Two-dimensional Janus X2STe (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, NO2, NH3, and O2 on two-dimensional (2D) Janus group-III materials, specifically Al2XY and B2XY. 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 NO2 as a prominent adsorbate, emphasizing the Te surface of 2D Al2STe and B2STe materials as particularly adept for NO2 detection, based on considerations of adsorption energy, height, and charge transfer. Additionally, the study underscores the heightened sensitivity of work function changes in the B2STe material. The adsorption properties of all gas molecules, except for NO2, on both materials were determined to be physical. Upon adsorption of the NO2 gas molecule onto the B2STe 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.

Realization of efficient and selective NO and NO2 detection via surface functionalized h-B2S2 monolayer

In the ever-growing field of two-dimensional (2D) materials, the boron-sulfide (B2S2) monolayer is a promising new addition to MoS2-like 2D materials, with the boron (a lighter element) pair (B2 pair) having similar valence electrons to Mo. Herein, we have functionalized the h-phase boron sulfide monolayer by introducing oxygen atoms (Oh-B2S2) to widen its application scope as a gas sensor. The charge carrier mobilities of this system were found to be 790 × 102 cm2 V-1 s-1 and 32 × 102 cm2 V-1 s-1 for electrons and holes, respectively, which are much higher than the mobilities of the MoS2 monolayer. The potential application of the 2D Oh-B2S2 monolayer in the realm of gas sensing was evaluated using a combination of density functional theory (DFT), ab initio molecular dynamics (AIMD), and non-equilibrium Green's function (NEGF) based simulations. Our results imply that the Oh-B2S2 monolayer outperforms graphene and MoS2 in NO and NO2 selective sensing with higher adsorption energies (-0.56 and -0.16 eV) and charge transfer values (0.34 and 0.13e). Furthermore, the current-voltage characteristics show that the Oh-B2S2 monolayer may selectively detect NO and NO2 gases after bias 1.4 V, providing a greater possibility for the development of boron-based gas-sensing devices for future nanoelectronics.

First-principles study on α/β/γ-FeB6 monolayers as potential gas sensor for H2S and SO2

CONTEXT

The adsorptions of toxic gases SO2 and H2S on 2D α/β/γ-FeB6 monolayer were investigated using density functional theory calculations. To analyze the interaction between gas molecule H2S/SO2 and α/β/γ-FeB6 monolayer, we calculated adsorption energy, adsorption distance, Mullikan charge, charge density difference, band structure, the density of states, work function, and theoretical recovery time. The adsorption energies show that H2S/SO2 is chemisorbed on α/β-FeB6 while H2S/SO2 is physiosorbed on γ-FeB6 monolayer. As a result, γ-FeB6 has a short recovery time for H2S (5.71×10-8 s)/SO2 (1.94×10-5 s) due to modest adsorption. Therefore, γ-FeB6 may be a promising candidate for reusable H2S/SO2 sensors at room temperature. Although H2S is chemisorbed on α/β-FeB6, as the working temperature rises to 500 K, the recovery time of α/β-FeB6 for H2S can decrease to 1.13×10-1 s and 2.08×10-1 s, respectively, which are well within the detectable range. So, α/β-FeB6 monolayer also may be a good candidate for H2S gas sensor.

METHODS

Calculations were performed at GGA-PBE/DNP level using the Dmol3 module implemented in the Material Studio 2018 software package.