ZnO@MnO2 nanocomposite modified carbon paste electrode for electrochemical detection of dopamine

Abstract

In this study, we have compared the performance of a bare carbon paste electrode (BCPE) against the ZnO@MnO2 nanocomposite modified carbon paste electrode (MCPE) in the electrochemical determination of dopamine (DA). Chemical and structural features of the ZnO@MnO2 nanocomposites were characterized using scanning electron microscopy (SEM), energy dispersive X-Ray analysis (EDX), transmission electron microscopy (TEM), X-Ray diffraction (XRD), thermo-gravimetric analysis (TGA) with differential thermal Analysis (DTA) and Brunauer-Emmet-Teller (BET) surface area analysis. The cyclic voltammetry (CV) measurement of the ZnO@MnO2 nanocomposite MCPE showed better oxidative catalytic activity (3.6 μA) towards the DA than BCPE with higher efficiency (44.50%) in sensing the dopamine, making MCPE suitable for developing biosensors. The electrochemical studies were carried out in 5 × 10−5 M DA and obtained results were measured in the potential range of −0.2 to 0.6 V vs. saturated calomel electrode (SCE). The electrochemical performance of electrochemical impedance spectroscopy (EIS) and Tafel technique were measured for the BCPE and MCPE using 0.2 M phosphate buffer to maintain pH 7.2 with the scan rate of 50 mV/s. The redox peak current for MCPE Vs scan rate had good linearity with correlation coefficients of R2 = 0.9996, which represents the diffusion controlled process was under controlled electron transfer reaction. It is expected that the good electrocatalytic behavior of MCPE can be utilized for the fabrication of biosensors.