Effect of sintering temperature on photocatalytic activity of cadmium monoxide plus cadmium titanate thin solid films deposited by the sol–gel technique

Cadmium monoxide plus Cadmium Titanate [CdO + CdTiO₃] thin solid films were prepared on soda-lime glass substrates by means of the sol-gel technique. Two Titanium [Ti]/ Cadmium [Cd] ratios, 0.54, and 0.67, in the precursor solutions were studied. After the dipping process, the samples were sintered in an open atmosphere during one hour at selected temperatures (T_s) in the range of 350–600 °C. The variation of T_s was in steps of 50 °C. These the thin solid films were analyzed using X-ray diffraction, UV–Vis optical absorption, and atomic force microscopy. The photocatalytic activity (PA) was measured by means of the photobleaching of an aqueous solution of methylene blue (MB) after irradiation with an UV-lamp. The MB concentration was determined by using optical absorption spectra, measured before and after the photobleaching process, and the Beer-Lambert principle. The best PA was obtained for films sintered at 500 °C for both [Ti]/[Cd] ratios studied, as for this T_s value the PA was very similar.