Comparative study of TiO 2 particles in powder form and as a thin nanostructured film on quartz

Abstract

A sol–gel method was employed to prepare TiO 2 particles in the powder form and on a flat quartz (SiO 2) 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 TiO 2 on SiO 2 and TiO 2 in the powder form (self-supported). However, after annealing at 800 °C the TiO 2 particles on SiO 2 remained in the anatase form, whereas the anatase phase of self-supported TiO 2 particles was easily converted into the rutile form. TiO 2 particles on SiO 2 remained as individual crystallites even at 800 °C despite the growth of their size, whereas annealing TiO 2 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 TiO 2 on SiO 2 and TiO 2 in the powder form in the reaction of acetaldehyde oxidation demonstrated the TiO 2 on SiO 2 superiority with quantum yields significantly higher than that of TiO 2 powder.