Advanced Materials Research Vol. 829 (2014) pp 93-99 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.829.93
Synthesis and characterizations of highly efficient Copper nano particles and their use in ultra fast catalytic degradation of organic Dyes Syed Tufail Hussain Sherazi*, a Razium Ali Soomrob, Sirajuddinc, Najma Memond National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, 76080Pakistan a
[email protected], b
[email protected], c
[email protected], d
[email protected]
Keywords: Copper nanoparticles, sodium dodecyl sulfate, Methylene Blue, Rose Bengal, Reductive degradation.
Abstract The present study describes synthesis of highly active copper nano particles by a green and economically viable approach. The highly stable colloidal dispersions of copper nano particles ( Cu NPs) were prepared via modified sodium borohydride reduction route with controlled morphology in a aqueous phase using anionic surfactant, Sodium dodecyl sulfate (SDS), as directing agent and vitamin-C as a Quenching agent. The characterization studies like optimization of various parameters for preparation of nano scale copper NPs, surface binding interactions, size and morphology of the fabricated Cu NPs were carried out using UV-Visible Spectroscopy, Fourier Transform Infrared (FTIR) Spectroscopy, X-Ray Diffraction (XRD) Analysis and Tunneling Electron Microscopy(TEM). The results of study revealed that CuNPs has ultra fast catalytic activity for the degradation of some frequently used organic dyes such as methylene blue (MB) and rose bengal (RB). 1.
Introduction During last two decades considerable attention is focused on nano-materials research because of their unique properties, which are entirely different from the corresponding bulk materials. [1] Various types of nanoparticles are used for variety of applications; however metallic nanoparticles are of great interest of due to their excellent chemical, physical, and catalytic properties [2]. Among other metal nanoparticles, copper nanoparticles are of substantial interest due to their high catalytic, optical and electrical properties [2-4]. Additional advantages with copper is the low cost ,easy availability, and can serves as a heterogeneous recyclable catalyst in various types of pollution control study especially waste water pollution[5]. Regarding the waste water pollution colored effluents released from textile, paper and cosmetic industries are one of the major sources of hazardous compounds responsible for inhibitory effect on aquatic ecosystems [6-8]. There are several methods reported in the literature for the synthesis of copper nanoparticles including radiation method [9 ], microemuslion method [10], thermal decomposition method [11], laser ablation method[12 19], and aqueous chemical reduction method [13]. Among all mentioned methods, aqueous reduction route is most widely selected because of its advantages like simple, economic and provides ease of control over size and distribution of particles by controlling reaction parameters like concentration of precursor salt, capping agent and pH of solution [14,15]. In the present study stable copper nanoparticles with narrow size and homogenous distribution were synthesized via surfactant assisted wet chemical reduction method using sodium borohydride as a reducing agent, sodium dodecyl sulfate as a capping agent and ascorbic acid All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 151.250.96.7-28/10/13,21:21:14)
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(natural vitamin C) as an anti-oxidant. These nanoparticles were further employed as a heterogeneous catalyst for ultra fast reductive degradation of model dyes methylene blue (MB), and rose bangle (RB), which to the best of our knowledge, have not been addressed before. 2.
Materials and methods
All chemicals used were of analytical grade and used without further purification. CuCl2.5H2O, Sodium dodecyl sulphate (SDS), and vitamin C were purchased from E. Merck and NaBH4, NaOH, HCl, from Sigma–Aldrich. Copper nanoparticles were synthesized via surfactant assisted aqueous reduction route, by taking 2.0 ml of 2.0M Sodium dodecyl sulphate (SDS) in deionized water to obtain transparent solution. In the next step 0.2ml of 0.2 M ascorbic acid was introduced to previous solution , followed by 0.2ml of 0.06M copper (II) chloride pent hydrate salt (CuCl2 • 5H2O). The mixture was diluted to with de ionized water to volume of 18 ml in deionized water. In the end 0.6ml of 0.02M sodium borohydride (NaBH4) was added to initiate the reduction process. The color of the mixture changed from blue to reddish brown, which indicated the formation of Cu NPs. The resulting NPs were characterized by absorption spectra using UV– Visible spectroscopy (Lambda 35 of PerkinElmer).The Fourier transform infrared spectroscopy (FTIR) (Nicolet 5700 of Thermo) analysis was performed after incorporating the dried (under nitrogen) sample in solid state KBr disc, to confirm surface interaction between Cu NPs and surfactant molecules. Size and shape of the synthesized nanoparticles were characterized using Transmission electron micrographs (TEM) (Jeol JEM 1200 EX MKI) and X-ray diffraction (XRD) (D-8 of Bruker) was used for the phase confirmation and crystalline patterns of Cu NPs. 2.1
Catalytic performance of Cu NPs
The catalytic performance of surfactant capped Cu NPs was investigated for reductive degradation of methylene blue (MB), and rose bangle (RB). In a representative catalytic reductive degradation experiment, 0.1mg of Cu NPs deposited on prior weighted broken pieces of glass cover slip was introduced to 100µM concentration of an aqueous dye solution along with 10 mM NaBH4 in quartz cells and then the mixture was allowed to react at room temperature and under atmospheric pressure. The catalytic reduction of these dyes was monitored by the recording UV– Vis spectral changes with time. 3. 3.1
Results and discussions UV-visible spectroscopy
UV-visible spectroscopy was carried out to investigate the effect of important parameters like concentration of surfactant, and concentration of precursor salt. UV-visible spectra of Cu NPs recorded a blue shift in the excitonic absorption peak from 567-569 nm when the amount of surfactant (SDS) was varied in the range of 0.4-0.6 ml, as shown in Fig.1. Further increase in amount to 0.7 ml generated a red shift from 565 to 569nm indicating growth of copper nanoparticles. Similarly Uv-Vis Spectra profile for the shift in SPR position with variation in the amount of precursor salt in the range from 0.05-0.8ml was recorded as shown in Fig.2, a blue shift in the range from 579 to 569nm was observed with variation in amount from 0.2 to 0.3ml. However with higher amount of precursor ions to 0.4, red shift was observed from 569-577 nm which is the result of particle growth.
