Titania-silica mixed oxide (TiO2-SiO2) was prepared from the alkoxides: titanium tetrabutoxide (TBOT) and tetraethyl orthosilicate (TEOS), by using an ammonia-water solution as the hydrolysis catalyst. Variables included synthesis route, aging time, the type of alcohol, and calcination temperature. The materials were then evaluated as photocatalysts for the decomposition of n-heptane. Experimental results revealed: (1) the photoactivity of TiO2-SiO2 Prepared via the route that Ti sol and Si sol were simultaneously and slowly added, was significantly enhanced due to its good homogeneity. However, for pure TiO2 the route that Ti sol was slowly added into ammonia-water solution was effective in inhibiting the growth of crystalline size and therefore improving the photoactivity; (2) longer aging time promoted the hydrolysis of TEOS. As a result, the intimate interaction between titania and silica (Ti-O-Si hetero linkages) were strengthened and the photoactivity was increased; (3) TiO2-SiO2 prepared by using ethanol as the solvent had the best combination of crystalline size, crystallinity, and homogeneity, thus, it exhibited the best photoactivity among the mixed oxides prepared via different alcohols; (4) 600 degrees C calcined TiO2-SiO2 possessed excellent photoactivity as compared with that calcined at 400 or 800 degrees C due to the good crystallinity and the synergism between Ti-O-Si hetero linkages and surface hydroxyl groups. (c) 2005 Published by Elsevier B.V.