater optical performance such as high energy photons can be easily absorbed in short region, less power consumption, high crystal quality and operating frequency. Further, for better harvesting of light various theoretical and experimental light trapping mechanism have been reported which includes nanograting, nanoparticles and back reflectors etc. [1–3]. Hong et al. have reported a designing GaAs thin film solar cells by incorporating a periodic silver nanoparticles. They have observed enhanced absorption due to the surface plasmon induced by metal nanoparticles. GaAs based solar cell could give 31% improvement in short-circuit current as comparison to planar solar cell [4]. Nakayama et al. have experimentally demonstrated an improvement through GaAs solar cells by using silver nanoparticles fabricated by masked deposition. They have observed a strong scattering by the interacting surface plasmons and increased optical path of the incident photons which could give 8% increment in the short circuit current density [5]. Chang et al. have presented a modeling of GaAs solar cells using finite-difference time domain (FDTD) method. The fabricated device was self assembled two-dimensional microspheres and found to be efficient for light harvesting. A comparative study of designed solar cell with fabricated one could showed 25% enhanced conversion efficiency [6]. Grandidier et al. have demonstrated the designing of perfectly flat GaAs solar cell structures of various thicknesses that were comprised of a double layer antireflection coating, silica nanosphere array at the top and a back reflector. The thinner solar cell of 100 nm showed better improvement however, in case of 1000 nm cell thickness 2.5% improvement was observed after optimizing the sphere size and spacing between them [7]. Zhang et al. have presented a study of light trapping properties of GaAs nanoneedle arrays based solar cells by employing rigorous coupled wave analysis and finite element method. They have compared the nanowire arrays based solar cell with thin film layer based and observed an enhanced V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 81–84 (2015)

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light absorption. This enhancement has been attributed to the graded refractive index of nanoneedle arrays that could couple the incident light in an efficient way and also was observed to be less dependent on incident angle. With optimized solar cell structure, they observed enhanced absorption greater than 90% of above band gap [8]. In this paper, we present a modeling and simulation of GaAs solar cell based on dual grating. In section 2, designing approach with simulation details is presented and results are discussed in section 3. Finally, section 4 concludes the paper.

DESIGNING APPROACH The schematic diagram of the solar cell structure with proposed light trapping mechanism is depicted in Figure 1. This design architecture consists of 70 nm anti-reflection coating (ARC) of silicon nitride (Si3N4), top dielectric grating (height 30 nm) of indium-tin-oxide, bottom metal grating (height 30 nm) of aluminum, 40 nm GaAs active layer and 150 nm aluminum substrate.

Fig. 1: Schematic Diagram Poposed GaAs Solar Cell

The modeling of proposed structure was investigated by using finite-difference-time domain method. Periodic boundary conditions were applied in x- and y-directions while perfect matched layer condition was applied in z-direction.

RESULTS AND DISCUSSION For the comparison of absorption of proposed design of dual grating basedsolar cell (named as D), we have designed three solar cells, A: reference solar cell without grating, B: with only bottom grating&C: with only top grating. Figure 2(a) and (b) shows absorption curves of various solar cells for both TE and TM polarizations respectively. Refering to Figure 2(a), optimal enhancement in light absorption can be seen in case of dual grating based solar cell however, planar solar cell shows worse absorption. This enhanced absorption has been attributed to the scattering effect of metal and guiding effect of dielectric gratings respectively. Figure 2(b) shows absorption of various designed solar cells for TM wave. In case of reference solar cell lowest absorption can be observed while dual grating based solar cell shows optimal absorption in a broad range of wavelength. For the case of bottom grating based design, localized surface plasmon and guided modesis observed. Generally, the metallic grating structure excites localized surface plasmon resonance which

Grating Influence Study of GaAs Solar Cell Structures

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prolongs the optical path length of photons in absorber layer [1, 9]. For the case of solar cell D combined effect of dual gratings supported by plasmonic and photonic modes has been observed.

Fig. 2: Light Absorption for TE, (a) TM, (b) Cases

CONCLUSION We have investigated the optical performance of ultrathin dual grating GaAs solar cell and compared with reference solar cell. Among other designed solar cells, dual grating based solar cell could yield maximum short-circuit current density 17.41 for TE and 29.66 mA/cm2 for TM case. Finally, a relative enhanced in short-circuit current density about 101.6 and 216.7% have been obtained for TE and TM respectively. ACKNOWLEDGMENT The financial support from DRDO is acknowledged. REFERENCES [1] Chriki, Ronen; Yanai, Avner; Shappir, Joseph and Levy, Uriel, Enhanced efficiency of thin film solar cells using a shifted dual grating plasmonic structure, Opt. Express, 21/S3, A381–A391, 2013. [2] Shi, Yanpeng; Wang, Xiaodong; Liu, Wen; Yang, Tianshu; Xu, Rui and Yang, Fuhua. Multilayer silver nanoparticles for light trapping in thin film solar cells” J. Appl. Phys. 113, 176101–3, 2013. [3] Lee, Sangjun and Kim, Sangin, Optical absorption characteristic in thin a-Si film embedded between an ultrathin metal grating and a metal reflector, IEEE, 5(5), 4800610–9, 2013. [4] Hong, Lei; Rusli; Wang, Xincai; Zheng, Hongyu; He, Lining; Xu, Xiaoyan et al., Design principles for plasmonic thin film GaAs solar cells with high absorption enhancement, J.Appl.Phys.112, 054326–1–5, 2012. [5] Nakayama, Keisuke; Tanabe, Katsuaki and Atwater, Harry A., Plasmonic nanoparticle enhanced light absorption in GaAs solar cells, Appl.Phys.Lett., 93, 121904–1–3, 2008. [6] Chang, Te-Hung; Wu, Pei-Hsuan; Chen, Sheng-Hui; Chan, Chia Hua; Lee, Cheng-Chung et al., Efficiency enhancement in GaAs solar cells using self-assembled microspheres, Opt. Express, 7/9, 6519– 6524, 2009. [7] Gr&idier, Jonathan; Callahan, Dennis M.; Munday, Jeremy N. and Atwater, Harry A., Gallium Arsenide Solar Cell Absorption Enhancement Using Whispering Gallery Modes of Dielectric Nanospheres, IEEE J. Photovolt., 2/2, 123–128, 2012.

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[8] Zhang, Xu; Sun, Xiao-Hong and Jiang, Liu-Di, Absorption enhancement using nanoneedle array for solar cell, Appl Phys. Lett., 103, 211110–5, 2013). [9] Saravanan, S., Dubey, R.S., Kalainathan, S., More, M.A. and Gautam, D.K., Design and optimization of Ultrathin Crystalline Silicon Solar cells Using an Efficient Back Reflector, AIP Advances, 5, 057160–1–9, 2015.

Preparation of Hole Transporting Layer Material CuNiOnanocomposite for Organic Solar Cells Surekha Podili, D. Geetha and P.S. Ramesh1 Department of Physics, Annamalai University, Annamalai Nagar 1 Physics Wing DDE, Annamalai University, Annamalai Nagar E-mail: [email protected]

ABSTRACT The present study describes a selective transition metal oxide NiO doped CuO (CuNiO) composites were fabricated by simple co-precipitation method. Since Cu can acts as both conductor and a catalyst, the CuNiOnanocomposite exhibits higher initial coulombic efficiency than the pure CuO. The prepared nanocomposites are characterized in terms of their structural, optical and morphological properties. The detailed structural, compositional and optical characterization of nanocomposites are examined by XRD, FT-IR, and UV-Vis spectroscopy, which confirmed that the obtained nanocomposites are well crystalline CuNiO and possessed good optical properties. The CuNiOnanocomposite morphology was examined by FE-SEM/EDS which confirmed that the nanocomposite has spherical shape. The doping concentration of NiO plays an important role to get diverse morphology. The substitution of Ni on CuO resulting an increase in the hole concentration and therefore improved P-type conductivity and providing excellent conduction and chemical stability. Keywords: CuNiOnanocomposite, Hole Transporting Layer, Chemical Stability.

INTRODUCTION In report to the rising interest hygienic energy technologies, transition metal oxides have concerned special awareness for solar cells, shortcharging times and long cycle life [1]. Metal oxidenano composites with distinct morphologies have fascinated great attention because of the size, shape and surface dependent properties [2,3]. CuO an important p-type semiconductor with the band gap in the range of 1.8–2.5 eV [4] has obtained increasing interest because it has many potential applications in solar energy conversion, photocatalytic degradation of organic pollutants. Nickel oxide (NiO) is one of the most important transition metal oxides due to its applications in various fields, including the fabrication of p–n hetero junctions [5], catalysis [6], fuel cell electrodes [7], gas sensors [8], supercapacitors and battery cathodes [9]. Compared with other transition metal oxides, CuO and NiO has been received a considerable attention over the last few years due to its large surface area, high conductivity pseudocapacitive behavior. In this work, we demonstrate the preparation of CuNiO nanocomposite by simple, low cost co-precipitation route. EXPERIMENTAL Cu (NO3)26H2O, Ni (NO3)26H2O, NaOH, de-ionized water and ethanol were used as analytical grade. The CuNiOnanocomposites were prepared by co-precipitation method; in a typical synthesis, 1M of V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 85–88 (2015)

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Ni(NO3)26H2O and 1 M of Cu(NO3)26H2O were dissolved in 50 ml de-ionized water to obtain homogeneous solution, then 2 M of NaOH is added drop wise into the above solution under magnetic stirring at 80°C for 4 h, the obtained precipitate was washed with de-ionized water and ethanol for 3 times to remove unexpected ions and dried at 80°C for 5 h. The as-prepared sample was calcinated at 400°C for 6 h under air atmosphere, finally CuNiO nanocomposites were harvested XRD, FT-IR, FESEM/EDS, and UV techniques were adopted to characterize the synthesized sample.

RESULTS AND DISCUSSION The XRD patterns of CuO, NiO, CuNiO nanostructures are shown in Figure1. For CuObased diffraction peaks at 2θ value of 32.38, 35.47, 38.65, 48.67, 53.35, 58.23, 61.47, 66.12, 68.06, 72.48 and 75.13 can be indexed to the (020), (110), (002), (111), (202), (202), (113), (311), (220), (311)and (004) planes respectively (JCPDScardno.80–1268). The XRD patternindicatesmono-clinic CuO with two broad peaks around 35°(002) and 38°(111). For NiObased diffraction peaks at2θ value of 37.29, 43.30, 62.92 and 75.44 can be indexed to the (111), (200), (220), (311) and (222) planes of cubicphased NiO, respectively (JCPDS cardno.78-0643). CuO NiO (c)

Transm ittance(a.u.)

Intensity(a.u.)

(c)

(b)

(b)

(a) (a)

10

20

30

40

50

60

70

2 theta (degree)

Fig. 1: XRD Pattern of (a) CuO (b) NiO (c) CuNiO Nanostructures

80

4000

3500

3000

2500

2000

1500

1000

500

-1

Wavenumber (cm )

Fig. 2: FT-IR Spectra of (a) CuO (b) NiO (c) CuNiO Nanostructure

The XRD pattern of the final product CuNiO is shown in Figure 1(c). It can be observed that the crystal phase of the final product was the mixture of CuO and NiO. Most of the high intensity diffraction peaks can be indexed to CuO, which was well agreed with the reported values from (JCPDS: 80–1268). The residual peaks were indexed to NiO, which was consistent with the Standards card (JCPDS: 78–0643). For CuNiO based diffraction peaks at 2θ value of 35.49, 37.15, 38.68, 43.14, 48.72, 58.34, 62.78, 66.21, 68.06 and 75.26 corresponds to the (002), (111), (111), (200), (202), (202), (220), (311), (220) and (311) planes respectively. The FT-IR spectra of the CuO,NiO and CuNiO nano composites in the 4000–400 cm–1 spectral regions are shown in Figure 2. In the frequency region, the broad absorption bands observed at 3414 cm–1 for CuO, 3446 cm–1 for NiO and 3444 cm–1 for CuNiO nano composites are assigned to O–H stretching vibration of H2O [10]. The broad band around2922 cm–1 for CuO, 2927 cm–1 for NiO and 2924 cm–1 for CuNiO are assigned to the C–H stretching vibration mode. The peak at 2358 cm–1 for CuO, 2362 cm–1 for NiO and 2360 cm–1 for CuNiO nano composites are caused by –CH2 and C–CH3

Preparation of Hole Transporting Layer Material CuNiOnanocomposite for Organic Solar Cells

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stretching vibrations.The adsorbed band at 1641 cm–1 for CuO,1637 cm–1 for NiO and 1645 cm–1 for CuNiO nano composite can be assigned to O–H bending vibration of H2O. The metal oxide stretching vibrations appearing the frequencies in the range of 420 cm–1 to 850 cm–1 are associated with the vibrations of Cu–O and Ni–O [11]. The field emission scanning electron microscopy (FESEM) images ofCuNiO nano composite is shown in Figure 3(a). The morphology of the CuNiO nano composite the image indicates uniformly distributed as spherical grains, with an average diameter of ~36 nm. The nano composites are uniform and compact.

(a) FE-SEM Image

(b) EDSspectra of CuNiOnanocomposite

Element

Weight%

Atomic%

OK

34.79

66.97

Ni K

35.68

18.72

Cu K

29.52

14.31

Totals

100.00

(c) Weight % of the Elements Present

Fig. 3

The EDS pattern of the CuNiOnanocomposite is shown in Figure 3(b). The weight percentage of the elements are present in CuNiO nano composites is 29.52, 35.68 and 34.79 are corresponds to Cu, Ni and O elements are tabulated. UV-Vis spectra of CuO, NiO and CuNiO nano composites as shown in Figure 4.The absorbance onset for CuO is at about 258 nm is characteristic of the CuO nano particles. 3.5

CuNiO 3.0

NiO CuO

Absorbance

2.5

2.0

1.5

1.0

0.5

0.0 200

300

400

500

600

Wavelength(nm)

Fig. 4: UV-Vis Absorption Spectra of CuO, NiO and CuNiO Nano Structures

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For NiO, a strong absorption in the UV region is observed at wavelengths about 355 nm is characteristic of the NiO nanoparticles, while a broad absorption appears in the visible region. For CuNiO, a strong absorption in the UV region is observed at wavelengths about 301nm, while a broad absorption appears in the visible region.

CONCLUSION CuNiO nano composite have been synthesized successfully by co-precipitation method. The crystalline structure, functional groups, shapes, optical properties were characterization by XRD, FTIR, FE-SEM/EDS, and UV techniques. The synthesized CuNiOnanocomposites were found to beface centered cubic lattice as studied by XRD. The presence of functional groups and chemical bonding with Cu–O and Ni–O are conformed by FT-IR spectra.The morphology of the CuNiOnanocomposites has spherical shape with grain size of 36 nm from FE-SEM/EDS. The synthesized material has better properties and superior quality, so this material can be used as a hole transporting layer in organic solar cell in future. REFERENCES [1] Guo, P., Song, H., Chen, X., Ma, L., Wang, G. and Wang, F., Effect of graphenenanosheet addition on the electrochemical performance of anode materials for lithium-ion batteries, Anal.Chim.Acta, 688, 146–155, 2011. [2] Wang, J., Tafen, D.N., Lewis, J.P., Hong, Z., Manivannan, A., Zhi, M., et al., Origin of photocatalytic activity of nitrogen-doped TiO2nanobelts, J. Am. Chem. Soc., 131, 12290–12297, 2009. [3] Zuo, F., Wang, L., Wu, T., Zhang, Z., Borchardt, D. and Feng, P., Self-doped Ti3+enhancedphotocatalyst for hydrogen production under visible light, J. Am. Chem. Soc.,132,11856–11857, 2010. [4] Wang, Ning; He, Hongcai and Han, Lit, Room temperature preparation of cuprous oxide hollow microspheres by a facile wet-chemical approach, Applied surface science, 256, 7335–7338, 2010. [5] Chrissanthopoulos, A., Baskoutas, S., Bouropoulos, N., Dracopoulos, V., Poulopoulos, P. and Yannopoulos, S.N., Photonics and Nanostructures – Fundamentals and Applications, 2010. [6] Wei, W., Jiang, X., Lu, L., Yang, V., Wang, X., Hazard, J., Mater, nanomaterials in lithium-ion batteries and gas sensors, 168, 838, 2009. [7] Li, F., Chen, H.Y., Wang, C.M., Hu, K.S., A novel modified NiO cathode for molten carbonate fuel cells, J. Electroanal. Chem, 531, 53, 2002. [8] Hotovy, I., Huran, J., Spiess, L., Hascik, S. and Rehacek, V., Preparation of nickel oxide thin films for gas sensors applications, Sens. Actuators B: Chem., 57, 147, 1999. [9] Yao, Yu; Zhang, Jingjing; Wei, Zhen and Yu, Aishui, Hydrothemal Synthesis of Porous NiONanosheets and Application as Anode Material For Lithium Ion Batteries, Int. J. Electrochem. Sci., 7, 1433–1442, 2012. [10] Abbas, Syed Mustansar; Hussain, Syed Tajammul; Ali, Saqib; Ahmad, Nisar; Ali, Nisar; Abbas, Saghir and Ali, Zulfiqar, Modification of carbon nanotubes by CuO-doped NiOnanocompositeforuse as ananodematerialforlithium-ionbatteries, solid state chemistry, 202, 43–50, 2013. [11] Zhou, G., Wang, D.W., Yin, L.C., Li, N., Li, F., Cheng, H.M., ACS Nano6, 3214–3223, 2012.

Electrochemical Evaluation of RuO2, MnO2, (Ru:Mn)O2 Composite Thin Film Electrodes P.S. Joshi, S.D. Gothe1, S.G. Madale2 and D.S. Sutrave2 Walchand Institute of Technology, Solapur, Maharashtra 1 Sangameshwar College, Solapur, Maharashtra 2 D.B.F. Dayanand College of Arts and Science, Solapur, Maharashtra

ABSTRACT Ruthenium oxide, Manganese oxide and (Ru:Mn)O2composite thin films have been prepared by 0.02M Ruthenium chloride and Manganese acetate solutions respectively by sol-gel spin coating technique on SS substrates. The thin films have been studied with respect to different characterizations such as X-ray diffraction, SEM, Cyclic voltammetry, Chronopotentiometry, Electrochemical Impedance Spectroscopy and Stability. (Ru:Mn)O2 composite thin films have been demonstrated to be an excellent material for Supercapacitor application when evaluated with RuO2 and MnO2 thin film electrodes. As a result, high specific capacitance of 515 F/g at 10 mV/s with excellent stability and long cycle life was obtained, where specific power andenergy were as high as 65 Wh/kg and 45 KW/kg respectively with loading weight of 0.13 mg/cm2. Composite films showed changes in structural and morphological features which was admiring for supercapacitor applications. The electrochemical impedance measurement was carried out in 0.1 M KOH in the frequency range 10 to 105 Hz. From the analysis it can be concluded that mixed oxide composites have superior capacitive performance to single transition metal oxides as electrodes. Keywords: (Ru:Mn)O2 Composite Thin Films, Cyclic Voltammetry, Chronopotentiometry, Electrochemical Impedance Spectroscopy.

INTRODUCTION Supercapacitors, also known as electrochemical capacitors or ultracapacitors, are an energy storage devices have received much attention[1]as they store up charge electrostatically through the charge accumulation at the electrode/electrolyte interface, therefore strongly dependent on the surface area of the electrode accessible to the electrolyte. There are two electrode materials that are used to store charge –conducting polymers and metal oxides [2]. The most of relevant research concerns ruthenium oxide among various metal oxides. This is because other metal oxides have yet to obtain comparable capacitances. However, the high cost of this noble metal material limits its further commercial applications.Also owing to the potential applications in supercapacitors requiring both high energy and high power densities, composites of metal oxides perform better than single transition metal oxides when used as electrode in a supercapacitor [3]. Manganese oxides have a variety of advantages such as low cost, abundance, environmentally friendly nature coupled with excellent electrochemical properties [4]. So here efforts are made to reduce the quantity of ruthenium oxide by sol-gel spin coating technique and cost by using manganese oxide for synthesis of composite films. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 89–94 (2015)

90


EXPERIMENTAL Analytical grade chemicals were used for the work.Firstly, 0⋅02M Ruthenium trichloride solution was prepared in double distilled water. Isopropyl alcohol was added then the solution was continuously and thoroughly stirred for 3 hours by magnetic stirrer. The gel was formed after aging the solution for 24 hrs. at room temperature. After that deposition was taken on cleaned SS substrates in spin coater unit at a speed of 3000 rpm. Then after calcinations at 900°C,uniform thin films of RuO2 were formed. The procedure was repeated for multiple coats. Same procedure was repeated by using 0.02 M Mn Acetate solution for deposition of MnO2. Layer-by layer spin deposition is done for deposition of composite (Ru:Mn)O2thin films. First two layers of RuO2 and then two layers of MnO2 were deposited. All the films studied here were of 4 coats. RESULTS AND DISCUSSIONS Structural Properties The X-ray diffraction pattern of as deposited RuO2, MnO2, (Ru:Mn)O2thin films recorded using a Xray diffractometer D2 PHASER using CuKα radiation (λ = 1.54 A°) is shown in Figure 1. The experimental data showed that tetragonal structure of RuO2 film (JCPDS Card No.-88–0322) corresponding to Miller Indices [111] and [211] and orthorhombic structure of MnO2 film (JCPDS Card No.-82–2169) corresponding to Miller indices [410], [401], [520].

Fig. 1: X-ray Diffractogram of RuO2,MnO2, (Ru: Mn)O2 Thin Films

For (Ru:Mn)O2 films, the peaks for MnO2 as well as RuO2 has been observed but with decreased intensity. Also for composite films it was observed that there is a shift in angle 2θ for every peak.Intensity change means adsorption on surface while change in theta indicates inter-layer change.

Morphological Properties As the electrochemical performance of electrodes is strongly influenced byparticle size, microstructure and porosity, the films were studied by SEM. Morphology of the RuO2 films of SS

Electrochemical Evaluation of RuO2, MnO2, (Ru:Mn)O2 Composite Thin Film Electrodes

91

substrates was examined by SEM JEOLJSM 6360. The RuO2 thin films showed porous, mud-cracked morphology giving rise to high surface roughness.The MnO2 films showed non-uniformly distributed well developed grains with porosity. The (Ru:Mn)O2composite films showed relatively high porous morphology which is suitable for supercapacitor application.

Fig. 2: SEM Images of (a) RuO2 (b) MnO2 (c) Ru: Mn)O2 Thin Films

Electrochemical Properties As deposited films were used as electrodes so cyclic voltammetry and chronopotentiometry, EIS analysis were done by a electrochemical workstation CH Instruments CH1608E in 0.1 M KOH electrolyte solution in a three –electrode cell employing Pt auxiliary electrode and a SCE reference electrode. For electrochemical analysis in cyclic voltammetry the electrode potential was varied between –1.4 V to 0.8 V in both cathodic and anodic directions and current response was measured. A large magnitude of current, a rectangular type of voltammogram with redox transition peaks showing occurrence of the Faradaic reactions are the indications of ideal capacitive nature of any material. Figure 3.(A) C-V of ruthenium oxide, Manganese oxide and composite thin film electrode at 100 mV/Sec scan rate in 0.1 M KOH electrolyte illustrates the similar nature. In addition, the capacitive current density tends to increase in the order MnO2< RuO2< (Ru:Mn)O2.Meanwhile, the maximum values of the specific capacitance for RuO2, MnO2 and (Ru: Mn)O2 thin films atcurrent densities of 4.5, 3.7 and 7 mA/cm2 using a scan rate of 10 mV/s are 310, 172, and 515 F/g respectively. Figure 3

92


(B). shows the increase in specific capacitance for composite films as compared to individual oxide thin films for different scan rates.

(a) (b) Fig. 3: Cyclic Voltammograms of (a) RuO2(b) MnO2 (c) (Ru: Mn) O2 Thin Films, (b) Specific Capacitance of (a) RuO2 (b) MnO2 (c) (Ru: Mn)O2 thin Films as a Function of Scan Rate

Moreover the specific capacitance decreased as the scan rate increased. This activity can be attributed to the high possibility of revealing both inner and outer surface of the deposited oxide to the ions with the decrease in the scan rate [5]. The charge–discharge behavior of the film was examined by chronopotentiometry [6]. Figure 4 shows the charge/discharge behavior for RuO2, MnO2 and (Ru:Mn)O2 thin film electrodes. The linear and symmetric charge/discharge curves indicate good capacitive behavior.

(a) (b) (c) Fig. 4: Charge–Discharge Curve for (a) RuO2,(b) MnO2 and (c) (Ru:Mn)O2 Electrodes at a Constant Current Density of 2 mAcm–2, within a Potential Range of -1–1 V vs. SCE in 0.1M KOH Solution

Specific energy and Specific Power was calculated and it was observed that for (Ru:Mn)O2 electrodes both energy (45 Wh/kg) and power (65 KW/kg)with coulombic efficiency 83.33% obtained were higher than single oxide electrodes. Electrochemical impedance spectroscopy has been widely used to study the redox (charging/discharging) processes of electrode materials. Figure 7(a) shows the 1–105 Hz Nyquist plot for the RuO2, MnO2 and (Ru: Mn)O2 thin films. All the plots in the high

Electrochemical Evaluation of RuO2, MnO2, (Ru:Mn)O2 Composite Thin Film Electrodes

93

frequency region only show a quarter-distorted circle which is related to interfacial processes. In the low frequency region, the Nyquist diagram showed a slope line, but not so straight, which is related to that of the Warburg impedance corresponding to porous nature and a capacitive behavior related to the film charging mechanism [7]. The charge transfer resistance (Rct) [8] decreased for (Ru:Mn) O2 indicates that the enhancement in pseudocapacitive characteristics is mainly due to an improvement in the electronic properties of the composite films.

Fig. 4: Nyquist Plots for (a) RuO2,(b) MnO2 and (c) (Ru:Mn)O2 Electrodes

CONCLUSIONS In an attempt to develop a electrode with low cost, high capacitive performance and long cyclic stability, (Ru:Mn)O2 thin films were deposited by sol-gel spin coating method on SS electrodes. The obtained composite oxide films were porous and cracked according to the SEM results. The XRD showed peaks of both RuO2 and MnO2. In electrochemical analysis, it showed maximum capacitance of 515 F/g at 10 mV/Sec scan rate. From the shaped variation of CV curve and variation of the EIS plots, a process of electrochemical activation is suggested. It can be concluded that mixed oxide composites have superior capacitive performance to single transition metal oxides as electrodes. ACKNOWLEDMENTS The Authors wish to acknowledge the U.G.C, New Delhi for financial support through the Major Research Project F No. 42–123/2013(SR). REFERENCES [1] Zhao, D., Yang, Z., Kong, E.S., Xu, C. and Zhang, Y., J. Solid State Electrochem. DOI 10.1007/s10008010-1182-x. [2] Conway, B.E., Birss, V. and Wojtowicz, J., Journal of Power Sources, Vol. 66, No. 1–2, pp. 1–14, 1997. [3] Hwang, S., Ryu, S., Yun, S., Ko, J., Kim, K. and Ryu, K., Materials Chemistry and physics, 130 (2011) 507–512] [4] Toupin, M., Brousse, T. and Belanger, D., Chem. Mater, 14 (2002), 3946.

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[5] Zhang, Y., Li, G., Lv, Y., Wang, L., Zhang, A., Song, Y. and Huang, B., International Journal of Hydrogen Energy, Vol. 36, pp. II760–II766, 2011. [6] Nagarajan, N., Humadi, H. and Zhitomirsky, I., Electrochim. Acta 51 (15), (2006), 3039–3045. [7] Zhang, Y., Li, G., Lv, Y., Wang, L., Zhang, A., Song, Y. and Huang, B., International Journal of Hydrogen Energy, Vol. 36, pp. II760–II766, 2011. [8] Tuken, T., Yazici, B. and Erbil, M., Prog. Org. Coat., Vol. 50, pp. 115–122, 2004.

Comparative Study of MnO2, Co3O4 and MnO2: Co3O4 Stacked Thin Film Electrodes for Super Capacitor S.S. Dattatraya, M.J. Sangeeta and S.G. Sagar D.B.F. Dayanand College of Arts and Science, Solapur, Maharashtra

ABSTRACT In the present work, MnO2, Co3O4 and MnO2:Co3O4 stackedthin filmswere prepared by Sol-gel spin coat method with Manganese acetate and Cobalt acetate as precursors. The XRD patterns showed crystalline behaviour with orthorhombic and cubic phase for MnO2 and Co3O4 respectively. MnO2:Co3O4 stacked film showed dominating peaks of both oxides with two new peaks of MnO2 and small shift in angle 2θ affecting lattice constants. The SEM images revealed the formation of well adherent and porous structure of grains. From electrochemical analysis it is found that, the MnO2, Co3O4 and MnO2:Co3O4 stacked films showed maximum specific capacitance of 440 F/g, 530 F/g and 600 F/g respectively at 10 mV/s scan rate, specific energy 20.13 Wh/kg, 72.22 Wh/kg and 141.66 Wh/kg respectively and specific power 29.00 KW/kg, 52.00 KW/kg, 68.00 KW/kg respectively. Furthermore 75% stability is retained after 1000 cycles exhibiting good cyclic stability and long cycle life. These results suggest that, MnO2:Co3O4 stacked thin film can be a good electrode material for supercapacitor. Keywords: Sol-gel, MnO2, Co3O4, Stacked Oxide, Specific Capacitance.

INTRODUCTION The properties of nanocomposite films depend not only upon the individual components used but also on the morphology and the interfacial characteristics. Recently, various nanocomposite films consisting of either metal-metal oxide, mixed metal oxides, polymers mixed with metals or metal oxides, or carbon nanotubes mixed with polymers, metals or metal oxides have been synthesized and investigated for their application as active materials for supercapacitors. Design of the nanocomposite films for such applications needs the considerations of many factors, for example, the surface area, interfacial characteristics, electrical conductivity, nanocrystallite size, surface and interfacial energy, etc., all of which depend significantly on the material selection, deposition methods and deposition process parameters. Materials can be deposited in the form of thin film on asubstrate by a variety of methods such as physical vapour deposition, chemical vapourdeposition, wet-chemical processes such as sol-gel and electrochemical deposition and spray pyrolysis etc. [1]. It is believed that transition metal oxides are good candidates as electrode materials, because they have variation in oxide states which is suitable for effective redox charge transfer [2,3]. Non-noble oxides such as NiO, Co3O4, MnO2 are very promising candidates for electrode materials in supercapacitors [4–5]. However, the relatively low specific capacitance needs to be improved for supercapacitor application. Recent research is focused on increasing the specific capacitance of the oxides by introducing other oxides technology [6–7]. In this study, MnO2, Co3O4 and V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 95–100 (2015)

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MnO2:Co3O4stacked oxides as electrode materials were prepared by Sol-gel spin coat method.

EXPERIMENTAL Sol-gel Preparation and Deposition At first 0.02 M solution of cobalt acetate [(CH3COO)2Co.4H2O] and manganese acetate [C4H6MnO4.4H2O] were prepared in a double distilled water and isopropyl alcohol. The prepared solution was stirred for 4 hours and then aged for 48 hours to get viscous solution. Then resultantsolgel is spin coated on steel substrate to obtain thin film electrodes. Before deposition substrateds were scrubbed with zero grade polish paper and cleaned in ultrasonic bath for 15 minutes. RESULT AND DISCUSSION Structural Analysis by XRD Structural analysis was carried out by D2 PHASER diffractometer with steps one degree per minute using source CuKα1 with λ =1.54184 A°. The 2θ angle is varied from 10° to 90°.The Figure 1 shows the XRD pattern for MnO2,Co3O4andMnO2:Co3O4stacked oxide thin films. XRD pattern exhibited crystalline nature with orthorhombic [8] and cubic phase [9] for MnO2 and Co3O4 films respectively. The XRD pattern of MnO2:Co3O4stacked film shows dominating peaks of both oxides and two new peaks of MnO2. It also showed small shift in angle 2θ hence shifting the lattice constants. The details of lattice constants are given table.1. The lattice mismatch between pure and stacked films indicate significant variations occurred on the structure and properties of stacked thin film. 16000 ss 14000 [410]

ss

12000

ss ss

MnO2 [412]

[520]

[401]

8000

[411]

[120]

10000

14000 ss

ss ss ss

Co3O4 ss

6000 4000 16000 ss

14000

[620]

[422]

8000

[444]

10000

[400]

12000

[400] Co

Intensity (arb.unit)

6000

6000 10

20

30

40

50

60

[444] Co

[331] Mn [002] Mn

8000

MnO2: Co3O4 [422] Co

ss ss

10000

[120] Mn [410] Mn

12000

70

80

90

Angle 2 Theta (degree)

Fig. 1: XRD Patterns of MnO2,Co3O4 and MnO2:Co3O4 Stacked Oxide Thin Films

Comparative Study of MnO2, Co3O4 and MnO2

97

Table 2: Observed Shift in Lattice Parameters for Stacked Film Compared to Pure Films Film

Lattice Constant ‘a’ Observed

MnO2

9.363

MnO2:Co3O4

8.880

Co3O4

8.144

MnO2:Co3O4

8.068

Standard

Lattice Constant ‘b’ Observed

Standard

4.494 9.323 8.085

Lattice Constant ‘c’ Observed

Standard

2.855

4.332

4.453

2.841

2.848

–

–

–

–

Surface Morphology The morphological features of the samples were investigated by Scanning Electron Microscopy (SEM) using a JEOL JSM-6360 instrument.

Fig. 2: SEM Micrographs of (a) MnO2, (b) Co3O4 and (c) MnO2:Co3O4 Stacked Oxide Thin Films

From the SEM analysis it has been observed that the grain structure of both MnO2 and Co3O4 films is tetragonal with smooth, well adherent and porous surface. As shown in Figure 2(a) and (b) MnO2 and Co3O4 thin films possess large grains uniformly distributed throughout the film surface, the average grain size calculated from the SEM images are around 500nm and 600nm respectively. From Figure 2(c), it is observed that, the grains are more equated with continuous grain boundary with decreased grain size in the range 250 nm, this indicates MnO2:Co3O4 stacked thin film exhibit enhanced pore density and grain density which is major requirement in supercarpacitor.

Electrochemical Analysis Cyclic Voltammetry The CV measurements were performed with MnO2, Co3O4 and MnO2:Co3O4stacked thin films as working electrodes and platinum wire as counter electrode and SCE as a reference electrode in 0.1 M KOH electrolyte. Figure 3 shows the cyclic voltammograms for all films, with varying potential windows such as 0.7V to –1V, 0.75V to –1.25V and 0.65V to –1.3V respectively at various scan rates 10, 20, 40, 60, 80 and 100mV/sec. From CV analysis, MnO2, Co3O4 and MnO2:Co3O4stacked films showed maximum specific capacitance of 440 F/g, 530 F/g and 600 F/g respectively at 10mV/s scan rate.

98


Fig. 3: Cyclic Voltammograms of (a) MnO2, (b) Co3O4 and (c) MnO2:Co3O4 Stacked Electrodes

All electrodes showed a common trend of decreasing specific capacitance values against increasing scan rate. Despite this common trend, the MnO2:Co3O4stacked electrode displays higher specific capacitance values throughout the whole scan region, clearly indicating its superiority over the pure electrodes [10]. Cyclic Stability Since theMnO2:Co3O4stacked film gave the highest capacitance, we investigated the stability of the film for longer votammograms upto 1000 cycles at the scan rate of 500mVs–1 in 0.1M KOH electrolyte lasting about 3hour, is shown in Figure 4. The 75% stability is retained after 1000th cycle, the value of specific capacitance is decreased by a comparably small amount which may be due to detatchment during early charging/discharging cycles in the electrolyte. [11]

Fig. 4: CV Curves of MnO2:Co3O4 Stacked Electrodes At 500 mv/s scan rate.

Comparative Study of MnO2, Co3O4 and MnO2

99

Chronopotentiometry Typical charging and discharging curves for MnO2, Co3O4 and MnO2:Co3O4 stacked electrodes were measured between the voltage range of –1 to 1V at a current density of 1, 2 and 3 mA cm2respectively in 0.1 M KOH electrolyte as shown in Figure 5. It is observed that charging-discharging time are almost same but there is a difference in potential range, the maximum potential is observed for MnO2:Co3O4 stacked oxide thin film. From CP, the supercapacitive parameters such as specific energy, specific power and coulombic efficiency were calculated. MnO2, Co3O4 and MnO2:Co3O4 stacked films exhibited specific energy 29.13 Wh/kg, 72.22 Wh/kg, 141.66 Wh/kg respectively and specific power 20KW/kg, 52.00 KW/kg, 68.00 KW/kg respectively. The columbic efficiency for all the electrodes was fond to be 100%.

Fig. 5: Charge-Discharge Curves of MnO2, Co3O4 and MnO2:Co3O4 Stacked Oxide Electrodes

CONCLUSION This study shows successful synthesis of MnO2,Co3O4 and MnO2:Co3O4stacked oxide thin films as confirmed by the different characterizations such as XRD, SEM, CV, Stability and Chronopotentiometry. XRD revealed the formation of metal oxides which are crystalline in nature, the XRD pattern of stacked film include dominating peaks of both metal oxides. The lattice mismatch between pure and stacked films indicate significant variations occurred on the structures and properties of stacked thin film to some extent. The SEM images clearly indicated the enhanced porous nature of MnO2:Co3O4stacked oxide as compared to pure thin films. Cyclic Voltammetry, and Charge-discharge techniques revealed that MnO2:Co3O4stacked oxide electrode exhibited good electrochemical behaviour. It has been also observed that value of specific capacitance is more for stacked electrode as compared to pure electrodes. ACKNOWLEDGEMENT Authors wish to acknowledge the U.G.C, New Delhi for financial support through the Major Research, Project F No. 42–123/2013(SR).

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REFERENCES [1] Yang, Dongfang, Industrial Materials Institute, National Research Council Canada, www. intechopen.com [2] Shukla, A.K., Sampath, S. and Vijayamohanan, K., Current Science, 2000, 79, 1656. [3] Hall, P.J., Mirzaeian, M., Fletcher, S.I., Sillars, F.B., Rennie, A.J.R., Shitta-Bey, G.O., G, Energy and Environmental Science, 2010, 3, 1238. [4] Srinivasan, V. and Weidner, J.W., J Electrochem Soc, 2000, 147, 880. [5] Meng-qiang, W.U., Jia-hui, Shu-ren, et al., J Power Sources, 2006, 159:365. [6] Yong, W., Xiao, Z., J. Electrochimica Acta, 2004, 49: 1957−1962. [7] Kuo, S.L., Lee, J.F. and Wu, N.L., J Electrochem Soc, 2007, 154: A34−A38. [8] JCPDS card No. 82–2169. [9] JCPDS card No. 78–1969. [10] Chen, W.C., Wen, T.C. and Teng, H., Electrochim. Acta, 48 (2003), 641. [11] Rafik, F., Guolous, H., Gallay, R., Crausaz, A. and Berthon, A., J. Power Source, 165 (2007), 928.

Effect of Calcium Oxide Nanoparticles on the Performance of Polyethersulfone Ultrafiltration Membranes K. Rambabu and S. Velu Chemical Engineering Division, SMBS, VIT University, Vellore E-mail: [email protected]

INTRODUCTION Ultrafiltration (UF) is one of the most widely used technologies for macromolecules separation from solutions especially for industrial effluent treatment. The basic principles of ultrafiltration along with its salient features have been extensively reported in literature [1,2]. Polyethersulfone (PES) is one of the best polymers for UF membrane synthesis especially for wastewater treatment [1,2]. However, pure PES membranes suffer from the limitation of very low fluxes and membrane fouling. To overcome this limitation, the PES polymer is blended with several modifiers to produce membranes with enhanced ultrafiltration properties [3,4]. Recently, calcium salts has been successfully blended with other polymeric membranes resulting in the enhanced features of the respective base membrane [5,6]. In this current study, a series of UF membrane with PES as base polymer and calcium oxide nanoparticles (CON) as modifier have been synthesized in varying compositions. The prepared membranes were subjected to morphological studies, UF characterization, dye rejection and fouling analysis. The obtained results and their inference are discussed. EXPERIMENTAL PROCEDURE PES based asymmetric UF membranes are predominately prepared by phase inversion method. Standard procedure of phase inversion method for membrane preparation as described in literature [1,3], was adopted for the membrane synthesis. The cast solution composition for the various membrane blends preparation is shown in Table 1. Scanning electron microscopy (SEM) was used to analyze the morphology of the blend membranes through standard morphology study procedure. Surface roughness of all the prepared membranes was estimated through Atomic force microscopy (AFM). Structural analysis of all the prepared membranes was carried out through x-ray diffraction (XRD) patterns and fourier transform infrared (FTIR) spectroscopic studies. Surface hydrophilicity in terms of contact angle was measured using Goniometer. Pure water flux, measured at a transmembrane pressure of 414 kPa, was determined using the Eq. (1). Jw = [Q/(A ΔT)] … (1) –2 –1 2 where, Jw is permeate flux (lit m h ), Q is quantity of permeate (lit); A is membrane area (m ), ΔT is sampling time (h). Porosity (ε) and average pore radius (rm) for all the membrane samples were estimated by water uptake test and by using Eq. (2) and Eq. (3) respectively. ε=

Ww − Wd × 100 ρ wVm


… (2)

102


where, Ww (kg) and Wd (kg) are the wet and dry weight of the membrane sample, V (m3) is membrane volume and ρw (kg m–3) is water density.

rm =

(2.9 − 1.75 ε) × 8ηwlq ε × A × ΔP

… (3)

where, ηw is the dynamic viscosity of water (Pa s) at 30 °C, ‘l’ is the membrane thickness (m), q is the volume of the water permeated per unit time (m3 s-1), A is the effective area of the membrane (m2), and ΔP is the transmembrane pressure (Pa). Dye rejection test was carried out at an operating pressure of 414 kPa and the solute rejection percentage was calculated using Eq. (4). %SR = [1–(Cp/Cf)] × 100

… (4)

where, Cp and Cf are metal ion concentrations of permeate stream and feed stream, respectively. Fouling analysis for all membranes samples was carried out by estimating the flux recovery ratio (FRR) of the membranes using Eq. (5). Congo red (CR) dye solution was used as the standard test sample for all the membranes to carry out the fouling study. FRR = (Jw / Jw2) × 100 –2

… (5)

–1

where, Jw2 (lit m h ) is the pure water flux obtained through the membrane after the CR dye solution permeation through the membrane for a period of 3 hours.

RESULTS AND DISCUSSIONS SEM studies on PES – CON blend membranes revealed the modified pore characteristics of the blend membranes in comparison to pure PES membrane. As shown in Figure 1, it could be seen that the number of pores as well as the pore size got increased with the CON addition to the PES matrix, ensuring the chances of better flux for the blend membranes.

(a)

(b)

(c)

Fig. 1: SEM Images of Pure and Blend Membranes (a) Pure PES (b) PES – CON (1 wt%) (c) PES – CON (3 wt%)

As shown in Table 1, AFM results clearly indicated that the roughness of the prepared membranes was increased with the CON addition. Moderate increase in the surface roughness ensures the chances of better flux and antifouling nature of the CON blend membranes. XRD and FTIR structural analysis confirmed the uniform dispersion of the added CON in the PES matrix. UF characterization results for the prepared membranes are presented in Table 1. Surface hydrophilicity of the membrane was measured in terms of contact angle. It was observed that the

Effect of Calcium Oxide Nanoparticles on the Performance of Polyethersulfone Ultrafiltration Membranes

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water contact angle on the membrane sample was decreasing with increase in CON concentration, revealing the enhanced hydrophilicity due to modifier addition. Porosity measurements through the water uptake test clearly showed the enhanced porosity in the composite membrane with the raise in CON concentration. Average pore radius estimation showed that the pore size was almost same till a cutoff concentration of 1 wt% CON in the blend membrane after which there was appreciable increase in the pore size. Thus the results of porosity and average pore size measurements were in accordance with the results obtained through SEM analysis. Pure water flux measurements clearly exhibited the superiority of the blend membranes over the pristine PES membrane. As shown in Figure 2, the water flux was increased to a maximum of four times in the blend membrane with increase in CON concentration in the blend membranes. From above characterization results, it was very clear that addition of CON modifier to PES membrane has boosted the UF characteristics of the blend membrane as compared to the pure PES membrane. Table 1: UF Surface roughness and characterization results for the pure and blended membranes Membrane ID M0 M1 M2 M3 M4

Membrane Composition (weight %) Solvent PES CON (DMF) 18 0 82 18 1 81 18 2 80 18 3 79 18 4 78

Surface Roughness, Ra (nm) 13.95 17.75 39.65 71.25 124.85

Fig. 2: Pure Water Flux of Prepared Membranes

Contact Angle (°)

Porosity, ε (%)

65.5 60 56.5 49 42

25.27 27.05 59.49 94.12 159.13

Average Pore radius, rm (nm) 13.6 20.4 28.5 32.5 33.2

FRR (%) 37.2 54.3 49.7 44.5 41.4

Fig. 3: Results of Dye Rejection Studies

Performance analysis of the pure and blend membranes were examined by subjecting the membranes for dye rejection test. The obtained results of the rejection studies are shown in Figure 3. Results of performance tests showed that the blend membranes had an increased flux with a better dye rejection percentage as compared to that of the performance of pure PES membrane. Also the rejection tests indicated that steric hindrance and adsorption were predominant separation principles for the blend membranes. Fouling resistance of the prepared membranes was measured in terms of FRR. A high value of FRR denotes a strong resistance towards membrane fouling [7]. As shown in table 1, it was clearly seen that all the CON blend membranes had a better fouling resistance than the pure PES membrane.

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High FRR values could be attributed to the minimal pore size and enhanced hydrophilicity of the membrane. Thus, the FRR analysis indicated the enhanced antifouling nature of the CON blend membranes, especially for the 1 wt% CON membrane. Analyzing the results of the membrane characterizations, dye rejections and fouling studies, it was clear that the 1 wt% CON composite membrane was possessing better separation and antifouling properties in comparison with the other synthesized membranes.

CONCLUSIONS A novel series of polyethersulfone (PES) blended with calcium oxide nanoparticles (CON) ultrafiltration membrane was synthesized in varying compositions and subjected to membrane characterization analysis. Results indicated enhanced pores statistics, surface roughness, water permeability and hydrophilicity with increase in CON concentration in the membrane composition. Dye rejection performance test on the prepared membranes clearly indicated that the CON blend membranes reported improved rejection efficiency as compared with pristine PES membrane. Fouling analysis indicated that the CON blend membranes were more fouling resistant than the unmodified PES membrane. A very close analysis on the obtained results revealed the better performance characteristics of 1 wt% CON membrane among the synthesized series of the composite PES membranes. Thus the calcium oxide nanoparticles blended polyethersulfone composite membrane seems to be a promising candidate for treatment of dye polluted waste water, ensuring high fluxes and elevated rejection rates. ABBREVIATIONS AND NOMENCLATURE SEM - Scanning electron microscopy; AFM - Atomic force microscopy; XRD - X-ray Diffraction; FTIR - Fourier transform infrared spectroscopy; wt% - Weight percentage; Ra - Surface roughness average; ε - Membrane porosity; Wd -Weight of dry membrane; Ww - Weight of wet membrane; ρw Density of water; Vm - Volume of membrane; A -Membrane surface area; l -Membrane thickness; ηw Dynamic viscosity of water; q - Volume of the water permeated per unit time; ΔP - Transmembrane pressure; Jw - Pure water flux; Q - Permeate quantity; ΔT - Sampling time; % SR - Percentage solute rejection; Cp - Solute (Dye) concentration in the permeate; Cf - Solute (Dye) concentration in the feed. REFERENCES [1] Cheryan, M., Ultrafiltration and microfiltration handbook, CRC press, Florida, 1998. [2] Crull, A., Membranes for the Nineties: Highlighting Surface Modification Technology, Business Communications Co., Nonvalk, CT, 1990. [3] Ahmad, A.L., Abdulkarim, A.A., Ooi, B.S. and Ismail, S., Recent development in additives modifications of polyethersulfone membrane for flux enhancement. Chem. Eng. J., 223 (2013) 246–267. [4] Lau, W.J. and Ismail, A.F., Polymeric nanofiltration membranes for textile dye wastewater treatment: preparation, performance evaluation, transport modeling, and fouling control—A review, Desalination 245 (2009), 321–348. [5] Chen, X.N., Wan, L.S., Wu, Q.Y., Zhi, S.H. and Xu, Z.K., Mineralized polyacrylonitrile-based ultrafiltration membranes with improved water flux and rejection towards dye, J. Membr. Sci., 441 (2013), 112–119. [6] Zhi, S.H., Wan, L.S. and Xu, Z.K., Poly (vinylidene fluoride)/poly (acrylic acid)/calcium carbonate composite membranes via mineralization, J. Membr. Sci., 454 (2014) 144–154. [7] Rahimpour, A., Madaeni, S.S., Jahanshahi, M., Mansourpanah, Y. and Mortazavian, N., Development of high performance nano-porous polyethersulfone ultrafiltration membranes with hydrophilic surface and superior antifouling properties, Appl. Surf. Sci., 255 (2009), 9166–9173.

Prediction on Flashover Voltage of Bamboo Leaf Ash Blended Ceramic Electrical Insulator M. Shanmugam, G. Sivakumar1 and S. Barathan Department of Physics, Annamalai University, Annamalainagar, Tamil Nadu Centralized Instrumentation and Service Laboratory, Annamalai University, Chidambaram, Tamil Nadu E-mail: [email protected]

1

ABSTRACT Ceramic insulators are widely used in electrical applications such as power transmission and distribution network. In the fabrication of ceramic electrical insulator partial replacement of quartz by bamboo leaf ash by an industrial route. The overall goal of this work is to utilize waste material in the ceramic formulation and enhances the physical properties such as bulk density, water absorption, porosity, shrinkage. The mechanical strength values of the control and 5% bamboo leaf ash blended specimens about 2.48 and 3.12 MPa. This result confirms that the BLA waste act as a filler in a blended ceramic insulator. The surface feature of the specimen was analyzed through Scanning Electron Microscopy (SEM). Quartz phase and mullite formation were determined by X-ray diffraction (XRD). The electrical insulating property of the fabricated blended ceramic insulator was safe for use with a maximum of 5000V evaluated. Dielectric breakdown strength is correlated with the flashover voltage. Thus, BLA waste is a suitable material for the production of ceramic electrical insulator. Keywords: Bamboo Leaf Ash, Ceramic Electrical Insulator, SEM, XRD, Flashover.

INTRODUCTION Triaxial porcelain forms a large base of the commonly used ceramics for both low and high tension insulation. It is considered to be one of the most complex ceramic materials and most widely studied in the raw materials, processing science, phase and microstructure evolution. These materials are ceramics and generally composed of clay [Al2Si2O5 (OH) 4], give plasticity to the ceramic mixture; flint or quartz (SiO2), maintains the shape of the formed article during firing; and feldspar [KxNa1–x (AlSi3) O8] [1]. Bamboo leaves is one of the forest waste materials obtained as large amounts of solid waste, it is disposed mainly by burring. Reuse of this kind of solid waste has many advantages, not least of which are the economic advantages, including job creation in companies specializing in the selection and recycling of this kind of material [2]. Utilization ofthis waste material such as bamboo leaf ash isapplicable to ceramic product formation. Replacement of quartz by bamboo leaf ash is to develop the attention in blended ceramic electrical insulator fabrication. High voltage outdoor insulators used in transmission lines and substation are being subjected to various operating conditions and environments. Contamination on the surface of insulators enhances the leakage current that develops which may lead to flashover and power system outage and it is the essential element in power system [3]. Electrical insulators are used to insulate electrical wires and cables from points of support.The overall goal of this work is to utilize this (BLA) waste material in ceramic formulation by the replacement of and to estimate the potentials of materials for the fabricationof ceramic electrical insulator. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 105–110 (2015)

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EXPERIMENTAL Raw Materials An industrial ceramic ingredient such as clay, feldspar and quartz were purchased from M/s Oriental Ceramic Industry, Viruthachalam, Tamil Nadu. The bamboo leaves were collected from the campus of the Annamalai University, Chidambaram, Tamil Nadu. Dry bamboo leaves were open fired and to complete combustion. The obtained ash was cleaned, dried in air for 12 h consequently, and then the ash calcined at 650 °C for 3 h at a heating rate of 300°C/h in an electric furnace. The organic compounds are decomposed at 500°C and large amount of crystalline silica was obtained at 650°C [4]. The chemical composition of the calcined ash (BLA) was determined by X-ray fluorescence and its results are given in Table 1. Table 1: Composition of the Materials (wt %) Composition

SiO2

Quartz

97.55

0.97

BLA

79.90

2.78

Al2O3

K2O

Fe2O3

Na2O

TiO2

CaO

MgO

Others

0.41

0.27

0.35

0.04

0.23

0.08

0.10

3.98

0.86

0.20

0.38

7.84

1.97

2.09

Insulator Fabrication Standard ceramic electrical insulator specimen (SC) was prepared using an industrial standard ceramic material (wt%) such as clay 60%, feldspar 25% and quartz 15%. Partial replacement of quartz by calcined 5wt % bamboo leaf ash (BLA) for the fabrication of blended ceramic electrical insulator (QB). Each composition (SC and QB) was milled and water was added to the homogenous mixture separately. Then the slurry was milled for 12 h using ball milling and slip (slurry) was filter pressed using pressing machine. The moisture content of ceramic electrical insulator is about 4–6% are normal and dried for 48 hours and shaping the insulator to attain smooth surface. The dried ceramic electrical insulator (green insulator) was sintered at 1250°C in a kiln and the sintered insulator are allowed to quality assessment test. Characterization Physical properties such as bulk density, porosity and water absorption of the sintered specimens were determined by the archimedes method with water as the liquid medium as for ASTM 378–88 [5] and mechanical strength was recorded by using universal testing machine. Microstructure of the sintered specimens was observed using scanning electron microscope (JEOL –JSM-5610LV). The major crystalline phases present in the specimen was analysed by X-ray diffraction pattern (D/Max ULTIMA). The electrical insulation resistance and flashovers test of the specimen were examined by using an industrial test method of solid insulating material (ASTM D149). RESULTS AND DISCUSSION Physical and Mechanical Properties The results obtained for porosity (P) %, water absorption (WA) %, shrinkage (S) %, bulk density (BD) and mechanical strength (MS) MPa. The average value of the three sample results for each specimen are calculated are given in Table. 2.

