A potential mechanism for the formation of the nanoparticles is proposed. The photocatalytic properties of the Cr2O3 nanoparticles were investigated with respect to the degradation of methyl orange. It was found that the spherical Cr2O3 nanoparticles subjected to a heat treatment at 800 1C exhibited a higher photocatalytic activity than did the untreated nanoparticles or the nanoparticles heat treated at 400 1C. & 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.