Anodic Peak Current Research Articles

Sonochemical synthesis of lanthanum ferrite nanoparticle-decorated carbon nanotubes for simultaneous electrochemical determination of acetaminophen and dopamine.

A new nanocomposite consisting of lanthanum ferrite nanoparticles (LaFeO3 NPs) integrated with carbon nanotubes (CNTs) was fabricated via facile sonochemical approach. The engineered nanocomposite was applied to simultaneously determine acetaminophen (ACP) and dopamine (DA) in a binary mixture. The LaFeO3 NPs@CNT probe possesses several advantages such as superior conductivity, large surface area, and more active sites, improving its electrocatalytic activity towards ACP and DA. Under optimized conditions, the anodic peak currents (Ipa) linearly increased with increasing concentration of ACP and DA in the range 0.069-210 µM and 0.15-210 µM, respectively. The sensitivity of LaFeO3 NPs@CNTs/glassy carbon electrode (GCE) for detecting ACP and DA is 7.456 and 5.980 μA·μM-1·cm-2, respectively. The detection limits (S/N = 3) for ACP and DA are 0.02 μM and 0.05 μM, respectively. Advantages of LaFeO3 NPs@CNTs/GCE for the detection of ACP and DA include wide linear ranges, low-detection limits, good selectivity, and long-term stability. The as-fabricated electrode was applied to determine ACP and DA in pharmaceutical formulations and human serum samples with recoveries ranging from 97.7 to 103.3% and an RSD that did not exceed 3.7%, confirming the suitability of the proposed sensor for the determination of ACP and DA in real samples. This study not only presents promising opportunities for enhancing the sensitivity and stability of electrochemical sensors used in the detection of bioanalytes but also significantly contributes to the progress of unique and comprehensive biochemical detection methodologies.

Label-free and ultrasensitive electrochemical transferrin detection biosensor based on a glassy carbon electrode and gold nanoparticles

In this study, we developed a label-free and ultrasensitive electrochemical biosensor for the detection of transferrin (Tf), an important serum biomarker of atransferrinemia. The biosensor was fabricated by using glassy carbon electrode (GCE) and modified with gold nanoparticles (AuNPs) via electroless deposition. The electrochemical characteristics of the GCE-AuNPs biosensors were characterized using cyclic voltammetry and electrochemical impedance spectroscopy analysis. Differential pulse voltammetry was used for quantitative evaluation of the Tf-antigen by recording the increase in the anodic peak current of GCE-AuNPs biosensor. The GCE-AuNPs biosensor demonstrates superior sensing performance for Tf-antigen fortified in buffer, with a wide linear range of 0.1 to 5000 μg/mL and a limit of detection of 0.18 μg/mL. The studied GCE-AuNPs biosensor showed excellent sensitivity, selectivity, long-term storage stability and simple sensing steps without pretreatment of clinical samples. This GCE-AuNPs biosensor indicates great potential for developing a Tf detection platform, which would be helpful in the early diagnosis of atransferrinemia. The developed GCE-AuNPs biosensor holds great potential in biomedical research related to point of care for the early diagnosis and monitoring of diseases associated with aberrant serum transferrin levels. These findings suggest that the GCE-AuNPs biosensor has great potential for detecting other serum biomarkers.

Highly water dispersible poly (caffeic acid - L-arginine)-MoS2 nanocomposite modified sensor for effective electrochemical detection of amlodipine drug

