First-principles investigations of As-doped tetragonal boron nitride nanosheets for toxic gas sensing applications

Pristine and arsenic-doped tetragonal boron nitride nanosheets (BNNS and As-BNNS) have been reported as potential candidates for toxic gas sensing applications. We have investigated the adsorption behavior of BNNS and As-BNNS for CO₂, H₂S, and SO₃ gas molecules using first-principles density functional theory (DFT). Both BNNS and As-BNNS possess negative cohesive energies of -8.47 and -8.22 eV, respectively, which indicates that both sheets are energetically stable. Successful adsorption is inferred from the negative adsorption energy and structural deformation in the vicinity of the adsorbent and adsorbate. As-doping results in a significant increase in adsorption energies from -0.094, -0.175, and -0.462 eV to -2.748, -2.637, and 3.057 eV for CO₂, H₂S and SO₃ gases, respectively. Due to gas adsorption, the electronic bandgap in As-BNNS varies by approximately 32% compared to a maximum of 24% in BNNS. A notable fluctuation in the energy gap and electrical conductivity is seen, with ambient temperature being the point of maximal sensitivity. For SO₃, the maximum charge transfer during adsorption in BNNS and As-BNNS is determined to be 0.08|<i>e</i>| and 0.25|<i>e</i>|, respectively. Due to the interaction with gases, all structures exhibit an extremely high absorption coefficient on the order of 10⁴ cm^-1 with minimal peak shifting. Additionally, doping an As atom on BNNS' surface remarkably improved its ability to sense CO₂, H₂S, and SO₃ gasses.