Polyol synthesis of Cu2O nanoparticles: use of chloride to promote the formation of a cubic morphology

Abstract

We have employed the polyol method to synthesize copper(I) oxide (Cu₂O) nanostructures with well-defined shapes and in large quantities. Transmission electron microscopy and X-ray powder diffraction studies show that polycrystalline colloidal spheres could be prepared in high yields by simply reducing copper nitrate with ethylene glycol heated to 140 °C in the presence of poly(vinyl pyrrolidone). When a small amount of sodium chloride was introduced, single-crystal nanocubes were obtained. In this case, chloride seems to play a pivotal role in controlling the formation of seeds and the growth rates of various crystallographic planes to shape the Cu₂O nanostructures into nanocubes. Based on the structural analysis of samples obtained at different growth times, we also proposed a plausible mechanism to account for the formation of these two distinctive morphologies under different conditions.