Noble metal-anchored Janus Ga₂SSe monolayers for toxic gas sensing: first-principles investigation

Industrial production processes discharge substantial quantities of hazardous gases, posing severe risks to both environmental safety and human well-being. Therefore, developing high-performance gas sensors that enable accurate detection of these dangerous species is urgently needed. Using density functional theory (DFT) calculations, this study explores the adsorption and gas-sensing performance of Ir-, Pt-, and Au-doped Ga₂SSe monolayers toward six toxic gases (NO, NO₂, SO₂, CO, H₂S, and NH₃). It is found that Ir-Ga₂SSe, Pt-Ga₂SSe, and Au-Ga₂SSe all exhibit excellent structural stability, and the dopant atoms significantly enhance the capture capability of Ga₂SSe toward the target gases. Specifically, Ir-Ga₂SSe and Pt-Ga₂SSe exhibit strong chemisorption toward all six gases, while Au-Ga₂SSe displays strong adsorption toward NO, NO₂, and SO₂ molecules. These findings are further confirmed by electronic structure analyses, including charge density difference (CDD) and partial density of states (PDOS). Moreover, a comprehensive analysis of band gap variation and sensing responses reveals that Ir-Ga₂SSe possesses outstanding sensitivity toward all six target gases, whereas Pt-Ga₂SSe and Au-Ga₂SSe show excellent response characteristics toward NO, NO₂, H₂S, and NH₃. Finally, the recovery time calculations indicate that the Au-Ga₂SSe monolayer is well suited for sensing NO, SO₂, and NH₃ at ambient temperature, whereas Pt-Ga₂SSe is reusable for detecting all six toxic gases under elevated temperatures. Therefore, this study serves as a basis for designing novel gas sensors aimed at detecting industrial toxic gases.