Boron-doped graphene topological defects: unveiling high sensitivity to NO molecule for gas sensing applications.

Global air quality has deteriorated significantly in recent years due to large emissions from the transformation industry and combustion vehicles. This issue requires the development of portable, highly sensitive, and selective gas sensors. Nanostructured materials, including defective graphene, have emerged as promising candidates for such applications. In this work, we investigated the B-doped topological line defect in graphene as a sensing material for various gas molecules (CO, CO2, NO, and NH3) based on a combination of density functional theory and the non-equilibrium Green's function method. The electronic transport calculations reveal that the electric current can be confined to the line defect region by gate voltage control, revealing highly reactive sites. The B-doped topological line defect is metallic, favoring the adsorption of NO and NH3 over CO and CO2 molecules. We notice changes in the conductance after gas molecule adsorption, producing a sensitivity of 50% (16%) for NO (NH3). In addition, the recovery time for nitride gases was calculated for different temperatures and radiation frequencies. At 300 K the ultraviolet (UV) has a fast recovery time compared to the visible (VIS) one by about two orders of magnitude. This study gives an understanding of how engineering transport properties at the microscopic level (by topological line defect and chemical B-doping) leads to promising nanosensors for detecting nitride gas.

C-doping anisotropy effects on borophene electronic transport.

The electronic transport anisotropy for different C-doped borophene polymorphs (ß12andχ3) was investigated theoretically combining density functional theory and non-equilibrium Green's function. The energetic stability analysis reveals that B atoms replaced by C is more energetically favorable forχ3phase. We also verify a directional character of the electronic band structure on C-doped borophene for both phases. Simulated scanning tunneling microscopy and also total density of charge confirm the directional character of the bonds. The zero bias transmission forß12phase atE-EF= 0 shows that C-doping induces a local current confinement along the lines of doped sites. TheI-Vcurves show that C-doping leads to an anisotropy amplification in theß12than in theχ3. The possibility of confining the electronic current at an specific region of the C-doped systems, along with the different adsorption features of the doped sites, poses them as promising candidates to highly sensitive and selective gas sensors.