Computational Study of Janus Transition Metal Dichalcogenide Monolayers for Acetone Gas Sensing

Recently, Janus two-dimensional (2D) transition metal dichalcogenides (TMDs) have been widely investigated and have provided exciting prospects in many fields such as photoelectric materials, photocatalysis, and gas sensors. In this study, we performed density functional theory (DFT) calculations to study the sensitivity of four volatile organic compounds (VOCs), including acetone, methanol, ethanol, and formyl aldehyde, over pristine 2D TMDs and 2D Janus TMD monolayers. We found that MoS₂, Janus MoSSe, and Janus MoSTe demonstrated greater sensitivity toward acetone than other VOCs. Furthermore, the band gap values of the Janus MoSSe and Janus MoSTe monolayers dramatically changed after acetone adsorption on their sulfur layers, which was quite larger than the band gap change after acetone adsorption on the MoS₂ monolayer. This result also leads to the extremely large conductivity change of Janus MoSSe and Janus MoSTe after sensing acetone. Hence, Janus MoSSe and Janus MoSTe monolayers show much higher sensitivity toward acetone in comparison with the pristine MoS₂ monolayer. Finally, our finding indicates that Janus MoSSe and Janus MoSTe monolayers can be proposed as ultrahigh-sensitivity 2D TMD materials for acetone sensors.