Analytical & Bioanalytical Electrochemistry
Volume:10 Issue: 10, Oct 2018

In this study, the surface of 6061 Al alloy sheets were treated by plasma electrolytic oxidation (PEO) process to obtain oxide coatings. The voltage-time curves shows that the breakdown potential decreases with increasing of electrolyte concentration. The effect of concentration of PEO electrolyte on the corrosion behavior of the coatings was investigated. To assess the corrosion behavior, the potentiodynamic polarization plots were achieved and electrochemical impedance spectroscopy (EIS) measurements were carried out. The results of these analyses indicated that by reducing the concentration of sodium aluminate in the electrolyte, the corrosion rate of the coatings on the 6061 Al alloy significantly decreased. Moreover, the variation of sodium aluminate concentration in the electrolyte, led to modification of morphology and micro porosity of the coatings and alteration of the responses in the voltage-time. The coating processed in the electrolyte which contained 10 g L-1 sodium aluminate exhibited the best corrosion resistance.

A nanocomposite miniaturized electrode modified with cobalt ferrite nanoparticles (CoFe2O4 NPs) was used for determination of donepezil (DON) in presence of memantine HCl. The voltammetric results indicate that CoFe2O4 NPs can remarkably enhance electrocatalytic activity toward the oxidation of donepezil in buffer solution. Scanning electrochemical microscopy (SEM) and transmission electron microscopy (TEM) were used for characterization of CoFe2O4 NPs and the modified electrode surface. Characteristics of the electrochemical responses of the modified electrode toward donopezil were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). Experimental parameters including preconcentration time, scan rate and pulse height were optimized for high sensitivity. An In-situe electrochemical cleaning step was proposed for regeneration of the initial surface conditions of the electrode between measurements. The electrocatalytic oxidation current of donepezil was found to have a linear relation to concentration over the range from 5 to ≤ 20 µM by the DPV method. The average recovery of DON in Aricept tablet was 97.49 with a %RSD <0.5%. The modified electrode can be applied to the determination of DON in tablets and urine samples with satisfactory results.

Poly (alanine) modified carbon paste electrode (CPE) was fabricated for the determination of 5-amino salicylic acid (5-ASA) by cyclic voltammetric technique. The poly (alanine) modified CPE exhibited a high sensitivity towards the oxidation of 5-ASA. The effect of scan rate was found to be surface-controlled diffusion process and the concentration study was conducted between the range of 20-180 µM. The limit of detection (3 S/M) and limit of quantification (10 S/M) were calculated and found to be 0.23 µM and 0.76 µM respectively. Because of high sensitivity in the electro-oxidation, the fabricated poly (alanine) modified CPE can be used as a promising electrochemical sensor for the determination of 5-ASA in both commercial as well as in pharmaceutical samples.

Here, an electrochemical synthesis method is reported for the facile preparation of Ni doped iron oxide grafted with biocompatible polymers (i.e. PVP and PEG). PVP- and PEG coated Ni doped iron oxides (i.e. PVP-Ni-IOs and PEG-Ni-IOs) were fabricated through cathodic electrochemical deposition. The aqueous electrolyte containing 2.4 g Fe(NO3)3, 1g FeCl2, 0.2NiCl2 and 0.5 g PVP or 0.5 g PEG was used as the deposition media. The crystal structure, morphology, chemical composition, purity, and magnetite properties of the prepared PVP-Ni-IOs and PEG-Ni-IOs samples were scrutinized through XRD, FTIR, FESEM/EDAX and VSM techniques. The presence of PVP and PEG on the surface of the IOs was confirmed via EDS and FTIR analyses. XRD and FE-SEM probes showed that the products are magnetite crystal structure with the particle size about 20 nm. EDAX results verified that the samples have metal ion doped Fe3O4 (about 7%Ni cations) composition. In addition, VSM measurement confirmed that the both PVP-Ni-IOs and PEG-Ni-IOs samples have superparamagnetic nature, showing the saturation magnetizations of 52.98 and 48.51 emu/g, respectively.

In this study, the photochemical compositions of the methanolic extracts of the leaves and root parts from the Anabasis aretioides were determined, as well as the evaluation of their effect as a green corrosion inhibitor of mild steel (E24) in a neutral solution (NaCl 3.5%). The photochemical screening performed for the methanolic extracts showed the presence of the polyphenols, tannins, alkaloids, reducing compounds and trace amounts of the proteins, carotenoids, coumarins and cardiac glycosides. The electrochemical study was carried out by using the polarization measurements and electrochemical impedance technique. The analyzing of the surface of the metal was carried out by the scanning electron microscope (SEM) coupled with the EDS. The inhibition efficiency increased with increasing the concentrations and reached the values of 86 and 87% respectively for the 10% concentration of methanolic extracts from the leaves and root parts of the Anabasis aretioides plant. The both inhibitors act as a mixed type, with the predominance of the cathodic efficiency for the leaves extract and the anodic efficiency for root extract.

