Aggregation-induced color fine-tunable carbon dot phosphorescence covering from green to near-infrared for advanced information encryption

Multi-color phosphorescence carbon dots (CDs) show enormous potential in advanced information encryption, yet the achievement of wide-range, fine-tunable phosphorescence CDs, especially with near-infrared (NIR) phosphorescence emission, confront numerous challenges. Herein, for the first time, the phosphorescence CD-based composites with fine-color tunable property ranging from green to NIR are obtained via regulating CDs contents in annealed boric acid (BA). The synthesized CDs are fully passivated by BA molecular and form uniform surface state, which avoids aggregation-induced quenching to some extent. By increasing the CDs contents in BA during thermal treatment, the aggregation degree of CDs is gradually increased, causing substantial electronic interactions. This leads to energy splitting and form low-energy aggregation states, resulting in phosphorescence continuously shifts from 530 to 555, 585, 625, 645 and 750 nm. Based on aggregation-induced discoloration, we further explore solvent-triggered evolutionary discoloration property of CDs, that is, trace methanol could induce phosphorescence color change from green to red, and illustrate their potential applications in advanced anti-counterfeiting and information encryption.