A Green and lower-temperature synthesis of two-color fluorescent nitrogen dopedgraphene quantum dots

Herein, the nitrogen-doped graphene quantum dots (N-GQDs) were produced by a facile thermal treating strategy at low temperature using citric acid (CA) and urea as the precursors. The as-prepared N-GQDs with different ratios of the precursors exhibited blue or green emission with relatively high quantum yield in the ethanol solution. While in the aqueous solution, the quantum dots displayed both blue and green emissions, which indicate two independent luminescent centers coexisted in the N-GQDs. Considering of the excellent absorption ability of the N-GQDs in the visible-light region, the N-GQDs was combined with titanium dioxide (TiO2) as the dye sensitizer. And, the products showed 16 times catalytic degradation ability than that of pure TiO2 for rhodamine B (RhB).