This work describes and compares the electron transport and electrocatalytic properties of chemically synthesised cobalt oxide (Co3O4) and nickel oxide (NiO) nanoparticles grafted onto graphene oxide (GO)/acid treated multi-walled carbon nanotubes decorated glassy carbon electrode. Successful synthesis of these nano materials was confirmed using microscopic and spectroscopic techniques. Successful modification of electrode was confirmed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Results showed that the GCE-fMWCNT-NiO and GCE-fMWCNT- Co3O4 nanocomposite modified electrodes gave faster electron transfer process in both 5 mM Ferri/Ferro ([Fe(CN)6]3−/4−) redox probe and 0.1 M phosphate buffer solution (PBS). GCE-fMWCNT-NiO and GCE-fMWCNT-Co3O4 electrodes also gave enhanced Pyrene oxidation current compared with bare GCE and other electrodes studied. The charge transfer resistance, electron transfer rate constant (ks), Tafel value, limit of detection (LoD), sensitivity, adsorption equilibrium constant (β), Gibbs free energy change due to the adsorption (ΔGoads) of Pyrene onto the GCE-fMWCNT-Co3O4 are established and discussed. The LoD and ΔGoads for Pyrene were 1.62 nM and -15.8 kJ/mol, respectively, over a linear dynamic range of 1.0 x 10-9 – 100 x 10-9 M. The electro-oxidation of Pyrene was a diffusion dominated process, but demonstrated adsorption thought to be as a result of a combination of the strong pi-pi electron interactions between Pyrene and the MWCNT, thus the thin film formed on the surface of the electrode by the analyte and its reaction intermediates. The LoD compared favourably with literature reported values. GCE-fMWCNT-Co3O4 gave better performance to Pyrene electrooxidation, good resistance to electrode fouling, higher catalytic rate constant and lower limit of detection. The sensor is easy to fabricate, cost effective and could be used for routine determination of Pyrene in food and environmental matrices.
Electrochemical Rutin Sensor Based on Graphene Oxide and Functionalized Multiwall Carbon 