Mechanism Of Electrooxidation Research Articles

Electrochemical detection of antimalarial drug (Amodiaquine) using Dy-MOF@MWCNT composites to prevent erythrocytic stages of plasmodium species in human bodies

Herein, we report on fabrication of dysprosium-based metal–organic framework (Dy-MOF)@multiwalled carbon nanotubes (MWCNT) composites modified with glassy carbon electrode (Dy-MOF@MWCNT/GC) as a working electrode for Antimalarial drug detection. Dy-MOF@MWCNT composites was prepared by sonochemical process along with ultrasonication. The composite structure, phase purity, morphology and composition of the composites were confirmed by X-ray diffraction, Scanning electron microscope, and X-ray photoelectron spectroscopy. Further, Dy@MWCNT composites were deposited on a glassy carbon electrode by drop casting method, and used as an electrode material to efficiently detect Amodiaquine (ADD) by electrochemical techniques such as CV and DPV. The as-prepared Dy@MWCNT composite material showed the oxidation peak current of ADD to be ∼ 60 % higher than other unmodified GC electrodes and showed a low charge transfer resistance (R ct) of 24 Ω. The Dy@MWCNT provided a broad linear range of 0.4 to 20 µM with a limit of detection of 0.377 μM and sensitivity of 1.817 μA.μM−1 for the detection of ADD. According to the pH study, the amount of electrons and protons involved in the electrochemical processes of ADD was calculated and a plausible mechanism for ADD electro-oxidation was proposed. Thus, the prepared sensor exhibited practical usefulness by determining the ADD drug in human urine samples. Hence, the results shows that the Dy@MWCNT- modified sensor has good electrocatalytic activity for the redox of ADD.

Fabrication of block-shaped Sb2O3 and flower-shaped CoNPs nanocomposites for ultrasensitive antioxidant quercetin sensing and its electrooxidation mechanism

Quercetin (Qu) is a natural pentahydroxyflavone that is thought to counteract oxidative cell damage by acting as an effective free radical scavenger, exhibits estrogenic and anticancer activities. Therefore, it is important to detect the content of Qu and study its electrooxidation mechanism. Here, we prepared Sb2O3@MWCNTs/GCE sensors based on block-shaped antimony oxide (Sb2O3) and multi-walled carbon nanotubes (MWCNTs), and Pyrrole/CoNPs/GCE sensors with pyrrole and flower-shaped cobalt nanoparticles (CoNPs), respectively, for ultrasensitive detection of Qu, as these modified nanocomposites have excellent catalytic effect towards Qu. In contrast, the second sensor allowed ultrasensitive detection of Qu and had a wider linear range (0.10–100.00 μmol·L−1), a detection limit of 0.033 μmol·L−1 and a sensitivity of 8.98 µA·μmol·L−1·cm−1. In addition, both sensors showed good repeatability, stability and selectivity. The recoveries of antioxidant Qu in ginkgo biloba by these two sensors ranged from 95.50 to 103.86 %, and the Qu accounted for 35.60 % and 39.57 % of the flavonol glycosides (19.20 mg) in the tablets. These studies demonstrate the potential application of both sensors in practical assays.

Zirconium-based hydrophobic-MOFs as innovative electrode modifiers for flibanserin determination: Exploring the electrooxidation mechanism using a comprehensive spectroelectrochemical study.

