Time‐Programmable Fluorescence in Perovskite Quantum Dots via Reverse Sustained‐Release Strategy for Dynamic Information Encryption

Smart luminescent materials capable of time‐resolved dynamic fluorescence color transitions hold immense potential for advanced information encryption and anti‐counterfeiting technologies in the emerging digital era. However, achieving precise control over wide‐range fluorescence color modulation remains a significant challenge. In this study, a novel reverse sustained‐release strategy is presented to fabricate CsPbBr 3 @PAA perovskite quantum dots (QDs), where ultra‐small CsPbBr 3 QDs within quantum confinement size (QCS) are confined within a polyacrylic acid (PAA) matrix. Initially, the CsPbBr 3 @PAA QDs exhibit blue‐violet fluorescence in toluene due to the quantum confinement effect. Upon exposure to hydrous alcohol, the PAA matrix enables a controlled, reverse release of CsPbBr 3 QDs into the solvent, triggering a morphological transition from sub‐nanometer QDs to nanoblocks exceeding the QCS. This structural evolution induces a dynamic time‐dependent fluorescence shift from blue‐violet to green, spanning five visually distinct colors (blue‐violet, blue, cyan, turquoise, and fluorescent green) across the CIE chromaticity diagram. By leveraging this unique time‐resolved color transition mechanism, programmable information encryption and dynamic fluorescent patterning with temporal precision are demonstrated. This work not only advances the design of stimuli‐responsive luminescent materials but also provides a versatile platform for next‐generation optical security systems