Electronic properties and molecular electrostatic potential mapping of edge functionalized GQDs with ZnO, CuO, and TiO2

Abstract

Graphene quantum dots (GQDs) are a cutting-edge material that has excellent electrical, thermal, and mechanical characteristics, as well as minimal toxicity and powerful photoluminescence. These unique properties give GQDs the ability to be used in different electrical, optical, and optoelectronic applications. GQDs with hexagonal and triangular cuts with armchair and zigzag ends (ATRI, AHEX, ZTRI, and ZHEX) were decorated with different metal oxides such as ZnO, CuO, and TiO2. Metal oxides (MOs) were employed to tune the band gap and electrical properties of GQDs for usage in certain applications. The influence of functionalization on the GQDs electronic properties was examined utilizing HOMO–LUMO orbital distribution and molecular electrostatic potential (MESP) mapping calculations. The model structures were calculated using density functional theory (DFT: B3LYP/ LanL2DZ). The band gap energies of AHEX C42, ZHEX C54, ATRI C60, and ZTRI C46 were found to be 3.508, 2.886, 3.177, and 0.305 eV, respectively. The findings show that addition of MOs increases the total dipole moment (TDM) while decreasing the band gap energy ∆E. The most effective metal MO on GQDs band gap and electronic properties was TiO2, which enhanced the band gap energy ∆E for AHEX C42-TiO2, ZHEX C54-TiO2, ATRI C60-TiO2, and ZTRI C46-TiO2 to 0.391, 0.530, 0.287, and 0.250 eV, respectively. Accordingly, GQDs seem to be excellent for certain applications. Accordingly, GQDs functionalized with ZnO could be used for sensors, due to their increased responsiveness and energy gap variation while GQDs functionalized with TiO2 is excellent to be applied as optoelectronic materials.