complexes of the substrates (S) and the TiO2surface, exhibited an exponential decline with the increasing of the methylene number of S. The determined decay factor (beta) of 9 nm(-1) also supports the fact that the 4-(methylthio)phenyl chromophore is separated from the TiO2surface. The efficiency of the one-electronoxidation of S adsorbed on the TiO2surface, which was determined from the relationship