Threedifferent types of Zr-based MOFs derived from benzene dicarboxylic acid (BDC) and naphthalene dicarboxylic acid as organic linkers (ZrBDC, 2,6-ZrNDC, and 1,4-ZrNDC) were synthesized. They were characterized using X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform IR spectroscopy (FT-IR), and Transmission electron microscopy (TEM). Their hydrophilic/hydrophobic nature was investigated via contact angle measurements; ZrBDC MOF was hydrophilic and the other two (ZrNDC) MOFs were hydrophobic. The three MOFs were combined with MWCNTs as electrode modifiers for the determinationof a hydrophobic analyte, flibanserin (FLB), as a proof-of-concept analyte. Under the optimized experimental conditions, a significant enhancement in the oxidation peak current of FLB was observed when utilizing 2,6-ZrNDC and 1,4-ZrNDC, being the highest when using 1,4-ZrNDC. Furthermore, a thorough investigation of the complex oxidation pathway of FLB was performed by carrying out simultaneous spectroelectrochemical measurements. Based on the obtained results, it was verified that the piperazine moiety of FLB is the primary site for electrochemical oxidation. The fabricated sensor based on 1,4-ZrNDC/MW/CPE showed an oxidation peak of FLB at 0.8V vs Ag/AgCl. Moreover, it showed excellent linearity for the determinationof FLB in the range 0.05 to 0.80μmol L-1 with a correlation coefficient (r) = 0.9973 and limit of detection of 3.0nmol L-1. The applicability of the developed approach was demonstrated by determinationof FLB in pharmaceutical tablets and human urine samples with acceptable repeatability (% RSD values were below 1.9% and 2.1%, respectively) and reasonable recovery values (ranged between 97 and 103% for pharmaceutical tablets and between 96 and 102% for human urine samples). The outcomes of the suggested methodology can be utilized for the determinationof other hydrophobic compounds of pharmaceutical or biological interest with the aim of achieving low detection limits of these compounds in various matrices.

Unveiling the effect of Pt addition on Ag/C catalyst for enhanced glycerol electrooxidation

This study investigates the performance of Ag/C and a range of Ag100-xPtx/C nanoparticles as electrocatalysts for glycerol electrooxidation reaction (GEOR). Low amounts of Pt (<2 %) were spontaneously deposited on Ag-supported nanoparticles using Ag as a sacrificial metal. The primary aim of the study is to determine the impact of adding a small amount of Pt to the Ag/C catalyst. Cyclic voltammetry is employed to assess the electrocatalyst's performance, while in situ Fourier Transform Infrared (FTIR) spectroscopy is used to examine the formed reaction intermediates and products. Additionally, physical characterization techniques such as XRD and XPS are applied to analyze the material structure. The Ag100-xPtx/C series of catalysts show a significant improvement in the glycerol oxidation process with the addition of 0.25 % of Pt to the material composition compared to pure Ag. It is observed that the enhancement performance reaches a limit at a Pt composition of approximately 7 % in the metallic nanoparticles, indicating that further increases in Pt content do not yield additional improvements. The in situ FTIR studies reveal that the presence of Pt on the Ag surface leads to a distinct glycerol electrooxidation mechanism compared to using Ag alone. Small amounts of Pt deposits promote C−C−C bond breaking, as evidenced by the selective formation of formic acid and CO2. FTIR results demonstrate a preference for carboxylic acid formation, with no significant evidence of dihydroxyacetone (DHA) production. The findings emphasize the critical role of Pt composition in the electrooxidation of glycerol paving the way for the design and development of more efficient and sustainable electrooxidation catalysts.

Electrochemical detection of bicalutamide in sepiolite clay sensing platform: Its possible electrooxidation mechanism, determination, and DNA interaction

AbstractA carbon paste sensor was modified with sepiolite clay particles (SC/CPE) to quantify the bicalutamide (BICA). BICA's probable oxidation mechanism and the interaction between calf thymus DNA (dsDNA) were investigated (in aqueous medium, pH 4.8) for the first time. Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) were used for the investigation of surface morphology and electrochemical characteristics. The effect of the amount of SC, supporting electrolyte, and pH was optimized. Under optimum conditions, the developed sensor exhibited a linear response between 0.223 and 20.0 μM. The detection of the limit was found to be 0.069 μM. The sensor was successfully applied to quantify BICA in biological and pharmaceutical samples. Finally, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) provided new insight into the interaction between BICA and ds‐DNA. The kinetic parameters for the free DNA, diffusion coefficient (D), heterogeneous rate constant (ks), and electrode surface concentration (Γ) were calculated to be 4.22×10−5 cm2 s−1, 0.57 s−1 and 7.67×10−9 mol cm−2, respectively. The (ds‐DNA)‐BICA complex parameters were 4.56×10−6 cm2 s−1, 0.70 s−1, and 1.61×10−9 mol cm−2. In addition, binding constant (K) and Gibbs free energy change (ΔG°) were 6.02×105 M−1 and −32.97 kJ mol−1, respectively.

