High‐Temperature Resistance Photoluminescence Carbonized Polymer Dots Through Equilibrium Bi‐Confinement Effects

Abstract Carbon dots are emerging luminescent nanomaterials that have drawn considerable attention due to their abundance, environmental friendliness, and customizable optical properties. However, their susceptibility to temperature‐induced vibrational exciton changes and the tendency to thermal quenching of emission have hindered their practical applications. Here, a method is reported for achieving high‐temperature photoluminescence carbonized polymer dots (CPDs) through a bi‐confinement approach that involves a highly cross‐linked polymer network and a rigid Al 2 O 3 matrix. As the temperature increased from 303 to 500 K, the fluorescence and phosphorescence emission intensities of CPDs@Al 2 O 3 remained virtually unchanged, with the emission duration exceeding 150 h at 500 K. Additionally, CPDs@Al 2 O 3 composites with different degrees of carbonization exhibit dynamic excitation‐dependent photoluminescence properties, which can be patterned for multiple information encryption application. This work provides a concept for designing stable and luminous CPDs under harsh conditions, thus expanding their potential application range.