A selective colorimetric and efficient removal strategy for mercury(II) in aquatic systems using mesoporous FeO-loaded silver probes.

Mesoporous FeO-loaded silver nanocomposites (FeO@Ag) were simply fabricated as bi-functional nanozymes for the catalysis-based detection and removal of Hg ions. It was found that the as-prepared magnetic FeO@Ag could display peroxidase-like catalysis activity that could be rationally enhanced in the presence of Hg ions. To our surprise, the shell of the Ag element may decrease the catalysis of the FeO to some degree. However, the Ag particles could serve as the probes for specifically recognizing Hg ions and trigger increased catalysis through the formation of Ag-Hg alloys, with a decreased signal background. A high-throughput colorimetric analytical method was thereby developed based on the FeO@Ag catalysis for probing Hg ions in the muscles of fish by using 96-well plates, at linear Hg concentrations ranging from 0.010 to 2.5 mg kg. Moreover, the developed colorimetric analytical method was applied to evaluate Hg levels in muscle samples of different kinds of fish. Unexpectedly, an obvious difference of Hg levels in muscles of four kinds of fish was discovered, with the order of snakehead () > largemouth bass () > crucian carp () > silver carp (), where the carnivorous fish showed higher Hg levels than the omnivorous or plant-based ones. Moreover, the as-fabricated FeO@Ag adsorbents with their large specific surface area and high environmental robustness could exhibit efficient Hg adsorption with capacities of up to 397.60 mg g. A removal efficiency of 99.40% can also be expected for Hg ions from wastewater, with the magnet-aided recycling of FeO@Ag adsorbents. Such an FeO@Ag-based colorimetric analysis and removal strategy for Hg ions should find wide applications in the fields of aquatic food safety, environmental monitoring, and clinical diagnostics of Hg-poisoning diseases.