Electron Transfer Coefficient Research Articles

Effect of operating temperature on ammonia decomposition behavior and cell performance of direct ammonia solid oxide fuel cells

Direct ammonia solid oxide fuel cells (DA-SOFC) are regarded as a promising power generation technology. Nevertheless, the catalytic reaction of ammonia on the anode surface significantly affects DA-SOFC performance. This study explores the deterioration of DA-SOFC performance in the 550–700 °C and the interaction between NH3 decomposition and electrochemical reactions. The findings indicate that, at 550 °C, compared to H2, the reduction in power density of NH3 18.58% exceeds 4.56%t of NH3 d.s.g. (mixtures, 0.75H2 + 0.25N2). The anodic polarization impedance of NH3 exceeds that of H2 and NH3 d.s.g. by 51.1% and 28.9%, respectively. Cathode utilizing O2 has a dual impact on NH3 decomposition, at lower temperatures, oxidizing the anode's active site, decreasing NH3 decomposition rate, resulting in insufficient H2 supply, reducing electron transfer coefficient. Conversely, at higher temperatures, O2 promotes NH3 decomposition by boosting H2 consumption. However, more N2 is produced, increasing the concentration loss.

Voltammetric and electro-kinetic assessment of prucalopride at MnO2-rGO fabricated pencil graphite electrode

Development and design of rGO-based nanocomposite-modified carbon-based electrodes are necessary to enhance the selectivity and desired selectivity of the voltammetric sensors. In this work, a manganese dioxide-reduced graphene oxide (MnO2-rGO) fabricated pencil graphite electrode is described for the detection of prucalopride (PRU), which is used to treat chronic idiopathic constipation. A simple cost effective hydrothermal method was used to synthesize the needle-shaped MnO2. The MnO2-rGO nanocomposite was characterized using XRD, SEM, and FTIR spectroscopy to examine its microstructure and morphology. The results revealed that MnO2 needles are distributed on the flakes of the rGO, thereby enhancing the electro-catalytic activity of MnO2-rGO/PGE. The electrochemical performance of the developed MnO2-rGO/PGE was examined using CV, chronocoulometry, SWSV, and DPSV methods. The diffusion-controlled oxidation of the PRU at the MnO2-rGO/PGE produces an irreversible peak in all the voltammograms which were used to calculate several electro-kinetic parameters like electron transfer coefficient (α = 0.598), diffusion coefficient (Do = 1.62 × 10−5 cm2s−1), surface coverage (Γo = 1.55 × 10−9 molcm−2), and effective surface area. Furthermore, advanced SWSV and DPSV methods are proposed for the accurate, selective, and sensitive detection of the PRU in pharmaceutical samples. The reported values of detection limit (LOD) for the proposed SWSV and DPSV methods are 20.39 μM and 14.53 μM, respectively, which make them eco-friendly and affordable alternative tools for the quantification of the PRU in pharmaceutical samples.

Fe-doped WO3-Modified sensor for the improved electrochemical detection of curcumin

In this study, an iron-doped tungsten oxide (Fe-WO3) nanomaterialwas synthesizedand utilized to modify carbon paste electrodes for the identification of the bioactive ingredient curcumin (CUM). Turmeric contains a bioactive compound called curcumin, which is yellow and has various potential biological applications, such as being an anti-carcinogenic, anti-inflammatory, and antioxidant agent. The Fe-WO3 nanomaterial underwent characterization through SEM, XRD, and EDS techniques. The electrochemical performance of CUM was inquired using square wave and cyclic voltammetry methods. During catalytic oxidation, the Fe-WO3 working electrode assembly showed faster electron transport than the bare CPE. Investigations havebeen conductedinto the kinetics of oxidation, and the developed sensor demonstrated an excellent linear detection range (5 μM to 60 μM), a decreased limit of detection (6.2 × 10−8 M), and a limit of quantification under optimal conditions (20.7 × 10−8 M).The numbers of electrons transmitted, the heterogeneous rate constant, the electron transfer coefficient, and the electrochemical oxidation were all measured. The results from the examination of CUM in actual samples using the devised Fe-doped WO3 modified electrode were good. Additionally, it showed a considerable increase in the curcumin peak current concerning responsively, specificity, and reliability for curcumin analysis.

