Broad-range time-dependent afterglow colors in multi-confinement effect carbon dots for high-security dynamic information encryption

Arising from multiple triplet emission centers with distinct lifetimes, the time-dependent afterglow color (TDAC) phenomenon demonstrates significant potential for dynamic phosphorescence anti-counterfeiting and information encryption. However, insufficient spectral separation between triplet emissive peaks usually confines TDAC in carbon dots (CDs) to narrow color ranges, limiting distinguishability and security in advanced optical applications. Herein, a broad-range TDAC transition from deep orange to cyan within 1 s was achieved in an aluminum-ion doped CDs based composite (Al-CD@ Urea) via a rational synthesis process. The multi-confinement effect arising from the urea and silica matrix collectively facilitates triplet exciton stabilization and suppresses non-radiative transitions, thereby promoting enhanced phosphorescence emission in the composite system. Aluminum doping modifies the bandgap of CD, which realizes a blue TADF (peak at 450 nm) and a red RTP (peak at 590 nm) simultaneously under 360 nm excitation in composite system. The dual afterglow emission with distinct lifetimes collectively drives the observed broad color range TDAC phenomenon. Leveraging the broad-range TDAC properties in the Al-CD@ Urea, we developed dynamic afterglow anti-counterfeiting labels and a concept of information encryption with enhanced distinguishability and security, demonstrating practical viability for advanced optical applications.