Hydrothermal Processing as an Effective Strategy for Producing Coordinated Non‐Aromatic Hydrogels With Persistent and Reversible UV‐Activated Room‐Temperature Phosphorescence

Abstract The development of non‐aromatic hydrogels with unique persistent room‐temperature phosphorescent (RTP) through simple preparation methods remains a great challenge. Here, we propose and demonstrate a facile and universal hydrothermal processing strategy for transforming mechanical weak and non‐RTP emissive non‐aromatic hydrogels into mechanically very strong and persistent RTP hydrogels by metal ion coordination‐induced clustering of non‐conventional chromophores. As a model system, through hydrothermal processing in a solution of aluminum ions, polyacrylamide hydrogels show dramatically enhanced mechanical properties with tensile strength and elastic modulus up to 12.8 and 75.1 MPa, respectively, and very impressively, they also exhibit excellent RTP properties with long lifetime up to 169.7 ms and very interesting reversible UV‐activated RTP emission. The UV‐activated and persistent RTP emission enable innovative applications of the hydrogels in self‐erasing encryption and ultrasensitive antibiotic sensing. The hydrothermal processing strategy can be applied to preparing other RTP hydrogels by using different polymeric matrices and metal ions. This work establishes a universal paradigm for developing multifunctional RTP hydrogels through metal ion coordination and provides a basis for their practical applications.