The present work applied a facile, green, and versatile approach to preparing self-organized redox polymers on 2D-MoS2 (Molybdenum Disulfide) nanosheets. It was utilized as the modified electrode material for electrochemical determination of 1, 4-dihydropyridine-based antihypertensive drugs viz amlodipine (AMD). Naturally available caffeic acid was used as a precursor, and it was polymerized through a 1, 4-Michael addition reaction with L-arginine. Oxidants and amine functional groups of L-arginine synergistically promote the polymerization of caffeic acid (P (CA-LA)). The P(CA-LA) in the 2D-MoS2 matrix was stabilized via self-assembly by intermolecular interaction between catechol groups and MoS2 sheets. The ultra-sonication process induced the subsequent polymerization and simultaneous exfoliation of MoS2 sheets. The self-assembled P(CA-LA)-MoS2 nanocomposite exhibits a good cyclic voltammetric response with excellent electrochemical oxidation of AMD. The electrochemical response of AMD was explored using a glassy carbon electrode (GCE) modified with P(CA-LA)-MoS2 nanocomposite employing differential pulse voltammetry (DPV). Under the optimized experimental conditions, electrochemical detection of AMD has been performed with a linear correlation between the anodic peak current of AMD observed at 0.8 V. Additionally, the designed self-assembled redox polymer-based nanocomposite sensor exhibited superior selectivity for the detection of AMD with two linear ranges from 0.010 to 16.82 µM and 16.82 to 433.3 µM with good detection limits of 3.6 nM. Moreover, the synergic interactions of polymers and MoS2 and their self-assembly nature can offer a good sensitivity of 0.42 μA μM−1 cm−2. Hence, the electrochemical behavior of self-assembled P(CA-LA)-MoS2/GCE may provide new insights into the recent era of electrodes and sensors.

Hierarchical porous covalent organic framework-based sensor for the detection of neurodegenerative disorder biomarkers

Guanosine is an essential biomarker that enacts an important role in neuroprotection against brain-related activities, influences the metabolism of fatty acids, and assists in the improvement of the gastrointestinal tract. A facile and selective electrochemical sensor has been developed for the sensing of guanosine based on a hierarchical porous covalent organic framework. Owing to the distinctive 2D porous architecture and ordered framework of TpBD-COF, the irreversible electrooxidation of guanosine occurred at 1.03 V (vs. SCE) in phosphate buffer solution at pH 6. The anodic peak currents under optimal conditions were linear with guanosine concentration within the range of 0.123–720 μM with a LOD of 40.63 nM under various optimal conditions. Moreover, the developed biosensor was used to determine guanosine in pharmaceutical tablets to confirm its potential application in the healthcare industry.

Fired brick microparticles assisted oxidative radical polymerization of pyrrole for electrochemical sensing: Application to the determination of ciprofloxacin and metanil yellow in food products and environmental samples

A novel and simple hybrid sensor was constructed for the electrochemical sensing of ciprofloxacin (CPX) and metanil yellow (MEY). The sensor consists of fired brick microparticles (FB) modified with a thin film of poly(pyrrole) (PPy), which were used as a modifier for carbon paste electrode (CPE). Adding HCl to FB (which is predominantly made of Fe2O3) resulted in the release of Fe3+ ions, which aided in the oxidative polymerization of pyrrole monomer. The polar groups and aromatic rings found in the composition of PPy@FB provide more anchoring sites for adsorption of CPX and MEY, facilitating their electro-chemical oxidation. Under optimum conditions, the anodic peak currents (Ipa) showed a linear increase with increasing the concentration of CPX over the concentration range of 0.011–16.0 µmol/L and MEY in the range of 0.012–16.0 µmol/L. Limit of detections (LODs, S/N = 3) were calculated as 0.0035 µmol/L and 0.0042 µmol/L for CPX in milk and water samples, respectively. LOD for MEY in turmeric and water samples were 0.0032 µmol/L and 0.0036 µmol/L, respectively. The advantages of the as-fabricated sensor compromise greenness, simplicity, low-cost, reproducibility, sensitivity, selectivity, and adequate stability. The fabricated sensor was efficiently applied to detect CPX and MEY in different matrices including industrial water, milk, and turmeric samples with satisfactory recoveries % and low RSDs values.

