Fluorescence and Raman spectroscopic characteristics of the photo-induced electron transfer of Coumarin 343 dye-sensitized TiO₂ nanoparticles

The fluorescence and Raman spectroscopic characteristics of the photo-induced electron transfer of Coumarin 343 (C343) dye-sensitized TiO₂ nanoparticles have been investigated. The results indicate that the red-shift of the absorption spectrum peaks and the fluorescence spectrum maxima can be attributed to the photo-induced electron transfer from the excited state of the absorbed C343 dye molecules and the charge transfer complex (C343/TiO₂) to the conduction band manifold of the TiO₂ nanoparticles. Back electron transfer of the system was investigated by time resolved fluorescence spectroscopy and takes place in around τ₁=31 ps. Raman spectroscopy of the C343 dye-sensitized TiO₂ nanoparticles reveals that the carbon bond stretching vibrations and ring breathing motions of the absorbed C343 dye molecules at the interface significantly contribute to the ultrafast interface photoinduced electron transfer.