Synthesis of green-photoluminescent single layer graphene quantum dots: Determination of HOMO and LUMO energy states

Low-cost and high-yield green-photoluminescent single layer graphene quantum dots (SLGQDs) synthesized with only DI water and glucose as precursor using a hydrothermal method. Atomic force microscopy proved that the graphene quantum dots are single layers and transmission electron microscopy images showed that the average width of SLGQDs is about 8 nm and optical characterization revealed that SLGQDs are highly photoluminescent. Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the SLGQDs against vacuum determined using a cyclic voltammetry technique, and energy band gap was obtained ∼ 2.9 and 3.1 eV from cyclic voltammetry and optical measurements, respectively.