Copper nanoparticle modified chain-like platinum nanocomposites for electro-oxidation of C1-, C2-, and C3- type alcohols

The design of efficient, durable and inexpensive electrocatalysts is of great importance in the development of direct alcohol fuel cells, a clean energy source. In this context, in this study, chain-like platinum-copper (PtCu) nanoparticles were synthesised by chemical reduction method to be used in alcohol oxidation studies. X-Ray diffraction analysis (XRD) of the synthesised nanoparticles showed the formation of PtCu crystal structure. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) analysis showed the formation of chain-like PtCu structures and particles with an average size of 4.04 nm. These PtCu nanocomposite structures were used in electro oxidation studies of ethanol, methanol and 2-propanol. As a result of the oxidation studies, anodic peak currents of 253.1 mA cm−2, 187.7 mA cm−2, 37.2 mA cm−2 were obtained for methanol, ethanol and 2-propanol, respectively. It was also observed that PtCu has a higher electrochemically active surface area than bare Pt and is more tolerant to CO. The results showed that the synthesised catalyst showed very high electrocatalytic activity and stability in alcohol fuel cells. With this study, important results have been given for the stability problem, which is one of the biggest problems in fuel cells.

A highly sensitive and green electroanalytical method for the determination of favipiravir in pharmaceutical and biological fluids

BackgroundFavipiravir is currently used for the treatment of coronavirus disease-2019 (COVID-19).ObjectiveA highly sensitive and eco-friendly electroanalytical method was developed to quantify favipiravir.MethodThe voltammetric method optimized a sensor composed of reduced graphene oxide / modified carbon paste electrode in the presence of an anionic surfactant, improving the favipiravir detection limit. The investigation reveals that favipiravir-oxidation is a diffusion-controlled irreversible process. The effects of various pH and scan rates on oxidation anodic peak current were investigated.ResultsThe developed method offers a wide linear dynamic range of 1.5–420 ng/mL alongside a higher sensitivity with a limit of detection in the nanogram range (0.44 ng/mL) and a limit of quantification in the low nanogram range (1.34 ng/mL).ConclusionThe proposed method was applied for the determination of favipiravir in the dosage form, human plasma and urine samples. The developed method exhibited good selectivity in the presence of two potential electroactive biological interferants, uric acid which increases during favipiravir therapy and the recommended co-administered vitamin C. The organic solvent-free method greenness was evaluated via the Green Analytical Procedure Index, The present work offers a simple, sensitive and environment-friendly method fulfilling green chemistry concepts.

A Simple Electroanalytical Method for Detecting Carminic Acid in Foods through a Glassy Carbon Electrode Modified with Chitosan in the Presence of Allura Red

AbstractIn this report, a new method involving glassy carbon electrodes modified with chitosan (Cs) was tested for the detection of carminic acid (CA) in the presence of allure red by square wave voltammetry. The modified electrode (Cs/GCE) presented activity toward the oxidation of CA at potential values less than 0.3 V The signal is generated from the oxidation of carboxylic acid in the chemical structure of CA. Compared to that of the unmodified electrode, the anodic peak current of the Cs/CGE electrode increased by more than 500 %, and the oxidation potential shifted to a lower potential. This result indicates that the sensitivity increases and the energy to oxidize CA decreases with the Cs/GCE. The optimal parameters were pH 3.0 and PBS buffer, the square wave voltammetry with accumulation time was tACC 30 s, the accumulation potential was EACC 0.0 V, the oxidation signal was proportional to the concentration of CA between 0.99 and 10.90 μmol/L, and the detection limit was 0.20 μmol/L. The relative standard deviation (R.S. D) was 5.0 % using five different electrodes. The Cs/GCE was used for food samples spiked with CA with consistent results

A novel detection method for neohesperidin dihydrochalcone (NHDC) based on ZIF-8/ErGO composite modified electrode in milk

Neohesperidin dihydrochalcone (NHDC), as a high-intensity sweetener, has been widely used to be a new food additive. In this study, zeolitic imidazolate framework (ZIF)− 8/electrochemical reduced graphene oxide (ErGO) composite materials were favorably constructed onto the glassy carbon electrode (GCE) by two simple steps without any dispersant, and an electrochemical sensing of NHDC was developed. The morphology and its structure of the composite materials were characterized by SEM and Raman. The two-electron two-step redox mechanism was investigated by cyclic voltammetry (CV). The first anodic peak current of NHDC at ZIF-8/ErGO electrode is about 3.8 times as much as that of ErGO GCE and 42 times of ZIF-8 GCE under the optimized conditions. The linear relationship between oxidation peak current of NHDC and its concentration is ranged from 0.08 to 80 μM by linear sweep voltammetry (LSV), with the detection limit of 31.5 nM (based on S/N = 3). Finally, the modified electrode was used to detect NHDC in milk samples with a recovery rate of 98.3∼106.3%, which implied its feasibility for the determination of NHDC in actual samples.

