Hydrophilic property of SiO2-TiO2overlayer films and
TiO2/SiO2mixing films①
TiO2/SiO2mixing films①
(1. Research Institute of Chemical Equipment, East China University of Science and Technology,
Shanghai 200237, China;
2. Engineering Department, Laiyang Agricultural College, Laiyang 265200, China)
Shanghai 200237, China;
2. Engineering Department, Laiyang Agricultural College, Laiyang 265200, China)
Abstract: The photo-induced hydrophilicity of SiO2overlayer on TiO2films prepared by sol-gel method was investigated by means of soak angle measurement, XPS, UV-VIS and FTIR spectra. The results show that, compared with the TiO2 film without SiO2overlayer, when the TiO2film is thoroughly covered by SiO2overlayer, the hydrophilicity and the sustained effect are enhanced. It is found that the significant growth of the OH-group occurs in the surface of SiO2overlayer. The different mechanism of enhanced hydrophilicity between SiO2 overlayer on TiO2films and TiO2/ SiO2mixing films was analyzed. The result suggests that the photo-generated electrons created in the interface between TiO2 and SiO2 tendto reduce the Ti(Ⅳ) cation to the Ti(Ⅲ) state, and the photogenerated holes transmit through the SiO2 layer to upper most surface efficiently. Once the holes go up to the surface, they tend to make the surface hydrophilic. The stable hydrophilicity of SiO2 overlayer which adsorbs more stable OH groups, enhances the sustained effect, i.e. the super-hy drophilic state can be maintained for a long time in dark place.
Key words: TiO2; SiO2; super-hydrophilic property; overlayer films; sol-gel method