Hydrothermal synthesis and characterization of nanostructured titanium monoxide films

Abstract

At the present time, the formation of titanium monoxide (TiOx) two dimensional (2D) species with distinct composition, size, shape, and a significantly reduced bandgap (Eg) value compared to TiO2 is of great scientific and practical importance. This paper describes our findings investigating Ti surface oxidation for the formation of TiOx 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 TiO0.84, 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 Eg of anatase TiO2 and a surprising 70% porosity determined via simulation of experimental reflection plots. It is anticipated that this unique TiOx nanomaterial will pave the way for new investigations and applications.