A ratiometric electrochemical sensor for dopamine detection based on hierarchical manganese dioxide nanoflower/multiwalled carbon nanotube nanocomposite modified glassy carbon electrode

A ratiometric electrochemical sensor is developed for dopamine detection based on hierarchical manganese dioxide (MnO2) nanoflower/multiwalled carbon nanotube (MWCNT) nanocomposite modified glassy carbon electrode (GCE). The hierarchical MnO2 nanoflower was electrodeposited onto the electrochemically pretreated GCE modified with MWCNT (MWCNT/EPGCE) to prepare an inner reference electrochemical probe. The fabrication process of the MnO2/MWCNT/EPGCE electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The introduction of MWCNT can not only improve the electrochemical signals of dopamine, but also increase MnO2 signals. The origin of the dual signal enhancement for both dopamine and MnO2 is reasonably explained by using electrochemical techniques. The results show that the high sensitivity for dopamine detection at MnO2/MWCNT/EPGCE predominately originates from the high surface coverage of dopamine, and the signal enhancement of MnO2 on MWCNT/EPGCE is ascribed to the electrocatalytic activity of MWCNT towards the electrodeposited MnO2 and the increase of MnO2 surface coverage. This sensor based on MnO2/MWCNT/EPGCE has a low detection limit of 0.17 mu M and a wide linear range from 0.5 to 30.0 mu M. In addition, the sensor displays high selectivity, good reproducibility, and good stability, and can be applied for dopamine detection in human serum samples with satisfactory results. (C) 2019 Elsevier B.V. All rights reserved.