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 20 min. Noteworthy, Cu2O 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 Cu2+ 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.