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Table 2: Physical and Mechanical Properties of Experimental Insulators Specimen

P (%)

WA (%)

BD (g/cm3)

S (%)

MS (MPa)

SC

1.4052

0.6784

2.0503

5.41

2.48

QB

1.2319

0.5932

2.0546

7.74

3.12

The porosity and water absorption decreased with increasing of bamboo leaf ash content because of gradual densification increasing. It is observed that porosity of QB is significantly lower when compared to SC and this is very advantage for electrical insulator. The water absorption value decreased in BLA blended ceramic material. The amount of water absorbed by the material in service will affect the life of the material and even reduce the resistivity of the material. Therefore, absorbed water reduces the insulation resistance. This may be due to the presence of active silica in treated BLA. The bulk density of the sample QB is slightly higher than SC. This is related to the vertification that contributes to an open pores amount that reduced resulting is more dense ceramic electrical insulator. The shrinkage increased with blended BLA higher due to less significant particles occupied the inter particles spacing as a result of which volume is reduced. The mechanical strength of the blended QB insulator (3.12 MPa) becomes higher than the reference(2.48 MPa) which is possibly suitable to the pozzolanic reaction activity of the BLA. The higher mechanical strength is attributed by the reduction of cracks and flaw [6].

Phase Analysis The XRD results of the experimental insulator are shown in Figure 1. Insulator contains the greatest quartz (SiO2) peak is observed around at 26 (2θ-degree) which is typical diffraction angle for quartz while be short of mullite peaks (2θ = 40.91°). In a blended QB insulator mainly characteristic diffraction peak (2θ = 60.68°) is familiar as mullite (3Al2O3.2SiO2), and the new phase of to be present secondary mullite crystals (2θ = 54.02°) is distinguished. The addition of the BLA is increased the glassy phase became supplementary obvious. It is significantly noticed that the crystalline phases formed in blended insulator, but there is a reduce in quartz content with the increase of mullite phase. Mullite is incredibly vital phase in promoting the mechanical and dielectric properties [7].

Fig. 1: XRD Patterns of the Experimental Insulators

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Morphology Analysis Microstructural images of the insulator are in Figure 2.The image of SC insulator, has higher quartz nature of the standard body, contained much more, coarser and irregularly shaped porosity. The surface of the QB insulator, glassy phase and mullite structure of the sintered specimen are seen. The higher porosity is observed instandard (SC) specimen which is composed of a large quantity of interlocked pores. It is well coincide with the physical properties. The size distribution of mullite whiskers becomes narrow, with adecrease due to a lack of mullite crystals. High mullite content with low quartz and micro pores become more prominent in the blended ceramic electrical insulator (Figure 2b). It is parallel support to the XRD results. From the SEM image, it can be confirmed that blended QB insulator needle-shaped long mullite crystals randomly oriented in all directions in the microstructure would form a three dimensional network to reinforce the glassy matrix and reduce deforming during sintering [8].

Fig. 2: SEM Photograph (a) SC and (b) QBof the Experimental Insulator

Electrical Resistance and Dry Power Frequency Flashover Voltage Test The megger device (model No: 6250 IN) was used to measure the insulation resistance of the specimen. Blended (QB) insulator has the higher value (21.0 GΩ) of insulation resistance than the SC insulator (12.5 GΩ) at the maximum injection 5000 DC voltage. The 5% BLA is acceptable so long as

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it has shown good performance in both strength and electrical insulation. The international electrical Testing Association recommends the minimum insulation resistance 500 Meg ohms at the injection 5000 DC voltage [9]. The flashover voltage tests were conducted according to ANSI C29-1 for visual inspection. In this test, an alternating current voltage of 50Hz frequency was applied to the test specimen in air. The voltage was initially rapidly raised to approximately 75% of the expected flashover voltage value, and then slowly raised until a flashover occurred. It can be observed that the flashover voltage of QB (9.92 kV/mm)is much higher than the SC insulator (8.65kV/mm). The flashover voltage was remarkably influenced by the physical properties, and the presence of higher crystalline silica content in 5 wt% BLA addition insulator [10].

CONCLUSION Fabrication of bamboo leaf ash blended ceramic electrical insulator was achcieved and the quality assessment of its have been investigated. The physical properties and mechanical strength of the blended is enhanced when compared to the reference insulator. The results indicate that the better performance was achieved by BLA blended insulator. The BLA substitution is responsible for the occurrence of higher mullite and low quartz was confirmed by the XRD. The shape of needle-like secondary mullite crystals are seen in the blended insulator microstructure. The blended specimen has higher electrical insulation resistance was achieved than the standard one and is responsible for strength development. Higher value of the flashover voltage of the blended specimen is due to lower porosity and higher crystalline silica content. Hence, forest waste material bamboo leaf ash is potential candidate for electrical insulator fabrication. ACKNOWLEDGEMENT The authors are grateful to Mr. Parthasarathy, Managing Director, M/s Orient Ceramic Industry, Viruthachalam for providing the ceramic materials and thanks are extended to Mr. V. Pandiyan, Deputy General Manager, M/s Global Power Research Institute, Kurinchipadi for electrical insulation resistance and flashover voltage measurement. REFERENCES [1] Olupot, P.W., Jonsson, S. and Byaruhanga, J.K., Development and characterisation of triaxial electrical porcelains from Ugandan ceramic minerals, Cer. Inter. 36(4), 1455–1461, 2010. [2] Juan, A., Medina, C., Guerra, M.I., Morán, J.M., Aguado, P.J., Isabel, M., Rojas, S.D., Frías, M. and Rodríguez, O., Re-use of ceramic wastes in construction, 197–215, 2015. [3] Nasrat, L.S., Hamed, A.F., Hamid, M.a. and Mansour, S.H., Study the flashover voltage for outdoor polymer insulators under desert climatic conditions, Egyp. J. Petrol., 22 (1),1–8, 2013. [4] Sivakumar, G., Hariharan, V., Shanmugam, M. and Mohanraj, K., Fabrication and Properties of Bagasse Ash Blended Ceramic Tiles,6 (12),4991–4994, 2014. [5] Guo, X., Zhu, L., Li, W. and Yang, H., Preparation of SiC powders by carbothermal reduction with bamboo charcoal as renewable carbon source, J. Advan. Cer. 2 (2), 128–134, 2013. [6] Mostafa, N.Y., Shaltout, A.A., Abdel-aal, M.S. and El-maghraby, A., Sintering mechanism of blast furnace slag – kaolin ceramics, Materials and Design, 31(8), 3677–3682, 2010. [7] Hariharan, V., Shanmugam, M., Amutha, K. and Sivakumar, G., Preparation and Characterization of Ceramic Products Using Sugarcane Bagasse ash Waste, 3, 67–70, 2014. [8] Ebrahimpour, O., Dubois, C. and Chaouki, J., Fabrication of mullite-bonded porous SiC ceramics via a sol-gel assisted in situ reaction bonding, J. Eur.Cer. Soc., 34 (2), 237–247, 2014.

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[9] Emel O. Derya yesim tuncel, Evaluation of pyroplastic deformation in sanitaryware porcelain bodies, Ceramics International, 38, 1399–1407, 2012. [10] Moyo, M.G. and Park, E., Ceramic Raw Materials in Tanzania – Structure and Properties for Electrical Insulation Application, International J. Engg. Res. and Tech., 3 (10), 1015–1020, 2014.

High Voltage Solid State Symmetric Supercapacitor Based on GraphenePoyoxometalates Hybrid Electrode with Quinone Doped Hybrid Gel Elecetrolyte Bhawna Nagar, Deepak P. Dubal and Pedro Gomez-Romero Catalan Institute of Nanoscience and Nanotechnology, CIN2, ICN2 (CSIC-ICN), Campus UAB, E-08193 Bellaterra, Barcelona, Spain E-mail: [email protected]; [email protected]

INTRODUCTION Energy storage devices have been widely researched in order to meet the increasing demand ofsustainable energy [1–3]. Among them, Supercapacitor store charge through surface adsorption (EDLC) and surface redox reactions (pseudo-capacitors) hence possesses high power density and excellent cycling stability, sacrificing energy density [4]. The emerging new concept of hybrid electrodes combines high energy with high power and stability. These hybrid electrodes can be made up of combinations of capacitive carbons and faradaic materials (transition metal oxides, polyoxometalates, conducting polymers etc.) [5–7]. In this work, we prepared 3D hierarchical open porous reduced graphene oxide (rGO) through modified Hummer’s method. Subsequently, phospomolybdate (PMo12) polyoxometalate nano-clusters [8, 9] were homogeneously and effectively anchored onto the surface of rGO nanosheets (Figure 1).

Fig. 1: (a, b) SEM Images of rGO and rGO-PMo12 Hybrid materials, respectively, (c) EDS mapping of rGOPMo12 hybrid sample, (d) HR-TEM image of rGO-PMo12 sample, (e, f) STEM images of rGO and rGO-PMo12 hybrid samples, respectively. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 111–114 (2015)

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Figure 1 (a, b) presents SEM images of rGO and rGO-PMo12 hybrid materials, respectively. rGO exhibits 3D open porous architecture composed of ultrathin nanosheets and electronically conductive framework it preserves their 3D open porous structure even after heavy deposition of PMo12 clusters (Figure 1b). EDS mapping in Figure 1 (c) confirms that PMo12nanoclusters are homogeneously anchored onto rGO nanosheets. Figure 1 (d) shows HR-TEM image of rGO-PMo12with black tiny dots of PMo12 clearly seen. STEM imagesare displayed in Figure 1 (e, f). It is unambiguously seen that (Figure 1 c) the surface of rGO nanosheets is blank and free from tiny spots while the surface of rGOPMo12 hybrid is abundantly decorated with PMo12 clusters without any agglomeration. Figure 2 shows the effect of PMo12 on the electrochemical performance of rGO in all-solid-state symmetric configuration. Figure 2 (a) shows the CV curves of rGO and rGO-PMo12 symmetric cells at a scan rate of 20 mV/s. There is an extensive increase in the current density for rGO-PMo12 hybrid cell along with an extension of 0.3 V compared to rGO cell. Furthermore, the rGO-PMo12 symmetric cell show san extended operational voltage (1.6 V)(Figure 2 (b)) and a larger specific capacitance. Figure 2 (c) shows the variation of volumetric capacitance of rGO and rGO-PMo12 symmetric cells as a function of scan rates. The great increase of specific capacitance is due to the faradaic contribution of PMo12 in the nanohybrid. The values reported here are considerably higher than those of other symmetric and asymmetric cells. [4–8]. Figure 2 (d) presents the volumetric power and energy densities of rGO and rGO-PMo12 symmetric cells. These results demonstrate that rGO-PMo12l with polymer gel-electrolyte is promising for high power as well as high energy super capacitors. Our results show a novel hybrid symmetric design with a high performance close to those of asymmetric supercapacitors but keeping the design simplicity and durability of symmetrical systems.

Fig. 2:(a) CV curves and (b) CD curves of rGO and rGO-PMo12 symmetric cells at scan rate of 20 mV/s and current density of 1.27 mA/cm2, respectively, (c) Variation of volumetric capacitance of rGO and rGO-PMo12 based symmetric cells as a function of scan rates, (d) the volumetric power and energy density values of rGO and rGO-PMo12 symmetric cells.

High Voltage Solid State Symmetric Supercapacitor Based on Graphene- Poyoxometalates ...

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Effect of Hydroquinone Doping in Gel Electrolyte The hybrid gel-electrolyte was prepared by doping conventional PVA/H2SO4 polymer gel-electrolyte solution with different concentrations of Hydroquinone (0.1, 0.2 and 0.3 M). Figure 3 (a-c) shows CVs of rGO-PMo12 symmetric cells with HQ doped gel-electrolyte of different concentrations at various scan rates. The additional redox activityof hydroquinone provides more species for fast and reversible redox reactions greatly increasing the electrochemical response of the devices [10]. The highest integrated area of the CV loops of rGO-PMo12 cell is obtained for 0.2 M HQ doped gelelectrolyte, which decreases with further increase in doping concentration of HQ. A similar trend was observed in the behaviors of the Charge-Discharge (CD) curves of rGO-PMo12 cell. In Figure 3(d) also, rGO-PMo12 cell with 0.2 M HQ doped gel-electrolyte exhibits highest volumetric capacitance which decreases with further increase in HQ concentration.

Fig. 3: (a-c) CV curves of rGO-PMo12 symmetric cells with HQ doped gel-electrolyte of different concentrations at various scan rates, (d) summary of volumetric capacitance vs. scan rate of rGO-PMo12 cell for different HQ concentrations, (e) CD curves for rGO-PMo12 symmetric cell with 0.2 M HQ doped electrolyte at different current densities, (f) variation of volumetric capacitance with current density of rGO-PMo12 cell for different concentrations of HQ.

CONCLUSION We have provided a double hybridization approach, in which we have prepared ‘hybrid electrode’ by anchoring PMo12 redox-active clusters on rGO nanosheets, solid-state symmetric hybrid design and redox-active species doped hybrid gel-electrolyte. The rGO-PMo12 symmetric cell with conventional gel-electrolyte shows significant improvement in the cell performance, extending potential window by 0.3 V with energy density of 1.04 mWh/cm3. Furthermore, an impressive, 2-fold increase in the device performance (energy density of 1.99 mWh/cm3) with redox-active electrolyte has been achieved. These findings have proved the potential of the rGO-PMo12 hybrid material and electrolyte as a promising device with high energy density, high power density, and long cycle lifetime for energy storage systems.

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REFERENNCES [1] Simon, P. and Gogotsi, Y. Materials for Electrochemical Capacitors. Nat. Mater. 7, 845–854, 2008. [2] Dubal, D.P., Ayyad, O., Ruiz, V. and Gomez-Romero, P., Hybrid energy storage: the merging of battery and supercapacitor chemistries. Chem. Soc. Rev., 44, 1777–1790, 2015. [3] Pech, D. et al. Ultrahigh-Power Micrometre-Sized Supercapacitors Based on Onion-like Carbon. Nat. Nanotechnol., 5, 651–654, 2010. [4] Simon, P., Gogotsi, Y. and Dunn, B., Where Do Batteries End and Supercapacitors Begin? Science, 343, 1210–1211, 2014. [5] Yu, G. et al. Hybrid nanostructured materials for high-performance electrochemical capacitors. Nano Energy, 2, 213–234, 2013. [6] Suarez-Guevara, J., Ruiz, V. and Gomez-Romero, P., Hybrid energy storage: high voltage aqueous supercapacitors based on activated carbon-phosphotungstate hybrid materials. J. Mater. Chem. A, 2, 1014– 1021, 2014. [7] Dubal, D.P., Gomez-Romero, P., Sankapal, B.R. and Holze, R., Nickel cobaltite as an emerging material for supercapacitors: An overview. Nano Energy, 11, 377–399, 2015. [8] Gómez-Romero, Pedro and Casañ-Pastor, Nieves, Photoredox Chemistry in Oxide Clusters. Photochromic and Redox Properties of Polyoxometalates in Connection with Analog Solid State Colloidal Systems, J. Phys. Chem, 100(30), 12448–54, 1996. [9] Gómez-Romero, P., Polyoxometalates as Photoelectrochemical Models for Quantum-Sized Semiconducting OxidesSolid State Ionics, 101, 243–248, 1997. [10] Roldan, S., Blanco, C., Granda, M., Menendez, R. and Santamaría, R., Towards a further generation of high-energy carbon-based capacitors by using redox-active electrolytes. Angew. Chem., Int. Ed. 50, 1699– 1701, 2011.

Facile Synthesis and Characterization of Nano Andmicro Structured Lead Telluride for Thermoelectric Applications B. Khasimsaheb, S. Neeleshwar and B.K. Panigrahi1 University School of Basic and Applied Sciences, GGS Indraprastha University, New Delhi Materials Physics Division, Materials Science Group, Indira Gandhi Center for Atomic Research, Kalpakam, Tamil Nadu

1

ABSTRACT In the current study, we have studied the effect of pH and surfactant on synthesis of nano and micron-sized Lead Telluride (PbTe) by employing cost effective chemical reduction method. This method has yielded an elongated ~ 5–10 micron length PbTe sheets. Further, these synthesized nanostructures have been characterized by using the X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and High Resolution Transmission Electron Microscope (HRTEM) with Selective Area Electron Diffraction (SAED). XRD analysis confirmed the phase purity and subsequently peak broadening represented the nano and micron-sized structures. Moreover, HRTEM analysis has confirmed the size of the nanocubes (20–30 nm) and nanosheets (10–30 nm). The size and shape of these nano and micron-sized structures are more prone to enhance the phonon scatterings at grain boundaries without effecting their electronic transport properties, which eventually enhances the Figure of Merit of thermoelectric materials. Keywords: Lead Telluride, Nanocubes, Nanosheets, Microsheets, FESEM and HRTEM.

INTRODUCTION Enormous efforts have been put toward controlling the properties of the nanoparticles by controlling their size and shape due to quantum confinement phenomena. Thermoelectric material’s uses its majority carriers to convert the heat into direct electricity and vice versa. The thermoelectric materials, have no moving parts, have long lifetime of reliable operation and can be operated in friendly environment (contain no chlorofluorocarbons). The thermoelectric energy conversion efficiency depends on dimension less figure of merit (zT). The increase in figure of merit can be achieved with decrease in dimensionality [1–6]. The study of lead chalcogenides nanoparticles as one of the thermoelectric materials, has gained a lot of attention in recent years due to its application in wide range (400–800 K). Lead telluride (PbTe) is particularly promising for high-ZT thermoelectric material, due to its rock salt cubic structure, narrow band gap (0.32 eV at room temperature) and the large Bohr radius (46 nm) possessing strong quantum confinement. Preparation of the PbTe nanostructures within the excitonic Bohr atomic radius (~46 nm) [7] using simple chemical method is a challenging task due to its sensitiveness towards concentration, pH and temperature. Since last decades, so many methods have been reported by researchers to synthesize different nanostructures of PbTe with high surface to volume ratio such as nanocrystals, [8, 9] nanorods, [10] nanoboxes, [11] nanowires, [12–13], [27–28] nanosheets, [29,26] hollow spheres and V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 115–120 (2015)

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Application off Nanostructuredd Materials for Energy E and Enviironmental Technology

nanotuubes [14, 15]. There are diffferent routes have h been sugggested to conttrol the shape using countinng surfacctants, [8], [16 6–18], [28] seed growth, [19–21] and thee use of differrent template materials. [222– 23] Recently R some research grouups have reporrted the controolled synthesiis of PbTe nannocrystals, [244] whichh are cubic in shape for lonng reaction tim me whereas naanoparticles with w shape in cube c octahedral have been b reported d for short reaaction timingss. [9], [ 25], [28] They alsso showed thhat particle sizze depennds on the reacction timings as a for long groowth time, the size of the paarticles increasses. Inn the present in nvestigation, this t paper is focused f on surrfactant free PbbTe nanostrucctures using thhe chemiical reduction method whicch is cost effeective. PbTe nanocubes n andd nanosheets are a synthesizeed by chaanging the pH H of the solutioon; whereas micro m sheets aree synthesized by using PVP P as a surfactannt for 244 hrs reaction time. t

EXPE ERIMENTA AL PROCEDURES Semicconducting Pb bTe nano andd micro structtures small band gap preppared by chem mical reductioon methood. The presen nt investigatioon of the PbT Te nano and microstructure m es synthesizedd from differennt pH, reeaction time an nd at differentt temperaturess. for the phase and structtural analysis by the X-raay A prepared sample All s was characterized, c diffracction (XRD) using u PANalyttical X-Ray Diffractometer D with a Cu–K α. The transm mission electroon microscope (TEM) was carried out o by using Carl C Zeiss maakeLIBRA 2000 FE at 200kV V and analyzeed with Gatan G digital micrograph m software.

Fig. 1: (aa) XRD Patternns of the Purifiedd PbTe Nanocuubes, (b) XRD Paatterns for Nanoocubes, Nanoshheets and Microosheets

Facile Syntthesis and Charaacterization of Nano N Andmicro Structured S Lead Telluride

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RESU ULTS AND DISCUSSIO D NS Figuree 1 (a&b), sho ows the XRD patterns of PbTe nano andd microstructuures with diffeerent conditionns tempeerature, pH an nd reaction tim me. All the samples exhibit a simple cuubic PbTe phhase with spacce group (Fm 3 m) [JC CPDS card #788–1905] as shhown in Figuree 1. The peakss broadening were w due to thhe quantuum size effectts. The particlle size was estimated by Sccherer formulaa (d = kλ/βCoosθ), where k is 0.90, λ is CuKα waavelength (1.54 nm), β is thhe full width half h maximum m of the intensse peak and θ is e averrage crystallinne size was arround 20–30 nm n for the PbbTe nanocubees, Braggg angle. The estimated 10–300 nm for PbTee nanosheets [8, 13], 50–70 nm for microo sheets. Then the samples were w performeed HR-TEM analysis for f further phhase conformaation like crysttalline nature,, morphology,, d-spacing annd its parrticle size anallysis.

Fig. 2:: TEM images illustrating i the particle p size disstribution of PbTe nanocubes(lleft)and nanoshheets(right), in (a) and (b) lower inserts represents theirr size distribution respectivelyy. Upper insertss represents the HR-TEM imagge osheet. of nanocube and nano

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Fuurthermore, in n Figures 2(aa) and (b), thee TEM imagees illustrate thhe size distribbution of PbT Te nanoccubes and nan nosheets 24 hoours respectivvely. As observed from thee lower histoggram in Figurre 2(a), the t average siize of the nannocubes arounnd ~ 25 nm, nanocube n withh highly crystaalline in naturre (upperr insert). Figu ure 2(b) repreesents the 2D PbTe nanoshheets withaverrage 9 × 16 nm n widths annd lengthh (lower inserts), nanosheeet with highlly crystalline in nature (uupper insert). Selective areea electroon diffraction n (SAED) coonfirmed that the samples are highly polycrystallin p ne in nature in i agreem mentwith the XRD pattern of the PbTe nanocubes annd nanosheets. The d spacinng of the PbT Te nanostructures weree well in agreeement with thhe bulk. PbTee micro sheetss were prepareed by using thhe hod PVP as a surfactant and reaction was carried out at 150°°C for 12 hrrs. hydrothermal meth EM imaging. Microostructures furtther conformeed by using SE Fiigure 3. Dem monstrate the PbTe 5–10 µm µ micron shheets with nanno width, thee homogeneouus distribbution of Pb and Te elemeents in PbTe was confirm med by SEM and a energy dispersive d x-raay (EDX X) analysis exh hibited a Pb/Tee ratio of 61.84/38.16 (1:1).

Fig. 3 (a, ( b, c and d): Represents thee SEM Images of o PbTe Microshheets, (a, b and c) Showin ng the 5–10 µm m Length Sheets and (d) Showinng the Tilted Naano Width Sheeets

CONCLUSIONS In sum mmary, PbTee nano and micro m structurees were synthhesized by chemical reducttion as well as a hydrothermal synth hesis. XRD coonfirms prepaared samples are in simplee cubic structuure and furtheer EM. The TEM M studies reveaal the shape of the nanostruuctures and cryystalline naturre. confirrmed by HRTE With varying the pH p and use off surfactant chhanges the moorphology froom cubes to nano n and micrro sheetss. The size and shape of theese nano and micron-sized structures aree more prone to enhance thhe phonoon scatterings at grain bounndaries withouut effecting thheir electronicc transport prooperties, whicch eventuually enhancess the Figure off Merit of therrmoelectric materials. m ACK KNOLEDGEM MENTS This work w was spo onsored by DAE, D BRNS project p grant number-20100/34/47/BRNS S/2317. One of o authorr (B. Khasim Saheb) S acknow wledges UGC C-MANF for thhe SRF fellow wship.

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REFERENCES [1] Hicks, L.D. and Dresselhaus, M.S., Effect of quantum-well structures on the thermoelectric figure of merit, Phys. ReV. B, 47, 12727, 1993. [2] Hicks, L.D. and Dresselhaus, M.S., Thermoelectric figure of merit of a one-dimensional conductor, Phys. ReV. B, 47, 16631, 1993. [3] Venhatasubramanian, R., Siivola, E., Colpitts, T. and O’Quinn, B., Three-dimensional modeling of nanoscale Seebeck measurements by scanning thermoelectric microscopy, Nature, 413, 597, 2001. [4] Harman, T.C., Taylor, P.J., Spears, D.L. and Walsh, M.P., Thermoelectric quantum-dot super lattices with high ZT, J. Electron. Mater. 29, 2000. [5] Harman, T.C., Taylor, P.J., Walsh, M.P. and LaForge, B.E., Quantum dot super lattice thermoelectric materials and devices, Science, 297, 2229, 2002. [6] Heremans, J.P., Thrush, C.M., Morelli, D.T. and Wu, M.-C., Thermoelectric power of bismuth nanocomposites, Phys. Rev. Lett. 88, 216801 (2002). [7] Wise, F.W., Lead Salt Quantum Dots: the Limit of Strong Quantum Confinement, Acc. Chem. Res, 33, 773, 2000. [8] Mokari, Taleb; Zhang, Minjuan and Yang, Peidong, Shape, Size, and Assembly Control of PbTe Nanocrystals, AM. CHEM. SOC, JACS, 129, 9864–9865, 2007. [9] Urban, J.J., Talapin, D.V., Shevchenko, E.V. and Murray, C.B., Self-Assembly of PbTe Quantum Dots into Nanocrystal Superlattices and Glassy Films, J. Am. Chem. Soc. 2006, 128, 3248. [10] Peng, X., Manna, L., Yang, W., Wickham, J., Scher, E., Kadavanich, A. and Alivisatos, A.P., Shape control of CdSe nanocrystals, Nature, 404, 59–61, 2000. [11] Wang, W.Z., Poudel, B., Wang, D.Z. and Ren, Z.F., Synthesis of PbTe Nanoboxes Using a Solvothermal Technique, Adv. Mate, 17, 2110, 2005. [12] Zhang, L.Z., Yu, J.C., Mo, M.S., Wu, L., Kwong, K.W. and Li, Q., A General in situ Hydrothermal Rolling‐Up Formation of One‐Dimensional, Single‐Crystalline Lead Telluride Nanostructures, Small, 1, 349, 2005. [13] Fardy, M., Hochbaum, A.I., Goldberger, J., Zhang, M.M. and Yang, P.D., Synthesis and Thermoelectrical Characterization of Lead Chalcogenide Nanowires, Adv. Mater., 19, 3047, 2007. [14] Tong, H., Zhu, Y.J., Yang, L.X., Li, L. and Zhang, L., Lead Chalcogenide Nanotubes Synthesized by Biomolecule‐Assisted Self‐Assembly of Nanocrystals at Room Temperature, Angew. Chem., Int. Ed. 45, 7739, 2006. [15] Zou, G.F., Liu, Z.P., Wang, D.B., Jiang, C.G. and Qian, Y.T., EurSelected‐control solvothermal synthesis of nanoscale hollow spheres and single‐crystal tubes of PbTe, J. Inorg. Chem., 22, 4521, 2004. [16] Qiu, X.F., Lou, Y.B., Samia, A.C.S., Devadoss, A., Burgess, J.D., Dayal, S., Burda, C., PbTe nanorods by sonoelectrochemistry, Angew. Chem., Int. Ed., 44, 5855, 2005. [17] Manna, L., Milliron, D.J., Meisel, A., Scher, E.C. and Alivisatos, A.P., Controlled growth of tetrapodbranched inorganic nanocrystals, Nat. Mater., 2, 382–385, 2003. [18] Yu, W.W., Wang, Y.A. and Peng, X.G., Formation and stability of size-, shape-, and structure-controlled CdTe nanocrystals: ligand effects on monomers and nanocrystals, Chem. Mater., 15, 4300–4308, 2003. [19] Talapin, D.V., Koeppe, R., Gotzinger, S., Kornowski, A., Lupton, J.M., Rogach, A.L., Benson, O., Feldmann, J. and Weller, H., Highly emissive colloidal CdSe/CdS heterostructures of mixed dimensionality, Nano Lett., 3, 1677–1681, 2003. [20] Trentler, T.J., Hickman, K.M., Goel, S., Viano, A.M., Gibbons, P.C. and Buhro, E., Solution-liquid-solid growth of crystalline Ill-V semiconductors: an analogy to vapor-liquid-solid growth, Science, 270, 1791– 1794, 1995. [21] Kan, S., Mokari, T., Rothenberg, E. and Banin, U., Synthesis and size-dependent properties of zinc-blende semiconductor quantum rods, Nat. Mater., 2, 155–158, 2002.

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[22] Kovtyukhova, N.I., Kelley, B.K. and Mallouk, T.E., Coaxially Gated In-Wire Thin-Film Transistors Made by Template Assembly, J. Am. Chem. Soc., 126, 12738–12739, 2004. [23] Pena, D., Mbindyo, J., Carado, A., Mallouk, T., Keating, C., Razavi, B. and Mayer, T.. Template growth of photoconductive metal-CdSe-metal nanowires, J. Phys. Chem. B, 106, 7458–7462, 2002. [24] Lu, W., Fang, J., Stokes, K.L. and Lin, J., Shape evolution and self assembly of monodisperse PbTe nanocrystals, J. Am. Chem. Soc., 126, 11798–11799, 2004. [25] Murphy, J.E., Beard, M.C., Norman, A.G., Ahrenkiel, S. P., Johnson, J.C., Yu, P., Micic, O.I., Ellingson, R.J. and Nozik, A.J., PbTe colloidal nanocrystals: synthesis, characterization, and multiple exciton generation, J. Am. Chem. Soc., 128, 3241–3247, 2006. [26] Khasimsaheb, B., Neeleshwar, S., Pandiyan, S. Amrita and Panigrahi, B.K., Two Dimensional-Lead Selenide (PbSe) Nanosheets for Renewable Energy Applications, Advanced Science Letters, Vol. 20, 1383–1386, 2014 [27] Lee, Seung Hyun; Shim, Wooyoung; Jang, So Young; Roh, JongWook; Kim, Philip; Jeunghee Parkand Wooyoung Lee. Thermoelectric properties of individual single-crystalline PbTe nanowires grown by a vapor transport method, Nanotechnology, 22, 295707, 2011. [28] Guo’an Tai, Bin Zhou, and Wanlin Guo. Structural characterization and thermoelectric transport properties of uniform single-crystalline lead telluride nanowires, J. Phys. Chem. C, 112, 11314–11318, 2008. [29] Zhu, T.J., Chen, X., Meng, X.Y., Zhao, X.B. and He, J., Anisotropic Growth of Cubic PbTe Nanoparticles to Nanosheets: Controlled Synthesis and Growth Mechanisms, Crystal Growth and Design, Vol. 10, No. 8, 3727–3731, 2010.

Phytogenic Nanosilver Incorporated with Epoxy Coating on PVC Materials and Their Antibiofilm Properties N. Supraja, S. Adam1, T.N.V.K.V. Prasad1 and E. David Department of Biotechnology, Thiruvalluvar University, Vellore Institute of Frontier Technology, Regional Agricultural Research Station, ANGRAU, Tirupati, A.P.

1

ABSTRACT The advantages of nanoscale materials (size 1–99 nm in at least one dimension) could be realized with their potential applications in diversified branches of science. In the present investigation, we report for the first time, synthesis of homogeneous epoxy coatings containing phytogenic AgNPs on PVC and glass substrates by room-temperature curing of fully mixed epoxy slurry diluted by acetone. Alstonia scholaris bark extract was used to reduce and stabilize silver slurry. The surface morphology and mechanical properties of these coatings were characterized using techniques such as, UV-Vis Spectrometry, X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FT-IR), Epi-fluorescence microscopy and scanning electron microscopy (SEM). The efficacy of incorporating AgNPs on the biofilm (scale) as anti-microbial resistance of epoxycoated PVC was thoroughly investigated, by total viable microbial counts (CFU/cm2) from epoxy coating for duration of 5–28 days. The phytogenic-AgNPs were found to be significant in improving the physical properties like microstructure of the coating matrix, coating barrier performance and also enhanced the antimicrobial efficacy of Ag NPs played an important role in improving the anti-biofilm performance of these epoxy coatings. Keywords: Alstonia scholaris, Ag nanoparticles, Epoxy Coating, Biofilm Resistance.

INTRODUCTION The term ‘epoxy resin’ refers to both the pre polymer and its cured resin/hardener system. The characteristic group, a three membered ring known as the epoxy, epoxide, oxirane, glycidyl or ethoxyline group are highly strained and therefore very reactive. Epoxy resins can be cross-linked through a polymerization reaction with a hardener at room temperature or at elevated temperatures (latent reaction). Epoxy resins are versatile with excellent chemical and heat resistance, high adhesive strength, good impact resistance, high strength and hardness, and high electrical insulation May (1987). Adams et al. (1986), Ellis (1993).Epoxy has been widely used as a coating material to protect the steel reinforcement in concrete structures Galliano et al. (2002). Talo et al. (1999), because of its outstanding process ability, excellent chemical resistance, good electrical insulating properties, and strong adhesion/affinity to heterogeneous materials. Epoxy coatings generally reduce the corrosion of a metallic substrate subject to an electrolyte in two ways. First, they act as a physical barrier layer to control the ingress of deleterious species. Second, they can serve as a reservoir for corrosion inhibitors to aid the steel surface in resisting attack by aggressive species such as chloride anions. The present study reveals the influence of phytogenic AgNPs, which are incorporated with the epoxy coating on V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 121–124 (2015)

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the surface morphology, anti-scale behavior of PVC materials. It is expected to shed more light on the fundamental mechanisms through which nanoparticles interact with the epoxy matrix and thus provide guidance for the design of high-performance epoxy coatings used for anti scale protection of PVC pipelines from biofilm formation.

MATERIALS The liquid epoxy resin was blend with diluents and diglycedal ether of bis-phenol-A, whereas the hardener was based on adduction reaction chemistry of aliphatic amines. The weight ratio of the epoxy resin to the hardener was 2:1. The PVC coupons were prepared from CECRI, Karaikudi with AgNPs 50 nm diameter. Preparation of Aqueous Extract (ABE) 10 g of shade dried powder of Alstonia scholaris was boiled and filtered for experimentations. 90 mL aqueous solution of 1.0 × 10–3 M silver nitrate was mixed with a 10 mL of 5% aqueous bark extract of A. scholaris Prabha shetty et al. (2014). Epoxy resin nano suspensions with 1.0wt% of AgNPs were prepared by immersing the nanofillers in epoxy resin further incubated for overnight without any disturbance so that the resin completely wets the nanostructures. The mixture was mechanically stirred twice at 600 rpm for 1 hr at room temperature to remove bubbles in the solution and to prevent the settlement of Ag nanofillers during the curing process, low speed (200 rpm) mechanical stirring was conducted at 70°C for 3–4 h in a water bath. Finally, the solution was poured into silicone rubber molds and cured at 120°C for 5 h and then cooled down naturally to room temperature. Coating Preparation Fourier transform infrared spectroscopy (FTIR) indicated that the sonication processing in acetone did not induce chemical change in the epoxy network, thus acetone was chosen as the solvent. AgNPs of 1 wt.% of the total weight of resin and hardener, were added to the resin-acetone solution, by stirring at

Fig. 1: Epi-Fluorescence Pictures Showing the Anti-Biofilm Activity from 3rd Day to 27th Day

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speeds up to 1550 rpm and sonication for 10 min. Later the hardener-acetone solution was added to the mixture, followed again by stirring and sonication for 10 min. The glass coupons of 1.5 × 1.5cm sizes were dipped into the finally obtained mixture for one time and then kept in a dry place at room temperature for 7 days for full curing, formation of a uniform coating in preparing the anti-biofilm. Coupons were immersed in drinking water test sample for 20 days and after completion of incubation period the formed biofilms were formed on PVC coupons, these coupons were tested and coated by epoxy, Epoxy coated with Alstonia scholaris Silver nanoparticles and kept for incubation period up to 27 days and check the total viable count for every 5 days and Epi-fluorescence images for every 3 days to identify the anti biofilm activity. Total cell counts in biofilm samples and biofilm suspensions were determined by staining of the bacteria and fungi for 20min with 4, 6-diamidino-2phenylindole (5 µg/ml) and subsequent quantification by Epi-fluorescence microscopy at 1,000-fold magnification as given in Figure 1.

Anti Biofilm Activity Coupons were immersed in drinking water test sample for 20 days and after completion of incubation period up to a period of 27 days. During this period to identify the anti biofilm activity total viable count was noticed for every 5 days and Epi-fluorescence images for every 3 days. The bacterial and fungal stains were stained with 4, 6-diamidino-2-phenylindole (5 µg/ml) and subsequent quantification by Epi-fluorescence microscopy at 1,000-fold magnification was performed. RESULTS AND CONCLUSION In this study, phytogenic AgNPs were produced using the Alstonia Scholaris bark extract as reducing and stabilizing agent of silver ions. The anti-biofilm of pure, mixed epoxy coatings and epoxy coated

Biofilm formation on slide

Normal slide

Epoxy coating on sliders

Epoxy + Ag Nanoparticles coated on slide

Biofilm degradation by epoxy coating on slide

Biofilm Degradation by epoxycoating + Ag nanoparticles

Fig. 2: Visual Observation of Epoxy Coating and Silver Nanoparticles Mediated Epoxy Coating Glass Materials and its Anti-Biofilm Activity

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with phytogenic AgNPs applied on reinforcing PVC coupons were evaluated by means of total viable count and Epi-fluorescence microscopic studies. The intact epoxy coatings with AgNPs provided a much higher degree of biofilm protection than epoxy coating. Epoxy coatings were significantly outperformed by the impact of AgNPs coating. Interconnected regions of AgNPs in the mixed epoxy coating appeared to provide an anti-biofilm pathway to the underlying PVC coupons so that biofilm i.e., anti-scaling occurred on the surface of coupons as shown in Figure 2. The non-uniformity of coating thickness must be overcome with an alternative coating process to improve the biofilm performance of epoxy coatings for practical applications.

REFERENCES [1] May, C. (Ed.) (1987). Epoxy resins: chemistry and technology CRC press. [2] Mc Adams, L.V. and Mc, Gannon, J.A. (1986). Encyclopaedia of polymer science and engineering, Wiley Inter science 2nd ed Vol. 6. [3] Ellis, B. (Ed.) (1993). Chemistry and technology of epoxy resins (1st ed., 42–43). London: Blackie Academic and Professional. [4] Galliano, F. and Landolt, D. (2002). Evaluation of corrosion protection properties of additives for waterborne epoxy coatings on steel. Progress in Organic Coatings 44: 217–225. [5] Talo, A., Forsen, O. and Yläsaari, S. (1999). Corrosion protective polyaniline epoxy blend coatings on mild steel. Synthetic Metals 102: 1394–1395. [6] Prabha, shetty G., Supraja, N., Garud, M. and Prasad, T.N.V.K.V. (2014). Synthesis, Characterization and Anti microbial activity of Alstonia scholaris bark extract mediated silver nanoparticles. Journal of Nano Structures in Chemistry DOI:10.1007/S40097-014-0132-Z.

Synthesis and Characterization of ZnO NRs and Different QDs for Solar Cells Fabrication M. Kamruzzaman, J. Schneider1 and J.A. Zapien Department of Physics and Materials Science and Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Hong Kong SAR, P.R. China 1 Department of Physics and Materials Science and Centre for Functional Photonics (CFP), City University of Hong Kong, Hong Kong SAR, P.R. China E-mail: [email protected]; [email protected]; [email protected]

ABSTRACT ZnO nanorod arrays (NRAs) based quantum dots (QDs) solar cells have attracted much attention due to their potential applications in photovoltaic solar cells for overcoming the limits of conventional junction solar cell devices. ZnO NRAs were fabricated by a low cost simple hydrothermal process on different substrates on different seed layers and CdSe, CdTe, CdS and CISeS QDs were also synthesized by chemical solution process. The SEM images show that the density of nanorods depends on several factors such as the seed layers, concentration, growth time and on different substrates. The TEM images show ZnO nanorods to be a single crystalline in nature and QDs are uniform shape and size. PL results of ZnO NRs show a broad near band edge (NBE) emission peak at around Ӌ 380 nm which is close to the band gap energy of ZnO and a small peak arises at 532 nm to be related to the defect phenomena and for CdS, CdSe and CdTe QDs are to be 438 nm, 554 nm and 569 nm, respectively. The crystal structure of ZnO NRAs was characterized by XRD and the gain sizes were found to be lie in between 8–17 nm. The absorption peak was found to be ~380 nm for ZnO NRAs and 425 nm, 557 nm, 554 nm, and 818 nm for CdS, CdSe, CdTe and CISeS QDs. So, the good crystallinity and controlling the density of ZnO NRAs and also controlling size of QDs to tune the band gap, it is possible to optimize light trapping over a wide spectral range, as demonstrated for Si nanorods solar cells, thus enabling efficient and economical devices to produce higher photovoltaic conversion efficiency solar cells.

INTRODUCTION In the nanotechnology era an intensive research has been focused on fabricating one dimensional (ID) ZnO nanostructures and correlating their morphologies with their size-related mechanical, chemical, optical and electrical properties [1]. ZnO is applied as key material in electronic, optoelectronic, electrochemical, and electromechanical devices [1], such as ultraviolet (UV) lasers, light-emitting diodes, field emission devices, high performance nanosensors, solar cells, piezoelectric nanogenerators, biosensor, nanopiezotronics, flat panel displays, quantum devices due to its intrinsic properties of non- toxicity, good electrical and optical behaviors [2]. Even though various kinds of ZnO nanostructures have been realized, however ZnO nanorods (NRs) has been most widely studied because of easy formation and device applications as interconnects and functional units in fabricating those devices [3]. To synthesize 1D ZnO nanorods different methods have been reported both with physical and chemical approaches such as pulsed laser deposition, vapor phase transport technique, thermal decomposition of precursors, oxidation of zinc metal, metal-organic vapor phase, molecular V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 125–130 (2015)

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beam epitaxy, different chemical vapor deposition techniques, and magnetron sputtering [4]. However, these methods require moderate to high temperature to grow the NRAs on commercial scale, and they are expensive [5]. On the other hand, hydrothermal growth process is much cheaper, very simple and does not require stringent experimental conditions. In view of all these aspects we have synthesized ZnO NRAs on different substrates using various kinds of chemicals and investigated their structural and optical properties using SEM, TEM, XRD, UV-Vis and PL spectroscopies, respectively.

EXPERIMENTAL PROCEDURES Zinc acetate dehydrate (ZnAce), potassium hydroxide, sodium hydroxide, 3-methoxypropionitrile (MPN), zinc chloride and diethanolamine (DEA) have been used to form the seed layer solution. Zinc nitrate hexahydrate and hexamethylenetetramine were used to grow the ZnO NRs. We have followed same condition according to [6] to prepare all samples. CdSe, CdTe, CdS and CISeS QDs were synthesized by chemical solution method and their experimental description is given elsewhere [7–9]. RESULTS AND DISCUSSION Scanning Electron Microscopy (SEM) and EDX ZnO NRs were grown from equimolar concentration (0.025 M) of zinc nitrate hexahydrate and hexamythalamine under similar synthesis conditions along on various reduction reagents for seed layer solutions is shown in Figure 1, (i) ZnAce and NaOH (1st row), (ii) ZnAce and KOH (2nd row), (iii) ZnAce and MPN (3rd row), (iv) ZnAce and DEA (4th row) and (v) ZnCl2 and NaOH (5th row), respectively. From 1st row we see that the synthesized nanorods are not vertically aligned on the ITO substrate however for MPN (2nd row), KOH (2nd row) and DEA (4th row) nanorods are vertically aligned on the substrates. It is seen that ZnO NRAs grown on MPN, DEA, KOH seed layers are better than NaOH and ZnCl2 (1st and 5th rows). The average diameter of ZnO NRs using KOH is larger than NaOH due to higher reaction rate constant. However, for MPN and DEA, ZnO NRs are vertically grown on three substrates. Since MPN and DEA work as stabilizer reagents and their viscosity is higher than NaOH a and KOH. The longer stability and homogeneity of MPN and DEA solutions make smooth and adhere seed layers on all the substrate that favorable vertical aligned ZnO nanorods. The ZnO NRs grown on the MPN (300 mM) based seed layers are more oriented and the diameter are larger than those of NaOH and KOH based, because both the sol gel and precursor solutions concentrations were higher than KOH (30mM) and NaOH (30 mM) solutions and the obtained results are consistence with the published results [10]. On the other hand, when ZnCl2 is used as seed layers solution the quality of NRs is poor and there may be many defects. When ZnCl2 and NaOH are dissolved in methanol for ZnO seed layers it may mixed with other phases Zn(OH)2 and Zn5(OH)8Cl2.H2O. The presence of these phases in the final composition of the material indicates that the conversion of reactants into the desired ZnO product was not complete and Zn5(OH)8Cl2.H2O is formed when the concentration of the Zn2+ ions is higher than 0.01 M [11], which is in good agreement with our obtained results and the poor crystallinity is also observed in XRD, SEM and PL spectra. The length of ZnO NRs for all samples is found to be around 1 μm. Transmission Electron Microscopy (TEM) HRTEM and SEAD TEM (Figure 1 column 4) images show the single crystalline properties of nondefect sites with c-axis orientation. The HRTEM images (colmn 4) display the lattice constants 0.2 nm and 0.5 nm corresponding to (002) plane and d-spacing, respectively, confirmed that ZnO nanorods

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are preferentially oriented in the c-axis direction. Size of CdS, CdSe, CdTe and CISeS QDs are found to be ~2 nm, 3–4 nm, 3–4 nm and 5 nm, respectively (not shown here). AZON

FTON

AZOK

FTOK

ITOK

AZOM

FTOM

ITOM

AZOD

FTOD

ITOD

FTOZC

ITOZC

ITON

Fig. 1: SEM images top view of ZnO NRs grown on 1st row (NaOH), 2nd row (KOH), 3rd row (MPN), 4th row (EA) and 5th row (ZnCl2) and their side view (inset), (b) TEM images for HRTEM and SEAD (inset), (c) XRD patterns (right column).

X-Ray Diffraction (XRD) The XRD patterns of all samples are shown in Figure 1 (right colmn). Some sharp peaks arises in the spectra correspond to (100), (002), (101), (102), (200) and (112) planes. All the diffraction peaks were indexed to hexagonal structure according to JCPDS card No. 036–1451. From these figures it is evidence that ZnO NRAs vertically preferred oriented along (002) plane. The lattice constants of ZnO NRs for (100) and (002) planes and the average grain were calculated using Eqns. (1) and (2), respectively:

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1 d hkl

⎡ 4 (h 2 + hk + k 2 l 2 ⎤ =⎢ + 2⎥ a2 c ⎥⎦ ⎢⎣ 3

Dg =

0.9λ Δ cos θ

1

2

… (1) … (2)

where, Dg is the average grain size, λ is the wavelength of the producing x-ray CuKα (λ = 1.5406 Å),

Fig. 2: PL spectra (top row) of ZnO NRs, 1st (ZnAce+NaOH), 2nd (ZnAcee+KOH), 3rd row (ZnAce+MPN), 4th (ZnCl2+NaOH) sol gel and their corresponding UV–Vis spectra (below row).

θ Bragg angle in degree and Δ is FWHM. The obtained values of “a” and “c” are in good agreement with [12] and average grain size was found to be in the range 8 nm to 121 nm.

Photoluminescence and UV-vis Spectroscopies A broad peak is observed at around 380 nm (Figure 2) which is called near band edge (NBE) emission and another small peak arises at 532 nm corresponds to a defect-related luminescence, due to the oxygen vacancies in ZnO which is occur from radiative transitions between shallow donors (oxygen vacancies), deep acceptors (Zn vacancies) and interstitial zinc [13] and the defect level is located below the conduction band edge [13]. The emission peak for CdS, CdSe and CdTe QDs are 438 nm, 554 nm and 569 nm (Figure 33rd), respectively. A strong absorption peak appears at around 379–381 nm (Figure 2 below row) for all samples and the smallest average diameter of ZnO NRs has the best absorption for UV light. These sharp strong absorption peaks correspond to the direct band gap of he samples [14]. The absorption peak for CdS, CdSe, CdTe and CISeS QDs are 425 nm, 558 nm (460 nm), 554 nm and 818 nm (Figure 3 1st), respectively.

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Fig. 3: Absorption Spectra of CdS, CdSe, CdTe QDs (Figure 1st ), CISeS (Figure 2nd) and PL Spectra CdS, CdSe, CdTe QDs (Figure 3rd)

CONCLUSIONS ZnO NRs and QDs (CdSe, CdTe, CdS and CISeS) have been synthesized successfully. Vertically ZnO NRs is better for MPN, DEA and KOH than NaOH, ZnCl2 solutions. ZnO NRAs highly oriented along the (002) plane and direct band gap lies in between 3.26 to 3.27 eV. The better crystal quality, fewer structural defect and better aligned ZnO nanorods were obtained for MPN, DEA and KOH. Thus MPN, DEA and KOH based sol-gel solutions should be selected for synthesizing nanorod-ZnOs. Better aligned, better crystalline and fewer defects suggest their potential applications in optoelectronic devices for power-saving, ZnO NRs based QDs solar cells devices for higher efficiency, longitivity and stability. ACKNOWLEDGEMENTS The authors would like to thank City University of Hong Kong for financial support. REFERENCES [1] Keem, K., Kim, H., Kim, G., Lee, J., Min, B., Cho, K., Sung, M. and Kim, S, Appl. Phys. Lett. 84, 4376, 2004. [2] Corcoran, E., Sci. Am. 263, 74, 1990. [3] Wang, Z.L., Adv. Mater. 12, 1295, 2000. [4] Cao, B.Q., Lorenz, M., Rahm, A., Wenckstern, H., Czekalla, C., Lenzner, J., Benndorf, G. and Grundmann, M., Nanotechnology 18, 455707:1–455707:45, 2007. [5] Yao, B.D., Chan, Y.F. and Wang, N., Appl. Phys. Lett., 81, 757, 2002. [6] Choi, J., You, X., Kim, C., Park, J. and Pak, J.J., J. Electrical Engineering and Technology, 5, 640–645, 2010. [7] Nordell, K.J., Boatman, E.M., Lisensky, G.C. and Easier, A.S., J Chem Edu 82, 1697–1699, 2005. [8] Wu, S., Dou, J., Zhang, J. and Zhang, S., J. Mater. Chem. 22, 1457, 2012. [9] Daniel, M.H., Fuke, N., Makarov, S.N., Pietryga, M.J. and Klimov, V., Nature Communications 42887. [10] Lei, Y., Qu, F. and Wu, X., Nano-Micro Letters 4, 45–51, 2012. [11] Rakhshani, A.E., Journal of Physics D: Applied Physics 41, 1–6, 2008.

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[12] Jagadish, C. and Pearton, S.J. Zinc Oxide Bulk, Elseviser Ltd. 2006. [13] Chang, P.C., Chien, C.J., Stichtenoth, D., Ronning, C. and Lu, C.G, Appl. Phy. Lett 90, 11310, 2007. [14] Sridevi, D. and Rajendran, K.V, Bulletin of Materials Science 32, 165–168, 2009.

