Dynamic Fluorescence Materials Based on Naphthalimide-Functionalized Silica Aerogels Covalently Grafted with Spiropyran: Applications in Advanced Information Encryption
Dynamic fluorescent materials with stimulus-responsive emission modulation are pivotal for next-generation information security. This study presents a photoresponsive fluorescent composite system where spiropyran (SP) is covalently grafted onto naphthalimide-functionalized silica aerogel matrices. The architecture exhibits reversible fluorescence resonance energy transfer (FRET) between naphthalimide donors and merocyanine (MC) acceptors under ultraviolet irradiation, enabling dynamic emission shifting from green (blue) to red. Aggregation-induced emission (AIE) characteristics of SP are exploited to engineer a smart material system that reversibly regulates distinct red fluorescence by precisely controlling amino group dispersion on the naphthalimide-functionalized silica aerogels. This spatial manipulation governs the molecular packing state of SP, enabling dynamic fluorescence modulation. Programmable control over fluorescence chromatic transitions is achieved by systematically adjusting SP grafting densities (1%, 2%, and 3% w/w). A unique mode of dynamic information encryption technology is developed utilizing these dynamic fluorescence variations. The materials substantially enhance information encryption levels due to precisely adjustable fluorescence properties in response to external stimuli over time, making the encryption process unpredictable and complex, thereby exponentially increasing the difficulty for unauthorized replication or decoding. However, photostability requires further improvement (Table S3).