Electrochemical sensor based on MoS2 nanosheets and DNA hybridization for trace mercury detection

Mercury ions (Hg2+) are highly toxic and can cause serious harm to the environment and human health. In this study, we prepared a novel electrochemical sensor based on an electrode coated with chitosan/graphene oxide/molybdenum disulfide/Au nanoparticles (chitosan/GO/MoS2/AuNPs) and thymine-Hg2+-thymine base pair to detect trace Hg2+ in water. This method effectively utilized the affinity of MoS2 to immobilize deoxyribonucleic acid (DNA) on the electrode surface and enabled the amplification of the electrochemical signals detected by the sensor. The specific binding of the thymine-Hg2+-thymine base pair and the electrochemical activity of MoS2 successfully reduced the detection limit of Hg2+ and rendered it interference resistant. In the presence of Hg2+, a double-stranded structure was formed on the electrode after the interaction between Hg2+ and DNA, which caused the change of the oxidation current signal of the electrode surface. The sensor showed good linearity ranging from 0.01 μg/L to 4 μg/L with a correlation coefficient of 0.991, and the limit of detection was found to be 5.8 ng/L. This portable chitosan/GO/MoS2/AuNPs modified electrode showed satisfactory recovery in tap water samples, thus demonstrating its potential for application in trace Hg2+ detection.