Biaxial Strain Engineering for High-Performance Monolayer GeSe Sensors toward Nitrogen-Containing Toxic Gases

Strain engineering offers a powerful route to tailor the chemical reactivity and electronic response of two-dimensional GeSe, yet its impact on gas-sensing selectivity remains insufficiently understood. Here, we combine density functional theory and the nonequilibrium Green's function (NEGF) method to reveal a strain-governed sensing mechanism in monolayer GeSe toward nitrogen-containing pollutants (NO, NO₂, and NH₃). Pristine GeSe exhibits intrinsic selectivity for NO₂, where adsorption triggers a semiconductor-to-metal transition, whereas interactions with NO and NH₃ are comparatively weak. Remarkably, a modest 4% biaxial compressive strain transforms GeSe into a fully discriminative sensing platform: NO₂ adsorption produces a pronounced conductivity increase via metallic switching, NO yields strongly spin-polarized currents approaching a 100% filtering efficiency, and NH₃ induces only minimal electronic perturbation. These distinct response signatures arise from strain-enhanced gas adsorption, bandgap renormalization, and reconfigured transport pathways. Recovery-time analysis further reveals rapid desorption, confirming the practical recyclability. Our findings demonstrate that biaxial strain can activate distinct electronic responses─metallicity, spin polarization, and inertness─to achieve precise differentiation of chemically similar nitrogen-containing species, establishing strained GeSe as a versatile and tunable platform for next-generation gas sensing.