Rational preparation of anti-water phosphorescent carbon-dots and flake C3N4 composites through microwave-heating method for multiple data encryption

The development of anti-water phosphorescent carbon dots (CDs) based materials is of great practical interest. Herein, we report a rational design of CDs based composite with anti-water phosphorescence by controlling a one-step microwave assisted heating of green fluorescent CDs and urea. Upon increasing the microwave-heating temperature, urea was gradually converted to C3N4, in which the CDs were uniformly embedded in the C3N4 matrix. The fluorescence/phosphorescence intensity of these CDs based composites are determined by the morphologies of the C3N4, which can be adjusted by controlling the microwave heating time. More importantly, the combining CDs in C3N4 not only promote the phosphorescence emission but also prevent the phosphorescence quenching by water, leading to stable phosphorescence emission in aqueous environment. Based on the anti-water phosphorescence properties of these CDs based composites, a concept of multiple data encryption was demonstrated.