Halloysite‐Based X‐Ray‐Activated Persistent Luminescent Hydrogels Enable Multiple‐Level Encryption and Dual‐Locked Camouflage

Exploring multiple‐level encryption technologies and extra safety decoding ways to prevent information leakage is of great significance and interest, but is still challenging. Herein, we propose a novel approach by developing halloysite‐based X‐ray‐activated persistent luminescent hydrogels with self‐healing properties, which can emit visible luminescence even after switching off the X‐ray irradiation. The afterglow properties can be well regulated by controlling the crystal form of the anchored nanocrystal on the surface of the halloysite nanotube, enabling the “time‐lock” encryption. Additionally, the absence or presence of photoluminescence behaviors can also be controlled by changing the crosslinkers in synthesizing hydrogels. Six types of hydrogels were reported by means of condensation reactions, which show diverse emission and afterglow properties. By taking advantage of these features, the hydrogels were programmed as a display panel that exhibits three types of fake information under the wrong decoding tools. Only when the right stimuli are applied at the defined time does the panel give a readable pattern, allowing the encrypted information to be recognized. We believe this work will pave a novel path in developing extra safety information‐encryption materials.