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 CsPbBr₃@PAA perovskite quantum dots (QDs), where ultra-small CsPbBr₃ QDs within quantum confinement size (QCS) are confined within a polyacrylic acid (PAA) matrix. Initially, the CsPbBr₃@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 CsPbBr₃ 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