A novel label-free electrochemical sensor for Hg2+ based on the catalytic formation of metal nanoparticle

A novel label-free electrochemical sensor has been developed for the highly sensitive and selective detection of Hg2+. Hg2+ were first captured on the modified electrode surface through the specific thymine-Hg2+-thymine (T-Hg2+-T) coordination and then through the catalytic HAuCl4/NH2OH reaction for the formation of gold nanoparticles (AuNPs) as signal reporter. The formed AuNPs could be directly detected by stripping voltammetry. By the introduction of graphene to accelerate electron transfer and amplify the electrochemical signal, a detection limit as low as 0.06 nM could be obtained for Hg2+. Compared with the traditional metal nanoparticles (NPs)-based method, this sensor avoids the labeling of the DNA probe with NP tags, only one unlabeled T-rich DNA sequence was needed, which greatly reduced the cost and simplified the sensing procedure.