Metal-to-particle charge-transfer

In this chapter, we describe the excited-state and electron transfer properties of transition metal compounds anchored to nanocrystalline Ti02 (anatase) particles. Emphasis is given to interfacial charge transfer processes relevant to the conversion of light into other forms of energy. We discuss new advances that have enabled practical applications in electrical power generation and the production of useful fuels. The discussion is not meant to be comprehensive but details key advances that represent new opportunities for further research and application. 

UV-visible spectra of the alkoxides can be attributed to the charge-transfer band of unshared electron pairs on the oxygen atoms to the empty metal orbital. Metal ion is suitable for studying subtle changes in the coordination number and oxygen donor ligands. The visible emission is believed to stem from defect levels associated with oxygen vacancies. The broadness of the emission frequencies indicates a presence of broad particle size distribution or low crystallinity. 

The unhindered ionic charge transfer requires many open pores of the smallest possible diameter to prevent electronic bridging by deposition of metallic particles floating in the electrolyte. Thus the large number of microscopic pores form immense internal surfaces, which inevitably are increasingly subject to chemical attack. 

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