Synthesis of ultrafine copper particles by complex-reduction-extraction method
(School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China)
Abstract: A novel chemical process for producing well-defined copper particles with satisfied anti-oxidation property was described. The resultant particles were characterized by X-ray diffractometry and scanning electron microscopy. The results show that well-dispersed nano-copper particles with 70 nm in diameter are obtained from the water/organic solution containing 0.2 mol/L Cu2+ ion, with ammonia as ligand and ascorbic acid as reductant. In this process, the formation of copper-ligands in aqueous solution causes initial copper ions concentration very low, which is not only good to obtain homogeneous initial reaction solution, but also slower the initially drastic nucleation reaction rate. This makes the process more convenient for delaying the nuclei processes and for controlling the ultimate copper particles size. In addition, oleic acid acts as both a phase-transfer agent and a particle protector coordinating their carboxyl end groups on the new generated copper particles surface, the carbon tails of the oleic acids are pointed outwards from the surface of the synthesized particles. This organic film also seems to play an important role to prevent the new generated copper particles from oxidation.
Key words: copper nanoparticles; copper ligands; complex; extraction; reduction