Electrochemical detection of dopamine via pencil graphite electrodes modified by Cu/CuxO nanoparticles

A novel voltammetric biosensor was developed through the modification of pencil graphite electrodes (PGEs) with Cu/CuxO nanoparticles. Initially, Cu nanoparticles (CuNPs) were electrodeposited on the PGEs surface at various deposition potentials and times. Then, by applying 20 voltammetric cycles in a 0.1 M sodium hydroxide solution, the CuNPs were converted into copper oxide. The dopamine (DA) detection ability of modified electrodes in 0.1 M PBS (pH = 5.8) was consequently evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The highest peak current (I-p) for DA electrooxidation was observed by the electrode modified at -0.6 V vs. Ag/AgCl and 150 s. This optimized electrode also exhibited a low limit of detection (LOD) of 1.06 mu M, and a high sensitivity of 0.51 mu A/mu M being higher than that of the biosensors modified by rod-shaped CuO, ZnO, TiO2 and AuNPs. The optimal biosensor showed a high selectivity (E-UA - E-DA = 0.14 V) for DA at pH 5.8, while it was unable to detect Ascorbic acid (AA). In order to obtain more details, phase and morphology identification of the deposited NPs were studied by X-ray diffraction and field emission scanning electron microscopy, respectively. In addition, the effect of scan rate and pH of test solution on DA detection ability of optimal biosensor was evaluated and optimum values were determined. It was also found that the electron transfer process for DA at the modified electrode surface is reversible. (C) 2020 Elsevier B.V. All rights reserved.