Hydrothermal synthesis and characterization of nanostructured titanium monoxide films

Abstract

At the present time, the formation of titanium monoxide (TiO_x) two dimensional (2D) species with distinct composition, size, shape, and a significantly reduced bandgap (E_g) value compared to TiO₂ is of great scientific and practical importance. This paper describes our findings investigating Ti surface oxidation for the formation of TiO_x films possessing a densely-packed nanoplatelet morphology and a low bandgap value. This goal was herein achieved by the hydrothermal treatment of the Ti surface in selenious acid solution kept at a slightly alkaline pH. Furthermore, the nanoplatelet design not typical for TiO₂ porous films was created by this method for the first time. The formation of titanium monoxide, particularly TiO_0.84, as a major crystalline phase, was verified by XRD and confirmed by EPR investigations. It is worth noting that these nanoplatelet-shaped films with a thickness of 0.1–0.25 μm exhibited a very large shift of their light absorption threshold, down to 1.29 eV, compared to the E_g of anatase TiO₂ and a surprising 70% porosity determined via simulation of experimental reflection plots. It is anticipated that this unique TiO_x nanomaterial will pave the way for new investigations and applications.