Effect of doping graphene quantum dots with metalloid dopants in the presence of zigzag and armchair edge configuration.

Graphene quantum dots (GQDs) are known as promising zero-dimensional nanomaterials due to their tunable electronic and optical properties arising from quantum confinement and edge effects. In this work, a comprehensive density functional theory investigation is carried out to explore the influence of semi-metal doping and edge configuration on the structural, electronic, chemical reactivity, and optical properties of hexagonal graphene quantum dots. Two edge types, zigzag and armchair, are considered for pristine GQDs and GQDs doped with fourth group (Si, Ge) and fifth group elements (As, Sb). All geometries are fully optimized using the CAM-B3LYP and ωB97XD functionals via DFT, and the electronic excitations are analyzed via time-dependent density functional theory (TD-DFT). The results exhibit that heteroatom doping induces significant structural distortion due to the larger covalent radii of dopants and their specific valence shell electron configuration compared to carbon. Electronic structure analysis shows that both dopant type and edge configuration strongly modulate the HOMO–LUMO gap and density of states. In particular, doping the GQDs with fourth group elements —especially with zigzag edges—exhibit a pronounced reduction in bandgap, chemical hardness, and an enhancement in dipole moment and electrophilicity index, indicating improved charge-transfer capability and electronic reactivity. In contrast, arsenic- and antimony-doped systems introduce more localized electronic states, higher electrophilicity, and increased structural strain, because of their different valence shell electron configuration compared with carbon, suggesting carrier trapping tendencies that are less favorable for electronic transport applications.