Composite material based on ZIF-8, reduced graphene oxide, and Nafion as electrode modifier for dopamine electrooxidation

A zeolitic imidazolate framework (ZIF-8), a subclass of metal-organic frameworks (MOFs) was synthesised and morpho-structural characterised by X-ray diffraction (XRD), thermogravimetric analysis (TGA), FT-IR and Raman spectroscopy, N2 adsorption/desorption isotherms and scanning electron microscopy (SEM). A ZIF-8–rGO–Nafion/GCE modified electrode was prepared by the drop-casting method from a solution containing reduced graphene oxide (rGO), ZIF-8 and Nafion. The modified electrode was characterised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and square-wave voltammetry (SWV) for dopamine (DA) detection. The influence of scan rate and pH (by CV), corroborated with EIS data, led to estimating different electrochemical parameters of the dopamine oxidation process. By SWV, ZIF-8–rGO–Nafion/GCE modified electrode showed good analytical performances, such as: linear domain 0.5–1.4 μM, limit of detection of 0.051 μM dopamine when alone, and 0.069 μM dopamine in the simultaneous detection with paracetamol and citric acid, good electrode stability (RSD 7.43 %) and reproducibility (RSD 1.72 %), expressed for peak current intensities. A standard addition method applied to DA samples led to recovery values ranging from 110.8 % to 112.6 %, proving the reliability of the ZIF-8–rGO–Nafion/GCE modified electrode to be used in the analysis of real samples.