Electron Transfer Coefficient Research Articles

A Reliable Cyclic Voltammetry Technique for the Degradation of Salicylaldehyde: Electrode Kinetics

Salicylaldehyde (SA) is used in numerous biological, pharmaceutical, and industrial applications. Releasing effluents from these industries contaminates water. So the degradation of salicylaldehyde is necessitated. The electrochemical degradation of salicylaldehyde in buffered media was studied using the eco-friendly cyclic voltammetry (CV) technique on a platinum electrode at different scan rates. Kinetic and electrochemical parameters were evaluated for the reaction such as standard heterogeneous rate constant (k0,2.468×103 s-1 ), anodic electron transfer rate constant (kox,2.507×103 s-1), electron transfer coefficient of reaction (?,0.673), and formal potential (E0, 1.0937) under the influence of scan rate. The nature of the reaction is found to be diffusion controlled. The concentration study in the range of 1 mM to 4 mM was calibrated. The limit of detection and the limit of quantification were calculated to be 0.0031 mM and 0.0103 mM respectively.

Reduced graphene oxide/titanium carbide MXene nanocomposite‐modified electrode for electrochemical hemoglobin biosensor

AbstractIn this work, reduced graphene oxide (rGO) and titanium carbide (Ti3C2Tx) nanocomposite was prepared by the self‐assembly method and used for electrode modification. The rGO‐Ti3C2Tx nanocomposite was examined by scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy. Then, an electrochemical hemoglobin (Hb) biosensor was prepared on the nanocomposite‐modified electrode and used for the determination of trichloroacetic acid (TCA) and hydrogen peroxide (H2O2). Direct electrochemistry of Hb on the modified electrode was examined with the calculations of the electron transfer number, electron transfer coefficient, and the reaction rate constant. The presence of the rGO‐Ti3C2Tx nanocomposite on the electrode can improve the effective surface area and biocompatibility of the electrode interface, obtaining a higher electron transfer rate. Furthermore, this electrochemical Hb biosensor exhibited excellent stability, reproducibility, and repeatability in TCA and H2O2 analyses.

Production of copper-graphene nanocomposite as a voltammetric sensor for determination of anti-diabetic metformin using response surface methodology

In this paper, application of a sensitive electrochemical technique assisted with multivariate optimization methods is presented for measurement of anti-diabetic metformin (MET) drug in pharmaceutical and serum samples. The sensitive electrochemical sensor was modified carbon paste electrode by copper-graphene nanocomposite (Cu-G/CPE). Firstly, synthesis of graphene (G) and copper-graphene (Cu-G) were performed and X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and N2 adsorption–desorption isotherm were applied to specify the structure of them. FESEM of Cu-G shows carbon sheets were decorated with some dense layer of well-dispersed uniform CuNPs with a type size around 50 nm. Also, the XRD pattern of Cu-G displays several peaks for Cu, which approves the formation of Cu-G nanocomposite. Next, the G and Cu-G are used for modification of a carbon paste electrode (CPE) surface. Results from response surface methodology indicated that solution pH of 12, 11% of Cu-G nanocomposite in the modified CPE, accumulation potential (0.2 V) and accumulation time (80 s) outcomes in the maximal current density. The electrochemical behavior of MET at the Cu-G/CPE surface are investigated by differential pulse voltammetry (DPV), cyclic voltammetry (CV), and chronoamperometry techniques. The electron-transfer coefficient, catalytic rate constant and diffusion coefficient are found to be 0.84, 6.27 × 106 cm3 mol−1 s−1 and 1.07 × 10−8 cm2 s−1, respectively. Under the optimum conditions, the detection limit and linear dynamic range were found to be 3.4 µM and 10.4–1125.0 µM by DPV technique, respectively. The Cu-G/CPE exhibited good reproducibility, stability and high recovery and it has low cost, low background current, ease of surface renewal. The Cu-G/CPE has better poisoning tolerance ability than bare CPE for electro-oxidation of MET and is a superior sensor for the long-term action. Furthermore, the proposed method can be applied as a valorous analytical method in the quality control of the pharmaceutical industry.

