Titanium dioxide, bond energy

If so, one may expect products to result from chemical bond formation between the cation-radical-anion-radical pair, which are both paramagnetic and of opposite charge. In the latter route, there is a precedent for the formation of dioxetane intermediates of stable olefin cation radicals [51], as in the characterization by Nelsen and coworkers of a dioxetane cation radical from adamantylidene cation radical [52]. If a dioxetane is formed, either in neutral form or as a cation radical, the Ti02 surface can function in an additional role, that is, as a Lewis acid catalyst, to induce decomposition of the dioxetane. Since no chemiluminescence could be observed in these reactions, apparently Lewis acid catalysis provides a nonradiative route for cleavage of this high-energy intermediate. That Ti02 can indeed function in this way can be demonstrated by independent synthesis of the dioxetane derived from 1,1-diphenylethylene, which does indeed decompose to benzophenone when it is stirred in the dark on titanium dioxide. 

In the most commonly studied configuration of the DSSC, the electron conductor is a wide band gap, nanocrystalhne, metal oxide film. Colloidal titanium dioxide is most often used although other wide band gap metal oxides are candidates. The sensitizer is a transition metal-based (usually ruthenium), organic dye, with excited state free energy sufficient to reduce the semiconductor, and containing ligands, such as carboxylates or phosphonates, which facilitate bonding to the semiconductor... 

Rutile (TiOj) can be prepared in the form of single crystals by the Vemeuil (flame fusion) technique. Slightly reduced rutile is an n-type semiconductor with an energy gap of 3.05 eV and electron mobilities of -1.0 cmWs at room temperature. TITANIUM DIOXIDE SUPPLIERS ALFA AESAR, A JOHNSON M AITHEY COMPANY 30 Bond St. 

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