Au Nanocluster-Based Smart Multicolor Luminescent Hydrogels for Encryption Applications

The development of nanocluster (NC)-based luminescent functional materials has gained tremendous attention recently owing to their unique optical properties. Herein, we studied the coassembly behavior of AuNCs modified using 6-propyl-2-thiouracil (PRT-AuNCs) with trimesic acid (TA). Microrods were formed through the coassembly, accompanied with enhanced photoluminescence emission. The intermolecular hydrogen bonding and π–π stacking between TA and PRT ligands were verified to be the main driving forces for the formation of ordered aggregates and consequently the improvement of the luminescence of PRT-AuNCs. Furthermore, inspired by the outstanding optical properties of the PRT-AuNCs/TA complex, we prepared a luminescent nanocomposite hydrogel through loading the PRT-AuNCs/TA complex into κ-carrageenan networks. The obtained hydrogel showed strong luminescence, high strength, and self-healing properties. Moreover, by doping blue emission quantum dots (QDs), a type of multicolor hydrogel was obtained. The different pH-responsive behaviors of QDs and PRT-AuNCs render the multicolor hydrogel a candidate with potential applications in information encryption. This study proposes a new method for the development of AuNC-based nanomaterials through coassembly and provides a perspective for the potential usage of AuNCs as smart luminescent devices.