Time-dependent phosphorescence colors from carbon dots in zirconia for dynamic information encryption and ratiometric thermometry

Afterglow materials displaying time-dependent phosphorescence colors (TDPCs) are pivotal for advanced optical encryption, yet their rational design remains challenging. Herein, we report a controllable synthesis of carbon dots (CDs) embedded within a zirconia matrix (CDs@ZrO 2 ) that demonstrate remarkable TDPCs via facile calcination of a Zr-based metal–organic framework. The composites feature dual emissive centers, producing short-lived blue phosphorescence from the carbon core and long-lived yellow-green phosphorescence from surface states. The calcination temperature precisely tailors the graphitization degree and surface chemistry, enabling programmable control over the emission profile and dynamic color evolution. The ZrO 2 matrix provides multi-confinement of CDs via structural rigidity and covalent/hydrogen bonding, effectively stabilizing triplet excitons and endowing exceptional environmental robustness. The unique TDPC characteristic is successfully leveraged for high-level dynamic information encryption with temporal resolution. Furthermore, the distinct thermal quenching behaviors of the blue and yellow-green phosphorescence components in CDs@ZrO 2 facilitate the development of a ratiometric optical thermometer, exhibiting excellent linear response from 298 to 473 K for quantitative detection and visual semi-quantification of temperature in the range of 298–398 K. This work establishes a novel paradigm for creating intelligent afterglow materials with significant potential in photonic security and sensing technologies.