Surface modification and optical behavior of TIO2 nanostructures

TiO2 is a very important material from the perspective of photocatalytic applications, but due to its 3.2 eV bandgap, it is not possible to make this material efficient under visible illumination. Anatase TiO2 nanoclusters in the 3-30 nm range have been formed by a wet chemical technique and surface modified in order to enhance the absorption of visible light. Nitridation of the highly reactive TiO2 nanosphere surface has been achieved by a quick and simple treatment in alkyl ammonium compounds and the metallization of this surface has been achieved by electroless plating. Although the structure of the resultant material remains anatase, some of the treated material exhibits strong emission between 550-560 nm, which red shifts and drops in intensity with aging in the atmosphere. Electron Spin Resonance performed on these samples identify a resonance at g=2.0035, which increases significantly with the nitridation step. This resonance is attributed to an oxygen hole center created near the surface of the nanoclusters, which correlates well the noted optical activity.