WO₃–TiO₂ nanostructured thin film prepared by in situ hydrothermal method as the sensing material for liquid petroleum gas (LPG) detection

Titanium dioxide (TiO₂) and tungsten trioxide (WO₃) are considered technologically important materials in many research areas including energy and the environment due to their excellent semiconducting properties, chemical stability, and relatively low cost. TiO₂, WO₃, and WO₃–TiO₂ composite thin films were prepared on Fluorine Doped Tin Oxide (FTO) glass substrate by in situ hydrothermal method. Titanium Isopropoxide (C₁₂H₂₈O₄Ti) and Sodium Tungstate Dehydrate (Na₂WO₄·2H₂O) were used as the starting material for the preparation of TiO₂, and WO₃ thin films respectively. The structure and morphology of the thin films were characterized by using different techniques including XRD, and SEM. According to the results, the thin films’ particle size ranges from a few microns to a hundred nanometers. XRD results showed that the phase composition of composite samples is a mixture of TiO₂ and WO₃ and its average grain size is reduced with the incorporation of TiO₂. Band gap values of prepared TiO₂, WO₃, and WO₃–TiO₂ composite films are found to be 3.66 eV, 2.52 eV, and 3.55 eV respectively. Gas sensitivity towards Liquid Petroleum gas (LPG) was measured for three different films: TiO₂, WO₃, and WO₃–TiO₂. According to the results, the prepared composite WO₃–TiO₂ films showed a higher response than the pristine TiO₂ and WO₃ towards the LPG. Smaller size of the grains and uniform distribution of grains in the composite which provides a more active site for the gas sensing reaction is positively affected for the enhancement of gas sensitivity of WO₃–TiO₂ composite.