DFT-Based Insights into the Functionalization of MoSe 2 Monolayers via Substitutional Doping for Enhanced Gas Detection

To enhance safety in industrial processes and prevent dangerous exposures to hazardous gases such as H 2, H 2 S, and HCN, early detection and monitoring are essential. Using Density Functional Theory, we investigated the D-MoSe 2 (D-Pt, Ir, and Os) monolayers as sensing materials and analyzed their structures, electronic properties, and gas-sensing behaviors. The absence of imaginary phonon bands confirms the dynamical stability of the substitutionally doped monolayers. Their band gaps decrease as new energy states form, and charges are redistributed, improving the surface for better gas adsorption. The Ir-MoSe 2 monolayer interacts highly with all three gases and yields adsorption energies of −0.59 eV for H 2, −1.17 eV for H 2 S, and −1.01 eV for HCN. The substantial charges donated from the gas to the material are 0.094, 0.267, and 0.134 e. Followed by which the Pt-MoSe 2 monolayer also chemically interacts with H 2 S and HCN gases with significant charge transfer and adsorption energies. The doped monolayers exhibit profound changes in their sensing and electronic properties, as observed through changes in band structure, density of states, electron density differences, and electron localization function-based interactions. The work function changes for Pt-MoSe 2 indicate selective detection (−0.27 and −0.34 eV), and for the Ir-MoSe 2 monolayer, it shows nearly identical changes (−0.35 and −0.34 eV) for H 2 S and HCN gases. The Pt-MoSe 2 monolayer releases HCN gas within 12.79 s at 323 K, enabling reliable, repeatable sensing. Also, the Ir-MoSe 2 monolayer recovers HCN gas in 5.32 s at 400 K. Therefore, the Pt- and Ir-MoSe 2 monolayers are acceptable choices for efficient gas-sensing applications, enabling the rational design of a nanosensor with sensitive and selective detection of targeted hazardous gases.