Surface modification of titanium dioxide nanoparticles
Nanocrystalline titanium dioxide (TiO2), a wide band-gap semiconductor, is synthesized by a sol-gel method for studies of its photocatalytic activity. In this work, surface modification of TiO2 utilizing various species is performed. The surface modifications are performed on both pure and doped TiO2. It is shown that surface modifications affect the phase transition temperature of TiO2. Band gap energy modifications, via dopants, in combination with surface absorbed species have been shown to affect the photocatalytic activity of TiO2. Surface adsorbed species must be inert to redox reactions in order remain bound to the surface, yet facilitate charge transport from the TiO2 bulk into a species on the surface. Typically dye sensitizers are anchored to semiconductor oxide surfaces via carboxylates. The polarization at the carboxylate-oxide interface junction may interfere with the charge injection process. Here, the use of anchors containing species of different polarities (phosphates, sulfates, silicates, etc.) at the interface junction is analyzed for improvements in the charge injection process. This charge injection process is measured by observing the extent in which methylene blue is degraded. In this work, characterization is performed by a variety of microscopic and spectroscopic techniques.