One step synthesis of graphene quantum dots, graphene nanosheets and carbon nanospheres: investigation of photoluminescence properties

Abstract

Single layer graphene quantum dots (GQDs), graphene nanosheets (GNSs), and carbon nanospheres (CNSs) were synthesized by an easy, environment-friendly, and low-cost hydrothermal process and the effect of the hydrothermal reaction time on their structural and photoluminescence properties was studied. Four different kinds of samples were prepared only using glucose and deionized water. By varying the hydrothermal reaction time, we obtained excitation-dependent photoluminescent GQDs and GNSs with different photoluminescence quantum yields (PLQYs) and CNSs without any photoluminescence. Atomic force microscopy images showed that the synthesized GQDs are single or double-layered. Transmission electron microscopy (TEM) images indicated that the sizes of the samples are distributed between the small graphene quantum dots (GQDs ≤ 10 nm) for reaction time of 2 h and the homogeneous carbon nanospheres (CNSs ∼ 560 nm) for reaction time of 30 h. Finally, it has shown that the optimized sample exhibits the high PLQY of 22.7% for reaction time of 8 h.