Preparation and Characterisation of Nickel Aluminate—A Solid Acid Catalyst N. Neelakandeswari, N. Rajasekaran, K. Uthayarani1 and M. Chitra1 Department of Chemistry, Sri Ramakrishna Engineering College, Coimbatore 1 Department of Physics, Sri Ramakrishna Engineering College, Coimbatore

ABSTRACT In this work, mesoporous nickel aluminate, a solid acid catalyst is prepared via hydrothermal route and characterized by Fourier-transform Infra Red spectroscopy (FT-IR), Powder X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM) and N2 – adsorption desorption analysis. Catalytic efficiency of the prepared solid acid catalyst is tested towards the acylation reaction. Various parameters like the effect of solvent, temperature, catalyst quantity etc., were optimized and the results are presented in this paper.

INTRODUCTION Acylation reaction is one of the most important reaction for the preparation of biologically active compounds. Industrially accepted and practiced protocol for the acylation reaction is Friedel-crafts acylation [1]. However, the reaction requires stoichiometric amount of lewis acid catalysts like AlCl3, BF3, ZnCl2 [2,3] etc., under homogenious condition, consequently, this reaction finds some limitations as far as the green technology is concerned due to their low yield, lack of selectivity and the production of unwanted corrosive by-products like HCl in addition to catalyst recovery and reusability. Hence, there is a considerable interest in the use of solid acids as alternatives for hazardous and corrosive protonic or Lewis acids. Hence in this work, we report the preparation of new solid acid Nickel Aluminate for acylation of anisole. EXPERIMENTAL DETAILS Preparation of Nickel Aluminate To an emulsion of 0.1 M aqueous Sodium Dodecyl Sulphate with n-hexane, a mixture of 0.05 M Nickel Chloride and 0.95 M Aluminium Chloride is added drop wise and the pH of the solution was adjusted to 10 by the addition of ammonium hydroxide. The gel obtained is allowed to stir at room temperature for 3 hrs and transferred into a clean Teflon lined stainless steel autoclave and maintained at 140°C for 3 hrs. Aerogel thus obtained is washed with water, dried at 100°C for 6hrs and calcined at 600°C for 3 hrs. RESULTS AND DISCUSSION FT-IR spectrum of the uncalcined and calcined catalyst show a broad absorption between 300–3500 cm–1 corresponding to – OH group and NH4 group present in the uncalcined sample, which is completely converted to a sharp band around 3490 cm–1 after calcinations. Similarly, the bands corresponding to SO42– appeared at 1010, 1100, 1430 cm–1 and C = C around 1750, 1800 cm–1 are V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 131–134 (2015)

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absent in the calcined sample. In addition, -OH band around 3450 cm–1 and 1650 cm–1 correspondingly for stretching and bending vibrations in the calcined sample shows the availability of surface hydroxyl groups. Presence of an intense absorption around 790 cm–1 is due to the formation of tetrahedral M-O-M vibrations. UV-DRS spectrum of Nickel Aluminate shows the presence of absorption at 510 nm and 820 nm and is corresponding to the presence of Ni2+ in the tetrahedral vacant sites of surface spinel structure. Further, absence of absorption around 420 nm and 720 nm revealed the absence of the NiO phase. Powder XRD pattern of the product presented in Figure 1 exactly matches with the standard JCPDS file (File No: 10–341) corresponding to NiAl2O4. Absence of individual diffractions corresponding to NiO and Al2O3 in the pattern reveals the formation of a phase pure nickel aluminate. Peak broadening observed might be due to the poor crystalline nature of the material, since the complete crystallization of Nickel Aluminate observe only after 700°C. SEM image of the catalyst (Figure 2) show a flake like morphology of almost uniform distribution with pores on the surface. These pores are responsible for the better catalytic activity of the material towards acylation.

80

Intensity

60

40

20

0 10

20

30

40

50

60

70

80

2θ (Degrees) Fig. 1: Powder XRD Pattern of NiAl2O4

Nitrogen adsorption –desorption isotherm is of Type-IV in nature which corresponds to the mesoporous nature of the material. Pore size distribution calculated by BJH method is distributed between 6 and 50 nm and the maximum number of pores having the pore diameter of 9 nm with maximum pore volume (0.002 cm3/g), which will highly enhance the catalytic reactivity of the material. Surface area of the catalyst is found to be 150.7755 m2/g, which is higher than the already reported Nickel Aluminate catalyst (137 m2/g) [4].

Preparation and Characterisation of Nickel Aluminate—A Solid Acid Catalyst

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Fig. 2: SEM Image of NiAl2O4

Catalytic Activity Catalytic activity of Nickel Aluminate towards acylation of Anisole is optimised by varying parameters like catalyst quantity, nature of solvent and reaction temperature. Initially, 1mM anisole and 100 mg of the catalyst were refluxed with stirring in presence of 0.2 mL of Acetic Anhydride at 140°C. Progress of the reaction was monitored by thin layer chromatography. Complete formation of ortho acetyl anisole is observed within 30 minutes of the progress of the reaction. Optimisation of the catalyst quantity is carried out with varying catalyst amount from 0 mg to 200 mg. From the result, it is observed that, there was no reaction in the absence of the catalyst, 86.3% yield was obtained with 50 mg and there was no appreciable change in the isolated yield of the product by increasing the catalyst quantity from 100mg to 200 mg (91.3% and 92.0%). Hence the amount of catalyst for the acylation reaction is fixed as 100 mg. Effect of reaction temperature on the progress of the catalytic reaction is studied by fixing the catalyst quantity as 100 mg and varying the reaction temperature for Room Temperature (25°C) to 160°C. In the room temperature and at 50°C, there was no reaction even after 8 hrs of the reaction time. Though the reaction proceeded from 100°C to 120°C, the yield of the product isolated was poor. At 140°C, the reaction rate was faster and the acylation of anisole has completed within 30 minutes of the progress of the reaction and the yield was 90.5%. Further increase in temperature did not influence rate effectively and hence the reaction temperature was fixed as 140°C. Generally nature of the solvent and its properties influence the reaction rate and selectivity of the reaction very much in the case of liquid phase reactions. Hence, for the optimization of catalyst quantity and the reaction temperature, the acylating agent Acetic Anhydride itself acted as a solvent. But to know the effect of solvent on the reaction, various chlorinated solvents were tested by adding 2 mL of the solvent along with the reaction mixture and the results are presented in the table. There was no improvement in the yield of the product and the results revealed that the presence of solvent is not necessary for the complete acylation reaction. Similar results were observed for the acylation of anisole inpresence of arene sulphonic acid modified SBA-15 catalyst [5]. Hence the reaction was carried out in the absence of any chlorinated solvents.

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CONCLUSION Nickel Aluminate catalyst was prepared by hydrothermal method and characterised by various techniques. Prepared catalyst was used for the acylation of anisole in the absence of the solvent and it was found that 100 mg of the catalyst is sufficient for the acylation of 1mM anisole in 30 min of reaction time. REFERENCES [1] [2] [3] [4] [5]

Furstner, A., Voigtlander, D., Schrader, W. and Giebel, D., Reetz, Org. Lett., 2001, 3, 417–420. Gmouth, S., Yang, H.L. and Vaultier, M., Org. Lett., 2003, 5, 2219–2222. Fillion, E., Fishlock, D., Wilsily, A. and Goll, J.M., J. Org. Chem., 2005, 70, 1316–1327. Heracleous, E., Lee, A.F., Wilson, K. and Lemonidou, A.A., J. Catal., 2005, 231, 159–171. Juan A. Melero, Rafael van Grieken, Gabriel Morales and Vanesa Nuno, Catal. Commun., 2004, 5, 131–136.

Comparison of Pure CdS and Mg Doped CdS Films with Chemical Bath Deposition for Solar Cell Applications S. Rajathi, K. Selvaraju1 and K. Kirubavathi1 Department of Physics, Thanthai Hans Roever College, Perambalur 1 Department of Physics, Government Arts College, Ariyalur E-mail: [email protected]

ABSTRACT The pure CdS and Mg doped CdS films were grown on glass substrates using chemical bath deposition (CBD) technique. The Pure bath containing cadmium chloride (CdCl2) and thiourea (CS(NH2)2). The Mg:CdS bath containing cadmium chloride (CdCl2), thiourea (CS (NH2)2) and magnesium sulfate (MgSO4.H2O). Structural properties of the obtained films were studied by X-ray diffraction analysis. The structural parameters such as crystallite size, dislocation density, micro strain and number of crystallite per unit area have been evaluated. The optical properties have been studied in the range of wavelength 350–1100nm from the measurements of the optical transmittance (T). The optical band gap values of the thin films were calculated using the equation, relating absorption coefficient with the wavelength. The plotted graphs show the optical characteristics of the film which varied with the wavelength and the photon energy. The optical conductance and band gap indicated that the film is transmitting within the visible range. The films deposited with CBD technique are good conditions, especially for Solar Cell applications. Keywords: Chemical Bath Deposition, CdS, Mg:CdS, X-ray Diffraction, Optical Transmittance, SEM.

INTRODUCTION Chemical bath deposition (CBD) is known to be a simple low temperature, low cost and inexpensive large area deposition technique [1]. CdS is a wide band gap semiconductor, which is used as an efficient window layer for the fabrication of substrate type solar cell structure due to its high transmitivity and low resistivity [2,3]. For the application of CdS thin films in solar cells, it is necessary to have layers with the following characteristics: i) uniformity, ii) transparency and iii) crystalline. CdS have been used as a window material in high efficiency thin film solar cells based on CdTe and Cu(In,Ga)Se2 (CIGS) [4,5]. It has also been used in other applications including electronic and opto electronic devices [6]. Although in other techniques have been used in the deposition of CdS, CBD is known to enhance the performance of cadmium sulfide window used in solar cell applications [7, 8]. Varies techniques such as, evaporation [9], spray [10], sputtering [11], electrodeposition [12] and CBD [13–16] has been to grow this material. Cadmium Sulphide is doped with Mg the effect of its concentration on optical and structural properties is outlined. In this paper, for optimizing the film growth condition and obtaining good quality thin films for device application, XRD, UV-VIS V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 135–140 (2015)

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spectrrophotometer and SEM analysis of chemiically depositeed CdS, and Mg:CdS M thin films f have beeen reportted.

EXPE ERIMENTA AL DETAILS S The separately s preepared CdS annd Mg:CdS films f using glass g substratee. The CdS thhin films werre deposited onto glass slides from m an aqueouss solution cheemical bath containing c 0.001 M cadmium m M thiourea. The T Mg:CdS thin films were w depositedd onto glass slides from an a chloride and 0.05M hemical bath containing 0..01 M cadmiuum chloride, 0.05 M thiouurea and 0.25M M aqueoous solution ch magnnesium sulfaate. The bath was stirred duuring in orderr to assure a homogeneous h distribution of o the reagents at 85°C C. A uniform yellowish film m with the thhickness of CddS 234 nm annd Mg:CdS 3225 0 min having good g adherentt property. Theen the film waas dried in air. nm waas obtained 80 RESU ULTS AND DISCUSSIO D N XRD Analysis X-rayy diffraction stu udies were carrried out at room temperatuure as shown inn Figure 1(a) and 1(b). Som me structuural parameteers such as cryystallite size and a number and a strain calcculated from XRD X data. Thhe diffracction peaks ap ppear enlargedd by a low grrain size and/oor a thin sampple presentingg a broad noissy backgground. The Sccherrer formuula was used foor the calculattion of the cryystallite sizes, which is giveen by thee following forrmula [17]: D=

Kλ β cos θ

... (11)

Were K is constant,, β is FWHM in radians, λ is i the wavelenngth of X-ray used, u θ is the Bragg angle. K 0 for the caalculations. Inn addition, thhe dislocation density (δ), the number of o value is taken as 0.9 mined using thheir XRD datta. crystaallites per unitt area (N) andd strain of the films (ε) [18], were determ The peak p appears at a 37.16°, whiich can be asssigned to the (102) plane of o the CdS heexagonal phase. Usingg the size of the t crystallitees (D) = 45.67 nm, dislocaation density(δ) = 4.78 × 1014 (lines/m2), numbeer of crystallites per unit suurface area(N) = 1.88 × 10016 (m–2) and strain(ε) s = 0.776 × 10–3 in thhe films has been deterrmined. It is innteresting to note n that irresppective of the chemical bathh, the grain sizze m thickness. smalleer and the defeects like disloccation densityy and strain in the films increease with film

Fig. 1(a a): X-Ray Diffrraction of CdS thin Film ms

Fig. 1(b): X-Ray Diffractionn of Mg:CddS thin Films

Comparison of Pure CdS and Mg Doped CdS Films with Chemical Bath Deposition

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The peak appears at 25.84º and 76.36°, which can be assigned to the (111) and (105) plane of the Mg:CdS hexagonal phase. Using the size of the crystallites (D) = 9.37 nm, dislocation density (δ) = 1.13 × 1016 (lines/m2), number of crystallites per unit surface area (N) = 1.3 × 1017 (m–2), and strain(ε) = 3.67 × 10–2 in the films has been determined. This may be due to the improvement in crystalline in the films with film thickness.

Morphology The surface morphology of the CdS and Mg:CdS films were analyzed by scanning Electron microscopy (SEM). Figure 2(a) and 2(b) shows the SEM micrographs of the CdS and Mg:CdS films at different magnitudes. The grain size of the film CdS and Mg:CdS(1 μm–10 μm) was measured from SEM photograph by keeping the photograph under travelling microscope having high accuracy. Optical Studies The optical transmission spectra of CdS and Mg:CdS films shown in Figure 3. The CBD CdS films present high transmission (70–80%) in the visible range. The spectra depict a sharp fall in transmission near to fundamental absorption, which is identification for the good crystallinity of the films. The oscillatory nature of the transmission spectra observed the films are attributed to the interference of light transmitted through the thin film and the substrate. CdS thin film can be considered good for use as a visible transmitting thin film since the range of band gap for visible transmitting film is 1.5 eV. The Mg:CdS Optical transmission was performed in the wavelength range 350–1100 nm using UV spectrometer. The optical parameters such as absorption coefficient, extinction coefficient and band gap are estimated in Mg:CdS thin films were plotted and the straight line portion is extrapolated to cut the x-axis which gives the band gap. In Figure 4 CdS films, the band gap (Eg) values can be calculated by plotting (αhυ)2 axis: Eg = 2.51 eV (reported 2.42 eV). The absorption coefficient (α) = 0.15x105cm–1(λ = 500 nm) and extinction coefficient (k) = 0.0597(λ = 500 nm) are calculated. The band gap explained in terms of the smaller grains in nanometer scale present in as deposited layers. Absorption coefficient values associated with the strong absorption values associated with the strong absorption region of the films were calculated. Calculated values are of the order of 105 cm–1 in the strong absorption region.

Fig. 2(a): Scanning Electron Micrograph of CdS thin Films

Fig. 2(b): Scanning Electron Micrograph of Mg:CdS thin Films

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Fig. 3: Trannsmission Specctrum of CdS annd Mg:CdS thinn Films

Fig. 4: Plots of o (αhυ)2 vs. Photon Energy off CdS and mg:C CdS Films

Fig. 5: Refractive R Index as a Function of o Photon Energgy for CdS and Mg:CdS thin Films

Comparisoon of Pure CdS and a Mg Doped CdS C Films with Chemical C Bath Deposition D

1339

Fig g. 6: σelec as a Function of Photton Energy for CdS C and Mg:CddS thin Films

Inn Figure 4 Mg:CdS, the baand gap(Eg) values v can be calculated byy plotting (αhhυ)2 axis: Eg = 5 2.3eV V. The absorption coefficiennt (α) = 0.27 × 10 cm–1 (λ = 500 nm) andd extinction coefficient (k) = 0.10888 (λ = 500 nm m) are calculateed. It was obsserved that thee band gap deccreases with inncreases in film m thicknness and incrrease in the ion concentraation in thin films. Usingg the calculaated absorptioon coefficient values, the type of trransition assocciated with baand structure of CdS and Mg:CdS M can be b 9] and the elecctrical conducttivity can alsoo be estimatedd by optical meethod using thhe identified using [19 relatioon, σe =

2λσop α

… (22)

The recorded trransmission sppectrum of CddS and Mg:CddS shows the lower l cutoff wavelength w 3225 d a wide transpparency in thee entire visiblee region whichh makes the suuitable materiaal. nm annd 350 nm and From the recorded absorption sppectra, the opttical constants of CdS andd Mg:CdS calcculated and thhe a a function of photon ennergy is plottted (Figure 5 and 6). It is variatiion of opticaal constants as interesting to note that t the inclussion of materiial CdS and Mg:CdS M has inncreased the refractive r indeex ecreased the electrical e cond ductivity of the e mater. and de

CONCLUSIONS This wok w has clearrly presented how CdS andd Mg:CdS thiin film was grown g using solution s growtth techniiques and how w the effect of o the solid staate propertiess on spectral absorbance a annd transmissioon were obtained. o Thee CBD grown CdS and Mgg:CdS layers under u given deeposition condditions producce hexaggonal plane. SEM S of film showed irreguular distributiion of particlees with the grain sizes. Thhe opticaal band gap off the CdS film is 2.51 eV forr this band gapp deciding factor for the appplication of thiin films. It can be sug ggested for thee application in i solar energyy technology. The optical band b gap of thhe 3eV. SEM off film showed irregular disttribution of particles with the t grain sizees. Mg:CdS film is 2.3 firmed the morphological sttructure of Mgg:CdS thin fillms and it was observed that SEM analysis confi o Mg ion CddS increased the size of the t grain andd morphologyy changed in a the dooping level of signifi ficant manner. The investigaation revealedd that Mg dopping CdS thin films have suuitable structurre

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as well as optical parameters in the view of solar cell applications. The Mg:CdS low electrical conductivity (102 (Ωcm–1)) show the semiconducting nature of the material. The high transmission, low absorbance, low reflectance and low refractive index of CdS and Mg:CdS in the UV-VIS region make the material a prominent one for antireflection coating in solar thermal devices.

REFERENCES [1] Khallaf, Hani; Oladeji, Isaiah O.; Chai, Guangyu and Chow, Lee, Thin Solid Films. 516 (2008), 7306. [2] Chopra, K.P. and Dav, S.R., Thin Films Solar Cells, New York, 1979, p. 424. [3] Mitchell, K.W., Eberspecher, C., Enmer, J. and Pier, D., Proc, 20th IEEE, Isc, Photovoltaic spi, conf, 198, p. 1384. [4] Oladeji, I., Chow, L., Ferekides, C., Viswanathan, V. and Zhao, Z., Sol. Energy Mater. Sol. Cells 61(2000), 203. [5] Contreras, M. and Ramanathan, M., Thin Solid Films. 403/404(2002), 204. [6] Davis, A., Vaccaro, K., dauplaise, H., Waters, W. and Lorenzo, J., J. Electrochem. Soc. 146 (1999), 1046. [7] Contreras, M., Egaas, B., Ramanathan, K., Hiltner, J., Swartzlander, A., Hasoon, F. and Noufi, R., Prog. Photovolt: Res. Appk. 7(1999), 311. [8] Wu, X., Keane, J., Dhere, R., Dehart, D., Albin, D., Duda, A., Gessert, T., Asher, S., Levi, D. and Sheldon, P., Proceedings of the 17th European Photovoltaic Solar Energy Conference, Munich, Germany, October 22–26 (2001), 995. [9] Dona, J.M. and Herrero, J., J. Electrochem. Soc. 144(1997), 4091. [10] Oliva, A.I., Castro-Rodriguez, R., Solis-Canto, O., Sosa, Victor, Quintana, P. and Pena, J.L., Appl. Surf. Sci. 205(2003), 56. [11] Rafffaella, R.P., Forsell, H., Potdevin, T., Fridefeld, R., Mantovani, J.G., Bailey, S.G., Hubbard, S.M., Gordon, E.M. and Hepp, A.F., Sol. Energy Mater. Sol. Cells., 57(1999), 167. [12] Ramaiah, K. Subba and Raja, V. Sundara, Sol. Energy Mater. Sol. Cells. 32(1994), 1. [13] Pouzet, J., Bernede, J.C., Khellil, A., Essadi, H. and Benhida, S., Thin Solid Films. 208 (1992), 252. [14] Lanning, B.R. and Armstrong, J.H., Int. J. Sol. Energy. 12(1992), 247. [15] Kaar, I., Pandya, D.K. and Chopra, K.L., J. Electroche. Soc. 127(1980), 943. [16] Lincot, D. and Ortega, R., J. Electrochem. Soc. 139(1992), 1880. [17] Ding, J., Cheu, H., Zhao, X. and Ma, S., J. Phys. Chem. Solids. 71(2010), 346. [18] Das, R. and Kumar, Rajesh, Materials Research Bulletin, 47(2012), 239. [19] Tauc, J., Amorphous and liquid semiconductors, Plenum press, New York, 1974, p. 159.

Electrochemical Synthesis of P-Type Copper Oxides C.V. Niveditha, M.J. Jabeen Fatima and S. Sindhu Department of Nanoscience and Technology, University of Calicut, Kerala E-mail: [email protected]

INTRODUCTION` Copper oxide is a low cost, non toxic, narrow band gap metal oxide [1]. Oxides of copper crystallizes mainly in two forms, cuprous oxide (Cu2O) and cupric oxide (CuO) [2,1]. Cuprous oxide is a direct bandgap [1] and cupric oxide is an indirect band gap [1] metal oxide. These metal oxides exhibits interesting properties suitable for catalytic [3], electrochromic [4], electrochemical [4], photoelectrochemical [5] and photovoltaic application [4]. Due to the narrow band gap (Cu2O - 1.9 2.2eV and for CuO is 1.2 – 1.7eV) it has high potential in photovoltaic and photoelectrochemical applications. Commonly copper oxide films have been synthesized by high temperature thermal oxidation of copper metal [6] that limits the control over the interfacial features like surface area, particle size, and grain boundaries etc, which affect the optical and electrochemical properties. Hence the present study focus on electrodeposition method [7] which is an attractive method for thin film synthesis under low temperature condition. The efficiency of electronic and charge transfer mechanism between the nanoparticles or the nanoparticles and the adjacent layer depends highly on the shape and size of the particles participating in the process. This highlights the significance of deposition of size and shape controlled nanostructures by electrochemical deposition. EXPERIMENTAL METHOD Electrodeposition of copper oxide is done using three electrode system, where cleaned FTO is used as the working electrode, platinum wire as counter electrode and Ag/AgCl as reference electrode. The Cu2O is deposited on FTO substrate under neutral pH at -0.25 V from the solution containing CuSO4 and KNO3 to get a yellow coloured film. CuO is deposited from solution containing CuSO4 and KNO3 under acidic pH at -0.6V to obtain a black coloured film. Figure 1 shows the photographs of the obtained yellow and black coloured films of copper oxides.

Fig. 1: Photographs of Cu2O and CuO Films V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 141–144 (2015)

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RESULT AND DISCUSSION The crystallinity of the deposited films is analyzed using grazing angle X-ray diffraction (GIXRD). Figure. 2 depicts the XRD spectra of the deposited films and is compared with standard JCPDS files 78–2076, 80–1917, which corresponds to cubic and monoclinic crystal structure respectively for cuprous and cupric oxide.

Fig. 2: XRD Spectra of Cu2O and CuO Films Compared with Standard JCPDS

Figure 3 depicts the morphology of the film obtained from SEM analysis. The average size of Cu2O is 75 nm and that of CuO is 93 nm. The morphology of Cu2O is square shape and that of

CuO is spherical shape.

Fig. 3: SEM Image of Cu2O and CuO Films

***

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Optical properties of the films are analyzed by using UV-Visible spectroscopy. The absorption spectra and Tauc plots for Cu2O and CuO are shown in Figure 4. The band gap is estimated from the Tauc plot and the obtained values are 2.43 eV and 1.73 eV respectively for Cu2O and CuO.

Fig. 4: UV-Visible Spectra and Tauc Plot of Cu2O and CuO Films

The electronic properties of the films are studied using hall measurement system. From this measurement both Cu2O and CuO are p-type semiconductors with conductivity of 11.03 Scm–1 and 15.30 × 102 Scm–1 respectively. Figure 5 depicts the Nyquist plots obtained from electrochemical impedance (EIS) analysis of copper oxides, which measure the interfacial resistance between the electrode and electrolyte in the presence and absence of light. This analysis confirms the photo activity of copper oxide.

Fig. 5: Nyquist Plots of Electrodeposited Cu2O and CuO Films

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CONCLUSION p-type copper oxides were synthesized through electrodeposition technique. The band gaps of both copper oxides are narrow ie; 2.43 eV and 1.73 eV for Cu2O and CuO respectively. The electrochemical impedance analysis shows that the copper oxide thin films are photoactive. ACKNOWLEDGEMENT Authors Niveditha C V and Jabeen Fatima acknowledge CSIR for financial assistant in the form of Senior Research Fellowship. Sindhu S acknowledges Kerala State Council for Science Technology and Environment (KSCSTE), Govt.of Kerala, and Council of Scientific and Industrial Research (CSIR), Govt. of India for financial assistance. Support obtained from Satyabhama University, Chennai and NIT Calicut for GIXRD and SEM analysis are greatly acknowledged. REFERENCES [1] Kari, E.R.B. and Kyoung-Shin, C., Electrochemical synthesis and characterization of transparent nanocrystalline Cu2O films and their conversion to Cuo films, ChemComm, 3311–3313, 2006. [2] Samarasekara, P., Characterization of low cost p-Cu2O/n-CuO junction, GESJ: Physics No. 2(4) ISSN1512-1461, 2010. [3] Yongqian, W. et al., Controllable fabrication nanostructured copper compound on Cu substrate by onestep route, RSC.Adv., 1–17, 2015. [4] Ahmad, S.Z. et al., Nanostructured copper oxide semiconductor: a perspective on materials, synthesis method and applications, J. Mater. Chem. C., 2, 5247, 2014. [5] Chia-Yu, L. et al., Cu2O/NiOx nanocomposite as an inexpensive photocathode in photoelectrochemical water splitting, Chem. Sci., 2012. [6] Kasim, U.I. Et al., Effect of oxidation temperature on the properties of copper oxide thin films prepared from thermally oxidised evaporated copper thin films, IOSR-JAP, 3, 61–66, 2013. [7] Rachel, O., Usha, R., Sajeeviraja, Characteristics of electron beam evaporated and electrodeposited Cu2O thin films- comparative study, Int. J. Electrochem. Sci., 7, 8288 – 8298, 2012.

Application of Gel Electrolyte in Dye Sensitized Solar Cells P. Nijisha, N.M. Bhabhina and S. Sindhu Department of Nanoscience and Technology, University of Calicut, Kerala E-mail: [email protected]

INTRODUCTION DSSC have received great attention owing to their low production cost and high efficiency [1,2]. The certified record efficiency of DSSC is 12–13%. DSSC consist of a photo anode which is a dye sensitized semiconductor film coated on a transparent conducting oxide layer, a counter electrode usually FTO coated with a catalytic material and electrolyte which includes a redox couple usually I– /I3– system and a suitable solvent. In DSSC electrolyte is the medium for transportation of charges between the two electrodes and acts as a source for dye regeneration [3]. The long term stability of the devise strongly depends on the electrolyte component [4]. The highest efficiency reported in DSSC was by employing liquid electrolyte. But there are some practical impediments when using this liquid electrolyte like leakage while sealing and volatilization of the solvent, desorption and photodegradation of the attached dye, corrosion of the counter electrode etc., which prevent it from its application and commercialization [4,5]. So as an alternative to liquid electrolyte, solid state electrolytes and quasi solid state electrolytes (gel electrolyte) were introduced. Though solid state electrolyte seems to be an ideal material for DSSC, the efficiency was not up to expectation [6]. This might be due to poor interfacial contact and poor charge carrier mobility. When coming to gel electrolyte all the problems related to liquid and solid state electrolyte can be resolved. It remains as quasi solid at room temperature and as a highly viscous liquid at high temperatures. So it has got both the cohesive property of solid as well as diffusive transport property of liquid [7,8]. In the present work a polymer based gel electrolyte is synthesized and its behavior in the performance of dye sensitized solar cell is studied by using two different photoanode material – TiO2 and ZnO. EXPERIMENTAL Gel Electrolyte Synthesis Polyvinyl alcohol is used as the polymeric matrix. Gel electrolyte is prepared by adding adequate amount of polymer, KI and I2 to dimethyl sulfoxide. The resulting mixture is heated to 2 hrs and stirred continuously to obtain the gel. Assembling of Quasi Solid State Dye Sensitized Solar Cell The nanocrystalline TiO2 photo anode was fabricated by doctor blading TiO2 paste on FTO substrate. The film was air dried and sintered at 450° c for half an hour. The sintered sample is then cooled to room temperature and is dipped in the dye solution for 24 hrs. The dye loaded sample is then air dried and sealed. Counter electrode is made by electrodepositing Pt on FTO surface. The two electrodes are V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 145–148 (2015)

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then kept face to face with gel electrolyte in between to obtain a sandwich structure and is then clamped tightly.

RESULT AND DISCUSSION Gel Characterization Figure 1 shows the FT-IR of pure PVA and PVA based gel electrolyte. The presence of broad peak at 3416 shows the inter-molecular hydrogen bonding. In PVA-G the intensity of the peak is found increased and this is because of extensive hydrogen bonding between the polymeric chains due to its complete expansion. The peak at 2914 cm– 1 shows the –CH- stretching vibration. Peak at 1654cm–1 is for terminal vinyl group. Peaks at 1783 cm–1 and 1806cm–1 corresponds to ester group present. 1315 cm–1 and 1434 cm–1 peaks corresponds to S-O stretching. 1024 cm–1, 1083 cm–1, 1186 cm–1 shows the C-O vibration of PVA. PVA 80

1048 1445

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XRD spectra of gel electrolyte, pure PVA, KI, and I 2 are shown in Figure 2. Diffraction peak at 2θ − 40.76 is ascribed to pure PVA. Diffraction peak at 2θ - 21.67, 30.80, 54.98 and 24.62, 25.07, 29.04 is for pure KI and I2 respectively, shows the crystalline nature of the ionic salt. Amorphous peak is observed for polymer gel electrolyte which shows the complete dissolution of the ionic salt and also increased liquid electrolyte uptake by the matrix. 1000

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Fig. 2: XRD of Pure I2, KI,PVA and Polymer Gel Electrolyte

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Cell Characterization The current-voltage characteristics and nyquist plot of the DSSCs based on polymer gel electrolyte is carried out with two different photoanode semiconductor materials-TiO2 and ZnO. The table below summarizes the best values of their photovoltaic parameters.

Fig. 3: (a) Jsc-Voc Curve, and (b) Nyquist Plot of the Cell Table 1: Photovoltaic Parameters of TiO2 and ZnO based DSCs with Gel Electrolyte Photoanode Material

Jsc(mA/cm2)

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Eff(%)

TiO2

1.21

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The charge transfer or transport behaviour of the cell is measured by taking the electrochemical impedance spectroscopy. The three semicircle from left to right gives the electrochemical behaviour at the Pt counter electrode, TiO2/dye/electrolyte interface and Warburg diffusion.

CONCLUSION PVA based polymer gel electrolyte was synthesized. DSSC was fabricated with two different photoanode materials to study the performance of the cell. Photovoltaic studies show that the gel goes good with TiO2 based solar cell with an overall efficiency of 2.05%. ACKNOWLEDGEMENT The authors would like to acknowledge UGC and CSIR for their financial assistance. Sindhu S thanks Kerala State Council for Science Technology and Environment (KSCSTE), Govt.of Kerala, and Council of Scientific and Industrial Research (CSIR), Govt. of India for funding in the form of research projects. REFERENCES [1] O’Regan, B. and Gratzel, M., Nature, 353 (1991), 737–740. [2] Lee, Yuh-Lang; Shen, Yu-Jen and Yang, Yu Min, A hybrid PVDF-HFP/nanoparticle gel electrolyte for dye-sensitized solar cell application, Nanotechnology, 19 (2008), 455201. [3] Nogueira, A.F., Longo, C. and Paoli, M.A. De, Polymers in dye sensitized solar cells:overview and perspectives, Coordination Chemistry Reviews, 248 (2004), 1455–1468.

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[4] Lan, Jo-Lin; Wei, Tzu-Chien; Feng, Shien-Ping; Wan, Chi Chao and Cao, Guozhong, Effects of iodine content in the electrolyte on the charge transfer and power conversion efficiency of dye sensitized solar cells under low light intensities, The J. Phys. Chem. C, 2012 116, 25727–25733. [5] Lee, Kun Seok; Jun, Yongseok and Park, Jong Hyeok, Controlled Dissolution OfPolystyrene nanobeads: Transition from Liquid Electrolyte to Gel Electrolyte, Nano Lett. 2012 12, 2233–2237. [6] Tsai, Chih-Hung; Lu, Chun-Yang; Chen, Ming-Che; Huang, Tsung-Wei; Wu, Chung-Chih and Chung, YiWen, Organic electronics, 14(2013), 3131–3137. [7] Kubo, Wataru; Murakoshi, Kei; Kitamura, Takayuki; Yoshida, Shigeo; Haruki, Mitsuru; Hanabusa, Kenji; Shirai, Hirofusa; Wada, Yuji and Yanagida, Shozo, Quasi-solid-state dye-sensitized TiO2 solar cells:Effective charge transport in mesoporous space filled with gel electrolytes containing iodide and iodine, J.Phys.Chem. B 2001, 105, 12809–12815.

Hydrothermal Synthesis of Nanosized (Fe, Co, Ni)-TiO2 for Solar Hydrogen Generation K.R. Anju and T. Radhika Centre for Materials for Electronics Technology [C-MET] (Scientific Society under M/o Communications and Information Technology, India) M.G. Kavu, Athani, Thrissur, Kerala E-mail: [email protected]

ABSTRACT In this work, nanosized TiO2 and 0.01 (Fe, Co, Ni) doped TiO2 were prepared through hydrothermal method and characterized using X-ray diffraction, Raman, DR UV-Vis spectroscopy and TEM. The powder X-ray diffraction patterns of all the materials show crystalline anatase TiO2 with crystallite size in the range of 22–23 nm. Raman spectra show modes corresponding to anatase TiO2 which confirms the XRD data. The DR UV-Visible absorption spectra of 0.01 (Fe, Co, Ni)-TiO2 extends to the visible region (450–650 nm). TE micrographs and EDAX data confirms the nano size and presence of doped Fe within the TiO2. The extended absorption of these materials into the visible region provides the possibility for enhancing the photosensitive behavior of nanosized TiO2 materials for solar based hydrogen generation applications. Keywords: TiO2, Nano, Hydrothermal, Water-Splitting, Solar Hydrogen.

INTRODUCTION Photosensitive water splitting is one of the best routes for solar-hydrogen generation, that could contribute to the solution of both environmental and energy issues, known to be the future fuel [1–3]. Hydrogen (H2) is identified as an attractive candidate for the energy carrier of future, which replace fossil fuels. Photosensitive water splitting can be achieved at a theoretical minimum potential difference of 1.23 eV (visible light). In the development of new photosensitive materials, most of the investigations have focused on TiO2, which shows relatively high activity and chemical stability under UV light irradiation [4,5]. The major drawback of TiO2 lies in its ineffective use of visible light as irradiation source because of its wide band gap (3.2 eV). There is an urgent need to develop photo sensitive materials that can yield high activity under visible light irradiation too by modifying TiO2 or using other semiconductors. The doping of TiO2 is a promising route to extend the optical absorption to the visible spectral region [6]. Hydrothermal method is one of the unique methods for synthesizing nanosized materials with high purity, narrow particle size distribution, controlled morphology and very high crystallinity [7]. The incorporation of transition metal into TiO2 lattice is an important method to induce visible light photocatalytic activity. It was observed that cationic doping in TiO2 leads to decrease in band gap energy and enhancement of photo-activity upon sunlight [8]. In the present study, the doping of TiO2 with transition metals such as Fe, Co and Ni was done through hydrothermal route, which help to reduce the band gap and make it as a visible light active material. Thus this material could be used effectively for solar hydrogen generation by water-splitting. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 149–152 (2015)

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EXPERIMENTAL In a typical procedure, Titanium (IV) tetraisopropoxide (TIP) was added into dH2O (TIP::NH3 dH2O1:0.1:100) and kept for 15 min. stirring after adjusting pH with NH3. It is transferred into a teflon lined autoclave and kept at 453 K for 24 h in an oven. Precipitate obtained is centrifuged, dried at 343 K and calcined at 723 K. The same procedure was followed for the preparation of Fe, Co and Ni doped TiO2 with the addition of required amount of corresponding metal nitrate salts. RESULTS AND DISCUSSION The powder X-ray diffraction and Raman spectra of the prepared materials are shown in Figure 1 (a) and (b). (101)

2500

(204)

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Intensity (a.u.)

(211)

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Fig. 1: (a) XRD Pattern and (b) Raman Spectra of the Materials

The XRD pattern in Figure 1 (a) shows diffraction peaks corresponding to anatase phase of TiO2 with crystallite size of 20–23 nm as calculated by Scherrer equation. The doped TiO2 exhibits smaller sizes compared with those of pure TiO2, since Fe, Co, and Ni doping can suppress its crystal growth. Absence of any other peaks in the doped materials indicate that doped Fe, Co and Ni metals are uniformly dispersed into the anatase phase of TiO2. In Figure 1 (b) the observed distinct Raman active modes are characteristic of the anatase TiO2 phase assigned to Eg and B1g modes which confirm the XRD pattern [9]. The DR UV-Visible spectra and T-plot of the materials are shown in Figure 2(a) and (b) respectively. Band gap values are presented in Table 1. Table 1: Band Gap Energy of Materials Sl. No.

Material

Energy Band Gap (eV)

1.

TiO2

2.95

2.

0.01 Fe-TiO2

2.78

3.

0.01 Co-TiO2

2.63

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2.76

Hydrothermal Synthesis of Nanosized (Fe, Co, Ni)-TiO2 for Solar Hydrogen Generation

(a)

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(b)

Fig. 2: (a) DR UV-Vis Spectra and (b) T-Plot of the Materials

The band gap energy was estimated by plotting (αhν)1/2 as a function of the photon energy hν. The DR UV-Vis spectrum of TiO2 shows single intense broad absorption around 400 nm with band gap 2.95 eV, almost near to its typical band gap of 3.10 eV. The Fe, Co and Ni doped TiO2 shows red shift in the absorption onset value with reduced band gap as in Table 1. The observed shift of the absorption for the transition metals doped TiO2 indicates that Fe, Co and Ni doping is indeed effective in extending the optical response of TiO2 from UV to visible light range (450–650 nm). The results demonstrate that these transition metals doped TiO2 materials are very promising for hydrogen generation applications under solar light [10]. Figure 3 (a) and (b) shows the TEM images and EDAX of 0.01Fe-TiO2.

(a)

(b)

Fig. 3: (a) TEM Image and (b) EDAX of 0.01Fe-TiO2

The TE micrograph of 0.01 Fe-TiO2 shows that the particle size is about ~ 20 nm, the result of which is almost the same as that of XRD analysis. Thus hydrothermal method yields nanosized TiO2 materials in single step. In the EDAX pattern, the presence of Fe and Ti confirms the formation of FeTiO2 nanoparticles.

CONCLUSIONS Nanosized TiO2 and 0.01Fe-TiO2, 0.01Co-TiO2 and 0.01Ni-TiO2 were prepared by hydrothermal method. The powder X-ray diffraction patterns of all the materials show crystalline anatase TiO2 with

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crystallite size in the range of 22–23 nm which confirms through TE micrograph. In Raman spectra, modes corresponding to anatase TiO2 only observed which confirms the XRD pattern. Moreover, the DR UV-Visible absorption of 0.01 Fe-TiO2, 0.01 Co-TiO2 and 0.01 Ni-TiO2 extends to the visible region (red shift) with band gap of 2.67, 2.64 and 2.76 respectively. The extended absorbance of these transition metals doped TiO2 into the visible region provides the possibility for enhancing the photosensitive behavior of TiO2 materials for solar based hydrogen generation.

REFERENCES [1] Nowotny, J., Bak, T., Nowotny, M.K. and Sheppard, L.R., Int. J. Hydrogen Energy, 32 (2007), 2609– 2629. [2] Kudo, A., Int. J. Hydrogen Energy, 31 2 (2006), 197–202. [3] Minggu, L.J., Daud, W.R. Wan and Kassim, M.B., Int. J. Hydrogen Energy, 35 (2010), 5233–5244. [4] Kato, H., Asakura, K. and Kudo, A., J. Am. Chem. Soc., 125 (2003), 3082. [5] Suchanek, W.L. and Riman, R.E., Adv. Sci. Tech., 45 (2006), 184–193. [6] Naik, B., Martha, S. and Parida, K.M., Inter. J. Hydrogen Energy, 36 (2011), 2794–2802. [7] Dholam, R., Patel, N., Adami, A. and Miotello, A., Inter. J. Hydrogen Energy, 34 (2009), 5337–5346. [8] Cook, T.R., Dogutan, D.K., Recee, S.Y., Surendranath, Y., Teets, T.S. and Nocera, D.G., Chem. Rev., 110 (2010), 6474. [9] Ohsaka, T., Izumi, F. and Fujiki, Y., J. Raman Spectroscopy, 7 321 (1978). [10] Castro, A.L., Carvalho, M.R., Ferreira, M.D. and Jumas, L.P., J. Solid State Chem., 182 (2009), 1838–1845.

Facile Preparation of 3D-Interconnected Porous Metal Oxide Aerogels for Super Capacitors and Fuel Cell Applications Santhana Sivabalan Jayaseelan2, Kesavan Devarayan2 and Byoung-Suhk Kim1,2 1

Department of Organic Materials and Fiber Engineering, Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do 54896, Republic of Korea 2 Department of BIN Convergence Technology, Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do 54896, Republic of Korea

ABSTRACT In recent years, CNT based nanocomposites have been paid great attentiondue to their potential applications in sensors, catalysis, hydrogen storage and energy applications. Aerogels are the mesoporous solids and exhibits high surface area and porosity. Metal oxide aerogels having 3dimentional architecture are interconnected with metallic nano particles of mesoporous nature. In this work, we have prepared bimetal oxide/MWCNT nanocomposite aerogel by sol-gel approach. The structures of material are confirmed by X-ray diffraction and FE-SEM studies. It exhibits high surface area and porosity. Specific capacitance of the synthesized metal oxide/MWCNT nanocomposite aerogels is about 520 F/g. It also shows good electrocatalytic activity on ethanol oxidation and indicates excellent electrochemical sensing of dopamine at lower level detection of less than 200 µM.

INTRODUCTION In recent years nanocomposite materialshave attracted great attentionfrom both academic and industrial points of view due to the appealing possibility of synergetic properties exploiting the best of both components. Among them, CNT based nanocomposites have attracted great attention and interest due to their potential applications in sensors, catalyst, hydrogen storage, and energy applications. Aerogels are the emerging materials having three dimensionally cross-linked nanoparticles and exhibiting high porosity and high surface area. Usually aerogels are ultra-low weight materials. In this work, we report the electrochemical properties of the metal oxide/MWCNT aerogel nanocomposites. Experimental Section 3.0 wt% of nickel chloride hexahydrate and cobalt(II) chloride hexahydrate was dissolved in 10 ml DMF. Then, appropriate amount of gelling agent was added into the mixture of nickel and cobalt precursors, and allowed to form a gel. After few minutes, the mixture has been transferred into a wet gel. The prepared wet gel was washed three times with DMF and acetone respectively. After washing, the wetgel was washed by supercritical CO2. The supercritical dried aerogel nanocomposite was calcinated at 400°C under air for 4.0 hrs. The electrochemical properties of the prepared metal oxide/MWCNT aerogel nanocomposites were investigated. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 153–156 (2015)

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Application of Nanostructured Materials for Energy E and Envirronmental Technnology

RESU ULTS AND DISCUSSIO D N Figuree 1 shows the morphology of o the prepareed aerogel nannocomposite. FE-SEM F analyysisconfirmed a highlyy porous structure and thee high surfacee area of the sample. Thee crystalline structures s werre confirrmed by X-ray y diffraction teechnique. Thee diffraction peaks p were observed at 31°,, 37°, 59° annd 65°, corresponding c to the (222), (400), ( (422) and a (533) refleections of the NiCo N 2O4 crystal structure. In I additioon, the diffraaction peak at a 20° indicaates the preseence of carboon in the preepared sample, corressponding to th he (111) reflecttion, as seen inn Figure 2.

(400)

Fig. F 1: FE-SEM M Images of NiC Co2O4/MWCNT T Aerogel Nanoocomposites

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NiCoOx/C CNT 01-073-170 04

(442)

(222)

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60 40 20 10

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Fig. 2: 2 X-ray Diffracction Patterns off NiCo2O4/MW WCNT Aerogel Nanocomposite N es

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600 5mV 10mv 20mV

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Fig. 3: Cyclic Voltammetry Curves of NiCo2O4/MWCNT Aerogel Nanocomposites

The electrochemical characterization was conducted in three electrode cell with Versastat4 instrument. Figure 4 shows the cyclic voltammetry behavior of NiCo2O4/MWCNT coated on glassy carbon electrode in 0.5 M NaOH solution as electrolyte. From CV curves, it was found that the specific capacitance at the scanrate of 5.0 mV/s was 519 F/g. As expected, the specific capacitance was getting decreased as increasing scan rate. Moreover, this aerogel showed good electrocatalytic activity for ethanol oxidation fuel cell and also indicated better electrochemical sensing towards dopamine.

Fig. 4: EDX Analysis of NiCo2O4/MWCNT Aerogel Nanocomposites

Calculation for specific capacitance Sp = ∇V – Potential difference M – Mass of the active material A – Area of the curve

∇௏ ଶெ஺

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CONCLUSION In this work, we have prepared NiCo2O4/MWCNT aerogel nanocomposites by sol-gel approach, having thehigh porosity and high surface area. The formation of NiCo2O4crystalwas confirmed by X-ray diffraction studies and its exhibited polycrystalline in nature. The NiCo2O4/MWCNT aerogel nanocomposites exhibited high specific capacitance value at 5mV/s as 519 F/g. REFERENCES [1] Guo, Y.G., Hu, J.S. and Wan, L.J., Adv. Mater, 20 (2008) 2878–2887. [2] Tian, Z.Q., Jiang, San Ping, Liang, Y.M. and Shen, P.K., J. Phys. Chem., B 110 (2006), 5343–5350. [3] Shen, J., Hu, Y., Li, C., Qin, C. and Ye, M., Electrochim. Acta, 53 (2008), 7276–7280.

Synthesis and Studies of Carbazole Based (A-D-A) Polymers for Organic Solar Cell Applications Govindasamy Sathiyan, Ramasamy Ganesamoorthy, E.K.T. Sivakumar1, Rangasamy Thangamuthu2 and Pachagoundar Sakthivel Organic Chemistry Division, School of Advanced Sciences, VIT University, Vellore, Tamil Nadu 1 Centre for Nanoscience and Technology, Anna University, Chennai 2 Electrochemistry Materials Science Division, CSIR - Central Electrochemical Research Institute Karaikudi E-mail: [email protected]; [email protected]; [email protected]

ABSTRACT We have synthesized a new carbazole based (A-D-A) polymer, such as (2E,2'E)-3, 3'-(9-hexyl-9Hcarbazole-3, 6-diyl)bis(2-(5-methylthiophen-2yl) acrylonitrile (CN-PICTAN) bychemical oxidative polymerization method. The structure and properties of the polymer was characterized by 1H, 13C-NMR, CV, TGA, UV-visible and Emission spectra. The CN-PICTAN was showed high thermal stabilty of 356 ºC, deeper-lying HOMO of -5.23 eV, broad absorption range 340–590 nmand their optical band gap was showed 2.1 eV these results were measured by TGA, cyclic voltammetry and UV-Vis measurements, respectively. Organic photovoltaic device will be fabricate with the following configuration ITO/PEDOT:PSS/donor:PCBM/LiF/Al, CN-PICTAN used as an electron donors. Keywords: Carbazole, Low Band Gap, Organic Solar Cell.

INTRODUCTION Now a day’s more attention is drawn towards bulk heterojunction solar cell approach (BHJ PSCs) [1– 7]. The main important of BHJ solar cell approaches the mixture of donor (polymers or small molecules) and acceptor (fullerene derivatives). Previously, it has been reported that the maximum Power Conversion Efficiency (PCE) was achieved up to 5.1% when donor moiety poly (3hexylthiophene) (P3HT) blended with acceptor [6, 6]-phenyl-C61-butyric acid methyl ester (PC61BM) derivatives [8]. Moreover, the donor material can be designed to improve the properties of OPVs such as hole transport character with deeper-lying HOMO (Highest Occupied Molecular Orbital) energy level and low band gap.Various research groupsare focus on the development of fused ring system derivatives such as fluorenes, carbazole, cyclopentadithiophene, and dibenzothiophene as donor moieties. Among these donor moieties, carbazole based polymers possesses low oxidation potential and it has ability to generate excitons and broad absorption range [9,10]. Further, few research reports reveals that carbazole based donor molecules shows bettercapability to deliver deep-lying HOMO energy levels, high Voc (open circuit voltage), high hole mobility and showed maximum PCEs of 6.1% [11]. The electron donating strength of carbazole is more; because of it can be easily functionalized with various alkyl groups which can improve the solubility and stability of polymers. Nakamura et al., was reported a high molecular weight Poly(3,6-carbazole)by Yamamoto polymerization method [12]. A facile approach to obtain low band gap polymers is through V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 157–162 (2015)

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incorporation of electron rich unit (as donor) and electron deficient unit (as acceptor) forming a donor acceptor (D-A) structure. More significant attachments of cyanovinylene spacer’smoiety were previously reported. In this work, we are going to report 3, 6-carbazole based polymer, this polymer contain carbazole (donor) as the center core, two thiophene derivatives (donor) unit attached through a cyanovinylene (acceptor) linker.The thiophene attachments willextent the π-conjugation and increaseabsorption. The polymer was synthesized via oxidative polymerization with FeCl3. Until now, other direct synthetic pathways toward low band gap materials were either very difficult to handle or yielded relatively low molecular weight polymers. On the other hand, the FeCl3 method is a well-established method to polymerize thiophene like monomers and continues to be the most widely used and straight forward method to prepare polythiophene derivatives.

EXPERIMENTAL Synthesis of Polymer The poly ((2E, 2'E)-3, 3'-(9-hexyl-9H-carbazole-3, 6-diyl)bis(2-(5-methylthiophen-2yl) acrylonitrile) (CN-PICTAN) was prepared according to oxidative polymerization with FeCl3. The monomer (1.034, 2 mmol) was dissolved in dry chloroform (40mL) and added into the suspended anhydrous FeCl3 (2 equivalents) under nitrogen atmosphere. The resulting mixture was stirred at room temperature for 48 h. The solution was added drop wise into methanol with constant stirring and theprecipitates was filter and again re-precipitate by methanol and then consequently washed for 48 h by soxhlet extractions with methanol and acetone, after which the soluble fraction is collected with CHCl3 via extraction for 24 h. The CHCl3 solution is then concentrated, and precipitation into methanol yields the polymer as a brown powder. 1H NMR (CDCl3, ppm): 8.56 (s, 2H), 8.17 (d, 2H), 7.57(s, 2H), 7.47 (d, 2H), 7.39 (d, 2H), 7.30 (d, 2H), 7.1–7.0 (m, 2H), 4.35 (t, 2H), 1.94–1.826 (m, 2H), 1.38–1.34 (m, 6H), 0.89–0.87 (m, 3H).

Scheme 1: Synthesis of Polymer (CN-PICTAN)

RESULT AND DISCUSSION:THERMAL PROPERTIES The thermal stability of CN-PICTAN was studiedusing TGA and DSC techniques are shown in Figure 1 and 2.The TGA curve reveals degradation temperature (Td) at 356 °C with 5% weight loss

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159

indicating high thermal stability of CN-PICTAN. The glass transition temperature (Tg) was noticed at 275 °C while melting temperature (Tm) at 425 °C respectively, the CN-PICTAN showing amorphous structures.Earlier reports regarding polymers currently used in solar cell such as P3HT, fused ring systems derivatives shows thermal stability around at 400 °C [8,13,14]. Comparing to these polymers, CN-PICTAN polymer also exhibits capability to withstand high temperature conditions. Thus,these results prove that CN-PICTAN might act as a potential material for solar cell applications.

