Adsorption Efficiency and Gas Sensing of ScSeTe, TiSeTe, and ZrSeTe Nanosheets for Nitrogen-Based Toxic Gases (NO, NO ₂ , and NH ₃ ) through DFT Calculations

In this study, density functional theory (DFT) is employed to investigate the adsorption behavior of NO, NO2, and NH3 on Janus ScSeTe, TiSeTe, and ZrSeTe monolayer nanosheets. The asymmetric Se–M–Te configuration gives rise to distinct adsorption sites, leading to site and material dependent interaction strengths. The calculated adsorption energies span −0.147 to −0.441 eV for ScSeTe, −0.130 to −0.306 eV for TiSeTe, and −0.004 to −0.703 eV for ZrSeTe. The electronic response upon gas adsorption is examined through the density of states, band structure, charge density difference, electron localization function, and reduced density gradient (RDG) analyses. RDG analysis confirms that the gas molecules interact with the nanosheets primarily through weak van der Waals forces, identifying ZrSeTe as the most responsive material among the studied monolayers. Charge transfer analysis indicates that NO and NH3 donate electrons to the monolayers, whereas NO2 acts as an electron acceptor. Recovery time calculations demonstrate that desorption kinetics are strongly governed by adsorption strength and temperature. At 500 K, NO2 on TiSeTe shows a rapid recovery time of 4.05 × 10–5 ns, while more strongly bound configurations exhibit comparatively longer recovery times. In addition, gas adsorption induces measurable changes in the work function as well as electronic responses in the Janus nanosheets. Therefore, among the three nanosheets, ZrSeTe shows the highest interaction toward the three gases.