Comparative study of TiO2 particles in powder form and as a thin nanostructured film on quartz

A sol–gel method was employed to prepare TiO2 particles in the powder form and on a flat quartz (SiO2) support. Calcination at progressively higher temperatures caused morphological and structural changes, which were followed by XRD, UV-Vis spectroscopy, AFM, and SEM microscopy. In particular, it was found that annealing at 500 °C leads to the formation of the anatase phase for both TiO2 on SiO2 and TiO2 in the powder form (self-supported). However, after annealing at 800 °C the TiO2 particles on SiO2 remained in the anatase form, whereas the anatase phase of self-supported TiO2 particles was easily converted into the rutile form. TiO2 particles on SiO2 remained as individual crystallites even at 800 °C despite the growth of their size, whereas annealing TiO2 powders at 500 and 800 °C led to bigger crystallites with their eventual sintering to very big particles of micrometer size. Examination of the photocatalytic activity of TiO2 on SiO2 and TiO2 in the powder form in the reaction of acetaldehyde oxidation demonstrated the TiO2 on SiO2 superiority with quantum yields significantly higher than that of TiO2 powder.