Calcined Nickel Oxide Nanostructures at Different Temperatures Onto Graphite for Efficient Electro‐Oxidation of Ethylene Glycol in Basic Electrolyte

ABSTRACTFabricating a highly active and stable nanocatalyst material displays a great concern when constructing a commercially viable ethylene glycol (EG) fuel cell. Herein, nickel oxide nanostructures were grown onto graphite (NO/T) using coprecipitation and calcination protocol at different temperatures. Techniques for XRD, TEM, SEM, and EDX investigations were used to look into the produced crystal planes, shape, and elemental mapping of synthesized nickel oxide nanoparticles. Different NO/T nanocatalyst electroactivities were examined in order to oxidize EG molecules in basic electrolyte. The surface area values of calcined nanostructures at 200°C and 300°C were much higher than those measured at NO/T‐400 by 7.62 and 3.71 folds to explain their outstanding performance. Some kinetic information for varied NO/T nanocatalysts was derived including the electron transfer coefficient, rate constant, and surface coverage values. Electron transfer rate constants of 0.1946, 0.3734, 0.0113, and 0.0303 s−1 were calculated at NO/T‐200, NO/T‐300, NO/T‐400, and NO/T‐500, respectively. Increased oxidation current densities could be achieved when NO/T nanomaterials were subjected to lowered calcination temperatures. NO/T‐200 and NO/T‐300 nanocatalysts also displayed decreased Eonset for alcohol oxidation process by 20 and 41 mV in relation to that at NO/T‐400. Moreover, chronoamperometric experiments revealed the prevalence of the stable behavior during EG oxidation at these nanostructures, especially for calcined ones at 200°C and 300°C. Much reduced poisoning rates were measured at NO/T‐200 (0.171 s−1) and NO/T‐300 (0.067 s−1) when contrasted to that at NO/T‐500 (0.727 s−1). Increasing the alcohol and supporting electrolyte concentrations was beneficial in improving the charge transfer characteristics of NO/T nanocatalysts as demonstrated by EIS measurements. This study supports the promising activity of NiO nanoparticles onto graphite as anode materials for direct alcohol fuel cells.

Is the Interfacial Electrochemical Behavior of Quercetin the Same as That of Catechol Plus Resorcinol?

Background: Electrodeposition of functional films from polyphenol-containing solutions has emerged as a new field of surface functionalization from bio-sourced molecules. There is, however, almost no knowledge about the chemical structure of such complex films. It is the aim of this research to use the known electrodeposition of films made from catechol and resorcinol, two isomers of dihydroxybenzene, to understand the electrodeposition of a more complex polyphenol, quercetin, which is constituted from a fused catechol and resorcinol moiety. The aim of this article is hence to introduce some methodology in the interpretation of the electrochemical behavior of complex polyphenols starting from their building blocks. Methods: Cyclic voltammetry (CV) is used to deposit films from quercetin and from equimolar blends of catechol and resorcinol on amorphous carbon and gold working electrodes. The main experimental parameter was the potential sweep rate used during the CVs. Results: The CV of quercetin is not the exact sum of the CV of the catechol + resorcinol blends, but the major features are conserved, namely the presence of two main oxidation peaks affiliated to those of catechol and resorcinol but shifted to less anodic potentials. In addition, the anodic electron transfer coefficients of the two oxidation waves of quercetin are higher than those measured in the catechol resorcinol blend. However, film deposition ability is reduced with quercetin compared to catechol + resorcinol blend in probable relationship to steric hindrance occurring during the non-electrochemical crosslinking of the deposit. The quercetin-based films deposited at 10 mV·s−1 on gold electrodes are conformal and display some antioxidant activity.

NiCo layered double hydroxide nanosheet arrays constructed via in-situ plasma etching as non-enzymatic electrochemical sensor for glucose in food

The design and construction of an efficient non-enzymatic glucose electrochemical sensor is of great significance for food quality assessment. Here, we have developed a method to fabricate highly efficient catalytic electrodes for glucose sensing in alkaline. This method utilizes microplasma assistance during the in-situ etching of NiCo layered double hydroxide nanosheet arrays on nickel foam (NiCo-LDH/NF). The NiCo-LDH nanosheets possessed uniform dispersion without agglomeration, high electrochemically active surface area, and excellent electron transfer efficiency (the electron transfer coefficient (α) up to 0.91, the catalytic rate constant (k) was 2.44 × 106 cm3 mol−1 s−1). The NiCo-LDH/NF-based non-enzymatic glucose sensor exhibits the broad linear range (0.4–150 μM), high sensitivity (98000 μA mM−1 cm−2), and the low detection limits (48.76 nM) with satisfactory reproducibility and selectivity. This work developed a simple and rapid in-situ approach for constructing non-enzymatic electrochemical sensors with high sensitivity.

