Color-Tunable and Time-Dependent Room-Temperature Phosphorescence Carbon Dots for Dynamic Multi-information Encryption

The development of carbon dots (CDs) with color-tunable long-lived room-temperature phosphorescence (RTP) represents a significant advancement in the field of information encryption and anticounterfeiting applications. In this study, carbon dots doped with B and N (BNCDs) were synthesized via a one-step hydrothermal method using boric acid and glutamate. The dynamic multicolor BNCDs with distinct optical properties, including significant shifts in phosphorescence emission and prolonged phosphorescence lifetimes, were achieved by modulating both the amount of carbon source precursor and the reaction temperature. The combination of a rigid matrix of B₂O₃, a C–B covalent bond, and hydrogen bonds enabled BNCDs to achieve long phosphorescence lifetimes and high photoluminescence quantum yields of up to 1.15 s and 9.48%, respectively, at room temperature. Subsequently, following the deactivation of the UV lamp, the naked-eye discernible RTP lifetime of BNCDs was observed to be 13 s, with a dynamic color change from yellow to green within 1–3 s for some specific BNCDs. Moreover, the RTP lifetime of BNCDs was observed to exceed 6 s when illuminated with visible light. BNCDs show significant potential in areas such as dynamic encryption and advanced fingerprinting.