Resistive nanostructured W₁₈O₄₉ gas sensors: an overview

The detection of toxic gases by resistive gas sensors, which are mainly fabricated using semiconducting metal oxides, is of importance from a safety point of view. These sensors have outstanding electrical and sensing properties as well as are inexpensive. W₁₈O₄₉ (WO_2.72), which is a non-stoichiometric tungsten oxide, possesses abundant oxygen vacancies, which are beneficial for the adsorption of oxygen gas molecules and act as sites for sensing reactions. Thus, through the rational design of W₁₈O₄₉-based gas sensors using strategies such as morphology engineering, doping, decoration, formation of composites or their combination, the fabrication of high-performance W₁₈O₄₉ gas sensors is feasible. Herein, we present the gas-sensing features of pristine W₁₈O₄₉, doped W₁₈O₄₉, decorated W₁₈O₄₉ and composite-based W₁₈O₄₉ sensors. Moreover, focusing on the sensing mechanism of W₁₈O₄₉ sensors, this review provides an in-depth understanding on the working principles of the sensing of toxic gases using W₁₈O₄₉.