Lanthanide–polyoxometalate-based self-erasing luminescent hydrogels with time-dependent and resilient properties for advanced information encryption

In such an era of information explosion, improving the level of information security is still a challenging task. Self-erasing luminescent hydrogels are becoming ideal candidates for improving the level of information security with simple encryption and decryption methods. Herein, a lanthanide-polyoxometalate-based self-erasing luminescent hydrogel with time-dependent and resilient properties was constructed through a covalent crosslinked network constructed with polyacrylamide and a non-covalent crosslinked network constructed with [2-(methacryloyloxy)ethyl]trimethyl ammonium chloride/Na₉DyW₁₀O₃₆, along with doping urease. This acquired hydrogel exhibited reversible luminescence switching properties in the presence of HCl-urea mixed solution. At the same time, obvious changes in the luminescence intensity can be seen on the timescale by modulating the concentrations of HCl and urea/urease. Based on this, the information loaded onto the hydrogel by using a HCl-urea mixed solution self-erased over time, leading to misinformation during this process. The real information can only be recognized at a specific time. Moreover, the information is self-erased permanently, which can avoid secondary leakage of information. In addition, the hydrogel has excellent resilience. The information can be loaded in the stretched state of the hydrogel, resulting in the information only being recognized in the re-stretched state of the hydrogel while the information cannot be recognized in the normal state of the hydrogel. The combination of time-dependent and resilient properties of the hydrogel can further improve the level of information security effectively. This self-erasing luminescent hydrogel with time-dependent and resilient properties has great potential in improving the security of information encryption.