Analytical & Bioanalytical Electrochemistry
Volume:10 Issue: 4, Apr 2018

Electrochemical behaviors of carbidopa at the surface of the graphite screen printed electrode (SPE) modified with Cu(II) nanocomplex, [CuCl2(salophen)]. H2O (salophen=o-phenylenediaminebis(salicylidenaminato)) were studied. The oxidation peak potential of the carbidopa at a surface of Cu/SPE appeared at 360 mV that was about 100 mV lower than the oxidation peak potential at the surface of the traditional SPE under similar condition. On other hand, the oxidation peak current was increased for about two times at the surface of Cu/SPE compared to SPE. The linear response range and detection limit were found to be 0.5-700 μM and 0.1 μM, respectively. The proposed sensor was successfully applied for the determination of carbidopa in real samples.

The purpose of current study is to discuss the role of immersion time and passivation potential on the passive behavior and semiconducting properties of passive oxide films forming on Ti–6Al–4V titanium alloy in Ringer’s physiological solution at 37 °C. Polarization and impedance spectroscopy revealed that at longer immersion times and higher passivation potentials, Ti–6Al–4V shows a better passive response. Mott–Schottky (M–S) analysis revealed that the passive oxide films behaved as n-type semiconductor and immersion time and anodic passive potential did not affect the conductivity type of the passive oxide films. Moreover, M–S results indicated that fewer defects exist in the passive film at longer immersion times and higher anodic passive potential. The obtained results show that corrosion resistance of Ti–6Al–4V titanium alloy improves over the time and at higher passivation potentials due to the formation of passive films that are thicker yet less defective.

Carbon paste-modified imprinted zeolite electrodes as a potentiometric sensor for creatinine detection have been constructed. The modified electrodes were fabricated by mixing activated carbon, imprinted zeolite, and paraffin. The electrode that was prepared with a respective mass ratio of 45:15:40 showed the best performance in creatinine detection. In addition, the electrode showed a fast response time (less than 50 s), a wide range of measurement (10-7–10-5 M), and a low limit of detection (7.9×10-8 M). The presence of urea in the solution did not interfere in the detection of creatinine. The proposed creatinineselective sensor exhibited good reproducibility, accuracy, and a long lifetime. The creatinineselective electrode based on carbon paste-imprinted zeolite can be potentially used for creatinine detection in the medical field.

A graphite screen printed electrode was modified with iron oxide nanoparticles (Fe3O4 NPs). This modified electrode is proposed for electrochemical detection of hydroxylamine. Nanoparticles act as catalysts and also increase the surface area. Under optimized conditions, the oxidation peak currents, obtained by differential pulse voltammetry, of hydroxylamine increased linearly with increases in this concentration in the range of 1.0–125.0 μM. In this analysis, the detection limit was 0.4 μM. The developed electrochemical sensor was successfully applied to determine hydroxylamine in water samples.

Nanosized Fe3O4 particles were electrochemically prepared and deposited on reduced graphene oxide (rGO) sheets to prepare a nanocomposite for use in high performance capacitors. This was achieved using an electrophoretic/electrochemical deposition (EPD/ECD) approach for preparing the binder-free Fe3O4/rGO nanocomposite. The products were studies through XRD, IR, FE-SEM, VSM, TEM, and BET techniques. The mechanism of the formation of the nanocomposite through has also been described. The nancomposite further evaluated as an electrode material of use in supercapacitors and GCD tests indicated the composite to be able to deliver a specific capacitance (SC) of 478 F g−1 at 0.25 A g−1. Electrodes based on the material was also found to have a cycle life of 87.4% after 5000 GCD cycles. The results indicated the positive effects as a result of the synergy between Fe3O4 and rGO.