In this work, a sensitive Sudan I electrochemical sensor was assembled using NiFe2O4 nanoparticles modified screen printed electrode. Due to the synergetic effect of NiFe2O4 nanoparticles displayed high electrochemical activity with well-defined voltammetric peaks of Sudan I oxidation and lower overpotential compared with unmodified electrode. According to the results of differential pulse voltammetry (DPV), under optimized conditions, a good linear response was observed for the concentration of Sudan I in the range of 0.1–100.0 μM with a detection limit of 0.05 μM. The developed electrochemical sensor was successfully applied to determine Sudan I in water samples. This study indicated that NiFe2O4 nanoparticles based electrochemical sensor can be a promising and reliable tool for rapid analysis of Sudan I.

Novel substituted quinazolinone derivatives based on 8-hydroxyquinoline were synthesized and identified by hydrogen-1 nuclear magnetic resonance, carbon-13 nuclear magnetic resonance, and elemental analysis. The corrosion inhibition of these compounds in 1 M HCl Solution for mild steel was evaluated using potentiodynamic polarization measurements, electrochemical impedance spectroscopy, weight loss measurements. It is showed that these compounds are good inhibitors for mild steel corrosion in 1.0 M HCl solution which act as mixed type inhibitors. So, the inhibition efficiency was increased with inhibitor concentration in the order of QZn>QZ which depended on their molecular structures. Maximum values of inhibition efficiency 96% and 79% were obtained at low concentration (10-3 M) for QZn and QZ respectively. It is found also that the inhibition efficiency of these compounds slight decrease with temperature. In addition, the thermodynamic adsorption parameters at different concentrations were investigated and discussed. The both inhibitors as good acid corrosion inhibitors and were found to obey Langmuir adsorption isotherm. Additionally, the corrosion properties were also investigated by UV-visible spectrophotometry to obtain information on bonding mechanism between the metallic surface and the inhibitor. Scanning Electron Microscopy (SEM) was performed and discussed for surface study of uninhibited and inhibited mild steel samples.

In this paper, cerium doped iron oxide (Ce-IO) is cathodically electro-synthesized from electrolyte containing iron(III) nitrate, iron(II) chloride and cerium chloride by applying direct current of 10 mA cm–2 for 30 min. The analysis data obtained from X-ray diffraction (XRD), field emission electron microscopy (FE-SEM) and energy-dispersive X-ray (EDX) showed that the synthesized Ce-IO sample has composition of cerium cations doped magnetite crystal structure and average particle size of 20 nm. This developed electrochemical procedure can be proposed as a one-pot electrosynthesis platform for fabrication of nanoparticles of cerium doped iron oxide. Furthermore, the prepared Ce-IO was used as supercapacitor electrode material and its charge storage ability was specified through cyclic voltammetry (CV) and galvanostat charge-discharge (GCD) tests. The obtained charge storage data indicated that Ce-IO sample provide SCs as high as 168 and 125 F g−1 at the discharge loads of 1 and 3 A g−1, respectively, and capacity retentions of 90.4% and 81.5% after 1000 GCD cycling. These results proved the suitability of the electrosynthesized sample for use in supercapacitors. Also, the VSM data confirmed better superparamagnetic properties of Ce-IO sample (Mr=0.14 emu g–1 and HCi=2.44 G) as compared with undoped iron oxide sample (Mr=0.95 emu g–1 and HCi=14.6 G) resulting from their lower Mr and Hci values.

The possibility of daclatasvir electrochemical detection, assisted by conducting polymer-based sulfoacid, was analyzed by theoretical point of view. It was shown, that the conducting polymer sulfoacid may serve as an excellent electrode modifier, permitting the use of more flexible pH-window for analysis. The steady-state may be maintained stable in the vast parameter region. The electroanalytical response has to be clear and easy to interpret. The possibility for electrochemical instabilities (electrochemical oscillations and monotonic instability) in this system has also been studied.

The compound ability of 5,5-diphenylimidazolidine-2,4-dione (PID) against mild steel corrosion in 1 M HCl solution was investigated by various techniques. It is found that this compound is an effective inhibitor against corrosion which its inhibition efficiency increases with its concentration. The potentiodynamic polarization curves indicated that PID acts as mixed inhibitor. In addition, these results were confirmed by the electrochemical impedance spectroscopy where the resistance transfer of PID increases by its concentration.
Thus, the inhibitor adsorption which is studied on the mild steel surface conforms to the Langmuir adsorption isotherm. On the other hand, the quantum chemical parameters were calculated by using the density functional theory (DFT) method with the 6-31G/B3LYP base (d, p) and Monte Carlo simulation. It is shown that PID adsorbs in parallel ways on the metal surface of low energy iron. Finally, the correlation between theoretical and experimental results is in good agreement.