Fig. 1: TGA Curves of CN-PICTAN

Fig. 2: DSC Curves of CN-PICTAN

Optical Properties The absorption spectra of CN-PICTAN in chloroform solution are shown in Figure 3. Themaximum absorption peak of monomer and CN-PICTAN in solution was found to be almost similar.The maximum absorption peak of monomer and polymer showed at 392 and 412 nm respectively. Compare to monomer polymer showed broad absorption range of 350 to 600 nm. This UV spectra indicate that polymer have ability to absorb more light. The optical band gap (2.1 eV) of CNPICTAN was calculated from onset wavelength of optical absorption in solution. Previously, reportedreference donor P3HT UV-absorption spectra shows broad absorption range at 400 to 650 nm with maximumabsorptionpeak at 515 nm and the P3HT film due to strong interchain interaction [15, 16]. The fluorescence emission spectra (blue line) of the polymer exhibited strong luminescence maxima at 320–600 nm was recorded upon their excitation of maximum absorption value.

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Fig. 3: Normalized UV-Vis Absorption, PL Spectra of CN-PICTAN in CHCl3 Solutions

Electrochemical Properties The Cyclic Voltammetry (CV) was employed to determine the HOMO and LUMO energy level of the CN-PICTAN and the obtained CV spectra is shown Figure 4.The CN-PICTAN showed oxidation potential peak only, it indicate that p-type semiconductor nature. From that onset HOMO energy level of CN-PICTANwas calculatedusing above mention equation. The LUMO energy level was calculated from their optical band gap (2.1 eV)for UV-vis spectra. The HOMO energy level of the CN-PICTAN was very close to P3HT.The higher HOMO level of the polymer indicates the stronger intramolecular charge transfer effects.The importance of p-type materials with deep lying HOMO energy level improve hole transport property of the OPV applications [17]. The energy band gap diagram of the materials shown in Figure 5 suggests that synthesized CN-PICTAN well suitable for OPV applications.

Fig. 4: Cyclic Voltammograms of CN-PICTAN

Synthesiss and Studies off Carbazole Baseed (A-D-A) Polym mers for Organiic Solar Cell Appplications

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Fiig. 5: Band Gapp Diagram of CN-PICTAN

CONCLUSION In thiis study, a new n carbazole based ((2E E, 2'E)-3, 3'-(9-hexyl-9H-ccarbazole-3, 6-diyl)bis(2-(5 6 5methyylthiophen-2yll) acrylonitrilee) was syntheesized via chemical oxidattive polymerization methodd. The CN-PICTAN C showedbroadd absorption range in betweeen 340–590 nm and it haas high thermal stabiliity of 356°C. From F the onseet wavelength absorption thee optical bandd gap was calcuulated to be 2.1 eV. The T CN-PICT TAN showed deep lying HOMO energgy level of -5.23 eV. These results arre indicaates, the synth hesized CN-PICTAN well suitable fordoonor material in organic soolar cell devicce study.. ACK KNOWLEDG GMENTS This work w was su upported by VIT V Universitty for providiing laboratoryy facilitiesandd VIT SIF foor spectrral study. The characterizattion was donee by CECRI, Karaikudi. K Thhe financial suupported by thhe Ministry of Departm ment of Sciennce and Technnology (DST), India, under the Science annd Engineerinng ERB) NO. SB//FT/CS-185/22011. Reseaarch Board (SE REFE ERENCES [1] Cheng, Y.J., Yang, Y S.H. andd Hsu, C.S., Synthesis S of Conjugated C Pollymers for Orgganic Solar Ceell A Applications, Chemical C Review ws, 109(11), 5868–923, 2009. [2] Delgado, D J.L., Bouit, P.A., Filippone, F S., Herranz, H M. A. A and Martín, N., Organic Photovoltaics: P A Chemical Apprroach, Chemical Communicatioons, 46(27), 48553–65, 2010. [3] Taylor, T P., Sivoththaman, S. and Baroughi, M.F., Internatiional Journal off Green Energyy Cost-Effectivve, S Silicon-Based Solar S Cells : Material M and Teechnology Issuess, 37–41, 2007.. [4] Pochettino, P A., Atti Acad Linceei Rend, 15, 355, 1906. [5] Tang, T C.W., Tw wo-Layer Organnic Photovoltaicc Cell, Applied Physics Letterss. 48 183, 1986.. [6] Sakthivel, P., Song, S H. S., Chaakravarthi, N., Lee, L J. W., Gal, Y.-S., Hwang, S. and Jin, S.-H H., Synthesis annd Characterizatio on of New Indeeno [1, 2-B]Inddole-Co-Benzotthiadiazole-Bassed Π-Conjugatted Ladder Typpe P Polymers for Bulk Heterojunction Polymer Solar Cells, Polyymer, 54(18), 48883–4893, 20133. [7] Lin, L Y., Li, Y. and Zhan, X., Small Moleculee Semiconductoors for High-Effficiency Organnic Photovoltaiccs, Chemical Socieety Reviews, 41((11), 4245–72, 2012. [8] Ma, M W., Yang,, C., Gong, X., Lee, K. and Heeger, H A.J., Thhermally Stablee, Efficient Polyymer Solar Cellls W Nanoscalle Control of The With T Interpenetraating Network Morphology, Advanced A Functtional Materialls, 15(10), 1617–1622, 2005. [9] Jiaoli J Li., Andrrew C. Grimsdaale., Carbazole--Based Polymerrs for Organic Photovoltaic P Deevices, Chemical S Society Reviewss, 39, 2399–24110, 2010.

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[10] Hwang, D.H., Lee, J.D., Kang, J.M., Lee, S., Lee, C.H. and Jin, S.H., Syntheses and Light-Emitting Properties of Poly(9, 9-Di-N-Octylfluorenyl-2, 7-Vinylene) and PPV Copolymers, Journal of Materials Chemistry, 13(7), 1540, 2003. [11] Alem, S., Chu, T.Y., Tse, S. C., Wakim, S., Lu, J., Movileanu, R. and Gaudiana, R., Effect of Mixed Solvents on PCDTBT:PC70BM Based Solar Cells. Organic Electronics, 12(11), 1788–1793, 2011. [12] Tang, H., Motonaga, M. and Torimitsu, K., The First High Molecular Weight Poly(N-Alkyl-3, 6Carbazole)s, Macromolecules, 35, 1988–1990, 2002. [13] Ramkumar, S., Manoharan, S. and Anandan, S., Synthesis of D-(π-A)2 Organic Chromophores For DyeSensitized Solar Cells, Dyes and Pigments, 94(3), 503–511, 2012. [14] Ramkumar, S. and Anandan, S., Synthesis of Bianchored Metal Free Organic Dyes for Dye Sensitized Solar Cells, Dyes and Pigments, 97(3), 397–404, 2013. [15] Bahy, A., Chemli, M., Hassine and B. Ben., Synthesis and Characterization of New Carbazole-Based Materials for Optoelectronic Applications, Tetrahedron Letters, 54(31), 4026–4029, 2013. [16] Kim, Y., Cook, S., Tuladhar, S. M., Choulis, S. A., Nelson, J. and Ree, M., A Strong Regioregularity Effect In Self-Organizing Conjugated Polymer Films and High-Efficiency Polythiophene:Fullerene Solar Cells. Nature Materials, 5(3), 197–203, 2006. [17] Wu, J., Yue, G., Xiao, Y., Lin, J., Huang, M., Lan, Z. and Sato, T., An Ultraviolet Responsive Hybrid Solar Cell Based on Titania/Poly(3-Hexylthiophene), Scientific Reports, 3, 1283, 2013.

Synthesis of 1,7-Disubstituted N,N’Bis(hexyl)Perylene-3, 4:9, 10-Tetracarboxylic Acid Diimide (PDI) Small Molecule for Organic Solar Cell Application Ramasamy Ganesamoorthy, Govindasamy Sathiyan, E.K.T. Sivakumar1, Rangasamy Thangamuthu2 and Pachagoundar Sakthivel Organic Chemistry Division, School of Advanced Sciences, VIT University, Vellore, Tamil Nadu 1 Centre for Nanoscience and Technology, Anna University, Chennai 2 Electrochemistry Materials Science Division, CSIR - Central Electrochemical Research Institute Karaikudi E-mail: [email protected]; [email protected], [email protected]

ABSTRACT We report the synthesis of N,N’-Bis(hexyl)-1,7-di(2,2’-bithiophenyl)perylene-3,4:9,10-tetracarboxylic acid diimide (BT-PDI-H) based small molecule (donor) used for organic solar cell application. The synthesized small molecule was confirmed by FT-IR, NMR techniques. The BTPDI-H has broad and strong absorption in the UV-Vis to near IR region. From UV-visible spectra we observed a low optical band gap Egopt-1.75 eV for BT-PDI-H. The melting point is above 360°C. The desired property for the high power conversion efficiency (PCE) organic solar cells (OSC) the molecules must have low band gap, broad and strong absorption in the near IR region. The synthesised BT-PDI-H has fulfil the above criteria this may have the possibility to give high PCE. Keywords: Perylene, Suzuki Coupling, Low Band Gap, Organic Solar Cells.

INTRODUCTION The perylene diimide small molecular dye was introduced as an acceptor in bilayer organic solar cellin the year of 1986 by Tang [1]. The core of the OSC is the active layer. The active layer is sandwiched between the low work function cathode and high work function anode, it consist of an electron donating small molecule or a polymer as the donor and high electron affinity small molecule, polymer or Fullerene derivatives as an acceptor in a blend or a bilayer form [2]. In all kind of organic solar cells the photoinduced electron transfer is the reason behind the conversion of sun light into electricitywhich relied on the ionization energy of the donor and electron affinity of the acceptor. Perylene dyes are having the following special featureslow cost, high molar absorption coefficient, high thermal, environmental stability and easy to design the molecule for desirable properties [3]. Polymers and small molecules of perylene based dyes are used as a donor as well an acceptor in organic solar cell.The drawbacks of polymers are reproducibility, solubility and purity. But in the case of small molecules it is reverse and mass production in short span of time is possible [4–6]. PDI small molecules are most widely used as donors because of the high electron transporting property and high electron affinity [7–10]. Chen et al. first introduced the new D-A-D type perylene diimide dye which containing the oligothiophene in the bay position in 2005 [11]. The effect of V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 163–166 (2015)

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substituents was clearly explained by Perrin et al., The presence of electron withdrawing group in the bay position increases the electron accepting n-character and the presence of highly electron donating group will enhance the p-character [12]. Balaji et al., reported the interesting property of a pentathiophene substituted D-A-D type perylene diimide. The important finding was the conversion of n-type character into p-type character by the D-A-D type small molecule after the annealing process [13]. In 2011 Choi et al., synthesised a bay annulated D-A-D type small molecule which showed very good hole mobility and it used as donor and they achieved 1.42% of PCE. From the above results it is clear more steric and high electron donating moiety in the bay position to the perylene core will results a very good donor small molecule [14].

Scheme 1: Synthesis of BT-PDI-H Small Molecular Dyes

Synthesis of 1, 7-dibromo-perylene-3,4,9,10-tetracarboxylic dianhydride (BPDA): (39.4 g, 100 mmol) of perylene-3,4,9,10-tetracarboxylic dianhydride (PDA) was dissolved in 350 mL of Conc. H2SO4. The solution was stirred at room temperature under nitrogen atmosphere for 8 h. Catalytic amount of Iodine (504 mg, 2 mmol) was added. (10.3 mL, 200 mmol) of bromine was added drop wise to a period of 8 h. The solution was stirred at 85 ⁰C for 8 h. After cooled to room temperature, washed with water to neutralise the acid and the crude was filtered off. It is in dark red colour. It is a mixture of 1, 7- and 1, 6-dibromo isomers. M. F: C24H8Br2O6, Yield: 84%, m.p 360°C. N, N’-Bis(hexyl)-1, 7-dibromoperylene-3, 4, 9, 10-tetracarboxylic diimide (BPDI-H) The BPDA(20.9 g, 39 mmol) in NMP (300 mL) was placed in a sonicator for 0.5 h. To the above mixture n-hexylamine (13.75 mL, 104 mmol) and acetic acid (100 mL) were added drop wise. The mixture was stirred for 48 h at 85°C under N2 atm. Cooled to room temperature, poured into the ice water and neutralised with dil. HCl and filtered off. The crude product was purified by column chromatography using hexane and ethyl acetate 80:20 as eluent. A reddish brown solid was obtained in 35.70% yield.M. F: C36H32Br2N2O4,m.p.185 ⁰C, FT-IR (KBr, cm–1): 2914 (aliphatic ν C-H), 2903 (aliphatic νC-H), 2848 (aliphatic νC-H), 1695 (ν C = O), 1651 (aromatic νC = C), 1591, 1433 (νC-N), 1392, 1238, 1198, 1153, 808, 746, 663.1H-NMR [400 MHz, CDCl3, δ = 7.26, s]: 0.95 (t, 6H), 1.32–1.48 (m, 12H), 1.72–1.77 (m, 4H), 4.12–4.20 (t, 4H), 8.60 (d, 2H), 8.9(s, 2H), 9.40 (d, 2H). 13C-NMR [400 MHz, CDCl3, δ = 77.16, 3 peaks]: 162.7, 162.2 (C = O), 137.9, 132.8, 132.6, 129.8, 129.1, 128.4, 126.9, 123.2, 122.7, 120.7 (aromatic carbon), 40.7, 29.9, 29.2, 27.7, 22.4, 13.9 (hexyl amine carbon).

Synthesis of 1,7-Disubstituted N,N’-Bis(hexyl)Perylene-3, 4:9, 10-Tetracarboxylic Acid Diimide ...

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N,N’-Bis(hexyl)-1, 7-di(2, 2’-bithiophenyl)perylene-3, 4:9, 10-tetracarboxylic Acid Diimide (BT-PDI-H) PDI-H (0.358 g, 0.5 mmol) was taken in 3 neck R. B flask 10 m L of dry THF was added and purged with N2 for half an hour.Pd(PPh3)4 (0) catalyst 144 mg was added and nitrogen purging continued. The temperature was raised to 50°C and 3 mL 2 M solution of K2CO3 was added. To the above reaction mixture 2, 2’-bithophene-5-boronic acid pinacol ester (0.292 g, 1 mmol) was added and refluxed for overnight under N2 atm. After being cooled to room temperature, 3 mL of 2N HCl was added and the mixture was extracted with CH2Cl2 and dried over anhydrous Na2SO4, and concentrated. The residue was purified by column chromatography using hexane and ethyl acetate 95:5% as eluent to give the product (BT-PDI-H) as a violet color solid in 37% yield (200 mg).M. F: C54H42N2O4S4.m.p.> 360°C.

0.8

Normalized (au)

Normalized absorption (au)

BT-PDI-H (Solution) BT-PDI-H (THIN FILM)

0.8 0.6 0.4

0.6 0.4 0.2

0.2 0.0 300

BT-PDI-H (Absorption) BT-PDI-H Fluoroscence 353 nm

1.0

1.0

400

500

600

Wavelength (nm)

700

800

0.0 300

400

500

600

700

800

Wavelength (nm)

Fig. 1: a). UV-Visible Spectra of BT-PDI-Hin CHCl3 (circle) and thin Film (black square). b) PL (circle) and UV Visible (square) Spectra of BT-PDI-H in 4 × 10–7 M Chloroform Solution

RESULT AND DISCUISSION Absorption and Emission Properties Absorption and emission spectra was measured in chloroform (4.0x10–7M) as well as thin film for BTPDI-H. The UV-vis spectrum and PL spectrum of BT-PDI-H were given in Figure 1. The BT-PD-H was showed three absorption bands first band at 328 nm, 288 nm, second band at 473 nm,480 and third band at 571, 596 nm respectively for solution and thin film form. The most intense absorption band was appeared at 328 nm for BT-PDI-H. The third band appearance at 571 nm may be due to the So-S1 transition of more conjugated bithiophene moiety. Absorption spectra of BT-PDI-H in thin film state showed slight red shift in second band and 30 nm variation in the third band is due to the rigid packing of the BT-PDI-H resulted an increased p-p intermolecular interactions. The broadening and red-shift of the bands are visible and consequently lead to smaller gap. The optical band gap of the synthesized BT-PDI-H was 1.75 eV. The BT-PDI-H showed extremely weak fluorescence due to the effective intramolecular charge transfer at the given excitation wavelength between the oligothiophene-donor and perylene-acceptor. CONCLUSSION In summary, BT-PDI-H small molecular dye was synthesised. The absorption value for this small molecule extended upto 800 nm and it resulted reduced band gap value i.e., Eg (opt) 1.75 eV. The high

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electron donating bithiophene moiety not only increases the absorption in UV-vis spectra but also declined the fluorescence quantum yield than compared with parent perylenediimide dyes due to the extended conjugation of the bithiophene. The new D-A-D type small molecule is stable upto 400°C.

ACKNOWLEDGEMENTS This project has been supported by the Ministry of Department of Science and Technology (DST), India, under the Science and Engineering Research Board (SERB) NO. SB/FT/CS-185/2011. We thank the VIT management for the lab and instrument facility and VIT-SIF lab, SAS, Chemistry Division for NMR and GC-MS Analysis. REFERENCES [1] Tang, C.W.,Two layer Organic Photovoltaic Cell, Appl. Phys. Lett., 48, 183–185, 1986. [2] He, Z., Wu, H. and Cao, Y., Recent Advances in Polymer Solar Cells: Realization ofHigh Device Performance by Incorporating Water/AlcoholSoluble Conjugated Polymers as Electrode Buffer Layer, Adv.Mater., 26,1006–1024, 2014. [3] Vajiravelu, S., Ramunas, L., Vidas, G.J.,Valentas, G., Vygintas, J. and Valyaveettil, S., Effect of substituents on the electron transport properties of bay substituted perylene diimide derivatives, J. Mater. Chem., 19, 4268–4275, 2009. [4] Sakthivel, P., Gunasekar, K., Woo, H.Y., Kranthiraja, K., Kim, et al., Carbazole linked phenylquinolinebased fullerene derivatives as acceptors for bulk heterojunction polymer solar cells: Effect of interfacial contacts on device performance, J. Mater. Chem., A. 2, 6916–6921, 2014. [5] Lucas, B., Trigaud, T., Videlot-Ackermann, C., Polym. Int., Organic transistors and phototransistors based on small molecules, 61, 374–389, 2012. [6] Kozma, E., Kotowski, D., Catellani, M., Luzzati, S., Famulari, A., et al., Synthesis and characterization of new electron acceptor perylenediimide molecules for photovoltaic applications, Dyes and Pigments, 99, 329–338, 2013. [7] Mikroyannidis, J.A., Suresh, P. and Sharma, G.D., Efficient bulk heterojunction devices based on phenylenevinylene small molecule and perylene–pyrene bisimide, Synthetic Metals, 160, 932–93, 2010. [8] Sharma, G.D., Suresh, P., Mikroyannidis, J.A. and Stylianakis, M.M., Synthesis of a perylene bisimide with acetonaphthopyrazine dicarbonitrile terminal moieties for photovoltaic applications, J. Mater. Chem., 20, 561–567, 2010. [9] Li, J., Dierschke, F., Wu, J., Grimsdale A.C. and Mullen, K., Poly (2,7-carbazole) and perylene tetracarboxydiimide: A promising donor/acceptor pair for polymer solar cells, J. Mater. Chem., 16, 96– 100, 2006. [10] Liu, Y., Wang, Y., Ai, L., Liu, Z., Ouyang, X. and Ge, Z., Effects of functional groups at perylene diimide derivatives on organicphotovoltaic device application Dyes and Pigments, 121, 363–371, 2015. [11] Chen, S., Liu, Y., Qiu, W., Sun, X., Ma, Y. and Zhu, D., Oligothiophene-Functionalized Perylene Bisimide System: Synthesis, Characterization, and Electrochemical Polymerization Properties, Chem. Mater., 17, 2208–2215, 2005. [12] Perrin, L. and Hudhomme, P., Synthesis, Electrochemical and Optical Absorption Properties of New Perylene-3,4:9,10–bis(dicarboximide) and Perylene-3, 4:9, 10-bis(benzimidazole) Derivatives, Eur. J. Org. Chem., 5427–5440, 2011. [13] Segura, J.L., Herrera, H. and Bauerle, P., Oligothiophene-functionalized naphthalimides and perylene imides: design, synthesis and applications, J. Mater. Chem., 22, 8717–8733, 2012. [14] Choi, H., Paek, S., Song, J., Kim, C., Cho, N., Ko, Synthesis of annulated thiophene perylene bisimide analogues: their applications to bulk heterojunction organic solar cells, J., Chem. Commun., 47, 5509–551, 2011.

Investigation on Structural Properties of Gadolinium Doped Barium Cerate Electrolyte A. Senthil Kumar, R. Balaji, P. Agalya, S. Bhuvanasundari and R. Venkateswaran1 Department of Physics, PSG College of Technology Coimbatore Department of Chemistry, PSG College of Arts and Science Coimbatore

1

ABSTRACT Solid oxide fuel cells (SOFCs) have attracted a great deal of consideration among the promising fuel cell systems for energy conversion. In SOFC, electrolyte plays a vital role to increase the energy conversion efficiency. The main hurdle is its higher operating temperature (1000°C) which results in design limitation and higher fabrication cost. In this work, Gadolinium Doped barium cerate (BCG) Electrolyte was successfully synthesized to operate at intermediate temperature (600–800°C) by co-precipitation technique. The structure of BCG was identified as orthorhombic perovskite phase and the crystallite size was found to be around 30 nm. From TEM, the particle size was found to be 32 nm and is in good agreement with XRD results. Further, the particles sizes were found to be uniform in size and shape. From the above results it is understood that the obtained particle is a single crystallite which indicates the absence of agglomeration. The formations of BCG nanoparticles were resulted in reduced sintering temperature of the electrolyte. By lowering the sintering temperature, the barium loss was successfully reduced in order to get the required orthorhombic perovskite phase and can be operated at intermediate temperature. Keywords: BCG, Nanoparticles, Electrolyte, Fuel Cell.

INTRODUCTION Solid oxide fuel cells play an important role as a power sources yet invented for the conversion of chemical energy directly into electrical energy free from pollution and are environmental friendly in nature. In SOFCs, chemically stable electrolyte is the major part to convert the oxygen ion by the reduction of oxidant at cathode and oxidation of fuel in the anode side. So far yttrium stabilized zirconia has been considered as a state of art as oxide ion electrolytes which operates at higher temperature (800°C to 1000°C) for energy conversion with higher ionic conductivity and efficiency too [1]. This higher temperature operation may leads to several problems such as high materials cost, low performance of the fuel cell and thermal mismatch between the interconnects during fabrication. In order to overcome these problems, the operating temperature of the fuel cell must be reduced to intermediate temperature (600–800°C) by choosing the high ionic conducting electrolyte [2, 3]. The other oxygen ion electrolyte are doped bismuth oxide, lanthanum gallete, doped ceria. Among this gadolinium doped barium cerate with Perovskite structure of ABO3 group have been considered as a one of the good candidate for solid oxide fuel cell application with fast migration of oxide ions at lower operating temperature [4–7]. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 167–172 (2015)

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In the present research work gadolinium doped barium cerate electrolyte is to be prepared by wet chemical method. The electrolyte prepared was sintered using a modern microwave technique to have higher ionic conductivity with less electronic conduction at intermediate operating temperature (500°C–700°C) [7,8]. The powder samples were characterized using TG/DTA for identifying the calcination temperature of the as prepared powder sample, followed by calcination the powder samples were given for XRD analysis to identify the phase purity and pressed into pellet with 150Mpa for sintering at 1400°C. Structural analysis have been carried out with the help of SEM and HRTEM and were presented

EXPERIMENTAL WORK The Gadolinium doped barium cerate (BCG) powder has been synthesized via chemical route (Coprecipitation technique). Barium nitrate (99.5% pure) purchased from Sigma–Aldrich, Italy and Cerium nitrate hexa hydrate (99.5%), Sigma–Aldrich, Italy were taken separately and get dissolved in 30 ml of distilled water. On the other hand, Gadolinium oxide (99.9%, Sigma–Aldrich, Italy) was dissolved in Conc. Nitric acid by heating in a separate beaker and stirred well until the powder gets completely dissolved to form gadolinium nitrate. The individual nitrate solutions were then slowly mixed together and added with Ammonium Hydroxide to form the precipitate with pH>10 and stirred well with rpm of 1000 in a magnetic stirrer for 30 minutes. PEG (Poly Ethylene Glycol) of 10% of the solution was added to the mixer as excipient (fillers) to reduce the Agglomeration and kept in a water bath for drying after stirring for 30 minutes. The obtained precipitant solution was filtered with watt man filter paper and again kept for drying in hot air oven at 80°C for about 8–9 hours [7,8, 9].The flakes obtained from the mixture were Calcinated at 900°C for 4 hours for obtaining the dry powder. DSC studies was carried out with the help of TA Instruments to identify the calcination temperature and XRD studies for phase determination, their crystallinity and the purity of the as-prepared green powder. Green pellets were obtained by uniaxial pressing at 14.7 MPa, using a steel die of 12 mm diameter. Polyvinyl alcohol (PVA) was added as a binder to increase the green strength of the pellets [7,8]. The prepared pellets were taken in alumina boat for sintering in microwave furnace at 1400°C for 20 minutes in air. The sintered pellets were then characterized with XRD, SEM, HRTEM and EDS. RESULTS AND DICUSSIONS DSC/TGA curve (Figure 1) shows that the BCG phase formation get completed at 900°C, where it completely crystallized into perovskite structure. From DSC curve it is to understood the up to 400°C there is a linear decrease in weight loss can be attributed as desorption of physisorbed (surface) water and organic solvent loss in the first region at 102°C The sign of two sharp weight loss peak are observed at 550°C and 760°C. The first down peak may be due the combustion of residual organic species with 5.87% weight loss and the second from plateau is due to the decomposition of barium carbonate with 1.68% weight loss after which there is no sign of any loss from 900°C which indicates that the BCG phase completion of barium cerate electrolyte [9]. Based on this TGA analysis the calcination temperature was identifies for the powder sample and get calcined at 900°C for 4 hours to get dry powder for further studies.

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Fig. 1: DSC-TGA Curve for BCG10 Calcined at 900°C

XRD pattern for the as prepared BCG10 powder sample (a) calcined at 900°C and (b) pellet sintered at 1400°C have been shown in Figure 2. All the major diffraction peaks were indexed accordingly for the calcined powder with orthorhombic perovskite structure and found to match with the JCPDS file No: 082–2373 In the XRD pattern of the calcined powder, some of the peaks values are not shown because of insufficient energy to form its phase and may be due to lower calcination temperature [6]. But in contrast XRD for the pellet shows all the major reflection peaks of orthorhombic perovskite structure. The phase was identified as orthorhombic crystal structure for both powder and pellet samples. From XRD of the calcined powder it is clearly seen that the peaks are very sharp and highly intense. This confirms the complete phase formation occurs at 900°C which is much lesser than the earlier reported values and the sintering temperature have also been reduced from the earlier reported work [8] and is in well agreement with all results [9]. The crystallite size of the BCG10 powder sample was calculated from Debye Scherer method using the equation (1) and it is found to be around 30 nm [10,11]

D=

0.9λ β Cos θ

… (1)

where D is crystallite size in nm, λ is the radiation wavelength (for Cu Kα radiation, λ = 1.5418 Å), θ is the diffraction peak angle and β is the peak broadening measured at half its maximum intensity (in radians). The crystallite size value was found to be nearly equal to the value reported earlier [12, 13]

Fig. 2: XRD Pattern for BCG10 Powder (a) Calcined at 900°C and (b) Pellet Sintered at 1400°C

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Application of Nanostructured Materials for Energy E and Envirronmental Technnology

H HRTEM imagee of the pow wder sample calcined c at 9000°C have beeen shown in Figure 3 it is observved that the particle p size off BCG powdeer is very small in nature Fiigure 3a and are a found to be b aroundd 30nm. The crystalline c nanno particles arre get observedd for the as prrepared powdeer samples. Thhe crystaalline size of XRD X is in founnd to be muchh closer and in good agreem ment with this HRTEM H resullts (Figurre 3b). The en ntire image hass shown the sppherical structtured nano parrticles with hiigh crystallinitty [11]

(a)

(b)

(c)

F 3: High Resolution Fig. R TEM M Images (a) Parrticle Size (b) Nano N Scale and (c) SAED Patteern of BCG SA AED pattern depicts the pervoskite phaase with all itss major reflecction peaks (F Figure 3c). Thhe crystaalline plane are indexed in SAED S patternn and found too exactly matcched with XRD D pattern in all a majorr reflection peeaks [14]. Thee Stoichiomettric phase preesence of Ba, Ce, Gd weree identified annd confirrmed through EDX analysiss (Figure 4). The T solid soluttion prepared through this co c precipitatioon methood which leadss to the compllete precipitation of Gd 3+ ioons in BaCeO O3 phase. The presence of Cu C in ED DX may be duee to grid in TE EM analyzer.

Fig. F 4: Energy Dispersion D Specctra of BCG10 Powder P Calcineed at 900°C

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Fig. 5: SEM Image for BCG Pellet Sintered at 1400°C

The surface micrograph of Ba10Ce1.xGdxO3 was studied by SEM analysis. From this SEM results (Figure 4) the average grain size was found to be around 1 μm. The sintered sample shows a well developed nano grains with less porosity and uniform grain size with closely packed at boundary which result in lower grain boundary resistance for the dense electrolyte to have high ionic conductivity. As reported from venka et al. [8] the area of dark region increases with BCG phase mole fraction and are compared with XRD results. A very few enclosed pores were also absorbed on its surface.

CONCLUSION Gadolinium Doped barium cerate (BCG) Electrolyte have been successfully synthesized by coprecipitation technique to operate at intermediate temperature (600–800°C). The structure of BCG was identified and confirmed as orthorhombic pervoskite phase and its crystallite size was calculated to be around 30 nm. HRTEM image have shown that, the particle size to be around 32 nm and is in good agreement with XRD results. Further, the particles sizes were found to be uniform in size and shape. The formation of single crystallite BCG nanoparticles indicates the absence of agglomeration at low sintering temperature. The required orthorhombic pervoskite phase was formed at lower sintering temperature with reduced barium loss and thus this BCG electrolyte can act as a good candidate for solid oxide fuel cell application. ACKNOWLEDGEMENT The authors would like to thank the Management, Principal and TEQIP II, PSG College of Technology for their kind support extended towards this research work and UGC, New Delhi for providing financial support. REFERENCES [1] Singhal, S.C., Solid State Ionics 135, 305, 2000. [2] Brett, D.J.L., Atkinson, A., Brandon, N.P. and Skinner, S.J., Chem. Soc. Rev., 37, 1568, 2008. [3] Garcia-Barriocanal, J., Rivera-Calzada, A., and Santamaria, J., Science, 321, 676, 2008. [4] Kato, H., Kudo, T., Naito, H. and Yugami, H., Soild State Ionics, 159, 296, 2003.

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Takahashi, T. and Iwahra, H., Energy Convers, 11 105, 1971. Gorbova, E. et al.., Journal of Power Sources, 181, 292–296, 2008. Kumar, A.Senthil and Balaji, R., Int. J. opt elec. and advanced mat.rapid com, 4–5, 788–791, 2015. Venkatasubramanian, A. and Gopalan, P., Int Jou of Hyd en, 35, 4597–4605, 2010. Mahata, T., Das, G. and Mishra, R.K., Journal of Alloys and Compounds, Vol. 391, 129, 2005. Yang, Huaming and Huang, Chenghuan, Mat Res Bull, 40, 1690–1695, 2005. Liu, Ai Zhu; Wang, Jian Xin and Rong, Chang, Cer Int, 39, 6229–6235, 2013. Prasada, D. Hari, Kim, H.-R. and Park, J.-S., J. of Alloys and Compounds, 495, 238–241, 2010. Gondolini, A., Mercadelli, E. and Sanson, A., Ceramics International, 37, 1423–1426, 2011. Anjaneya, K.C. and Nayaka, G.P., J. Journal of Alloys and Compounds, Vol. 585 (2014), 594–601.

Facile Synthesis of (CdZn)Se Nanocrystalline thin Films via Arrested Precipitation Technique (APT) for Photovoltaic Application Chaitali S. Bagade, Vishvnath B. Ghanwat, Kishorkumar V. Khot, Pallavi B. Patil, Rahul M. Mane and P.N. Bhosale Materials Research Laboratory, Department of Chemistry, Shivaji University, Kolhapur E-mail: [email protected]

ABSTRACT Nanocrystalline (CdZn)Se thin film have been successfully synthesized through a simple and cost effective arrested precipitation technique. Deposition and synthesis strategy of (CdZn)Se thin films exert appreciable influence on the photovoltaic properties of solar cells. In this paper a systematic characterization of optostructural, morphological, compositional and electrochemical property has been carried out. The optical band gap was evaluated from UV-Vis-NIR spectra in the wavelength range 400–1100 nm. X-ray diffraction (XRD) pattern reveals that the deposited film was nanocrystalline in nature and exhibit cubic crystal structure. The dependency of microstructural parameters such as crystallite size has been studied. Scanning electron microscopy (SEM) images demonstrates that surface morphology was uniform, dense, smooth and well adhered to substrate surface. As deposited nanorystalline (CdZn) Sethin film exhibits 0.61% conversion efficiency at room temperature.

INTRODUCTION In recent years, the field of nanocrystalline semiconducting thin films is rapidly expanding. The increasing interest for these materials is due to the fact that these are characterized by properties which are substantially different from the corresponding ones for bulk semiconductors [1]. In this regards IIVI group semiconductors are considered important technological materials due to its potential applications in optoelectronic devices [2]. Among them, cadmium zinc selenide (CdZn)Seis found to be an excellent material with a band gap value around 1.9 eV which make them fairly interesting for the fabrication of solar cells through photoelectrochemical route [3].(CdZn)Seis a promising ternary material because of its tunable parameters such as band gap and surface morphology. The most important applications of (CdZn)Sethin film is in solar cells, high efficiency thin film transistors, light emitting diodes, laser diodes and electroluminescent devices [4–7].Various techniques have been used for the synthesis of (CdZn)Se thin films such as electrodeposition, chemical bath deposition (CBD), screen printing followed by sintering and metal organic chemicalvapour deposition (MOCVD) [8–10]. One of the disadvantages of this technique is that some of them need sophisticated instrumentation along with vacuum and high temperature which increases production cost of the material. However, solution based deposition method, i.e. arrested precipitation technique offers the possibility of depositing thin films at low temperature under atmospheric conditions and at low fabrication cost. As a one step, environment friendly and low energy consumption aqueous technique, APT is based on V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 173–176 (2015)

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controolled release of o metal ions from metal coomplexes and reaction withh chalcogen ioons accordinglly Ostwaald ripening laaw [11].

EXPE ERIMENTA AL Deposition of Thin Films In typpical synthesis, 8 ml of 0.05 M [Cd-EDTA A] and 12 ml of o 0.2 M [Zn-E EDTA] solutioon was taken in i reactioon beaker. The pH of bath was w adjusted to t 10.4 by dropp wise additioon of ammoniaa. 20 ml of 0.225 M Naa2SeSO3 solution was addedd to reaction baath with consttant stirring. Total T volume of o reaction batth was made m to 50 ml by adding double distilled water then reaaction mixturee was stirred for f 5 min to get homoggeneous soluttion. Precleaned ITO glass substrates weere immersed vertically cloose to the inneer wall of o reaction con ntainer and thhen kept at 50°C temperaturre with constaant substrate rotation r 45 rpm m and deeposition timee was kept 4 h. h various prepparative param meters like pH H, temperaturee, concentratioon and tim me were finallized at initial stage of depoosition After deposition d substrates were withdrawn w from m bath, sufficiently s rin nsed with douuble distilled water w and driedd at room tem mperature. Deposited thin film m wasunniform, peach colour and well w adherent to t glass substrrate. This depoosited thin film m was used foor furtheer investigation ns. RESU ULTS AND DISCUSSIO D N Opticcal and Stru uctural Ana alysis Optical band gap energy e of (Cd dZn)Se thin fillm was calcullated by using g optical abso orption spectra. n spectra of deposited d (CdZn)Sethin film f was reco orded in wav velength rang ge Opticcal absorption 400–1 1100 nm, as shown in Fiigure 1a. Eleectronic transsition betweeen valence an nd conductio on bandss starts at thee absorption edge corresp ponding to th he minimum energy differrence betweeen the lo owest energy of conductio on band and highest enerrgy of valencce band in material. Figurre 1a cleearly shows that maximum m optical absorption is observed at aro ound 650–750 0 nm.

Fig. F 1: (a) Optiical Absorption n Spectra and Inset Figure Shows Plots of (αhν)2 vs. v (hν) (b) XR RD Pattern of (CdZn)Se ( Thin n Film

T band gap The p of (CdZn)S Sethin film was w determineed by extrapolating straig ght line to th he energ gy axis. Natu ure of plots suggest a direct and allowed a typee of transitio on, since lin ne depen ndence is obtaained at n = ½. ½ The opticaal band gap value v of (CdZ Zn)Sethin film m 1.91 eV waas obserrved as shown n ininset Figu ure 1a.

Facile Synthesis S of (CddZn)Se Nanocrysstalline thin Film ms via Arrested Precipitation P Tecchnique ...

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X XRD pattern of o (CdZn)See thin film was w carried ou ut at room teemperature in n the range of o 10–80 0° and sho own Figure 1b. Broad and intensse peaks in n XRD pattterns confirm m nanoccrystalline naature of thin film. XRD patterns p of thiin film exhib bit peaks at 25.39°, 2 42.17°, 49.74 4° and 60.85°° which are indexed i to th he (111), (220 0), (311) and d (400) planees respectivelly of cub bic CdSe (JC CPDS card no. n 19–0191). Also the peeaks at 12.47 7°, 14.30°, 20.13°, 23.62°, 29.32 2°and 31.83° are indexed to the (111), (200),(220), (311), (400)) and (331) planes p of cubiic ZnSe (JCPDS carrd no. 02–04 479). The XR RD pattern of o (CdZn)Se nanocrystals was locateed betweeen those for CdSe and Zn nSe materialss. Such phasee formation of o CdSe and ZnSe Z providees strong g evidence of (CdZn)Se solid s solution n formation which w was in n good agreeement with th he reportted value [12 2–13]. The average a crysttallite sizewaas calculated from XRD patterns p usin ng Deby ye Scherer’s eq. e [4]. The calculated cry ystallite size was w 24 nm off (CdZn)Se th hin film.

Morp phology and Composition nal Analysis In ord der to study the microstru uctures of (C CdZn)Se thin films, f scanniing electron microscopy y (SEM) was used. Fig gure 2(a-d) Low and d high nification SEM M images and (e) EDS sp pectra of magn (CdZn n)Se thin film m. Figure 2 show ws high and d low magniification Sethin films. Itshows SEM micro imagees of (CdZn)S nsely packed nanospherres like formaation of den smooth homogen nous surface morphology y which d uniiformly on substrate s surfface.The was dispersed presennce of elemeents in depoosited thin film fi was confirrmed by ED DS technique.. Figure 2(e)) shows elemeental distributiion of the connstituent elem ments for typicaal (CdZn)Se th hin film. The elemental e anallysis was carriedd out only for fo Cd, Zn, and a Se elements. The peaks at 3.55, 1.10 and 1.70 keV confirms the presence n thin film, reespectively. Innset table of Cdd, Zn and Se in showss expected an nd observed atomic a percenntages of Cd, Zn Z and Se in n (CdZn)Se thin film confirming compoosition of thin n film which is in good aggreement with expected e atom mic percentage [14]. Photo oelectrochemical Perfo ormance The PEC P perform mance of (Cd dZn)Se thin filmwas check ked with the help of a staandard two electrode config guration. In n the dark k and und der an illumiination of 30 0 mW/cm2 liight intensity y and in 0.5 M sulfide/pollysulfide red dox electroly yte.After illumiination, shift fting of J–V curve in thee fourth quadrrant suggestss that electrons were geenerated due to the umination, light illu magnic voltaage increasees with tude of open circuit

Fig. 2

Fig. 3: J-V Ch haracteristics of o (CdZn)Se Th hin Film in Sulph hide /Polysulphide Electroly yte

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negative polarity towards (CdZn)Se electrode, indicating cathodic behaviour of photovoltage which confirms that (CdZn)Se thin films are n-type.The current voltage (J–V) characteristics of glass/ITO/(CdZn)Se 0.5 M polysuhide/graphite were measured.From the J–V measurements, the obtained value of Jsc was 1.162 mA/cm2 and corresponding values of Voc was 581 mV, respectively. Closely packed nanospheres improve the carrier transport mechanism and minimize the surface trap states. Such types of interconnected nanospheresprovide higher effective surface area for light absorption.Theconversion efficiency 0.61% was achieved for (CdZn)Se thin film. [15].

CONCLUSION In conclusion, we report a facile chemical route for the deposition of (CdZn)Se thin film by using a simple and cost effective APT. From optical measurements, we can conclude that optical band gap was direct allowed type having band gap energy 1.91 eV. X-ray diffraction pattern illustrate cubic crystal structure for both CdSe and ZnSe phases. SEM study illustrated that formation of nanospherelike morphology for (CdZn)Se thin film. Such morphology shows high efficiency due to large surface area for the absorption of light. EDS analysis shows presence of all elements (Cd, Zn and Se) in stoichiometric form. The highest conversion efficiency was obtained for (CdZn)Se thin film (0.61%) thin film. Overall achieved results reveals that newly devised APT is a suitable method for the synthesis of different metal chalcogenide thin films.

ACKNOWLEDGEMENT One of the authors, Chaitali S. Bagade is very much thankful to Department of Science and Technology (DST), New Delhi for providing DST-INSPIRE fellowship for financial support (Registration No. IF140571). This work is also supported by the Priority Research Centre Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2009–0094055).

REFERENCES [1] Ubale, U., Mater. Chem. and Phys., 2010, 121, 555. [2] Litvinov, D., Schowalter, M., Rosenauer, A., Daniel, B., Fallert, J., Löffler, W., Kalt, H. and Hetterich, M., Phys. Stat. Sol A., 2008, 205, 2892. [3] Zhai, R., Wang, S., Xu, H.Y., Wang, H. and Yan, H., Mater. Lett., 2005, 59, 1497. [4] Wu, X., Yu, Y., Liu, Y., Xu, Y., Liu, C. and Zhang, B., Angew. Chem. Int. Ed., 2012, 51, 3211. [5] Schwenzer, B., Neilson, J.R., Jeffriesc, S.M. and Morse, D.E., Dalton Trans., 2011, 40, 1295. [6] Akaltun, Y., Yıldırım, M. Ali, Atesn, A. and Yıldırım, M., Mate. Res. Bull., 2012, 47, 3390. [7] Camargo-Gambo, G.J., Pacheco, J.S.L., Leon, J.M. de, Conradson, S.D. and Hernańdez-Caldero, I., Thin Solid Films, 2005, 490, 165. [8] Chavhan, S.D., Mane, R.S., Ganesh, T., Lee, W., Han, S.H., Senthilarasu, S. and Lee, S.H., J. Alloys Compd., 2009, 474,210. [9] Sutrave, D.S., Shahane, G.S., Patil, V.B. and Deshmukh, L.P., Mater. Chem. Phys., 2000, 65, 298. [10] Shan, C.X., Fan, X.W., Zhang, J.Y., Zhang, Z.Z., Wang, X.H., Lu, Y.M., Liu, Y.C., Shen, D.Z. and Lu, S.Z., J. Cryst. Growth, 2004, 265, 541. [11] Mezrag, F., Mohamed, W.K. and Bouariss, N., Phys. B, 2010, 405, 2272. [12] Cao, J., Xue, B., Li, H., Deng, D. and Gu, Y., J. Colloid Interface Sci., 2010, 348, 369. [13] Sheng, Y., Weia, J., Liu, B. and Peng, L., Mate. Res. Bull., 2014, 57, 67. [14] Zhong, X., Zhang, Z., Liu, S., Han, M. and Knoll, W., J. Phys. Chem. B., 2004, 108, 15552. [15] Kharade, S.D., Pawar, N.B., Mali, S.S., Hong, C.K., Patil, P.S., Gang, M.G., Kim, J. and Bhosale, P.N., J. Mater Sci., 2013, 48.

Synthesis of LEEH Capped CdTe Quantum Dots for Solar Cell Application Shilpa Patel, Bijendra Thakur and Sukanta K. Tripathy National Institute of Science and Technology, Berhampur, Odisha E-mail: [email protected]

ABSTRACT We here in this investigation synthesized CdTe quantum dots using LEEH (L-cysteine Ethyl ester hydrochloride) as a capping agent. EMA (Effective mass approximation) is used to estimate its size as 8.379 nm. The energy band gap is found to be 1.7005 e V which is redshirted by a small amount compared to its exitonic peak at 2.8335 eV. The synthesized quantum dots are spin coated on an ITO substrate at different rotation speed for 40 sec. CdTe coated ITO is then used as one electrode, while platinum is used as the other electrode in an electrolyte prepared using Sodium Sulphide (Na2S), Sulphur(S) and Sodium Hydroxide (NaOH).When the coated surface is illuminated with light of 4mW power, an open circuit voltage of 41.7 mV is measured. It is found that the open circuit voltage decreases with the decrease of size the CdTe Q.D’s and increases with the thickness of coating. These results seem to be important for third generation solar cells. Keywords: Quantum dots, Effective Mass Approximation, Excitonic Peak.

INTRODUCTION Considerable interest have been devoted in the recent years towards the synthesis of quantum dots for the solar cell applications as it is more stable, reduces the bulk material [1] solar cell like Si, Copper Indium, Gallium Selenide etc. [2–3] and doesn’t require high temperatures or a vacuum atmosphere to achieve stability when they are exposed to air [4]. Liquid Junction solar cell is a photochemical cell based on both organic and inorganic technology. It consists of two electrodes one photo anode and other metallic cathode immersed in semiconductor electrolyte where the charge separation occurs between these two electrodes. These photo anode and the metallic cathode electrodes have efficiency of about 10% and can generate electricity in ambient light (cloudy, sky, indoor etc.). Recently there are different types of quantum dots used in solar cells like core type, core/shell type or alloyed quantum dots which are applied as a thin film in the liquid junction solar cell thus giving high conversion efficiency from solar energy to electrical energy [5–6].When the quantum dots are used as the thin film in the liquid junction solar cell they become more sensitive to photon absorption even if the energy is less than the energy gap of nano crystalline semiconductor material. The different type of quantum dots reported for the application of solar cell are CdTe, CdSe, CdTe/CdS, PbS, Ge quantum dots. CdTe quantum dot is preferred in solar cells as they have high absorption coefficient (i.e. 1µm thick layer can absorb 90% solar spectrum), cheap and have a good conversion efficiency. Moreover L-cystein ethyl ester hydrochloride (LEEH) is used as a capping agent which is a derivative of protein amino acid and is used to passivate the core from further reaction to make it stable. We in this V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 177–180 (2015)

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investigation synthesized small size LEEH capped CdTe quantum dots using a simple chemical approach. The sample synthesized is then characterized by UV – Visible spectro-graphy. However the main intension in this paper is to study the effect of CdTe quantum dots layer on the efficiency of a liquid Junction solar cell. The paper is organized as follows in section 2; Experimental method to synthesize CdTe quantum dots is mentioned. While results and discussion are presented in section 3.Finally conclusion is made in section4.

EXPERIMENTAL Capped CdTe core shell quantum dots are prepared by a bottom up low cost chemicals technique at 80° C using reducing agent NaBH4 (99.99P purity, sigma), CdSO4(99.99 purity, sigma) and capping agent LEEH (99.99P purity, sigma) dissolved in Millipore water having resistivity 18.2 MΩ. First an aqueous solution was prepared by adding reducing agent NaBH4 (0.3M) in water (40ml) to which Tellurium(Te) powder (0.4 mM) was added and stirred for1 hour at 60°C to achieve NaHTe according to the following chemical reaction,

The color of the solution is light pink which becomes transparent after around half- an - hour stirring. The reducing agent NaBH4 was added to water prior to Te as the reverse would lead to oxidation of Te to TeO2 which is stable and synthesis become difficult. The second solution was prepared by taking CdSO4 (0.9 mM, 10ml) and capping agent LEEH(0.1 M, 10 ml) and stirred for half an hour at 45°C care has been taken such that first solution (2NaHTe + Na2B4O7) and second solution (CdSO4 + LEEH) stirring are completed at the same time so that both the solution can be added instantly . Both the solutions are mixed in the 1:1 ratio and stirred for 1 hour at 80°C. The chemical reaction undergoing the information of CdTe nano particle is as follows.

CdTe quantum dots thus prepared are spin coated on a clean I.T.O substrate, using a spin coater. Spin coated I.T.O is used as one electrode and Platinum is used as the other electrode, which is immersed in an electrolyte. The electrolyte is prepared by mixing Sodium Sulphide, Sulphur and Sodium Hydroxide (1 M each), with 10 ml of Millipore water. The solution is heated at 80°C for an hour until a transparent deep brown color is observed. The Schematic diagram to measure the open circuit voltage is shown in Figure 1.

Fig. 1: Schematic Diagram of Liquid Junction Solar Cell

Synthesis of LEEH Capped CdTe Quantum Dots for Solar Cell Application

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RESULTS AND DISCUSSION Prepared sample is analyzed using U-V Visible spectrography. Optical absorption spectra of the sample with time are shown in Figure 2.

Fig. 2: Optical Absorption Spectra of CdTe Solution with Time

Fig. 3: Energy Gap of CdTe Quantum Dots

Figure 2 shows that the prepared sample is stable at least for 20 days. The size of CdTe quantum dot is calculated using E.M.A. [7]

Where r is radius of QD, me*, mh* are effective mass for the electron and holes of the CdTe semiconductor, re is Bohr exciton radius and is found to be 8.379nm. Using Taugue model [8], a graph is plotted between (αhv)2 and hv, where α is the absorption coefficient and (hv) is the energy in e.v. The band gap is found to be 1.7005 ev. The prepared CdTe, LEEH capped sample is then spin coated on a I.T.O, substrate at different rotation speed 100 rpm, 200 rpm, 300 rpm for 40 sec. The corresponding thickness for these rotation speed is calculated from the calibration graph shown in Figure 4. thickness Linear Fit of Sheet1 B

0.0025 Equation

y = a + b*x

Weight

No Weighting

Residual Sum of Squares

0.0020

3.97735E-7 -0.92214

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0.70069

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thickness(nm)

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9.63352E-4

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150

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Fig. 4: Thickness v/s Spinning Rate Graph Voltage with Thickness of the Coating

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open circuit voltage 45 40

open circuit voltage(mV)

35 30 25 20 15 10 5 0 0.0000

0.0005

0.0010

0.0015

0.0020

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thickness of coating(n.m)

Fig. 5: Variation of Open Circuit

To test the efficiency of quantum dot, in solar cell application, open circuit voltage is measured using an experimental setup shown in Figure 2. In this experiment 4 mW/cm2 is exposed to the CdTe coated electrode (2 × 2.5 cm2). The variation of open circuit voltage with coating thickness is shown in Figure 5. To investigate the effect of the size of the CdTe quantum dot on efficiency, size is varied from 8.37 nm to 3nm by changing the LEEH concentration from 0.1M to 0.1mM. With a coating of this 0.1 mM LEEH with a spinning rate (100 rpm) the open circuit voltage is measured as 15.6 mV compared to 41.7 V when the size is 8.379 nm. This suggests that increase in the size of quantum dots increases the open circuit voltage and hence the efficiency of the liquid junction solar cell.

CONCLUSION We here in this investigation synthesized CdTe quantum dots using LEEH as a capping agent. It is found that at constant thickness, the open circuit voltage decreases with decrease of size of QDs. and increases with the thickness of the coating for a given size. These results will find applications for Liquid Junction solar cells. ACKNOWLEDGEMNT Authors wish to thank Prof. S.N. Sahu for his suggestions during the synthesis. Financial assistance by OREDA (DST, Govt. of Odisha) is also acknowledged. REFERENCES [1] [2] [3] [4] [5] [6] [8] [9]

Cachet, H., Cortes, R., Froment, M.M. and Etcheberry, A., Thin Solid Films 84, 361 (2000). Kelin, D.L., Roth, R., Lim, A.K.L., Alivisatos, A.P. and McEuen, P.L., Nature, 389, 669 (1997). Firth, A.V., Cole-Hamilton, D.J. and Allens, J.W., Appl. Phy. Lett., 75, 3120. Sarangi, S.N. and Sahu, S.N. “Structure and Morphological Studies of CdSe nanocrystals”, 109–117, (2006). Bailey, R.E., Nie, S. Edited by Rao, C.N.R., Mueller, A. and Cheetham, A.K. Chemistry of Nanomaterials, 2, 405 (2004). Smith, A.M. and Nie, S., Nature Biotechnology, 27(8), 732, (2009). Nemade, K.R., Waghuley, S.A., “UV-VIS spectroscopic study of one pot synthesized strontium oxide quantum dots”, 52–54 (2013). Patidar, D. Rathore, Sexena, K.S., Sharma, N.S. and Sharma, K.B., T.P. Energy Band Gap studies of CdS nanomaterials, J. Nano. Res., 2008, 3, 97–102.