Electrosynthesised CdS@ZnS quantum dots decorated multi walled carbon nanotubes for analysis of propranolol in biological fluids and pharmaceutical samples

Quantum dots (QDs) based electrochemical assays have received a great deal of attention. They preserve the outstanding characteristics of electrochemical methodologies with respect to simplicity, ease-of-use, and cost-effective instrumentation. In this work, a new challenge was opened up to explore the electrochemical features of CdS@ZnS as two well-known semiconductors for analytical utilizations. Here, CdS@ZnS core–shell QDs have been prepared electrochemically and applied for electrochemical sensor development in this approach. An activated glassy carbon electrode modified with a thin film of multi walled carbon nanotube was coated with CdS@ZnS QDs (activated GCE/MWCNTs/CdS@ZnS) as a thin uniform layer for analysis and monitoring of propranolol (PRO), a non-selective β-blocker drug. Field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the surface morphology of the developed electrodes. The results demonstrated that CdS@ZnS QDs were well-dispersed on the activated GCE/MWCNTs surface and were able to enhance the number of adsorbed analyte molecules. The electrochemical behavior of the PRO was studied at the modified electrode surface. The kinetic parameters of electron transfer coefficient (α) and the catalytic rate constant (kcat) for the electron transfer between PRO and the modified electrode were calculated. The electrochemical oxidation mechanism of PRO was also investigated by square wave voltammetry (SWV). Under optimal conditions, the proposed sensor demonstrated a linear response towards propranolol in the range of 0.06–27 μmol L−1 and a detection limit of 12 nmol L−1. Furthermore, the analytical performance of the developed sensor was evaluated for measuring propranolol in biological fluids and pharmaceutical samples. The observed promising results confirm the suitability of the developed sensor for applications in measuring complex materials.

Study of the electrochemical oxidation of 4,6-dimethyldibenzothiophene on a BDD electrode employing different techniques

• Study of the oxidation steps of 4,6-DMDBT by different techniques using a BDD anode. • 4,6-DMDBT was removed after 60 min of electrolysis at E an = 1.50 V. • Selective oxidation of 4,6-DMDBT to sulfoxide or sulfone. • The conversion depended on concentration, applied potential, and water content. • A small amount of dimers was formed during the electrochemical oxidation. The electrochemical oxidation of 4,6-dimethyldibenzothiophene (4,6-DMDBT) at low concentrations on a BDD anode was investigated in a monophasic acetonitrile (93.5% v/v)–water (6.5% v/v, 0.01 M LiClO 4 ) solution. Two oxidation steps related to the sequential formation of sulfoxide and sulfone derivatives were identified. Kinetic parameters such as the electron transfer coefficient α, the number of electrons n α involved in the rate-determining step, the total number of electrons n , the reaction rate constant k 0 and the diffusion coefficient D of 4,6-DMDBT for the first transformation were determined by cyclic voltammetry, differential pulse voltammetry (DPV), square wave voltammetry and bulk electrolysis under potentiostatic conditions. The process was bielectronic with α = 0.57, n α = 1, k 0 = 7.46 × 10 −6 cm s −1 and D = 2.30 × 10 −6 cm 2 s −1 . DPV was the most sensitive electroanalytical technique. Using 27 mg L −1 of 4,6-DMTDB, DPV allowed determining a conversion of 91% to sulfoxide after 60 min of electrolysis in a BDD/BDD cell at an anodic potential of 1.50 V, with an apparent rate constant of 0.034 min −1 . The electrochemical characterization was corroborated via gas chromatography–mass spectrometry and ultra-high performance liquid chromatography coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry, confirming the formation of the sulfoxide in the first step and the sulfone in the second one as main products, alongside a minor proportion of dimers.

