Abstract: TiO₂-SiO₂ thin films were prepared by the sol-gel processing. The photocatalytic activity of the thin films were characterized by means of the photocatalytic degradation of methylene blue under
UV irradiation. The structures of the films and powders were studied by using X-ray photoelectron spectroscopy, FTIR, HRTEM, FE-SEM, AFM and UV-Vis-NIR transmission spectroscopy. The effect of
its structure of the film on photocatalytic activity was investigated. It was found that the degradation rate of methylene blue of the TiO₂-SiO₂ thin film (Si/Ti=0.2) was the best of all. Rutile and anatase
phases were detected in TiO₂ powders while only anatase TiO₂ was detected in TiO_₂-SiO₂ powders even annealed at 500℃. The main mechanism could be ascribed to the fact that Ti--O--Si
amorphous glassy phase and amorphous SiO₂ are created when SiO₂ is doped in TiO_₂ thin film, these two phases enclose TiO₂ particles, which block the transformation of TiO₂ from
anatase to rutile and limit the growth of crystal sizes, so the photocatalytic activities can be improved .

Key words: TiO₂-SiO₂ thin film, composites, sol-gel method, photocatalytics