Electrochemical Techniques Research Articles

Study on the efficient electrocatalytic depolymerization of α-O-4 bond in lignin assisted by simple electrolyte

Lignin is anticipated to serve as a replacement for dwindling fossil fuel resources owing to its abundant sources and renewable nature. The electrochemical oxidation technique for depolymerizing lignin has garnered significant interest for its environmentally friendly and mild operating conditions. Nevertheless, the current utilization of auxiliary electrolytes, predominantly organic bases, ionic liquids, and other specialized substances, poses a constraint on the widespread adoption of this approach. Furthermore, there is a scarcity of instances where electrochemical technology has been employed to depolymerize the α-O-4 bond in lignin for the production of highly selective acetals. In this study, a sodium chloride/methanol (NaCl/MeOH) system was utilized for the direct depolymerization of the α-O-4 bond in a lignin model molecule, specifically benzyl phenyl ether (BPE). The optimal conditions resulted in a 95.2 % conversion rate of the BPE substrate and a high yield of 94.5 % for the main product, benzaldehyde dimethyl acetal(Bda). This research offers a promising approach for the electrocatalytic depolymerization of α-O-4 bonds in lignin, leading to the selective production of acetal chemicals using a common auxiliary electrolyte at room temperature in just 2 h.

Sodium salt of dodecyl benzene sulphonic acid as an effective corrosion inhibition for different heat-treated steel in sulphuric acid medium

Abstract The purpose of this work is to use electrochemical and gravimetric techniques to investigate the inhibition of DBSS on the corrosion of heat-treated dual-phase AISI 1040 steel in a 0.5 M sulphuric acid solution at 35 °C. The corrosion studies are performed by potentiodynamic polarization study (PDP), electrochemical impedance study (EIS), and gravimetric method. To confirm the inhibition surface characterization like x-ray diffraction technique (XRD) analysis, scanning electron microscopy (SEM), and EDS analysis are performed. Depending on the phase change of metals due to heat treatment, the corrosion inhibition of the heat-treated metal increased when it was exposed to 0.5 M H2SO4 at 35 °C in the presence of dodecyl benzene sulphonic acid sodium salt (DBSS) inhibitor. The highest inhibition efficiency of 63%, 82%, 87%, 43%, and 63% was obtained for AISI 1040 steel at heat treatment conditions of Normalized, Quenched at 700 °C, Quenched at 750 °C, Quenched at 790 °C and Quenched at 900 °C respectively. In the gravimetric and electrochemical study, the IE increases with the increase with the concentration of DBSS unto 75% from gravimetric analysis and 87% from PDP analysis for Quenched at 750 °C and 790 °C respectively. The metal protection is achieved by heat treatment process as well as by using DBSS as inhibitor. Corrosion inhibition on the metal’s surface was confirmed by SEM and XRD. In addition, the adsorption of DBSS on the anodic and cathodic sites of the metal surface was well explained.

Atomic-scale understanding of microstructural evolution in electrochemical additive manufacturing of metallic nickel

Atomic-level manufacturing is fundamentally concerned with the precise removal, addition, and migration of material at the atomic and close-to-atomic scale (ACS). Tip-based electrochemical deposition, a quintessential ACS electrochemical additive manufacturing technique, offers promising prospects for achieving bottom-up fabrication of metallic micro/nano structures. However, the complex physicochemical reactions involved in electrodes lead to a limited understanding of the mechanisms underlying atomic electrodeposition and structural evolution. For the first time, this study proposes electric double-layer controlled electrochemical kinetics and investigates the effect of direct current (DC) and pulse current (PC) on nickel atomic electrodeposition using molecular dynamics (MD) simulations. The findings reveal that compared to DC electrodeposition, PC electrodeposition results in more orderly deposition morphology, improved surface smoothness, reduced dislocation density, and lower crystal distortion, with these effects being particularly pronounced under low pulse duty ratio conditions. In addition, the pulse frequency significantly influences the morphology and structure of the deposit. The high pulse frequency yields smoother surfaces with local protrusions, while the low frequency favors the formation of orderly and dense structures excepting slightly increased roughness. This study provides critical insights into understanding the microscopic mechanisms of atomic-scale electrodeposition processes and achieving atomically controlled tip-based electrochemical additive manufacturing of micro/nanodevices.