On the use of green concrete composite as a nuclear radiation shielding material

In the present study, the samples of sustainable green concrete composites reinforced with hematite were prepared by partially replacing Ordinary Portland Cement (OPC) with flyash. The mechanical and gamma radiation shielding parameters have been measured experimentally for these prepared concrete composites. The experimental measurements were performed by using narrow beam transmission geometry (total scatter acceptance angle (θsc) = 1.78°) with NaI(Tl) spectroscopy in the gamma photon energy range of 59.54 keV–1332 keV. These experimentally measured values of linear attenuation coefficient are further used to calculate the values of half value layer, mass attenuation coefficient, effective atomic number, electron density, exposure build up factor, Klein-Nishina electronic, electron transfer and Compton mass attenuation coefficients. The fast neutron removal cross sections (∑R cm−1) were calculated for the concrete samples under investigations. The experimental values of mass attenuation coefficient have been compared with the results of theoretical values obtained by using winXCOM computer software and FLUKA simulations code. Excellent agreements have been observed between experimental, theoretical and simulation results.

PH Overpotential for Unveiling the pH Gradient Effect of H + /OH − Transport in Electrode Reaction Kinetics

pH Overpotential for Unveiling the pH Gradient Effect of H ⁺ /OH ⁻ Transport in Electrode Reaction Kinetics

The effects of the chemical environment of menaquinones in lipid monolayers on mercury electrodes on the thermodynamics and kinetics of their electrochemistry

The effects of the chemical environment of menaquinones (all-trans MK-4 and all-trans MK-7) incorporated in lipid monolayers on mercury electrodes have been studied with respect to the thermodynamics and kinetics of their electrochemistry. The chemical environment relates to the composition of lipid films as well as the adjacent aqueous phase. It could be shown that the addition of all-trans MK-4 to TMCL does not change the phase transition temperatures of TMCL. In case of DMPC monolayers, the presence of cholesterol has no effect on the thermodynamics (formal redox potentials) of all-trans MK-7, but the kinetics are affected. Addition of an inert electrolyte (sodium perchlorate; change of ionic strength) to the aqueous phase shifts the redox potentials of all-trans MK-7 only slightly. The formal redox potentials of all-trans MK-4 were determined in TMCL and nCL monolayers and found to be higher in nCL monolayers than in TMCL monolayers. The apparent electron transfer rate constants, transfer coefficients and activation energies of all-trans MK-4 in cardiolipins have been also determined. Most surprisingly, the apparent electron transfer rate constants of all-trans MK-4 exhibit an opposite pH dependence for TMCL and nCL films: the rate constants increase in TMCL films with increasing pH, but in nCL films they increase with decreasing pH. This study is a contribution to understand environmental effects on the redox properties of membrane bond redox systems.Graphical abstract

Ultrasensitive electrochemical determination of trace ceftizoxime using a thin film of Preyssler nanocapsules on pencil graphite electrode surface modified with reduced graphene oxide

An ultrasensitive electrochemical sensor for the selective voltammetric measurement of trace ceftizoxime (CFX) was described. Modification of a pencil graphite electrode (PGE) was first done with the reduced graphene oxide (r-GO) and, afterward, Preyssler nanocapsules (PNCs) were generated onto the r-GO/PGE. The surface morphology of the synthetic compounds has been evaluated using FT-IR, FE-SEM, TEM, and SEM techniques. Adsorptive differential pulse voltammetry (AdDPV), cyclic voltammetry (CV), chronocoulometry (CC) and electrochemical impedance spectroscopy (EIS) were employed to investigate the CFX electrochemical characteristic on the modified electrode (PNCs/r-GO/PGE). The electron transfer coefficient (α) between PNCs/r-GO and PGE was calculated using the obtained CV. Also, chronocoulometry experiments were performed in the absence and presence of CFX to calculate diffusion coefficient (D) and capacity of adsorption (ΓS) of CFX for PNCs/r-GO/PGE thin film. Under the optimized conditions, the calibration curve of the CFX has a linear concentration range from 1.0 × 10−11 to 3.0 × 10−8 M (R2 = 0.9993) and a detection limit of 1.8 pM. The developed electrochemical sensor shows greater sensitivity than the earlier reported techniques for the CFX measurement. The sensor was successfully utilized to determine the trace amounts of CFX in pharmaceutical and blood serum with suitable recoveries.

