Values Of Charge Transfer Coefficient Research Articles

PEDOT wrapped biomimetic recognition system for selective determination of carcinogenic phenacetin content in drug samples

A molecular imprinted polymeric (MIP) recognition system comprising of PEDOT swaddled CoWO4 nanocapsules has been developed for the electrochemical detection of carcinogenic phenacetin drug. Facile hydrothermal route was employed to synthesize CoWO4 whereas, EDOT was wrapped around under chemical polymerization at room temperature. A series of characterizations revealed that electrostatic interactions generated between thiophene sulfur of PEDOT and metal atoms of CoWO4 have prompted the homogeneously wrapped molecularly imprinted nanocomposite. The obtained peak potential plotted against the CV scan rate revealed involvement of 2 electrons in the electroxidation detection process of phenacetin. The values of charge transfer coefficient α (0.69) and charge transfer rate constant ks (2.24 s−1) at electrode-electrolyte interface during the detection procedure were also evaluated. The nanoarchitecture of the designed MIP exhibited abundant imprinted sites to selectively bind the template molecule in terms of shape, size and functionalities resulted in significant augmentation in sensitivity (0.14 µA nM−1 cm−2) and a very low detection limit (0.091 nM). Phenacetin content in homeopathic and allopathic drug samples were successfully quantified with more than 95 % accuracy by employing the MIP modified electrode. The present research introduces new possibilities for identification of carcinogenic phenacetin used as adulterants in various narcotic drug samples.

Appraising the electrocatalytic performance of beta-cyclodextrin embellished supramolecular recognition system for pernicious food colorants

The current research presents the evaluation of supramolecular proficiency of the designed platform for electrocatalytic determination of pernicious food colorants, amaranth and fast green. The approach involving surface modification of glassy carbon electrode with beta cyclodextrin decorated strontium ferrite reduced graphene oxide nanocomposite (SFrGO-βCD) to ensure fast and reversible electro-oxidation of hydroxyl groups of the colorant molecules. The synergy between SF and rGO facilitated the sensor with enhanced surface area and conductivity through faradic redox reaction. Tremendous decrease in the obtained values of peak separation potential and impedance as manifested in CV and EIS analysis, enabled by electrostatic interactions between surface functionalities of rGO and βCD has resulted in the significant augmentation of sensitivity. The value of charge transfer coefficient, number of electrons involved, nature of electron transport process at electrode electrolyte interface during the analysis of electrochemical detection were explored through CV experiments. Food samples analysis (without spiking) utilizing screen printed electrode manifested the sensor as portable device for real time monitoring. Outstanding detection limit (0.022 nM for amaranth and 0.051 nM for fast green), excellent regenerability (Relative standard deviation less than 3%) and apparent recovery rate (above 90%) of the modified electrode presented a colossal potential for the development of sustainable and commercially competitive electrochemical sensor in food sector.

Indium electrowinning kinetics on titanium, aluminum and copper supports from sulfate solution

Abstract Indium electrowinning process from sulfate solution on copper, titanium and aluminum cathodes (Cu, Ti and Al) were studied using the methods of cyclic voltammetry (CV) and chronoamperometry (CA). Voltammogram features indicated the irreversible behavior of indium discharge on each cathode. The heterogeneous charge transfer rate constant (k0) has been evaluated on Cu, Ti and Al cathodes and their values were 7.1·10−5 cm/s, 6.2·10−5 cm/s and 5.4·10−5 cm/s, respectively. The indium ions electro-reduction seems to be quite different on these diverse cathodic supports: a nucleation process appears on Cu and Al cathodes, while is absent on Ti cathode due to the hydrogen evolution overlapping at high cathodic overpotentials. CV and CA techniques allowed to calculate the diffusion coefficient (D0) of indium ion in sulfate solution. Furthermore, calculating the roughness coefficient (φ) by CV technique on each metal surface, it was possible to establish the real surface area of Cu, Ti and Al cathodic supports. The charge transfer coefficient values (α) calculated by Tafel curves agreed those obtained by CV results, while the k0 value and the exchange current density (i0) showed a similar trend for each cathode. By these results, the exchange current density was equal to 1.20 mA/cm2, 0.30 mA/cm2 and 0.075 mA/cm2 for Cu cathode Ti and Al cathodes, respectively. The findings of this investigation can provide an understanding of the indium electrowinning process on three different support electrodes (Cu, Ti and Al) from sulfate solution.

