As a new type of promising semiconductor photocatalyst, SnO2 cannot be widely applied due to its low utilization efficiency to visible light and swift recombination of photogenerated electrons and holes. These drawbacks were effectively overcome by preparing the B/Ag/F tridoped SnO2-ZnO composite films using the simple sol–gel method. The degradation of the methyl green and formaldehyde solutions was used to value the photocatalytic activity of the samples. Photoluminescence (PL) spectra and the UV–Vis absorption spectroscopy results of the samples illustrated that the B/Ag/F tridoped SnO2-ZnO composite film not only improved the lifetime of the charge carriers, but also enhanced their visible light absorption. The X-ray diffraction (XRD) results showed that the crystalline SnO2 was in the structure of rutile. As exhibited in the BET surface area results, the specific surface area of pure SnO2 was 19.9 m2g−1, while that of the B/Ag/F tridoped SnO2-ZnO was 85.3 m2g−1. Compared to pure SnO2, SnO2-ZnO, or the mono- or di-doped SnO2-ZnO films, the B/Ag/F tridoped SnO2-ZnO composite film had the highest photocatalytic activity.

In order to effectively photodegradate organic pollutants, ZnO composite and Co-B codoped TiO2 films were successfully deposited on glass substrates via a modified sol-gel method and a controllable dip-coating technique. Combining with UV–Vis diffuse reflectance spectroscopy (DRS) and photoluminescence spectra (PL) analyses, the multi-modification could not only extend the optical response of TiO2 to visible light region but also decrease the recombination rate of electron-hole pairs. XRD results revealed that the multi-modified TiO2 film had an anatase-brookite biphase heterostructure. FE-SEM results indicated that the multi-modified TiO2 film without cracks was composed of smaller round-like nanoparticles compared to pure TiO2. BET surface area results showed that the specific surface area of pure TiO2 and the multi-modified TiO2 sample was 47.8 and 115.8 m2/g, respectively. By degradation of formaldehyde and oxytetracycline, experimental results showed that the multi-modified TiO2 film had excellent photodegradation performance under visible light irradiation.

The nanocrystalline S doped titanium dioxide films were successfully prepared by the improved sol-gel process. Here TiO(C 4 H 9 O) 4 and CS(NH 2 ) 2 were used as precursors of titania and sulfur, respectively. The as-prepared specimens were characterized using x-ray diffraction (XRD), x-ray energy dispersive spectroscopy (EDS), high-resolution field emission scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller (BET) surface area, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic activities of the films were evaluated by degradation of organic dyes in aqueous solution. The results of XRD, FE-SEM, and BET analyses indicated that the TiO 2 films were composed of nanoparticles. S doping could obviously not only suppress the formation of brookite phase but also inhibit the transformation of anatase to rutile at high temperature. Compared with pure TiO 2 film, S doped TiO 2 film exhibited excellent photocatalytic activity. It is believed that the surface microstructure of the modified films is responsible for improving the photocatalytic activity.

The nanocomposite Al 2 O 3– Y 2 O 3 films were prepared on the surface of carbon steel by an electrochemical process and a sintering process. High-resolution field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the films, indicating that the films have nanostructures and the deposited alumina layers have a composition close to the stoichiometry of Al 2 O 3. SEM and mass gain measurement are adopted to study the oxidation resistance of films on carbon steel. It is proved that this kind of film is effective in protecting the substrate from oxidation. The mechanisms accounting for such effects have been discussed.