An ab-initio investigation of transition metal-doped graphene quantum dots for the adsorption of hazardous CO2, H2S, HCN, and CNCl molecules

The quantum confinement and size effects make graphene quantum dots (GQDs) remarkable candidates for sensing applications. Gas molecules can easily be adsorbed on GQDs because of their large specific areas and exposed edges. This computational work concerns the adsorption performance of pristine and transition metal [chromium (Cr) or nickel (Ni)]-doped coronene GQD to hazardous gases carbon dioxide (CO2), hydrogen sulfide (H2S), hydrogen cyanide (HCN), and cyanogen chloride (CNCl), along with structural properties such as bond length and angle, electronic properties including molecular orbital analysis, natural bond orbital and Mulliken charge analysis, spectroscopic properties of infrared and ultraviolet spectra, quantum theory of atoms in molecules with non-covalent interaction analysis, and sensing properties of recovery time, work function, and sensing response. As pristine GQDs show poor gas adsorption, doping with Cr and Ni enhance performance. The results of Cr-doped coronene GQD indicate that the gas molecules have strong interaction with GQDs as the computed adsorption energies are highly negative (-3.56, -3.81, -4.02, and -4.81 eV). Since the computed recovery times are extremely long, the Cr-doped GQDs can be used as removers of CO2, H2S, HCN, and CNCl gas molecules from specific environments. In the case of Ni-doped GQDs, only the interaction with CNCl yields chemisorption, with adsorption energy of -0.83 eV. However, the short recovery time (9.36 ms-93.6 s) indicates its potential candidature as a CNCl sensor.