Zinc‐Doping Trap Engineering and FRET Synergy Enable Multicolor Room‐Temperature Phosphorescence in Rice‐Derived Carbon Dots Confined in Amorphous Alumina for Advanced Encryption

ABSTRACT The development of multicolor room‐temperature phosphorescence (RTP) materials with tunable afterglow is crucial for advanced information encryption. Herein, we propose a synergistic strategy that integrates trap engineering and Förster resonance energy transfer (FRET) process for dynamically adjusting the emission color and lifetime. Expired rice‐derived carbon dots@Zn‐doping alumina (CDs@Zn x Al 2 O 3 ) composites with standout RTP properties are designed and fabricated using an in situ preparation strategy. In situ Zn 2+ doping is employed to engineer trap states within amorphous Al 2 O 3 , which not only optimizes the energy level structure of confined CDs but also enables precise modulation of phosphorescence color and lifetime. The optimized CDs@Zn 1.5% Al 2 O 3 composite achieves an ultralong green RTP duration of up to 22 s. Furthermore, by introducing newly synthesized red‐emissive TPA‐β‐CD‐aggregates with excellent aggregation‐induced emission (AIE) performance as an energy acceptor, efficient singlet‐to‐singlet and triplet‐to‐singlet FRET (SS‐FRET/TS‐FRET) pathways are established. Tuning the doping ratio allows dynamic control over the competition between these pathways, resulting in finely adjustable multicolor RTP emissions. This work demonstrates a versatile platform for creating color‐tunable, ultralong RTP materials and showcases their direct application in time‐gated, multilevel security encryption.