Synergistic integration of carbon dots and ZIF-8 in alginate hydrogel spheres: A bifunctional platform for efficient mercury adsorption and selective sensing

In this study, a novel alginate-based composite hydrogel sphere embedded with zeolite imidazole framework (ZIF-8) and carbon dots (CDs) was developed for simultaneous efficient adsorption and selective detection of mercury ions (Hg 2+ ). The hydrogel spheres (Z8S-CDs) integrate the porous structure of ZIF-8 for efficient Hg 2+ adsorption and the fluorescence properties of CDs for visual detection. The adsorption capacity of Z8S-CDs reached 381.67 mg/g for Hg 2+ , significantly surpassing conventional alginate hydrogels, attributed to synergistic chemisorption and pore-filling mechanisms. Meanwhile, the hydrogel spheres exhibited selective fluorescence quenching upon Hg 2+ binding, enabling rapid detection with a low detection limit (3.63 × 10 −8 M) and high specificity against competing ions. The hydrogel spheres maintained structural stability and reusability over multiple cycles. This work provides a dual-functional platform for effective Hg 2+ removal and real-time monitoring in contaminated water, highlighting its potential for environmental remediation applications.