Aggregation-induced emission solid-state multicolor fluorescent carbon dots for LEDs and fingerprints applications

At present, most of the reported carbon dots (CDs) are still dispersed in the solvent in liquid state. However, solid-state CDs cannot fundamentally prevent the aggregation-caused quenching effect (ACQ), which seriously affects their application. Herein, hydrophobic solid-state luminescent CDs with typical aggregation-induced emission (AIE) behavior were synthesized by simple solvothermal method using dithiosalicylic acid (DSTA) and acetic acid. The AIE behavior of CDs is mainly due to the presence of disulfide bonds, which restrict the intramolecular rotation of CDs surface groups around them, thus generating solid-state fluorescence (SSF) in long-wave emission. In addition, by using MA, urea and sulfonamide to tune the emission behavior of CDs, red, yellow and green AIE CDs named R-CDs, Y-CDs and G-CDs were obtained successfully. The as-prepared CDs powder was further applied to fabricate multi-color light-emitting diodes (LEDs) on UV chips. The fabricated tri-color LED devices can maintain high color purity and color rendering index (CRI). More importantly, the Correlated color temperature (CCT) of the three LED devices was located in the warm light area, which could effectively reduce visual fatigue. Finally, we applied three kinds of AIE CDs in fingerprint detection and effectively displayed the details.