Agar/Carbon Dots Crosslinked Polyacrylamide Double-Network Hydrogels with Robustness, Self-Healing, and Stimulus-Response Fluorescence for Smart Anti-Counterfeiting

From the perspective of sustainable economic development, the advanced fluorescent anti-counterfeiting technology concept is trying to encrypt information onto polymer materials with toughness, self-healing, and stimulus-responsive properties. Herein, a low cost and biocompatible fluorescent double network (DN) hydrogel based an anti-counterfeiting platform is demonstrated. The fluorescent hydrogels (agar/pAM–PCD DN gels) were composed of agar with a thermally reversible sol–gel transition property as the first physical network and polymerizable carbon dots (PCD) crosslinked polyacrylamide (pAM) as the second chemical network. Due to the thermally reversible sol–gel transition property, the interpenetrated physical/chemical crosslinked double network structure and the unique fluorescent characteristics of PCD, the as-prepared agar/pAM–PCD DN gels simultaneously presented excellent mechanical properties (tensile stress of 1.56 MPa, tensile strain of 1400%, and tearing energy of 3420 J m−2), rapid recoverability (30 min with 56.7%/63.3% stiffness/toughness recovery at 95 °C), good self-healing property (self-healing toughness/strain of 0.54 MPa/580% after 12 h resting at 95 °C), as well as photo- and Fe3+-sensing luminescence. The as-prepared agar/pAM–PCD DN hydrogels were further used for the fabrication of luminescent patterns with robustness, stretch resistance, and a self-healing ability for smart anti-counterfeiting. We anticipate that the agar/pAM–PCD DN hydrogels hold enormous potential in developing new-generation anti-counterfeiting materials and technology for data information encryption and protection.