Dual-mode fluorescent hydrogel and its ion response behavior based on the coordinated construction of europium/carbon dot dynamic dual network

In this study, a composite hydrogel was designed and prepared based on a simple hydrothermal method with a synergistic strategy of citric acid carbonization and rare earth coordination. Through the coordination effect of the sp 2 graphitized nucleus (0.21nm crystal surface spacing), surface functional groups and europium (Eu 3+ ) of the carbon dots (CDs), a dynamic “soft-hard” dual network structure is constructed, realizing the synergistic optimization of fluorescence-electrical-mechanical-swelling characteristics. Compared to existing rare-earth-based dual-color fluorescent hydrogels, this material uniquely achieves independent excitation/emission control at dual wavelengths (433 nm/615 nm under 317 nm/291 nm excitation), surpassing the typical single-excitation limitations of analogous systems. Studies have shown that the hydrogel exhibits a broad detection range for K + (0.1–5 mol/L) with visual fluorescence enhancement. The material's compressive strength (18 MPa at 80% strain) and dynamic self-healing ability further demonstrate its excellent mechanical stability. This work provides a novel paradigm for designing multifunctional hydrogels with integrated optical, mechanical, and responsive properties.