TiO_2 thin films were prepared by a sol-gel method on ITO and glass substrates. The hydrophilicity change under two wavelength UV light was investigated by the determination of the contact angle of water. Cyclic voltammetric behavior of ITO/TiOj electrode under ultraviolet (UV) illumination with different wavelength was measured in the solution of Na2SO4. Two photoelectrochemical processes for TiO2 thin firm electrode under UV illumination can be observed. The conversion rates of hydrophilicity of the TiO2 thin film and the two photoelectrochemical processes were determined by the wavelength of the UV light. The main reason is that ultraviolet light with short wavelength has high energy and absorbance. A mechanism was proposed on the base of these two photoelectrochemical processes. It is assumed that the change of hydrophilicity of the films was related with the changes of surface stmcture when the film was irradiated by UV light.

Key words: TITANIUM OXIDE, THIN FILMS, CYCLOVOLTAMGRAPH, HYDROPHILICITY, MICRO-STRUCTURE