Square-Wave Voltammetric Detection of Dopamine at a Copper-(3-Mercaptopropyl) Trimethoxy Silane Complex Modified Electrode

Abstract

Square-wave voltammetric detection of dopamine was studied at a copper (Cu)-(3-mercaptopropyl) trimethoxy silane (MPS)-complex modified electrode (Cu-MPS). The modification of the electrode was based on the attachment of MPS onto an electrochemically activated glassy carbon electrode (GCE) by the interaction between methoxy silane groups of MPS and surface hydroxyl groups and followed by the complexation of copper with the thiol groups of MPS. The surface of the modified electrode was further coated by a thin layer of Nafion film. The surface of the Nafion coated MPS-Cu complex modified electrode (Nafion/Cu-MPS) was characterized using cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectrometry. The modified electrode exhibited an excellent electrocatalytic activity towards the oxidation of dopamine, which was oxidized at a reduced potential of +0.35 V (vs. Ag/AgCl) at a wider pH range. Various experimental parameters, such as the amount of copper, the pH, and the temperature were optimized. A linear calibration plot was obtained in the concentration range between 8.0×10−8 M and 5.0×10−6 M and the detection limit was determined to be 5.0×10−8 M. The other common biological compounds including ascorbic acid did not interfere and the modified electrode showed an excellent specificity to the detection of dopamine. The Nafion/Cu-MPS modified electrode can be used for about 2 months without any significant loss in sensitivity.