Omolola E Fayemi, Abolanle S Adekunle and Eno E Ebenso*
Electrochemical properties and sensor application of multi-walled carbon nanotubes (MWCNTs), doped with metal oxides [(MO=nickel oxide (NiO), zinc oxide (ZnO) and iron oxide (Fe3O4)] nanoparticles was investigated using FTIR, XRD, UV-vis spectroscopy, Raman spectroscopy, TEM, SEM, EDX, and cyclic voltammetry techniques. Electrochemical oxidation of dopamine on a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes doped with metal oxides (GCE/MWCNT/NiO, GCE/MWCNT/ZnO, GCE/MWCNT/Fe3O4) was examined by cyclic voltammetry, EIS and square wave voltammetry in 0.1 M phosphate buffer solution PBS at pH 7. The results were compared with those obtained on bare GCE, GCE/MWCNT and MO GCE modified electrodes (GCE/NiO, GCE/ZnO, GCE/Fe3O4). All electrodes were conditioned at potential of 0.2V (vs Ag/AgCl, sat’d KCl) in DA solution for EIS experiment. It was found that the multi- walled carbon nanotubes improve remarkably the reactivity of NiO, ZnO and Fe3O4 for dopamine oxidation. The GCE/MWCNT/NiO, GCE/MWCNT/ZnO, GCE/MWCNT/Fe3O4 electrodes exhibited good linear properties in the concentration range from 4 × 10-5 μM to 6.25 μM for the quantitative analysis of dopamine (DA) with a limit of detection of 7.99 × 10-12 M, 3.742 × 10-7 M and 1.386 × 10-6 M respectively. The limit of detection of GCE/MWCNT/NiO was better than the other two nanocomposites modified electrodes. The interference study also revealed no AA interference signal at AA concentration 1000 times that of DA. The DPV techniques give well distinct peaks for the DA and AA and a wider separation potential. The prepared electrode exhibited satisfactory stability and long shelf life when stored at ambient conditions. It has been demonstrated that the GCE/MWCNT/NiO modified electrode can be successfully used for the assay of dopamine in some real samples.
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