Visible light absorption of surface modified TiO 2 powders with bidentate benzene derivatives

TiO 2 powders with different specific surface area were prepared using reproducible, sol–gel synthetic route and their ability to form hybrids with catechol and 5-amino salicylic acid was compared with the commercially available Degussa P25 TiO 2 powder. Microstructural characterization involving transmission electron microscopy, X-ray diffraction analysis and nitrogen adsorption–desorption isotherms indicated that TiO 2 samples cover reasonably wide size and/or specific surface area range (50–115 m 2 /g). The surface modification of TiO 2 powders with catechol and 5-amino salicylic acid induced significant shift of absorption to the visible spectral region due to charge transfer complex formation. It should be emphasized that tunable optical properties of TiO 2 in powder form have never been reported in the literature. The largest red shift of the absorption onset was observed for sample with the largest specific surface area upon surface modification with both ligands. The binding of the modifier molecules to the surface Ti atoms was studied using Fourier transform infrared spectroscopy.