A review of carbon-based catalysts and catalyst supports for simultaneous organic electro-oxidation and hydrogen evolution reactions

Producing organic electro-oxidation and hydrogen evolution reactions (HER) simultaneously in an electrolytic cell is an appealing method for generating valuable chemicals at the anode while also producing H2 at the cathode. Within this framework, the task of designing energy-saving electrocatalysts with high selectivity and stability is a considerable challenge. Carbon-based catalysts, along with their supports, have emerged as promising candidates due to their diverse sources, large specific surface area, high porosity and multidimensional characteristics. This review summarizes progress from 2012 to 2022, in the use of carbon-based catalysts and their supports for organic electrooxidation and HER. It delves into outer-sphere electrooxidation mechanisms involving molecule-mediated oxidation and oxidative radical coupling reactions, as well as inner-sphere electrooxidation mechanisms, encompassing both acidic and alkaline electrolytes. The review also explores prospective research directions within this domain, addressing various aspects such as the design of electrocatalytic materials, the study of the relationship between the structure and properties of electrocatalysts, as well as examining their potential industrial applications.

Sensing platform for the highly sensitive detection of catechol based on composite coupling with conductive Ni3(HITP)2 and nanosilvers.

Catechol, which has a high toxicity and low degradability, poses significant risks to both human health and the environment. Tracking of catechol residues is essential to protect human health and to assess the safety of the environment. We constructed sensing platforms to detect catechol based on the conductive metal-organic frameworks [Ni3(HITP)2] and their nanosilver composites. The reduction process of catechol at the Ni3(HITP)2/AgNP electrode is chemically irreversible as a result of the difference in compatibility of the oxidation stability and conductivity between the Ni3(HITP)2/AgNS and Ni3(HITP)2/AgNP electrodes. The electrochemical results show that the Ni3(HITP)2/AgNS electrode presents a lower detection limit of 0.053 μM and better sensitivity, reproducibility and repeatability than the Ni3(HITP)2/AgNP electrode. The kinetic mechanism of the catechol electrooxidation at the surface of the electrode is controlled by diffusion through a 2H+/2e- process. The transfer coefficient is the key factor used to illustrate this process. During the electrochemical conversion of phenol to ketone, more than half of ΔG is used to change the activation energy. We also studied the stability, anti-interference and reproducibility of these electrode systems.

Electronic Structure Effect of PtCo Alloy with Adjustable Compositions for Efficient Methanol Electrooxidation.

Various efficient strategies have been developed to overcome the anodic electrocatalyst issue of methanol-based fuel cells owing to their complicated methanol electrooxidation mechanism. In this work, PtCo nanoparticles with adjustable compositions supported on multiwalled carbon nanotubes (Pt1Cox/MWCNTs) through the adsorbing-coating-annealing-etching route were synthesized. Compared with the Pt/C catalyst, Pt1Co3/MWCNTs exhibit better electrocatalytic MOR activity in both activity and durability. Notably, the electrochemical mass and specific activity of the as-prepared catalyst are 1.04 mA μg-1Pt and 2.18 mA cm-2, respectively, which are higher than those of the Pt/C catalyst. Moreover, the as-prepared sample revealed lower onset potential during the CO stripping test. Furthermore, the Pt1Co3/MWCNTs possess a lower current density decrease rate in chronoamperometry and cyclic durability tests. The enhancement of activity and stability of Pt1Co3/MWCNTs could be ascribed to their ordered morphological structure, the electronic interaction between MWCNTs and PtCo nanoparticles, and the suitable electronic structure effect between Pt/Co ratios. The concept of the catalyst design in this study offers a different guideline for constructing the novel methanol electrooxidation catalyst, which will accelerate the widespread fuel cell practical application.

