Two-dimensional Janus XSTe (X = B, Al) monolayers: the effect of surface selectivity and adsorption of small gas molecules on electronic and optical properties.

This investigation delves into the adsorption characteristics of CO, NO, NO, NH, and O on two-dimensional (2D) Janus group-III materials, specifically AlXY and BXY. The examination covers adsorption energies and heights, diverse adsorption sites, and molecular orientations. Employing first-principles analysis, a comprehensive assessment of structural, electronic, and optical properties is conducted. The findings highlight NO as a prominent adsorbate, emphasizing the Te surface of 2D AlSTe and BSTe materials as particularly adept for NO detection, based on considerations of adsorption energy, height, and charge transfer. Additionally, the study underscores the heightened sensitivity of work function changes in the BSTe material. The adsorption properties of all gas molecules, except for NO, on both materials were determined to be physical. Upon adsorption of the NO gas molecule onto the BSTe Janus material, it was observed that the material exhibited weak chemical adsorption behavior, which was confirmed by the adsorption energy, larger band gap change, electron localization function, work function changes and charge transfer from the material. This research provides valuable insights into the gas-sensing potential of 2D Janus materials.