Metal-polymer-clay nanocomposites based electrochemical sensor for detecting hydrazine in water sources

AgNPs embedded polymer-clay (AgNPs@PEI-HNT) nanocomposites were successfully employed to sensitively detect hydrazine in water samples using differential pulse voltammetry (DPV) and amperometry methods. In-situ polymerization was utilized for assembling the polymer-clay composites, which were subsequently coated with AgNPs. PEI improves conductivity and absorbs AgNPs on the surface of HNTs, as evidenced with the help of UV-Visible, IR spectroscopy, XRD, XPS and morphological studies (FE-SEM and TEM). Nanocomposites were coated with GCE, which improved their electrocatalytic performance during hydrazine oxidation. The Tafel plot, Galus and Cottrell equations were used to compute the electron transfer coefficient (0.64), catalytic reaction rate constant (4.81 × 104 M−1s−1) and diffusion coefficient (2.56 × 10−5 cm2/s) of hydrazine at AgNPs@PEI-HNT/GCE. Amperometry technique was used to determine the LOD along with sensitivity of hydrazine, which were 0.22 nm and 116.76 µA µM−1 cm−2. Modified electrode offers enhanced properties for example strong anti-interference capability, good reproducibility, long-term stability, sensitivity, and so on. The designed sensor successfully detects hydrazine in water samples with high recovery rates (R.S.D. < 5 %).

Boosting conversion of waste activated sludge to methane during anaerobic digestion via facilitating direct interspecies electron transfer with glycerol

Possibility of boosting conversion of waste activated sludge to methane via facilitating direct interspecies electron transfer with glycerol was explored. Methane yields with 5 %/8 % glycerol were 1.18/1.31 folds higher than that without glycerol. After removing methane yields from glycerol, methane yields with 5 %/8 % glycerol was still 17 %/19 % higher than that without glycerol. Electron transfer coefficients for charge/discharge in sludge with 8 % glycerol were 1.12/1.39 folds higher than that without glycerol. Analysis of conductivity-temperature responses found that conductivity of sludge with 8 % glycerol exhibited an exponential increase when temperature was declined, similar to that with 8 % ethanol. However, conductivity of sludge with 8 % glycerol was one order of magnitude higher than that with 8 % ethanol. Electrochemical Fourier transform infrared spectra showed that reversible changes of bands associated with c-type cytochrome in sludge with 8 % glycerol were more intense than that with 8 % ethanol. Analysis of microbial communities showed that glycerol feeding increased the abundance of Methanospirillum hungatei JF-1, and specially enriched Tangfeifania diversioriginum, Syntrophomonas zehnderi OL-4 and Trichococcus pasteurii. These results indicated that glycerol feeding facilitated the better direct interspecies electron transfer than ethanol feeding that had been previously documented during anaerobic digestion of waste activated sludge.

Ferulic acid detection in honey using carbon paste electrode modified by C-C3N4/Li2CoMn3O8 nanocomposite

Honey is regarded as a valuable food commodity which has many and varied components, including phenolic compounds. Ferulic acid (FA) is one of these compounds, which possesses activities such as antioxidant, anti-inflammatory, anti-diabetic, haemolytic, antiviral, anti-cancer, etc. In view of these unique characteristics, a quick, sensitive, simple and inexpensive method for FA identification is required. This research developed a novel electrochemical sensor for measuring FA in honey samples. The sensor utilizes a C-C3N4/Li2CoMn3O8 nanocomposite modified carbon paste electrode (C-C3N4/LCMO/CPE) to enhance the sensitivity and detection. The synthesized nanocomposite exhibits remarkable properties, featuring an abundance of electrochemically active sites and enhanced electron transfer rates, making it ideal for developing advanced electrochemical sensors. The XRD, SEM and EDX analysis were used to examine and look like the synthesised nanocomposite structure. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods were used to evaluate the electrochemical behavior of C-C3N4/LCMO/CPE sensor for FA detection and optimized by adjusting pH, and potential scan rate. FA was measured in a phosphate buffered saline (PBS; 0.1 M, pH 4.0) by DPV with the detection limit of 3.6 nM and quantitative limit of 0.009 µM in the linear response ranges of 0.009–3.000 and 5.00–100 µM. Chronoamperometry was utilized to calculate the diffusion coefficient of FA (D = 3.45 (±0.11) × 10−6 cm2.s−1) on the surface of the C-C3N4/LCMO/CPE, as well as the electron transfer coefficient (α = 0.68). The sensor’s high sensitivity for accurately assessing FA in real samples was demonstrated by recovery values ranging from 96.96 to 102.36 %.

