Harnessing spiropyran isomerization in lanthanide metallopolymers for sequential logic encryption and anticounterfeiting

Abstract

Stimuli-responsive lanthanide-based luminescent materials, exhibiting dynamic changes in photoluminescence in response to external stimuli and reversible recovery of their properties, hold great promise for advanced optical encryption and anticounterfeiting technologies. Nevertheless, simultaneously achieving reversible responsiveness to light, pH, and temperature alongside tunable multicolor emission remains a significant challenge. Herein, we present a facile strategy for constructing two terbium-based metallopolymers (Poly-Tb(1–2)) that exhibit triple-mode reversible responsiveness and tunable emission behavior. By copolymerizing spiropyran and terpyridine into a polymethyl methacrylate backbone and coordinating the polymer with β-diketone Tb(III) complexes, Poly-Tb(1–2) with effective energy transfer from the Tb³⁺ ions to the merocyanine isomer of spiropyran were obtained. The resulting Poly-Tb(1–2) exhibit excellent photochromic behavior and pH-dependent emission color switching. Remarkably, Poly-Tb(1) exhibits reversible responsiveness to both light and pH stimuli, and in its MC state, shows the rare phenomenon of enhanced Tb³⁺ luminescence upon heating. Such multifunctional optical behavior enables precise multicolor modulation and exceptional adaptability to complex external stimuli. Capitalizing on their robust multi-stimuli responsiveness, these materials were further applied in erasable photopatterning and sequential logic information encryption systems. This work offers a new design strategy for lanthanide metallopolymers and may contribute to the development of next-generation intelligent multifunctional materials.