Fabrication of Amine-Modified Magnetite-Electrochemically Reduced Graphene Oxide Nanocomposite Modified Glassy Carbon Electrode for Sensitive Dopamine Determination

Abstract

Amine-modified magnetite (NH2–Fe3O4)/reduced graphene oxide nanocomposite modified glassy carbon electrodes (NH2–Fe3O4/RGO/GCEs) were developed for the sensitive detection of dopamine (DA). The NH2-Fe3O4/RGO/GCEs were fabricated using a drop-casting method followed by an electrochemical reduction process. The surface morphologies, microstructure and chemical compositions of the NH2–Fe3O4 nanoparticles (NPs), reduced graphene oxide (RGO) sheets and NH2–Fe3O4/RGO nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The electrochemical behaviors of DA on the bare and modified GCEs were investigated in phosphate buffer solution (PBS) by cyclic voltammetry (CV). Compared with bare electrode and RGO/GCE, the oxidation peak current (ipa) on the NH2–Fe3O4/RGO/GCE increase significantly, owing to the synergistic effect between NH2–Fe3O4 NPs and RGO sheets. The oxidation peak currents (ipa) increase linearly with the concentrations of DA in the range of 1 × 10−8 mol/L – 1 × 10−7 mol/L, 1 × 10−7 mol/L – 1 × 10−6 mol/L and 1 × 10−6 mol/L – 1 × 10−5 mol/L. The detection limit is (4.0 ± 0.36) ×10−9 mol/L (S/N = 3). Moreover, the response peak currents of DA were hardly interfered with the coexistence of ascorbic acid (AA) and uric acid (UA). The proposed NH2–Fe3O4/RGO/GCE is successfully applied to the detection of dopamine hydrochloride injections with satisfactory results. Together with low cost, facile operation, good selectivity and high sensitivity, the NH2–Fe3O4/RGO/GCEs have tremendous prospects for the detection of DA in various real samples.

Morphologically Tunable MnO2 Nanoparticles Fabrication, Modelling and Their Influences on Electrochemical Sensing Performance toward Dopamine

“…As presented in Figure 5B, the oxidation peak currents (i pa ) increase linearly with scanning rate (v), suggesting the electrochemical oxidation of dopamine is an adsorption-controlled process. This result is consistent with previous reports [34,[37][38][39][40][41], and also favors our assumption for model simulation. …”

“…As is well known, electrocatalytic oxidation of dopamine on the surface of modified electrodes is mainly controlled by the adsorption process [34,[37][38][39][40][41]. Hence, the response peak current can be calculated according to the Laviron Equation [45]:…”

“…GO was prepared from cheap graphite powder by modified Hummers method referred to our previous reports [36][37][38]. The resulting GO was dispersed in 100 mL of deionized water under ultrasonication for 2 h, centrifuged twice at 6000 rpm to remove trace precipitates, and the supernatant was taken out to obtain a gold GO solution with approximately 1 mg/mL.…”

“…The response peak currents and peak current densities among three various morphologies of MnO 2 -RGO/GCE have been compared to find out the main factors on the enhancement of electrochemical response. The response peak current is supposed to be proportional to the surface area of the modified electrode, because of the presence of an adsorption-controlled process during electrochemical oxidation of dopamine [34,[37][38][39][40][41]. Based on the hypothesis, spatial models for three various morphologies of nano-MnO 2 were established to compare their specific surface area, and find the main factors on the specific surface area.…”

“…The MnO 2 -reduced graphene oxide modified glass carbon electrode (MnO 2 -RGO/GCE) was prepared by drop-casting MnO 2 -GO dispersion on the surface of GCE and subsequently an electrochemical reduction process [36][37][38]. The response peak currents were measured by second-order derivative linear sweep voltammetry in dopamine solution.…”