Portable-Equipment-Assisted Colorimetric Hydrogel Kits Based on Quercetin-Reducing Silver Nanoparticles for Hg2+ Tests in Aquatic Products

As a highly hazardous heavy metal, mercury ion (Hg2+) poses a serious threat to human health through the intake of polluted aquatic products and water. Accordingly, the development of a simple, sensitive, and efficient method for Hg2+ detection is of significant importance. Herein, a novel silver nanoparticle (Qu-CD-AgNPs) was successfully synthesized using an inclusion complex of Qu and β-cyclodextrin, which forms an Ag–Hg alloy upon interaction with Hg2+, markedly enhancing its oxidase-like activity to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB), generating a Hg2+ concentration-dependent color change. On this basis, a colorimetric detection platform for Hg2+ was fabricated by integrating the hydrogel-based Qu-CD-AgNPs + TMB system and a self-developed RGB-values-analysis app for portable equipment. Under the optimized conditions, the platform shows a linear range between 3 and 100 μM and a detection limit as low as 0.023 μM, as well as excellent selectivity and anti-interference performance. This work promises a broad application prospect in water-quality monitoring and the inspection of aquatic products.