Mechanistic insights of the oxidation of bisphenol A at ultrasonication assisted polyaniline-Au nanoparticles composite for highly sensitive electrochemical sensor

In this work, a conducting polymer and nanometal composite electrocatalyst was prepared for the sensitive detection of bisphenol A (BPA) over a wide concentration window. Polyaniline (PANI) was first prepared from aniline through a chemical method, and gold nanoparticles (AuNPs) were embedded with the prepared PANI via ultrasonication to obtain the PANI_AuNPs electrocatalyst. The morphological, chemical, and electrochemical properties of the electrocatalyst were then determined, and BPA oxidation was investigated with the help of electroanalytical techniques to understand the electron-transfer process occurring at the PANI_AuNPs interface. The results showed that BPA was oxidized through a multistep electron-transfer process without any intermediate chemical step, and the rate-determining step was the second electron-transfer step. The oxidation proceeded as a 2e–/2H+ process with an electron-transfer coefficient of ≈0.69. These results indicate that the PANI and AuNPs work synergistically to promote the electron transfer from BPA. The quantitative analysis gave a broad linear range and a low limit of detection of 0.4 nM. The sensor was also tested for the detection of BPA in tap water, bottled water, and a canned beverage for real sample analysis.

Differential Pulse Voltammetric Determination of Paracetamol Using Activated Glassy Carbon Electrode

The electrochemical property of paracetamol was investigated at a glassy carbon electrode and activated glassy carbon electrode. Differential pulse voltammetry and cyclic voltammetry were used as diagnostic techniques in the determination of paracetamol. The activated glassy carbon electrode exhibited excellent electro-catalytic behaviour for the oxidation of PAR as evidenced by the enhancement of the oxidation peak current and the shift in the oxidation peak potential to less positive values by (13mv) in comparison with a bare GCE. In the present work the activated glassy carbon electrode was prepared by activating 200 s in a time base technique at a potential of 1750 mV. The electrode process of paracetamol was studied and some the experimental parameters which affect the response paracetamol, such as pH, effect of PAR concentration and scan rate on AGC electrode. The analysis of cyclic voltammogram gave fundamental electrochemical parameters including the electroactive surface coverage, the electron transfer coefficient and the heterogeneous rate constant (ks). The variation of scan rate study shows that the system undergoes adsorption controlled process. The equation of the calibration curve was found to be: Ip=0.429C + 6.43, R2=0.993. The LOD and LOQ for the developed method were determined to be 8×10-8 mol L-1 and 2.6×10-7mol L-1 respectively. Phosphate buffer pH 7.0 was selected for analytical purpose.

Polyaniline/reduced graphene oxide nanosheets on TiO2 nanotube arrays as a high-performance supercapacitor electrode: Understanding the origin of high rate capability

As charge storage occurs both on the surface and in the bulk of material, the dynamics of charge storage is a key issue in the practice of energy storage. Although the energy storage can be increased in the bulk of the material, it often suffers from a quite slow kinetics, which seriously hinders the rate capability. Keeping high surface-induced capacitive contribution is proposed to address this issue. Herein, a porous scaffold, TiO2 nanotube arrays grown in a Ti foil (TiO2 NTs/Ti) is selected as the current collector for electrodeposition of porous polyaniline/reduced graphene oxide (PANI/rGO) hybrid film. The capacitive contribution of PANI/rGO@TiO2/Ti is quantitatively evaluated, showing a high surface-induced capacitive contribution up to 58% at high rates (>25 mV s−1) and large electron transfer coefficient of 2. As a result, the electrode not only shows an ultrahigh specific capacity of 908 C g−1 at 1 mV s−1, but also delivers an outstanding rate capacity of 310 C g−1 at 500 mV s−1. PANI/rGO@TiO2/Ti also shows excellent cycling stability with 80% capacity retention after 10,000 cycles at a high current density of 25 A g−1.

