Bright Tunable Multicolor Graphene Quantum Dots for Light-Emitting Devices and Anticounterfeiting Applications

The development of multicolor tunable emission graphene quantum dots (GQDs) is important for their application in photoelectric devices and multicolor anticounterfeiting. Herein, we synthesize blue (B-GQDs), green (G-GQDs), and red GQDs (R-GQDs) via a solvothermal reaction. The B-, G-, and R-GQDs exhibit excitation-independent behavior, excellent fluorescence properties, and exceptional photostability. The relative quantum yields (QYs) for the B-, G-, and R-GQDs are 68, 62, and 27%, respectively. Structural characterization and theoretical calculations indicate that the quantum size effect adjusts the red shift of emission from B-GQDs to G-GQDs, and the increased content of oxygen and C═N bonds are answerable for the red emission of R-GQDs. Then, we apply the prepared multicolor GQDs as a fluorescent ink for pattern printing and multicolor anticounterfeiting. Moreover, B-, G-, and R-colors and white light-emitting diodes (LEDs) are fabricated by ultraviolet radiation as excitation. The white LEDs exhibit a color coordinate of (0.335, 0.343), a high color rendering index of 95, and a correlated color temperature of 4835 K. This research successfully expands the potential application of GQDs in the reliable anticounterfeiting, information security, and high color rendering index GQD-based LEDs.