DYE SENSITIZATION OF TIO2 SURFACES STUDIED BY RAMAN-SPECTROSCOPY

Surface modification by suitable dyes of TiO2 electrodes used in photo electrochemical cells allows noticeable increase of their photo-to-ele ctrical conversion efficiency. Several bis or trisbipyridylruthenium(I I) complexes, containing different functional groups (in particular, c arboxylation of the pyridine ring is necessary to obtain a strong adso rption) were studied. All of them were identified by ''normal'' (witho ut any ''artificial'' enhancement) ex situ Raman spectroscopy. The dif ferences (in peak position and intensity) of their spectra, typical of the pyridine rings, carboxylated or not, yields the position of the m olecule with respect to the oxide surface. It is the first time that s uch a monolayer-on-oxide substrate was studied by Raman spectroscopy; the laser light must stimulate the charge transfer in the Ti-molecule surface complex.