Size-tunable leaf-like copper oxide modified by graphene nanosheets was synthesized by a facile hydrothermal method. Stirring temperature control during synthesis was found to be important in effectively controlling the size of CuO nanoparticles, with smaller size CuO nanoparticles produced by increasing the stirring temperature. The as-prepared nanocomposites were characterized by XRD, TEM, and nitrogen adsorption-desorption. The nanocomposites exhibited better catalytic activity than pure CuO toward the degradation of rhodamine B in the presence of H2O2 under visible light irradiation. The catalytic performance was improved with decreasing particle size of the nanocomposites, which was attributed to the increased in the rate of interelectron transfer at the interface. (C) 2014 Elsevier Ltd. All rights reserved.