DFT exploration of the sensing performance of Janus transition metal dichalcogenides (ASSe; A = Sc, Ti, Zr, Nb, Pd) monolayers for HCN, H 2 S, and NH 3 toxic gases

consistently shows strong interactions across all surfaces with significant charge transfer. Recovery time analysis reveals that gas molecules desorb from ScSSe and ZrSSe nanosheets within seconds and milliseconds, respectively, while TiSSe and NbSSe exhibit faster desorption at the microsecond scale. In contrast, PdSSe demonstrates ultrafast recovery in the picosecond range. Therefore, ScSSe, ZrSSe and NbSSe could be preferable candidates for gas sensing operation because of their favorable adsorption energies, electronic properties, quick recovery and high sensitivity.