a shows an FESEM image (top view) of a nanocrystallineTiO2film with an average particle size of about 20 nm. The specificsurface area, the average pore size and porosity of the meso-porous TiO2film were estimated to be about 80 m2g−1, 30 nm,and 78% by the Brunauer-Emmett-Teller (BET) analysis, respec-tively.