Ultrafine narrow dispersed copper nanoparticles synthesized by a facile chemical reduction method
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Ultrafine narrow dispersed copper nanoparticles synthesized by a facile chemical reduction method O. Mondal, Department of Physics, M.U.C. Women's College, Burdwan-713104, India A. Datta, Guru Gobind Singh Indraprastha University, New Delhi-110075, India D. Chakravorty, MLS Prof's Unit, Indian Association for the Cultivation of Science, Kolkata-700032, India M. Pal, CSIR-Central Mechanical Engineering Research Institute, Durgapur-713209, India Address all correspondence to M. Pal at [email protected] (Received 19 October 2012; accepted 7 March 2013)
Abstract We have prepared stable ultrafine narrow dispersed copper nanoparticles (Cu-NPs) using a facile chemical reduction technique below room temperature (300 K), without any template. X-ray diffraction and high-resolution transmission electron microscopy studies reveal the growth of highly crystalline Cu-NPs with an average diameter of 2.2 nm. Interestingly, these Cu-NPs demonstrate both interband electronic transitions along with usual surface plasmon resonance, a unique phenomenon previously unobserved in any noble metal nanoparticles. These Cu-NPs do not get oxidized easily and could be suitable candidates for different optical devices, heat transfer liquids, and biological applications.
Copper nanoparticles (Cu-NPs) attracted much attention due to various technological applications[1–5] attributed to their unique optical, conducting, and catalytic properties.[6,7] Small metal nanoparticles exhibit the absorption of visible electromagnetic waves by the collective oscillation of conduction electrons at the surface known as surface plasmon resonance (SPR).[8] Interestingly, due to SPR, Cu-NPs exhibit enhanced nonlinear optical properties, which could be beneficial for applications in optical devices and nonlinear optical materials, such as optical switches or photochromic glasses.[9] In spite of huge application potential, the main challenge remains in the production of antioxidation Cu-NPs with narrow size distribution. To overcome these problems, the reduction of copper salt is usually performed in non-aqueous medium with low precursor concentration, having protective polymers coating and inert gas atmosphere.[10–12] Copper clusters with diameters about 4 nm have been synthesized within dendrimer templates,[13,14] and using electrochemical[15] and microemulsion technique.[16] Synthesis of Cu-NPs through a complex chemical reduction technique in the presence of nitrogen atmosphere[17] and using an oil bath at 80 °C in the presence of L-ascorbic acid[12] have also been reported. However, these groups did not observe interband electronic transition along with SPR. In this paper, we present an easier solution based chemical reduction process of synthesizing ultrafine Cu-NPs in water and ethylene glycol (EG) medium in the presence of a capping agent cetyltrimethylammonium bromide (CTAB) below room temperature (RT ∼300 K) without inert gas protection. We demonstrated that it is possible to tune the size and optical property by manipulating
the reaction t
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