Electron Transfer between Metal Ions and Photoexcited Semiconductors

Electron transfer between metal ions and excited solid materials is central to many catalytic events in natural and synthetic systems. The interaction of metal ions, leading to their reduction, with the excited semiconductor is expected to decrease the lifetime of excited electrons and increase that of the holes. By conducting this reaction using a semiconductor single crystal [rutile TiO2 (110)] in the aqueous phase and the presence of different Ag+ concentrations, it was found that the initial signal of excited electrons increases and the signal related to holes decreases, which is the opposite of expectations. Results indicate that this is most likely related to the initial interaction, the adsorption process (surface OGS–Ag+; GS: ground state) that precedes the electron transfer reaction (Tiex3+–Ag metal; ex: excited state). Similar results are obtained for the Ce4+ interaction with the surface of TiO2(110).