Effects of pH and Temperature on Ethanol Photocatalytic Oxidation using Por-Si/Pd

The paper presents the results of a study of ethanol electrooxidation on por-Si/Pd structures formed by metal-stimulated etching. The emphasis on the influence of external factors, such as temperature, pH of ethanol solution and external radiation in the visible and UV ranges on the catalytic activity of the structure. The empirical mechanism of ethanol electrooxidation on the por-Si/Pd structure under additional external illumination is presented.

Electrochemical Valorization of Glycerol: Catalyst Development and Product Analysis

The growing interest in biofuels as a substitute for traditional fossil fuels has raised environmental concerns about the extensive production of their by-products. Among these by-product, Glycerol, which accounts for over 10% of the total by-products, resulted in the production of nearly 4 billion liters in 2020. (1) Glycerol is a polyol organic molecule, viscous, and water-soluble liquid that if not disposed of properly, it can have detrimental impacts on the environment, including soil and water pollution, ultimately contributing to an increase in the carbon footprint. Hence, addressing this growing concern has prompted a surge of interest in developing sustainable and economically viable techniques for converting glycerol into value-added products.The electrochemical glycerol oxidation reaction (GOR) is a cost-effective and reliable method to enable circular economy practices by selectively producing highly value-added products such as dihydroxyacetone, glyceric acid, and glycolic acid from glycerol. However, it requires the development of active, selective, and stable electrocatalysts to steer GOR at low overpotentials. To date, catalysts based on platinum group metals (PGMs) have outperformed other GOR catalysts in terms of activity. However, in addition to the high cost of fabrication, these catalysts are susceptible to surface poisoning by glycerol intermediates, thereby impeding their commercialization due to the absence of long-term stability. (2) As a result, developing electrocatalysts based on earth-abundant element has become the focal point in GOR catalyst research.Here in, we highlight the latest advancements in the development of low-PGM content GOR catalysts. Our discussion focuses on the strategies for understanding how the type and concentration of PGM can influence selectivity, with a particular emphasis on the significance of GOR overpotentials. We also aim to highlight the inconsistencies in GOR product analyses, specifically regarding the use of H-NMR analysis, with an ultimate goal of advancing accurate GOR product quantification. References Nomanbhay S, Hussein R, Ong MY. Sustainability of biodiesel production in Malaysia by production of bio-oil from crude glycerol using microwave pyrolysis: a review. Green Chemistry Letters and Reviews. 2018;11(2):135-57. Li T, Harrington DA. An Overview of Glycerol Electrooxidation Mechanisms on Pt, Pd and Au. ChemSusChem. 2021;14(6):1472-95.

Vacancy‐induced catalytic mechanism for alcohol electrooxidation on nickel‐based electrocatalyst

AbstractOwing to outstanding performances, nickel‐based electrocatalysts are commonly used in electrochemical alcohol oxidation reactions (AORs), and the active phase is usually vacancy‐rich nickel oxide/hydroxide (NiOxHy) species. However, researchers are not aware of the catalytic role of atom vacancy in AORs. Here, we study vacancy‐induced catalytic mechanisms for AORs on NiOxHy species. As to AORs on oxygen‐vacancy‐poor β‐Ni(OH)2, the only redox mediator is electrooxidation‐induced electrophilic lattice oxygen species, which can only catalyze the dehydrogenation process (e.g., the electrooxidation of primary alcohol to carboxylic acid) instead of the C−C bond cleavage. Hence, vicinal diol electrooxidation reaction involving the C−C bond cleavage is not feasible with oxygen‐vacancy‐poor β‐Ni(OH)2. Only through oxygen vacancy‐induced adsorbed oxygen‐mediated mechanism, can oxygen‐vacancy‐rich NiOxHy species catalyze the electrooxidation of vicinal diol to carboxylic acid and formic acid accompanied with the C−C bond cleavage. Crucially, we examine how vacancies and vacancy‐induced catalytic mechanisms work during AORs on NiOxHy species.