Synthesis of nanoflakes-covered microparticles of nickel-Application for electrocatalytic oxidation and quantitation of nitrofurazone

Nickel microparticles covered with nanoflakes (NMCN) were hydrothermally synthesized in an alkaline solution of acrylamide dissolved in ethylene glycol/ethylenediamine at 200 °C. Structure and morphology of NMCN were characterized by field-emission scanning electron microscopy and X-ray powder diffraction, respectively. NMCN was applied, as an electrode modifier, with a surface concentration of 5.1 × 10−8 mol cm−2, and a detailed study was performed for the kinetics of charge transfer across the modified electrode/electrolyte interface using cyclic voltammetry. For the redox transition of NMCN in an alkaline solution, electron transfer coefficient and apparent charge-transfer rate constant were acquired as 0.65 and 0.6 s−1, respectively. The modified electrode was then applied for a study on the electrocatalytic oxidation of nitrofurazone (NF) on the NMCN surface through an electrochemical-catalytic (EC') mechanism. The oxidation process was followed by a NF diffusion coefficient of 2.9 × 10−6 cm2 s−1 and a catalytic rate constant of 3.0 × 104 cm3 mol−1 s−1. Also, an electron transfer coefficient of 0.40 was attained. The modified electrode was employed as a novel, time-saving, sensitive and simple amperometric sensor for NF, and quantified the drug with a linear range of 30–570 μmol L−1 and a sensitivity of 0.694 ± 0.002 A L mol−1 cm−2. Also, a detection limit of 4.3 μmol L−1 was attained. The sensor was employed for direct assay of NF in the human serum and ointments.

Voltammetric Sensing of Chloride Based on a Redox-Active Complex: A Terpyridine-Co(II)-Dipyrromethene Functionalized Anion Receptor Deposited on a Gold Electrode.

A redox-active complex containing Co(II) connected to a terpyridine (TPY) and dipyrromethene functionalized anion receptor (DPM-AR) was created on a gold electrode surface. This host-guest supramolecular system based on a redox-active layer was used for voltammetric detection of chloride anions in aqueous solutions. The sensing mechanism was based on the changes in the redox activity of the complex observed upon binding of the anion to the receptor. The electron transfer coefficient (α) and electron transfer rate constant (k0) for the modified gold electrodes were calculated based on Cyclic Voltammetry (CV) experiments results. On the other hand, the sensing abilities were examined using Square Wave Voltammetry (SWV). More importantly, the anion receptor was selective to chloride, resulting in the highest change in Co(II) current intensity and allowing to distinguish chloride, sulfate and bromide. The proposed system displayed the highest sensitivity to Cl- with a limit of detection of 0.50 fM. The order of selectivity was: Cl- > SO42- > Br-, which was confirmed by the binding constants (K) and reaction coupling efficiencies (RCE).

Parameter estimations from SARS-CoV-2 electrochemical interactions

Electrochemical pathogen sensing has gathered limelight for its effective and ultrafast detection capabilities. More recently, several electrochemical sensors were developed to counter the increasing testing requirement for the 2019 coronavirus disease (COVID-19) diagnosis. One such sensor developed was the Ultrafast COVID-19 (UFC-19) diagnostic sensor which could detect the SARS-CoV-2 spike protein in saliva samples. Although UFC-19 was established in literature to sense SARS-CoV-2 in saliva samples, the factors causing such an interaction or parameters to model such an interaction are yet to be studied in detail. In this work, an attempt has been made to electrochemically characterize the interactions at the interface by employing cyclic and linear sweep voltammetry on a rotating disk electrode setup. As a result, electrochemical parameters were calculated using chemical and electrochemical principles. The electrochemical surface area, electrode surface coverage, diffusion coefficient, reaction order with respect to SARS-CoV-2 whole virus, electron transfer coefficient have been estimated providing additional insights into the events occurring at the electrical double layer. The reaction order for the interaction was reckoned to be 0.7 confirming a non-elementary, multi-step process occurring at the interface. Theoretical and experimental calculations confirm higher hydroxide ion accumulation at the interface in the presence of SARS-CoV-2 whole virus. Results from this work lay the foundation for developing models for electrochemical SARS-CoV-2 interaction and possible extension toward other pathogenic viruses.

