Molecular insights into NO2 sensing through doped armchair graphene nanoribbon

Abstract

An escalating concern from the Nitrogen dioxide (NO₂) molecules induces respiratory issues, necessitating the development of highly sensitive sensors. In response to this pressing issue, the research proposed a novel methodology leveraging hydrogen (H) passivated armchair graphene nanoribbons (ArGNR). These nanoribbons are successively substituted with reactive non-metal phosphorus (P) and post-transition metals (aluminum (Al) and gallium (Ga)) to enhance the sensitivity of the ArGNR to the NO₂ molecules. The introduction of this dopant increases the density of adsorption sites, leading to a higher interaction with the NO₂ molecule. Moreover, to ensure accuracy, the electronic properties are rigorously examined through the density functional theory (DFT) with spin polarization and unpolarization calculation, within the linear combination of atomic orbitals (LCAO) framework. Initially, the investigation focuses on a width-3 ArGNR, substituted with P at all the carbon (C) sites, and identifies an optimal site for the dopant incorporation. Subsequently, the Al and Ga substitution at these sites results in a notable 10–20 % increase in adsorption energy (E_ads) compared to the P-doped ArGNR. In addition, the research extended to the wider ArGNR (widths of 4 and 5 C atoms), where the introduction of dopants further influences the electronic properties. The results demonstrate that the Al-doped width-3 ArGNR exhibits optimal E_ads and increased desorption (r_des) of −3.32 eV and 0.17 eV, following NO₂ adsorption, respectively. The band gap (E_G) also delineates a decrement of 42.5 % post-adsorption, signifying a high sensitivity. Furthermore, it is discerned that Al manifests as a promising dopant in ArGNR for sensing.