3D-printed holder for drawing highly reproducible pencil-on-paper electrochemical devices.

Pencil drawing is one of the simplest and most cost-effective ways of fabricating miniaturized electrodes on a paper substrate. However, it is limited by the lack of reproducibility regarding the electrode drawing process. A 3D-printed pencil holder (3DPH) is proposed here for simple, reproducible, and low-cost hand-drawn fabrication of paper-based electrochemical devices. 3DPH was designed to keep pressure and angulation of the graphite mine constant on the paper substrate using a micromechanical pencil regardless of the user/operator. This approach significantly improved the reproducibility and cost of making reliable pencil-drawn electrodes. The results showed high reproducibility and accuracy of the 3DPH-assisted electrodes prepared by 4 different operators in terms of sheet resistance and electrochemical behavior. Cyclic voltammetric (CV) curves in the presence of [Fe(CN)6]3-/4- redox probe showed only 3.9% variation for the anodic peak currents of different electrodes prepared by different operators when compared with electrodes prepared without the 3D-printed support. SEM analyses revealed a more uniform graphite deposition/design of the electrodes prepared with 3DPH, which corroborates the results obtained by CV. As a proof of concept, 3DPH-assisted pencil-drawn graphite electrodes were employed for dopamine detection in synthetic saliva, showing a proportional increase in anodic peak current at 0.12 V vs. carbon pRE with increasing dopamine (DA) concentration, with a detection limit of 0.39μmol L-1. Moreover recoverywas in the range93-104% of DA (4-7% RSD) in synthetic saliva for three different concentrations, demonstrating the reliability of the approach. Finally, we believe this approach can make pencil-drawn technology more robust, accessible, reliable, and inexpensive for real on-site applications, especially in hard-to-reach locations or research centers with little investment.

Graphene quantum dots functionalized Ce-ZnO nanofibers with enriched oxygen vacancy sites morphology to improve the efficiency of selective electrochemical detection of Hg (II)

Herein, GQD functionalized Ce-ZnO hybrid nanofibers (GQD/Ce-ZnO NFs) towards selective Hg2+ ion detection through DPV technique was investigated. The hybrid NFs were synthesized via a facile electrospinning process and their physical properties were investigated through XRD, SEM-EDS, HR-TEM with SAED pattern, XPS, UV-DRS, and ESR techniques. Notably, the plane value, phase recognition, and purity of the GQD/Ce-ZnO NFs were examined through XRD analysis. The chemical states, chemical composition, and weight percentage of the elements were examined by the XPS and EDS analysis. Similarly, the width of the hybrid NFs and structural morphology were elucidated through SEM and HR-TEM analysis. The existence of oxygen vacancies (vo) was verified using UV-DRS and ESR techniques. The electrochemical characteristics of GQD/Ce-ZnO NFs-modified glassy carbon electrode (GCE) was investigated using diverse electrochemical methodologies like cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Remarkably, DPV studies depict that GQD/Ce-ZnO NFs modified GCE achieved high anodic peak current 3.48 × 10−4 A upon successive addition of Hg2+ (0.1–100 μM). The anodic peak current was directly proportional to the mercury ions concentration throughout a wide range of 0.1 × 10−6 to 100 × 10−6 M with a LOD of 267 nM in an optimized experimental condition. The GQD/Ce-ZnO NFs modified GCE showed remarkable reproducibility, with an RSD value of 1.81 %. Additionally, it maintained a strong current retention rate of 71.5 % over 12 days, indicating commendable long-term stability.

