Ag-doped P3S2-I monolayers: selective and robust toxic gas detection in ambient environments

Abstract

The sensing capabilities of pristine and Ag-doped P₃S₂-I (Ag-PS) monolayers toward toxic gases such as SO₂, CO, HCN, and H₂S were investigated using DFT simulations. Intrinsic P₃S₂-I exhibits semiconductor properties but shows limited gas adsorption capacity due to low adsorption energies (E_ad). In contrast, Ag-doping induces metallization (bandgap closure) and enhances surface reactivity. Ag-PS demonstrates strong chemisorption of all target gases (E_ad ranging from −0.682 to −1.149 eV), accompanied by the reopening of a direct bandgap (1.269–1.398 eV). Variations in work function and optical properties further support Ag-PS’s potential for selective gas detection. Notably, Ag-PS maintains selectivity even in humid/ambient conditions (with negligible interference from O₂, H₂O, CO₂, and N₂), affirming its utility as a robust detector and scavenger for toxic gases. These findings highlight Ag-PS as a promising candidate for environmental monitoring systems, leveraging doping-enhanced electronic and optical responsiveness for gas sensing applications.