Low-potential amperometric detection of dopamine based on MnO₂ nanowires/chitosan modified gold electrode

In this research, a manganese dioxide (MnO₂) nanowires/chitosan-modified gold (Au) electrode was successfully fabricated for amperometric determination of dopamine (DA) at a very low working potential (0.00 V vs. SCE). The electrochemical properties of the modified Au electrode were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The detection scheme was proposed to involve two major reactions: the chemical oxidation of DA to o-dopaminoquinone by MnO₂ nanowires, and then the electro-reduction of o-dopaminoquinone to DA at a low working potential (0.00 V vs. SCE), resulting in a distinct reduction response current. The modified Au electrode displays good amperometric response to DA in a wide concentration range 0.10 μM to 1.10 mM. The fabrication of MnO₂ nanowires/chitosan-modified Au electrode is simple and highly reproducible (RSD = 3.8%, n = 5). It exhibits excellent analytical performance in terms of low working potential (0.00 V vs. SCE), long shelf-life (90% of its initial response after 1-month storage) and high repeatability (RSD = 2.2%, n = 5). Finally, it was applied to determine DA in real samples directly with high accuracy (99%) and good recovery (99.7-103%), confirming its promising application in routine DA analysis.