Unveiling the Remarkable Antioxidant Activity of Plant-Based Fish and Seafood Analogs through Electrochemical Sensor Analysis.

The global consumption of vegan foods is experiencing an expressive upward trend, underscoring the critical need for quality control measures based on nutritional and functional considerations. This study aimed to evaluate the functional quality of caviar and salmon analog food inks based on pulses combined with nano ingredients and produced in our laboratory (LNANO). The primary objective of this work was to determine the total antioxidant compounds contained in these samples using a voltammetric technique with a glassy carbon electrode. The samples underwent ethanolic extraction (70%) with 1 h of stirring. The voltammograms were acquired in a phosphate buffer electrolyte, pH 3.0 with Ag/AgCl (KCl 3 mol L-1) as the reference electrode and platinum wire as the auxiliary electrode. The voltammograms revealed prominent anodic current peaks at 0.76-0.78 V, which are attributed to isoflavones. Isoflavones, known secondary metabolites with substantial antioxidant potential commonly found in pulses, were identified. The total isoflavone concentrations obtained ranged from 31.5 to 64.3 mg Eq genistein 100 g-1. The results not only validated the efficacy of the electrochemical sensor for quantifying total antioxidant compounds in the samples but also demonstrated that the concentration of total isoflavones in caviar and salmon analogs fell within the expected limits.

Electrochemical Determination of Epinephrine in Pharmaceutical Preparation Using Laponite Clay-Modified Graphene Inkjet-Printed Electrode.

Epinephrine (EP, also called adrenaline) is a compound belonging to the catecholamine neurotransmitter family. It can cause neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis. This work describes an amperometric sensor for the electroanalytical detection of EP by using an inkjet-printed graphene electrode (IPGE) that has been chemically modified by a thin layer of a laponite (La) clay mineral. The ion exchange properties and permeability of the chemically modified electrode (denoted La/IPGE) were evaluated using multi-sweep cyclic voltammetry, while its charge transfer resistance was determined by electrochemical impedance spectroscopy. The results showed that La/IPGE exhibited higher sensitivity to EP compared to the bare IPGE. The developed sensor was directly applied for the determination of EP in aqueous solution using differential pulse voltammetry. Under optimized conditions, a linear calibration graph was obtained in the concentration range between 0.8 µM and 10 μM. The anodic peak current of EP was directly proportional to its concentration, leading to detection limits of 0.34 μM and 0.26 μM with bare IPGE and La/IPGE, respectively. The sensor was successfully applied for the determination of EP in pharmaceutical preparations. Recovery rates and the effects of interfering species on the detection of EP were evaluated to highlight the selectivity of the elaborated sensor.

Voltammetric examination of hydroquinone at ordinary and nano-architecture platinum electrodes

The electrochemical behavior of hydroquinone was examined experimentally using cyclic voltammetry, convolution transform, and deconvolution transform at clean ordinary and nanostructured mesoporous platinum electrodes in 1 mol/l HClO4. The cyclic voltammogram of hydroquinone (HQ) at an ordinary Pt electrode displays an anodic peak at 0.610 V and a cathodic peak at 0.117 V, with a scan rate of 50 mV·s–1. Excellent linearity was recorded between the anodic or cathodic peak currents of hydroquinone and the square root of the scan rate (υ1/2). The anodic and cathodic peak potential separation (∆Ep) was found to be 463 ± 3 mV vs. the saturated calomel electrode (SCE). It was noted that the value of peak potential separation increased with increasing the scan rate. The type of electrode reaction at both platinum electrodes in 1 mol/l HClO4 was examined and discussed. The electrochemical parameters and the nature of the mechanistic pathway of the investigated HQ were determined experimentally and ascertained via a numerical simulation method.

