Retarding Effect of Silica on the Growth and Anatase-to-Rutile Transformation of TiO2 Nanocrystals

By pre-hydrolysis of TEOS, Ti02/SiO2 composites with homogeneous texture were prepared by a sol-gel process. These composite powders were characterized by UV/Vis spectra, FT-IR, TEM, XRD, and BET techniques. It was found that the growth and anatase-to-rutile transformation of titania nanocrystals in the composite were retarded significantly in the presence of small amount of silica. Mesoporous TiO2 with high specific surface area and crystalline framework was obtained by selective dissolving of silica in composite. The fact that more than 90% of silica was removed after selective dissolving and the resulting TiO2 was mesoporous with mean pore size about 4nm suggested the network of ultrafine silica was continuous and uniform.