Titanium dioxide (TiO2) thin films are used for a broad range of applications such as wastewater treatment, photocatalytic degradation activity, water splitting, antibacterial and also in biomedical applications. There is a wide range of synthesis techniques for the deposition of TiO2 thin films, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), both of which are well known deposition methods. Layer by layer deposition with good homogeneity, even thickness and good adhesive nature is possible by using the PVD technique, with the products being used for photocatalytic applications. This review studies the effects of magnetron sputtering conditions on TiO2 films. This innovative technique can enhance the photocatalytic activity by increasing the thickness of the film higher than any other methods. The main purpose of this article is to review the effects of DC and RF magnetron sputtering conditions on the preparation of TiO2 thin films for photocatalysis. The characteristics of TiO2 films (i.e., structure, composition, and crystallinity) are affected significantly by the substrate type, the sputtering power, the distance between substrate and target, working pressure, argon/oxygen ratio, deposition time, substrate temperature, dopant types, and finally the annealing treatment. The photocatalytic activity and optical properties, including the degree of crystallinity, band gap (Eg), refractive index (n), transmittance (T), and extinction coefficient (k), of TiO2 films are dependent on the above- mentioned film characteristics. Optimal TiO2 films should have a small particle size, a strong degree of crystallinity, a low band gap, a low contact angle, a high refractive index, transmittance, and extinction coefficient. Finally, metallic and nonmetallic dopants can be added to enhance the photocatalytic activity of TiO2 films by narrowing the band gap.

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A hydrothermal method is proposed for the synthesis of TiO2 nanoparticles, which were further sintered at 200 °C, 300 °C, 500 °C, and 800 °C in a hot air oven. UV–light-driven photodegradation of Rhodamine-B dye was studied for as-prepared and sintered samples. The low probability of recombination of electron-hole pair and high charge separation rate showed better performance in degradation efficiency for a sample sintered at 300 °C. X-ray diffraction patterns suggest that as the sintering temperature is increased, amorphous nature vanishes and a pure anatase phase is observed. With a further increment of sintering temperature above 300 °C, mixed phase is observed. Band bending phenomenon of anatase and rutile provides a clear view on photocatalytic performance. Kinetics and mechanism of adsorbed water molecules with the bridging oxygen vacancy and 5 fold coordinated titanium (Ti5c) of reduced anatase TiO2 (101) is illustrated schematically, where energy is reduced in the presence of bridging oxygen vacancy. The concept of oxygen vacancies and water molecule adsorption over reduced titania surface is discussed. The reaction mechanism process of the kinetics of the adsorbed water molecules with the bridging oxygen vacancy defects and Ti5c site along the bridging and terminal hydroxyl radical are embedded on reduced TiO2 (101) nanoparticles.