Carbon nanofiber-based voltammetric sensor for the simultaneous quantification of β-Lactum antibiotics as amoxicillin and clavunate potassium

The present work reports a novel electrochemical method for the simultaneous quantification of amoxicillin (AMX) and clavunate potassium (CLV) at carbon nanofiber-modified glassy carbon electrode (GCE) by using square wave voltammetry due to its high sensitivity, low cost, simplicity, and degrades the signal-to-noise ratio. The developed sensor was characterized by Scanning electron microscopy, Transmission electron microscopy, X-Ray powder diffraction, Infrared spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The fabricated electrode exhibited excellent electrocatalytic activity towards electrochemical oxidation of both compounds in BR buffer pH 2.0. All the instrumental parameter that affects the anodic peak current of AMX and CLV was also optimized during the investigation. Two well-resolved oxidation peaks at 0.55 V and 1.05 V for AMX and CLV were optimized at the time of analysis of these analytes. The limit of detection was 98 nM for AMX and 95 nM for CLV and the limit of quantification was 0.298 µM and 0.289 µM for AMX and CLV respectively, achieved at the fabricated sensor. The proposed method has also been examined in pharmaceutical formulation and biological samples with satisfactory recovery results.

BaO-MWCNT composite material-based electrocatalytic amperometric sensor for the detection of environmentally hazardous Diuron

Population growth has prompted industrialization and intensive agricultural methods, which are linked to issues with flora and fauna and result in deteriorated water quality due to contamination by hazardous, persistent pesticides. In this paper, we have concentrated on the herbicide Diuron (DIU) determination as one such priority pollutant. This study was conducted keeping in mind key factors for a proficient electrochemical sensor development for DIU. The working electrode surface area was modified with the as-synthesized BaO-MWCNT composite material to reinforce the efficiency of the Faradaic reaction. A three-fold magnification in DIU anodic peak current was witnessed at the modified electrode in contrast to an unmodified electrode, demonstrating the enhanced electrochemical surface area of the BaO-MWCNT/MCPE. Additionally, the least charge transfer resistance and facile reaction catalysis for strong analyte interaction are the key factors in the fabrication of the sensor. The Nyquist plot and cyclic voltammograms provided evidence that the BaO-MWCNT/MCPE sensor has caused electrocatalytic oxidation of DIU. Thus, BaO-MWCNT composite material is a viable modifier in an electrochemical sensor. However, the study also evaluated the dearth of published studies on the electrochemical detection of other interfering species, such as amitrole, bentazone, and carbendazim, during real sample analysis. Furthermore, the sensor was efficiently utilized for the electrochemical DIU quantification in soil and water samples. These results emphasize the developed sensor to portray good selectivity, sensitivity, and reliability for DIU determinations.

Electrochemical activity of tungsten oxide doped carbon (WO3/C) catalyst for hydroquinone/benzoquinone redox flow battery

The research in organic flow batteries is emerging as the cost of the vanadium electrolyte limits the grid-scale application. Tungsten trioxide doped carbon (WO3/C) electrocatalyst is developed to examine its potential in hydroquinone - benzoquinone redox flow battery (HQ/BQ RFB). The catalyst is characterized by a field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR) and confirms the formation of active WO3/C electrocatalyst. The electrochemical activity of the synthesized WO3/C electrocatalyst is inspected by cyclic voltammetry (CV). It shows comparatively high anodic and cathodic peak currents, low charge transfer resistance, and relatively high electrokinetic reversibility. The charge–discharge test on single cell HQ/BQ RFB is conducted using pristine carbon paper (CP), and WO3/C coated carbon paper (WO3/C-CP). The columbic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) of the RFB using WO3/C-CP are around 90%, 75%, and 70%, respectively, which are significantly higher than the CP. The improvement in results demonstrates that the WO3/C electrocatalyst is better at providing active sites and improving the electrochemical reactions kinetics, thus suits the application of HQ/BQ RFB.