A Simple Analytical Approach for Fitting Steady-State Polarization Behavior of Polymer Electrolyte Fuel Cells Using Tafel Slope Component Analysis (TSCA)

There is a need for methods with which to characterize the current-voltage (I-V) or polarization behavior of fuel cells with minimal computational resources. One candidate is the direct analytical approach.1 In our work, in contrast to most other approaches, we have used the potential (approximated by the voltage) as the governing variable to both characterize catalysts and ionomers with rotating disk electrode measurements2 and characterize the performance of fuel cell membrane-electrode assemblies.3-5 This approach allows us to use a single, multi-component equation to calculate the current density from the potential. The various components are based on (1) an intrinsic kinetic current density with a relatively low Tafel slope (TS), based on an electron transfer coefficient α, which is a variable, (2) a double TS current density, corresponding to α/2, (3) a quadrupled TS current density, corresponding to α/4, and (4) a limiting current density, with α = 0. Essentially, the equation takes the simple form of a summation of series resistances, where each term refers to a TS component. Each resistance is then converted to the reciprocal of a characteristic current density, similar to an exchange current density. The doubling can be due to a change in mechanism, the onset of pore-based mass transport, or to coupled ionic conduction. Quadrupling can occur when two of these operate in tandem. Only five parameters are needed to characterize the polarization behavior, the intrinsic α value, the characteristic current densities for α , α/2 and α/4, and the limiting current density.This approach has no intrinsic physical basis but can be used to compare various operating conditions and electrode compositions (Fig. 1). One application we have been interested in is the effectiveness of the catalyst.3,4 Another is determining the extent to which the polarization behavior is time-dependent. In ongoing work, we are (1) attempting to elucidate the intrinsic α values with specific mechanisms for the oxygen reduction reaction, (2) examining the relationship of hierarchical pore structures on TS quadrupling, and (3) developing a comprehensive database linking the fitted parameters with physically meaningful characteristics. Acknowledgements This project was partly supported by NEDO Japan through funds for the “Superlative, Stable and Sustainable Fuel Cells” project. References A. Kulikovsky, Electrochem. Commun., 11, 845-852 (2002).Miyatake, T. Omata, D. A. Tryk, H. Uchida, and M. Watanabe, J. Phys. Chem. C, 113, 7772-7778 (2009).Lee, M. Uchida, H. Yano, D. A. Tryk, H. Uchida and M. Watanabe, Electrochim. Acta, 55, 8504-8512 (2010).Lee, M. Uchida, D. A. Tryk, H. Uchida, and M. Watanabe, Electrochim. Acta, 56, 4783-4790 (2011).A. Tryk, M. Lee, M. Uchida, H. Uchida, and M. Watanabe, ECS Trans., 35, 13-23 (2011). Figure 1. Steady-state polarization behavior for MEAs with Pt/C catalyst layers with varying Nafion/carbon weight ratios: (left) log (Tafel) plots; (right) linear plots. Cell was operated at 65 °C with pure O2 feed (1 atm) at 100% RH (data from Ref. 3). Figure 1

Synthesis of gold nanoflakes decorated biomass-derived porous carbon and its application in electrochemical sensing of luteolin

Abstract The preparation and application of biomass-derived porous carbon (BPC) have aroused intensive attentions due to the advantages of eco-friendliness, abundant resources, and low cost. Herein banyan leaves derived BPC was prepared by calcination technique with rich three-dimensional interconnected frameworks. Furthermore, Au nanoflakes (AuNFs) were decorated on BPC by hydrothermal method to obtain AuNFs-BPC nanocomposite. The morphology, structure and composition of AuNFs-BPC were characterized by SEM, XRD, Raman and XPS techniques. AuNFs-BPC was modified on glassy carbon electrode to construct a functional sensing platform for the investigation on electrochemical behaviors of luteolin. Obvious enhanced electrochemical signals of luteolin could be observed, which was bigger than that on bare electrode. The electrode reaction mechanism was studied with the electron transfer coefficient and standard heterogeneous reaction rate constant calculated as 0.51 and 1.99 s−1. Consequently, an AuNFs-BPC modified electrode based voltammetric sensor for luteolin determination was constructed with a low detection limit of 0.07 μmol/L (3S0/S). This novel sensing platform displays great potential for practical and reliable determination of luteolin in Duyiwei capsules and human urine samples.

