Synthesis of copper nanorods by aqueous solution

Synthesis of copper nanorods by aqueous solution method without heating external Dedi Mardiansyah, Kuwat Triyana, Harini Sosiati, and Harsojo Citation: AIP Conference Proceedings 1755, 150019 (2016); doi: 10.1063/1.4958592 View online: http://dx.doi.org/10.1063/1.4958592 View Table of Contents: http://scitation.aip.org/content/aip/proceeding/aipcp/1755?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Excitation temperature of a solution plasma during nanoparticle synthesis J. Appl. Phys. 116, 083301 (2014); 10.1063/1.4894156 Synthesis and characterization of Cu, Fe co-doped ZnO nano-particles synthesized by solution combustion method AIP Conf. Proc. 1536, 173 (2013); 10.1063/1.4810156 Growth And Synthesis Of ZnO Nanorod Arrays By A Chemical Solution Method AIP Conf. Proc. 1325, 79 (2010); 10.1063/1.4757194 X-ray photoelectron spectroscopy characterization of aminosilane anchored to ZnO nanorod arrays grown by an aqueous solution method with microwave-assisted heating J. Vac. Sci. Technol. B 27, 1834 (2009); 10.1116/1.3155824 Simulation of preferential Cu 2+ solvation in aqueous ammonia solution by means of Monte Carlo method including three-body correction terms J. Chem. Phys. 112, 4212 (2000); 10.1063/1.480966

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Synthesis of Copper Nanorods by Aqueous Solution Method without Heating External Dedi Mardiansyah1,3,a), Kuwat Triyana1,2, Harini Sosiati2, and Harsojo1,2,b) 1

Departement of Physics, Faculty of Mathematics and Natural Sciences Universitas Gadjah Mada, Sekip Utara BLS.21 Yogyakarta, 55281 Indonesia 2 Nanomaterials Research Group, Integrated Research and Testing Laboratory (LPPT), Universitas Gadjah Mada, Jl. Kaliurang KM.4 Sekip Utara, Yogyakarta, 55281 Indonesia 3 Departement of Physics Education, Faculty of Teaching and Education Universitas Pasir Pengaraian, Riau, Indonesia a)

[email protected] Corresponding author: [email protected]

b)

INTRODUCTION Abstract. So far, synthesizing Cu nanorods (CuNRs) are complicated, expensive, and needs a long time. In this study, We report a simple way to synthesized CuNRs by the aqueous solution method without external heating. Instead of external heating, we used internal heating from the exothermic reaction of NaOH and water. Copper (II) nitrate trihydrate Cu (NO3)2.3H2O, sodium hydroxide (NaOH), ethylenediamine (EDA), and hydrazine (N2H4) were used in our work. The morphology and formation structure of CuNRs have been investigated using Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy (SEM-EDXS), and X-ray Diffraction (XRD). The SEM analysis confirmed the formation of CuNRs with a diameter of 200-300 nm and length of 3-7 μm.

Recently, the synthesis of copper compounds has attracted the attention of researchers and industries due to its various potential applications. One of them is the synthesis of one-dimensional (1D) nanomaterials of copper compounds such as Cu nanowires (CuNWs) or CuNRs [1-3]. The CuNRs have prospective applications in many fields such as electronics, optics, medicine, pharmacy and renewable energy [4]. The CuNRs have also been used as the main materials for fabricating a transparent electrode of indium tin oxide (ITO) [5-7]. To date, some methods have been developed in the process of synthesis of CuNWs or CuNRs. The aim is how to get a simple and low-cost method, but capable of producing homogeneous CuNWs or CuNRs. Principally, the methods are by reducing Cu ions in the solution, and then providing a capping agent for the growth of 1-dimensional Cu [8]. The process of reduction and providing capping agent are the main key to synthesizing CuNRs. Zeng and co-workers have developed a simple method for the synthesis CuNWs or CuNRs [9]. In their work, Zeng and co-workers synthesized 1-dimensional Cu by using Cu (NO3)2, NaOH, EDA, and hydrazine. EDA was used as a capping agent and hydrazine as a reducing agent. The product of Cu nanowires was 90–120 nm in diameter and 40–50 μm in length. Rathmell et al. modified Zeng's approach with scaled up the reaction by 200 times to demonstrate the potential for large-scale production [10]. The Cu nanowires were 90 ± 10 nm in diameter and 10 ± 3 μm in length. Ye et al. found the size and shape of the Cu nanowires were controllable through adjustment of the molar ratio of Cu (NO3)2, N2H4, and EDA [11]. However, CuNRs synthesis without external heating has not been discussed. In this work, we performed the synthesis of CuNRs without external heating process. The addition of heating in solution is necessary to make the solution become more homogeneously mixed. Besides, the heating is also necessary for the reduction process, and the capping process in order to have optimum conditions. In this work, CuNRs have been successfully synthesized by an addition of internal heating from the Advances of Science and Technology for Society AIP Conf. Proc. 1755, 150019-1–150019-4; doi: 10.1063/1.4958592 Published by AIP Publishing. 978-0-7354-1413-6/$30.00

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reaction of NaOH and water. The NaOH and water produced an exothermic reaction. The resulting heat could reach 100 ºC. The optimum heating is at 60 °C [9]. The CuNRs production is highly dependent on the reduction and capping process [12]. The reduction process is a process of reduction reaction of Cu ions to a neutral Cu. The capping process is the process to grow one dimension material by the capping of nanoparticles. The formation of high aspect ratio CuNRs will be maximized by giving heat in the process of capping and reducing.

