Metal ion-induced multifunctionality in luminescent hydrogels for information encryption and mercury ion detection

Information security has long been a focal point of research. However, the development of cryptographic hydrogels endowed with both high security and multifunctionality remains a challenge. Herein, we reported a method to construct multifunctional hydrogels using a metal ion-induced strategy. Leveraging Au- induced luminescence, Zn 2+ - induced shape memory, and Hg 2+ - induced fluorescence quenching, our method engendered a suite of distinctive properties, including fluorescence, shape memory effects, and ionic conductivity. Tunable fluorescence was utilized for detecting Hg 2+ with a detection limit as low as 0.0007 μmol/L. Additionally, a successful design of a multilevel information encryption platform, ranging from 2D to 3D, was achieved by combining the aforementioned properties. The information written using Hg 2+ as ink can be protected by the fixed shape of Zn 2+ , and the encrypted information can only be read under the conditions of shape recovery and UV irradiation. This simple yet effective strategy demonstrates a promising future for the application of this hydrogel in information encryption.