Conductor substrate-coating ilmenite (FeTiO3) electrodes developed for electrochemical sensors was investigated to high the photocurrent response, which influenced by transfer of electrons for photoelectrocatalytic processes. A highly ordered electrochemical process to obtain the electron response was employed as modeling reduction-oxidation (redox) reactions on working electrodes. This study utilized conductor substrates, i.e., indium tin oxide (ITO), titanium (Ti) plate, and TiO2/Ti then coated with FeTiO3 sol-gel. The results investigated the resistivity determined in ITO, Ti plate, TiO2/Ti, FeTiO3/ITO, FeTiO3/Ti, and FeTiO3.TiO2/Ti electrodes were 21.30 Ω, 0.37 Ω, 5.17 Ω, 117.04 Ω, 31.07 Ω, and 51.24 Ω, respectively. The Ti plate was a better conductor substrate than ITO was indicated by the highest performance with linear sweep voltammetry (LSV) and cyclic voltammetry (CV) methods. The FeTiO3.TiO2/Ti electrode performance had the highest activity compared with TiO2/Ti electrode as shown by photocurrent values of 1200 µA and 600 µA, respectively. This phenomenon indicates the photocurrent response of FeTiO3.TiO2/Ti possesses voltammogram stability for modeling the redox reactions. More importantly, this study to approach of chemical oxygen demand (COD) determination using FeTiO3 synthesized as modeling natural FeTiO3 extracted from mineral sands.

In this work, electrochemical synthesis was applied for the fabrication of ethylenediaminetetraacetic acid (EDTA) capped and metal-cations doped magnetite nanoparticles. The electro-deposition process was performed in the constant current mode using an aqueous electrolyte containing FeCl2.4H2O (0.5 g), Fe(NO3)3 .9H2O (2 g), MnCl2 .6H2O (0.5 g) and 0.2 g EDTA capping agent. The prepared samples were examined by analyses of XRD, IR, TG, EDAX, FE-SEM and VSM. The XRD results proved the magnetite crystal structure of the deposited powder. All chemical bands of EDTA were observed in the IR spectrum of the sample. And EDAX data indicated the doping of iron oxide nanoparticles by Mn2 cations during their electrochemical preparation. Based on the TG results, it was observed that EDTA capped layer has been formed onto the deposited iron oxide particles. The vibrating sample magnetometer (VSM) data (i.e. Ms=41.77 emu g–1, Mr=0.15 emu g–1 and Hc=3.97 G) was also confirmed the super-paramagnetic nature of the EDTA capped iron oxide nanoparticles. Based on the results, the cathodic electrochemical synthesis was proposed as a facile procedure for the preparation of EDTA-coated Mn2 doped SPIONs.

Glycine was electropolymerized on a carbon paste electrode (CPE) to form the polymer film in the electrooxidation process of the amino and carboxylic group containing compound by cyclic voltammetric technique and the electrochemical oxidation of resorcinol (RC) was studied in 0.2 M phosphate buffer solution (PBS) having pH 7.0. Modified carbon paste electrode (MCPE) shows a good electrocatalytic activity towards RC compared to bare carbon paste electrode (BCPE). The oxidation of RC at MCPE showed a linear relation versus concentration of RC in the range of 6×10-5 to 1×10-3 M with a detection limit 8.6×10-6 M.

The possibility of the inositol CoO(OH)-assisted electrochemical detection in alkaline media has been evaluated from the theoretical point of view. The correspondent mathematical model has been developed and analyzed by means of linear stability theory and bifurcation analysis. It was shown that CoO(OH) may serve as a modifier for inositol electrochemical detection in alkaline media, participating in the electroanalytical process as a reducent. The electroanalytical process is diffusion-controlled. The possibility of oscillatory and monotonic instabilities has also been verified.

Pristine crystalline superparamagnetic nanoparticles (SPNs) of magnetite (Fe3O4) were prepared from an additive-free aqueous solution of iron(III) nitrate salt though a novel one-pot electrodeposition method. The prepared nanoparticles were characterized by XRD, IR, VSM, DLS and FE-SEM. The SPNs were further grafted by poly(N-vinyl-2-pyrrolidone) during their deposition process. The PVP-grafting via electrochemical route was confirmed by IR, DSC-TGA and DLS analyses. The analyses results confirmed the proper phase (i.e. pristine magnetite), size (about 10 nm) and excellent super-paramagnetic nature (Ms=48.57emu g–1, Mr≈0.038 emu g–1 and Ce~1.35G) of the prepared PVP-grafted Fe3O4 nanoparticles for biomedical applications.