Composite Metal–Organic Framework-Derived NiCoP/MoS2 Heterostructure with Superior Electrocatalytic Credentials for Urea and Methanol Oxidation

The urea oxidation reaction (UOR) and methanol oxidation reaction (MOR) are the most practical alternative counter-reactions to the hydrogen evolution reaction in the overall electrochemical water splitting process. The thermodynamic gains in terms of lower water-splitting potentials compared to the oxygen evolution reaction (OER) can be cashed in if the kinetics of the UOR and MOR can suitably be controlled. This has called for the development of suitable cost-effective and non-precious catalysts for the processes. Herein, we report the synthesis of a heterostructured composite catalyst that incorporates the versatile NiCoP and MoS2 components through a composite MOF degradation route for efficient UOR and MOR catalysis in an alkaline medium (0.5 M NaOH). The intimate union of the components generates the strong synergistic influence of catalytically active phosphide and sulfide components toward excellent electrocatalytic UOR and MOR performance. The cyclic voltammetry and linear sweep voltammetry analyses reveal anodic UOR and MOR peak currents of 92.5 and 214.2 mA cm–2, respectively. Also, a benchmark current of 50 mA cm–2 is achieved at voltages of 1.55 and 1.53 V versus the reversible hydrogen electrode for the UOR and MOR, respectively, which reflects a considerable kinetic facility over the OER. The electrochemical impedance (EIS) measurements reveal considerably enhanced kinetics over the control samples and the OER on the catalyst systems. Additionally, the catalytic synergism is clearly reflected as the catalytic credentials of the composite catalysts surpass those of the individual control samples significantly. The catalytic features compare well with the best catalysts reported for the UOR and MOR in the alkaline medium.

Voltammetric analysis of luminescent markers in gunshot residues.

Currently, SEM-EDS is used to detect gunshot residue (GSR) from the presence of Ba, Pb, and Sb in the sample. However, the development of new nontoxic ammunition (NTA) has prevented conventional metals from being found. In this work, we aim to determine the presence of an inorganic luminescent chemical marker based on rare earth in gunshot residues using the technique of squarewave voltammetry (SWV). After firing, the luminescent complex [(Eu2 Zr)(btc)3 (Hbtc)0.5 .6H2 O], which is used as a chemical marker, can be detected under a UV lamp. An aqueous solution with 0.1mol L-1 KCl as supporting electrolyte can be easily collected on carbon paste electrode surfaces for SWV analysis A=100 mV, f=10Hz, and step potential of 5mV are required. The luminescent marker incorporated into the carbon paste electrode showed two anodic peak currents in the region of 0.4V (vs Ag/AgCl) and at 0.75 V (vs Ag/AgCl) and also a cathodic one in 0.4V (vs Ag/AgCl). SEM-EDS was able to analyze the same voltammetric results for conventional and nontoxic ammunition containing the luminescent marker. Therefore, voltammetry and SEM-EDS are valid for detecting the new residue marker in GSR. Despite this, the electrochemical method is still more advantageous because of its low cost and lack of expensive equipment and supplies in forensic laboratories.

Electrochemical sensor based on epoxy-functionalized BEA nanozeolite and graphene oxide modified glassy carbon electrode for bisphenol E determination

An epoxy-functionalized beta type nanozeolite (BEA)/graphene oxide nanocomposite modified glassy carbon electrode (GCE/BEA/APTMS/GA/GO/NF) has been created for the differential pulse voltammetric determination of bisphenol E (BPE). The modified electrode presented an enhanced current response in comparison with bare GCE. A linear dependence of anodic peak current (Ip) and scan rate (ν) was observed, which showed that the electrochemical process was adsorption-controlled. Differential pulse voltammetry (DPV) was employed and optimized for the sensitive determination of BPE. Under the optimized conditions, the anodic peak current was linearly proportional to BPE concentration in the range between 0.07 and 4.81 µM, with a correlation coefficient of 0.995 and limit of detection 0.056 μM (S/N = 3). The electrode showed good repeatability and storage stability, and a low response to interfering compounds. Comparison was made to the determination of bisphenol A. To confirm the electrode analytical performance, recovery tests were performed, and deviations lower than 10% were found. The BEA zeolite-GO nanocomposite proved to be a promising sensing platform for bisphenol determination.Graphical abstract