抄録
There exist two types of photo-effects on TiO2 surface. One is the well-known photocatalytic reaction proceeding on the TiO2 surface irradiated by UV light. Another is the photo-induced super-hydrophilic and simultaneously superoleophilic conversion of the TiO2 surface. In other words, both water and oil drops spread completely on the UV irradiated surface. This effect was found recently, and is attributed to the nanometer scale hydrophilic domain structure formed on an original oleophilic TiO2 surface by the UV irradiation. The results of recent detailed experiments suggest that the hydrophilic domains are formed by the surface reduction by the photo-produced electrons. The produced holes will be used by the oxidation of bridging oxygen ions of TiO2 surface, releasing molecular oxygen followed by the adsorption of molecular water. The detailed mechanism is explained in this review article. Moreover it is described that various materials coated with this type of TiO2 transparent film can show anti-fogging and self-cleaning effects. Their industrial applications are also described.
