W/sup +6//W/sup +5/ redox reactions at the interface of the nanocrystalline TiO/sub 2/ photoactive electrode

Photocurrent of nanocrystalline TiO/sub 2/ thin films has been probed by using a steady-state photoconduction technique. A broad single peak (280-410 nm) photocurrent spectrum was observed for the TiO/sub 2/ thin films. The photocurrent maximum at about 360 nm associates with the direct band gap of anatase TiO/sub 2/. The electron-hole pair formation that occurs at the interface between semiconductor TiO/sub 2/ nanoparticles and a solution upon absorption of near UV light leads to redox reactions of solution species (W/sup +6//W/sup +5/). The mechanism of such photodriven processes are discussed along with the potential applications in photoelectrochemical cells and as particulate photochromic systems.