A stimulus-triggered luminescent hydrogel with Al3+ for visible color tunability in advanced information encryption applications

Abstract

Color-tunable luminescent hydrogels have shown significant potential in smart display devices, data encryption and multilevel anti-counterfeiting due to their excellent flexibility, functional versatility and optical properties. However, developing hydrogels that exhibit prominent optical decryption capabilities while maintaining robust mechanical properties remains a challenge. Herein, we present an Al³⁺ stimulus-triggered luminescent hydrogel with the integrated properties of wide multi-color tunability, self-healing capacity, high strength (160%) and an impressive toughness (180 kJ m⁻³). The double-network in the hydrogel with rich hydrogen bonds is well compatible with various luminophores. These include luminescent layered rare earth hydroxide nanosheets (LRH NSs) with red/green (R/G) emission and a chemosensor molecule that displays a fluorescence “turn-on” change in blue (B) emission only in the presence of Al³⁺ as a stimulus. Consequently, this smart hybrid hydrogel not only provides an adjustable tool for tuning the visible color of soft materials based on orthogonal responsive R/G/B three-primary-color luminescence, but also acts as a specific key for enabling color-switchable anti-counterfeiting and information encryption/decryption. These unique optical properties of the luminescent soft material highlight its potential as a hydrogel-based functional platform for the development of intelligent and color-tunable cryptographic devices with low cost, facile synthesis, and good processability.