Sensitive Competitive Electrochemical Immunosensor for Hg (II) Based on Molybdenum Disulfide/Reduced Graphene Oxide/Gold Nanocomposites

A sensitive and specific competitive electrochemical immunosensor for the detection of Hg (II) using a modified electrode based on molybdenum disulfide/reduced graphene oxide/gold (MoS2/rGO/Au) nanocomposites was developed in this study. The nanocomposites were characterized and assembled with an antibody against Hg (II) for the immunosensor, demonstrating good electrical activity, high affinity and high specificity. Free Hg (II) in a solution can be measured by the competitive reaction of the Hg element in the sample and the antigen with the antibody fixed on the electrode. A differential pulse voltammetry (DPV) method was used, and the competitive current changed in accordance with the concentration of Hg (II). Under optimal conditions, the sensor showed a linear relationship from 0.1 to 600 ng/mL, and the limit of detection (LOD) was 63 pg/mL. The proposed immunosensor showed an acceptable recovery from 98.4% to 100.3% in spiked samples. Satisfactory stability and reproducibility were obtained. Competitive species, including Zn (II), Mg (II), Al (III), Cu (II), Pb (II), Ba (II), Cd (II), Ag (I), MNA, CH3Hg (I) and CH3Hg-MNA, were selected and applied according to the procedure of the assay, and their significantly different response compared to Hg (II) indicated that the assay displayed not only high sensitivity but also high selectivity. This immunosensor offers a useful model for the detection of Hg (II).