DYE SENSITIZATION OF TIO2 SURFACES STUDIED BY RAMAN-SPECTROSCOPY

Surface modification by suitable dyes of TiO2 electrodes used in photoelectrochemical cells allows noticeable increase of their photo-to-electrical conversion efficiency. Several bis or trisbipyridylruthenium(II) complexes, containing different functional groups (in particular, carboxylation of the pyridine ring is necessary to obtain a strong adsorption) were studied. All of them were identified by ''normal'' (without any ''artificial'' enhancement) ex situ Raman spectroscopy. The differences (in peak position and intensity) of their spectra, typical of the pyridine rings, carboxylated or not, yields the position of the molecule with respect to the oxide surface. It is the first time that such a monolayer-on-oxide substrate was studied by Raman spectroscopy; the laser light must stimulate the charge transfer in the Ti-molecule surface complex.