Bottom-Up Fabrication of Single-Layered Nitrogen-Doped Graphene Quantum Dots through Intermolecular Carbonization Arrayed in a 2D Plane.

A single-layered intermolecular carbonization method was applied to synthesize single-layered nitrogen-doped graphene quantum dots (N-GQDs) by using 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) as the only precursor. In this method, the gas produced in the pyrolysis of TATB assists with speeding up of the reactions and expanding the layered distance, so that it facilitates the formation of single-layered N-GQDs (about 80 %). The symmetric intermolecular carbonizations of TATB arrayed in a plane and six nitrogen-containing groups ensure small, uniform sizes (2-5 nm) of the resulting products, and provide high nitrogen-doping concentrations (N/C atomic ratio ca. 10.6 %). In addition to release of the produced gas, TATB is almost completely converted into aggregated N-GQDs; thus, relatively higher production rates are possible with this approach. Investigations show that the as-produced N-GQDs have superior fluorescent characteristics; high water solubility, biocompatibility, and low toxicity; and are ready for potential applications, such as biomedical imaging and optoelectronic devices.