An ultrasensitive electrochemical sensor based on in situ synthesized manganese dioxide/gold nanoparticles nanocomposites for rapid detection of methylmercury in foodstuffs

Abstract

The inclusion of methylmercury (CH₃Hg⁺) in the environment and food chain has aroused wide concern due to its high neurotoxicity and cumulative effects. Herein, a highly sensitive electrochemical sensor based on manganese dioxide (MnO₂)/gold nanoparticles (AuNPs) composites is fabricated for CH₃Hg⁺ detection in food. The MnO₂/AuNPs nanocomposites were synthesized in situ on the surface of a glassy carbon electrode by an electrodeposition method and were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The resulting MnO₂/AuNPs modified electrode exhibited a large active surface area, enhanced conductivity and excellent electrocatalytic activity toward CH₃Hg⁺ due to the synergistic effect of MnO₂ and AuNPs. Square wave anodic stripping voltammetry (SWASV) was used as the sensing technique for CH₃Hg⁺, and the stripping peak current showed a good linear relationship with CH₃Hg⁺ concentration in the range of 0.7–15 μg L⁻¹ with a detection limit of 0.051 μg L⁻¹. Besides, the interference from Hg²⁺ associated with CH₃Hg⁺ detection can be avoided by the addition of diethylene triamine pentaacetic acid (DTPA). The as-prepared sensor was applied to detect CH₃Hg⁺ in various food samples with satisfactory recoveries, thus providing a promising platform for rapid screening of methylmercury residues.