Temperature-dependent thermal stability and dispersibility of SiO2–TiO2 nanocomposites via a chemical vapor condensation method

Surface-modified TiO2 nanoparticles were prepared by a chemical vapor condensation method (CVC). The resultant nanocomposites were subjected to post-heat treatment with various temperatures. The sedimentation behavior of the surface-modified TiO2 nanoparticles in aqueous solution was investigated visually using a separation analyzer. The dispersion stabilities of the pure CVC-made TiO2 and the surface modified SiO2–TiO2 samples were enhanced due to low zeta potential values compared to a commercial TiO2 sample (P25). With increasing heat treatment temperature, the photocatalytic activity of the pure TiO2 samples (CVC–TiO2 and P25) suddenly dropped, which resulted from the increased particle size and the reduced anatase content. For the surface-modified TiO2 nanoparticles, the anatase-to-rutile phase transformation process did not occur even at 900 °C. Although the surface-modified TiO2 nanoparticles formed using the chemical vapor condensation method were thermally treated with high temperature, the photocatalytic activity was higher than that of the pure TiO2 samples. This is probably due to the fact that the surface-modified TiO2 nanoparticles had increased thermal stability, and SiO2 provides better adsorption sites in the vicinity of the TiO2.