A simple and rapid method has been developed to synthesize cuprous selenide (Cu2Se) nanoparticles by the reaction of selenium nanoparticles sal with copper sulfate solution containing ascorbic acid at room temperature. Cu2Se nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive X-ray analysis (EDX). The results indicated that Cu2Se nanoparticles were cubic crystal structure and spherical with the diameter about 75 nm. The ultraviolet-visible absorption spectrum (UV-vis) and cyclic voltammetry of Cu2Se nanoparticles were also investigated. The optical band gap energy of Cu2Se nanoparticles was 1.94 eV. On the basis of a series of experiments and characterizations, the formation mechanism of Cu2Se nanoparticles was discussed. (C) 2011 Elsevier Ltd. All rights reserved.