Dopant-driven electronic coupling and fast gas sensing in gold-boron co-doped Si/MoS2 heterostructures: a first-principles study.

Developing gas sensors that combine ultrahigh sensitivity, chemical selectivity, and rapid recovery is crucial for next-generation environmental and industrial monitoring technologies. Here, density functional theory is employed to unravel the structural, electronic, and interfacial mechanisms governing CO and CO2 detection on pristine, single-doped, and AuB co-doped silicene/MoS2 heterostructures. Phonon and formation-energy analyses confirm that AuB co-doping markedly enhances thermodynamic and dynamic stability while inducing a semiconductor-to-metal transition through hybridized Au d, B p, and Si p states near the Fermi level. The resulting metallic character enables efficient carrier delocalization and rapid electronic response. Adsorption, charge-density-difference, and periodic energy decomposition analyses reveal distinct interaction pathways: CO adsorption arises primarily from orbital hybridization between Au d and C p orbitals, whereas CO2 binding is dominated by electrostatic attraction and B p-O p coupling. Balanced electrostatic and orbital components, together with moderate Pauli repulsion, ensure strong yet reversible adsorption, promoting fast charge transfer without surface trapping. The AuB co-doped interface achieves the highest performance, exhibiting charge transfer up to 0.0104e and recovery times as short as 0.050 ns, surpassing most reported two-dimensional sensors. These ultimate effects of Au-induced polarization and B-mediated electron acceptance establish a tunable electronic platform that simultaneously enhances sensitivity, selectivity, and reusability. This work provides atomistic insight into dopant-controlled interfacial chemistry and charts a rational pathway for designing multifunctional 2D heterostructure sensors with rapid, reliable, and energy-efficient gas detection.