Preparation of Monodispersed Cu Nanoparticles by Microwave-Assisted Alcohol Reduction

Copper (Cu) nanoparticles were prepared via a microwave-assisted alcohol reduction process. We have succeeded in selectively preparing monodispersed Cu nanoparticles with or without surface plasmon absorption. Monodispersed Cu nanoparticles with average sizes of 5-6 nm (with the surface plasmon absorption) and 2-3 nm (without the surface plasmon absorption) were prepared using copper(II) octanoate and copper(II) myristate, respectively, as the copper precursors by reduction with alcohols under microwave-heating at 443 K for 20min. Noteworthy, Cu 2 O and CuO were not observed in the electron diffraction patterns of the prepared Cu nanoparticles, demonstrating chemical stability of the nanoparticles against oxidation in air. When using a long-chain carboxylate as an organic moiety bearing a short alkyl chain (copper(II) octanoate), the rate of the reduction was faster than long one (copper(II) myristate). The activation energies for the reduction of Cu 2+ using copper(II) octanoate and copper(II) myristate were estimated to be 115 and 124 kJ mol -1 , respectively. We have shown that the length of the alkyl chain contained in the copper precursors, heating temperature, and microwave-irradiation time are important for rapidly preparing monodispersed Cu nanoparticles.