Electrodeposition synthesis of a NiO/CNT/PEDOT composite for simultaneous detection of dopamine, serotonin, and tryptophan

A novel NiO/carbon nanotube (CNT)/poly(3,4-ethylenedioxythiophene) (PEDOT) composite with a coaxial tubular nanostructure was successfully deposited on a glassy carbon electrode (GCE) through electrochemical processes. The outer PEDOT matrix has a high affinity for biomolecules, while the CNT inner layer has a strong electron-transport capacity. Hence, the NiO/CNT/PEDOT/GCE was used for the simultaneous determination of dopamine (DA), serotonin (5-HT), and tryptophan (Trp). Electrochemical responses of the NiO/CNT/PEDOT/GCE sensor were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry. Three well-separated oxidation peaks were observed in a mixed system containing DA, 5-HT, and Trp; the 5-HT–DA and Trp–5-HT potential separations were 160 and 324 mV, respectively, owing to the synergistic effect of NiO, CNT, and PEDOT. Linear responses were obtained for DA, 5-HT, and Trp in the 0.03–20, 0.3–35, and 1–41 μM concentration ranges, with detection limits of 0.026, 0.063, and 0.210 μM, respectively. In addition, it was possible to simultaneously determine the three analytes using the NiO/CNT/PEDOT composite, which suggests that the sensor has promising applicability.