Differences in adsorption behavior of N3 dye on flat and nanoporous TiO2 surfaces

The adsorption of N3 dye on two types of TiO2 surfaces (rutile single crystals and anatase nanocrystalline films) was studied. We used highly sensitive absorption spectroscopy to acquire absorption spectra of sub-monolayer amounts of dye adsorbed on rutile TiO2 single crystals. We found that absorption spectra were not sensitive to dye amount in single crystals, whereas the peak shifted toward longer wavelength region with increasing dye amount in nanocrystalline films. We also found that much less N3 dye was adsorbed on the nanoporous surface than on the flat (single-crystal) surface. Possible reason for these experimental findings will be discussed.