Ultrasensitive electrochemical sensor for mercury ion detection based on molybdenum selenide and Au nanoparticles via thymine-Hg 2+ -thymine coordination.

An ultrasensitive and specific-selection electrochemical sensor was constructed for Hg 2+ detection based on Au nanoparticles and molybdenum selenide (Au NPs@MoSe 2 ) as well as the thymine-Hg 2+ -thymine (T-Hg 2+ -T) coordination. Herein, Au NPs@MoSe 2 not only could improve the sensitivity due to the large surface area and good electrical conductivity but also offered more sites to immobilize thiol-labeled T-rich hairpin DNA probes (P-1), which has a specific recognition for Hg 2+ and methylene blue-labeled T-rich DNA probes (MB-P). When Hg 2+ and MB-P exist, P-1 and MB-P can form a stable T-Hg 2+ -T complex. Then, methylene blue can be close to the electrode and detectable via differential pulse voltammetry (DPV). Benefiting from the specific recognition of T-Hg 2+ -T and the merits of Au NPs and MoSe 2 , the fabricated biosensor presented an ultrasensitive and highly selective performance. The DPV responses had a positive linear relationship with Hg 2+ concentrations over ten orders of magnitude from 1.0 × 10 -16 to 1.0 × 10 -7 mol L -1 . The detection limit was down to 1.1 × 10 -17 mol L -1 . Moreover, the developed sensor exhibited a promising application for trace Hg 2+ determination in water samples.