Bio-directed synthesis of platinum nanoparticles by Nymphaea alba extract: fabrication of a novel non-enzymatic hydrogen peroxide sensor

In this work, the extract of Nymphaea alba flowers was used as a reducing agent to synthesize platinum nanoparticles (Pt NPs), being such NPs characterized by different methods such as XRD, SEM and FT-IR. Crystal size of prepared Pt NPs was determined by SEM round circa 35 nm. Such characterized NPs were then applied to modify carbon paste electrodes (CPE/Pt NPs), which were electrochemically investigated by cyclic voltammetric method. The active surface area of CPE/Pt NPs was calculated about 0.027 cm2. Finally, the ability of this modified electrode was assessed to determine of hydrogen peroxide by amperometric technique. This modified electrode has shown a linear dynamic range of 1.5–250 μmol L−1 with detection limit of 0.7 μmol L−1. In addition, the electron transfer coefficient for hydrogen peroxide at the surface of CPE/Pt NPs was found to be 0.74. The simple preparation method, low costs (free enzyme), good stability, and efficient response are the advantages of this novel modified electrode as a sensor for determination of hydrogen peroxide.

The electrochemical behaviors and kinetics of AuNPs/N, S-GQDs composite electrode: A novel label-free amplified BPA aptasensor with extreme sensitivity and selectivity

A highly sensitive electrochemical sensor was developed for the determination of Bisphenol A (BPA) by immobilizing the aptamer on the glassy carbon electrode which was modified by nitrogen-sulfur-doped graphene quantum dots (N, S-GQDs) and Au nanoparticles. We mainly delved into the density of states of N, S-GQDs and the detection mechanism of sensor. On the basis of the improved detector, we focused on the research of kinetic parameters, such as the activation surface area (A), electron transfer coefficient (α), the standard rate constant (k), diffusion coefficient (D), and surface concentration (Г0). Under the optimal conditions, the DPV response of the sensor to BPA was a linear detection range from 0.1 to 10 μM and the detection limit was around 0.03 μM. It was noted that the developed sensor was excellently suitable for measuring BPA in tap water, and the recovery ranged from 82.6 to 107%.

Insights of temperature dependent catalysis and kinetics of electro-oxidation of nitrite ions on a glassy carbon electrode

Influence of temperature on the catalysis and kinetics of nitrite oxidation reactions has been investigated on a glassy carbon (GC) electrode surface in a slightly basic medium. To elucidate the kinetics of oxidation reaction, diffusion coefficient, electron transfer coefficient, heterogeneous rate constant and free energy of activation were systematically evaluated within the temperature range of 0–60 °C. Nitrite oxidation involves single electron transfer and first order reaction forming nitrogen dioxide as a product. The electrode process was found most efficient at 60 °C with a standard rate constant (ko) of 4.63 × 10−5 cm s−1 at 0. 0.84 V vs. Ag/AgCl (sat. KCl) reference electrode. Above 60 °C, predominant desorption step negatively influences the overall reaction rate. It has been proposed that at the lower temperatures (≤ 30 °C), the chemical step is concerned with an electron transfer step at the RDS and above this temperature, the reaction simply follows a stepwise mechanism. The decrease of solvent reorganization energy (λ) at higher temperatures minimizes the activation free energy (ΔG‡) which accelerates the reaction rate using catalytically different route.