Hydrothermally Prepared Porous Titanium Dioxide Nanorods/Nanoparticles and Their Influence in Dye Sensitized Solar Cells R. Govindaraj, M. Magesh, N. Santhosh, M. Senthil Pandian and P. Ramasamy SSN Research Centre, SSN College of Engineering, Kalavakkam, Tamil Nadu E-mail: [email protected]

ABSTRACT The TiO2 nanostructures composed of nanorods and nanoparticles were successfully synthesized via hydrothermal process and then used for dye sensitized solar cells. The powder X-ray diffraction pattern shows anatase phase with good crystalline behavior of the prepared materials. The specific surface area and average pore width of the synthesized material are 93.08 m2/g and 9.1 nm respectively. The morphological result shows the obtained materials are having rods and particles with different sizes. Based on the phase, porous and morphological behavior of the nanorods/nanoparticles, the fabricated dye sensitized solar cell gives 3.08% conversion efficiency with 74.27% fill factor. Keywords: Nanostructures, Powder X-ray diffraction, Electron Microscopy.

INTRODUCTION Among the photovoltaic devices, the dye sensitized solar cell has very attractive way to make the device due to its less expensive and easy manufacturing process. But, it has some stability and charge carrier recombination problems with the device. Generally, the photoanode of DSCs based on nanoparticles can provide larger surface area. However, the relatively poor electron transport property of TiO2 nanoparticles makes it difficult for further improving the photovoltaic properties of DSCs due to the surface states and large number of grains. Among the solution based experimental techniques, hydrothermal method has many advantages such as low cost, easier control of shape and size with different morphology [1-]. We prepared mixture of nanorods and nanoparticles (NR/NP) in a single step with hydrothermal process. EXPERIMENTAL To prepare mixture of NR/NP, 20 ml of Titanium (IV) butoxide (Aldrich) was added with 1.6 ml of ammonia solution (30% NH4 OH, Aldrich), stirred well for 5 min and transferred to the teflon-lined autoclave system and kept in a hot air oven for 24 hr at 130ºC. After that, the autoclave was naturally cooled to room temperature. The obtained product was thoroughly washed with millipore water for several times, followed by drying at 120°C for 12 hr. Finally, the obtained products were collected and calcined at 450°C for 2 hr in homemade programmable high temperature furnace. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 181–184 (2015)

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RESULT AND DISCUSSION Figure 1 shows the powder X-ray diffraction pattern of the TiO2 NR/NP. All the diffraction peaks are assigned to tetragonal crystal structure of anatase phase TiO2. The peaks at 25.17, 37.77, 48.07, 53.87, 54.97, 62.62, 68.77, 70.42 and 75.02 corresponded to the (101), (004), (200), (105), (211), (204), (116), (220) and (215) planes of anatase (JCPDS file no. 21–1272).

Fig. 1: Powder X-ray Diffraction Pattern of TiO2 NR/NP

These peaks indicate that the synthesized material is pure anatase phase. The sharp and strongest peak (101) at 25.17 degree of 2θ indicates the good crystalline quality of the TiO2 NR/NP. Figure 2 shows the nitrogen (N2) adsorption and desorption isotherm and pore size distribution of the TiO2 NR/NP. 140

2

BET surface area = 93.08 m /g

0.005

a)

9.1 nm

0.004 b)

0.003

3

100

Dv(d)[cm /Å/g]

3

N2 Volume(cm /g)

120

80 60 40

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20 0.0

0.2

0.4

0.6

0.8

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0.002 0.001 0.000 0

100

200

300

400

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Fig. 2: (a) Nitrogen Adsorption and Desorption Isotherm (b) Pore Size Distribution of NR/NP

The Brunauer-Emmett-Teller (BET) specific surface area (SBET) and average pore width of the TiO2 NR/NP are 93.08 m2/g, and 9.1 nm respectively. A sharp increase in adsorption volume of N2 was observed and located in the P/Po range of 0.6–0.9. The isotherm exhibits type IV pattern with hysteresis loop, characteristic of mesoporous material according to the classification of IUPAC.

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In order to identify the morphology of the TiO2 NR/NP, the synthesized product was dispersed in ethanol and subjected to the HRTEM analysis. Figure 3a shows the HRTEM image of TiO2 NR/NP. The result indicates that the formed nanostructures are composed of different size rods and particles.

Fig. 3: (a) HRTEM Image (b) SAED Pattern of TiO2 NR/NP

The formation of rods and particles are due to effect of ammonia in the autoclave, because the ammonia acts as a shape controlling agent for the nanostructures in the reaction environment. The length and diameter of the nanorods are approximately 25 and 100 nm respectively. The nanoparticles are spherical in shape with approximately 10 nm in size. In addition, the selected area diffraction pattern (SAED) shows good number of bright spots of the samples (Figure 3b). The bright spots indicate that the synthesized products are having good crystalline nature. The inner circle of the SAED image shows the (101) plane of the anatase phase. The electron diffraction results are in good agreement with powder X-ray diffraction pattern. Oriel Class A solar simulator equipped with 1.5 G air mass filter was used as the light source. The level of standard irradiance (100 mW/cm2) was determined with a calibrated c-Si reference solar cell. Figure 4 shows the current-voltage (I-V) characteristics behavior of dye sensitized solar cell. The synthesized material was used as a photoanode in DSSC. The results show the 3.08% photoconversion efficiency with 6.39 mA/cm2 of short circuit current (Jsc), 0.65 V of open circuit voltage (Voc) and 74.27% of fill factor (FF). The good fill factor might be due to the reduction of charge recombination with our hydrothermally synthesized NR/NP combination. Moreover, the NR/NP can offer to get better electron collection and better dye loading in DSSC.

Fig. 4: I-V Characteristics of DSSC

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CONCLUSION The mesoporous structure of TiO2 NR/NP has been successfully synthesized by hydrothermal method. The obtained nanorods have pure anatase phase, which is confirmed with powder XRD. The specific surface area and average pore width of the NR/NP are about 93.08 m2/g and 9.1 nm respectively. The HRTEM result shows that the synthesized products are having mixture of nanorods and nanoparticles (the TiO2 nanorods have ~25 nm width and ~100 nm length. The nanoparticles are ~10 nm in size). Additionally, the DSSC shows 3.08% conversion efficiency with 74% fill factor. The good fill factor might be due to the reduction of charge recombination with our NR/NP. The authors claim that this kind of nanostructures can be a potential candidate for DSSC. The TiO2 NR/NP nanostructures can be a right way to improve the solar cells performance. REFERENCES [1] O'Regan, B. and Grätzel, M., Nature 353, 737–40 (1991). [2] Jihuai, W., Zhang, L., Jianming, L., Miaoliang, H., Yunfang, H., Leqing, F. and Genggeng, L., Chem. Rev., 115, 2136–2173 (2015). [3] Hao, BW., Huey, H.H. and Xiong, W.L., Advanced materials, 24, 2567–2571 (2012). [4] Lijun, Y. and Wallace, W.L., Advanced materials, 25, 1792–1795 (2013). [5] Mathew, S., Yella, A., Gao, P., Humphry-Baker, R., Curchod, B.F.E., Ashari-Astani, N., Tavernelli, I., Rothlisberger, U., Nazeeruddin, M.K. and Gratzel, M., Nat. Chem., 6, 242 (2014). [6] Albero, J., Atienzar, P., Corma, A. and Garcia, H., Chem. Rec., 15, 803–828 (2015).

SERS Enhancement of Glucose Molecules on Layered Hybrid Ag/ZnO/Ag Nanostructure Anil Kumar Pal and D. Bharathi Mohan Department of Physics, Pondicherry University, Pondicherry E-mail: [email protected]

ABSTRACT Ag/ZnO/Ag hybrid structure was fabricated for the detection of D-glucose molecules. Photoluminescence spectra revealed the quenching due to Ag decreases the passivation of emitted light from ZnO. The reasons for enhancement, (i) the strong local electric field at nanometer gap between Ag nanoparticles, (ii) the hydrophobic surface of ZnO nanorods and (iii) the amplified electric field due to charge transfer from Ag to ZnO.

INTRODUCTION Surface enhanced Raman scattering (SERS) is recognized as one of the emerging techniques for the detection of chemical and biological species at the ppb levels [1]. More recently, metal-semiconductor based hybrid nanostructure has shown greater increment in Raman scattering efficiency of trinitrotoluene (TNT), glucose, hemoglobin, DNA and cancer cells [2]. We report a simple method of fabrication of Ag/ZnO/Ag hybrid structure using hydrothermal reaction and thermal evaporation techniques for the SERS detection of probe molecules such as D-glucose with the lowest concentration. EXPERIMENTAL DETAILS Ag metal powder (purity: 99.9%) was purchased from Sigma Aldrich, USA for the deposition of Ag films. Zinc nitrate hexahydrate (Zn(NO3)2 . 6H2O, extra pure) and hexamethylenetetramine (C6H12N4, extra pure) were purchased from FINAR, India for the hydrothermal growth of ZnO nanorods (NRs). D-Glucose (C6H12O6, purity: 99.5%) was purchased from Himedia, India used as probe molecule to testify the SERS activity of Ag/ZnO/Ag hybrid structure. Ultrathin Ag film with thickness of 7 nm was deposited on glass substrate by Thermal Evaporation. ZnO NRs were grown by immersing Ag film in solution of zinc nitrate hexahydrate and hexamethylenetetramine with equal concentration of 25 mM by refluxing at 90 °C. Once again, Ag NPs were decorated on ZnO NRs. A low volume of 5 µl of D-glucose of 10–3 M was drop casted on Ag/ZnO/Ag andallowed to dry at ambient condition. RESULTS AND DISCUSSIONS Ag film with thickness of 7 nm consists of closely packed spherical NPs of size 20 nm with the particle number density of 5.68 × 109 /cm2 and the RMS surface roughness of 1.23 nm (Figure 1(a)). The decorated Ag NPs on the surface of ZnO NRs are non-spherical with size varying from 30 to 70 nm. XRD shows the peaks of both ZnO and Ag confirming the formation of hybrid structure. The fluorescence quenching for Ag NPs decorated ZnO NRs (Figure 2(a)) could be due to more surface coverage formed by Ag NPs on the surface of ZnO NRs. The decorated Ag NPs decrease the passivation of light emitted from ZnO NRs which leads to decrease in emission intensity. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 185–186 (2015)

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Fig. 1: (a) AFM image Ag film of 7 nm thickness; (b) SEM image of ZnO NRs with Ag decoration and (c) XRD spectra of Ag/ZnO/Ag hybrid structure

Figure 2(b) shows many intense Raman peaks at 613, 661, 710, 770, 893, 915, 1112, 1180, 1260, 1312 and 1360 cm–1 in the range of 600 to 1400 cm–1 wave number. The maximum intense peak observed at 1360 cm–1 is assigned to the wagging of CH2 in α- and β-D-glucose [3]. Other SERS peaks such as 1260 cm–1 is assigned to twisting mode of CH2, 1120 cm–1 is ascribed to the bending mode of COH, 893 cm–1 is assigned to stretching mode of β-D-glucose, 710 and 770 are assigned to O-5-C-1-O-1 in α- and β-D-glucose respectively [3]. The decoration Ag NPs increases the number of hot spot sites which enables to detect D-glucose molecule with lower concentration of 10–3 M. Moreover, hydrophobic nature of ZnO NRs confines D-glucose molecules in a small area.

Fig. 2: (a) PL Spectra of ZnO NRs and Ag/ZnO/Ag Hybrid Structure, (b) Raman Spectra of Glucose Molecules on SERS Substrate

REFERENCES [1] Guerrini, L., Loureiro, I.R., Duarte, M.A.C., Lee, Y.H., Ling, X.Y., Abajo, F.J.G.D. and Pueble, R.A.A., Nanoscale, 6 (2014), 8368–8375. [2] Kneipp, K., Kneipp, H., Kartha, V.B., Manoharan, R., Deinum, G., Itzkan, I., Dasari, R.R. and Feld, M.S., Phys.Rev., E 57 (1998), 6281–6284. [3] Hirsch, L.R., Gobin, A.M., Lowery, A.R., Tam, F., Drezek, R.A., Halas, N.J. and West, J.L., Ann. Biomed. Eng., 34 (2006), 15–22.

Ag Nanoparticles Decorated on ZnO Nanrods Array Based SERS Substrate for Label Free Detection of DNA Anil Kumar Pal and D. Bharathi Mohan Department of Physics, Pondicherry University, Pondicherry E-mail: [email protected]

ABSTRACT Label free detection of DNA of Escherichia Coli bacteria was achieved on Ag nanoparticles decorated on ZnO nanorods array based Surface Enhanced Raman Scattering (SERS) substrate. Scanning electron microscope (SEM) cross sectional image corroborates the decoration of Ag nanoparticles (NPs) on ZnO nanorods (NRs) array. X-ray diffraction (XRD) pattern showed the formation of composite structure of Ag/ZnO/Ag hybrid structure. Confocal Raman spectroscopy study confirms the detection of DNA molecules even at lower concentration level of 10–6 M.

INTRODUCTION Surface Enhanced Raman Scattering (SERS) as a significant technique has gained considerable attention due to its extremely high sensitivity makes possible for single molecule detection [1]. Recently,metal/semiconductor based 3D hybrid nanostructures are achieving higher SERS effect to words the detection of glucose, hemoglobin, DNA and cancer cells due to their high surface to volume ratio preserving large active surface area [2, 3]. For the purpose of DNA detection, dye labeling is currently the foundation of most approaches requiring costly chemicals and complex chemistry. Here we approach simple Ag/ZnO/Ag hybrid structure for label free detection of DNA of Escherichia Coli bacteria. EXPERIMENTAL DETAILS High purity fused quartz substrates were used as the substrates for the fabrication of Ag/ZnO/Ag hybrid structure based SERS substrate. Ultrathin Ag film with thickness of 8 nm deposited on quartz substrate by Thermal Evaporation was used as catalytic layer for the growth of ZnO NRs. ZnO NRs array was grown by immersing Ag film in the equimolar solution (25 mM) of zinc nitrate hexahydrate and hexamethylenetetramine by refluxing at 90°C. Once again Ag NPs with film thickness 25 nm were decorated on ZnO NRs by Thermal Evaporation.DNA of laboratory strain Escherichia Coli was used as probe molecule to testify the SERS activity of Ag/ZnO/Ag hybrid structure. A low volume of5 µl with concentration of 10–6 Mwas drop casted on Ag/ZnO/Ag film and dried at ambient condition. RESULTS AND DISCUSSIONS Figure 1(a) shows the FESEM image of ZnO NRs array decorated with Ag NPs. It is observed that the ZnO NRs are grown vertically with aspect ratio of ~18. Ag NPs are non-spherical and decorated distinctly on the surface of ZnO NRs with size varying from 20 to 60 nm. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 187–188 (2015)

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The structural quality was confirmed through XRD measurement as shown in Figure 1(b). The XRD spectrum is found to have peaks of both ZnO and Ag as confirmed with JCPDS data no 36–1451 and 04–0783 respectively. The ZnO NRs are oriented along [001] direction with hexagonal structure andAg NPs are formed with FCC phase.

Fig. 1: (a) FESEM Image and (b) XRD Spectrum of ZnO NRs Decorated with Ag NPs Respectively

The SERS detection of DNA of laboratory strain Escherichia Coli with concentration of 10–6 M was probed through Raman spectrometer excited at 785 nm diode laser as shown in Figure 2. Many strong peaks are observed in the range of 450 to 1600 cm–1 are assigned to Adenine (A), Cytosine (C), Guanine (G), Thymine (T) and deoxyribose (d) of DNA [4].The local electric field strength increases at the nanometer gap between Ag NPs decorated on ZnO NRs which enables to detect the DNA molecules of lower concentration. Another reason for higher SERS effect is the hydrophobic nature of ZnO NRs which confines the drop casted DNA molecules with a small area.

Fig. 2: Raman Spectra of DNA of Escherichia Coli Adsorbed on Ag/ZnO/Ag Hybrid Structured SERS Substrate

REFERENCES [1] Guerrini, L., Loureiro, I.R., Duarte, M.A.C., Lee, Y.H., Ling, X.Y., Abajo, F.J.G.D. and Pueble, R.A.A., Nanoscale, 6, 8368–8375 (2014). [2] Chen, I.-C., Liou, Y.-C.M., Yang, J. and Shieh, T.-Y. J. Raman Spectrosc., DOI. 10.1002/jrs.2727 (2010). [3] Kneipp, K., Kneipp, H., Kartha, V.B., Manoharan, R., Deinum, G., Itzkan, I., Dasari, R.R. and Feld, M.S., Phys. Rev. E 57, 6281–6284 (1998). [4] Benevides, J.M., Wang, A.J., Marel, G.A. and Thomas, G.J., Biochem. 27, 931–938 (1988).

Facile Synthesis of Nanostructured Lithium Titanate for Battery Applications M. Selvamurugan, R. Dhilip Kumar and S. Karuppuchamy Department of Energy Science, Alagappa University, Karaikudi, Tamil Nadu E-mail: [email protected]; [email protected]

INTRODUCTION There is a remarkable interest in developing alternative and sustainable energy storage systems to meet modern society needs due to fossil fuel depletion. Compared with other existing energy storage systems, batteries are promising and lots of efforts have been taken by researchers to develop efficient device with affordable price. The development of Lithium-ion batteries with enhanced safety and a long cycle life is vital for mainly energy storage applications, in particular for electronics and electrotraction. Recently, researchers are attempting to develop the advanced nanomaterials for energy storage devices especially for batteries. Nanostructured materials of lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4) or oxides of vanadium (V2O5), manganese (MnO2) have been used as the cathode in Lithium ion batteries. Similarly nanostructured titanium oxide (TiO2) and or graphite were used as the anode materials in batteries [1–4]. Ti-based materials have been intensively investigated and measured as good potential negative electrode materials for lithium-ion batteries due to their safety, excellent rate capability and superior cyclic stability. Batteries have been used in several applications such as portable communication deviceslaptops, cellular phones, video cameras and cameras [5]. Now a day’s new kind of anode materials being developed in order to reduce the cost as well as to make highly efficient devices. Among the new anode materials, Li4Ti5O12 is one of the right choices for anode materials due to its superior performance [6, 7]. Li4Ti5O12 nanomaterials have been prepared using several methods for instance hydrothermal methods, sol-gel process, solid sate reaction, spray pyrolysis, hybrid microwave synthesis, gel-emulsion, solution growth technique and gel combustion [8–10]. In this work, nanostructured novel bimetal oxide Li4Ti5O12 was prepared by solution growth technique. The present research work describes the easiest synthetic pathway for Li4Ti5O12. EXPERIMENTAL All chemicals were of analytical grade and used without any further purification. Lithium titanate was prepared by solution growth technique. In a typical experimental route, titanium oxysulfate (TiOSO4) and lithium hydroxide (LiOH.H2O) were dissolved in double distilled water under strong stirring and consequently a precipitate was obtained. The precipitate was dried at 80°C in hot air oven for 10 hr. Finally, colorless powders were obtained which was then heat treated at 850°C in a muffle furnace for 3 h. The structural properties of synthesized powders were studied using various advanced characterization techniques. The X-ray diffraction (XRD) patterns of all the samples were measured on a (XPERT-PRO) diffractometer with monochromatic CuKα – radiation (λ = 1.5406Å). FT-IR V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 189–192 (2015)

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spectra of the samples were recorded on a (Thermo Nicolet 380, USA) spectrometer using a KBr pellet technique in the range of 4000–400 cm–1. The SEM - EDX were recorded on a (JEOL JSM6360LV) using an accelerating voltage of 30.0 kV.

RESULTS AND DISCUSSION Figure 1 depicts the XRD pattern of synthesized powder. XRD pattern show the peaks at18.34, 35.60 and 43.28. The appeared peaks clearly indicate the formation of Lithium titanate. This study clearly demonstrates the formation of lithium titanate by simple solution growth technique. It should be indicated that the appearance of three more peaks at 21.98, 22.21 and 22.63. These peaks are assigned to the reduced form of titanium oxide. The formation of titanium oxide along with lithium titanate may be beneficial in terms of storage capacity when it is used as anode material in the lithium ion batteries. Figure 2 shows the scanning electron microscopic image of lithium titanate. The SEM image clearly reveals that the formation of homogeneous morphological features. EDX spectrum of mixture

Fig. 1: XRD Pattern of Lithium Titanate

Fig. 2: SEM Image of Lithium Titanate

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of lithium titanate and titanium oxide nanopowders was measured (Figure 3). It was found from the EDX spectrum that the presence of appropriate percentage of Ti and O in the synthesized sample. It should be indicated that the Li does not present in EDX spectrum because the Li is light weight element. The investigations on the electrochemical property of the prepared Li4Ti5O12 materials are also carried out. The charge/discharge curve of lithium titanate anode is shown in Figure 4. The lithium titanate anode has been showing reversible discharge capacity of 83 mAhg–1 at first cycle. The better lithium ion storage performance of the synthesized Lithium titanate anode may be due to the good electronic conductivity. Further, investigations to optimize the electrochemical property of the prepared Li4Ti5O12 materials are underway in order to use them in lithium batteries.

Fig. 3: EDX Spectrum of Lithium Titanate

Fig. 4: Charge/Discharge Performance of Lithium Titanate

CONCLUSIONS Lithium titanate has been successfully synthesized by simple solution growth from aqueous precursor solution of titanium. The XRD studies reveal the formation of lithium titanate. SEM observation demonstrated the formation of homogeneous nanosphere morphology. The better lithium ion storage performance of the synthesized Lithium titanate anode was observed. REFERENCES [1] Liu, Y., Liu, D., Zhang, Q. and Cao, G., Engineering nanostructured electrodes away from equilibrium for lithium-ion Batteries, J. Mater. Chem, 21, 9969–9983, 2011. [2] Santhi, K., Manikandan, P., Rani, C. and Karuppuchamy, S., Synthesis of nanocrystalline titanium dioxide for photodegradation treatment of remazol brown dye, Appl. Nanosci. 5, 373–378, 2015. [3] Miyazaki, H., Matsui, H., Kuwamoto, T., Ito, S., Karuppuchamy, S. and Yoshihara, M., Synthesis and photocatalytic activities of MnO2-loaded Nb2O5/carbon clusters composite material, Microporous and Mesoporous Mater. 118, 518–522, 2009. [4] Thamima, M. and Karuppuchamy, S., Biosynthesis of titanium dioxide and zinc oxide nanoparticles from natural sources: A Review, Adv. Sci. Eng. Med., 7, 18–25, 2015. [5] Li, N., Chen, Z., Ren, W., Li, F. and Cheng, H.M., Flexible graphene-based lithium ion batteries with ultrafast charge and discharge rates, Proc. Natl. Acad. Sci. U.S.A., 109, 17360–17365, 2012.

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[6] Xie, L.L., Xu, Y.D., Zhang, J.J., Cao, X.Y., Wang, B., Yan, X.Y. and Qu, L.B., Facile synthesis and characterization of Li4Ti5O12 as anode material for lithium ion batteries J. Electrochem. Sci. 8, 1701 – 1712, 2013. [7] Wang, W., Tu, J., Wang, S., Hou, J., Zhu, H. and Jiao, S., Nanostructured Li4Ti5O12 synthesized in a reverse micelle A bridge between pseudocapacitor and lithium ion battery, Electrochemica Acta 68, 254– 259, 2012. [8] Lee, W.W. and Lee, J.M., Novel synthesis of high performance anode materials for lithium-ion batteries (LIBs), J. Mater. Chem., 2, 1589–1626, 2014. [9] Kumar, R.D. and Karuppuchamy, S., Synthesis and characterization of nanostructured Zn-WO3 and ZnWO4 by simple solution growth technique, J. Mater. Sci. Mater – Electron, 26, 3256–3261, 2015. [10] Kumar, R.D. and Karuppuchamy, S., Microwave-assisted synthesis of copper tungstate nanopowder for supercapacitor applications, Ceram. Int. 40, 12397–12402, 2014.

Zinc Oxide/Palladium Nanocomposites an Efficient Solar Active Photocatalyst for Environment Remediation Application Karuppannan Rokesh, Kulandaivel Jeganathan1 and Kandasamy Jothivenkatachalam Department of Chemistry, Anna University, BIT Campus, Tiruchirappalli, Tamil Nadu Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli, Tamil Nadu E-mail: [email protected]

1

ABSTRACT Zinc oxide - palladium (semiconductor-metal) nanocomposite materials were synthesized via a microwave technique and simple chemical reduction method. The synthesized materials were characterized by UV-Vis spectroscopy, photoluminescence spectroscopy, X-ray diffraction analysis and scanning electron microscopy. Zinc oxide modification with appropriate amount of palladium could greatly enhance its photocatalytic activity. The photocatalytic performance was investigated by degradation of rhodamine B and congo red as a model dye pollutants under solar light. The prepared composite materials are effectively degraded individual and mixture of dye under fixed conditions.

INTRODUCTION The dyes and organic compounds are strongly polluting the water resources with producing serious environment problems. The photocatalysis is an efficient technique to degrade the dyes and organic pollutants in water. The nanostructured semiconductors and their composite materials have been preferred to be photocatalyst. Zinc oxide (ZnO) is a wide band gap (3.37 eV) metal oxide semiconductor material. As prepared by a several techniques and a collection of different morphologies and sizes [1]. The nanostructured ZnO and ZnO - metal nanocomposite materials have been found huge attention in the field of photocatalysis and photoelectrocatalysis. Because of their high surfacevolume ratio, stability and surface charge (SPR effect of metal nanoparticles). Then the metal support on ZnO to decrease photoexcited electrons-holes recombination and increase the adsorption of pollutant on catalyst surfaces afterwards improved its photocatalytic oxidation and reduction process [2,3]. In account of ZnO/Pd nanocomposite materials were synthesized and characterized. Then its photocatalyic activity was investigated throughout photocatalytic degradation of rhodamine B (RhB) and congo red (CR) dyes. INTRODUCTION Nowadays textile industries using dyes and pigments are producing serious environmental problems relating to soil and water pollution. The photocatalytic process with metal oxide semiconductor is the most promising technique for water and waste water treatment [1]. Nanostructured metal oxide V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 193–196 (2015)

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semiconductor materials have been received a huge attention in environment remediation [2]. In addition, the noble metal support with semiconductor materials which greatly improve their catalytic properties [3].

EXPERIMENTAL The materials such as zinc acetate dehydrate, palladium acetate, hydrazine hydrate and sodium borohydride were obtained from Merck, and respectively rhodamine B and congo red were purchased from S.D. Chemicals, Mumbai. ZnO nanomaterials prepared by microwave assisted technique. Then ZnO/Pd nanocomposite materials have been prepared through facial chemical reduction method. The prepared materials characterized by UV-DRS recorded using Shimadzu UV-2550 UV-vis spectrometer, PL recorded using a JASCO-FP-6500 spectrofluorometer, XRD pattern on a Bruker Advance with Cu Kα radiation and morphology studied using Carl Zeiss FE-SEM. RESULTS AND DISCUSSION Optical Property The synthesized zinc oxide-palladium composite materials were observed strong absorption below 400 nm in near UV spectral region (Figure 1A). The (ZnO/Pd)NCM shows wide week absorption about the visible region. The (ZnO/Pd)NCM have exist slightly blue shift when compared to bare ZnO which point out the increased its band-gap energy [3]. The PL spectra showed wide band emission at visible region (Figure 1 B). This extended emission due to recombination of photogenerated hole-electron and oxygen vacancy site. The prepared materials observed weak emission obtained at 468 nm due to band edge free excitons. Then the materials were existing blue and green emission peaks at range of around 520–580 nm due to presence of oxygen vacancies in the materials [2]. The emission intensity of ZnO/Pd nanocomposites decreased with increase the palladium content.

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Fig. 1: (A) UV-Diffuse Reflectance Spectra (B) Photoluminescence Spectra (a) ZnO and ZnO/Pd Nanocomposites (b) 10:0.25, (c) 10:0.50, (d) 10:0.75 (e) 10:1.0

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Zinc Oxxide/Palladium Nanocomposites N an Efficient Sollar Active Photoccatalyst ...

1995

Crysttalline Propeerty The XRD X pattern of ZnO and (ZnnO/Pd)NCM (100:0.25) compoosite material is shown in Figure F 2. All thhe diffracction peaks in i XRD are confirmed c thaat the prepared hexagonall wurtzite struucture of ZnO (JCPD DS No. 36–14 451). The difffraction peakks of Pd in (Z ZnO/Pd)NCM was w not obserrved due to Pd P percenntage is much lesser in com mposite [3].

Fig. 2: XRD D Pattern of (a)) ZnO and (b) (Z ZnO/Pd)NCM (100:0.25)

Morp phology Stud dy The morphology m off ZnO/Pd (10:: 2.5)NCM nanoocomposite was w studied by FE-SEM imaage is shown in i Figuree 3. The synth hesized ZnO/P Pd composite displays d floweer buds-like morphology m wiith average sizze about 1 to 2 µm. Th he Pd nanoparrticles are depoosited on the ZnO Z surface can be confirm med by FE-SEM M r surface which formedd by agglomerration small paarticles. imagee. The buds haave exhibited rough

Fig. 3: FE E-SEM Image of ZnO/Pd (10:00.25) Nanocompposite

Photoocatalytic Stu udy The photocatalytic experiment was w carried outt by photodegrradation of rhoodamine B (R RhB) and conggo CR) under solaar light irradiaation (Figure 4). 4 The preparred ZnO and ZnO/Pd Z compoosites materiaals red (C 20 mgg was suspend ded in 50 mL of o RhB (5 ppm m), CR (50 ppm) and mixturre of dyes (RhhB 5 ppm + CR 50 ppm) in aqueou us solution. Thhen the dye soolution was exxposed to solaar light in opeen air conditioon betweeen 11 am to 2 pm. The conttinuous aeratioon was suppliied to mixing the t catalyst annd dye solutionn.

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The degradation process was studied and confirmed by UV-Vis absorbance spectroscopy. The (ZnO/Pd) nanocomposite materials showed better photocatalytic activity and degradation efficiency than that of bare ZnO. The result shows that the photocatalytic activities of (ZnO/Pd)NCM (10:0.25) reported maximum degradation efficiency of 99.3% (RhB), 100% (CR) and 56.7% (RhB + CR). Moreover the percentage of degradation was decreased when increase the Pd content in the composites [3,4].

Fig. 4: Photodegradation of RhB (Left), CR (Centre) and (Right) in Presence of Catalyst (a) ZnO and (ZnO/Pd)NCM (b) 10:0.25, (c) 10:0.5 (d) 10:0.75 & (e) 10:01.

CONCLUSIONS ZnO/Pd nanocomposite materials have been successfully synthesized and characterized by UV-DRS, PL, XRD and FE-SEM. The UV-DRS provide the optical properties and PL spectra explain the photochemical properties of prepared materials. The XRD pattern confirmed crystalline nature of composite materials. FE-SEM displays that the morphology of nanocomposite material are in a flower buds-like shape. The photocatalytic activity of synthesized (ZnO/Pd)NCM were studied by decomposition of rhodamine B and congo red under sun light. The zinc oxide - palladium nanocomposite materials behave as a efficient photocatalyst for environmental remediation. REFERENCES [1] [2] [3] [4]

Ahmad, M. and Zhu. J, J. Mater. Chem. 21 599–614, 2011. Zhang, Y., Wang, Q., Xu, J. and Ma, S., J. Alloys Compd. 258, 10104–10109, 2012. Zhong, J.B, Li, J.Z., He, X.Y., Zeng, J., Lu, Y., Hu, W. and Lin, K., Curr. Appl. Phy. 12, 998–1001, 2012. Jothivenkatachalam, K., Prabhu, S., Chandra Mohan, S. and Jeganathan, K., Desalin. Water Treat. 1–12, 2014. DOI: 10.1080/19443994.2014.906324.

Development of Polymeric Film Dosimeter Using Gamma Radiation Priyanka Oberoi, Chandra B. Maurya and Prakash A. Mahanwar1 Department of Chemistry, G.N. Khalsa College, Mumbai Department of Polymer and Surface Engineering, Institute of Chemical Technology, Mumbai

1

ABSTRACT An emerging technology evolved with enormous applications is radiation processing technology. Ionizing radiations are one of the type of radiation technology, which cause a number of chemical and physical changes in exposed materials. Dosimetry plays an important role in the quality control of radiation processing. A dosimeter is a gadget used to detect the level of exposure to ionizing radiation. The precise detection of ionizing radiation often seems to be a difficult task to perform in the food processing industry. An attempt has been put to develop precise and inexpensive polymeric dosimeter which can be used for controlling dosage of ionizing radiation for food sterilization purpose. Polymeric film using polyvinyl alcohol containing an acid-base indicator dye methyl orange and trichloroacetic acid was developed which changed its color when exposed to gamma rays at different doses. The control and irradiated samples were analyzed by color spectrophotometry UV/Vis spectrophotometry and FT-IR analysis. Keywords: Polyvinyl Alcohol, Methyl Orange, Trichloroacetic Acid, Gamma Radiations, Dosimeter.

INTRODUCTION The latest trend and technology of the 21st century using light photons, electromagnetic or ionizing radiations (γ-photons, α, β-particles) for various processes [1] have enormous applications in the fields of medicines, food irradiation, water and other mineral purification [2] and crosslinking of polymers & semiconducting materials [3].Ionizing radiations are harmful radiations, but if used accurately, it can be very efficient in use. Everyone is cognizant that gamma radiations are highly used in the pharmaceutical sector for sterilization of various instruments and other materials [4, 5]. Gamma radiations can be dangerous to humans if used at higher dose rates as they can cause cancer related diseases. In order to prevent the damage caused by the gamma radiation dosimeters are used. A Dosimeter is a gadget that which distinguishes the dose rate of ionizing radiation. It absorbs the radiation dose prompting physical changes brought on by radiations [6, 7]. Flexible polymeric dyed films and label dosimetry systems were developed by Gamma irradiation using Polyvinyl Alcohol, the films become colorless as the radiation causes bleaching effect leading the visual change in the dose absorbed [8–11]. Other radiation sensitive indicator film containing pH-indicating dye and substance containing chlorine or chloral hydrate were observed in other articles [12], [13]. In one of the experiments [3] the effect of Gamma-radiation on the structure as well as the morphology of the polymeric film of Polyvinyl Alcohol (PVOH) resulted in main chain bond partial scission and disappearance of –OH groups was observed. Polymeric films are mostly used for their easy V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 197–200 (2015)

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availability, lightness, reproducibility, convenience in handling. In the present work we have reported the irreversible change in the color of the polymeric film (Polyvinyl Alcohol) in the presence of an acid (trichloroacetic acid) and an acid-base pH indicator, azo dye methyl orange. PVOH was opted for its flexible properties and effects of Gamma-radiation on its structure which has already been reported [3, 14]. Methyl Orange which is commonly used as an indicator dye where the change in color of the dye has been sensitized by the addition of metal salts or strong acids.

MATERIALS Materials used for the current work were Polyvinyl alcohol (PVOH) obtained from Maya Plastics and Chemicals Pvt. Ltd., methyl orange procured from Thomas Baker and trichloroacetic acid from SD Fine Chemicals Pvt. Ltd. All the materials procured were of LR grade. METHOD The solution of methyl orange was prepared using 0.4 grams of the indicator dye and 10 ml of ethanol. Four grams of PVOH powder were added in 50 ml of de-ionized water, heated with continuous stirring at 120 RPM for 2 hours at 60°C. It was then cooled at room temperature. In this solution, methyl orange and 1ml diluted trichloroacetic acid (TCAA) were added simultaneously. The final solution was further stirred for an hour to homogenize. The obtained solution was then cast on to a Teflon sheet and allowed to set at room temperature for 48 hours. PVOH films were cut into the size of 1 × 1 cm2 and was given for Gamma-irradiation at 50, 100, 150, 200, 250 and 300 kGy dose. Gamma radiation was done using a γ-chamber with a source of 60Co emission radiation energy at the BRIT section of BARC, Turbhe. The films after Gamma irradiations were characterized by Gretag Macbeth’s color-Eye 7000A for CIEL*a*b values, UV/Vis Spectrometer 3000 to obtain the absorbance spectra in the range of 250 to 600 nm & Bruker FT-IR system was used for the range of 4000 to 400 cm–1. RESULTS AND DISCUSSION There was a visual color change in the samples from pink to brown after they were irradiated by gamma rays. Table 1 shows an increase in yellowness indicating the darker color of the film. This confirms that there was a color change in the samples. The L*a*b values calculated in the form of ΔE showed a rise in the values denoting a change in color to much darker side of the color [15]. Table 1: CIEL*a*b Values to Check Color of Samples of PVOH Containing Methyl Orange and TCAA L

A

B

Control

Samples

46.589

14.583

–0.607

0.442

ΔE

Yellowness 20.000

Whiteness 19.345

100 kGy

45.388

11.666

2.360

6.196

21.755

–4.651

150 kGy

44.944

8.548

2.706

2.743

22.302

–7.985

200 kGy

44.330

8.546

3.245

4.803

24.362

–13.081

250 kGy

45.337

7.691

4.061

5.817

25.376

–18.615

UV Analysis: Due to electronic & vibrational transitions in the absorbance, there are excitations that produce absorption bands. Figure 1 shows UV/Vis absorption spectra of the PVOH and methyl orange control film and those after irradiation with gamma rays for the dose of 50 to 300 kGy. Increase in the dose rate of radiation lead to the increase in absorbance due to more acid liberation from the samples.

Development of Polymeric Film Dosimeter Using Gamma Radiation

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The acid formation is due to the reaction of chlorine from tricholoracetic acid and H & OH free radicals from the polymer combined to form acid [12]. Changes in methyl orange are due to confined electrons in a molecule when hydrogen ions are attached or detached. The nitrogen bearing the positive charge is involved in a double bond reacts with the liberated acid and not when only reacted PVOH. Because PVOH films containing only methyl orange and not trichloroacetic acid showed no change in the film visually. 0.8 0.7 0.6

Absorbance

0.5 0.4 0.3 0.2 0.1 0.0 0

50

100

150

200

250

300

Dose (kGy)

Fig. 1: UV/Vis Spectra of Control and Irradiated PVOH+ Methyl Orange+ TCAA by Gamma Radiation for 50 to 300 kGy

Fig. 2: FTIR Analysis of Control and Irradiated Films of PVOH+ Methyl Orange+ TCAA

FT-IR analysis of Figure 2 shows vary in intensity of the samples as there was an increase in dose rate of Gamma radiations. Due to stretching and bending on irradiation, different bands at particular wave numbers were observed, indicating changes in the structure of the films. The band at 3344 cm–1 shows scission of the main bonds and change in –OH groups which, when combined with the –Cl from TCAA forms H-Cl (hydrochloric acid). This H-Cl reacts with methyl orange bringing about

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change in color as it is an indicator. The peak at 2932 cm–1 is due to amides. Carbonyl stretching of ester groups were indicated by peaks at 1750 cm–1 and 1713 cm–1 which was due to the addition of water in the solution. The band at 1422 cm–1 is due to CH2 bending, peaks at 1378 cm–1, 1328 cm–1 and 1251cm–1 methylene bonds of CH2 = CH2 stretching whereas peak at 1083 cm–1 shows C = O stretching. C-Cl groups were observed at peak numbers 673 cm–1 and 833 cm–1.

CONCLUSION It is observed that, Polyvinyl alcohol films containing an acid-base indicator dye methyl orange and trichloroacetic acid showed the change in the color with respect to dose rate of gamma radiation (from pink to brown). Yellowness (darkness) of samples increased as there was an increase in irradiation dosage was observed by CIEL*A*B method. Moreover, there is also an increase in absorbance value with respect to dose rate in UV spectrophotometer. In this research work, an attempt has been made to develop precise, reliable, durable, & cost effective polymeric composite dosimeter. These films thus, can be used for routine dosimetry systems for sterilization of food and other items necessary. REFERNCES [1] Shahid, “Dosimetry Characterization of Unknown Dye Polyvinyl Alcohol Films,” J. Basic Appl. Sci., pp. 508–512, 2012. [2] Akhtar, S., Hussain, T. and Shahzad, A., “The Feasibility of Reactive Dye in PVA Films as High Dosimeter,” J. Basic. Appl. Sci., pp. 420–423, 2013. [3] Bhat, N.V., Nate, M.M., Kurup, M.B., Bambole, V.A. and Sabharwal, S., “Effect of/ γ-irradiation on the structure and morphology of polyvinyl alcohol films,” Nucl. Instr. Mthds. Phys. Res., vol. 237, no. 3–4, pp. 585–592, 2005. [4] Galante, A.M.S. and Campos, L.L., “Mapping radiation fields in containers for industrial γ-irradiation using polycarbonate dosimeters,” Appl. Radiat. Isot., vol. 70, no. 7, pp. 1264–1266, 2012. [5] El-Kelany, M., “Effect of γ-radiation on the physical properties of poly(vinyl alcohol) dyed with tetra bromophenolphthalein ethyl ester,” vol. 2, no. 5, pp. 71–80, 2012. [6] Laranjeira, J.M.G., Khoury, H.J., Azevedo, W.M. De, Vasconcelos, E.A. De and Silva, E.F. Da, “Polyaniline nanofilms as a monitoring label and dosimetric device for gamma radiation,” Mater. Charact., Vol. 50, No. 2–3, pp. 127–130, 2003. [7] Feldman, L., Adair, P.C. and Hess, T.M., “Radiation dosimeter and method for measuing dosage,” US patent no. 4788126, 1988. [8] Rehim, F. Abdel, Ebraheem, S., Ba, W.Z. and McLaughlin, W.L., “A thin dyed-plastic dosimeter for large radiation doses,” Appl. Radiat. Isot., vol. 43, no. 12, pp. 1503–1510, 1992. [9] Rehim, F. Abdel, El-Sawy, N.M. and Abdel-Fattah, A.A., “Dyed grafted films for large-dose radiation dosimetry,” Appl. Radiat. Isot., vol. 44, no. 7, pp. 1055–1062, 1993. [10] Rehim, F. Abdel and Abdel-Fattah, A.A., “A thin-film radiation monitoring label and dosimetry system,” Appl. Radiat. Isot., vol. 44, no. 7, pp. 1047–1053, 1993. [11] Ebraheem, S., Eid, S. and Kovacs, A., “A new dyed poly (vinyl alcohol) film for high-dose applications,” Radiat. Phys. Chem., vol. 63, no. 3–6, pp. 807–811, 2002. [12] Sushilawati and Doyan, A., “Dose response & optical props of dyed PVA-TCAA polymeric blends irradiated with gamma rays,” J. Appl. Sci., pp. 2071–2077, 2009. [13] Ebraheem, S. and El-kelany, M., “Dosimeter Film Based on Ethyl Violet-Bromophenol Blue Dyed Poly (Vinyl Alcohol),” J. Poly. Chem., vol. 3, no.1, pp. 1–5, 2013. [14] Bhat, N.V., Nate, M.M., Bhat, R.M. and Bhatt, B.C., “Effect of γ-irradiation on polyvinyl alcohol films doped with some dyes and their use in dosimetric studies,” Indian J. Pure Appl. Phys., vol. 45, no. 6, pp. 545–548, 2007. [15] (X-Rite), “A Guide to Understanding Color Communication,” 2007. (https://www.xrite.com/documents/literature/en/L10-001_Understand_Color_en.pdf)

Vanadium (Oxide, Nitride and Carbide) Nanostructures Based Counter Electrodes in Dye Sensitized Solar Cell (DSSC) Applications P. Vijayakumar, M. Senthil Pandian, S. Mukhopadhyay1 and P. Ramasamy SSN Research Centre, SSN College of Engineering, Chennai, Tamil Nadu Centre of Excellence for Green Energy and Sensor System, Indian Institute of Engineering Science and Technology, Howrah, West Bengal E-mail: [email protected]

1

ABSTRACT In this work, we prepared vanadium oxide (VO), vanadium nitride (VN) and vanadium carbide (VC) as a counter electrode for application in dye-sensitized solar cells (DSSCs). The surface morphologies of VO, VN, VC samples were observed by the scanning electron microscopy (SEM). The powder X-ray diffraction (PXRD) was carried out to confirm the VO, VN, VC materials. BET surface area analysis confirms the surface area. Photovoltaic performance of the DSSC with VO, VN and VC counter electrode are 0.3%, 0.14% and 0.008% respectively.

INTRODUCTION Ever since the pioneering work of O’Regan and Graሷ tzel in1991, dye-sensitized solar cells (DSSCs) have continuously attracted great interest and currently represent the cutting edge of photovoltaic technologies owing to their high light-to-electricity conversion efficiency and cost-effective fabrication. Commonly, a DSSC is composed of a photoanodesensitized by a dye, an electrolyte containing a redox couple(triiodide/iodide), and a counter electrode (CE), usually made ofPt. However, the mass production of DSSC is restricted due tohigh costs and poor stability, To date, the best solar conversion efficiencyachieved for liquid electrolyte based DSSCs is about 11–13% [1–3].To resolve this issue, several low cost materials have been proposed to replace Pt, such as carbon materials, conductive polymers and composite materials. Recently, CoS, TiN, TiN/Carbon nanotube and NiN were applied in DSSC system as CE catalysts, resulting in decent results [4–7]. Therefore, it is prospective to develop economical new inorganic catalysts for triiodide reduction in DSSC system. In this work vanadium oxide (VO), vanadiumnitride (VN), vanadium carbide (VC) were synthesized as potential substitutes for Pt. EXPERIMENTAL PROCEDURE Nano-scaled VO, VN and VC were synthesized as follows. In the case of carbides, nitrides, and oxides, metal chlorides were used as metal precursors, ethanol (or urea) was used as the oxygen source, and urea could be used as either the carbon or nitrogen source depending on the urea/metal chloride molar ratio (nitrogen source at low urea/metal ratiosand carbon source at high ratios). Vanadium chloride (2.67 gm, VOCl3) was added to 10 ml ethanol while stirring for 30 mins. The metal source VOCl3 dissolved completely in ethanol which is oxygen source. The specified amount of V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 201–206 (2015)

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urea [0 gm, 3.00 gm, 7.20 gm] was then added to the solution, which was stirred for 2 h until the urea dissolved completely Subsequently, the solution was dried at 130°C. Finally, sintering the precursors at 800◦C-1100◦C for 3h–5h under N2 atmosphere, the VO, VNand VCare obtained.

Cell Fabrication Preparation of CE A mixture of 100 mg VO, VN, VC powder and 1gm ZrO2 pearl was dispersed in 2.5 ml iso propanol inside an agate pot. The mixture was milled for 8 h. Then it was ultrasonically dispersed for 30 min. The VO, VN and VC paste was prepared and coated on FTO substrate using Doctor Blade method. TiO2 Working Electrode and DSSC Fabrication TiO2 based working electrode was prepared by doctor blade technique [8]. TiO2 coated FTO substrate was sintered at 500 ºC for 30 min using home-made high temperature furnace. The organic N3 dye was dissolved in ethanol as solvent. The TiO2 coated FTO substrate was immersed in a dye solution for 24 h. Dye sensitized TiO2 electrode was rinsed with anhydrous ethanol and then dried in nitrogen flow. The Iodolyte electrolyte was used for the cell fabrication. The photoanode and counter electrode were assembled in a sandwich configuration. An active area of 0.8 cm × 0.8 cm was used to measure the cell performance.

RESULTS AND DISCUSSIONS The powder X-ray diffraction (XRD) patterns of the as-prepared sample are shown in Figure 1. These patterns correspond to VO, VN and VC of a Rhombohedral phase, cubicphase and cubic phase respectively, diffraction peaks of VO were observed at 24.32°, 33.01°, 36.25°, 38.54°, 41.24°, 49.83°, 53.94°, 63.16°. 65.21°, VN diffraction peaks were observed at 37.55°, 43.65°, 63.77°, 76.57° and VC diffraction peaks were observed at 37.35°, 43.86°63.55°, 76.98° with lattice parameters of VO a = 4.951Å and c = 14.002 Å (S.G: R3-C (167)), VN a = 4.1317 Å(S.G: Fm3-m(225), VC a = 4.13(S.G:Fm3-m(225)) (JCPDS card no. 84–0316(VO), 78–1315(VN), 89–5055(VC)).VC good crystallinity affect the catalytic activity, as well as the performance of the DSSC[9].

Fig. 1: Powder X-Ray Diffraction Pattern of a). Vanadium Oxide (VO) b) Vanadium Nitride (VN) c) Vanadium Carbide (VC)

Vanadium (Oxide, Nitride and Carbide) Nanostructures Based Counter Electrodes in Dye

203

The morphology of VO, VN and VC samples were observed by the FESEM images shown in Figure 2 (a, b, c). The morphology of the VO, VN sample was star like shape and VC was ofnanosheetshape. Thenanostars and nanosheets show no alignment and majority ofnanostars are similar in size.The nanostars and nanosheets may act as one-dimensional conductors and thus the nanostars are expected to be efficient in electron transfer to the electrolyte. BET surface area of as prepared sample is shown in Figure 3 (a, b, c). The multipoint BET surface area of the VO, VN and VC samples were14.25 m2g–1. 5.80 m2g–1, 5.96 m2g–1 respectively.The working mechanism of dye sensitized solar cell (DSSC) is shown in Figure.4 (a). In Figure 4(b, c, d) the DSSC using the three materials prepared at VO, VN and VC as counter electrodes show energy conversion efficiency of 0.3%, 0.14% and 0.008%.From the results, we can see that the surface area affects the performance of DSSC. The obtained photovoltaic parameters, such as the short-circuit current density (Jsc), opencircuit voltage (Voc), fill factor (FF), and overall conversion efficiency (η) forVO, VN and VCare summarized in the Table 1.

(a)

(b)

(c)

Fig. 2: FESEM Images of a) Vanadium Oxide (VO) b) Vanadium Nitride (VN) and c) Vanadium Carbide (VC)

204


(a)

(b)

(c)

Fig. 3: Nitrogen Adsorption–Desorption Isothermsof a) Vanadium Oxide (VO) b)Vanadium Nitride (VN) and c) Vanadium Carbide (VC) Table 1: Photovoltaic Parameters of DSSC with the VO, VN and VCcoated FTO CE Counter Electrode

Jsc (mA cm–2)

Voc (mV)

FF

η (%)

VO

1.75

626

0.34

0.38

VN

1.23

619

0.18

0.14

VC

0.06

584

0.23

0.008

205

Vanadium (Oxide, Nitride and Carbide) Nanostructures Based Counter Electrodes in Dye

(a)

(b)

0.0008

VN 0.0007 0.0006

VC

0.000016

Voc (V) = 0.584 2 Jsc (mA/cm )=0.063 Fill Factor (%)=23.13 Efficiency (%)=0.008

0.000014

0.0005 Current (A)

Current (A)

0.000018

Voc (V) = 0.619 2 Jsc (mA/cm )=1.235 Fill Factor (%)=18.93 Efficiency (%)=0.144

0.0004 0.0003

0.000012 0.000010 0.000008 0.000006

0.0002

0.000004

0.0001 0.0000 0.0

0.000002

0.2

0.4

0.6

Voltage(V)

(c)

0.8

1.0

0.000000 0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Voltage(V)

(d)

Fig. 4: a) DSSC Schematic Diagram, I-V Measurement of b) Vanadium Oxide (VO) c) Vanadium Nitride (VN) and d) Vanadium Carbide (VC)

CONCLUSION The synthesized VO, VN and VCwere characterized by PXRD, FESEM and BET surface area analysis. The VO, VN and VC based DSSC shows the photovoltaic performance and overall conversion efficiency (η) are 0.38%, 0.14% and 0.008% respectively.The cell performance can be attributed to the VO and VN nanostars network and VC nanosheets1-D efficient charge-transfer network. It is concluded that VO nanostars and high surface area as counter electrode may provide a potential feasibility for replacing Pt counter electrodes in DSSC applications. ACKNOWLEDGMENTS The authors are grateful toA. Narayanan, Technical Officer, Department of Chemistry, Indian Institute of Technology, Chennai forcarrying out the BET surface area analysis. We also thank Prof. R. Ramaraj, Director, Centre for Photo electrochemistry, MaduraiKamaraj University, Madurai for fruitful discussions.