Vacancy-induced catalytic mechanism for alcohol electrooxidation on nickel-based electrocatalyst.

Owing to outstanding performances, nickel-based electrocatalysts are commonly used in electrochemical alcohol oxidation reactions (AORs), and the active phase is usually vacancy-rich nickel oxide/hydroxide (NiOx Hy ) species. However, researchers are not aware of the catalytic role of atom vacancy in AORs. Here, we study vacancy-induced catalytic mechanisms for AORs on NiOx Hy species. As to AORs on oxygen-vacancy-poor β-Ni(OH)2 , the only redox mediator is electrooxidation-induced electrophilic lattice oxygen species, which can only catalyze the dehydrogenation process (e.g., the electrooxidation of primary alcohol to carboxylic acid) instead of the C-C bond cleavage. Hence, vicinal diol electrooxidation reaction involving the C-C bond cleavage is not feasible with oxygen-vacancy-poor β-Ni(OH)2 . Only through oxygen vacancy-induced adsorbed oxygen-mediated mechanism, can oxygen-vacancy-rich NiOx Hy species catalyze the electrooxidation of vicinal diol to carboxylic acid and formic acid accompanied with the C-C bond cleavage. Crucially, we examine how vacancies and vacancy-induced catalytic mechanisms work during AORs on NiOx Hy species.

Revealing Adsorption Conformation and Electro-oxidation Mechanism of Urea on the Ni Film Catalyst by In Situ ATR-SEIRAS

Revealing Adsorption Conformation and Electro-oxidation Mechanism of Urea on the Ni Film Catalyst by In Situ ATR-SEIRAS

Electrochemical surface-enhanced Raman spectroscopy analysis of malachite green on gold substrates

The pH-sensitivity and electroactivity of malachite green (MG), a cationic dye, can potentially affect the surface-enhanced Raman spectroscopy (SERS) profile during electrochemical SERS (EC-SERS) analysis. An EC-SERS investigation was performed by acquiring dynamic SERS profiles of MG on Au SERS substrates at various applied potentials to elucidate the electrochemistry of MG at the molecular level. The appropriate EC-SERS potential window of MG, mass and electron transfer modes, and the number of electrons and protons in the redox process were determined by cyclic voltammetry. The EC-SERS parameters (pH and type of supporting electrolyte) were optimized. The highest SERS signal was achieved by chronoamperometry SERS (CA-SERS) and CV-SERS at an applied potential of 0.6 V (vs. Ag/AgCl) using 0.1 M phosphate buffer at pH 4 as the supporting electrolyte. Plausible mechanisms for electrooxidation and SERS signal enhancement were proposed. The oxidized form of MG, conformational changes, and evolution of the adsorption orientation were successfully elucidated using CV-SERS. This study provides molecular-level insight into the adsorption orientation of MG and its oxidized form, which involves aromatic rings with a tilted upright orientation at positive applied potentials. The mechanism of SERS signal enhancement is expounded, which is valuable for developing EC-SERS-based MG sensing.

Electrochemical sensor for ultrasensitive sensing of biotin based on heme conjugated with gold nanoparticles and its electrooxidation mechanism.

We report the fabrication of a facile sensor using heme conjugated with gold nanoparticles (AuNPs) in situ on a glass carbon electrode (GCE) for the ultrasensitive determination of biotin without antibody or streptavidin. The use of heme and AuNPs as dual amplifiers allows a very broad detection range from 0.0050 to 50.0000μmol·L-1 and a very low detection limit of 0.0016μmol·L-1. The mechanistic aspects were elucidated using electrochemical analyses and frontier orbital calculations showing that the electrooxidation of biotin involves a one-electron and a one-proton transfer, generating biotin sulfoxide. The heme/AuNPs/GCE sensor exhibited excellent selectivity, reproducibility and stability, indicating high robustness. The recovery was between 97.20 and 105.70% with RSD less than 8.71%, suggesting good practicability. Our studies demonstrate that this approach can be used to detect and quantify biotin in a range of foods, including milk, infant formula, flour, orange juice, mango juice, egg white and egg yolk. Furthermore, all measurements do not require any intricate preparation or pre-treatment of the foods, thus representing a great potential for point-of-care testing.