Nanoscale zero-valent iron improved lactic acid degradation to produce methane through anaerobic digestion

Serious inhibition of methane production in an anaerobic digestion (AD) system can be caused by propionic acid, which is derived from lactic acid degradation. Nanoscale zero-valent iron (nZVI) was used in this study to improve conversion of propionic acid into acetic acid, thereby promoting methane production. The methane yield was markedly enhanced when nZVI concentration increased from 0 to 2 g/L; however, it decreased when nZVI concentration further increased to 8 g/L. At an nZVI concentration of 2 g/L, the methane yield increased by 37% from 398.5 to 546.4 mL CH4/g TVS. The abundance of Candidatus Cloacamonas in the bacterial community increased from 2.17% to 3.78%, which facilitated conversion of propionic acid into acetic acid. Meanwhile, the abundances of Methanomassiliicoccus and Methanosarcina in archaeal community increased, which was beneficial to methane production. Cyclic voltammetry showed that the electron transfer coefficient in the AD system increased from 0.029 to 0.034 s−1.

A rapid voltammetric strategy for determination of ferulic acid using electrochemical nanostructure tool in food samples

In this project, we performed an electrochemical investigation using a reduced graphene (rG) decorated CdO nanocomposite/1-methyl-3-octylimidazolium tetrafluoroborate ionic liquid (MOITF) carbon paste electrode (rG-CdO/MOITF/CPE) for determination of ferulic acid in food samples. In preparation of rG-CdO/MOITF/CPE, 6% w/w rG-CdO nanocomposite and 20% v/v room temperature ionic liquid were used to modify the bare CPE. SEM (Scanning Electron Microscopy) and XRD (X-Ray Diffraction) methods were applied to characterize the structure of the synthesized rG-CdO nanocomposite. At all the stages of this research, phosphate buffer solution (PBS) with the pH of 5.0, as an optimized pH condition, was used. The electron transfer coefficient (α) was obtained ⁓0.68 by recorded data from cyclic voltammogram of rG-CdO/MOITF/CPE in the presence of ferulic acid. In addition, using the chronoamperometric technique, the diffusion coefficient (D) of ferulic acid at rG-CdO/MOITF/CPE was calculated 5.4 × 10−5 cm2/s. Using the square wave voltammetry method, the linear dynamic range (LDR) was calculated to be from 0.02 to 400 μM, and the limitation of detection (LOD) was obtained as 8.0 nM. Eventually, the rG-CdO/MOITF/CPE was utilized to determine the amount of ferulic acid in food samples, and statistical calculations confirmed the sensitivity, selectivity, and precision of rG-CdO/MOITF/CPE, which is an electroanalytical tool.

Study of Organic Sulfide Oxidation on the Modified Graphite Electrodes by Co, Fe and Ni Nano Particles

Electro-oxidation of methyl phenyl sulfide with the aim of producing sulfoxide and sulfone was investigated over Ni, Co, Fe, and their alloys on graphite electrodes in the acetic acid as a non-toxic solvent. The modified electrodes were prepared by cyclic voltammetry technique. The surface morphology of electrodes was investigated by scanning electron microscopy and the presence of metal nanoparticles on the graphite was investigated by X-ray diffraction. The catalytic treatment and synergistic effects of the modified electrodes were studied by electrochemical techniques such as cyclic voltammetry (CV) and chronoamperometry (CA). It was found the performance of all the modified electrodes is successful. In the attendance of methyl phenyl sulfide, the graphite/CoFe modified electrode (G/CoFe) showed the highest performance for electro-oxidation also there was a linear relationship between the square root of the scan rate and anodic current in low scan rates, that indicates a diffusion controlled process. The diffusion coefficient, heterogeneous electron transfer rate constant and electron transfer coefficient were determined for methyl phenyl sulfide electrochemical oxidation. Electro-oxidation of methyl phenyl sulfide by electrolysis method was investigated and its results were studied by gas chromatograph (GC). Based on GC studies, the electro-oxidation of methyl phenyl sulfide by electrolysis produced methyl phenyl sulfoxide and methyl phenyl sulfone. Also, a mechanism for electro-oxidation of sulfide was proposed. The using of non-noble metals as the electrocatalyst for the first time for the organic sulfide electro-oxidation, the very easy, affordable and fast preparation of the modified electrode, high performance of the modified electrode, no need of using oxidant and co-catalyst and designing a homogeneous media with proper conductivity for oxidation of insoluble in water compounds demonstrate important items for the use of this procedure and electrode in the subsequent investigation of sulfides.