Selective Detection of Paraquat in Adulterated and Complex Environmental Samples Using Raman Spectroelectrochemistry.

Growing demand for pesticides has created an environment prone to deceptive activities, where counterfeit or adulterated pesticide products infiltrate the market, often escaping rapid detection. This situation presents a significant challenge for sensor technology, crucial in identifying authentic pesticides and ensuring agricultural safety practices. Raman spectroscopy emerges as a powerful technique for detecting adulterants. Coupling the electrochemical techniques allows a more specific and selective detection and compound identification. In this study, we evaluate the efficacy of spectroelectrochemical measurements by coupling a potentiostat and Raman spectrograph to identify paraquat, a nonselective herbicide banned in several countries. Our findings demonstrate that applying -0.70 V during measurements yields highly selective Raman spectra, highlighting the primary vibrational bands of paraquat. Moreover, the selective Raman signal of paraquat was discernible in complex samples, including tap water, apple, and green cabbage, even in the presence of other pesticides such as diquat, acephate, and glyphosate. These results underscore the potential of this technique for reliable pesticide detection in diverse and complex matrices.

Observation of monotonic surface charging at polycrystalline platinum-electrolyte interface using streaming current method

Surface charging characteristics at polycrystalline Pt-electrolyte interfaces were studied using a novel combination of electrochemical techniques and electrokinetic streaming current methods developed by our group [Saha et al., 2019]. Surface charge typically increases with increasing electric potential on a metal, and this trend is commonly referred to as monotonic charging. Based on theoretical models, it was suggested that the Pt-electrolyte interface might deviate from this trend and have negative charge above the potential of zero charge (PZC) due to the metal's strong chemisorption properties [Huang et al., 2016]. We attempted to experimentally determine the validity of this claim using our method. In addition to the surface charging relations, we also quantified the effect of anion adsorption (oxide, chloride, sulfate) on surface charging. The experimental method also allowed us to observe the slow time-dependent growth of oxides on Pt surface. Since our first publication in 2019 [Saha et al., 2019], we were able to develop the setup to be more efficient that enabled us to apply higher potential on the metal, observe stronger ion adsorption effects on surface charging, and obtain more reliable data. Our recent experimental study shows that Pt charging remains monotonic and does not reverse due to chemisorption of oxides nor strong anion adsorption in the potential window where the charge reversal was theoretically shown to occur.

Electrodeposition of actinides: Optimization of deposition parameters by chronoamperometric studies

To quantify alpha-emitting radionuclides by alpha spectrometry, it is necessary to prepare a thin and uniform alpha source on a suitable substrate. Electrodeposition is the most used electrochemical technique for this purpose. In order to better understand the electrochemical process carried out in the electrodeposition of actinides, in particular the selection of the current densities applied, a chronoamperometric study of the electrodeposition of actinides (Th, U, Pu, Am and Cm), in three different electrolytes (Na2SO4/H2SO4, NH4NO3, NaF) using stainless steel and platinum as cathode and anode, respectively, is presented. The corresponding polarization curves (potential vs. current density), characteristic for each electrolyte and actinide used, were constructed from the chronoamperometric data, The limiting diffusion current as well as the minimum current necessary for the electrodeposition process to take place were determined. To achieve a quantitative electrodeposition of actinides, a balance between OH- production and the thickness of the OH- layer formed near the cathode must be reached. These parameters are controlled by the electrolyte used and the current density applied to the electrochemical system. Actinides were electrodeposited mainly in the form of oxides, according to Raman spectroscopy results.

