Novel Cu:ZnS Quantum Dots‐Sodium Alginate Composite Fluorescent Hydrogel for Simultaneous Visual Detection and Efficient Removal of Pb(II)

ABSTRACT A novel composite fluorescent hydrogel composed of copper‐doped zinc sulfide quantum dots (Cu:ZnS QDs) was embedded in sodium alginate (SA). Fluorescence sensors were constructed on the basis of fluorescent hydrogels for nondestructive visual detection and efficient removal of Pb(II) from beverages. A seamless process for Pb(II) detection and removal was established by integrating the hydrogel into a self‐designed accessory device for automated cyclic operation. In each automated cycle, the Cu:ZnS QD‐SA hydrogel was introduced to the sample solution using an accessory device. Upon interaction with Pb(II) ions facilitated by Ca(II), the hydrogel underwent solidification, effectively binding to Pb(II) through a combination of chemisorption and physical adsorption. The resultant hydrogel beads were subsequently removed and analyzed under ultraviolet light, where the Pb(II)‐induced aggregation of the Cu:ZnS QDs led to a fluorescence quenching effect. This phenomenon enabled visual detection on the basis of the linear correlation between the fluorescence luminance ratio and Pb(II) concentration in the range of 0.1–60 mg/kg. The methodology has been validated through applications in complex real‐world samples, achieving recovery rates between 92.15% and 100.28%, with a removal efficiency exceeding 99.62% after manifold cycles. The proposed approach underscores benefits, such as high efficiency, non‐toxicity, cost‐effectiveness, automation, and convenience, and presents a promising way to monitor and mitigate excessive heavy metal contamination in liquid foods.