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Fig.1. UV-Vis spectra for the effect of surfactant precursor salt concentration on SPR of Cu NPs.
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Fig.2. UV–Vis spectra for the effect of concentration on SPR of Cu NPs.
Fourier transform infrared (FTIR) spectroscopy
Surface interaction between synthesized copper nanoparticles and surfactant were studied using FTIR spectroscopy. Fig.3, shows FTIR of SDS capped Copper NPs. The major bands of pure SDS can be divided into two regions, two absorption bands in the range of 2950–2850 cm–1, attributed to aliphatic group (tail group) and another band at 1226 cm–1, attributed to sulfonic acid (head group) [18]. Shift towards higher wave number in the absorption band of the sulfonic head group from 1226 cm–1 to 1234 cm–1 in the FTIR of SDS capped Cu NPs confirms the surface capping of copper nanoparticles. SDS-Cu NPs
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Fig.3. FTIR spectra of SDS capped Cu NPs.
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Tunneling Electron Microscopy (TEM)
Fig.4 is a representative TEM image of Cu NPs synthesized in an aqueous medium via a surfactant assisted chemical reduction route. This clearly shows that most of synthesized Cu NPs are spherical in shape having diameter in the range of 8 to 25 nm with an average of 15 nm. In some regions, agglomeration of small nanoparticles was observed which might due to interaction of surfactant chain with each.
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Fig.4. TEM images of SDS capped Cu NPs mounted on carbon coated Cu grids. 3.4
X-ray powdered diffraction (XRD)
Cu NPs
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XRD analysis was performed to explore the structure and morphology of SDS capped Cu NPs. For this, XRD diffractogram was recorded in a range of 20-80° 2θ as shown in Fig.5. Diffraction data inferred to the formation of pure crystalline phase Cu metal nanoparticles with face centered cubic (FCC) crystal structure having characteristic diffraction peaks at peaks (111), (200) and (220).The data obtained is in strong co-relation with previous reports concerning Cu nanoparticles [19, 20].
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Fig.5. XRD spectra of Cu NPs. 3.5
Catalytic activity
The progress of the catalytic degradation of methylene blue (MB), and rose bangle (RB) dye can be easily monitored by the decrease in the maximum absorbance wavelength (665 nm and 550nm respectively). Fig.6 (a, b), shows the UV–Vis spectra of the MB and RB (100µm) with NaBH4 (10mM) in absence of Cu NPs respectively. Noticeably very small reduction was observed with the passage of time. However, the reductive degradation observed after addition of Cu NPs catalyst, in the presence of NaBH4, as shown in Fig.7(a, b), suggest the complete reductive degradation of the MB and RB dye within 12 sec and 16 sec respectively. This result indicates that the as-prepared copper nano catalyst shows high activity in degradation of organic dyes which highlights the exceptional catalytic potential of the Cu NPs.
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Fig.6. (a) Absorption spectra of 100µM of MB + 500µL of 100 µM NaBH4 (b) Reduction of 100 µM of MB+ 500µL of 10mM NaBH4 + 0.1mg Cu NPs.
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Fig.7. (a) Absorption spectra of 100µM of RB + 500µL of 100 µM NaBH4 (b) Reduction of 100 µM of RB+ 500µL of 10mM NaBH4 + 0.1mg Cu NPs 4.
Conclusion
Copper nanoparticles were successfully prepared via surfactant assisted aqueous reduction route which is green, cheap and very simple as compared to conventional reported methods. The stable nanoparticles were characterized using analytical techniques such as UV-visible spectroscopy (UV-VIS), Fourier transform infrared (FTIR) spectroscopy, tunneling electron microscopy (TEM), and X-ray diffractometery (XRD). Synthesis parameters like concentration of capping material, amount of precursor salt, and pH were optimized using UV-Vis spectrometer. The synthesized nanoparticles were applied as a heterogeneous catalyst for reductive degradation of organic dyes like methylene blue and rose bangal and 100% complete reductive degradation was achieved with in few seconds. The obtained results suggested that copper nanoparticles has a strong potential for fast dye degradation technologies.
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