A green approach to synthesis disordered TiO2 for Organic Compound Sensing

Over the past decades, TiO2 nanomaterials have been receiving tremendous attention due to its applications in energy harvesting and storage devices, including photocatalytic hydrogen generation, environmental pollution removal, and Organic Compound Sensing. One of the methods used to increase quantum efficiency is to introduce disordered titanium dioxide nanoparticles. These nanomaterials are an excellent light absorber because they can absorb sunlight from the ultraviolet to the infrared. The presence of defects such as self-doped Ti3+ ions, Ti-H and Ti-OH groups, oxygen vacancies, and surface disordered can extend light absorption, decrease electron-hole recombination, and improve photocatalytic properties. In this case, disordered TiO2 is prepared by addition of ascorbic acid to the TiO2, that prepared by Sol-gel method, as a reductant. The structural phases of the prepared nanoparticles are studied with X-ray diffraction. Fig.1 demonstrates the diffraction pattern of reduced TiO2 and TiO2. Most of the diffraction peaks of two samples matched with the diffraction peaks of anatase TiO2 (JCPDS 21-1272). It was observed that the diffraction peaks of reduced TiO2 exhibited a larger linewidth than TiO2 as its crystallinity is decreased. Besides diffraction peaks shift to the higher diffraction angles in disordered TiO2, it confirms that there is some defect in its crystal structure. These defects can trap charge carriers, in order to limit their recombination. As shown in Fig.2, the reduced TiO2 has significant absorption in the visible-light region, because of the generation of Ti3+ and oxygen vacancy while the TiO2 has no absorption in the visible-light region. Disordered TiO2 can be utilized as Organic Compound Sensors, which can degrade and ultimately detect various kinds of organic compounds under the visible light.