Förster Resonance Energy Transfer Mediated Tunable Fluorescence of Poly(ionic liquids)/Poly(thioctic acid) Dual-Network Ionogel

Multicolor fluorescent materials with time-dependent optical response have garnered significant interest in recent years owing to their promising applications in advanced anticounterfeiting technologies. However, conventional fluorescent materials often suffer from limitations such as inflexible emission properties and poor surface adhesion, which restrict their practical use. In this study, we report a family of photostimuli-responsive dynamic fluorescent ionogels (NEC-PIL-PTA-SP) with inherent adhesion and self-healing capabilities. These ionogels are constructed through the integration of an imidazolium-based poly(ionic liquid) (PIL) and a spiropyran-functionalized poly(thioctic acid) (PTA-SP). Leveraging the abundant noncovalent interactions, the PIL/PTA dual-network ionogel exhibits tunable fluorescence behavior mediated by Förster resonance energy transfer (FRET). Under visible light irradiation (470 nm), the ionogel emits blue fluorescence, which switches to red upon ultraviolet (UV) light (365 nm) irradiation. This fluorescence transition is highly reversible under alternating UV/visible light cycles. The tunable emission originates from an efficient FRET process between the imidazolium-based donor and the spiropyran-based acceptor. Furthermore, the dual-network ionogel demonstrates excellent autonomous self-healing and strong adhesion to various substrates. Benefiting from its time-dependent fluorescence and robust adhesion, the PIL/PTA ionogel can be directly applied as a reusable anticounterfeiting label. This study offers a feasible and innovative strategy for designing dynamic multicolor luminescent materials with combined optical versatility and surface adaptability.