Electrochemical Reduction of Perfluorooctanoic Acid (PFOA): An Experimental and Theoretical Approach.

Perfluorooctanoic acid (PFOA) is an artificial chemical of global concern due to its high environmental persistence and potential human health risk. Electrochemical methods are promising technologies for water treatment because they are efficient, cheap, and scalable. The electrochemical reduction of PFOA is one of the current methodologies. This process leads to defluorination of the carbon chain to hydrogenated products. Here, we describe a mechanistic study of the electrochemical reduction of PFOA in gold electrodes. By using linear sweep voltammetry (LSV), an E0' of -1.80 V vs Ag/AgCl was estimated. Using a scan rate diagnosis, we determined an electron-transfer coefficient (αexp) of 0.37, corresponding to a concerted mechanism. The strong adsorption of PFOA into the gold surface is confirmed by the Langmuir-like isotherm in the absence (KA = 1.89 × 1012 cm3 mol-1) and presence of a negative potential (KA = 3.94 × 107 cm3 mol-1, at -1.40 V vs Ag/AgCl). Based on Marcus-Hush's theory, calculations show a solvent reorganization energy (λ0) of 0.9 eV, suggesting a large electrostatic repulsion between the perfluorinated chain and water. The estimated free energy of the transition state of the electron transfer (ΔG‡ = 2.42 eV) suggests that it is thermodynamically the reaction-limiting step. 19F - 1H NMR, UV-vis, and mass spectrometry studies confirm the displacement of fluorine atoms by hydrogen. Density functional theory (DFT) calculations also support the concerted mechanism for the reductive defluorination of PFOA, in agreement with the experimental values.

Silver Nanoparticle-Embedded Hydrogels for Electrochemical Sensing of Sulfamethoxazole Residues in Meat.

A disposable electrochemical sensor based on silver nanoparticle-embedded cellulose hydrogel composites was developed for sensitive detection of sulfamethoxazole residues in meat samples. Scanning electron microscopy confirmed the porous structure of the cellulose matrix anchored with 20-50 nm silver nanoparticles (AgNPs). Fourier transform infrared spectroscopy and X-ray diffraction verified that the metallic AgNPs coordinated with the amorphous cellulose chains. At an optimum 0.5% loading, the nanocomposite sensor showed a peak-to-peak separation of 150 mV, diffusion-controlled charge transfer kinetics, and an electron transfer coefficient of 0.6 using a ferro/ferricyanide redox probe. Square-wave voltammetry was applied for sensing sulfamethoxazole based on its two-electron oxidation peak at 0.72 V vs. Ag/AgCl in Britton-Robinson buffer of pH 7.0. A linear detection range of 0.1-100 μM sulfamethoxazole was obtained with a sensitivity of 0.752 μA/μM and limit of detection of 0.04 μM. Successful recovery between 86 and 92% and less than 6% RSD was achieved from spiked meat samples. The key benefits of the proposed disposable sensor include facile fabrication, an antifouling surface, and a reliable quantification ability, meeting regulatory limits. This research demonstrates the potential of novel cellulose-silver nanocomposite materials towards developing rapid, low-cost electroanalytical devices for decentralized on-site screening of veterinary drug residues to ensure food safety.

Electrochemical Aptasensing Platform for the Detection of Retinol Binding Protein-4.

