Colorimetric determination of Hg(II) sensor based on magnetic nanocomposite (Fe3O4@ZIF-67) acting as peroxidase mimics

Abstract An extremely sensitive colorimetric sensor has been developed for selective determination of Hg2+ in aqueous solution based on magnetic nanocomposite (Fe3O4@ZIF-67), which results in an effective intrinsic peroxidase mimicking activities and makes the composites oxidize the 3, 3′, 5, 5′- tetramethyl benzidine (TMB) in the presence of hydrogen peroxide (H2O2) to produce a blue coloured solution. Significantly, the oxidation of TMB was retarded or prevented in the presence of antiradical biomolecules Glutathione (GSH) because of its strong cation restoration property. When Hg2+ is added, the strong affinity of mercury ions with thiol groups of GSH provokes the oxidation of the substrates, which helps the solution turn into blue colour. The absorbance intensity was proportional to the concentration of Hg2+ in the wide range of 0–30 nM and detection limit was successfully as low as 0.36 nM. The resultant nanocomposite based peroxidase mimicking activity applied as a versatile platform in the colorimetric detection of Hg2+ was established the other co-existing metal ions in aqueous solutions. Finally the sensor was applied to detect Hg2+ in real water sample with satisfactory recovery results. Interestingly, the proposed colorimetric sensing platform held great potential in the application of mercury contamination in industrial sewage.