Eco-Friendly and Sustainable Inhibitors for Steel Corrosion in Acidic Media

The inhibitory action of eco-friendly food waste extracts, Red Beta Vulgaris leaves (R.B.V.L) and Prunus cerasus seeds (P.C.S), on the B7 grade steel corrosion in 1.0 M HCl were investigated utilizing chemical and electrochemical measurements. The functional groups of both extracts have been predicted utilizing Fourier transform infrared spectroscopy (FTIR). The potentiodynamic polarization technique reveals that the two extracts act as a mixed-type inhibitor. The electrochemical impedance spectroscopy technique shows that the corrosion process is controlled via charge transfer. Both extracts exhibit a maximum inhibitory efficiency of 75%. Langmuir and Flory–Huggins isotherms, as well as the Kinetic-thermodynamic model, were used to study the inhibition mode of both extracts. The values of the change in free energy of adsorption, ΔGads, demonstrate that the adsorption occurs via the physisorption (electrostatic) mechanism. The activation parameters were determined and discussed. The quantum chemical calculations have proceeded to show the main active ingredients.

Constructing Pr-doped CoOOH catalytic sites for efficient electrooxidation of 5-hydroxymethylfurfural

Electrocatalytic conversion of renewable biomass is emerging as a promising route for sustainable chemical production; hence it urgently calls for developing efficient electrocatalysts with low potentials and high current densities. Herein, a Pr-doped Co(OH)2 hexagonal sheet (Pr/Co = 1/9, in mole) is synthesized by electrodeposition as highly performant catalyst for 5-hydroxymethylfurfural (HMF) oxidation reaction (HMFOR) to produce 2,5-furandicarboxylic acid (FDCA). This novel and low-cost catalyst possesses a rather low onset potential of 1.05 V (vs. RHE) and requires only 1.10 V (vs. RHE) to reach a current density of 10 mA cm−2 for HMFOR, significantly outperforming Co(OH)2 benchmark (i.e., 210 mV higher to reach 10 mA cm−2). The origin of Pr promotion effect as well as the evolution of CoOOH catalytic sites and HMFOR process has been deeply elucidated by physical characterizations, kinetic experiments, in situ electrochemical techniques, and theoretical calculations. The unique Pr-ameliorated CoOOH active centers enable 100% conversion of HMF, 99.6% selectivity of FDCA, and 99.7% Faraday efficiency, with a superior cycling durability toward HMFOR. This can be one of the most outstanding results for Co-based HMFOR catalysts to date in the literature. Thereby this work can help open up new horizons for constructing novel and efficient Co-based electrocatalysts by the utilization of lanthanide elements.

Enhanced electrochemical performances of ternary polypyrrole/MXene/Gum arabic composites as supercapacitors electrode materials

The development of supercapacitor electrodes for high energy storage applications requires the use of ternary composites made of PPy, Mxene, Gum Arabic (PPy/Mxene/GA) these materials are special because they have new characteristics like cyclic stability, and high specific capacitance. The pure PPy, PPy/Mxene and PPy/Mxene/Gum Arabic show the shifting and appearance of new peaks in UV-Visible spectra, which are further supported by the Fourier transform infrared spectroscopy (FT-IR). The appearance of new peaks in X-ray diffraction (XRD) of PPy confirms presence of Mxene and Gum Arabic, which is in agreement with the energy dispersive X-ray (EDX) analysis. The electrochemical techniques such as Cyclic Voltammetry (CV), Galvanostatic Charge Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS) show that the (PPy/Mxene/GA) ternary composite maintains 94 % of the specific capacitance retention after 2000 cycles and; reaches a maximum specific capacitance of 657.64 F/g at 1 A/g. As compared to Pure PPy and PPy/Mxene composite the PPy/Mxene/GA composite show small intrinsic resistance Rs and charge transfer Rct values 0.11Ω and 6.15Ω respectively. The outstanding electrochemical properties of PPy/Mxene/GA composite are ascribed to the blending of three different type compounds PPy, Mxene and GA and theirs mutual beneficial effects. These findings show that ternary composite material holds great promise for use in these condition involving portable electronic storage devices.

Effect of Citric Acid Hard Anodizing on the Mechanical Properties and Corrosion Resistance of Different Aluminum Alloys.

