Lanthanide-Functionalized Carbon Quantum Dot-Based Dual-Emission Hydrogels for Multilevel Anti-counterfeiting and Repeatable Information Loading

With the increasing development of advanced optical anti-counterfeiting technologies, it is essential to develop a simple, fast fluorescent material with anti-counterfeiting properties. In this study, we successfully prepared a single-emission CDs-based hydrogel (CDs@PVA-Alg) by introducing carbon dots (CDs) into the interpenetrating network of sodium alginate (Alg) and poly(vinyl alcohol) (PVA) via hydrogen bonding and further cross-linking them with Ln3+ ions to obtain dual-emission Ln-functionalized CDs-based hydrogels (Ln@CDs@PVA-Alg) (Ln = Tb, Eu). By freeze–thawing and ion-exchange methods, the resulting hydrogels displayed extraordinary mechanical properties and significant photoluminescent properties. On one hand, the CDs@PVA-Alg hydrogel demonstrated distinct fluorescence responses to Ln3+ ions. On the other hand, the fluorescence of Tb@CDs@PVA-Alg was quenched by H+ ions and restored in OH– solution. Furthermore, the mechanism of the above fluorescence response was explored in depth, which was further used to create an excellent optical anti-counterfeiting platform that can be utilized for multilevel anti-counterfeiting and repeatable information loading. By changing the excited light and chemical reagent, these materials enable versatile operations such as encryption, decryption, decoding, loading, and unloading of a wide range of information. This study not only supplies a representative example of the fabrication of dual-emitting Ln@CDs@PVA-Alg hydrogels but also investigates their potential application as smart polymeric gels with multifunctionality.