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REFERENCES [1] Grätzel, M., Conversion of sunlight to electric power by nanocrystalline dye-sensitized solar cells, J. Photochem. Photobiol. A Chem., 164, 3–14, 2004. [2] Chen, C., Li, Y., Sun, X., Xie, F. and Wei, M. Efficiency enhanced dye-sensitized Zn2SnO4 solar cells using a facile chemical-bath deposition method. New J. Chem., 38, 4465–4470 (2014). [3] Mathew, S., Yella, A., Gao, P., Baker, R.H, Curchod, B.F.E., Astani N.A., Tavernelli, I., Rothlisberger, U., Nazeeruddin, M.K. and Gra¨tzel, M., Dye-sensitized solar cells with 13% efficiency achieved through the molecular engineering of porphyrin sensitizers. Nat. Chem., 2014, 6, 242–247. [4] Kay, A. and Grätzel, M., Low cost photovoltaic modules based on dye sensitized nanocrystalline titanium dioxide and carbon powder, Sol. Energy Mater. Sol. Cells., 44, 99–117, 1996. [5] Hong, W.J., Xu, Y.X., Lu, G.W., Li, C. and Shi, G.Q., Transparent graphene/PEDOT-PSS composite films as counter electrodes of dye-sensitized solar cell, Electrochem. Commun., 10, 1555– 1558, 2008. [6] Jiang, Q.W., Li, G.R. and Gao, X.P., Highly ordered TiN nanotube arrays as counter electrodes for dyesensitized solar cells, Chem. Commun, 44, 6720–6722, 2009. [7] Lin, J.-Y., Liao J.H. and Wei, T.-C., Honeycomb-Like CoS Counter Electrodes for Transparent DyeSensitized Solar Cells, Electrochem. Solid-State Lett, 14, D41–D44, 2011. [8] Pandikumar, A. and Ramraj, R., TiO2–Au Nanocomposite Materials Modified Photoanode with Dual Sensitizer for Solid-State Dye-Sensitized Solar Cells, J. Renew. and Sustain. Energy, 5, 043101, 2013. [9] Wu, M., Lin, X., Hagfeldt, A. and Ma, T., Low-Cost Molybdenum Carbide and Tungsten Carbide Counter Electrodes for Dye-Sensitized Solar Cells, Angew. Chem. Int. Ed, 50, 3520–3524, 2011.

Fabrication and Characterization of DSSC Using Agaricus Bisporus with Citrus Limonum as a Natural Metal Free Sensitizer A. Arulraj1,2, S. Veeramani1, 2, B. Subramanian3, G. Senguttuvan2 and V. Sivakumar2 1

Nanoscience and Technology, Anna University-Bharathidasan Institute of Technology, Tiruchirappalli 2 Department of Physics, Anna University- Bharathidasan Institute of Technology, Tiruchirappalli 3 Electro Chemical Material Science division, CSIR-CECRI, Karaikudi E-mail [email protected]

ABSTRACT The natural metal free dye from the Agaricus bisporus with Citrus limonum leaves extract with methanol and acetone medium respectively was used for the fabrication of Dye-Sensitized Solar Cells (DSSCs). Nanosized Titania (TiO2) which is used as a photoanode material. The hybrid dye sensitizer has broad absorbance of visible and near IR region confirmed using UV Visible spectrum showing the presence of Riboflavin (336 nm) and chlorophyll (436 and 662 nm) pigments in hybrid dye. FTIR studies confirms the presence of the functional molecules in the mixed dye for binding with TiO2. The anatase phase of TiO2 which is essential for DSSC is confirmed by XRD. The TiO2 photoanode was coated using Doctor-blade technique and Platinum (Pt) coated counter electrodes was done using Electron Beam Evaporation (EBE) technique on the Transparent Conducting Oxide (TCO) substrates. DSSC stack was fabricated by sandwiching these electrodes and injecting (I-/I3-) electrolyte and evaluate its performance using solar simulator. Keywords: Agaricus Bisporus, Citrus Limonum, Riboflavin, Chlorophyll, TiO2 Photoanode, Pt Counter Electrode, Doctor-Blade, Electron Beam Evaporation.

INTRODUCTION A dye sensitized solar cells (DSSCs) is the device used for converting visible light energy into electrical power, based on the sensitization of wide band gap materials [1]. The performance of the cell mainly depends on a dye used as photo-sensitizer. The absorbance and anchorage medium of the dye on the surface of TiO2 are important parameters that determines the efficiency of the cell [2]. Generally, transition metal coordination compounds (ruthenium complexes) are used as effective sensitizer, due to their intense charge transfer absorbance in the whole medium of visible of visible range [3]. Moreover, the process to synthesize the complexes is costly and complexity [4]. So alternatively, natural dyes can be used as photo-sensitizer with an acceptable efficiency. The advantages of natural dyes includes their green environment, availability and its low cost [5]. The sensitization of semiconductors using natural pigments is usually ascribed to anthocyanins and riboflavins. Riboflavins based on DSSCs are interacted with the semiconductor nanostructures [6]. Hydroxyl and carbonyl groups present in riboflavin molecule can bound to the surface of the porous TiO2 film. This makes electron transfer from the riboflavin molecule to the conduction band of TiO2 [7]. The properties of riboflavin pigments are described in connection with particular applications reviewed and used as the photochemical catalytic application with Zinc Oxide (ZnO) [8]. As reported V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 207–210 (2015)

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[1–8], riboflavin from natural sources gives the sensitizing performances. In this work, DSSCs was prepared using natural dyes extracted from the agaricus bisporus (white button mushroom) and citrus limonus (lemon leaves). The extracted dyes were mixed together to form a hybrid dye and is been used as a sensitizer for DSSCs. The performance of this hybrid dye was also investigated.

EXPERIMENTAL Materials and Methods The extract of agaricus bisporus and citrus limonum, Titanium dioxide (TiO2), Methanol, Acetyl Actone, Iodine, Lithium Iodide (KI), Acetonitrile, Triton X-100, Acetic acid, Polyethylene Glycol (PEG), TCO substrates, Platinum substrates and Deionised water was used for the fabrication of DSSCs. Preparation of Photo-Sensitizer The riboflavin pigments was extractedby taking 50 g of agaricus bisporus and crushed in 50 ml of methanol solution and then by filtering using whatman filter paper. Chlorophyll pigments was extracted by taking 3 g of fresh green citrus limonum leaves are grind in a mortar with 15 ml of acetone. Now both the pigments are mixed together in a ratio of 1:1 to form a hybrid photo-sensitizer for DSSC. Preparation of TiO2 Paste TiO2 paste was prepared by using 3g of procured TiO2 in a mortar and grind powder by adding 5 ml of acetic acid in incremental order. The grinding is made vigorously for 30 minutes until the lump free paste is obtained. Then a few drops of Polyethylene glycol (PEG) is added and two drops Triton X100 been added as surfactant and grinding is done for few more minutes to obtain TiO2 paste. Preparation of Electrolyte Solution The liquid electrolyte solution was prepared using 3.5 g of lithium iodide (LI) to 50 ml of acetonitrile as solvent, with stirring for an hour. Then 1g of Iodine (I2) is added to the above solution and stir for few minutes. The electrolyte solution is taken and stored in dark container [9]. Preparation of Photoanode The photoanode is prepared by depositing TiO2 paste on the conducting of the TCO substrate using Doctor-blade technique. After depositing the TiO2 paste it undergoes annealing @ 500ºC for an hour. Then the TiO2 coated substrate is made immersed in the photo-sensitizer for 18–20 hours so that the dye gets attached to the mesoporous surface of the TiO2 film. Preparation of Counter Electrode Platinum (Pt) counter electrode is coated on the conducting side of TCO substrate using Electron Beam Evaporation technique [10]. RESULTS AND DISCUSSION UV Visible Spectrum Analysis The UV Visible spectrum of the extracted natural metal free hybrid sensitizer is shown in Figure 1. It shows the absorption in the range of UV, visible and near IR region with the corresponding wavelength of 318 nm, 436 nm, 470 nm and 662 nm.

Fabrication and Characterization of DSSC Using Agaricus Bisporus

209

Fourier Transform Infra Red Analysis FTIR spectra of the natural hybrid sensitizer is shown in Figure 2. The characteristics peak appeared around 3477 cm–1 and 1642 cm–1 shows the presence of hydroxyl and carbonyl functional molecules.

Fig. 1: UV-Visible Spectrum

Fig. 2: FTIR Spectrum

X-ray Diffraction Analysis XRD pattern of TiO2sample is shown in Figure 3. The pattern matches with (JCPDS No.: 73–1764) confirms the presence of anatase phase in the TiO2 sample. CHARACTERISTICS CURVE The performance of an assembled DSSC using metal free natural photo sensitizer with platinum counter electrodes is evaluated using solar simulator of light illumination 100 mW/cm2.The characteristics curve is shown in Figure 4, from the obtained characteristics curve the photo conversion efficiency of assembled DSSC was determined using open circuit voltage (Voc), short circuit current (Isc), fill factor (F.F), the efficiency was calculated from the equation, Efficiency (η) = (Isc*Voc*FF/Pin)*100%

Fig. 3: XRD Pattern

Fig. 4: IV Characteristics Curve

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CONCLUSIONS In conclusion we have fabricated a cost effective and simple DSSC with the combination of hybrid dye from agaricus bisporus and citrus limonumleaves with platinum as a counter electrodes. The absorbance range of the sensitizer was studied using UV Visible spectrum and the functional molecules present in the sensitizer was studied using FTIR analysis. The anatase phase of the TiO2nanoparticles was confirmed by using XRD analysis. From the IV characteristics studies, the efficiency of the metal free natural hybrid sensitizer is obtained to be of 0.5%. The photo conversion efficiency of the sensitizer is comparatively small with other metal complexes, but we can confirm that the natural metal free hybrid sensitizer made from agaricus bisporus has the ability of generating the electricity. REFERENCES [1] Gratzel, Michael, “Review Dye-Sensitized Solar Cells”, Journal of Photochemistry and PhotobiologyPhotochemistry Rev. 4, 145(2003). [2] Wongcharee, Khwanchit; Meeyoo, Vissanu and Chavadej, Sumaeth, “Dye-sensitized solar cell using natural dyes extracted from rosella and blue pea flowers”, Elsevier doi:10.1016/j.solmat.11.005(2006). [3] O,Regan, Brain and Gratzel, Michael, “A low cost, high efficiency solar cell based on dye-sensitized colloidal TiO2 films”, Nature 353, 737 (1991). [4] Smestad, Greg P. and Gratzel, Michael, “Demonstrating Electron Transfer and Nanotechnology: A natural dye sensitized Nanocrystaline energy converter”, Journal of Chemical education, 75, 6 (1998). [5] Gould, Kevin; Davies, Kevin and Winefield, Chris, “Anthocyanins biosynthesis, functions and applications”, Springer Science USA (2009). [6] Bertil et al., “Riboflavin as an electron donor in photochemical reactions”, Nov. 29, 1960. [7] Luque, Antonio and Hegedus, Steven, “Handbook of photovoltaic science and engineering” John Wiley & Sons Ltd Publishers, 1st ed., UK (2003). [8] Vaishnavi, E. et al., “Photochemical events during the photosensitization of colloidal ZnO nanoparticles by Riboflavin”, Bull. Mater. Sci., Vol. 35, No. 7, December 2012, pp. 1173–1179. [9] Bin, LI; Liduo, Wang; Deqiang, Zhang and Yong, QUI, “Preaparation and characterization of compact TiO2 film used in Gratzel solar cells”, Chinese Science Bulletin 49, 123 (2004). [10] Chou, Chuen-Shii; Hsiung, Chin-Min; Wang, Chun-Po; Yang, Ru-Yuan and Guo, Ming-Geng, “Preparation of a counter electrode with p-type NiO and its applications in Dye sensitized solar cells”, International Journal of Photoenergy, Vol. 2010, Article Id 902385.

Green Synthesis, Characterization of CUO Nano Particles Using Mimosa Pudica Leaf Extract as Fuel and Their Antibacterial Activity H.J. Amith Yadav, B. Eraiah, H. Nagabhushana1, R.B. Basavaraj1, K. Lingaraju2, H. Rajanaika2 and B. Daruka Prasad3 Department of Physics, Bangalore University, Bangalore Prof C.N.R. Rao Centre for Nano Research (CNR), Tumkur University, Tumkur 2 Department of Studies and Research in Environmental Science, Tumkur University, Tumkur, Karnataka 3 Department of Physics, B M S Institute of Technology, Yelahanka, Bangalore 1

ABSTRACT We report on the synthesis of copper oxide nanoparticles by low temperature combustion synthesis using Mimosa pudica leaf extract as fuel. The CuO nanoparticles are characterized with the help of PXRD, UV–Visible and SEM techniques. The particles are well crystalline in nature and average crystallite sizes were found to be 27~40 nm. The morphology of the nanoparticles can be controlled by tuning the amount of Mimosa Pudica extract. Further, as-formed CuO nanoparticles exhibit significant antibacterial activity against pathogenic bacterial strains namely Gram – veEscherichia coli, Gram +ve bacteria Staphylococcus aureus. The current study demonstrates that the utilization of Mimosa pudica extract as a fuel for the efficient synthesis of CuO nanoparticles. Keywords: Mimosa Pudica Leaf Extract, Combustion Method, Antibacterial Activity.

INTRODUCTION With the remarkable development of science and technology, environmental pollution, specially air pollution, both indoors and outdoors, have become a universal problem [1]. Therefore, it has provided the impetus to carry out fundamental and applied research on sensors with the ability to detect polluting gases. It was well known that copper oxide (CuO) was typical p-type semiconductor and widely used forgas sensors. Till date many methods were developed for the synthesis of nanostructured Cu-based materials including nanopaticals, nanorods, nanoribbons, nanofilms, nano spheres, hollow microspheres and hierarchical nanostructures etc [2–6]. Nevertheless, these methods have lots of drawbacks with respect to initial precursors, large defects during preparation of NPs etc. Solution combustion method has attracted increasing interest due to simple experimental setup scale up for industrial applications; product will be in nano scale, large surface to area etc. In the present work CuO nanoparticles were prepared via solution combustion route using Mimosa podica leaf extract and well characterized by means of XRD, UV-Vis, and SEM etc. Further antibacterial studies were performed on Gram –veEscherichia coli and Gram +ve bacteria Staphylococcus aureus. EXPERIMENTAL Synthesis CuO nanoparticles were prepared by eco-friendly green combustion route using Mimosa Pudica leaf extract as fuel. The copper nitrate trihydrate (Cu (NO3)2.3H2O) was procured from Sigma Aldrich V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 211–214 (2015)

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(AR) and used without further purification. Stoichiometric amount of Cu (NO3)2.3H2O was dissolved with 0.2 g of Mimosa pudica leaves extract in 10 ml of distilled water. The mixture was kept in a preheated muffle furnace at 400 ±10°C. The reaction was completed within 5 min. And a fine black colored material was obtained. The synthesis of nanoparticles were repeated with different concentrations of the plant extract such as 0.3, 0.4, 0.5, 0.6g etc. The obtained product was stored in airtight container until further use.

RESULTS AND DISCUSSION PXRD, SEM and UV-Visible Absorption Spectrum Figure 1 shows typical XRD patterns of the as formed CuOnanoparticles were obtained for 0.5 g Mimosa podica plant extract. It was observed that a monoclinic (JCPDS: 80–1916) structure with a lattice constant a = 4.6965 Å, b = 3.4324 Å and c = 5.1329 Å, β = 99.5287 Å. No further impurity peaks other than CuO were observed in the XRD pattern indicating the high phase purity. The broadening of the diffraction peaks indicates that the crystal size was small. The average crystallite size of the CuO nanoparticles calculated by Debye–Scherer’s formula as D = kλ/β cos θ. where D – the particle size (nm), k - a constant equal to 0.94, λ - the wave length of X-ray radiation (1.5406°A),β – the full-width at half maximum (FWHM) of the peak(in radians) and 2θ – the Bragg angle (degree). The average crystallite size was found to be in the range 20–47 nm.

Fig. 1: PXRD Patterns of CuONPs Prepared with Mimosa Pudicaextract (0.5 mg)

Figure 2 shows the SEM images of CuO NPs. It clearly shows that the particles were almost porous in nature with agglomeration. Further, it was observed that micro structure was independent of the concentration of plant extract. (a)

(b)

Fig. 2: (a & b) SEM Images of CuO Nanoparticles Prepared in Mimosa pudica Leaves Extract with Different Magnification

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Absorbance(a.u)

Figure 3 shows the UV-Visible absorption spectrum of CuONps exhibiting the maximum absorption peak at 358 nm which was blue shift with increasing concentration of the plant extract in the reaction mixture during the synthesis by combustion process.

300

358 nm

325

350

375

400

425

450

475

500

Wavelength (nm)

Fig. 3: UV-Visible Absorption Spectrum of CuONps

Antibacterial Activity The antibacterial properties of the CuONps were evaluated against Gram –ve bacteria E. coli, and Gram +ve bacteria S. aureususing agar well diffusion method [7]. Antibacterial activity of CuO NPs was studied against Gram +veS. aureus and Gram-veE.coli, bacterial strains using agar well diffusion method. The highly significant antibacterial activity in E. coli (12.00±0.00) was less significant in S. aureus (6.33±0.33). Mechanism of the bactericidal effect of nanoparticles was generally was been attributed to the decomposed of bacterial outer membranes by (ROS), primarily _HO which lead to phospholipid peroxidation and ultimately cell death. The pathogenic bacterial strains of Gram +ve bacteria S. aureusand Gram-ve bacteria E. coli, with 400 and 800 µg/µL concentration of CuONps showed thegraphical representation of antibacterial activity of CuO nanoparticles were shown in Figure 4 The data was shown in Table 1.

Fig. 4: Show s the Graphical Representation of Antibacterial Activity of CuONps

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Table 1: Antibacterial Activity of CuO Nanoparticles against Pathogenic Bacterial Strains

E.coli (Mean ± SE)

S.aureus (Mean±SE)

Standard (5 µg/50 µL)

10.12 ± 0.03*

11.17 ± 0.3*

CuO (400 µg/40 µL)

2.33 ± 0.12**

2.00 ± 0.00

CuO 800 µg/80 µL)

4.67 ± 0.06**

4.33 ± 0.09**

Treatment

Values are the mean ± SE of inhibition zone in mm. *Symbols represent statistical significance, *P < 0.05, **P < 0.01 as compared with the control group.

CONCLUSIONS This study reports that green synthesis of CuONps prepared by solution combustion method using Mimosa pudica leaf extract as fuel. The PXRD patterns showed monoclinic phase and the UV–visible absorption spectrum indicates blue shift with increasing concentration of the plant extract in the reaction mixture during the synthesis. SEM images reveal that the particles appear to be irregular in shape. CuONps exhibited significant antibacterial activity against both Gram –ve and Gram +ve bacterial strains such as E. coli, and S. aureus. Among them, E. coli and S. aureus show significant zone of inhibition to CuONps compared to the positive control (Ciprofloxacin). The study successfully demonstrates the convenient utilization of Mimosa pudica leaves extract as a fuel to get structurally and morphologically interesting and potentially antibacterial properties. REFERENCES [1] Eltzov, E., Pavluchkov, V., Burstin, M. and Marks, R.S., Creation of a fiber optic basedbiosensor for air toxicity monitoring, Sensors and Actuators B., 155 (2011), 859–867. [2] Taubert, A., Stange, F., Li, Z.H., Junginger, M., Guünter, C., Neumann, M. and Friedrich, A., CuO nanoparticles from the strongly hydrated ionic liquid precursor (ILP) tetra-butylammonium hydroxide: evaluation of the ethanol sensing activity, ACSApplied Materials & Interfaces, 4 (2012), 791–795. [3] Yang, C., Su, X.T., Xiao, F., Jian, J.K. and Wang, J.D., Gas sensing properties of CuOnanorods synthesized by a microwave-assisted hydrothermal method, Sensorsand Actuators B, 158 (2011), 299–303. [4] Gou, X.L., Wang, G.X., Yang, J., Park, J. and Wexler, D.J., Chemical synthesis, characterisation and gas sensing performance of copper oxide nanoribbons, Materials Chemistry, 18 (2008), 965–969. [5] Choi, Y.H., Kim, D.H., Hong, S.H., Hong, K.S., H2and C2H5OH sensing characteris-tics of mesoporous p-type CuO films prepared via a novel precursor-based inksolution route, Sensors and Actuators B, 178 (2013), 395–403. [6] Zhang, J.T., Liu, J.F., Peng, Q., Wang, X. and Li, Y.D., Nearly monodisperse Cu2O and CuOnanospheres: Preparation and applications for sensitive gas sensors, Chemistry of Materials 18 (2006), 867–871. [7] Perez, C., Paul, M. and Bazerque, P., Actabiol. Med. Exp., 15, 113–115(1990).

Chemosynthesis, Characterization and PEC Performance of CdZn(SSe)2 thin Films by Arrested Precipitation Technique (APT) S.K. Jagadale, D.B. Shinde, R.M. Mane, K.V. Khot, V.B. Ghanwat, P.N. Bhosale and R.K. Mane Materials Research Laboratory, Department of Chemistry, Shivaji University, Kolhapur E-mail: [email protected]; [email protected]

ABSTRACT In the present work, we have used simple, cost effective arrested precipitation technique (APT) to deposit CdZn(SSe)2 thin film. Preparative conditions were optimized during initial stage of experimentation to obtain good quality CdZn(SSe)2 thin film. As deposited film was studied for its structural, morphological, optical, and compositional analysis by XRD, SEM, UV-Vis-NIR spectrophotometer and EDS analysis techniques respectively. XRD study revealed that the film was polycrystalline in nature and exhibit hexagonal crystal structure. The SEM micrograph shows the formation of spherical surface morphology. EDS results confirm the presence of Cd, Zn, S and Se elements in the synthesized thin film. The band gap value of thin film was calculated from the absorption spectra which is found to be 1.8 eV. From J–V measurements, photo-conversion efficiency is found to be 0.07%.

INTRODUCTION The II-VI compounds are becoming interesting and important because of their major applications in solar cells [1] and opto-electronic devices [2]. The variety of techniques presently used for the synthesis of cadmium and zinc chalcogenidesemiconductor thin films [3–8]. In all this methods, APT is self organized, cost effective, and suitable for large area deposition [9] presently used by us to prepare CdZn(SSe)2 thin films. In the present investigation, we propose the synthesis, growth mechanism, optostructural, morphological, compositional and photoelectrical properties of quaternary CdZn(SSe)2 thin films by arrested precipitation technique (APT). EXPERIMENTAL DETAILS All the chemicals used in the present investigation are of AR grade and used as received without further purification. The Cadmium sulfate hydrate (CdSO4.3H2O), zinc sulfate hydrate (ZnSO4.7H2O), thiourea (NH2-CS-NH2), and sodium selenosulfite (Na2SeSO3), were used as precursors for Cd2+,Zn2+, S2–, Se2–ions. Ammonia is used to maintain pH of reaction bath and triethanol amine was used as complexing agent. For measuring the PEC performance, sulfide/polysulfide redox electrolyte is used. The solution of sodium selenosulfite was prepared by refluxing selenium metal powder with Na2SO3 at 90°C for 9 h. Commercial glass slides and FTO have been used as the substrate for thin film deposition. In APT method metal ions of the precursors are arrested using a stable organic complexing agent (in this case triethanol amine) in alkaline medium. All the preparative parameters such as pH of reaction bath, precursor concentration and temperature are optimized initially to 10.8±0.2, 0.1M and 55±2°C respectively, to obtain good quality thin films. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 215–218 (2015)

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The optical absorbance was measured using UV-Visible NIR- spectrophotometer (Hitachi model 330, Japan) in the wavelength range 300–1100 nm. The structural analysis is done by X-ray diffraction (XRD) analysis [Brukers AXS Analytical Instruments. Model D2 PHASER] with Cu Kα target for the 2θ ranging from 10° to 100°.The compositional analysis of deposited thin film was determined by energy dispersive X-ray analysis (EDS) attached to scanning electron microscope (SEM). (JEOL-JSM- 6360A). J-V measurements (PEC) were recorded on semiconductor characterization instrument (SCS-4200 Keithley, Germany) using a two electrode configuration.

RESULTS AND DISCUSSION Reaction Mechanism for Thin Film Formation In the present investigation,we have successfully deposited CdZn(SSe)2 thin films by arrested precipitation technique. APT is based on Ostwald ripening law [9]. The mechanism is given below. In alkaline medium Cd-TEA and Zn-TEA complex slowly releases Cd2+and Zn2+ ions at pH 10.8±0.2 (NH4)4[Cd2N(CH2–CH2–O)3] + 6 H2OCd2++ [2N (CH2–CH2–OH)3]+4NH4OH +2OH– … (1) 2+ – (NH4)4[Zn2N(CH2–CH2–O)3] + 6 H2OZn + [2N (CH2–CH2–OH)3]+4NH4OH +2OH … (2) Na2SeSO3and thioureadissociates in alkaline medium to produce Se2–and S2– ions respectively Na2SeSO3+ OH–Na2SO4 + HSe– → HSe–+ OH–Se2– + H2O –

–

–

… (3) –

2–

(NH2)2C = S + OH (NH2)2C = O + HS + H2O → HS + OH → S + H2O

… (4)

Overall reaction is … Cd2+ + Zn2++ Se2– + S2–CdZn(SSe)2

… (5)

Optical Study The optical absorption was measured at room temperature for the CdZn(SSe)2 thin films in the wavelength region of 300–1100 nm. The linear nature of the optical absorption plot confirms the direct allowed transition and is obtained by using formula given in[9].

Fig. 1: Optical Absorption Plot and Inset: Band Gap Energy Plot of Synthesized Thin Film

Fig. 2: X-ray Diffraction Pattern of CdZn(SSe)2 thin Film

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X-Ray Diffraction Study The Figure 2. Shows X-ray diffraction pattern of CdZn(SSe)2 thin film. Four peaks observed at diffraction angle of 24.92(100), 26.20(100), 41.92(110), and 71.87 (105) corresponding to 3.568, 3.396, 2.149 and 1.312 ‘d’ values respectively. These values are matched with standard JCPDS data (card No. 80–006, 35–1469 and 77–2307). XRD data demonstrate polycrystalline phase and a hexagonal crystal structure of CdZn(SSe)2 thin film. The crystallite size is calculated by using Debye Scherer formula. The calculated crystallite size is 20 nm. SEM/EDAX STUDIES Figure 3 shows SEM micrograph of surface morphology of CdZn(SSe)2 thin film which exhibits well adherent, smooth and uniform distribution of nanosphere, which cover all the substrate surface. The average grain size is calculated by standard scale bar methodand is found to be 120 nmrange. The EDS spectrum for CdZn (SSe)2 film is shown in Figure 4. The EDS spectrum indicates the present peaks for the Cd, Zn, S and Se elements in the synthesized thin film. Also spectrum shows peak for platinum, which is used for coating the sample during analysis.

Fig. 3: SEM Micrographs of CdZn(SSe)2 thin Film

Fig. 4: EDS Spectrum of CdZn(SSe)2 thin Film

PHOTOELECTROCHEMICAL PERFORMANCE The PEC performance of deposited CdZn(SSe)2 thin film was checked standard two electrode configuration, both in dark and under light illumination of a 500 W tungsten filament lamp having a light intensity of 30 mW cm–2, in sulphide/polysulphide redox electrolyte. The current density–voltage (J–V) characteristics ofglass/FTO/CdZn(SSe)2/electrolyte/graphite were measured. J–V characteristic curve of CdZn(SSe)2 thin film in dark display diode-like rectifying characteristics. Upon light illumination, the magnitude of the open circuit voltage (Voc) increases with negative polarity towards the CdZn(SSe)2electrode, indicating cathodicbehavior and which confirms that CdZn(SSe)2thin film is p-type. The output parameters of the PEC solar cell, i.e. light conversion efficiency (η %) and fill factor (FF), were calculated from eqn. (13) and (14), respectively. FF η%

… (13) 100

… (14)

is the open circuit voltage. Jmax and Vmax are Where JSC is the short-circuit current density and the maximum current density and the maximum voltage, and Pin is the input light intensity (30 mW cm–2). From the J–V measurements, the obtained values of JSC, VOC and FFfor the sample is0.1917 mA cm–2, 457.2 mV and 0.27 respectively. The resultant conversion efficiency of the synthesized thin film is 0.07%.

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Fig. 5: J-V Measurement Curve of CdZn(SSe)2 thin Films

CONCLUSIONS The arrested precipitation technique is found to be the most convenient method for deposition of metal chalcogenide thin films. Optical band gap energy value was found to be 1.87eV. The XRD study revealed the polycrystalline nature with purehexagonal crystal structure of the CdZn(SSe)2 thin film. The SEM micrograph shows that the spherical grain structure of the surface without any pinholes.EDS results confirm the presence of Cd, Zn, S and Se elemental in synthesized thin film. The J-V measurement curve shows the efficiency of CdZn(SSe)2 film was found to be 0.07%, It reveals that CdZn(SSe)2 thin films deposited by APT technique, show potential candidate for solar cell application. REFERENCES [1] Chavan, S. and Sharma, R., New trends to grow the n-CdZn(S1–xSex)2/p-CuIn(S1–xSex)2 heterojunctionthin films for solar cell applications, Solar Energy Mate. And Solar Cells, 90(9), 1241–1253, 2006. [2] Sharma, M., Kumar, S., Sharma, L.M., Sharma, T.P. and Husain, M., CdS sintered films: growth and characteristics, Physica B: Condensed Matter, 348, 15–20, 2004. [3] Chandramohan, R., Mahalingam, T., Chu, J.P. and Sebastian, P.J., Preparation and characterization of semiconducting Zn1–xCdxSe thin films, Solar Energy Materials and Solar Cells, 81, 371–378, 2004. [4] Chavhan, S.D., Senthilarasu, S. and Lee, S.H., Annealing effect on the structural and optical properties of a Cd1–xZnxS thin film for photovoltaic application, App. Surf. Sci., 254, 45439–4545, 2008. [5] Ilican, S., Zor, M., Caglar, Y. and Caglar, M., Optical characterization of the CdZn(S1–xSex)2 thn films deposited by spray pyrolysis method, Optica Applicata, 36(1), 2006. [6] Pathan, H.M. and Lokhande, C.D., Deposition of metal chalcogenide thin films by successive ionic layer dsorption and reaction (SILAR) method, Bull. Mater. Sci., 27, 85–111. 2004. [7] Subbaiah Venkata, Y.P., Pratap, P., Reddy Ramkrishna, K.T., Miles, R.W. and Yi, J., Studies on ZnS0.5Se0.5 buffer based thin film solar cells, Thin solid films, 516, 7060–7064, 2008. [8] Bagade, C.S., Mali, S.S., Ghanwat, V.B., Khot, K.V., Patil, P.B., Kharade, S.D., Mane, R.M., Desai, N.D., Hong, C.K. Patil, P.S. and Bhosale, P.N., A facile and low cost strategy to synthesizeCd1–xZnxSe thin films for photoelectron chemical performance: effect of zinc content, RSC Adv., 5, 55658, 2015. [9] Khot, K.V., Mali, S.S., Pawar, N.B., Kharade, R.R., Mane, R.M., Kondalkar, V.V., Patil, P.B., Patil, P.S., Hong, C.K., Kim, J.H., Heo J. and Bhosale, P.N., Development of nanocoral-like Cd(SSe) thin films using an arrested precipitation technique and their application, New J. Chem., 38, 5964, 2014.

Synthesis of Reduced Graphene-TiO2 Photocatalyst for Hydrogen Evolution Neha Singh, Rahul Kumar1, Ratan Kumar Dey and Gajendra Prasad Singh1 Centre for Applied Chemistry, Central University of Jharkhand, Ranchi, Jharkhand 1 Centre for Nanotechnology, Central University of Jharkhand, Ranchi, Jharkhand E-mail: [email protected]

ABSTRACT The reduced graphene oxide-TiO2nanocomposites was synthesized by hydrothermal decomposition at 150°C for 5h. The obtained nanocomposites were analyzed by XRD, SEM, UV-visible and FTIR spectroscopy. The graphite flakes showed total four distinct peaks with most intense peak at 2θ~26.05º of (002) plane whereas the same peak in graphene oxide is observed at 2θ~10.15º. The graphene oxide sheets in micron size is formed and TiO2 particles are well dispersed on the active site of sheets The graphene oxide showed absorbance peak at 232 nmand a broad shoulder peak at 300 nm. The presence of different type of oxygen functionalities peaks in FTIR spectra confirms the formation of graphene oxide. The TiO2 modified by 0.5 wt% of GO shows considerable enhancement in the H2 production, i.e. 1.1 mmol in comparison to 0.52 mmol for pure TiO2.

INTRODUCTION Owing to persistent demand of development ofalternative source of green route for the production of energy, the photo-catalytic hydrogen (H2) production from water splitting has been considered as a new breakthrough area [1, 2]. The photo-catalytic H2 production in presence of TiO2 photo-catalysts electrode was first time tested by Fuijisma and Honda [2]. Later on, several types of materials such as semiconductor, metal-semiconductor composites, polymer-semiconductor composites and semiconductor-semiconductor composites were used for photo-catalytic hydrogen (H2) production by various research groups [3,4]. The subsequent development of new materials further leads enhancement in H2 production from water. But, most of the materials activity are limited in ultraviolet region. Hence, in order to utilize the full solar spectrum mainly in visible region requires materials which have capacity to show absorbance or activity in visible region. In this regard, graphene based hybrid nanocomposites have been considered as another high quality photo-catalyst. Here, we report the synthesis of reduced graphene oxide (RGO) based TiO2hybrid nanocompositesphoto-catalyst for photo-catalytic H2 generation. The developed hybrid composites were characterized by using X-ray diffractogram (XRD), Fourier transform Infrared (FTIR) spectroscopy, UV-Visible spectroscopy, and Transmission electron microscopy (TEM). EXPERIMENTAL PROCEDURE The reduced graphene oxide (RGO) based TiO2 hybrid nanocomposites photo-catalyst was synthesized in two different steps. Firstly, the graphene oxides (GOs) were synthesized from commercial graphite flakes by using a well-known modified Hummers method [1, 5]. The obtained V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 219–222 (2015)

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powder was graphite oxide and exfoliation of oxide is known as graphene oxides (GOs). Secondly, the TiO2 powder was mixed with selective amount (0, 0.2, 0.5 and 1 wt %) of GOs exfoliated in waterethanol solution. The mixture was transferred into Teflon lined autoclave of 100 ml for 5 h for 150°C. After hydrothermal treatment, sample was recovered and washed thoroughly. The recovered powder sample is known as reduced graphene oxide-TiO2 (RGT) nanocompositephotocatalysts. The graphite flakes and graphene oxide powder were characterized by X-ray diffraction using a Bruker D8 advance X-ray diffractometer in the 10–100˚ range. SEM image was taken from Philips. UV-visible spectra of aqueous graphene oxide solution were obtained at room temperature in the range of 200–800 nm using a Perkin Elmer UV-visible spectrophotometer. FTIR spectra of graphene and graphene oxide mixed with KBr powder were recorded via a Perkin Elmer spectrophotometer.

RESULTS AND DISCUSSION The XRD spectra of the graphite flakes and graphene oxide are shown in Figure 1. The graphite flakes showed total four distinct peaks such as (002), (100), (004) and (105). Among these peaks, the most intense peak observed at 2θ~26.05º corresponds to the (002) plane of well-ordered carbon atoms in graphite. In contrast to graphite flakes, the same peak of (002) plane in graphene oxide is observed at 2θ~10.15º as shown in Figure 1.

Fig. 1: X-ray Diffraction Patterns of Graphite Flakes and Graphene Oxide Powder

The nearly featureless region at 2θ~26.05º on the spectrum of graphene oxides relative to that of graphite indicates that almost all graphite has been oxidized. These XRD spectra indicate that the interplanar spacing (d) of ~0.341 nm for graphite flakes has been shifted to 0.879 nm for graphene oxide. This increment in the interplanar spacing in graphene oxides is due to the expansion of the layer planes caused by the accommodation of various oxygen species. Furthermore, the SEM images of GO and RGO-TiO2 nanocomposites are shown in Figure 2. The GO sheets consists of micron size and the TiO2 particles of about 50 nm size are well anchored on GOs sheets active sites. The evolution of the Ultraviolet-visible (UV-vis) absorption spectra of graphene oxide (GO) suspensions is shown in Figure 3. The as-prepared GO samples (day 0) showed

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typical characteristics of a main absorbance peak at 232 nm, attributed to π–π* transitions of C = C in amorphous carbon systems. In addition, a broad shoulder at 300 nm is attributed due to n– π * transitions of C = O.

Fig. 2: SEM Images of (a) Graphene Oxide and (b) RGO-TiO2 Nanocomposites

Fig. 3: UV-Visible Spectrum of Graphene Oxide Dispersed in Water

The oxidation of the graphite flakes was further confirmed by the FTIR spectra (Figure is not given here). The graphite flakes spectrum was not showing any significant peak whereas the FTIR spectrum GOs showed the presence of different type of oxygen functionalities. The peaks are observed at 3400 cm–1 (O-H stretching vibrations), at 1720 cm–1 (stretching vibrations from C=O), at 1600 cm–1 (skeletal vibrations from unoxidized graphitic domains), at 1220 cm–1 (C-OH stretching vibrations), and at 1060 cm–1 (C-O stretching vibrations). Therefore, it can be concluded that the sample has strong hydrophilicity. Finally, the absorption peaks at 1385 cm−1 and 1110 cm−1 are correspond to the stretching vibration of C-O of carboxylic acid and C-OH of alcohol, respectively. The presence of these oxygen containing groups reveals that the graphite has been oxidized. The photo-catalytic hydrogen (H2) evolution activities on RGO and its composite samples were evaluated in UV-Visible region. In absence of photocatalyst, H2 evolution was almost negligible whereas in the

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presence of photocatalyst in solution, a significant H2 evolution was detected. It indicates the photocatalytic activity was happening due to presence of the photocatalyst. The TiO2 modified by 0.5 wt% of GO shows considerable enhancement in the H2 production rate, 1.1 mmol in comparison to 0.52 mmol for pure TiO2.

CONCLUSIONS The reduced graphene oxide-TiO2nanocomposites was synthesized by employing two processes, i.e. soft chemical and hydrothermal decomposition. The GOs showed the intense peak at 2θ~10.15º of (002) plane. The hydrothermal decomposition facilitates the well dispersion of the TiO2 nanoparticles on the active sites of GOs. In GOs dispersed in water, the absorption peaks are observed at 232 nm along with broad shoulder peak at 300 nm. The formation of GOs was further confirmed by the presence OH, C=O, and C-OH peaks at 3400, 1720 and 1600 cm–1. The TiO2 modified by 0.5 wt% of GO shows considerable enhancement in the H2 production, i.e. 1.1 mmol in comparison to 0.52 mmol for pure TiO2. REFERENCES [1] Singh, G.P., Singh, Shrestha, K.M., Nepal, A., Klabunde, K.J. and Sorensen, C.M., Graphene supported plasmonicphotocatalyst for hydrogen evolution in photocatalytic water splitting, Nanotechnology, 25, 265701–6, 2014. [2] Fujishima, A. and Honda, K., Electrochemical photolysis of water at a semiconductor electrode, Nature, 238, 37–38, 1972. [3] Kudo, A. and Yugo, M., Heterogeneous photocatalyst materials for water splitting, Chem. Soc. Rev., 38, 253–278, 2009. [4] Tu, W., Yong, Z. and Zou, Z., Versatile graphene-promoting photocatalytic performance of semiconductors: Basic principles, synthesis, solar energy conversion, and environmental applications, Adv. Funct. Mater., 23, 4996–5008, 2013. [5] Hummers, W.S. and Offeman, R.E., Preparation of graphitic oxide, J. Am. Chem. Soc., 80, 1339, 1958.

Analysing the Electrical Properties of Electron Beam Evaporated CdSe Thin Films for PEC Solar Cells K.S. Rajni Amrita School of Engineering, Coimbatore, Tamil Nadu

INTRODUCTION The severe crunch for the energy resources for solar absorption demands the development of photovoltaic devices and solar cells in which the energy from solar radiation is directly converted into useful electrical energy. CdSe have intermediate energy band gap, reasonable conversion efficiency, stability and low cost [1]. The absorption edge is approximately at 730 nm (response to the major part of the visible spectrum) and has a direct forbidden gap of energy of 1.74 eV. CdSe often has n-type conductivity in the bulk as well as in the thin film form [2] and the excess of cadmium and selenium vacancies play an important role in the determination of conduction process in CdSe thin films. EXPERIMENTAL In the present work CdSe thin films are prepared at different substrate temperature (RT, 100 and 200°C) by electron beam evaporation technique at a pressure of 10–6 Torr on a well cleaned glass substrate. The thickness of the prepared film is 270 nm.X-ray diffraction studies were carried out to analyze the structure and Linear four probe technique is used to measure the resistivity. An indigenously fabricated Van der Pauw set-up is employed for measuring the Hall coefficient. RESULTS AND DISCUSSIONS Structural Analysis-Effect of Substrate Temperature Figure 1(a), (b) & (c) shows the XRD patterns of CdSe thin films deposited at different substrate temperatures of RT, 100 and 200°C respectively. The difractogram shows the polycrystalline nature with peaks correspond to the hexagonal phase of CdSe film. This is supported by the fact that the bulk CdSe has a highly stable hexagonal (wurtzite) structure at temperatures ranging from room temperature to its melting point (~1240°C) [3]. In the present study the prepared CdSe thin films showed only hexagonal structure and all the films have thickness of about 270 nm. The XRD spectra show that at room temperature (RT), (002) peak along with other peaks like (101), (110) and (103) are identified. When the substrate temperature is increased, the films became highly orientated along (002) plane and the other peaks are greatly suppressed. These results have been observed similar to the CdSe films deposited by molecular beam epitaxy technique [4]. The microstructral properties of CdSe films with different substrate temperatures are summarized in Table 1. The increase in grain size shows the improvement in crystallinity that decreases the grain boundary discontinuities. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 223–226 (2015)

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Table 1: Microstructural Parameters of CdSe Films Deposited at various Temperatures Tempera ture (°C)

Grain Size D (nm)

RT 100 200

17 22 35

Dislocation Density δ (× 1014) Lines/m2 19.12 21.49 17.24

Lattice Parameters Strain ε × 10–3 1.96 1.88 1.70

No. of Crystallites n × 1015/unit area 19.89 17.54 9.67

a (nm) 0.433 0.436 0.435

c (nm) 0.697 0.699 0.698

Fig. 1: XRD Pattern of CdSe thin Films Deposited at Different Substrate Temperatutes, (a) Rt, (b) 100C, (c) 200C

Variation of Resistivity, Mobility and Carrier Concentration with Substrate Temperature From the observation of the direction of current flow and using the hot probe method all the EB evaporation CdSe films, irrespective of their deposition temperature are found to be n-type.The electrical resistivity values were high in the range of 105–107 ohm cm and agree well with the published values of about 1–3 × 107 ohm cm [5]. Further, it is obvious that the resistance of nanocrystalline thin films and materials is always higher compared to the corresponding larger grained polycrystalline films [6]. The values of resistivity (ρ) are 4.12 × 107, 5.98 × 106 and 2.45 × 105 ohm cm for the CdSe films deposited on glass substrates at RT, 100 and 200 °C respectively are shown in Figure 2 Thickness of all these films was kept nearly constant at about 270 nm. The high resistivity value for CdSe films at room temperature is attributed to the presence of fine grains (17 nm). The lower value of resistivity measures for the CdSe films deposited at 200°C is due to the increase in grain size to 35 nm. The characteristic behavior of the Hall mobility (μH) with substrate temperature for CdSe films of about 270 nm thickness is shown in Figure 3. The calculated carrier concentration values are nearly constant about 1.8–2.8 × 1017 cm–3 and it are shown in Figure 4.

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Fig. 2: Resistivity Variation with Different Substrate Temperatures for the CdSe Films

Fig. 3 & 4: Variation of Hall Mobility and Carrier Concentration Variations with Different Substrate Temperatures for the CdSe Films

Berger et al. [7] had reported very low activation energies of about 0.005–0.047 eV. Such results are highly related to the existence of a well-defined potential barrier between inter-crystalline grains probably which may be over-come by thermal activation and the carrier concentration and Hall mobility in the CdSe films [7,8]. Further, the activation energy ΔE corresponds to the mean energy of charge carriers with respect to the Fermi energy, when the carriers move along at the bottom or top of the well defined bands, conduction band and valance band respectively [9]. This is attributed to the electron isolation which implies a potential barrier between them, that arises due to the presence of a surface insulating thin film or insulating selenium aggregates in the grain boundaries leading to surface or grain potential barriers [10]. The activation energy is found to be0.61 eV and it is found to be in good agreement with the reported value [11].It is to be noted that electron trapping level located at 0.60 eV from the conduction band was due to Se (selenium) vacancies [12]. This may be also taken in our case because EB evaporated films are always n-type and at the same time the resistivity values are high. n-type may be due to Se-vacancies or Cd-excess. But, in the present study, though Cd-excess is observed, selenium vacancies act as electron acceptors.

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Flat Band Potential Study by Mott-Schottky Plot For an electrochemical junction, formed with polysulphide solution in contact with CdSe films deposited at 100°C on glass substrate, which makes an ideal system, a plot of 1/C2 versus the electrode potential known as the M-S plot, gives a straight line as seen in Figure 6. The Vfb value is found to be –0.69 V (SCE).

Fig. 5: Mott-Schottky Plot for the CdSe Film

CONCLUSION In the present work, CdSe thin films are prepared by electron beam evaporation technique at different substrate temperatures (Ts) (RT, 100 and 200°C (t = 270 nm)). The grain size of the prepared thin films ranges from 17–21 nm and the film s show n-type conductivity. The electrical resistivity is found to be decreases with increase with the grain size. The characteristic behavior of the hall mobility and hence the carrier concentration values are nearly constant about 1.8–2.8 × 1017 cm–3. The activation energy values were found to vary in the range of 0.308–0.429eV in the higher temperature region and 0.007–0.019 eV in the lower temperature region. The flat band potential for the electrochemical junction formed by the prepared thin film with the polysulphide solution is found to be –0.69 V. REFERENCES [1] Nakayama, N., Arita, T., Aramoto, T., Nishio, T., Higuchi, H., Omura, K., Hiramatsu, K., Ueno, N., Murozono, M. and Takakura, H., Sol. Ener. Mater. Sol. Cells, 35 (1994), 271. [2] Oduor, A.O. and Gould, R.D., Thin Solid Films, 270 (1995), 387. [3] Fitzpatrick, B.J., in: T.C. McGill, C.M.S. Torres, W. Gebhardt (Eds.), Growth and Optics Properties of Wide Gap II-VI Low-Dimensional Semiconductor, Plenum Press, New York, (1989) 67. [4] Hyugaji, M. and Miura, T., Jpn. J. Appl. Phys., 24 (1985), 950. [5] Pramanik, P. and Bhattacharya, R.N., J. Electrochem. Soc., 127 (1980), 2087. [6] Suryanarayana, C., Bull. Mater. Sci., 14 (1994), 307. [7] Berger, H., Janiche, G. and Grachovskey, N., Phys. Stat. Sol., 33 (1969), 417. [8] Mahmoud, S.A., Ashour, A. and Badawi, E.A., Applied Surface Science, 253 (2006), 2969. [9] Brodie, D.E. and Combe, J. La, Can. J. Phys. 45 (1967), 1353. [10] Kal, S.S. and Lokhande, C.D., Mater. Chem. Phys., 62 (2001), 103. [11] Velumani, S., Narayanadas, Sa.K., Mangalraj, D., Sebastian, P.J. and Mathew, Xaview, Solar Energ. Mater. Sol. Cells, 81 (2004), 323. [12] Balasundaram, N., Mangalaraj, D., Narayanadass, Sa.K. and Balasubramanian, C., Phys.Sta. Solodi, (a) 130 (1992), 41.

Scrutiny of Nano Technology Applications for Diesel Engine Performance Enhancement and Emission Control N. Tiruvenkadam, P.R. Thyla1, M. Senthil Kumar3, P.R. Senthil Murugan, D. Sridhar and T. Vijay Ananth Department of Mechatronics Engineering, K.S. Rangasamy College of Technology, Tiruchengode, Tamil Nadu 1 Department of Mechanical Engineering, P.S.G. College of Technology, Coimbatore, Tamil Nadu 2 Department of Production Engineering, P.S.G. College of Technology, Coimbatore, Tamil Nadu

ABSTRACT Nano technology advancement is one of the gifts for automobile sector in particular diesel engine applications. The unavoidable equipment on diesel engine used in car, busses, trucks and heavy vehicles for human, goods transportation and stationary engines like a generator, civil construction, agricultural applications etc. The various losses like cooling loss, friction loss, heat transfer loss, transmission losses and unburned fuel loss were commonly ensued in diesel engines. At last, the maximum 30% of useful output energy was retrieved for the supply of 100% input chemical (diesel) energy. So it is a duty of scientists, researchers and an engineer’s promote the useful technology to enhance the performance, reduce the emissions from diesel engines. This paper scrutinized that one of the current and future conquer technology of Nano size particles, coatings, composites have been taken place in all the essential components of diesel engines like nanofuel, Nano cooling system, Nano lubricant system, engine internal, external parts coatings and Nano composite were clearly discussed. From this scrutinized paper, it was clearly shown that the Nano technology stretches a potential way to save the energy in diesel engine and gives a green environment.

INTRODUCTION Diesel is essential for transport and heavy duty engines. It contributes to the prosperity of the worldwide economy since it is widely used due to high combustion efficiency, reliability, and cost effectiveness. However, pollutant emission is a main drawback. They can cause serious health problems, especially respiratory and cardiovascular problems. Increasing worldwide concern about combustion related pollutants, such as particulate matter (PM), oxides of nitrogen (NOx), carbon monoxide (CO), total hydrocarbons (THC), acid rain, and photochemical smog and the depletion of the ozone layer have led several countries to regulate emissions and give directives for implementation and compliance.The major developments in nanotechnology took place across the world over the last few years. Nanotechnology is a science of controlling individual atoms and moleculeswhich has great feature and is considered to be the manufacturing technology of 21st century. This paper reveals that by using Nano particles, in engine cooling system, as catalysts, in fuel and also in lubricating oil to reduce engine emission. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 227–232 (2015)

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NANOTECHNOLOGY APPLICATION IN AUTOMOBILES This section presents in more detail about the nanotechnology applications in the automobile emission controls. Nano Materials for Engine Emission Control Examples of technological strategies for Nano technology application of automobile

Catalyst

Lubricating Oil

Cooling System

Fuel

Nanoparticles Nanoparticle research is currently an area of intense scientific research, due to a wide variety of potential applications in biomedical, optical, and electronic fields. Nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic or molecular structures. Nanoparticles are particles that have one dimension that is 100 Nano meters or less in size. The properties of many conventional materials change when formedFrom nanoparticles. This is typically because nanoparticles have a greater surface area per weight than larger particles; this causes them to be more reactive to certain other molecules. Nanoparticles are used, or being evaluated for use, in many fields. ENGINE EMISSION CONTROL USING COOLING SYSTEM Cooling system plays important roles to control the temperature of car engine. One of the important elements in the car cooling system is cooling fluid. The usage of wrong cooling fluid can give negative impact to the car’s engine and shorten engine life. An efficient cooling system can prevent engine from overheating and assist the vehicle running at its optimal performance. With the development of new technology in the field of ‘Nano materials’ and ‘Nano fluid’, it seems very promising to use this technology as a coolant in the internal combustion engine. In this study, a Nano fluid (AL2O3-Water/Ethylene Glycol (EG)) is used as an engine coolant along with an optimized heat exchanger to reduce the warm up timing. The effect of nano fluid concentration is considered here by using their corresponding governing equations, such as momentum and energy[1, 2, 3, 4, and 5]. Emission Control by Using Nano Fluid Additive in Diesel An experimental investigation is carried out to establish the performance and emission characteristics of a compression ignition engine while using cerium oxide nanoparticles as additive in neat diesel and diesel-biodiesel-ethanol blends. In the first phase of the experiments, stability of neat diesel and diesel-biodiesel-ethanol fuel blends with the addition of cerium oxide nanoparticles are analyzed [6, 7, 8, and 9]. One of the methods to vary the physicochemical properties and combustion characteristics of a hydrocarbon fuel is the use of additives, which are found to be especially effective in nanoparticle form, due to the enhancement of the surface area to volume ratio. ASTM standard tests for the fuel property measurements and engine performance tests were reported in this paper for bio diesel modified by the addition of cerium oxide nanoparticles. Experiments were carried out at different dosing levels of the nanoparticle additives, to investigate the influences on the physicochemical properties, engine performance, and emissions [10, 11, 12, 13, and 14].