Hard anodizing is used to improve the anodic films' mechanical qualities and aluminum alloys' corrosion resistance. Applications for anodic oxide coatings on aluminum alloys include the space environment. In this work, the aluminum alloys 2024-T3 (Al-Cu), 6061-T6 (Al-Mg-Si), and 7075-T6 (Al-Zn) were prepared by hard anodizing electrochemical treatment using citric and sulfur acid baths at different concentrations. The aim of the work is to observe the effect of citric acid on the microstructure of the substrate, the mechanical properties, the corrosion resistance, and the morphology of the hard anodic layers. Hard anodizing was performed on three different aluminum alloys using three citric-sulfuric acid mixtures for 60 min and using current densities of 3.0 and 4.5 A/dm2. Vickers microhardness (HV) measurements and scanning electron microscopy (SEM) were utilized to determine the mechanical characteristics and microstructure of the hard anodizing material, and electrochemical techniques to understand the corrosion kinetics. The result indicates that the aluminum alloy 6061-T6 (Al-Mg-Si) has the maximum hard-coat thickness and hardness. The oxidation of Zn and Mg during the anodizing process found in the 7075-T6 (Al-Zn) alloy promotes oxide formation. Because of the high copper concentration, the oxide layer that forms on the 2024-T6 (Al-Cu) Al alloy has the lowest thickness, hardness, and corrosion resistance. Citric and sulfuric acid solutions can be used to provide hard anodizing in a variety of aluminum alloys that have corrosion resistance and mechanical qualities on par with or better than traditional sulfuric acid anodizing.

Binding-induced activation of CRISPR-Cas12a using PAM-engineered toehold switch and DNA tile architectures for enhanced detection of thrombin

This study presents a novel biosensor that integrates CRISPR-Cas12a technology with DNA tile-based architectures to enhance thrombin detection. Utilizing PAM-engineered toehold switches, the biosensor dynamically activates the CRISPR-Cas12a system upon thrombin recognition, significantly improving both sensitivity and specificity. The label-free electrochemical detection method offers rapid, cost-effective analysis, making it ideal for real-time clinical applications. The biosensor achieved an impressive detection limit of 103 aM, surpassing traditional methods and setting a new standard for thrombin assays. The biosensor's robust performance in complex biological samples, such as diluted human serum, demonstrates its reliability for clinical diagnostics. This is particularly important for the early diagnosis and management of thrombotic and coagulation-related disorders. By combining advanced genetic engineering with traditional electrochemical techniques, the biosensor not only optimizes detection but also expands its potential applications across various biomedical fields. Overall, this biosensor provides a powerful and innovative tool for thrombin detection, offering enhanced diagnostic accuracy, faster patient management, and potential cost savings in healthcare. Its superior performance and adaptability highlight its promise for broader adoption in clinical diagnostics and other biosensing applications.

An super sensitive Multi-Modal controlled release biosensor with label- and enzyme- free assisted single step simultaneously detect multiple breast cancer biomarkers

Despite the fact that homogeneous biosensing strategies have been proven to be advantageous, it remains a difficult task to identify multiple tumor biomarkers. Our proposition entails the creation of a groundbreaking biosensor that combines electrochemical and fluorescent techniques, enabling simultaneous detect multiple biomarkers with label- and enzyme-free assistance in a single step. Porous UIO-66-NH2 nanovessels loaded with 3,3′,5,5′ −tetramethylbenzidine (TMB) and methylene blue (MB) double signal dyes, along with double-stranded DNA (dsDNA) formed by the aptamer chain of human epidermal growth factor receptor-2 (HER2) and estrogen receptor (ER) and its complementary chain as a gated switch to the envelope MOFs, were utilized to create functional MOFs (dsDNA@MB@UIO and dsDNA@TMB@UIO). When HER2 and ER targets are present, the chain replacement reaction led to the formation of a biomarker-aptamer complex, resulting in the destruction of the dsDNA structure on the surface of MOF and the liberation of MB and TMB. The concentration of the two target biomarkers determines the strength of the electrochemical and fluorescent signals produced. By combining targeted biomarkers, signal enhancement, and dual-signal detection into one unified process, the amount of test error caused by the multi-step detection needed in prior studies is significantly decreased. We executed the detect HER2 and ER, achieving detection limits of 4.7 and 5.9 fg/mL in 4.7–1000 pg/mL linear range with good selectivity, stability, reproducibility, and acceptable applicability. The proposed biosensor for developing dsDNA@MB@UIO and dsDNA@TMB@UIO is promising for the early and sensitive detection of cancer biomarkers.

