Direct formation and photocatalytic performance of anatase (TiO2)/silica (SiO2) composite nanoparticles

Anatase (TiO2)/silica (SiO2: 23.9-27.7 mol%) composite nano-particles were directly synthesized from (i) the reaction of titanyl sulfate (TiOSO4) and sodium metasilicate (Na2SiO3) under mild hydrothermal conditions, (ii) the acidic precursor solutions of TiOSO4 and tetraethylorthosilicate (TEOS) by thermal hydrolysis, and (iii) the metal alkoxides, i.e., tetraisopropoxide (TTIP) and TEOS, by the sol-gel method. Their photocatalytic activities were evaluated by measurements of the relative concentration of methylene blue after UV irradiation. The as-prepared TiO2/SiO2 composite nanoparticles showed far more improve. photocatalytic activity than the pure anatase-type TiO2. The composite nanoparticles formed from (i) TiOSO4 and Na2SiO3 as well as those from (ii) TiOSO4 and TEOS showed fairly good photocatalytic activity, and it was better than that of those synthesized from (iii) the metal alkoxides, which was suggested to be due to the difference in crystallinity of the anatase.