Development, validation and enzyme kinetic evaluation of multi walled carbon nano tubes mediated tyrosinase based electrochemical biosensing platform for the voltammetric monitoring of epinephrine

Epinephrine (EP) is one of the key neurotransmitter, which plays a vital role in the central nervous system. Current research report designates the development of biosensor based on the modification of glassy carbon electrode (GCE) with multi walled carbon nano tubes (MWCNTs) followed by drop casting of Tyrosinase (Ty) enzyme (Ty/MWCNTs/GCE) towards the sensitive monitoring of EP. The electrochemical behavior of EP at Ty/MWCNTs/GCE biosensor was examined and the redox mechanism was proposed. The developed Ty/MWCNTs/GCE was characterized by electrochemical techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and tafel plot studies. The influence of pH of phosphate buffer solution (PBS) on the electrochemical redox behavior of EP was observed and pH-7.0 was identified as optimal pH value. The electrochemical kinetic parameters such as heterogeneous rate constant, diffusion coefficient and charge transfer coefficient values were evaluated. The limit of detection and limit of quantification values were evaluated. The low apparent Michaelis – Menten constant (Kmapp) was determined as 0.159 mM, demonstrating the immense catalytic activity of Ty enzyme. Repeatable, reproducible and stable nature of the fabricated Ty/MWCNTs/GCE was successfully examined. Finally, the developed biosensor was tested for the practical application in quantification of EP in human serum samples.

Electrochemical characteristics of (PEM) electrolyzer under influence of charge transfer coefficient

In this paper a systematic understanding of how charge transfer coefficient (CTC) and exchange current density contributes to polarization and performance characteristics of PEM electrolyzer has been investigated. A detail discussion on the role played by charge transfer coefficient in influencing operating characteristics of PEM electrolyzer has been presented in this article. Experimental data was used to validate the accuracy of the finding of this research. Main interesting insights are that at CTC of 0.5 and 0.2 for anode and cathode respectively, the operating voltage at 1 A/cm2 (current density) is around 2.0 V, however at CTC of 2 and 0.5 for anode and cathode respectively, there was significant drop in operating voltage up to 1.62 V with current density of 1 A/cm2, this accounts for about 27% reduction in operating voltage. It was also discovered that with exchange current density of 1 × 10–7 for a Pt–Ir anode based electrode the CTC value for anode increase from 0.27 to 0.34 at current density of 0.05 A/cm2 to 2 A/cm2 respectively, whereas for Pt cathode catalyst with exchange current density of 1.8 × 10–3 the CTC values for cathode increased from 0.02 to 0.14 at current density of 0.1 A/cm2 to 2 A/cm2 respectively, these findings were in agreement with the CTC values reported in the literature.

Investigation of the effect of charge transfer coefficient (CTC) on the operating voltage of polymer electrolyte membrane (PEM) electrolyzer

Activation overpotential is a very important parameter in evaluating the performance of PEM electrolyzer, it is one of the major overpotentials that contribute towards overall operating voltage of the electrolyzer. One of the most significant parameters associated with this overvoltage is charge transfer coefficient (CTC). This study aims to contribute to this growing area of research by investigating the effects of operating temperature and CTC on the overall operating voltage. This study also provides an important opportunity to advance the understanding of the effect of different temperature and pressure on the CTC. The result of this study was successfully compared with experimental data. The simulation result shows that, within the temperature range of 10 °C–90 °C, the CTC values at the anode electrode ranges between 0.807 and 1.035 while at the cathode electrode, the variation is only within 0.202–0.259. It was observed that activation overvoltage decreases when the CTC increase from 0.1 to 2.0 both at anode and cathode electrodes. Interestingly it was observed that the CTC remains the same even at balanced and unbalanced pressure.

Development, Characterization and Application of a Carbon‐Based Nanomaterial Composite as an Electrochemical Sensor for Monitoring Natural Antioxidant (Gallic Acid) in Beverages

AbstractGallic acid (GA) is an important organic acid, found in many natural plants and in food beverages. Here in, we have developed a chemical sensor for the monitoring of GA in wine, green tea and fruit juices. The oxidation of GA was found to be an irreversible process and the corresponding mechanism was proposed. The effect of pH on the oxidation behavior was studied and pH‐6.0 was selected as an optimum pH. Based on the scan rate results a linear relation was observed between the square root of scan rate and peak currents for GA, confirming the oxidation of GA as a diffusion controlled process. The kinetic parameters such as diffusion coefficient, heterogeneous rate constant and charge transfer coefficient values were determined. The limit of detection (LOD) and quantification (LOQ) values were calculated as 4.39 × 10‐7 M and 1.46 × 10‐6 M. The repeatability, reproducibility and stability of the developed sensor were examined and the results confirmed that the developed sensor was in superior in condition. Finally, the practical application of the developed sensor was scrutinized for the quantitative estimation of GA in wine, green tea and fruit juices.

