Photochemical reactions INDEX

The photochemical properties of titania surfaces are of interest for several reasons. They determine the stability of pigmented paint systems [76], the rate at which pollutants can be degraded in systems designed to purify air and water [77], and are the root cause of poorly understood phenomena such as water photolysis [78] and super hydrophilicity [79]. Using thin rutile epilayers with five low index orientations, it has been shown that the relative rates of photochemical reactions catalyzed by titania depend on the surface orientation [80]. In this chapter, experiments used to map the complete orientation dependence of the relative photochemical reactivity of TiO are described [81-83]. In this case, the relevant reactions are carried out at room temperature and this gives us the opportunity to fix both the surface morphological structure and stoichiometry. For the reactions described here, all of the surfaces were... 

In principle, any kinds of organic dyes which undergo photochemical reactions by irradiation with visible laser light (635-830 nm) can be used as the memory media. The photochemical reactions can be detected by changes in refractive index as well as in absorption properties. Although most of photochemical reactions are irreversible, some organic dyes undergo reversible photochemical reactions [photo-chromism) and the photochromic dyes are potentially applicable to erasable optical memory media. 

Electrochemical detection is inherently a chemical rather than a physical technique (such as ultraviolet, infrared, fluorescence, or refractive index). It is, therefore, not surprising to hnd that many imaginative postcolumn reactions have been coupled to LC-EC. These include photochemical reactions, enzymatic reactions, halogenation reactions, and Biuret reactions. In each case, the purpose is to enhance selectivity and therefore improve limits of detection. While simplicity is sacrihced with such schemes, there are many published methods that have been quite successful. 

Figure i. Optical absoiption spectnim of thin film (0.7S/t) of MAI (17 %) polymer before and after exposure to intense short wavdength ultraviolet light, possible photochemical reaction mechanism, and observed refiracdve index changes in the film. 

Kudo H, Yamamoto M, Nishikiibo T, Moriya O. 2006. Novel materials for large change in refractive index synthesis and photochemical reaction of the ladderlike poly(silsesquiox ane) containing norbomadiene, azobenzene, and anthracene groups in the side chains. Macromolecule 39 1759 1765. 

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