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The cerium oxide acts as an oxygen donating catalyst and provides oxygen for the oxidation of CO or absorbs oxygen for the reduction of NOx. The activation energy of cerium oxide acts to burn off carbon deposits within the engine cylinder at the wall temperature and prevents the deposition of non-polar compounds on the cylinder wall results reduction in HC emissions [15, 16, 17, 18, and 19]. The Nano particles are made by applying a plasma arc to aluminiumNano powder submerged in water. The average diameter of the aluminium nanoparticles is about 40–60 nm and they are covered with thin layers of aluminium oxide due to the higher oxidation activity of pure aluminium. This provides a large contact surface area with water and high activity for the decomposition of hydrogen from water during the combustion process. During combustion the alumina serves as a catalyst and the coated aluminium nanoparticles are denuded and decompose the water to yield the hydrogen. After combustion, total combustion heat increases while the concentration of smoke and nitrous oxide in the exhaust emission from diesel engine are decreased [20, 21, 22, and 23].

Emission Control by Using Nano Catalytic Converter A study on nano-particle reveals that the ratio of surface area of nano-particle to the volume of the nano-particle is inversely proportional to the radius of the nano-particle. So, on decreasing the radius, this ratio is increased, leading to an increased rate of reaction and the concentration of the pollutants is decreased. To achieve this objective, an innovative design of catalytic converter for automobiles is proposed using nano-particle as a catalyst. The proposed method is very effective in the prevention of environmental pollution contributed from automobiles. It involves the use of copper nano-particle which is cheaper than the platinum, palladium and rhodium nano-particles used in automobiles [24, 25, 26, 27, 28, and 29]. Nano materials like nano rhodium and nano palladium were obtained by using chemical vapor deposition (CVD) technique. The obtained nano powder was deposited in the honeycomb structure by using the spin coating method in the catalytic converter. Further the characterization of nano palladium and nano rhodium powder is made through Scanning Electron Microscope (SEM), X-ray diffraction, transmission electron microscope. By using the Nano catalytic converter the pollution is reduced [30, 31, 32, 33, 34, 35, 36, and 37]. Emission Control by Using Nano Fluid Additive in Lubricant Oil The synthesis and study of oil-soluble metal carbonate colloids are of interest in the area of lubricant additives. These surfactant-stabilized nanoparticles are important components in marine and automotive engine oils. Recently introduced, environmentally driven legislation has focused lowering of gaseous emissions by placing limits on the levels of phosphorous sulfur and ash allowed in engine oil systems. These chemical limits, coupled with improved engine performance and extended oil drain intervals, have led to renewed interest in the production of stable, efficient nanodetergent systems. To date, this has resulted in the modification of existing surfactant structures and development of new generations of surfactants [38, 39, 40, 41, 42, 43, 44, and 45]. CONCLUSION Many scientific studies have linked breathing in a PM to a series of significant health problems, including aggravated asthma and an increase in respiratory symptoms. PM emissions can be reduced in a number of ways, including more stringent emissions standards for internal combustion engines and fuels. The introduction of nanotechnology inthe engine has significantly improved the performance, fuel economy and exhaust emissions of diesel engines.

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The major developments in nanotechnology took place across the world over the last few years. By using Nano particles, in the engine cooling system, catalyst, fuel and also in lubricating oil to reduce engine emission the implementation of this nanotechnology will create an environment which stabilizes the emission of harmful gases thereby indirectly counteracts few main environmental issues to a major extent.

REFERENCES [1] Sharma, Vikas; Kumar, R. Nirmal; Thamilarasan, K.; Bhaskar, G. Vijay and Devra, Bhavesh “Heat Reduction FromIc Engine By Using Al2o3Nanofluid In Engine Cooling System”, American Journal of Engineering Research, Vol. 03, Issue 04, pp. 173–177, 2014. [2] Wong, Kaufui V. and Leon, Omar De, “Applications of Nano fluids: Current and Future”, Advances in mechanical engineering, Vol. 2010, Article ID 519659. [3] Franco, Antonio; Hansen, Steffen Foss; Olsen, Stig Irving and Butti, Luciano, “Limits and prospects of the ‘‘incremental approach’’ and the European legislation on the management of risks related to nanomaterials”, Regulatory toxicology and pharmacology, November 2006. [4] Arici1, M. and Karabay1, H., “The role of nanoparticles in enhancement of heat transfer”, International research and practice conference Nanotechnology and Nanomaterials, August 29 –September 1, 2013, Bukovel, Ukraine. [5] Venkatesan, S.P., Mathew, Joshua and Melel, Jithin Alex, “Improving the heat removal rate using nano particle mixed coolant in radiator”, Journal of Chemical and Pharmaceutical Sciences, 2015. [6] Selvan, V. Arul Mozhi; Anand, R.B. and Udayakumar, M., “Effect of cerium oxide nanopartical addition in diesel and diesel-biodiesel-ethanol blends on the performance and emission characteristics of a ci engine”, ARPN Journal of Engineering and Applied Sciences Vol. 4, No. 7, 2009. [7] Sajith, V., Sobhan, C.B. and Peterson, G.P., “Experimental Investigations on the Effects of Cerium Oxide Nanoparticle Fuel Additives on Biodiesel”, Advances in Mechanical Engineering, Vol. 2010, Article ID 581407. [8] Myung, C.L. and Park, S., “Exhaust nanoparticle emissions from internal combustion engines: A review”, International Journal of Automotive Technology, Vol. 13, No. 1, pp. 9−22 (2012). [9] Brijesh, P. and Sretha, S., “Exhaust emissions and its control methods in compression ignition engine: A review”, International Journal of Automotive Technology, Vol. 14, No. 2, pp. 195−206 (2013). [10] Lee, J., Lee, Y., Huh, K.Y., Kwon, H. and Park, J.I., “Quasi dimensional analysis of combustion emissions and knocking in a homogeneous GDI engine”, International Journal of Automotive Technology, Vol. 16, No. 5, pp. 877−883 (2015). [11] Uhrner, Ulrich and Zallinger, Michael, “Volatile Nanoparticle Formation and Growth within a Diluting Diesel Car Exhaust”, Journal of the air and waste management association, DOI:10.3155/10473289.61.4.399. [12] Matsuda, Masami and Hunt, Geosrey, “Nanotechnology and public health”, Japanese journal of public health, December 2005, Vol. 52, No. 11, p. 923927. [13] Uibel, Stefanie; Takemura, Masaya; Mueller, Daniel; Quarcoo, David; Klingelhoefer, Doris and Groneberg, David A., “Nanoparticles and cars – analysis of potential sources”, Journal of Occupational Medicine and Toxicology, 2012. [14] Casillas, Perla E. García, “Infrared Spectroscopy of Functionalized Magnetic Nanoparticles”. [15] Ranaware, A.A. and Satpute, S.T., “Correlation between Effects of Cerium Oxide Nanoparticles and Ferrofluid on the Performance and Emission Characteristics of a C.I. Engine”, IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE ISSN: 2278–1684, pp: 55–59. [16] Kao, Mu-Jung; Ting, Chen-Ching; Lin, Bai-Fu and Tsung, Tsing-Tshih, “Aqueous Aluminum Nanofluid Combustion in Diesel Fuel”, Journal of Testing and Evaluation, Vol. 36, No. 2 Paper ID JTE100579.

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[34] Stone, Peter, Ishii, Masaru and Bowke, Michael, “NOx storage in model Pt/Ba NSR catalysts: fabrication and reactivity of BaO nanoparticles on Pt. (111)”, Surface science, July 2003. [35] Smallwood, Greg; Thomson, Kevin; Snelling, David and Greenhalgh, Doug, “Mass Concentration of Non-volatile Nanoparticle Emissions: Comparison of Auto compensating Laser-Induced Incandescence (AC-LII) to Other Techniques”, International Energy Agency 32nd Task Leaders Meeting on Energy Conservation and Emissions Reduction in Combustion Nara, Japan 25 29 July 2010. [36] Senthilraja, S., Karthikeyan, M. and Gangadevi, R., “Nano fluid Applications in Future Automobiles: Comprehensive Review of Existing Data”, Vol. 2, No. 4, 306–310 (2010). [37] Weidenhof, B., Reiser, M., Sto, K. ¨we, Maier, W.F., Kim, M., Azurdia, J., Gulari, E., Seker, E., Barks, A. and Laine, R.M., “High-Throughput Screening of Nanoparticle Catalysts Made by Flame Spray Pyrolysis as Hydrocarbon/NO Oxidation Catalysts”, Journal of the American chemical society (2009). [38] Hudson, L.K., Eastoe, J. and Dowding, P.J., “Nanotechnology in action: Overbased nanodetergents as lubricant oil additives”, Advances in Colloid and Interface Science, 123–126 (2006) 425–431. [39] Bagavathi D\O Krishnan “Investigation of alumina additive in lubricant oil for enhanced engine performance”, Bachelor of Mechanical Engineering Majoring in Automotive Engineering, June 2012. [40] Santhanamuthu, M., Chittibabu, S., Tamizharasan, T. and Mani, T.P., “Evaluation of CI engine performance fuelled by Diesel-Polanga oil blends doped with iron oxide nanoparticles”, International Journal of ChemTech Research, Vol. 6, No. 2, pp. 1299–1308, April–June 2014. [41] Corti, Christopher W.; Holliday, Richard J. and Thompson, David T., “Developing NewIndustrial Applications for Gold: Gold Nanotechnology”, (2002). [42] Yu, Wei and Xie, Huaqing, “A Review on Nanofluids: Preparation, Stability Mechanisms, and Applications”, Journal of Nanomaterials, Vol. 2012, Article ID 435873. [43] Johnson, Timothy V., “Diesel Emission Control in Review”, SAE International, 2008 (SP-2154). [44] Zhmud, Boris and Pasalskiy, Bogdan, “Nanomaterials in Lubricants: An Industrial Perspective on Current Research Lubricants”, Lubricants, 2013, 1, 95–101. [45] Presting, Hartmut and Ko¨nig, Ulf, “Future nanotechnology developments for automotive applications”, Materials Science and Engineering, (2003) 737–741.

Integral Approach to Improve Hybrid Supercapacitors: From Hybrid Electrode Materials Based on Reduced Graphene Oxide-Polyoxometalates (rGO-POMs) to Hybrid Electrolytes Containing Quinones Deepak P. Dubal and Pedro Gomez-Romero Catalan Institute of Nanoscience and Nanotechnology, CIN2, ICN2 (CSIC-CERCA), Campus UAB, E-08193 Bellaterra, Barcelona, Spain E-mail: [email protected], [email protected]

Energy storage devices have been widely researched in order to meet the increasing demand of high energy, high power and cost effective storage systems.[1–3] Thus, various electrochemical energy storage devices have been proposed with batteries and supercapacitors as complementary technologies.[2] Among them, batteries take an advantage of bulk charge storage mechanism hence exhibit high energy density but they suffer from low power and cycling stability. In great contrast, supercapacitors store charge through surface adsorption (non-faradaic) and surface redox reaction (pseudo-capacitor) hence possess high power density and excellent cycling stability, sacrificing energy storage ability.[4] The emerging new concept of hybrid electrodes combines the high energy density characteristic of batteries with the high power and long-term stability of supercapacitors.[5–7] Polyoxometalates (POMs) are redox-active molecular clusters combining oxygen and early transition metals at their highest oxidation states. POMs are molecular oxides which contain tens to hundreds of metal atoms that reach nuclearities as high as 368 metal atoms in one single cluster molecule forming nanoparticles.[8, 9] They are well suited to achieve high capacity for energy storage applications due to fast and reversible multi-electron redox reactions. Moreover, due to the high solubility of these POMs in aqueous solutions, most of them were anchored onto CNTs,[10, 11] or AC,[12] to prevent the dissolution of the POMs into the aqueous electrolytes and also to increase the electrical conductivity. In this context, we carefully prepared three-dimensional (3D) hierarchical open porous reduced graphene oxide (rGO) through modified Hummer’s method. Subsequently, polyoxometalate molecular clusters (specifically phospomolybdate (PMo12) and phosphotungstate (PW12) in their acidic form) were homogeneously and efficiently anchored onto the surface of rGO nanosheets (Figure 1). In order to demonstrate the electrochemical performance, we fabricated the rGO-POMs hybrid symmetrical supercapacitors with H2SO4/PVA gel electrolyte. 3D hierarchical porous architecture and ultrathin graphene nanosheets decorated with tiny yet numerous PW12 clusters endow rGO-POMs excellent volumetric capacitance of over 5.09–6.12 F/cm3 which is much larger than those values for rGO (1.43 F/cm3). Moreover, thanks to the combination of faradaic and EDLCs at both ends, the rGO-POMs V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 233–236 (2015)

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based all-solid statee supercapacittor could realiize a broad vooltage of 1.6 V, amazinglyy comparable to t metric system ms, and attain a remarkable energy densitty of 1.04–1.11 mWh/cm3. In I addition annd asymm for thhe first time, we w have extennded our workk dedicating earnest e effortss to investigatte the effect of o additioon of redox-aactive species (hydroquinonne) in solid-sttate gel electrrolyte to furthher improve thhe perforrmance of rGO O-POMs basedd symmetric capacitors. c

Fig. 1: Schemaatic Illustration of Steps Involvved in the Synthhesis of Reduceed Graphene Oxxide (rGO) and Phospho otungstate (PMo12) Hybrid Maaterial (rGO-PW W12) with Simple Chemical Tecchnique

Fig. 2: (a, b) SE F EM images of rGO r and rGO-P PW12 hybrid matterials, respectivvely, (c, d) STE EM images of rGO and rGO-PW r rid samples, resspectively. (e) HR-TEM H imagee of rGO-PW12 sample, 12 hybr (f) EDS mapping of o rGO-PW12 hyybrid sample.

A series of morphological m characterizattions have beeen carried out o to confirm m the efficiennt anchooring of PW12 onto the surfaace of 3D open porous rGO O nanosheets. Figure F 2 (a, b)) presents SEM M imagees of rGO and rGO-PW12 hyybrid materialls, respectivelyy. It is revealeed that rGO exxhibits 3D opeen porouus architecture composed off ultrathin nanosheets and ellectronically conductive c fraamework whicch is higghly beneficiaal to enhancee the electronn transport annd good ionicc conductivityy. It is furtheer interesting to note that rGO preeserves its 3D D open porouss structure eveen after heavyy deposition of o

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PW12 metal oxide clusters. In order to get more insights about the distribution of PW12 on rGO nanosheets, STEM analysis has been carried out and displayed in Figure 2 (c, d). It is unambiguously seen (Figure 2 c), that the surface of rGO nanosheets is blank and free from tiny spots while in great contrast, the surface of rGO-PW12 hybrid is abundantly and evenly decorated with PW12 tiny nanoclusters. It is further interesting to note that, the PW12 nanoparticles are evenly anchored on rGO surface without any agglomeration. Figure 2 (e) shows HR-TEM image of rGO-PW12 sample in which black tiny nanoparticles of PW12 are clearly observed. EDS analysis of rGO-PW12 hybrid sample has been carried out and shown in Figure 2 (f) which clearly confirms that the PW12 nanoparticulate metal oxide cluster is homogeneously and efficiently anchored onto the rGO nanosheets. Figure 3 summarizes the effect of PW12 attachment on the electrochemical performances of rGO with all-solid state symmetric configuration. Figure 3 (a) shows the CV curves of rGO and rGO-PW12 symmetric cells at constant scan rate of 20 mV/s. It is worth noting thatthere is a substantial increase in the current density for rGO-PW12 hybrid cell along with an extension of 0.3 V compared to rGO cell. Furthermore, as seen in Figure 3 (b), the discharging time for rGO-PW12 symmetric cell is substantially higher than that for rGO based symmetric cell with extended operational voltage window (1.6 V), indicating that the cell has a significantly larger specific capacitance. This significant improvement in overall electrochemical performances of cell may be attributed to the synergetic effect from rGO (EDLC) and PW12 (faradaic). Further, all electrochemical parameters have been calculated by standard equations. Figure 3(c) shows the variation of volumetric capacitance of rGO and rGOPW12 based symmetric cells as a function of scan rates. The rGO-PW12 symmetric cell provides a volumetric capacitance of 5.04 F/cm3 (443 mF/cm2) and 1.61 F/cm3 (142 mF/cm2) at scan rate of 5 and 100 mV/s, respectively. This represents a much higher capacitance than the rGO symmetric cell (1.43 F/cm3 (125 mF/cm2) and 0.51 F/cm3 (44 mF/cm2) at scan rate of 5 and 100 mV/s, respectively). This enormous increase of specific capacitance is due to the faradaic contribution of PW12 in the nanohybrid.

Fig. 3: (a) CV curves and (b) CD curves of rGO and rGO-PW12 symmetric cells at scan rate of 20 mV/s and current density of 1.27 mA/cm2, respectively, (c) Variation of volumetric capacitance of rGO and rGO-PW12 based symmetric cells as a function of scan rates, (d) the volumetric power and energy density values of rGO and rGO-PW12 symmetric cells.

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Inspired from the work above, we are presenting one more successful example to further improve the performance of rGO-PW12 symmetric cell with redox-active species (hydroquinone) doped PVA/H2SO4 gel-electrolyte. Hydroquinone (HQ) is a highly active redox species and undergoes oxidation to release 2 electrons and form para-benzoquinone and vice versa. The hybrid gelelectrolyte was prepared by doping conventional PVA/H2SO4 polymer gel-electrolyte solution with different concentrations of Hydroquinone (0.1, 0.2 and 0.3 M). Further, this hybrid electrolyte gel was applied to rGO-PW12 hybrid supercapacitor which significantly enhances the overall performance of the device. Impressively, 2-fold increase in the device performance with redox-active electrolyte has been achieved. These encouraging findings have proved the potential of the rGO-PW12 hybrid material with hybrid electrolyte as a promising device with high energy density, high power density, and long cycle lifetime for energy storage systems.

REFERENCES [1] Simon, P., Gogotsi, Y., Nat. Mater, 2008, 7, 845–854. [2] Dubal, D.P., Ayyad, O. Ruiz, V. and Gomez-Romero, P., Chem. Soc. Rev. 2015, 44, 1777–1790. [3] Pech, D., Brunet, M., Durou, H., Huang, P., Mochalin, V., Gogotsi, Y., Taberna, P.L. and Simon, P. Nat. Nanotechnol. 2010, 5, 651–654. [4] Simon, P., Gogotsi, Y. and Dunn, B., Science, 2014, 343, 1210–1211. [5] Yu, G., Xie, X., Pan, L., Bao, Z. and Cui, Y., Nano Energy, 2013, 2, 213–234. [6] Suarez-Guevara, J., Ruiz, V. and Gomez-Romero, P., J. Mater. Chem. A, 2014, 2, 1014–1021. [7] Dubal, D.P., Gomez-Romero, P., Sankapal, B.R. and Holze, R., Nano Energy, 2015, 11, 377–399. [8] Muller, A., Krickemeyer, E., Meyer, J., Bogge, H., Peters, F., Plass, W., Diemann, E., Dillinger, S., Nonnenbruch, F., Randerath M. and Menke, C., Angew. Chem., Int. Ed., 1995, 34, 2122–2124. [9] Muller, A., Beckmann, E., Bogge, H., Schmidtmann, M. and Dress, A., Angew. Chem., Int. Ed., 2002, 41, 1162–1167. [10] Cuentas-Gallegos, A., Martinez-Rosales, R., Baibarac, M., Gomez-Romero, P. and Rincon, M.E., Electrochem. Commun., 2007, 9, 2088–2092. [11] Akter, T., Hu, K.W. and Lian, K., Electrochim. Acta, 2011, 56, 4966–4971. [12] Ruiz, V., Suarez-Guevara, J. and Gomez-Romero, P., Electrochem. Commun., 2012, 24, 35–38.

Chlamydomonas – A Green Micro Sized Nano Synthesizer: Phyco Solution to Nano Problems Vidhyasri Subramaniyam1,2, Suresh Ramraj Subashchandrabose1,2, Palanisami Thavamani1,2, Mallavarapu Megharaj1,2, Zuliang Chen1,2 and Ravi Naidu1,2 1

Global Centre for Environmental Remediation, Faculty of Science and Information Technology, University of Newcastle, Callaghan NSW 2308, Australia 2 CRC for Contamination Assessment and Remediation of the Environment, Mawson Lakes, Adelaide, 5095, Australia E-mail: [email protected]

Nanotechnology based remediation approaches are one of the promising and upcoming technologies for the clean-up of challenging environmental contaminants like chromium. Iron nanoparticles are most commonly used in the remediation due to its high reducing property as an electron donor, small size and high surface area [1]. Earlier studies reported the efficiency of iron nanoparticles in reducing 98% Cr(VI) by adsorption and reductive precipitation mechanisms [2]. However, these chemically synthesised iron nanoparticles are futile at field due to its instability as a result of agglomeration resulting in low reactivity [3]. Also, synthesis of these nanoparticles involves the use of precursor chemicals, toxic solvents and generation of hazardous by-products which pose further threat to the environment. Previously, few studies have shown the use of stabilising agents such as starch, Polyvinyl alcohol-co-vinyl acetate-co-itaconic acid, guar gum, carboxymethyl cellulose, bentonite, chitosan and calcium alginate beads to improve the efficiency of iron nanoparticles. However, in our study, an attempt was made to synthesise iron nanoparticles using microalgae following environmentally benign procedure which is also high yielding and cost-effective. Functional groups namely carboxyl, hydroxyl, sulphate and phosphate present in algal biomolecules such as polysaccharides, proteins and lipids reduce the bulk size metal to nano-size metal [4]. Also, they cap and protect the synthesized nanoparticle from agglomeration thereby increasing its stability resulting in effective remediation [5]. In our study, it is proved that biomass of microalga, Chlamydomonas sp. MM7 has the capacity to produce encapsulated spherical shaped iron nanoparticles of size ranging from 10–30 nm by acting as a reducing and capping agent which is confirmed using scanning electron microscope and energy dispersive x-ray spectroscopy and it is concurrent with earlier reports [6]. From particle size analysis and scanning electron microscope, it is proved that these nanoparticles are stable for 6 months under refrigerated condition. Moreover, these nanoparticles efficiently remediated Cr(VI) spontaneously by adsorption and reductive precipitation mechanisms similar to previous works [7]. Hence, it is clearly evident from this study that the strain MM7 produced economically viable, environmentally safe, stable nanoparticle and has potential for its application in the remediation of several other contaminants.


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ACKNOWLEDGEMENT The author acknowledges Endeavour Awards – Australian Government and cooperative research centre for contamination assessment and remediation of the environment (CRC CARE) for providing Scholarship, University of South Australia for the research facilities. REFERENCES [1] Zhang, W., Nanoscale iron particles for environmental remediation: An overview. J Nanoparticle Res., 5, 323–332, 2003. [2] Shao-feng, N., Yong, L., Xin-hua, X. and Zhang-hua, L., Removal of hexavalent chromium from aqueous solution by iron nanoparticles. Journal of Zhejiang University-Science B., 6(10), 1022–1027, 2005. [3] Zhao, D., Xu and Y., Reductive immobilization of chromate in water and soil using stabilized iron nanoparticles. Water Res., 41, 2101–2108, 2007. [4] Shankar, S.S., Rai, A., Ahmad, A. and Sastry, M., Rapid synthesis of Au, Ag and bimetallic Au core–Ag shell nanoparticles using neem (Azadirachta indica) leaf broth. J Colloid Interface Sci., 275, 496–502, 2004. [5] Gopinath, V., Ali, M.D., Priyadarshini, S., Priyadharsshini, N.M., Thajuddin, N. and Velusamy, P., Biosynthesis of silver nanoparticles from Tribulus terrestris and its antimicrobial activity: a novel biological approach. Colloid Surf B., 96, 69–74, 2012. [6] Subramaniyam, V., Subashchandrabose, S.R., Thavamani, P., Megharaj, M., Chen, Z. and Naidu, R., Chlorococcum sp. MM11—a novel phyco-nanofactory for the synthesis of iron nanoparticles. Journal of Applied Phycology, 1–9, 2015. [7] Madhavi, V., Prasad, T., Reddy, A.V.B., Reddy, R.B. and Madhavi, G., Application of phytogenic zerovalent iron nanoparticles in the adsorption of hexavalent chromium. Spectrochim Acta A., 116, 17–25, 2013.

Synthesis of Spray Deposited ZnO Nanoparticle Thin Film for the Application of Dye-Sensitized Solar Cell A. Amala Rani and Suhashini Ernest Department of Physics, Urumu Dhanalakshmi College, Trichy, Tamil Nadu

ABSTRACT ZnO film has been prepared on glass plate with concentration of 0.05 M consisting of 50 ml of solution using the spray pyrolysis technique. A dye sensitized solar cell (DSSC) was constructed by means of the obtained film which was also coated above the ITO (Indium Tin Oxide) substrate. N-719, iodide and platinum coated ITO glass plates were used as the dye, electrolyte and counter electrode respectively. XRD confirms that the structure of the film was polycrystalline having wurtzite structure. The morphology of the surface was analyzed through SEM studies. The DSSC shows an optical transmittance of approximately 75% in the visible region. The photoluminescence study reveals the band edge transition and crystal defects in the material. The efficiency of the obtained DSSC by sensitizing the film for 16 hours was, ŋ = 2.8%.

INTRODUCTION Dye-sensitized solar cells (DSSCs) are regarded as promising low cost solar cells with high light to energy conversion efficiency, due to their relative inexpensive manufacturing processes. Dyesensitized solar cells (DSSCs) are an attractive solar cell option because of their relatively low manufacturing costs and simple process technology [1, 2]. Since the first publication on dye-sensitized solar cells (DSSCs) with a high solar to electrical energy conversion efficiency of 7.1% by O’Regan and Grätzel in 1991, this kind of solar cell has attracted much interest. One of the reasons is the quite high efficiency in relation to their low production cost. Dye-sensitized solar cells (DSSCs) have been studied extensively as a potential inexpensive alternative to conventional silicon-based photovoltaic devices. A typical DSC comprises a dye-sensitized mesoporous TiO2 fabricated on a transparent conducting oxide (TCO) coated glass substrate, liquid electrolyte, and Pt counter electrode [3]. ZnO is a unique kind of metal oxide semiconductor with a 3.37 eV wide band gap and a high electron mobility of 115–155 cm2 V−1 s−1, which provides a tremendous possibility for application in DSSCs [4]. Zinc oxide (ZnO) has occupied an inevitable place among other metal oxides for many applications, due to its unique combination of interesting properties; such as non-toxicity, good electrical, optical and piezoelectric behavior, stability in a hydrogen plasmaatmosphere and lowprice [5,6]. Recently, ZnO semiconductors were also used as photoelectrode in DSSCs [7].Other metal oxides like SnO2, In2O3, Nb2O5, and ZnO have also been used as photoelectrodes for DSSCs [8–10]. Among these oxide materials, the band gap and the energetic position of ZnO are similar to those of TiO2 [11]. The electron injection rates from the excited dye into the TiO2 nanoparticles are ultra-fast, V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 239–244 (2015)

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on the order of femtoseconds, but the electron recombination rates are high due to low electron mobility and transport properties. Recently, zinc oxide (ZnO) has been explored as an alternative material in DSSCs. Additionally, ZnO can be easily processed into various nanostructures, such as nanoparticles, nanowires, nanosheets and nanotubes, which have unique features of photoexcited electron transport and light propagation due to light scattering or absorption. The electron transport and photovoltaic (PV) performance of DSSC has been improved mainly by controlling the morphology, particle size and thickness of the ZnO layer [12], which provides the better interfacial contact between the ZnOlayer and TCO. In this study, ZnO thin film of 0.05 M was prepared using the spray pyrolysis technique. The structural, morphological and optical properties were studied. Also a solution of 0.05 M was deposited above the indium tin oxide (ITO) coated glass substrate as the photo anode. N-719 and platinum coated ITO substrates were chosen as the photo sensitizer and counter electrode respectively which can be utilized for the fabrication of a dye-sensitized solar cell. The efficiency of the cell was calculated and reported for the duration of the dye sensitization of 16 hours.

EXPERIMENTAL DETAILS The dye-sensitized solar cell consists of an indium tin oxide coated glass plate. The ZnO thin film was deposited above the ITO glass plate. The obtained film was immersed in the dye solution and then sandwiched with the platinum coated ITO glass plate. The intermediate space was filled with the electrolyte. The two ITO glass plates were connected by means of an external load. In order to illuminate the DSSC, 100 mW/cm2 was used as the incident light. The open-circuit photo voltage and the short-circuit photocurrent of the DSSC was measured using NI USB 6009 Data acquisition system controlled with Lab VIEW software through a personal computer. The prepared photo anode film was studied by X-ray diffraction (XRD) using a D/max-2400 Xray diffraction spectrometer (Rigaku) with the radiation of Cu Kα which was operated at 40 kV and 100 mA from 20 to70°, and the speed of scanning was 15º min−1 at a step of 0.02º in order to confirm the structure. The morphology of the surface and the size of the particles of the ZnO films were determined using scanning electron microscopy (SEM, JOEL 6320 F). A UV-Vis spectrophotometer (Jasco-V-570) was used for measuring the absorbance and transmittance of the cell. Photoluminescence (PL) spectroscopy was taken at room temperature on a HORIBA jobin Yvon (Model) using a He-Cd laser with the excitation wavelength of 325 nm. RESULTS AND DISCUSSION Structural Analysis The X-ray diffraction analysis observed was shown in Figure 2 and was used to determine the phase of the crystal and size of the nanocrystalline material. The peak obtained was (101); this confirms that the film was polycrystalline in nature with hexagonal wurtzite structure. No other characteristic peaks of other impurities were observed in the XRD pattern and confirm the formation of single phase of ZnO with JCPDS Card no. 36–1451. The grains were perpendicular to the glass substrate situated in the c-axis. The size of the crystallite was calculated using the Scherrer equation, D = 0.9 λ/β cosθ

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Where, D is the crystallite size, β is the broadening of the diffraction line measured at half of its maximum intensity (rad.) FWHM and λ is the X-ray wavelength (1.5406 Ǻ) which was consistent with the SEM image.

SEM Analysis The ZnO thin film was studied for morphology of the surface which was shown in Figure 3. It has smooth surface which consists of discrete and closely packed particles which cover uniformly all over the surface exactly with good adherence with more pores.

Optical Analysis UV-Vis spectra of absorbance and transmission for ZnO thin film was studied as shown in Figure 4. and Figure 5. The edge of absorbance of the ZnO film was around 375 nm. The photo sensitizer has maximum absorption at nearly 500 nm. In the visible range of the electromagnetic spectrum, the film was rather transparent with an average transmittance of about 75% at 600 nm. One of the non-destructive spectroscopic methods was the photoluminescence which can collect the information about the electronic structure of a particular material. The light was made to fall on

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the sample and it was absorbed by the sample. During de-excitation, the sample emits the light which was known as the photo-excitation and this process was known as the photoluminescence, so that the light was incident upon the sample and the emitted light was collected. The light of shorter wavelength which has greater energy was preferable for the excitation of the material. The electrons inside the material moves from valence band to the excited states due to photo-excitation. When these electrons return to their equilibrium states, the excess energy was released so that there is emission of light which was known as the radiative process and if no light emission was known as the nonradiative process. Usually for semiconductor materials, the radiative transition was between the energy states in the conduction band and the valence band. Photoluminescence spectrum of ZnO thin film taken at room temperature was shown in figure. Two emission peaks were observed in the photoluminescence spectrum. A broad peak near UV emission band centered at 420 nm was due to the emission of free exciton. Another peak attributed to green emission in the visible region centered at 560 nm was also observed in the photoluminescence spectrum. And it was due to the amount of native defects such as Zinc interstitials, Zinc vacancies, Oxygen interstitials and Oxygen vacancies.

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Properties of Dye-Sensitized Solar Cell The incident light power 100 mW/cm2 was utilized for the measurement of the photovoltaic properties of the DSSC and the obtained values were collected in Table 1. The efficiency of charge collection, the rate of transport as well as the transfer of photo generated carriers and the light harvesting efficiency were the factors that depends on the performance of DSSC. Moreover the recombination of conduction band electrons with the electrolyte was higher and leads to lower fill factor. The Ru-complexed dye on a ZnO surface was dominated by carboxylate bidentate coordination. The resultant fill factor was low when compared to the earlier studies in the literatures because of the reality of absorption of dye on the surface and thus the fill factor was strongly affected by the efficiency of electron injection. The process of injection of electrons from the excited state of the dye to the conduction band of the ZnO film was due to the exact anchoring of the dye. When the electrode receives a better coating of the ZnO layer, the more electrons can be excited as the dye sensitized solar cell was exposed to light. The efficiency of the cell can be improved by developing the photo electrodes with larger surface area that has the ablility to absorb large amount of dye and synthesizing dyes with broader absorption ranges. The recombination losses can be reduced by raising the conduction band energy level of the metal oxide material which leads to an increase in open-circuit voltage. The porosity of the film was also most important because the electrolyte which consists of the redox ions has the capability to penetrate the film effectively in order to suppress the rate-determining step through diffusion of redox ions into the film. Viscosity of solvents in the electrolyte plays a major role for the improvement of efficiency. So solvents having lower viscosity were used in this study. The counter electrode should have high electro catalytic activity so that it can reduce the ions of tri-iodide and hence the ITO substrate was coated with platinum layer.

Sensitizing Time 16 hours

Jsc (mA cm–2)

Voc (V)

FF

Efficiency (ŋ)

9.50

0.62

0.47

2.8%

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CONCLUSION ZnO thin film was prepared using the spray pyrolysis technique. Also deposited above the ITO substrate and immersed in the solution of N-719 dye for 16 hours. It was sandwiched with the platinum coated ITO substrate. The intermediate space was filled with an iodide electrolyte. The terminals were taken from the two ITO coated glass substrates through the external load. The surface consists of discrete and closely packed particles for good absorption of dye. XRD confirms that the structure of the film was polycrystalline having wurtzite structure. The absorption spectrum confirms that, the dye was exactly anchored to the surface of ZnO for efficient injection of electron. The optical transmittance was approximately 75% in the visible region. In order to achieve higher efficiency, work is in progress to change the nanostructure of the metal oxide semiconducting material which can be coated above the fluorine doped tin oxide (FTO) glass substrate to reduce the cost. REFERENCES [1] O’Regan, B. and Grätzel, M., A low-cost, high-efficiency solar cell based on dyesensitized colloidal TiO2 films, Nature, 353 (1991), 737. [2] Grätzel, M., Prog. Photovoltaics, 8 (2000), 171. [3] Grätzel, M., Acc. Chem. Res. 42 (2009), 1788. [4] He, C.X., Lei, B.X., Wang, Y.F., Su, C.Y., Fang, Y.P. and Kuang, D.B., Chemistry – A European Journal, 16 (2010), 8757–8761. [5] Lee, J.H., Ko, K.H., Park, B.O. and Cryst, J., Growth, 247 (2003), 119. [6] Cao, B., Cai, W., Li, Y., Sun, F. and Zhang, L., Nanotechnology, 16 (2005), 1734. [7] Keis, K., Magnusson, E., Lindstrom, H., Lindquist, S.E. and Hagfeldt, A., Sol. Energy Mater. Sol. Cells, 73 (2002), 51. [8] Hara, K., Horiguchi, T., Kinoshita, T., Sayama, K., Sugihara, H. and Arakawa, H., Solar Energy Mater. Solar Cells, 64 (2000), 115. [9] Sayama, K., Sugihara, H. and Arakawa, H., Chem. Mater, 10 (1998), 3825. [10] Katoh, R., Furube, A., Yoshihara, T., Hara, K., Fujihashi, G., Takano, S., Murata, S., Arakawa, H. and Tachiya, M., J. Phys. Chem. B 108 (2004), 4818. [11] Quintana, M., Edvinsson, T., Hagfeldt, A. and Boschloo, G., J. Phys. Chem. C 111 (2007), 1035. [12] Ito, S., Kitamura, T., Wada, Y. and Yanagida, S., Sol. Energy Mater. Sol. Cells, 76 (2003).

Heavy Metal Analysis on Mamandur Lake Sediments, Tamilnadu, India M. Sundarrajan and V. Arulesan Department of Physics, Sri Chandrasekharendra Saraswathi Viswa Mahavidyalaya, Enathur, Kanchipuram, Tamil Nadu

ABSTRACT The elemental concentration and spatial distribution of heavy metals (Cu, Cr, Pb, Ni and Zn) have been studied for surface sediments of Mamandur Lake, near Dusi village, Thiruvannamalai district, Tamilnadu, India. Toxicity parameters such as Enrichment factor (EF), Contamination Factor (CF) and Geo accumulation Index (Igeo) were calculated from the metal concentrations. The toxicity parameter values showed no higher degree of heavy metal contamination due to the above metals in the lake sediments. The existing values of concentration may be due to the anthropogenic activities like industrial effluents, vehicular emissions and other waste disposals to the environment.

INTRODUCTION The sediments on the Earth’s surface contain different minerals and metals as they are the weathered particles of the rocks. The metal input given by the mankind to the environment in the form of industrial wastages, vehicular, sewages etc. contaminate the river, beach and lake sediments. Heavy metal contamination in sediments is one of the major quality issues in many fast developing cities, as the maintenance of water quality and sanitation infrastructure did not increase along with population and urbanization growth. The main objectives of this study are (1) to determine the heavy metal (Cu, Fe, Cr, Pb, Ni and Zn) concentrations and distribution in Mamandur lake sediments. (ii) To calculate some important toxicity parameters to know contamination level of the lake sediments. MATERIALS AND METHODS Study Area The study a area is Mamandur Lake which is situated near Dusi village, Thiruvannamalai district, Tamil Nadu, India. Sample Collection The samples were manually collected in polyethylene bags from top surface (10 cm depth) using plastic spade during December 2013 in 10 locations (S1 to S10) each 10m apart. Methods Inductively Coupled Plasma optical emission spectrometry technique (Ahmed A. Alomary et al., 2007) was employed using Perkin-Elmer Optima 5300 DV and sediment digestion by Microwave Accelerated Reaction System (MARS) at SAIF, IITM, Chennai. The collected samples were ground and acid digested using MARS. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 245–248 (2015)

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Results Distribution of Heavy Metals The distribution of heavy metal (Cu, Fe, Cr, Pb, Ni and Zn)is shown in the Figure 1.The comparison of heavy metal concentration with the crustal average is given in Table 1. Table 1: Statistical Summary of Measured Heavy Metal Concentrations Cr

Cu

Pb

Ni

Zn

Average

Element

45.78

36.63

4.78

25.29

49.02

Max.

86.61

160.70

11.22

49.34

94.18

Min.

17.89

10.94

19.78

CrustalAverage * UCC**

3.064

0.389

100.00

55.00

12.50

75.00

70.00

90.00

45.00

20.00

50.00

95.00

* Crustal Average (CA, Taylor, 1964); ** Upper Continental Crust (UCC; Wedepohl, 1995).

Fig. 1: Distribution of Elemental Concentration

The average concentration of heavy metals are in the order Zn> Cr > Cu > Ni >Pb.

Estimating Level of Toxicity Enrichment Factor (EF) The Enrichment Factor differentiates the metal contamination to the environment by humanfromnatural contamination. (Gonzalez-Macias et al., 2006, Taylor, 1964, Hema Achyuthan et al., 2002).If EF < 1, it suggests a possible depletion of metals (Hema Achyuthan et al., 2002). If EF>1, it indicates the anthropogenic origin of metals. The variation of calculated EF values is shown in the following Figure 2.

Heavy Metal Analysis on Mamandur Lake Sediments, Tamilnadu, India

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Fig. 2: Variation of EF Values along Experimental Sites

Contamination Factor (CF) CF is the ratio between the sediment metal concentrationto the background value of the metal (Nobi et al., 2010, Turekian and Wedepohl, 1961) and the variation of CF values along the sampling sites is shown in the following Figure 3.

Fig. 3: Variation of Contamination Factor (CF) Values along Experimental Sites

Geo Accumulation Index (Igeo) The Geo Accumulation index (Igeo), defined by Muller (1979), is also a measure of the metal pollution in aquatic sediments (Nobi et al., 2010).The distribution geo-accumulation index (Igeo) values is shown in Figure 4.

Fig. 4: Variation of Geo Accumulation Index (Igeo) Values along Experimental Sites

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DISCUSSION Enrichment Factor The mean EF value of Zn, Cu, Cr, Pbarehigher than 1. This shows the accumulation of above heavy metals is of anthropogenic origin in the study area. The EF value of Ni is 0.91 and is due to the crustal origin with some depletion in the region. Contamination Factor (CF) According to Jayaprakash et al., 2010, if the CF ≤ 1, it shows a low contamination factor. The average CF values of the observed metals are in the order: Cu > Zn > Ni & Cr > Pb. Since these values are less than 1, it shows a low contamination factor with anthropogenic origin (industrial effluents, vehicle emission and waste disposal). Geo Accumulation Index (Igeo) Igeo values were calculated using world crustal average concentrations given by Turekian and Wedepohl (1961). From the Figure 3, the negative Igeo values show the lower contamination levels. CONCLUSION From the toxicity parameter results, it is observed that there is no higher degree of contamination in the lake sediments of the study area by the metals Zn, Cu, Cr, Pb and Ni. The lower contamination levels may be due to industrial effluents, vehicular emissions and other waste disposals to the environment. REFERENCES [1] Ahmed A. Alomary et al. (2007). “Determination of heavy metals (Cd, Cr, Cu, Fe, Ni, Pb, Zn) by ICPOES and their speciation in Algerian Mediterranean Sea sediments after a five-stage sequential extraction procedure”, Environmental Monitoring and Assessment, Vol. 135, (1-3), 265–280. [2] Gonza’lez-Mac’ias, C., Schifter, I., et al. (2006). “Distribution, enrichment and accumulation of heavy metals in coastal sediments of Salina Cruz Bay, Mexico”, Environ, Monit, Assess., 118:211–230. [3] Hema Achyuthan, D. et al. (2002). “Trace metals concentration in the sediments cores of estuary and tidal zones between Chennai and Pondicherry, along the east coast of India,” Indian Journal of Marine Science, 21, 141–149. [4] Jayaprakash et al. (2010). “Accumulation of total trace metals due to rapid unbanization in microtidal zone of Pallikaranai marsh, South of Chennai, India”, Environ. Monit. Assess., 170(1–4), 609–629. [5] Muller, G. (1979). “Schwermetalle in den sediment des Rheins, Veranderungem Seit 1971”, Umschau, 79; 778–783. [6] Nobi, E.P. (2010). “Geochemical and geo-statistical assessment of heavy metal concentration in the sediments of different coastal ecosystems of Andaman Islands, India”, Estuar Coastal Shelf Sci., 87: 253– 264. [7] Nriagu, J.O. and Pacyna, J. (1988). “Quantitative Assessment of Worldwide contamination of Air, Water and Soil by Trace Metals”, Nature, 333: 134–139. [8] Nriagu, J.O. (1989). “A Global Assessment of Natural Sources of Atmospheric Trace Metals”. Nature, 338: 47–49. [9] Pyeong_Koo, Lee et al. (2005). “Metal contamination and solid phase partitioning of metals in urban roadside sediments”, Chemosphere 60 (2005), 672–689 (2005). [10] Taylor, S.R. (1964). “Abundance of chemical elements in the continental crust; A new table”. Geochimicaet Cosmochimica Acta, 28(8): 1, 273–1, 285.doi:10.1016/0016-7037 (64), 90129–2. [11] Turekian, K.K. and Wedepohl, K.H. (1961). “Distribution of the Elements in some major units of the Earth's crust. Geological Society of America”, Bulletin 72: 175–192.

Electro Chemical and Photo Catalytic Enactment of Recovered MnO2 from Consumed Dry Cell Batteries M. Mylarappa, V. Venkata Lakshmi, L.S. Nandeesh1, K.R. Vishnu Mahesh2, H.P. Nagaswarupa3, K.N. Shravana Kumara2, N. Raghavendra4 and D.M.K. Siddeswara5 Research Centre, Department of Chemistry, AMC Engineering College, Bannerghatta Road Bangalore, Karnataka & Affiliated to Department of Studies and Research in Chemistry, Tumkur University, Tumkur, Karnataka 1 Research Centre, Department of Chemistry, SJRC College, Bangalore 2 Department of Chemistry, ACS College of Engineering, Bangalore 3 Research Centre, Department of Chemistry, EWIT, Bangalore 4 CMRTU, RV College of Engineering, Bangalore 5 Department of Chemistry, AIEMS, Bangalore

ABSTRACT The objective of the existing research was essentially focused on recovery of MnO2 from consumed dry cells by employing adapted hydrometallurgical process. Experimental tests for the recovery of MnO2 present in the dry cell batteries have been carried out by two acidic reductive leachants namely oxalic acid and hydrogen peroxide. Elemental composition of recovered metals from dry cells were confirmed by Energy Dispersive X-ray analysis (EDAX). Surface morphology of the recovered metals was examined using Scanning Electron Microscopy (SEM). Phase composition of the recovered metals from dry cell batteries were confirmed from X-ray Diffract meter (XRD). Cyclic Voltammetry (CV) studies were carried out to clarify the reversibility of the reactions. Obtained MnO2 catalyst was applied to degrade different non-volatile compounds such as Methyl Orange (MO), Methyl Blue (MB), Indigo carmine (IC) and Rhodamine B (RB). The performance of MnO2 shows fast degradation of dyes of high concentration. Keywords: Dry Cell Batteries, Recovery, Zn, Mn, Electrochemical, Catalytic Activity.

INTRODUCTION The dry cell batteries are used in radios, recorders, toys, remote controls, watches, calculators, cameras, and in many other objects. The waste batteries cause a serious anxiety due to their poisonousness, abundance and durability in the environment [1, 5]. The hydrometallurgical methods are the most popular process in all over the world because of its environmentally suitable and economical to treat even low zinc and manganese containing materials on small scale with high purity and low energy requirements [2, 3]. Hence, the treatment of these wastes for the recovery of manganese is vigorous for discarded material to raw material recycling. Two different acid-reductive leaching agents have been investigated; sulphuric acid - oxalic acid and sulphuric acid- hydrogen peroxide. V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 249–254 (2015)

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MnO2 is economic and commercial important with applications in different fields such as battery industry, catalysis, water treatment plants, steel industry and chemicals. In this study shows to recover manganese as MnO2 from consumed dry cell using a hydrometallurgical process, without altering the concentration of zinc in solutions that can be recovered by precipitation or electro winning [4]. The aim of this work is to study the applicability of electrochemical and photo catalytic enactment of MnO2 using a hydrometallurgical process and the catalytic action of MnO2 is due to their high efficiency in the reaction/oxidation cycles [5]. The effects of the recovered conditions and crystallinity of MnO2 on the catalytic performance in degradation of high concentration dyes (methylene blue indigo carmine and Rhodamine B) were intensively progressed [6].

EXPERIMENTAL Recovery of MnO2 from Dry Cells Recovery of manganese as MnO2 from the leaching solution is possible at room temperature without special purification of the solution, and preserving a high efficiency. After the complete reductive acid leaching process, selective precipitation test was carried out at room temperature. Taken required quantity of leached solution in a 500 ml beaker and a solution of 4M NaOH was added slowly to the beaker containing leach solution with constant stirring by magnetic stirrer. At the end of the precipitation, the solution in the beaker was filtered and the solid residue remained in the filter paper was dried in an oven at 100°C for 24 hours. The dried solid residue was characterised by the XRD, EDX and SEM to analyse elemental composition and morphology of the powder as shown in Figure 1. Characterization The Energy Dispersive X-ray analysis (EDX) was carried out to obtain the elemental composition of the metals in powder sample. The accurate size and morphology of the MnO2 studied from the Scanning Electron Microscopy (SEM) and X-ray diffraction spectroscopy (XRD). In Figure 1 (a to c) shows that manganese and oxygen contents were detected in that point, indicating the presence of large amount of manganese hydroxide [7]. The leaching residue showed almost similar particle size compared to that before leaching. Particles are well distributed throughout with little agglomeration; particle size ranges from 5 to 30 µm. EDX of the leaching residue indicated that it contained unleachable Mn species, which was attributed to a metal oxide species resulting from the initial cell materials [8].

c

Fig. 1: EDAX/SEM and XRD/ of MnO2 from Dry Cells

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ELECTROCHEMICAL AND PHOTOCATALYTIC STUDIES Cyclic Voltammetry Studies The MnO2 electrodes were prepared as 5%.....20% according to experimental plan. Electrochemical activity of MnO2 can be assessed by cyclic voltammetry. An electrochemical measurement involves three electrode system having working electrode, Ag/AgCl reference electrode and a platinum wire as counter electrode. Cyclic voltammetry (CV) studies were performed in potential between +1 to –1 V using 0.5M KCl and 0.5M Na2SO4 electrolytes at constant scan rate [9,11]. To evaluate the electrochemical reversibility (ER) of the sample, the potential window of CV was changed from +1 to –1 V and sweep rate 10 mV as shown in Figure 2a and Figure 2b. A smaller the value of EO-ER shows reversibility of the electrode reaction is more. Lesser the solution resistance (Rs), greater will be the conductivity of the sample. As the carbon layer more and tighter, the Rs reduce due to the increase of electrical conductivity. In Figure 2c and 2d, clearly found that the samples M1, M2, M4 using 0.5M KCl has lower ER compare to 0.5 Na2SO4 and M4 in 0.5M Na2SO4 shows lowest Rct among all the electrodes Indicating the better conductivity and confirmed that the capacitive behaviour is faster. Table 1: Preparation MnO2 Making Electrodes Electrode

Graphite (mg)

MnO2(mg)

%

M1

190

10

5

M2

180

20

10

M3

170

30

15

M4

160

40

20

Table 2: Electrochemical Reversibility, Charge Transfer Resistance and Capacitance of Electrodes Electrode M1

M2

M3

M4

Electrolyte

EO(mv)

ER(mv)

EO-ER

Rct (ohm)

C(F) × 10–5

0.5M KCl

0.3261

0.3040

0.0221

15.75

0.0282

0.5M Na2SO4

0.4443

0.3929

0.504

19.26

0.01414

0.5M KCl

0.3275

0.3065

0.021

17.53

0.01799

0.5M Na2SO4

0.3767

0.3409

0.0358

16.2

0.01598

0.5M KCl

0.6879

0.4591

0.2288

15.49

0.01945

0.5M Na2SO4

0.3385

0.3336

0.0049

16.74

0.01629

0.5M KCl

0.3385

0.3053

0.0332

21.29

0.01274

0.5M Na2SO4

0.6509

0.1245

0.0526

12.1

0.02385

252


Fig. 2: Cyclicvoltagramms and EIS Spectra of MnO2 Electrodes with Nyquist Plots

Photocatalytic Activity of MnO2 The photocatalytic enactment of the as-prepared sample was assessed through the photocatalytic degradation of Rhodamine –B (RB) and Indigo carmine (IC) under visible light irradiation. 60 mg of MnO2 was dispersed in 250 ml IC (20 ppm) and similarly Rhodamine-B aqueous solutions respectively. The mixed suspensions were first magnetically stirred in the dark for 30 min to reach the adsorption–desorption equilibrium. Under the ambient conditions and stirring, the mixed suspensions were exposed to visible light irradiation produced by a 400 W metal Philips lamp (wavelength: 254 nm). At certain time intervals, 5 ml of the mixed suspensions was extracted. The filtrates were analysed by recording UV-Vis spectra of RB and IC using a Spectratreats 3.11.01 Release 2A UV-Vis spectrophotometer. The UV-Vis absorption of MnO2 show an intense absorption band in the range 200 to 220 nm. In Figure 3 shows the UV-vis absorption spectra of RB and IC as a function of the catalytic reaction time [10]. Both RB and IC solutions turns colourless after 30 min that indicates that complete degradation of dye molecules by MnO2 after 30 min of reaction, the MnO2 showed a higher efficiency in degradation of IC compared to RB.

a

b

Fig. 3: UV-Vis Absorption Spectra of RB and IC as Role of Time Catalysed by MnO2

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CONCLUSION In this exploration, an aqueous technique was utilized to recuperate MnO2 from expended dry cells in expansive scale. X-Ray spectra of the solid MnO2 with the most noteworthy measure of Mn have demonstrated that the CMD (chemical manganese oxide) creation is chiefly manganese oxide. Electrochemical estimations meant that MnO2 acquired present high electrochemical movement when the accelerates are kept at 200°C for 24 hrs. The electric limit of this example demonstrated a superior in correlation with the business tests. It showed that the MnO2 has the best electrochemical execution at a high sweep rate of 10 mV s−1. The recuperated specimen displays low charge exchange resistance (Rct) and high capacitive authorization. The morphology and crystallinity of MnO2 improve in catalytic enactment in degradation of RB and IC. ACKNOWLEDGEMENTS The authors thanks VGST for the finance assistance extended to CISEE to complete the project. The authors also thanks the management and Principal of SJRC for their encouragement in extending the facilities at SJRC and the Principal and management of East West institute of technology for the laboratory facilities extended to complete the project. REFERENCES [1] Maria V., Gallegos, Lorena R., Falco, Miguel A., Peluso, Jorge E., Sambeth and Horacio Thomas, Recovery of manganese oxides from spent alkaline and zinc–carbon batteries, An application as catalysts for VOCs elimination Waste Management, 33, 1483–1490, 2013. [2] Agnieszka, Sobianowska, Turek, Włodzimierz, Szczepaniak, Monika, Zabłocka, Malicka, Electrochemical evolution of reducers-Recovery of Mn from Zinc-Mn and Zinc-C battery waste, Journal of Power Sources, 270, 668–674, 2014. [3] Baba A.A., Adekola A.F. and Bale R.B., Development of a combined pyro-and hydro-metallurgical route to treat spent Zinc-carbon batteries, Journal of power sources, 171, 838–844, 2009. [4] Paola Macolino, Adriana Loredana Manciulea, Ida De Michelis, Muresan Silviu Anton, Petru Ilea and Francesco Veglio, Manganese recovering from alkaline spent batteries by ammonium peroxodisulfate, Acta Metallurgica Slovaca, Vol. 19, No. 3, p, 212–222, 2013. [5] Maria V., Gallegos, Lorena R. Falco, Miguel A., Peluso, Jorge E., Sambeth, Horacio J., Thomas, Recovery of manganese oxides from spent alkaline and zinc–carbon batteries, An application as catalysts for VOCs elimination, Waste Management, 33, 1483–1490, 2013. [6] Andrade C.A., Tacca, M.M.E. Duart, Acid leaching and electrochemical recovery of manganese from spent alkaline batteries. [7] Sait Kursunoglu and Muammer, Kavya, Dissolution and precipitation of Zinc and Manganese obtained from spent Zinc-carbon and alkaline battery powder, Physicochem. Probl. Miner Process, 50, 39–53, 2014. [8] Jun Lu Li Li, Yang Ren, Xiao Xiao Zhang, Ren Jie Chen, Feng Wu and Khalil Amine, Ascorbic-acidassisted recovery of cobalt and lithium from spent Li-ion batteries, Journal of Power Sources, 218, 21–27, 2012. [9] Buzatu M., Aceanu S.S., Petrescu M.I., Ghica G.V. and Buzatu T., Recovery of zinc and manganese from spent batteries by reductive leaching in acidic media, Journal of power sources, 247, 612–617, 2014. [10] Chanhlin Yu, Gao Li, Longfu Wei, Qizhe Fan, Qing Shu and Jimmy C. Yu, Fabrication, characterization of β-MnO2 micro rod catalysts and their performance in rapid degradation of dyes of high concentration, Catalysis Today, 224, 154–162, 2014.