Synthesis and Structure-Property Relationship of meso-Substituted Porphyrin- and Benzoporphyrin-Thiophene Conjugates toward Electrochemical Reduction of Carbon Dioxide.

A novel series of ZnII-trans-A2B2 porphyrins and benzoporphyrins bearing phenyl and thiophene-based meso-substituents was successfully synthesized and characterized by spectroscopic and electrochemical techniques. Systematic comparison among the compounds in this series, together with the corresponding A4 analogs previously studied by our group, led to the understanding of the effects of π-conjugated system extension of a porphyrin core through β-fused rings, replacement of the phenyl with the thiophene-based meso-groups, and introduction of additional thiophene rings on thienyl substituents on photophysical and electrochemical properties. Oxidative electropolymerization through bithiophenyl units of both A4 and trans-A2B2 analogs was achieved, resulting in porphyrin- and benzoporphyrin-oligothiophene conjugated polymers, which were characterized by cyclic voltammetry and absorption spectrophotometry. Preliminary studies on catalytic performance toward electrochemical reduction of carbon dioxide (CO2) was described herein to demonstrate the potential of the selected compounds for serving as homogeneous and heterogeneous electrocatalysts for the conversion of CO2 to carbon monoxide (CO).

Growth of WO3 nanostructure deposited on TiO2 nanotube arrays for electrochemical enzyme-free glucose sensor

In this study, a novel WO3-TiO2 hybrid nanostructure-based electrochemical non-enzymatic glucose biosensor has been developed. The anodization method was utilized to successfully produce TiO2 nanotubes on Ti6Al4V alloy functioning as substrates and WO3 nanomaterial decorate on the surface of TiO2 nanotubes (TNTs) deposited through electrochemical technique. The incorporation of WO3 on TNTs has resulted in a high electroactive surface and more degradation resistance in comparison to pure TNTs, resulting in enhanced electron transfer rate and electrode stability. High-resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction were used to investigate the crystalline structure and morphology of the WO3-TiO2 nanostructure. The electrochemical properties of the hybrid electrodes were investigated employing amperometry, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The hybrid electrode had a promising sensitivity (1228.12 μA/mM/cm2), low detection limit (0.19 mM), wide linear range (1.0–6.5 mM), and short response time (2-s). The sensors also demonstrated superior levels of reproducibility, repeatability, and stability.

Improvement of Power Density and COD Removal in a Sediment Microbial Fuel Cell with α-FeOOH Nanoparticles

Sediment microbial fuel cells (SMFC) are bioelectrochemical systems that can use different wastes for energy production. This work studied the implementation of nanoparticles (NPs) of α-FeOOH (goethite, which is well-known as a photoactive catalyst) in the electrodes of an SMFC for its potential use for dye removal. The results obtained demonstrate the feasibility of the NPs activation with the electrical potential generated in the electrodes in the SMFC instead of the activation with light. The NPs of α-FeOOH were synthesized using a hydrothermal process, and the feasibility of a conductive bio-composite (biofilm and NPs) formation was proven by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and electrochemical techniques. The improvement of the power density in the cell was more than twelve times higher with the application of the bio-composite, and it is attributed mostly to the presence of NPs. The results also demonstrate the NPs effect on the increase of the electron transfer, which resulted in 99% of the COD removal. The total electrical energy produced in 30 days in the SMFC was 1.2 kWh based on 1 m2 of the geometric area of the anode. The results confirm that NPs of α-FeOOH can be used to improve organic matter removal. Moreover, the energy produced due to its activation through the potential generated between the electrodes suggests the feasibility of its implementation for dye removal.