Electrochemical detection of rutin on nitrogen-doped graphene modified carbon ionic liquid electrode

In this paper nitrogen-doped graphene (NG) was synthesized and applied to modify an ionic liquid 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE). The fabricated NG/CILE exhibited excellent electrochemical performances. Electrochemical behaviors of rutin on NG/CILE were carefully investigated with a pair of well-defined redox peaks appeared, which was attributed to the presence of NG with electrocatalytic activity. Electrochemical parameters of rutin on NG/CILE were calculated with the values of charge transfer coefficient (α), electron transfer number (n) and electrode reaction standard rate constant (ks) as 0.57, 1.76 and 1.24s−1, respectively. Under the optimal conditions rutin could be detected in the concentration range from 7.0×10−10 to 1.0×10−5mol/L with the detection limit as 0.23nmol/L (3σ) by differential pulse voltammetry. The proposed method was further applied to the determination of rutin tablet samples with satisfactory results.

Constant-Charge Reaction Theory for Potential-Dependent Reaction Kinetics at the Solid–Liquid Interface

To understand the potential-dependent kinetics of reactions at the solid–liquid interface, we derive a constant-charge reaction theory for understanding the coupled charge transfer during the chemical bond making/breaking. The charge transfer coefficient (CTC) for reactions at the solid–liquid interface is shown to be linearly proportional to the electrochemical potential change from the initial state to the transition state as well the interface differential capacitance at the constant-charge model, and can be further related to the net dipole change normal to the surface during the reaction. Using the constant-charge theory, the CTC can be explicitly calculated on the basis of the first principles calculations without the need to assume the redox behavior of the elementary reactions and thus provide a unique possibility to evaluate and compare the magnitude of CTC for different reactions across different surfaces. By examining a series of interface reactions and comparing the calculated CTC values, we p...

Electrochemical characterization of the encapsulated polyoxometalates (POMs) into the zeolite

The electrochemical characterization of polyoxometalates encapsulated into the zeolite (POM@Z) is presented for the first time. A stable film comprising POM@Z and graphite powder was prepared on glassy carbon electrode (POM@Z-GCE) by dip-coating. The cyclic voltammograms of the modified electrode showed three well-defined pairs of redox peaks due to the redox reaction of the encapsulated POMs. The values of charge transfer coefficient (α) and the heterogeneous charge transfer rate constant (kapp) for three pairs of redox peaks were evaluated. The electrochemical studies revealed that the encapsulated POMs show very slower electrochemical responses than those of un-encapsulated POMs arising from the restraint in the zeolite pores towards diffusion of charge-balancing electrolytes. According to the obtained evidences an intra-zeolite charge transfer mechanism for the encapsulated POMs can be concluded. The POM@Z-GCE showed the advantages of excellent electrocatalytic activity towards reduction of H2O2.

Electrochemical behavior and electrowinning of palladium in nitric acid media

In this study, the electrochemical behavior of Pd(II) in nitric acid media was investigated using various electrochemical techniques. By analyzing the cyclic voltammogram of Pd(II) recorded at Pt electrode, a series of electrochemical reactions associated with palladium were recognized, indicating that Pd(II) undergoes a single step two-electrons irreversible process. Electroreduction reaction of Pd(II) and auto-catalytic reactions of nitrous acid are supposed to play a leading role in low and high concentrations of nitric acid, respectively. Stirring could facilitate the reduction of Pd(II) in relatively low nitric acid concentration (⩽ 3 mol/L). The value of charge transfer coefficient was determined to be 0.18 for the measurements at 298 K. The diffusion coefficient of Pd(II) increased from 1.89 × 10−8 cm2/s at 288 K to 4.23 × 10−8 cm2/s at 318 K, and the activation energy was calculated to be 21.5 kJ/mol. In electrowinning experiments, SEM images of palladium obtained by electrolysis reveal the dendrite growth in all cases, which is uniform all over the entire surface of Pt electrode. The recovery ratios of Pd at different nitric acid concentrations are high, and the faradic efficiency of electrolysis decreases with increasing the nitric acid concentration. When stirring was introduced during electrolysis, the electrodeposition rate of Pd increased substantially.