Multifunctional red-emission graphene quantum dots with tunable light emissions for trace water sensing, WLEDs and information encryption

In this study, red-emission graphene quantum dots (R-GQDs), with tunable emission wavelength, are synthesized and explored for applications in trace water sensing, white light emitting diodes (WLEDs) and information encryption. Systematic experiments and characterizations demonstrate that the as-fabricated R-GQDs possess homogeneous size, good crystallinity and high doping concentration of nitrogen and oxygen. Moreover, tunable multicolor light emissions of R-GQDs are demonstrated by simply adjusting the polarity of surrounding solvents. As a result, solid-state fluorescence films are successfully fabricated to construct a high-quality WLED, with the CIE (Commission International d′Eclairage) coordinates (0.352, 0.380) and color temperature of 5121 K. Besides, the water quenchable fluorescence of R-GQDs enables the fabrication of a trace water sensing platform, with the low detection limit of 0.034%. Finally, the potential of our prepared R-GQDs for the application in color visual information encryption is developed. This study may pave the way for the development of GQDs, especially in optically sensing, optoelectronics and anti-counterfeiting technology.