Syntheses of Cu2O and Cu Nanoparticles by Using a Polyol Method

Copper-containing nanoparticles were synthesized by using a polyol method. Ethylene glycol (EG), which is a typical polyol, was used as a reductant and a solvent. Cu(OAc)2·H2O and polyvinylpyrrolidone (PVP) were employed as a reagent and a protecting agent, respectively. The product nanoparticles obtained at each reaction stage were characterized by using transmission electron microscopic (TEM), TEM-energy dispersed X-ray spectroscopic (EDS), scanning electron microscopic (SEM), X-ray diffraction (XRD), and ultraviolet (UV)-visible (Vis) extinction spectroscopic measurements. Results showed that Cu2O particles with a mixture of various morphologies were initially formed at 175 oC. They consisted of aggregates of small nanoparticles in most cases. After further heating at 175 oC for 15 min, Cu2O particles were reduced to Cu nanoparticles rapidly. After heating at 175 oC for 60 min, monodispersed spherical Cu nanoparticles with an average diameter of about 200 nm were finally obtained. UV-Vis extinction spectra suggested that Cu2O particle solution was stable more than 10 days, whereas complete precipitation occurred for Cu nanoparticle solution after 3 days due to oxidation.