Electrical and work function-based chemical gas sensors utilizing NC3 and graphene combination

Abstract

Research has been conducted on the potential practical uses of heterostructures made of graphene and carbon nitride (NC₃) following their successful synthesis. The remarkable gas sensing properties of these 2D nanosheets have captured significant interest, attributed to distinctive electronic characteristics and exceptional surface-to-volume ratio that are resulted from combination of NC₃ and graphene. In this study, we present a detailed analysis of electronic and structural features of pristine NC₃ and graphene (PG), and their in-plane heterostructures using first-principles density functional theory. Our investigation utilizes the B3LYP and dispersion-corrected van der Waals (vdW) functional WB97XD, along with 6-311G (d, p) basis set. Our findings indicate that the nanosheets we anticipated exhibit robust structural stability, characterized by a desirable cohesive energy. Furthermore, we observed a gradual increase in the bandgap as the concentration of N–C in the nanosheets increases. Additionally, we investigated the adsorption characteristics of these heterostructures towards toxic gas molecules such as SO₂ and CO. Among the studied heterostructures, GNC₃I demonstrated higher adsorption energy (E_ads), with values of approximately −0.283 and −0.491 eV when exposed to SO₂ and carbon monoxide gas molecules respectively. Electronic characteristics, including LUMO and HOMO energy values, energy gap (E_g) between HOMO and LUMO, work function, Fermi level, and conductivity, underwent notable modifications upon SO₂ gas adsorption over nanosheets, except for PG. However, these parameters remained relatively unchanged following carbon monoxide adsorption. Natural bond orbital (NBO) and Mulliken charge analysis demonstrates that there is a transfer of charge from gas molecules to nanosheets. Although nanosheets exhibit slightly higher adsorption energy (E_ads) values for CO gas compared to SO₂ gas, various assessments, including molecular electrostatic potential (MEP) mapping, electronic properties, and charge transfer (CT) analysis, suggest that these nanosheets are superior sensors for detecting SO₂ gas rather than carbon monoxide gas molecules.