Defect formation in surface modified TiO2 nanostructures.

The defect formation in surface modified TiO2 has been studied. Anatase TiO2 structures in the 3-20 nm range formed by a wet chemical technique were surface modified and nitridation of the highly reactive TiO2 nanocolloid surface was achieved by a quick and simple treatment in alkyl ammonium compounds. The nitriding process was also accompanied by a metal surface coating process using electroless plating techniques, resulting in a thin metal surface layer on the modified TiO2 nanostructures. The crystal structure of the resultant TiO2-xNx nano-colloids remained anatase and the freshly prepared samples exhibited a strong light emission near 560nm (2.21 eV), which red shifted to 660 nm (1.88 eV) and dropped in intensity with aging in the atmosphere. This behavior was also evident in some of the combined nitridized and metal coated TiO2 nano-colloids. Electron Spin Resonance performed on these samples identified a resonance at g = 2.0035, which increased significantly with nitridation. This resonance is attributed to an oxygen hole center created near the surface of the nanocolloid, which correlates well with the observed optical activity.