TiO2 nanoparticles (NPs) were deposited on the surfaces of SiO2 microspheres with a mesoporous structure prepared by a hydrolysis-controlled sol-gel technique. The TiO2 NPs were firmly combined on the surfaces of SiO2 microspheres through the interfacial Si-O-Ti bonds. The coupling causes the bandgap widening up to 3.37 eV, enhancing the photocatalytic activity for the decomposition of acetaldehyde under illumination of UV-light (330 < lambda < 400 nm). Density functional theory calculations for model clusters suggested that the observed results are derived from the lowering in the valence band edge energy with the interfacial bond formation. (C) 2011 Elsevier Inc. All rights reserved.