RuO2 nanowires on electrospun CeO2-Au nanofibers/functionalized carbon nanotubes/graphite oxide nanocomposite modified screen-printed carbon electrode for simultaneous determination of ascorbic acid, dopamine and serotonin

Neurotransmitters, such as dopamine (3,4-dihydroxyphenylethylamine, DA) and serotonin (5-hydroxytryptamine, 5-HT) are chemicals in the brain that transmit signals from the neurons to the target cells. Simultaneous measurement of DA and 5-HT is particularly important since these molecules coexist typically and their relative levels have implications in many diseases and response to drug treatments [1]. Ascorbic acid (AA) is a common interference that coexists with DA and 5-HT in the brain at concentrations 100–1000 times higher than that of DA [2]. In this work, for the first time, a novel hybrid architecture of CeO2-Au nanofibers (CeO2-AuNFs) and single-crystalline RuO2 nanowires (RuO2NWs) have been synthesized by a combination of electrospinning and thermal annealing process. The CeO2-Au hybrid nanofibers were fabricated by the electrospinning technique and then annealed in air [3]. The amorphous Ru(OH)3 precursors at relatively low temperature were efficiently converted into highly single-crystalline RuO2NWs on electrospun CeO2-AuNFs. The electrospun CeO2-AuNFs, RuO2NWs–CeO2-AuNFs and other nanostructure were characterized by different methods such as field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), energy dispersive X-ray analysis (EDS) and fourier transform infrared spectroscopy (FT–IR). Novel RuO2NWs–CeO2-AuNFs hybrid architecture in combination with graphite oxide (GO) and functionalized multiwalled carbon nanotubes (f-MWCNTs) further employed to modify screen printed carbon electrode (SPCE (in order to develop a sensitive electrochemical method with suitable properties for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and serotonin (5-HT). The dependence of the oxidation peak currents on the pH of the solution, amount of modifier, scan rate and concentration of the analytes was studied to optimize the experimental conditions. Under the optimum operating conditions, linear calibration curves were obtained in the range of 0.5–100, 0.01–120 and 0.01–150 μM with a detection limit of 160, 2.8 and 2.4 nM for AA, DA and 5-HT, respectively. The proposed electrochemical sensor provided a good performance for the simultaneous determination of AA, DA and 5-HT by not only significantly improved their current responses, but also decreased the overpotentials as well as resolved the overlapping of the oxidation peak potentials. This sensor was successfully applied for the determination of AA, DA and 5-HT in biological fluids and pharmaceutical samples.