جستجوی مقالات مرتبط با کلیدواژه « Cyclic voltammetry » در نشریات گروه « علوم پایه »

Macrocyclic complexes play a crucial role in various emerging fields, including electrocatalysis, catalysis, sensor technology, pharmaceuticals, and biological applications. In this study, we synthesized a tetraaza-macrocyclic cavity capable of hosting transition metals, specifically MnII and NiII, forming the MnN4 and NiN4-macrocyclic complexes, respectively. Structural analyses were performed to propose the configuration of these complexes. Additionally, electrochemical studies were conducted to assess their redox potential and electron transfer kinetics. Furthermore, the biological activity of the complexes as antibacterial agents against a broad spectrum of microorganisms was investigated. The findings revealed that these complexes exhibit favorable redox properties with rapid electron transfer kinetics. The cyclic voltammogram was showed interesting results by eliminating ligand oxidation redox couple were observed as comparable in DMSO with shifting of 0.13 V peak potential in -ve peak potential range with the decreament in peak height. These results underscore the multifaceted applications of tetraaza-macrocyclic complexes in diverse fields, highlighting their importance in both fundamental research and practical biomedical interventions.

The aim of this research is to design an electrochemical sensor for the determination of mercury (II) (Hg2+) ions. A new compound 5-methoxy-2-({[4-(3-methyl-phenyl-cyclobutyl)-thiazol-2-yl]-hydrazone}-phenyl-methylene) (MTP) phenol as a substituent on glassy carbon (GC) electrode is reported. The electrochemical behaviors of the new compound were examined by cyclic voltammetry (CV) before characterization of the modified electrode by CV, electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and scanning electron microscopy (SEM) techniques. Determination of trace amounts of Hg2+ ions using a modified electrode was carried out using differential pulse voltammetry (DPV). To obtain optimized results, the effect of medium acidity and incubation time were investigated. The best results are pH 10.0 and incubation time (90 min), using Britton-Robinson (BR) buffer solution as the supporting electrolyte in all measurements. Under these optimal conditions, the oxidation peak current of Hg2+ ions exhibited a linear increase corresponding to concentrations ranging from 5.0 to 20.0 µM and 50.0 to 200.0 mM. Limit of detection (LOD) and limit of quantification (LOQ) are equal to 1.12 and 3.39 µM, respectively.

The pyrazole derivatives and its metal complexes are considered to be pharmacologically significant with a variety of pharmacological applications. The present investigation highlights the synthesis of pyrazole based novel ligand, 4-[(E)-(3-hydroxypyridin-2-yl)diazenyl]-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one (PDP) and its Co(II), Ni(II), Cu(II) complexes. The structure of the synthesized compounds has been evaluated using various physicochemical and spectroscopic techniques. Cyclic Voltammetry (CV) results are used to confirm the electrocatalytic ability of the modified electrode, [Co(PDP)2]Cl2.2H2O/GCE for the detection of Folic acid (FA) at different concentrations. The CV results displayed good electro-catalytic activity with 10-120 µML-1 with limits of detection (LOD) of 0.0666 µML-1. This electrode has a sensitivity of 2.8784 µAµM-1cm-2 for FA. The bio-efficacy of the synthesized ligand and its complexes have been evaluated against the bacteria (S.aures and E.coli) and fungal (A.flavus and P.anomala) strains using standard method. Antidiabetic study on two different enzymes, α- amylase and α-Glucosidase indicating excellent inhibition by the metal complexes having the maximum IC50 Value of 105.34 for α-amylase and 107.15 mg/mL for α- Glucosidase.

Deep brain stimulation (DBS) is a surgical procedure that involves implanting a medical device to send electrical signals to specific brain areas to improve movement disorder symptoms. There are many efforts to introduce closed-loop-based stimulation in DBS therapy, but most are in the experimental stages.  The current study is the characterization of a hybrid electrode for closed-loop control of the DBS adaptive stimulations. The electrode is fabricated as an interdigitated woven model and accommodates current steering stimulation and a sensing mechanism to provide input for the adaptive close loop system.  The study incorporates the identification of damaging effects of stimulation, estimation of safe charge injection limits which eliminate tissue damage, and estimation of safe charge injection limits to minimise electrode damage through electrochemical analyses, including Cyclic Voltammetry, Electrochemical Impedance spectroscopy, and Chronopotentiometry.  The study also addresses the development of an appropriate electrical equivalent model that could be employed in later analytical studies. The study has derived that for an electrode (ø1.3mm×1.5mm) to safeguard against physiological mass action-induced damage, the maximum permissible charge injection per phase during stimulation should be set to Qma=2.08 µC, corresponding to a charge density of 33.98 µC/cm2. In the case of the Pt-10Ir electrode (ø1.3mm×1.5mm), the safe charge injection threshold to prevent damage from electrochemical reactions is established at 4.1 µC (at a rate of 67 µC/cm2), surpassing Shannon's tissue-damaging limit of 2.08 µC (at 33.98 µC/cm2).