Here, we present the results of our the electrochemical aptasensing strategy for retinol binding protein-4 (RBP-4) detection based on a thiolated aptamer against RBP-4 and 6-mercaptohexanol (MCH) directly immobilized on a gold electrode surface. The most important parameters affecting the magnitude of the analytical signal generated were optimized: (i) the presence of magnesium ions in the immobilization and measurement buffer, (ii) the concentration of aptamer in the immobilization solution and (iii) its folding procedure. In this work, a systematic assessment of the electrochemical parameters related to the optimization of the sensing layer of the aptasensor was carried out (electron transfer coefficients (α), electron transfer rate constants (k0) and surface coverage of the thiolated aptamer probe (ΓApt)). Then, under the optimized conditions, the analytical response towards RBP-4 protein, in the presence of an Fe(CN)63-/4- redox couple in the supporting solution was assessed. The proposed electrochemical strategy allowed for RBP-4 detection in the concentration range between 100 and 1000 ng/mL with a limit of detection equal to 44 ng/mL based on electrochemical impedance spectroscopy (EIS). The specificity studies against other diabetes biomarkers, including vaspin and adiponectin, proved the selectivity of the proposed platform. These preliminary results will be used in the next step to miniaturize and test the sensor in real samples.

Revisiting the Butler-Volmer Electrode Kinetics: Separating the Anodic and Cathodic Current Components of a Quasi-Reversible Electrode Reaction in Staircase Voltammetry

A simple mathematical strategy is proposed to estimate anodic and cathodic current components in voltammetry by combining the basic mathematical model of a quasi-reversible electrode reaction at a conventional planar electrode with the Butler-Volmer electrode kinetics with a goal to simplify and facilitate the measurement of electrode kinetics. In spite of the fact that the separate anodic and cathodic current components are experimentally inaccessible parameters, it is demonstrated for the first time that they can be reliably estimated from the net (total) current over the whole potential interval of a common voltammetry, requiring only the current–potential relationship, without prior knowledge of any electrode kinetic parameter (i.e., the standard rate constant and the electron transfer coefficient). The mathematical procedure requires semi-integration of the current and previous knowledge of the formal potential of the studied redox couple. The theory predicts that very fast electrode processes, with an apparent electrochemical reversible behavior, are associated with anodic and cathodic current components the intensity of which is proportional to the standard rate constant. Thus, the proposed simple methodology provides a new perspective in analyzing voltammetric data and expands the accessible kinetic interval towards very fast electron transfer processes by means of simple voltammetry at macroscopic planar electrodes. The proposed methodology is experimentally illustrated with the electrode reaction of hexacyanoferrate(II) ion oxidation at platinum electrode.

Quantitative characterization of the contribution of electrogenerated active species for NH+ 4-N oxidation on Ti/RuO2-IrO2 anode

The contribution of active species for ammonia nitrogen (NH4+-N) oxidation has received much attention in recent decades through electrocatalytic oxidation (EO) technology. Here we describe the strong NH4+-N removal capacity (more than 98 %) with NaCl as electrolyte of Ti/RuO2-IrO2 anode. Electrochemical tests were used to characterize the excellent NH4+-N degradation performance of Ti/RuO2-IrO2 anode in presence of chlorides. The values of electron transfer number (n = 1.02) and transfer coefficient (α = 0.42) show that the reaction is in the diffusion control stage, which is more conducive to the degradation of NH4+-N. Additionally, three active species (•OH, Cl•, and ClO•) formation is related to the adsorption energy (obtained by density functional theory (DFT) calculation) during the electrolysis process. The difference charge density and density of state (DOS) calculation indicate that the O − in ClO• is more likely to break and react with pollutants in water, which is consistent with the results of active species detection experiments. The combination of kinetics (Tafel) and thermodynamics (adsorption energy) shows that the variation of Tafel slope is affected by the coverage of active species on the electrode surface.

An on-site and portable electrochemical sensing platform based on spinel zinc ferrite nanoparticles for the quality control of paracetamol in pharmaceutical samples.

