Heterogeneous Fluorescent Organohydrogel Enables Dynamic Anti‐Counterfeiting

Abstract Fluorescent patterns showing the unique color change in response to external stimuli are of considerable interest for their applications in anti‐counterfeiting. However, there is still a lack of intelligent fluorescent patterns with high‐security levels, presenting a dynamic display of encrypted information. In this study, a fluorescent organohydrogel is fabricated through a two‐step interpenetrating technique, leading to the co‐existence of naphthalimide moieties (DEAN, green‐yellow fluorescent monomer) contained Poly(N,N‐dimethylacrylamide) (PDMA) hydrogel network and Polyoctadecyl methacrylate (PSMA) organogel network bearing spiropyran moieties (SPMA, photochromic monomer). Due to the unique heterogeneous networks, the fluorescence color goes through a continuous change from green to yellow to red via the fluorescence resonance energy transfer (FRET) process with the extension of irradiation time. In addition, when H+ is introduced into the system, SP units exhibit transformation into the protonated merocyanine (MCH+) rather than merocyanine (MC) under UV light, which inhibits the FRET process. By selectively being treated with H+, the fluorescent organohydrogel can act as an effective platform for encrypting secret information, making them more difficult to forge.