Colorimetric determination of Hg2+ in environmental water based on the Hg2+-stimulated peroxidase mimetic activity of MoS2-Au composites

Abstract A colorimetric assay is described for sensitive determination of Hg 2+ ions based on the MoS 2 -Au composites as peroxidase mimetics, which are synthesized by microwave-assisted solvothermal method. The addition of Hg 2+ stimulates their peroxidase-like activity, along with lower Michaelis constant toward the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) with H 2 O 2 , allowing the composites for direct determination of Hg 2+ . A broad linear response is obtained ranging from 20 nM to 20 μM with a detection limit (LOD) of 5 nM. The superior peroxidase-like activity is attributed to the large surface area of MoS 2 nanosheets and the synergistic catalytic effect of MoS 2 and Au. The Hg 2+ -stimulation effect implies the strong interaction between Hg 2+ and MoS 2 -Au, where the XPS results confirm the presence of metallic Hg 0 , indicative of an Au-Hg amalgam. This colorimetric assay is successfully applied for the determination of Hg 2+ in environmental water (tap water and Yellow River water) with excellent selectivity over interfering cations.