Resistive nanostructured WO 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. WO (WO), 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 WO-based gas sensors using strategies such as morphology engineering, doping, decoration, formation of composites or their combination, the fabrication of high-performance WO gas sensors is feasible. Herein, we present the gas-sensing features of pristine WO, doped WO, decorated WO and composite-based WO sensors. Moreover, focusing on the sensing mechanism of WO sensors, this review provides an in-depth understanding on the working principles of the sensing of toxic gases using WO.