A fluorescent/photochromic dual-function Mo-based hydrogel for information encryption

One-step thermal-initiated polymerization to prepare light-responsive hydrogels • Achieve independent and reversible control of color change and fluorescence emission • The hydrogel achieves information encryption/decryption functions. Developing low-cost and straightforward strategies for integrating photochromic materials with fluorescent components is essential for next-generation information encryption. In this work, we present a facile fabrication of a photo-responsive fluorescent hydrogel by employing ammonium molybdate tetrahydrate (Mo) as the photochromic agent and fluorescein-o-acrylate (Fa), a monomer bearing a carbon–carbon double bond, as the fluorescent building block. Fa is covalently polymerized into the polyacrylamide (PAM) backbone, while Mo is anchored to the three-dimensional gel network via multiple hydrogen bonds. Upon exposure to a 365 nm UV source, PPM 3 F 3 G displayed a maximum emission peak at 547 nm, emitting visible yellowish-green fluorescence. After 60 s of continuous irradiation, the original fluorescence superimposed with the photochromic blue background produced a green fluorescence perceptible to the naked eye. Notably, the coloration process induced by prolonged UV irradiation does not cause fluorescence quenching, and both optical modalities exhibit outstanding cyclic stability and high reversibility. By integrating PPMFG with ASCII code and other innovative anti-counterfeiting platforms, we successfully develop highly secure encryption modes that resist counterfeiting. Download: Download high-res image (129KB) Download: Download full-size image