Transparent TiO2-SiO2 thin films doped with single dopants, such as a metal (Fe3+ ions), a non-metal (N-S), or a sensitizing dye (polyaniline, PANI), were synthesized by a modified sol-gel method combined with the peroxo titanic acid (PTA) approach at low temperature (similar to 100 degrees C). These samples were characterized by X-ray diffraction, wavelength-dispersive X-ray fluorescence spectrometry, Fourier-transform infrared spectroscopy, nitrogen adsorption-desorption isotherm measurements, and UV-Vis spectroscopy. The photocatalytic activities of the films were assessed by the degradation of methylene blue and formaldehyde. The results indicated that the crystallite size of anatase TiO2 was 15 nm. The photocatalytic activities toward gaseous formaldehyde degradation were similar, about 90% and 87% under UV and visible light irradiation, respectively, in the case of all the samples. These results suggested that the doped TiO2-SiO2 thin films exhibited high photoactivities.