In this study, crystalline spinel zinc ferrite nanoparticles (ZnFe2O4 NPs) were successfully prepared and proposed as a high-performance electrode material for the construction of an electrochemical sensing platform for the detection of paracetamol (PCM). By modifying a screen-printed carbon electrode (SPE) with ZnFe2O4 NPs, the electrochemical characteristics of the ZnFe2O4/SPE and the electrochemical oxidation of PCM were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and differential pulse voltammetry (DPV) methods. The calculated electrochemical kinetic parameters from these techniques including electrochemically active surface area (ECSA), peak-to-peak separation (ΔEp), charge transfer resistance (Rct), standard heterogeneous electron-transfer rate constants (k0), electron transfer coefficient (α), catalytic rate constant (kcat), adsorption capacity (Γ), and diffusion coefficient (D) proved that the as-synthesized ZnFe2O4 NPs have rapid electron/mass transfer characteristics, intrinsic electrocatalytic activity, and facilitate the adsorption-diffusion of PCM molecules towards the modified electrode surface. As expected, the ZnFe2O4/SPE offered excellent analytical performance towards sensing of PCM with a detection limit of 0.29 μM, a wide linear range of 0.5-400 μM, and high electrochemical sensitivity of 1.1 μA μM-1 cm-2. Moreover, the proposed ZnFe2O4-based electrochemical nanosensor also exhibited good repeatability, high anti-interference ability, and practical feasibility toward PCM sensing in a pharmaceutical tablet. Based on these observations, the designed electrochemical platform not only provides a high-performance nanosensor for the rapid and highly efficient detection of PCM but also opens a new avenue for routine quality control analysis of pharmaceutical formulations.

Influence of phase structure of MnO2 for enhancing the electrochemical sensitivity of environmental pollutant chlortetracycline

Electrochemical sensing of chlortetracycline (CTC) using α and β- MnO2 nanowires has been studied. The influence of different phase structures (α and β) of MnO2 nanowires on the determination of chlortetracycline (CTC) was studied systematically. To enhance the sensitivity of MnO2, a high conductivity microporous carbon (MC) was employed as a support matrix for MnO2. The electrochemical sensing results illustrate that the α-MnO2 exhibited better electrochemical performance than β-MnO2. This better activity was correlated with its excellent properties like more exposed MnO6 edges, higher conductivity, and lowest average oxidation state . The kinetics study illustrated that the MnO2 modified electrodes perform much better than the bare electrodes. The number of electron transfer, electron transfer coefficient, and diffusion coefficient of CTC were calculated from the scan rate effect; the values are 1, 0.50, and 1.581 × 10−6 cm2 s−1 respectively. Amperometry was used to calculate the lowest detection limit (LOD) at a potential of 0.82 V. The α-MnO2/MC electrode exhibits a better linear range (1–55 µM) with a LOD value of 103 nM towards CTC. Furthermore, the proposed sensor exhibited better anti-interference ability towards KCl, kanamycin sulfate, zinc acetate, magnesium chloride, tetracycline, streptomycin sulfate, and oxytetracycline. The sensor's ability to accurately determine the level of CTC in samples of drinking water, tap water, poultry farm soil, and milk highlights its suitability for industrial applications. The developed sensor showed better reproducibility (RSD=0.45%) and repeatability (RSD=2.06%) towards CTC. Therefore, the proposed sensor can be used as a more practical platform for monitoring environmental contaminants.

Electrochemical Determination of Thiophene by Dicyandiamide/Graphene Oxide/Modified Graphite Electrode in Gasoline by Square Wave Voltammetry (SWV)

An efficient stable electrochemical method for the determination of thiophene as a sulfur model compound in gasoline has been investigated based on the electrodeposition of graphene oxide and dicyandiamide on graphite electrode by cyclic voltammetry. The electroactive layer performance was considered by linear sweep voltammetry and square wave voltammetry by examining scan rates and their relevant equations to evaluate the electrochemical parameters. This modified electrode has high electrocatalytic characteristics to irreversible electrooxidation of thiophene. The electron transfer coefficient (α) was equal to 0.78, the electron transfer rate constant (log KS) was 3.2 s−1, and the saturated adsorptive capacity of the electroactive substance at the electrode surface (Γmax) was 1.14 × 10−8 mol cm−2 at pH 8 at low working potential of 0.5 V versus Ag/AgCl reference electrode. Scanning electron microscopy of the surface revealed the nanostructure of electrodeposited films and the morphology. This sensor is capable of electrochemical response to thiophene over the concentration range from 25 to 250 nmol L−1 with a detection limit of 8.31 nmol L−1, and a quantification limit of 25.18 nmol L−1. The method’s reliability was checked regarding the simulated gasoline samples and the desired response and sensitivity were provided. The wide dynamic range, low detection limit, favorable precision and accuracy, and fast response with no interferences confirm the ability of this sensor for thiophene determination. This nano-sensor can be used for electrochemical in-situ direct monitoring of liquid fuel desulfurization processes.