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Trivalent metal-doped TiO2 thin films have been extensively investigated in gas sensor applications. The trivalent metal dopants are Al, Y and Gd. The trilayer fabrication of a gas sensor consists of a thin film, sputtered TiO2 and Au nanoparticles. The characteristics of the gas sensing properties are strongly correlated with the annealing temperature, film thickness, type of doping and deposition method. The subsequent properties are presented - the crystalline structure, grain size, roughness, strain, stress and defects. Thin films have been developed with concentrations of O2 gas up to 10 sccm. A response time for O2 gas in milliseconds was obtained at room temperature. Al doped TiO2 thin film have a faster response time operating at room temperature compared with other thin films. Oxygen vacancy defects also contribute to the speed of the response time for a gas sensor. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) has been intensively investigated for solar hydrogen conversion via photocatalytic and photoelectrochemical water splitting. However, the performance of TiO2 photocatalyst for hydrogen generation is low due to the rapid electron-hole recombination and its wide band gap (3.0-3.2 eV) which is only feasible for UV light absorption of solar spectrum. There are various strategies have been used for TiO2 modification to harvest the sunlight and improve the surface chemical reaction between TiO2 and H2O for water splitting. Among the TiO2 modification strategies, intrinsic point defects such as vacancies and interstitials in TiO2 have been proven to improve the TiO2 properties for photo-catalytic activity. In this article, the recent progress achieved in defective TiO2 with intrinsic point defects for photocatalytic hydrogen evolution and photoelectrochemical water splitting has been reviewed. The fabrication methods of defective TiO2 along with their structural, optical, and charge carrier properties have been introduced. It has appeared that the intrinsic point defects are a promising strategy to improve the performance of TiO2 for photocatalytic hydrogen production, and more efforts are stiH needed to improve the TiO2 performance for photocatalytic hydrogen production in this area of research. [ABSTRACT FROM AUTHOR]

In this research, pure titanium dioxide (TiO 2 ) and doped TiO 2 thin film layers were prepared using the spin coating method of titanium(iv) butoxide on a glass substrate from the sol-gel method and annealed at 500 °C. The effects on the structural and chemical properties of these thin films were then investigated. The metal doped TiO 2 thin film which exists as trivalent electrons consists of aluminium (Al), yttrium (Y) and gadolinium (Gd). The anatase phase of the thin films was observed and it was found that the crystal size became smaller when the concentration of thin film increased. The grain size was found to be 0.487 to 13.925 nm. The types of surface morphologies of the thin films were nanoporous, with a little agglomeration and smaller nanoparticles corresponding to Al doped TiO 2 , Y doped TiO 2 and Gd doped TiO 2 , respectively. The trivalent doping concentration of the thin films increased with a rising of thickness of the thin film. This can contribute to the defects that give advantages to the thin film when the mobility of the hole carriers is high and the electrons of Ti can move easily. Thus, Ti 3+ existed as a defect state in the metal doped TiO 2 thin film based on lattice distortion with a faster growth thin film that encouraged the formation of a higher level of oxygen vacancy defects., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)