In-depth study of a newly synthesized imidazole derivative as an eco-friendly corrosion inhibitor for mild steel in 1 M HCl: Theoretical, electrochemical, and surface analysis perspectives

The present study is concerned with the corrosion inhibition and adsorption behaviour of a series of novel imidazole derivatives. The compounds under investigation are 5,5-diphenyl-3-propyl-2-(propylthio)-3,5-dihydro-4 H-imidazol-4-one (AM3) and 3-allyl-2-(allylthio)-5,5-diphenyl-3,5-dihydro-4 H-imidazol-4-one (AM6). The objective of this study is to evaluate the efficacy of 5,5-diphenyl-3,5-dihydro-4 H-imidazol-4-one (AM6) as a corrosion inhibitor on mild steel immersed in a 1.0 M hydrochloric acid medium. This comprehensive study assesses the efficacy of these derivatives through a range of electrochemical and spectroscopic analysis techniques. Additionally, polarisation curves, electrochemical impedance spectroscopy and advanced computer simulations were employed to evaluate the efficacy and inhibition mechanism of imidazole derivatives, thereby facilitating a more profound understanding of their anticorrosive capacity. The results obtained from potentiodynamic polarisation (PDP), electrochemical frequency modulation (EFM) and electrochemical impedance spectroscopy (EIS) measurements demonstrate that the inhibition efficiency increases with increasing imidazole derivative concentration. Conversely, an inverse relationship is observed between inhibition efficiency and temperature. The thermodynamic parameters ΔG°_ads and ΔH°_ads corroborate the conclusion that the adsorption process is predominantly chemical in nature. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) were employed to characterise the surface morphology. The maximum protection afforded by imidazole derivatives was 95.2 % and 93 % for compounds AM3 and AM6, respectively. Polarisation curves indicated that imidazole derivatives exhibited mixed inhibition behaviour. Surface analysis demonstrated that imidazole derivatives were effectively adsorbed onto the carbon surface, thereby significantly reducing acid damage. This finding was corroborated by DFT calculations, as well as Monte Carlo (MC) and molecular dynamics (MD) simulations. These simulations provided a comprehensive insight into the adsorption of imidazole and its protonated form onto the carbon surface, offering valuable insight into the corrosion inhibition mechanism.

Improving the electrocatalytic activity of the copper (II) metal-organic framework by functionalized imidazolate linker and functionalized carbon nanoparticles for detection of acyclovir

With the aim of expansion of nanocomposite materials in electrochemical sensors, the use of nanostructures as the electrode modifier has been shown to improves the kinetics of the electron transfer reactions and consequently increases the sensitivity of the sensors. So, in this study, a new electrochemical sensor was fabricated by using the nanocomposite of copper (II) metal–organic framework with functionalized imidazolate linker [Cu3(BTC)2-2-MIM] and cationic functionalized carbon nanoparticles (CFCNPs) at the glassy carbon electrode (GCE); Cu3(BTC)2-2-MIM/CFCNPs/GCE. The as prepared nanocomposite; Cu3(BTC)2-2-MIM/CFCNPs was characterized using various instrumental techniques. To identify the capabilities and electrocatalytic activity of the synthesized nanocomposite in analytical chemistry, it was used as an electrochemical modifier along with suitable electrochemical techniques. In this regard, the prepared modified electrode; Cu3(BTC)2-2-MIM/CFCNPs/GCE was utilized to the electrooxidation and determination of the acyclovir (ACR) in NaOH solution. Under optimal experimental conditions, the Cu3(BTC)2-2-MIM/CFCNPs/GCE showed low detection limit (0.24 µM) over the concentration ranges of 2.49–84.28 μM of ACR. On the other hand, the present sensor has robust stability, good reproducibility, high selectivity and sensitivity (5.907 µAµM−1 cm−2) in electrodetermination of ACR. Also, the diffusion coefficient of ACR (DACR = 9.25 × 10−6 cm2 s−1), the transfer coefficient (α = 0.34) and catalytic rate constant (kcat = 10.1 × 105 cm3 mol−1 s−1) of ACR electrooxidation reaction were estimated at the surface of modified electrode in NaOH solution. Finally, the Cu3(BTC)2-2-MIM/CFCNPs/GCE was applied as a promising and low-cost sensor for determination of the ACR in actual pharmaceutical formulations and biological samples.

