A rewritable and shape memory hydrogel doped with fluorescein-functionalized ZIF-8 for information storage and fluorescent anti-counterfeiting.

The emergence of stimuli-responsive fluorescence anti-counterfeiting technology has garnered increasing attention in the era of intelligent internet. Smart fluorescent hydrogels combine the characteristics of luminous materials with the unique structure of hydrogels, offering the potential for dynamic reversible erasing and multi-tiered data encryption. In this work, a fluorescent hydrogel was constructed by zeolitic imidazolate framework-8 loaded with fluorescein and then mixed with polyvinyl alcohol hydrogel, sodium carboxymethyl cellulose and borax, which could be used for image hiding in visible light. The reversible bonds cross-linked fluorescent hydrogel was stretchable and self-healing with a three-dimensional network structure. The hydrogel presented bright green fluorescence under 365 nm UV light, which was quenched by adding copper ions. Meanwhile, the imprint of the hydrogel could be cleared by L-Cysteine and repeatedly recorded information many times. The alkali-induced shape memory capability was further utilized to achieve multi-tiered data encryption by deforming it to a 3D-specific shape through folding. The rewritable and multi-dimensional encrypted hydrogel is expected to improve data security and reduce resource consumption.