Application of polyvinylpyrrolidone-stabilized silver nanoclusters as fluorescent probes for trace iodide in seaweed

Iodide is an essential trace nutrient in foods like seaweed, seafood, and iodized salt, with balanced intake critical for thyroid function and metabolic health. Accurate trace detection is key for nutrition evaluation and iodide deficiency prevention. Existing methods often face challenges in complex food matrices, so this study aimed to construct a polyvinylpyrrolidone (PVP)-stabilized silver nanocluster (AgNCs@PVP) fluorescent probe for trace iodide detection in seaweed.

AgNCs@PVP probes were synthesized via chemical reduction with PVP as a stabilizer, characterized by UV-Vis, TEM, and fluorescence spectroscopy. The iodide detection system was optimized for pH, reaction time, and probe concentration. Seaweed samples were pretreated by crushing, soaking, microwave-assisted extraction, protein precipitation, centrifugation, and pH adjustment. Sample solutions were mixed with AgNCs@PVP, and fluorescence intensity was measured at 340 nm excitation. Linear range, detection limit, selectivity, recovery, and repeatability were evaluated.

Iodide significantly quenched AgNCs@PVP fluorescence, showing a good linear response (0.29 μM-280 μM) with a detection limit of 56 nM. Common interfering substances in seaweed had no obvious impact on detection. The system exhibited good recovery (92.3-105.6%) and repeatability (RSD < 3.0%) in seaweed sample analysis. Synthesized AgNCs@PVP were spherical, uniformly dispersed (average size ~3.3 nm), and had stable fluorescence properties.

The AgNCs@PVP probe integrates PVP's stabilizing effect and AgNCs' excellent fluorescence performance, achieving sensitive and selective iodide detection. Its low detection limit and wide linear range address the needs of trace analysis in complex seaweed matrices, overcoming the drawbacks of traditional methods (cumbersome operation, poor selectivity). This study provides a rapid, reliable method for food iodide detection, supporting rational iodide intake and food nutritional safety.