An electrochemical aptamer sensor for rapid quantification sulfadoxine based on synergistic signal amplification of indole and MWCNTs and its electrooxidation mechanism

Unreasonable disposal of sulfadoxine (SDX) causing food safety and eventually result water pollution, and shows great significance of detection. A sensitive unit Aptamer (Apt) was adopted to construct an electrochemical sensor BSA/Apt/indole/MWCNTs/GCE with the synergistic amplification of multi-walled carbon nanotubes (MWCNTs) and indole for the detection of SDX. Optimization of the conditions allowed the detection of SDX shows a wide linear range from 0.10 to 1000.00 µmol/L by differential pulse voltammetry (DPV). The LOD and sensitivity were determined to be 0.033 µmol/L and 0.29 µA/(µmol/L·cm²), respectively. The recovery rate of SDX in pork and lake water samples range 98.57 %−104.93 %, 93.6 %−106.2 %, respectively. Both the relative standard deviation (RSD) was lower than 7.40 %, which proved that the sensor has good practicability. In addition, DFT calculation was established that a restricted of B3LYP and a basis set of 6–31 G, the electrooxidation of SDX involves two-electron and one-proton transfer.

Electrooxidation of chlorophene and dichlorophen by reactive electrochemical membrane: Key determining factors of removal efficiency

This study systematically investigated the variable main electrooxidation mechanism of chlorophene (CP) and dichlorophen (DCP) with the change of reaction conditions at Ti4O7 anode operated in batch and reactive electrochemical membrane (REM) modes. Significant degradation of CP and DCP was observed, that is, CP exhibited greater removal efficiency in batch mode at 0.5–3.5 mA cm−2 and REM operation (0.5 mA cm−2) with a permeate flow rate of 0.85 cm min−1 under the same reaction conditions, while DCP exhibited a faster degradation rate with the increase of current density in REM operation. Density functional theory (DFT) simulation and electrochemical performance tests indicated that the electrooxidation efficiency of CP and DCP in batch mode was primarily affected by the mass transfer rates. And the removal efficiency when anodic potentials were less than 1.7 V vs SHE in REM operation was determined by the activation energy for direct electron transfer (DET) reaction, however, the adsorption function of CP and DCP on the Ti4O7 anode became a dominant factor in determining the degradation efficiency with the further increase of anodic potential due to the disappeared activation barrier. In addition, the degradation pathways of CP and DCP were proposed according to intermediate products identification and frontier electron densities (FEDs) calculation, the acute toxicity of CP and DCP were also effectively decreased during both batch and REM operations.

Photoelectro-catalytic oxidation of monoethanolamine: From the study of electrooxidation mechanism to the development of high-efficient Ni-based photoelectro-catalysts

Monoethanolamine (MEA) electrooxidation occurring on Ni catalyst has proven to be a viable tactics for simultaneous MEA degradation and energy recovery. However, the excessively large overpotential (1505 mV) on Ni catalyst either causes high electricity consumption when acquiring H2 from MEA-containing electrolyzer or leads to low energy output when extracting electricity from direct MEA fuel cell. In this context, the reaction mechanism of MEA electrooxidation on Ni-based catalyst is deciphered at first by employing a specially designed three-step electrochemical procedure and in-situ Raman spectroscopy. Electrochemical data deconvolutions indicate the indirect electrochemical-chemical reaction path, via Ni(OH)2/NiOOH mediator, occupies ∼2.5 % of the total catalytic current density at 0.55 V vs. Ag/AgCl and the direct oxidation of MEA ranks the rest ∼97.5 %. To decrease the onset potential of MEA oxidation, a photoelectric-catalytic system including high-efficient Ni-based photoelectric-catalyst, where Ni is intimately coated on TiO2 by in-situ photodeposition to achieve the shortest carrier transport channel between Ni(OH)2 and TiO2, is developed. Results show the overpotential of MEA electrooxidation under illumination significantly drops to 255 mV. Such a Ni@TiO2/FTO electrode also exerts excellent durability toward MEA oxidation.

