Semiconductor powder irradiated, heterogeneous

The study of heterogeneous photosystems, involving u.v. or visible light irradiation of aqueous suspensions of semiconductor powders or colloids, has increased steadily over the past five years. Many studies are aimed at development of systems capable of cyclic water cleavage, although, as mentioned earlier, Ti02 doped with iron functions as a photocatalyst for reduction of N2 to The most popular semiconductor materials continue to be TiOj... 

Photoexcitation of n-type semiconductors renders the surface highly activated toward electron transfer reactions. Capture of the photogenerated oxidizing equivalent (hole) by an adsorbed oxidizable organic molecule initiates a redox sequence which ultimately produces unique oxidation products. Furthermore, specific one electron routes can be observed on such irradiated surfaces. The irradiated semiconductor employed as a single crystalline electrode, as an amorphous powder, or as an optically transparent colloid, thus acts as both a reaction template and as a directed electron acceptor. Recent examples from our laboratory will be presented to illustrate the control of oxidative cleavage reactions which can be achieved with these heterogeneous photocatalysts. 

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