New TiO2/SiO2 nanocomposites-Phase transformations and photocatalytic studies

A series of TiO2/SiO2 nanocomposites were synthesized via a novel sol-gel method. A phase transformation study of as-synthesized nanocomposite due to thermal treatment up to 1100 degrees C has showed the existence of anatase phase in all the tested temperatures. At thermal treatment, when the temperature exceeded 400 degrees C, brookite phase was formed beside anatase phase. At 950 degrees C, the amorphous silica matrix was transformed to crystobalite and the brookite phase disappeared. Finally, the small peaks of rutile phase were detectable at 1100 degrees C. The presence of tetrahedral coordination of TiO2 in SiO2 matrix was confirmed by UV-vis study. The produced nanocomposites have good photocatalytic properties due to its anatase phase, tetrahedral coordination of TiO2 in SiO2 matrix and very large surface area. The photocatalytic properties of the composites were compared for the degradation of Congo Red (CR) azo dye. Further studies were also devised to compare the catalytic efficiency of the composite with the synthesized pure TiO2. The results revealed that the as-prepared composite is the most effective. (C) 2010 Elsevier B.V. All rights reserved.