Janus AsP monolayer: A promising 2D platform for NO and NO2 gas sensing

Abstract

Two-dimensional Janus AsP monolayer has attracted considerable interest due to its structural asymmetry and tunable electronic properties. In this work, the gas sensing performance of Janus AsP monolayer toward N2, CO2, H2O, NO, and NO2 was systematically investigated using first-principles calculations combined with nonequilibrium Green’s function simulations. The calculation reveals weak physical interactions with common background gases (N2, CO2, and H2O), whereas NO and NO2 molecules exhibit stronger adsorption, significant charge transfer, and pronounced band gap modulation. In particular, NO2 exhibits a strong physisorption energy of –0.69 eV, which surpasses that of conventional AsP and even its complex doped counterparts, thereby underscoring its potential for reversible sensing applications. Notably, the adsorption of the NO and NO2 molecules induces spin polarization in the substrate, resulting in asymmetric spin-resolved density of states and the formation of new impurity states near the Fermi level. Electronic transport calculations show enhanced electrical conductivity and substantial I–V response for NO and NO2 adsorption, highlighting both sensitivity and potential selectivity. The reversible nature of the physical adsorption, confirmed by charge density difference and electron localization function analyses, further supports practical sensor applications. These findings demonstrate that Janus AsP is a promising candidate for high-performance nitrogen oxide detection and provide theoretical guidance for the design of next-generation 2D material-based gas sensors.