Electrochemical Aptasensor with Antifouling Properties for Label-Free Detection of Oxytetracycline.

Oxytetracycline (OTC) is a widely employed antibiotic in veterinary treatment and in the prevention of infections, potentially leaving residues in animal-derived food products, such as milk, that are consumed by humans. Given the detrimental effects of prolonged human exposure to antibiotics, it has become imperative to develop precise and sensitive methods for monitoring the presence of OTC in food. Herein, we describe the development and results of a preliminary label-free electrochemical aptasensor with antifouling properties designed to detect OTC in milk samples. The sensor was realized by modifying a gold screen-printed electrode with α-lipoic acid-NHS and an amine-terminated aptamer. Different electrochemical techniques were used to study the steps of the fabrication process and to quantify OTC in the presence of the Fe(CN)64-/Fe(CN)63- redox couple The detectable range of concentrations satisfy the maximum residue limits set by the European Union, with an limit of detection (LOD) of 14 ng/mL in phosphate buffer (BP) and 10 ng/mL in the milk matrix, and a dynamic range of up to 500 ng/mL This study is a steppingstone towards the implementation of a sensitive monitoring method for OTC in dairy products.

Facile fabrication of bismuth oxide anchored graphene oxide for the effective electrochemical sensing of diuron

BackgroundDiuron (DU), a weed controller widely used in the agricultural industry, prolonged conception of this agrochemical residue contaminated with environmental water bodies and soil sources could cause an acute impact on the human health system. This work utilized the electrochemical determination technique due to their rapid detection, outstanding sensitivity, and economical purpose. MethodsThe electrochemical behavior of DU at the γ-Bi2O3 microplates interconnected with sheet-like graphene oxide (GO) as a surface-modified electrode was scrutinized by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The surface-modified γ-Bi2O3/GO/GCE elucidates superior electrocatalytic performance towards the irreversible oxidation response of diuron than the other surface-modified electrode in the phosphate buffer solution of 0.1 M. Significant findingsThe γ-Bi2O3/GO/GCE electrode displayed an extensive detection range of 0.1–631 µM with a 0.751 µM lower detection limit furthermore, noticeable 0.0280 µA µM-1 cm-2 sensitivity for diuron determination. In addition, the DPV experiment exposed that the γ-Bi2O3/GO/GCE electrode achieves stupendous selectivity, durability, and acceptable feasibility of the real-time samples.

Deepening the Understanding of Carbon Active Sites for ORR Using Electrochemical and Spectrochemical Techniques.

Defect-containing carbon nanotube materials were prepared by subjecting two commercial multiwalled carbon nanotubes (MWCNTs) of different purities to purification (HCl) and oxidative conditions (HNO3) and further heat treatment to remove surface oxygen groups. The as-prepared carbon materials were physicochemically characterized to observe changes in their properties after the different treatments. TEM microscopy shows morphological modifications in the MWCNTs after the treatments such as broken walls and carbon defects including topological defects. This leads to both higher surface areas and active sites. The carbon defects were analysed by Raman spectroscopy, but the active surface area (ASA) and the electrochemical active surface area (EASA) values showed that not all the defects are equally active for oxygen reduction reactions (ORRs). This suggests the importance of calculating either ASA or EASA in carbon materials with different structures to determine the activity of these defects. The as-prepared defect-containing multiwalled carbon nanotubes exhibit good catalytic performance due to the formation of carbon defects active for ORR such as edge sites and topological defects. Moreover, they exhibit good stability and methanol tolerances. The as-prepared MWCNTs sample with the highest purity is a promising defective carbon material for ORR because its activity is only related to high concentrations of active carbon defects including edge sites and topological defects.