Investigations on the electrochemical behavior of sunitinib and metabolites N-desethyl-sunitinib and sunitinib-N-oxide and its selective determination using molecularly imprinted polymer-based sensor

Sunitinib (SUN) is an orally administered tyrosine kinase inhibitor and is mainly metabolized via N-deethylation to form the primary active metabolite N-desethyl-sunitinib (M1) and via oxidation to sunitinib-N-oxide (M2). In this study, we first investigated the electrochemical behavior of sunitinib and its N-desethyl and N-oxide metabolites on a bare glassy carbon electrode (GCE) by cyclic voltammetry (CV) technique. Based on the results, a plausible electrooxidation mechanism is proposed, yielding the oxo-desfluoro-sunitinib (quinoneimine metabolite) via oxidative defluorination of sunitinib. After this phase of the study, due to the low sensitivity and selectivity results obtained from the bare GCE, we aimed to develop the first molecularly imprinted polymer (MIP)-based electrochemical sensor for the sensitive and selective determination of SUN. The MA@SDS/MIP-GCE sensor was prepared by thermal polymerization of methacrylic acid (MA) as a functional monomer in the presence of SUN on a GCE surface under the optimized parameters such as template/monomer ratio, drop amount, polymerization temperature and time, removal solution and time, and rebinding time, which affect the structure and response of the sensor. The surface characterization of the developed sensor was performed by scanning electron microscopy (SEM), and the electrochemical characterization was performed by CV and electrochemical impedance spectroscopy (EIS). The electroanalytical performance of the MA@SDS/MIP-GCE sensor was tested by differential pulse voltammetry (DPV) under the optimized conditions in comparison with the NIP-based sensor. The linearity of the developed sensor for the determination of SUN was investigated in the concentration range of 0.5 – 5.0 nM for standard and serum solutions with low LOD and LOQ values. The application of the MIP sensor for the determination of SUN in pharmaceutical dosage form (capsule) and serum samples was demonstrated with excellent recoveries. The results showed that the MA@SDS/MIP-GCE sensor is a sensitive, specific, selective, rapid, and economical option for the quantitative determination of SUN.

Determination of vanillin in different food samples by using SMM/Au@ZIF-67 electrochemical sensor

Vanillin is a popular flavoring agent in many food products. Simple, fast, and reliable quantification of this compound is crucial for the food industry. In this work, we have developed a new electrochemical sensor for accurate detection of vanillin in various real samples. The composite electrode was made of sodium montmorillonite nanoclay (SMM) and gold nanoparticles modified ZIF-67 (Au@ZIF-67), in which SMM contributes to the large adsorption capacity of the analyte, ZIF-67 and SMM supply more sensing active sites, and gold nanoparticles provide high electrical conductivity. The sensing electrode was comprehensively characterized using Brunauer–Emmett–Teller, EDS, XRD, SEM, FTIR, and TEM, and its electrochemical behavior for determination of vanillin including the electrooxidation mechanism of vanillin and different parameters such as scan rate and pH value was investigated. The result revealed that a two electron-two proton process was involved in the electrooxidation of vanillin, which takes place more readily due to the lower potential on the surface of SMM/Au@ZIF-67/carbon paste electrode. The new composite electrode was also more sensitive to vanillin detection with an anodic peak current almost 2.6 times more than that of the bare electrode. A linear sensing concentration range was established between 1 and 1200 nM with a detection limit of 0. 3 nM and a limit of quantitation of 1 nM. For real samples, the sensor demonstrated excellent recovery rates and reliability that was comparable to the standard high-performance liquid chromatography method.