▎ 摘　　要

Using ultrasonication we succeed in a controlled incorporation of TiO2 nanoparticles on the graphene layers homogeneously in a few hours. The average size of the TiO2 nanoparticles was controlled at around 4-5 nm on the sheets without using any surfactant, which is attributed to the pyrolysis and condensation of the dissolved TiCl4 into TiO2 by ultrasonic waves. The photocatalytic activity of the resultant graphene-TiO2 composites containing 25 wt.% TiO2 is better than that of commercial pure TiO2. This is partly due to the extremely small size of the TiO2 nanoparticles and partly due to the graphene-TiO2 composite structure consisting of homogeneous dispersion of crystalline TiO2 nanoparticles on the graphene sheets. As the graphene in the composites has a very good contact with the TiO2 nanoparticles it enhances the photo-electron conversion of TiO2 by reducing the recombination of photo-generated electron-hole pairs. (C) 2011 Elsevier B.V. All rights reserved.