Construction of high-strength p(HEMA-co-AA) fluorescent hydrogels based on modified carbon dots as chemically crosslinkers

A novel kind of p(HEMA-co-AA) fluorescent hydrogels with high strength are first generated through one-step photopolymerization of 2-hydroxyethyl methacrylate (HEMA), acrylic acid (AA), and HEMA-modified carbon dots (HMCDs). Herein, HMCDs are used as new nontoxic fluorescent crosslinking centers. The novel HMCDs-based fluorescent hydrogels not only display stable photoluminescence, but have high mechanical strength. The fluorescent properties of the HMCDs-based hydrogel films are similar as that of CDs solution and stable for a prolonged duration. Besides, the fluorescent intensity of HMCDs-based hydrogels can be changed by controlling the HMCD content. The tensile strength of the fluorescent hydrogels with 1 wt% HMCD content can reach up to ~ 12 MPa, higher than that of the conventional hydrogels. More importantly, the mechanical properties can be adjusted by changing the water content and HMCD content. The enhanced mechanical strength is probably attributed to the relatively ordered hierarchical microstructure.