Superhydrophilicity, photoinduced

Upon excitation of a semiconductor, the electrons in the conduction band and the hole in the valence band are active species that can initiate redox processes at the semiconductor-electrolyte interface, including photocorrosion of the semiconductor, a change in its surface properties (photoinduced superhydrophilicity [13]), and various spontaneous and non-spontaneous reactions [14-19]. These phenomena are basically surface-mediated redox reactions. The processes are depicted in Fig. 16.1. Owing to the slow spontaneous kinetic of the reactions between the... 

Understand that a consideration of similar ideas about photo-excited Ti02 leads to an explanation of a variety of effects, such as removal of pollutants in water and air, destruction of cells of pathogens and cancers, and the concept of semiconductor-photoinduced superhydrophilicity. 

Figure 11.13 Schematic mechanism of the photoinduced superhydrophilicity of Ti02...

Figure 17-6. The photoinduced wettability change of water and hexadecane (a) the amphiphilic conversion and (b) superhydrophilic and oreophobic conversion by UVirradiation.

Not only pure Ti02 but also composite photocatalysts have been widely investigated. A mixture of Ti02 precursors (or sol) and other metal oxide precursors (or sol) gives an inorganic composite film. As mentioned below (additionally, Section Composites and dopant additions ), various compositions as a powder or a film have been prepared in order to improve photocatalytic activities and/or photoinduced superhydrophilic properties. 

Dohshi, S., Takeuchi, M., and Anpo, M. Photoinduced superhydrophilic properties of Ti-B hinary oxide thin films and their photocatalytic reactivity for the decomposition of NO. J. Natwsci. Nanotech. 2001,1, 337. 

Anpo, M., Dohshi, S., and Takeuchi, M. Preparation of Ti/B binary oxide thin films by the ionized cluster beam (ICB) method Their photocatalytic reactivity and photoinduced superhydrophilic properties. J. Ceram. Process. Res. 2002, 34, 258. 

Photoinduced superhydrophilication due to water-attracting hydroxyl groups (-OH) - High water-wettability effect... 

Si02 coating and an outer Ti02 coating. The self-cleaning effect is related to the photoinduced superhydrophilicity of thin nanoporous Ti02 films. 

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