Ultrasensitive electrochemical sensor for mercury ion detection based on molybdenum selenide and Au nanoparticles via thymine–Hg2+–thymine coordination

Abstract

An ultrasensitive and specific-selection electrochemical sensor was constructed for Hg²⁺ detection based on Au nanoparticles and molybdenum selenide (Au NPs@MoSe₂) as well as the thymine–Hg²⁺–thymine (T–Hg²⁺–T) coordination. Herein, Au NPs@MoSe₂ 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 Hg²⁺ and methylene blue-labeled T-rich DNA probes (MB-P). When Hg²⁺ and MB-P exist, P-1 and MB-P can form a stable T–Hg²⁺–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–Hg²⁺–T and the merits of Au NPs and MoSe₂, the fabricated biosensor presented an ultrasensitive and highly selective performance. The DPV responses had a positive linear relationship with Hg²⁺ 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 Hg²⁺determination in water samples.