First-Principles Investigation of Adsorption Behaviors and Electronic, Optical, and Gas-Sensing Properties of Pure and Pd-Decorated GeS Monolayers.

The extensive applications of two-dimensional (2D) transition metal disulfides in gas sensing prompt us to explore the adsorption, electronic, optical, and gas-sensing properties of the pure and Pd-decorated GeS monolayers interacting with NO, NO, CO, CO, SO, NH, HS, HCN, HF, CH, N, and H gases by using first-principles methods. Our results showed that the pure GeS monolayer is not appropriate to develop gas sensors. The stability of the Pd-decorated GeS (Pd-GeS) monolayer was determined by binding energy, transition state theory, and molecular dynamics simulations, and the Pd decoration has a significant effect on adsorption strength and the change in electronic properties (especially electrical conductivity). The Pd-GeS monolayer-based sensor has relatively high sensitivity toward NO and NO gases with moderate recovery time. In addition, the adsorption of NO and NO can conspicuously change the optical properties of the Pd-GeS monolayer. Therefore, the Pd-GeS monolayer is predicted to be reusable and a highly sensitive (optical) gas sensing material for the detection of NO and NO.