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[11] SiXu Deng, Dan Sun, ChunHui Wu, Hao Wang, JingBing Liu, YuXiu Sun and Hui Yan, Synthesis and electrochemical properties of MnO2 nanorods/graphene composites for supercapacitor applications, Electrochimica Acta., 111, 707– 712, 2013.

Optically Tuned Poly (3-Hexylthiophene-2, 5-DIYL)P3HT/PCBM (Modified Fullerene) Blend for Plastic Solar Cell Ishwar Naik, Rajashekhar Bhajantri1, Lohit Naik, B.S. Patil, Pragasam, Sunil Rathod and Jagadeesh Naik Department of Physics, Govt. Arts and Science College, Karwar 1 Department of Physics, Karnatak University, Dharwad E-mail: [email protected]

ABSTRACT The present work is focused to optimize the photoactive blend of Poly[3-hexylthiophene-2,5-dily) (P3HT) and [6,6]-Phenyl C61 butyric acid methyl ester (PCBM) for maximum absorption of the solar energy. P3HT: PCBM blends of weight ratio 3:1,1:1 and 1:3 are prepared inXylene as the solvent and glass coated samples are prepared by solution cast method. Samples are subjected toUV- VISIBLE spectroscopy by JASCO UV Vis NIR V 670 spectrometer. Spectral analysis revealed that 1:3 blend of P3HTwith PCBM has wide spectral sensitivity for absorption and can be used as photoactive material for construction of a plastic solar cell. Keywords: P3HT, PCBM, HOMO, LUMO, LSPR.

INTRODUCTION The first generation silicon based solar cells are suffering from material cost, installation cost, and fabrication complications. Even the second generation thin film solar cells are also not economical [1]. Plastic solar cells are promising because oftheir low cost, simple processing and flexibility. Since the efficiency is the main drawback of these solar cells, the scientists are looking for an efficient organic solar cell. The efficiencyof these cells are mainly determined by the photo active material used. The active material is the hetero junction blend of P and N type polymers. We have prepared photo active blends using P- type polymer Poly[3-hexylthiophene-2,5-dily) (P3HT) and N- type acceptor [6,6]Phenyl C61 butyric acid methyl ester(PCBM) with different weight ratios and then characterized by UV-VISIBLE spectroscopy. The spectra are analyzed for maximum absorption of solar energy by the photoactive material. The blend showing broad spectral sensitivity for absorption is selected as the best photo active blend. EXPERIMENTAL The p-type donor polymer P3HT and n-type acceptor PCBM are purchased from Sigma Aldrich Corporation. The solvent Xylene is procured from Rankem Chemicals. These chemicals are used as received without further purification.10 mg of P3HTand 10mg of PCBM are dissolvedin 100 ml of Xylene in separate beakers and magnetically stirred for 48 hrs at room temperature until clear solutions are formed. The resulting solutions are of concentrations 0.1mg/ml each. The solutions are V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 255–258 (2015)

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blended withP3HT: PCBM weight ratios of 3:1, 1:1 and 1:3 keeping total weight of the film fixed at 4mg.The mixtures are magnetically stirred for 3 days at room temperature and then transferred to 3cm diameter petri-plates, dried at room temperature and then at about 50°C in hot air oven.

RESULT AND DISCUSSION Samples are characterizedusing JASCO UV Vis NIR V-670 spectrometer. Pure P3HT film has absorption extending from 300 nm to 650 nm. The Spectrum has two peaks at 520 nm and 560 nm withone shoulder around 620 nm. The onset of absorption is 650 nm (Figure 1). Pure PCBM film shows strongest absorption in the UV region with a broad tail of absorption extending up to 800 nm (Figure 5). The strong absorption in the UV region arises from HOMOLUMO (Highest Occupied Molecular Orbital-Lowest Unoccupied Molecular Orbital) transitions [2] or in other words the strongest absorption is attributed to the formation of higher excited singlet states

Fig. 1: Spectrum of Pure P3HT Film

Fig. 2: Spectrum of 3:1, P3HT: PCBM

Fig. 3: Spectrum of 1:1, P3HT: PCBM

Fig. 4: Spectrum of 1:3 P3HT: PCBM

Optically Tuned Poly (3-Hexylthiophene-2, 5-DIYL)P3HT/PCBM Blend for Plastic Solar Cell

Fig. 5: Spectrum of Pure PCBM

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Fig. 6: Overlay Spectra of all Films

[3]. The spectra are in good agreement with the results reported earlier. Spectra for all other blends are the superposition of the component spectra. Effect of PCBM in the blend is to reduce the absorption of P3HT in the visible region followed by increase of absorption in UV region and beyond 650 nm. Although the 3:1 and 1:1 blends has enough absorption in the visible region, the absorption coefficient of 1:3 blend is more in UV region and beyond 650 nm. Relatively 1:3 blend has wide spectral sensitivity and can be considered as the best photoactive blend among the samples prepared.The absorption can be further enhanced by doping with metal nano particles, exploiting Localised Surface Plsmon Resonance (LSPR) or by dye sensitization. Nano doping/dye sensitization of1:3P3HT : PCBM blend and construction of solar cell using the same is our future work.

CONCLUSION We have investigated UV- VISIBLE absorption spectra for 3:1, 1:1,1:3 blends of P3HT:PCBM mixed p- n junction photoactive material along with their pristine glass coated films. Spectral analysis indicated that increased weight percentage of PCBM in the blend has broadened the spectral region of absorption. 1:3 blend ofP3HT:PCBM shows a wide spectral absorption and selected as the best photo active blend.By doping the blend with metaloxide nano particles or by dye sensitization the absorption can be further enhanced.Exploiting Plasmon Resonance through nano doping on the selected blendis our further study. Even it is planned to carry out dye sensitization of the active blend. Finally we conclude that 1:3 blend ofP3HT: PCBM can be used as the photoactive material for constructing a plastic solar cell and the construction of the solar cell is under progress. ACKNOWLEDGEMENT Thanks to UGC for sanctioning the Minor research project entitled “construction and characterization of an organic solar cell (OPV) devised from a self made low cost spin coating machine”.Order No.: 1419-MRP/14-15/KAKA088/UGC-SWRO.

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REFERENCES [1] Tipnis, Ritesh, Darin Laird, Mathew Mathai, Material Matters, 2008, 3.4, 92. [2] Mohamad, Khairul Anuar; Alias, Afishah; Saad, Ismail; Gosh, Bablu Kumar; Uesugi, Katsuhiro, et al., J. Chem. Chem. Eng., 8 (2014), 476–481. [3] (Kees) Hummelen, J.C., “Improved fullerene materials for plastic photovoltaics”. web: http://www. rug.nl/msc/research/groups/molecularMaterialsDevices.

Graphene Based Surface Plasmon Resonance to Differentiate Metallic Nanoparticles from Their Solutions; Theoretical and Experimental Approach Nasih Hma Salah, David Jenkins, Richard Handy and Larissa Panina School of Computing, Electronics and Mathematics, Plymouth University, Drake Circus, Plymouth, PL4 8AA, UK E-mail: [email protected]

INTRODUCTION Due to their high sensitivity [1, 2] and reliability[3], Surface Plasmon Resonance (SPR) based sensors are commonly used in bio-sensing application. The main benefit of using the SPR technique, is that it allows for label-free detection of low concentrations of analyte[4]. The SPR method relies on changes in the refractive index near the metal-sample interface of the sensor; where a change in the refractive index changes the SPR coupling conditions. Using this information it is possible to obtain information, such as the presence, concentration or purity of an analyte. In most cases, the refractive index is measured by determining the SPR angle (angular interrogation method) of multi-layered optical system, which contains the analyte: Other methods include wavelength, phase, and intensity interrogation [5]. In this work, angular interrogation has been concentrated on due to its high sensitivity [6] compared with wavelength, and intensity interrogation techniques, and its simplicity compared with phase interrogation techniques [7]. An advantage of SPR sensing devices is that they are unaffected by interference from light scattering within the sensing medium. This is due to the small sensing area, given by the penetration depth of the SPP, which has been approximated to be between 200 and 300 nm [8]. Only particulates within the area closest (< 300 nm) to the metal film cause a significant change in the SPR response. This is advantageous if the refractive index of the analyte suspended in solution is of interest.A wide range of SPR based sensors are in use that generate a signal specific to the fluctuation in the refractive index at the surface of sensor. In particular the SPR based sensing technique for immunoassays [9]; where it is used to measure specific antibody-antigen reactions. By using this technique the antibodies bind to the metallic surface (usually gold due to the ease of conjugation with antibodies [9], this enables the antigens to be passed into the chamber using a micro fluidic channel (As shown in Figure 1a, b). This creates local specific binding sites for the antigens; where the binding event causes a change in the effective refractive index, and hence the SPR conditions Figure 1 (c, d). The most common SPR sensor system is based on the Kretschmann configuration [11], which is extensively used for chemical and bio-molecular sensing with high sensitivity [3]. A demonstration of how the Kretschmann configuration can be used for detecting analytes in solution can be seen in Figure 1 as well. The thiol groups, from the disulphide bridge, of the antibodies creates a covalent bond to the surface of the gold V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 259–264 (2015)

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(or any other thiol-rich surface), immobilising them in an evenly spaced manner [12]. This allows them to be densely packed on the surface of the sensor, hence creating specific antigen binding sites [12].

Binding Event θ2

θ1

Angle θ1

θ2

θ2

θ1

(a)

Time

(b)

Fig. 1: Illustrates the SPR immunoassay technique, a) and b) Antibody functionalised SPR sensor layer on the top of a conventional glass prism/gold plasmonic system.c) Before and after the binding event, the angles (θ and θ ). d) The sensogram response changing following binding event[10].

SIMULATED RESULTS AND DISCUSSION Figure 6. Shows that changes in real component of the refractive index of the absorbing medium have an effect on the reflectivity and resonance angle. This study produced results which corroborate the findings of[13–15]; and similar findings were obtained in the case of transparent medium[16]. It is encouraging to compare this figure with a similar figure presented by Yingying (2013); who indicated that the both, intensity and angular standard interrogation methods are applicable to both absorptive and transparent, media. For that reason, the subsequent discussion is focused on reviewing the angular, and intensity, interrogation methods using a new combination of media for a four layered system. This system has the arrangement of Cr (2 nm)/Ag (40 nm)/Au (5 nm)/Gr (0.33 nm) for detecting the absorptive media, where the Graphene (Gr) is single-layered. Here chromium acts as an adhesion layer, silver as a plasmonic layer, gold as a protective layer and graphene is used to enhance the sensitivity of the SPR system. By using a 5nm protection layer of gold on top of the silver layer, the optimized thicknesses of the silver film is 40nm. Otherwise, without the Au protection layer, the optimised thickness is 50nm for Ag with one layer of graphene. When a number of simulated results were compared, it became clear that as the thickness of the Ag decreases, the maximum absorption increases. As shown in Figure 6, the intensity interrogation has been realised by obtaining a range of linear measurement values, which have been obtained by sweeping the incident angle. The relation between the SPR reflection and the fixed real component of the refractive index, as well as the changing imaginary components. Also, it worth to be mentioned that one can differentiate between the incident angles at the maximum of absorption of the SPR reflectivity curve for samples having 1.33126 to 1.380 as real components of the refractive index. It is evident from the figure that the resonant angle will shift as the bulk refractive index of the sensing media increases, Figure 7. Furthermore, when the imaginary part is more dominant than the real part, the change in the resonant angle is much lower, and therefore the sensitivity of the sensor is much less. This is supported by Figure 6). The higher the imaginary component of the refractive index, the broader the SPR peak will be (Figure 6). This can

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261

lead to errors in the determination of the resonant angle, which would raise in equivalent noise conditions. 1.0

0.8

ATR (%)

0.6

n=1.333, k=0 n=1.335, k=0 n=1.34, k=0 n=1.36, k=0 n=1.38, k=0 n=1.4, k=0 n=1.33126, k=0.001 n=1.33126, k=0.005 n=1.33126, k=0.01

0.4

0.2

0.0 56

58

60

62

64

66

68

70

72

74

76

Angle(Degrees)

78

80

82

84

1.0

1.0

0.8

0.8

0.6

0.6

ATR (%)

ATR (%)

Fig. 6: Compares the Reflectivity of the Different Samples with Different Real and Imaginary Components Obtained from Theoretical Calculation

0.4

Theo.2nm Cr/35nm Ag/5nm Au/0.33nm Gr Theo.2nm Cr/40nm Ag/5nm Au/0.33nm Gr Theo.2nm Cr/45nm Ag/5nm Au/0.33nm Gr Theo.2nm Cr/50nm Ag/5nm Au/0.33nm Gr

0.2

0.4 Theo. 2nm Cr/35nm Ag Theo. 2nm Cr/40nm Ag Theo. 2nm Cr/45nm Ag Theo. 2nm Cr/50nm Ag

0.2

0.0

0.0 56

58

60

62

64

66

68

70

Angle(Degrees)

72

74

76

78

50

80

52

54

56

58

60

62

(a)

66

68

70

72

74

76

78

80

(b) 1.0

1.0

0.8

0.8

0.6

ATR (%)

0.6

ATR (%)

64

Angle(Degrees)

0.4

0.4 0.2

-1

Theo. 62.5mgl AgNO3

0.2

-1

Theo. 62.5mgl AgNO3/0.33nm Gr

Theo.2nm Cr/40nm Ag/5nm Au/H2O Theo.2nm Cr/40nm Ag/5nm Au/0.33nm Gr/H2O

0.0 56

0.0 56

58

60

62

64

66

68

70

72

74

76

78

80

58

60

62

64

66

68

70

72

74

76

78

80

Angle(Degrees)

Angle(Degrees)

(c)

(d)

Fig. 7: These graphs show four results of the intensity of the reflection light with regard to incident angle. (a) and (b) SPR reflectivity from different thickness of the silver layer with and without 5 nm gold protection and graphene layer on top. (c) and (d) effect of the graphene layer on the SPR results for same multilayered system with regard to pure water and AgNO3 solution as a sample without imaginary part.

262


COMPRESSION OF EXPERIMENTAL AND THEORETICAL RESULTS With regard to experimental result, set of experiments have been done. The first result, Figure 8(a), shows the comparison between experimental (green triangles), and theoretical (black solid), of the multilayered SPR system (Cr (2 nm)/Au (50 nm)/Air), with a range of incident angles from 35° and 56°. Whereas there is a good agreement between reflectivity from (Cr (2 nm)/Ag (40)/Au (5 nm)/Gr (0.3nm)) SPR system with regard to samples with and without imaginary component of refractive index Ag NPs and AgNO3, respectively. The maxima of the absorption from the incident light occurs between the incident angles of 69.0° and 70° in this case, which silver sample with 62.5 mgl–1 shows more absorption in the experiment result and the same shift in the resonance angle as well. A range of linear measurement values can be achieved by altering the incident angle and the sensitivity of the measurement the increase in real component of the refractive index caused by higher imaginary component, which results in a reduction of the sensitivity of the SPR system. Hence in this interrogation technique, an increased resolution can be achieved by selecting a wavelength which evades the absorption band of sample. 1.0

ATR (%)

0.8

0.6

0.4

Theo. Air Expe. Air

0.2

0.0 36

38

40

42

44

46

Angle(Degrees)

48

50

52

54

(a) 1.0

ATR (%)

0.8

0.6

0.4 Theo. H2O -1

Theo. 62.5 mgl AgNO3

0.2

-1

Theo. 62.5 mgl Ag NPs -1

Expe. 62.5 mgl AgNO3 -1

Expe. 62.5 mgl Ag NPs

0.0 66

68

70

72

74

Angle(Degrees)

(b)

Fig. 8: These graphs compare the experimental result and the theoretical one. (a)experimental (green triangles), and theoretical (black solid), of the multilayered SPR system (Cr (2 nm)/Au (50 nm)/Air). (b) Shows a good agreement between reflectivity from (Cr (2 nm)/Ag (40)/Au (5 nm)/Gr (0.3nm)) SPR system with regard to Ag NPs and AgNO3, respectively.

Graphene Based Surface Plasmon Resonance to Differentiate Metallic Nanoparticles

263

CONCLUSIONS In this article, SPR sensors using two interrogations for the determination of real component of the refractive index of the sample are evaluated by numerical simulation and experimental data. In comparison with the analysis of transparent media (materials without imaginary part of refractive index within the visible range), the sensitivity has been demonstrated to increase by the use of both intensity and angular interrogation. However, in case of intensity and angle interrogations, such a wavelength must be selected which evades the absorption bands ( ). Furthermore, in case of these interrogations, sensitivity gets adversely affected if the same thickness of plasmonic film which has been optimised for nonabsorptive sample is employed for an absorptive sample. Yet, it is worth mentioning that the thickness of multi-layered thin film affects the sensitivity of both interrogation methods. It can be stated that optimal thickness reduces with the increase in absorption of the sample. In other words, once the optimisation of thickness of plasmonic film has been done efficiently, maximum resolution is demonstrated by the SPR sensor. REFERENCES [1] Lahav, A., Auslender, M. and Abdulhalim, I., Sensitivity enhancement of guided-wave surface-plasmon resonance sensors. Optics letters, 2008. 33(21), pp. 2539–2541. [2] Jha, R. and Sharma, A.K., High-performance sensor based on surface plasmon resonance with chalcogenide prism and aluminum for detection in infrared. Optics letters, 2009. 34(6), pp. 749–751. [3] Maharana, PP.K. and Jha, R., Chalcogenide prism and graphene multilayer based surface plasmon resonance affinity biosensor for high performance. Sensors and Actuators B: Chemical, 2012. [4] Liu, Q. and Wang, PP., Cell-based biosensors: principles and applications. 2009: Artech House. [5] Homola, J., Koudela, I. and Yee, S.S., Surface plasmon resonance sensors based on diffraction gratings and prism couplers: sensitivity comparison. Sensors and Actuators B: Chemical, 1999. 54(1), pp. 16–24. [6] Alleyne, C.J., et al., Enhanced SPR sensitivity using periodic metallic structures. Optics express, 2007. 15(13), pp. 8163–8169. [7] Salazar, A., et al. Electromagnetic modeling of surface plasmon resonance with Kretschmann configuration for biosensing applications in a CMOS-compatible interface. in SPIE OPTO. 2013. International Society for Optics and Photonics. [8] Raether, H., Surface Plasmon on Smooth and Rough Surfaces and on Gratings. 1988, Berlin Heidelberg New York London Paris Tokyo, Springer-Verlag. [9] Mullett, W.M., Lai, E.P. and Yeung, J.M., Surface plasmon resonance-based immunoassays. Methods, 2000. 22(1), pp. 77–91. [10] Salah, N.H., Jenkins, D. and Handy, R., Graphene and its Influence in the Improvement of Surface Plasmon Resonance (SPR) Based Sensors, a Review. 2014. [11] Kretschmann, E. and Raether, H., Radiative decay of non radiative surface plasmons excited by light. Zeitschrift Fuer Naturforschung, Teil A, 1968. 23, pp. 2135. [12] Neves Petersen, M.T., et al., Photonic activation of disulfide bridges achieves oriented protein immobilization on biosensor surfaces. Protein science, 2006. 15(2), pp. 343–351. [13] Akimoto, T., et al., Refractive-index and thickness sensitivity in surface plasmon resonance spectroscopy. Applied optics, 1999. 38(19), pp. 4058–4064. [14] Durou, C., Giraudou, J.-C. and Moutou, C., Refractive indexes of aqueous solutions of copper (II) sulfate, zinc sulfate, silver nitrate, potassium chloride, and sulfuric acid for helium-neon laser light at. theta. = 25. deg. Journal of Chemical and Engineering Data, 1973. 18(3), pp. 289–290.

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[15] Kotsev, S., et al., Refractive index of transparent nanoparticle films measured by surface plasmon microscopy. Colloid and Polymer Science, 2003. 281(4), pp. 343–352. [16] Zhang, Y., Study of an absorption-based surface plasmon resonance sensor in detecting the real part of refractive index. Optical Engineering, 2013. 52(1), pp. 014405–014405.

Titanium Dioxide Supported Ruthenium Nanoparticles for Carbon Sequestration Reaction Praveenkumar Upadhyay and Vivek Srivastava Basic Sciences: Chemistry, NIIT University, NH-8 Jaipur/Delhi Highway, Neemrana, Rajasthan E-mail: [email protected]

ABSTRACT Ru metal doped TiO2 nanoparticles using a sole gel method with and without ionic liquid were synthesized. Ru metal is well dispersed while utilizing ionic liquid as reaction medium for catalyst synthesis with respect to Ru-TiO2 catalyst. TEM image for Ru-TiO2-IL catalyst reveals, stable, well dispersed and agglomeration free Ru metal doped TiO2 nanoparticles. CO2 Hydrogenation reaction in task specific ionic liquid medium, offered the formic acid in high TON/TOF value. 5 times catalysts recycling is the major outcomes of the proposed protocol. Keywords: Ruthenium Metal, Titanium Dioxide, Nanoparticles, Hydrogenation, Carbon Sequestration, Formic Acid.

INTRODUCTION Various physiochemical methods were reported to fix the CO2 gas, such as fixation as carbonates, geological or ocean storage or afforestation. [1–4] However, these approaches have severe drawbacks in terms of economic factors, safety, efficiency, and reliability of their immediate application. It is also known that functionalized ionic liquid mediated Ru (II) compounds can promote the partial hydrogenation of CO2 to formic acid where the ionic liquid not only capture the formic acid formed but also shift the equilibrium of hydrogenation reaction. The pre-organized structure of imidazolium based ionic liquids (ILs) provides structural directionality though their hydrogen bond, as opposed to classical salts in which the aggregates display charge-ordering structures. [4] The structural organization of ILs provides a special “entropic drivers” for natural, precise, and prolonged assembling of nanoscale assemblies. [5, 6] We successfully applied imidazolium ionic liquids as a template, additive, and solvent for the synthesis of a glut of transition-metal nanoparticles. [7] The catalytic properties (activity and selectivity) of these soluble metal nanoparticles direct that they possess a pronounced surface like (multi-site) rather than single-site-like catalytic properties. [8–10] The main goal of this proposed work is to develop supported functionalized ionic liquid ruthenium nanoparticles [11] in TiO2 (nanoparticles and nanotubes) for the hydrogenation of CO2. Experimental Reagent Plus® grade ruthenium (III) chloride hydrate and titanium tetra isopropoxide were purchased from Aldrich. Other ReagentPlus® and extra pure grade chemicals were purchased from spectrochem. Nuclear Magnetic Resonance (NMR) spectra were recorded on a standard Bruker 300WB spectrometer with an Avance console at 400 and 100 MHz for 1H NMR. All the hydrogenation reactions were carried out in a 100 mL stainless steel autoclave (Amar Equipment, India). The catalyst V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 265–270 (2015)

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material was characterized by TEM (Hitachi S-3700N) and Energy-dispersive X-ray spectroscopy (EDX) (Perkin Elmer, PHI 1600 spectrometer). FTIR data for all the samples were studied with Bruker Tensor-27. 1-Butyl-3-methylimidazolium Chloride, 1, 3-di(N, N-dimethylaminoethyl)-2methylimidazolium trifluoromethanesulfonate ([DAMI][TfO]), 1, 3-di(N, N-dimethylaminoethyl)-2methylimidazolium bis (trifluoromethylsulfonyl) imide ([DAMI][NTf2]) and 1-butyl-3methylimidazolium chloride ionic liquids were synthesized as per reported procedure. [12, 13] FTIR data for all the samples were studied with Bruker Tensor-27. The morphology of catalysts was investigated by transmission electron microscopy (TEM) using a Philips CM12 instrument. XRD was performed on Philips X-Pert diffractometer. The normalized X-ray absorption near stretcher (XANES) spectra was recorded on BL01C1.

RESULT AND DISCUSSION We synthesized two different ruthenium metal doped TiO2 nanoparticles with and without ionic liquids, Ru-TiO2-IL and Ru-TiO2 -respectively, followed by sol-gel method and calcined over 250°C for 5 hours. The XRD pattern of TiO2 was compared with Ru-TiO2-IL and Ru-TiO2 (Figure1) [14] from the wide angle XRD pattern, the titania samples were found only in anatase phase with their characteristic diffraction peaks of 2 degree values near 42– 44°, assigned to metallic ruthenium (PDF no. 06–0633) were observed for Ru-TiO2 catalyst. However, there were no characteristic peaks of Ru° observed on the Ru-TiO2-IL catalyst, indicating a high dispersion of Ru on the TiO2 support.

Fig. 1: XRD data for Ruthenium Metal Doped Titanium Dioxide Nanoparticles

The FTIR analysis of TiO2 with respect to Ru-TiO2-IL and Ru-TiO2 catalysts was carried out in the range of 400–4000 cm–1 (Figure 2). In Ru loaded TiO2, a clear peak of O-Ti-O bonding were found near 445 and 708 cm–1. The representing band for δ-H2O bending appeared near to 1605 cm–1. A broad absorption band showing the-O and O-Ti-O flexion vibration band found between 400 cm1 and 800 cm–1. The XANES spectra at Ru K-edge of the Ru-TiO2-IL and Ru-TiO2 catalysts with respect to Ru foil were represented in the Figure 3. The XANES spectrum of the Ru-TiO2-IL catalyst was found similar to Ru foil, which indicates that the Ru species were reduced to the metallic sate, while XANES spectrum of Ru-TiO2 catalyst was found much higher than the Ru foil, which represents that the Ru supported on TiO2 remained in an oxidative state.

Titanium Dioxide Supported Ruthenium Nanoparticles for Carbon Sequestration Reaction

267

Fig. 2: Infrared Data for Ru-TiO2 Nanoparticles

Fig. 3: XANES Data for Ru-TiO2 Nanoparticles

TEM micrographs of TiO2, Ru-TiO2-IL and Ru-TiO2 are shown in Figure 4. Electron microscopy reveals the morphology of the TiO2, Ru-TiO2-IL and Ru-TiO2. It was clearly observed that for RuTiO2 catalyst, many severely strained ruthenium nanoparticles larger than 25±5nm were found on the surface of TiO2 while in Ru-TiO2-IL catalysts, ultrafine Ru nanoparticles with uniform particle size were dispersed on the surface of TiO2. Its worth noted here that no particles larger than 20 nm, observed despite our careful observation. More intuitively, the average particle size of the Ru-TiO2 catalyst was found to be 25 ± 5 nm. However, it was only 15±5nm with narrower particle size spreading for the Ru-TiO2-IL catalyst. These observations indicated that the reaction medium type could remarkably affect the dispersion of Ru on theTiO2 surface and ionic liquid to be an efficient reaction medium over conventional solvents to stabilize the smaller nano-sized particles of Ru. Theoretical (cation exchange capacity) and an experimental (ICP-AES) method was used to calculate the amount of Ru species in TiO2. Both theoretical and experimental values were found to be in good agreement, and 2.5 wt% Ru was found in Ru-TiO2-IL catalyst while in Ru-TiO2 catalyst 2.1wt % Ru metal calculated. This protocol also minimizes the loss of Ru nanoparticles during the process. Hydrogenation of CO2 was carried out using H2 gas in the presence of both the catalysts (without any

268


pretreatment) with functionalized ionic liquids separately at 80°C under high pressure reaction condition. After the reaction, formic acid was isolated from the reaction mass followed by the nitrogen flow at 125–130°C. The results obtained while optimizing the reaction conditions with respect to TON/TOF value of formic acid were summarized in table 1, entry 1–17. Acid –Base titration using phenolphthalein indicator and 1H NMR analysis was used to calculate the quantity of formic acid formed [12, 13].

(a) Ru-TiO2 Catalyst

(b) Ru-TiO2-IL Catalyst (Before catalysis)

(c) Ru-TiO2-IL Catalyst (After catalysis)

Fig. 4: TEM Data for Ruthenium Metal Doped Titanium Dioxide Nanoparticles (a, b, c)

Initially, both the catalysts were tested under same reaction condition for CO2 hydrogenation and high TON/TOF value was obtained with [DAMI][NTf2] immobilized Ru-TiO2-IL (Table1, Entry 1 &2). All the other important reaction parameters and technical variables were investigated using [DAMI][NTf2] immobilized Ru-TiO2-IL (Table 1, Entry 3–17). We obtained good TON/TOF value at 100°C when, the total H2/CO2 gas pressure was 40 MPa (Table1, Entry 3). Effect of water was also studied on the reaction kinetics of CO2 hydrogenation reaction only with 2 ml of water with a high TON/TOF value (Table 1, entry 12). CO2 may react with water and an amine group of ionic liquid to give offers bicarbonates which may act as a perfect substrate for the hydrogenation reaction. RuCl3 was also evaluated for the hydrogenation reaction, but formic acid was obtained with low TON/TOF value compared to [DAMI] [NTf2] immobilized Ru-TiO2-IL (Table 1, Entry 17).After the reaction, formic acid was isolated with the aid of N2 gas and the [DAMI] [NTf2] ionic liquid immobilized RuTiO2-IL went for a recycling test after washing with diethyl ether. [DAMI] [NTf2] ionic liquid immobilized Ru-TiO2-IL were recycled up to 5 times with slight loss of their catalytic action mainly

269

Titanium Dioxide Supported Ruthenium Nanoparticles for Carbon Sequestration Reaction

because of agglomeration of Ru NPs which was also confirmed by TEM analysis of Ru NPs (Figure 5). Table 1: Hydrogenation of CO2 to Formic Acid Using Ionic Liquid Immobilized TiO2 Dropped Ru Metal1 Entry

Catalytic System

P (H2) (P total) (MPa) 2

Temperature (°C)

Time (h)

TON3

1.

Ru-TiO2-IL/[DAMI][TfO]

20 (40)

80

1

252

2.

Ru-TiO2/[DAMI][TfO]

20 (40)

80

1

222

3.

Ru-TiO2-IL/[DAMI]

20 (40)

80

1

246

4.


20 (40)

100

1

253

5.


20 (40)

120

1

253

6.


20 (40)

50

1

195

7.


20 (40)

100

1.5

152

8.


20 (40)

100

0.3

85

9.


10 (20)

100

1

195

10.


30 (60)

100

1

252

11.

Ru-TiO2-IL/[DAMI][TfO]+ H2O (1 mL)

20 (40)

100

1

258

12.

Ru-TiO2-IL/[DAMI][TfO]+H2O (2 mL)

20 (40)

100

1

270

13.

Ru-TiO2-IL/[DAMI][TfO]+H2O (3 mL)

20 (40)

100

1

272

14.

Ru-TiO2-IL/[DAMI] [TfO] (0.100g)+ H2O (2 mL)

20 (40)

100

1

272

15.

Ru-TiO2-IL/[DAMI] [TfO] (0.500g)+ H2O (2 mL)

20 (40)

100

1

272

16.

Ru-TiO2-IL/[DAMI][NTf2]+ H2O (2 mL)

20 (40)

100

1

260

20 (40)

100

1

224

17.

4

[NTf2]

RuCl3 (0.07g) + [DAMI][NTf2](0.250g)

1. Reaction conditions: 0.250 g catalytic system; 2. The total pressure of the system is indicated in parentheses; 3. Turn over number = n (formic acid) n (Ru) –1 in one reaction cycle; 4. Turnover frequency = n (formic acid) n (Ru) –1h–1; 4. RuCl3. xH2O (50% Ru metal).

Fig. 5: Catalyst Recycling Experiment

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CONCLUSION Here, we reported the synthesis of air/moisture stable, narrow size distributed TiO2 supported Ru nanoparticles. Ru NPs in TiO2 support. [DAMI] [NTf2] ionic liquid immobilized Ru-TiO2-IL catalyst was found highly active in terms of TON/TOF value of formic acid over conventional and Ru-TiO2 catalyst. Effect of water was also studied during the CO2 hydrogenation reaction. The presence of functionalized ionic liquid as well as water was promising. Five times catalyst recycling, low catalyst loading and selectivity were the major outcomes of this proposed protocol. ACKNOWLEDGEMENT This work is financially supported by DST Fast Track (SB/FT/CS-124/2012). REFERENCES [1] Sakakura, T., Choi, J.C. and Yasuda, H., Chem. Rev., 107 (2007), pp. 2365–2387. [2] Thampi, K.R., Kiwi, J. and Gratzel, M., Nature, 327 (1987), pp. 506–508. [3] Zhang, Z.F., Xie, E., Li, W.J., Hu, S.Q., Song, J.L., Jiang, T. and Han, B.X., Angew. Chem. Int. Edit., 47 (2008), pp. 1127–1129. [4] Dupont, J. and Braz, J., Chem. Soc., 15 (2004), pp. 341–350. [5] Migowski, P. and Dupont, J., Chem. Eur. J., 13 (2007), pp. 32–39. [6] Antonietti, M., Kuang, D.B., Smarsly, B. and Yong, Z., Angew. Chem. Int. Edit., 43 (2004), pp. 4988– 4992. [7] Dupont, J., Fonseca, G.S., Umpierre, A.P., Fichtner, P.F.P. and Teixeira, S.R., J. Am. Chem. Soc., 124 (2002), pp. 4228–4229. [8] Scheeren, C.W., Machado, G., Dupont, J., Fichtner, P.F.P. and Texeira, S.R., Inorg. Chem., 42 (2003), pp. 4738–4742. [9] Scheeren, C.W., Machado, G., Texeira, S.R., Morais, J., Domingos, J.B. and Dupont, J., J. Phys. Chem. B 110 (2006), pp. 13011–13020. [10] Cassol, C.C., Umpierre, A.P., Machado, G., Wolke, S.I. and Dupont, J., J. Am. Chem. Soc., 127 (2005), pp. 3298–3299. [11] Silveira, E.T., Umpierre, A.P., Rossi, L.M., Machado, G., Morais, J., Soares, G.V., Baumvol, I.L.R., Teixeira, S.R., Fichtner, P.F.P. and Dupont, J., Chem. Eur. J., 10 (2004), pp. 3734–3740. [12] Srivastava, V., Catalysis letters, 144 (2014), pp. 1745–1750. [13] Srivastava, V., Catalysis letters, 144 (2014), pp. 2221–2226. [14] Wang, Y., Zhang, R., Li, J., Li, L. and Lin, S., Nanoscale Research Letters, 9(46) (2014). [15] Bagheri, S., Chekin, F. and Hamid, S.B.A., J. Chin. Chem. Soc., 61 (2014), pp. 702–706.

Water Suspended Graphene-Draped MnO2 for High Performance Supercapacitor P. Siva, M. Selvam, M. Vinoth, V. Rajendran and K. Saminathan Centre for Nano Science and Technology, KS Rangasamy College of Technology,Tiruchengode, Tamil Nadu E-mail: [email protected]

ABSTRACT In this present work, for the first time, new composite electrodes made from water suspended Graphene - Draped MnO2 were synthesized using a reflux method to increase the energy and power densities. Initially, water suspended Graphene (WSG) - Draped MnO2 at WSG draped different mass ratio. The implanted surfaces were characterized by SEM, AFM, XRD, Raman spectroscopy. Electrochemical performances of these supercapacitors were studied using cyclicvoltammetry, cyclic tester and electrochemical impedance spectroscopy (EIS). Supercapacitors made with water suspended Graphene- Draped MnO2 electrodes show a very large increase in energy density (more than 50%) and power density (more than 150%) compared to the supercapacitors made with undoped electrodes. Keywords: Water Suspended Graphene, MnO2, SEM, Raman Spectroscopy, EIS, Cyclic Voltammetry and Cell Tester.

INTRODUCTION The ever worsening energy reduction and global warming issues call for not only urgent development of clean alternative energies and emission control of global warming gases, but also more advanced energy storage and management devices. [1]. Supercapacitors or electrochemical capacitors have attracted considerable attention in recent years because they can provide immediately a higher power density than batteries and higher energy density than conventional dielectric capacitors. [2–3] Research into supercapacitors is presently divided into two main areas that are based primarily on their mechanism of energy storage, i.e., an electrostatic attraction as in electrical double layer capacitors (EDLCs) and pseuodocapacitors originated from quick faradic charge transfer reactions similar to processes proceeding in batteries. [4] Supercapacitors are considered as a promising candidate for energy storage due to high power performance, long cycle life, and low maintenance cost [5]. To develop the potential of graphene–MnO2 nano materials for supercapacitors, the difficult challenge to overcome in the fabrication and application is to prevent the graphene nano sheets from restacking during assembly and cycling operation. In this article, three difference mass ratio Water suspended graphene (WSG) – Draped MnO2 composite were synthesized by a facile and effective chemical reflux method. The synthetic WSG – Draped MnO2 composite have a uniform surface distribution and large coverage of MnO2 nanoparticles onto graphene, WSG–Draped MnO2 composite have a high specific capacitance of 324 Fg–1 the morphology and crystal structure of the composites were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Atomic V. Rajendran, P. Prabu and K.E. Geckeler (eds.) Application of Nanostructured Materials for Energy and Environmental Technology, pp. 271–274 (2015)

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forced microscopy (AFM), respectively. The graphene morphology and crystal structure investigated by XRD and Raman spectroscopy.

EXPERIMENTAL PROCEDURE Synthesis of Graphene Pure graphite rods were used as electrodes and poly (Sodium diphenyl amine sulphonate) (PSDS) was used as an electrolyte. The electrochemical exfoliation method was employed using potentiostatic technique to synthesise high-purity graphene. 0.01 M PSDS electrolyte solution was prepared by dissolving the de-ionized water. Two graphite rods were inserted into a beaker filled with an electrolyte solution, and the two rods were separated by a distance of 2 ± 0.1 cm. A constant dc current potential of 6.2 V was applied between two electrodes. During the electrolysis, the anode was corroded gradually to form a black precipitate in the beaker after 20 min. The obtained dispersion was centrifuged at 10,000 rpm to remove the lighter particles. The supernatant was decanted and then washed with deionized (DI) water and subsequently with ethanol and then finally dried at 353 K for one day to obtain graphene oxide powder. The obtained powder was reduced by hydrazine hydrate and then, dried in an air oven at 353 K to obtain graphene sample [3]. Water Suspended Graphene (WSG) – Draped MnO2 by Reflux Method 10 mg WSG poured in 200 ml of 0.03 M KMnO4 solution in a round –bottomed flask. This mixture was reflux at 900 C with sustained magnetic stirring for 14 h. Obtained mixture were washed with deionised water for several time to remove the residual KMnO4 and finally washed with diluted HCl acid. The obtained WSG-MnO2 was dried in hot air oven at 700 C. Synthesis of different mass ratio of WSG (30 mg and 50 mg) in 200 ml of 0.03M KMnO4 above method. Fabrication of Symmetry Electrode Button Cell WSG-Draped MnO2 with composite poly vinyl difluoride (PVDF) 95:5 weight ratio in solvent Nmethyl 2-pyrolydine and mixed well. This mixed was coated on copper and stainless plate. This two plate dried in hot air oven at 700 C in 1h. This two electrode fabricate in button cell (2032) using polypropylene separator and 1M Na2SO4 electrolyte. RESULT AND DISCUSSION Structure Characterizations Figure 1 shows XRD patterns of graphene sheets, and WSG-Draped MnO2 at WSG- draped different mass ratio. After the chemical reduction of GO, a broad peak around 25.26° could be seen for graphene (Figure 1a). This peak is due to the deep reduction of GO, indicating that most oxygen functional groups had been removed. The GW-MnO2 nanocomposites show an XRD pattern (Figure 1b, 1c and 1d), significant XRD peaks were recorded at 2θ = 12.3, 24.3, 36.6, and 65.7°, and could be well-assigned to the (001), (002), (100), and (110) planes of birnessite-type MnO2 of MnO2 nanospheres [3] suggesting that the self-assembly process with a low fraction of graphene does not affect the crystal structure of MnO2 nano spheres. Figure 2 shows FTIR spectra of WSG-Draped different mass ratio in MnO2 (Figure 2a,b,c), the absorption band at 519 cm−1 is assigned to the Mn-O-Mn stretching vibration; the band at 3420 cm– 1 corresponds to the O−H stretching vibration of water molecule and OH− in the lattice; the band at

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273

1627 cm−1 derives from the O−H bending vibration of adsorbed water molecules. [6] The morphology and structure of honeycomb MnO2 nanospheres, graphene sheets, and GW-MnO2 nanocomposites were elucidated by SEM and AFM observations (Figure 3). As 3(a) SEM image for Water Suspended Graphene (WSG),3(b),(c)and (d) at different mass ratio WSG-Draped in MnO2 (10, 20 and 30 mg) respectively.

Fig. 1: XRD Spectra of As-Prepared WSG-Draped Different Mass Ratio in MnO2

Fig. 3: SEM Image 3a) for Water Suspended Graphene

Fig. 2: FTIR Spectra of As-Prepared WSGDraped Different Mass Ratio in MnO2

Fig. 4: (a) CV Curves of WSG-MnO2 Nanocomposites Scan Rates of 10 mVs–1 at Different Mass Ratio in 1 M Na2SO4 Electrolyte

Electrochemical Studies The capacitive performances of materials were evaluated by cyclic voltammetry (CV) and Cell Tester in 1 M Na2SO4 aqueous solution. CV is a suitable tool to characterize the capacitive behavior of electrode materials [7]. As seen from Figure 4a, WSG-MnO2 have a rectangle-shaped and symmetric CV curve at a low scan rate of 10 mVs–1, indicating their perfect capacitive behavior at low scan rate of 10 mVs–1, the Na+ ion can easily diffuse into almost all available space of the hybrid material, leading to a sufficient insertion reaction and showing almost perfect capacitive behavior. However, increasing the scan rate has a remarkable impact on the diffusion of Na+ into the hybrid material. At a

274


high scan rate of 100 mVs–1, the Na+ ion can only approach the outer surface of the hybrid material and the material located in the deep space has little contribution to the electrochemical capacitive behavior, leading to the deviation from the ideal rectangular shape of the CV curve. Figure (a) for CV curve for 10 mv/s at different mass ratio of WSG-draped in MnO2, curve (a), (b) and (c) for 10,20 and 30mg WSG-draped in MnO2. There is 120,160 and 348 Fg–1 at scan rate 10mvs–1 respectively.

CONCLUSIONS In summary, we have first synthesized the novel WSG-Draped in MnO2 nanocomposites by selfassembly of reflux method for supercapacitors. Moreover, the WSG-MnO2 nanocomposites exhibited enhanced capacitive performance as high as 348 F/g, which is attributed to the synergistic effect between the pesudocapacitance of MnO2 nanospheres and good electrical conductivity of graphene sheets. The WSG-MnO2 nanocomposites retained about 82.4% of the original capacitance after 500 cycles of charge−discharge. These results demonstrate exciting potentials of the WSG-MnO2 nanocomposites for high performance supercapacitors. REFERENCES [1] Wang, H., Casalongue, H.S., Liang, Y. and Dai, H., J. Am. Chem. Soc. (2010), 132, 7472. [2] Zhang, D., Zhang, X., Chen, Y., Yu, P., Wang, C. and Ma, Y., J. Power Sources, (2011), 196, 5990−5996. [3] Selvam, M., Sakthipandi, K., Suriyaprabha, R., Saminathan, K. and Rajendran, V., Bull. Mater. Sci. (2013) 36 (7), 1315–1321. [4] Simon, P. and Gogotsi, Y., Nat. Mater, (2008), 7, 845–854. [5] Burke, A., J. Power Sources (2000), 91, 37–50. [6] Chen, S., Zhu, J., Wu, X. and Han, Q., ACS Nan (2010), 4, 2822−2830. [7] Si, Y. and Samulski, E.T., Nano Lett. (2008), 8, 6.

Author Index Abe, Toshiyuki Adam, S. Agalya, P. Alameh, Kamal Ali, Asgar Ananth, T. Vijay Anantharaju, K.S. Anju, K.R. Arulesan, V. Arulraj, A. Arya, Sandeep Bagade, Chaitali S. Balaji, R. Baral, Ayonbala Barathan, S. Basavaraj, R.B. Bhabhina, N.M. Bhagat, Madhulika Bhajantri, Rajashekhar Bhosale, P.N. Bhuvanasundari, S.

16 121 167 11 25 227 65 149 245 207 49 173 167 59 105 211 145 49 255 215, 173 167

Chen, Zuliang Chinnaiyah, Sripan Chitra, M.

237 55 131

D’Aguanno, Bruno Danasekaran, T. Das, Dipti P. Das, J. Dattatraya, S.S. David, E.

15 39 29, 59 29 95 121

Devarayan, Kesavan Dey, Ratan Kumar Dubal, Deepak P. Dubey, R.S. Dumasiya, Ajay

153 219 111, 233 81 69

Eraiah, B. Ernest, Suhashini

211 239

Faik, Abdessamad Fatima, M.J. Jabeen

15 141

Ganesamoorthy, Ramasamy Ganesan, R. Gangadevi, K. Geetha, D. Ghanwat, V.B. Ghosh, Malay Kumar Giribabu, K. Gomez-Romero, Pedro Gopal, K. Gothe, S.D. Govindaraj, R. Gupta, Sahil

157, 163 55 73 85 173, 215 59 39 7, 111, 233 43 89 181 49

Handy, Richard

259

Jagadale, S.K. Jayaseelan, Santhana Sivabalan Jeganathan, Kulandaivel Jenkins, David Joshi, P.S. Jothivenkatachalam, Kandasamy

215 153 193 259 89 193

276

Author Index

Kalainathan, S. Kalaivani, J. Kaler, Karan V.I.S. Kamruzzaman, M. Karthik, Mani Karthikeyan, S. Karuppuchamy, S. Kassiba, Abdel Hadi Khan, Saleem Khasimsaheb, B. Khot, K.V. Kim, Byoung-Suhk Kirubavathi, K. Konathala, L.N. Sivakumar Kumar, A. Senthil Kumar, J.B. Prasanna Kumar, M. Senthil Kumar, R. Dhilip Kumar, Rahul Kumar, S. Praveen Kumar, Umesh Kumara, K.N. Shravana Lakshmi, V. Venkata Lingaraju, K. López-López, Josu

81 77 21 125 15 43 189 19 49 115 173, 215 153 135 25 167 65 227 189 219 39 25 249 249 211 15

Megharaj, Mallavarapu Mishra, B.K. Mohan, D. Bharathi Mohana, V. Mukhopadhyay, S. Munusamy, S. Murugan, P.R. Senthil Muthamizh, S. Mylarappa, M. Nagabhushana, H. Nagai, Keiji Nagar, Bhawna Nagaswarupa, H.P. Naidu, Ravi Naik, Ishwar Naik, Jagadeesh Naik, Lohit Nandeesh, L.S. Narayanan, V. Neelakandeswari, N. Neeleshwar, S. Nijisha, P. Niveditha, C.V. Nur-E-Alam, Mohammad Oberoi, Priyanka

Maaza, M. Madale, S.G. Magesh, M. Mageswari, S. Mahanwar, Prakash A. Mahesh, K.R. Vishnu Maiyalagan, T. Mane, R.K. Mane, R.M. Mane, Rahul M. Manigandan, R. Maurya, Chandra B.

3 89 181 43 197 249 43 215 215 173 39 197

Padamanaban, A. Pal, Anil Kumar Pandian, M. Senthil Panigrahi, B.K. Panina, Larissa Patel, Shilpa Patil, Pallavi B. Patil, B.S. Pérez, Mónica Podili, Surekha Pragasam

237 29 185, 187 33 201 39 227 39 249 65, 211 16 111 249 237 255 255 255 249 39 131 115 145 141 11 197 39 185, 187 181, 201 115 259 177 173 255 10 85 255

Author Index

Prasad, B. Daruka Prasad, T.N.V.K.V. Prashantha, S.C.

65, 211 121 65

Radhika, T. Raghavender, M. Raghavendra, N. Rajanaika, H. Rajasekaran, N. Rajathi, S. Rajendran, V. Rajni, K.S. Rajput, Shayana Ramachandran, K. Ramasamy, P. Ramasamy, V. Rambabu, K. Ramesh, P.S. Ramgopal, G. Rani, A. Amala Rathod, Sunil Renukadevi, K. Rivas, Bernabé L. Rokesh, Karuppannan Rosenberg, Victor

149 63 249 211 131 135 271 223 49 73, 77 181, 201 33 101 85 65 239 255 77 10 193 11

Sagar, S.G. Sakthivel, Pachagoundar Salah, Nasih Hma Samal, Alaka Saminathan, K. Sánchez, Julio Sangeeta, M.J. Santhosh, N. Saran, Sandeep Saravanan, S. Sathiyan, Govindasamy Schneider, J. Selvam, M.

95 157, 163 259 29 271 10 95 181 25 81 157, 163 125 271

277

Selvamurugan, M. Selvaraju, K. Senguttuvan, G. Shah, N.M. Shanmugam, M. Shelke, Manjusha Shinde, D.B. Siddeswara, D.M.K. Sindhu, S. Singh, Gajendra Prasad Singh, Neha Singhal, Nikita Siva, P. Sivakumar, E.K.T. Sivakumar, G. Sivakumar, V. Sridhar, D. Srinivasan, R. Srivastava, Vivek Subashchandrabose, Suresh Ramraj Subramanian, B. Subramaniyam, Vidhyasri Sundarrajan, M. Supraja, N. Suresh, C. Suresh, G. Suresh, R. Susmitha, K. Sutrave, D.S.

189 135 207 69 105 20 215 249 141, 145 219 219 25 271 157, 163 105 207 227 73, 77 265 237 207 237 245 121 65 33 39 63 89

Thakur, Bijendra Thangamuthu, Rangasamy Thavamani, Palanisami Thyla, P.R. Tiruvenkadam, N. Tripathy, Sukanta K.

177 157, 163 237 227 227 177

Upadhyay, Praveenkumar Urbano, Bruno F.

265 10

278

Author Index

Uthayarani, K.

131

Vasiliev, Mikhail Veeramani, S. Velu, S. Venkateswaran, R. Vijayakumar, P.

11 207 101 167 201

Vinoth, M. Viswanath, Annamraju Kasi

271 55

Yadav, H.J. Amith Yamaguchi, Takeo

211 17

Zapien, J.A.

125