Insights into the Effects of Co-doping on the Electronic Properties of Armchair Graphene Nanoribbon-based NO₂ Gas Sensors

Nitrogen dioxide (NO₂) emissions from numerous sources pose a significant threat to health, necessitating the development of highly sensitive electronic sensors. In response to this issue, this study investigates the influence of NO₂ molecules on a hydrogen (H)-passivated doped/undoped armchair graphene nanoribbon (ArGNR). The electronic properties are examined using density functional theory (DFT) within the framework of a linear combination of atomic orbitals (LCAO) calculator, combined with the nonequilibrium Green’s function (NEGF). The modeling focuses on the impact of doping with manganese (Mn) and co-doping of Mn with group V elements [nitrogen (N), phosphorus (P), and arsenic (As) atoms] on the electronic properties of the ArGNR. The introduction of the Mn element introduces spin–polarization that can influence the adsorption behavior of the target molecule, enhancing the sensitivity and selectivity of ArGNR. Moreover, the results show that the co-doping in ArGNR significantly enhances the bandgap opening compared to individual doping, resulting in improved sensitivity towards the NO₂ molecules. Subsequently, compared to Mn-P- and Mn-As-co-doped ArGNR, the Mn-N-co-doped ArGNR exhibits binding energy (E_B) of 308.47 eV, high chemisorption of −2.92 eV, desorption of 39.69%, notable variations in bandgap (E_G) of 16.5%, and a large current variation by a factor of 2.64 times following NO₂ adsorption, indicating improved conductivity. These findings highlight the potential of the Mn-N-co-doped ArGNR as a leading material for NO₂ sensing.