Multifunctional Double-Network Hydrogel Synergistically Enhanced by Zirconium Ions and Carbon Quantum Dots

Inspired by the intuitive and efficient information-sensing capability of colorimetric changes, this work presents a design strategy that integrates fluorescent carbon quantum dots (CDs) with metal ion coordination to simultaneously enhance mechanical robustness and multimodal sensing performance. Specifically, CDs and zirconium ions were incorporated into a polyacrylamide/sodium alginate (PAM/SA) matrix to construct a multifunctional polyacrylamide/sodium alginate/carbon quantum dot/zirconium ion (PSCZ) hydrogel through chemical cross-linking, dynamic coordination, and multiple hydrogen-bonding interactions. At an optimal CD concentration of 20 μg·mL-1, the PSCZ hydrogel exhibits outstanding mechanical properties, including a tensile toughness of 923.5 kJ·m-3, a tensile strength of 303.9 kPa, and an elongation at break of 423.6%. This design effectively overcomes the conventional trade-off between structural robustness and multifunctionality. In addition, linear fitting analyses reveal strong correlations between brightness variation and both strain (R2 = 0.963) and resistance (R2 = 0.926), indicating correlated optical and electrical responses of the hydrogel to mechanical deformation. Benefiting from these features, the PSCZ hydrogel shows potential for physiological signal monitoring and fluorescent anti-counterfeiting, while the PSCZ-based TENG enables mechanical energy harvesting, demonstrating its potential as a power source for next-generation wearable electronics, human-machine interfaces, and motion and health monitoring systems.