EXPERIMENTAL In this study, we used copper (II) nitrate trihydrate (Cu (NO3)2.3H2O) (99%, Merck), sodium hydroxide (NaOH, 99% Merck), ethylenediamine (EDA, Merck) and hydrazine (N2H4, Merck). The steps of Cu nanorods synthesis were: (100 mL, 15 M) of NaOH was mixed (20 mL, 0.2 M) of Cu (NO3)2.3H2O in the 150-mL reaction flask. After 2 min, 0.5-mL EDA and 0.25-mL hydrazine (35 wt %) were added to the solution. All of these processes were done under stirring at 60 rpm for 35 min. The color would change from blue to reddish brown. The change of color indicated that CuNRs had been formed. The CuNRs were washed five times by centrifuged with alcohol at 6000 rpm for 10 min. The sonication was carried out for 30 min to parse agglomeration [4]. Finally, the CuNRs were stored in ethanol for the next process. The morphology and size of CuNRs were characterized by Scanning Electron Microscopy and Electron Dispersive Spectroscopy to study the distribution of elements in CuNRs (SEM-EDS, from JEOL JSM-6510). The CuNRs crystal structure was analyzed by XRD (Shimadzu XRD-6000).

RESULTS AND DISCUSSION Chemical reactions were optimized at the certain level of temperature. In this study, the heat was generated by the reaction of sodium hydroxide and water in the synthesis process without the provision of external heating, which could be described as Eq. 1.

NaOH( s ) H 2O(l ) o Na OH H 2O Heat

(1)

(b)

(a)

FIGURE 1. (a). The effect of stirring on the temperature. (b). before and after the reaction

Stirring can influence temperature in solution due to its role as a facilitator of the reaction between sodium hydroxide and water. Figure 1 shows the slope of the lines which describe the decreasing of temperature versus time. The faster the stirring process, the faster the heat occurs. Without stirring, the temperature tends to decrease constantly. when the stirring 1100 rpm given to the solution, the temperature would reach the maximum level of 100 qC, but then the decreasing process becomes faster. In this study, the stirring speed of 60 rpm with a temperature of 60 ºC was selected due to relatively constant in decreasing of temperature which is more suitable for the synthesis process. In the synthesis process, Changing of color from blue to reddish was investigated. The blue color changed into reddish brown after 15 min. The blue color indicates the Cu2+ ions and the reddish brown color is an indication of the CuNRs formation (Fig. 1b).


FIGURE 2. XRD pattern of CuNRs.

Figure 2 shows the XRD diffraction peak of CuNRs. The x-ray diffraction (λ = 1.54060 Å) showed diffraction peaks at the angles 2θ of 42.52 °, 49.68 °, 60.94 ° and 73.43 °. The value of the diffraction angle was in accordance with the CuNRs crystal miller index of (111), (200), (220) and (311) as crystalline planes of the face center cubic (fcc) Cu (JCPDS 04-0836). The calculated lattice constants according to the spacing distance dhkl of the {111} planes and the equation: dhkl2 = a2/(h2+k2+l2) was 3.6795 Å. This calculated lattice constant was very close to the literature value of 3.615 Å [3].

O K Al K Cu K Total

(a)

Wt % 1.58 2.07 96.35 100.00

Σ 0.06 0.06 0.53

(b)

FIGURE 3. (a). SEM image of CuNRs, (b). EDXS photograph is showing elements distributions in the CuNRs.

The morphology of CuNRs has been characterized by Scanning Electron Microscope (SEM). Figure 3 shows a scanning electron microscope image of CuNRs. The average diameters of CuNRs were 200 to 300 nm with lengths of 3 to 7 μm. The diameter and length of CuNRs could be controlled by changing the molar ratio of the solution [12]. The composition of Cu (NO3)2.3H2O above 0.2 M affects the diameter of CuNRs becomes larger. The formation of nanorods or nanowire was also determined by the shape of the nanoparticles, spherical nanoparticles with small sizes could more easily being into nanorods. The large nanoparticle size required great energy to form nanorods. Fig. 3a shows both CuNRs and the Cu nanoparticles, Cu nanoparticles were formed because the capping process has not perfect yet. EDXS spectrum shows the distribution of elements in CuNRs (Fig. 3b). The relative concentrations of Cu, Al, and oxygen elements were around 96.35%, 2.67%, and 0.25%, respectively. The distribution of Al was present due to the use of an aluminum grid when the sample prepared.


CONCLUSION The CuNRs have been successfully synthesized by a simple aqueous solution method with utilizing the heat from the reaction of sodium hydroxide and water. Temperature is an important parameter when synthesis. The temperature could affect the morphology of CuNRs. The optimal temperature of synthesis CuNRs was 60 ºC. The SEM analysis result of CuNRs was 200 to 300 nm in diameter and 3 to 7 μm in length. The EDXS and The XRD data showed the compositions and crystal structures of Cu nanorods. For the future, the next research should be the molar ratio optimization of Cu (NO3)2, N2H4, and EDA.

ACKNOWLEDGMENT This research was supported by the research grant of “International Research Collaboration and Scientific Publication, Contract No.: LPPM-UGM/998/LIT/2015” by the Directorate General of Higher Education (DIKTI), Ministry of Education and Culture, the Republic of Indonesia.

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