Resistive gas sensors for the detection of NH 3 gas based on 2D WS 2 , WSe 2 , MoS 2 , and MoSe 2 : a review

Transition metal dichalcogenides (TMDs) with a two-dimensional (2D) structure and semiconducting features are highly favorable for the production of NH 3 gas sensors. Among the TMD family, WS 2 , WSe 2 , MoS 2 , and MoSe 2 exhibit high conductivity and a high surface area, along with high availability, reasons for which they are favored in gas-sensing studies. In this review, we have discussed the structure, synthesis, and NH 3 sensing characteristics of pristine, decorated, doped, and composite-based WS 2 , WSe 2 , MoS 2 , and MoSe 2 gas sensors. Both experimental and theoretical studies are considered. Furthermore, both room temperature and higher temperature gas sensors are discussed. We also emphasized the gas-sensing mechanism. Thus, this review provides a reference for researchers working in the field of 2D TMD gas sensors.