Eu3+-Crosslinked Polymers with Tunable Ultralong Phosphorescence for Time-Resolved Information Encryption

Abstract

Organic room-temperature phosphorescence (RTP) materials have emerged as promising candidates for advanced photonic applications. However, achieving precise control over phosphorescence lifetime and integrating multiple emission modes within a single system remain major challenges. Herein, we report a strategy to fabricate tunable RTP materials by covalently incorporating a vinyl-functionalized Eu3+ complex into a polyacrylamide backbone that also contains organic phosphor units (phenylpyridinium derivatives). The Eu3+ complex serves a dual role: as a structural node, it coordinates with polymer chains to form a crosslinked network, enhancing matrix rigidity and effectively suppressing non-radiative transitions, which prolongs the RTP lifetime from 0.81 s to 1.63 s. Simultaneously, it acts as an energy acceptor, enabling a ligand-to-metal photosensitized energy transfer (PSET) process from the organic phosphors to Eu3+ ions. By simply adjusting the doping concentration of the Eu3+ complex, we achieve continuous modulation of the RTP lifetime (from 0.81 s up to 1.63 s, and then down to 0.16 s) and the afterglow duration has also been extended (from 7.0 s up to 21.0 s, and then down to 13.0 s). Intriguingly, realize a unique dual-emissive system featuring long-wavelength (red) fluorescence from Eu3+ and short-wavelength (green) ultralong phosphorescence. This finely manipulated optical behavior, encompassing both color and lifetime dimensions, is leveraged to construct a high-security-level, multi-layer information encryption platform based on time-resolved and color-resolved dot-matrix patterns. This work not only provides a facile and robust method for dynamically manipulating RTP properties but also opens new avenues for designing smart luminescent materials for cutting-edge anti-counterfeiting and information storage technologies.