Dopamine (DA) is a vital neurotransmitter having key roles in regulating various biological functions in animals and the sensitive and selective monitoring of DA in biological fluid is of high significance. Herein, poly(1-naphthylamine)–graphene oxide (PNA-20GO) nanocomposite containing 20 % GO by weight obtained by the in-situ chemical oxidative polymerization of 1-naphthylamine in the presence of GO was utilized to develop an economical electrochemical sensor for DA by modifying Carbon Paste Electrode (CPE) with prepared PNA-20GO nanocomposite. The electrochemical characterization of the PNA and PNA-20GO was performed with Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopic (EIS) studies. The electrochemical response and charge transfer kinetics were significantly improved for the PNA-GO-modified CPE compared to PNA-modified CPE which was evidenced by the comparatively lower diameter of the semicircle region in the Nyquist plot obtained from EIS studies and better current response for the PNA-GO modified CPE than PNA modified or bare CPE in the corresponding CV curves. The enhanced electrochemical characteristics were credited to the increased surface area and synergistic charge transfer interactions between the PNA and GO. Furthermore, it was observed that PNA-GO modification could trigger the diffusion-controlled electrochemical oxidation of DA over CPE. The demonstrated PNA-GO modified DA sensor could show the linear current response for DA concentration ranging from 1-100 µM. The sensor exhibited high sensitivity (1094 µA/(mM.cm2)) with a low detection limit of 0.23 µM. The present DA sensor could exhibit acceptable stability and selectivity over common interfering molecules like creatine, ascorbic acid, and uric acid.

The microscopic arrangement of alloys has a significant influence on their electrical, thermal, mechanical, and catalytic properties. In this respect, we have developed nickel-cobalt alloy films by electrodeposition on an ITO glass substrate while examining nucleation and growth processes during the first steps of electrocrystallization. Energy Dispersive X-ray Spectroscopy (EDX) approved stoichiometry (1,1) of the alloy elaborated. X-ray diffraction (XRD) showed that the Co-Ni binary electrodeposited at different potentials crystallizes in a cubic structure that belongs to the Pm3̅m space group. From chronoamperometry and cyclic voltammetry curves, we concluded that the Co-Ni/ITO system is quasi-reversible, with diffusion of Ni2+ and Co2+ cations being the controlling step.  The ascending part of the current-time transients investigation has shown that the Ni-Co electrodeposition mechanism is characterized by instantaneous nucleation in line with 3D growth.  This result is confirmed by comparison of the experimental chronoamperometry data with the theoretical models of Scharifker and Hills on the one hand, and Bewick, Fleischmann, and Thirsk on the other.

Using a molecularly imprinted polymer (MIP) as a recognition element, a selective voltammetric sensor for ketoconazole (KC) was designed and constructed. MIP was synthesized using methacrylic acid as a functional monomer and KC as a template, and then into the carbon paste electrode as a ketoconazole sensor, was incorporated. A new chemically modified electrode containing MIP compound on the surface of a glassy carbon electrode (GCE) by sol-gel method was obtained. The electrochemical behavior of the resulting modified electrode by cyclic voltammetry method in detail was investigated. The obtained film electrode had very good stability and thus exhibited a good electrocatalytic response for KC oxidation. A sharp catalytic oxidation peak was observed at around 53 mV in the MIP/CCE electrode and GCE, and a small oxidation peaks current at about 63 mV was observed. The diffusion coefficient and transfer coefficient (α) for the electrocatalytic oxidation of KC were also studied under experimental conditions.

Determining the band edges of Quantum Dots (QDs) in electrolytes with different redox is still a serious challenge for many researchers. A new and innovative method to trace Valence Band (VB) and Conduction Band (CB) edges is Electron Exchange Magnitude (EEM) determination with logarithmic scaling in Cyclic Voltammetry (CV) curves. The EEM method is an adaptation of the Tafel method, which determines the equilibrium currents in the logarithmic scale in the potential current curves. Accordingly, the equilibrium currents on the surface of QDs can be related to the currents occurring at the band edges. Since the band gap varies with the size of the QDs, the shift of the band edges occurs as the size of the QDs changes. In this study, PbS QDs were deposited on ITO/ZnO by the SILAR method and considered as a photoanod. The band edges were investigated by EEM method in electrolytes with and without Sulfide polysulfide redox. In this way, the minimum value of EEM in the anodic and cathodic range was considered as the VB and CB edges, respectively. Investigations show that some results of this research are in good agreement with the observations and results of others in matters such as determining the PbS QDs bandgap, although there are significant differences in determining the exact position of the band edges.

A lactate biosensor has been designed for the detection of lactate in a real sample. A combination of composite material comprising of multi-walled carbon nanotubes (MWCNTs) and zinc oxide nanoparticles has been used as working electrode, which were deposited on gold (Au) wire. This was treated as working electrode for the preparation of a LDH-based amperometric biosensor along with acetyl coenzyme, which acts as the mediator to enhance electron transportation. The biosensor showed excellent results in terms of stability, response time, and sensitivity. The sensitivity of the biosensor is 4.487 mA/µM and its linearity is between 10 µM and 100 µM. The biosensor has a 0.67 µM limit of detection with a response time of 8 sec. The optimal temperature is 35°C, and the optimal pH is 8. All the results confirmed that the ZnO/MWCNTs/Au electrode, along with acetyl coenzyme, acts as a suitable matrix for the purpose of immobilizing LDH enzymes for the formation of lactate biosensors.

This paper covers the synthesis and characterization of tetraamino Zinc(II) metallophthalocyanine (Zn(II)TAPc) using spectroscopic and electrochemical techniques. The electrochemical determination of dopamine (DA), ascorbic acid (AA) and uric acid (UA) was investigated using composite modified MWCNT-Zn(II)TAPc/GCE, due to their excellent conductivity, electrons transfer ability compared to the bare glassy carbon electrode (GCE), and because the charge transfer rate increases with multiwalled carbon nano tubes (MWCNT) on the surface of GCE. As a result, electrochemical sensing of bioanalytes was investigated on MWCNT-Zn(II)TAPc/GCE, and the analytical profile of micro molar concentration (µM) of DA is in the linear range of 0.1 to 1.1 µML-1 with LOD is 0.033µML-1, sensitivity of 14.063 µAµML-1 and the electro analytical sensing of AA and UA while using modified composite electrode for AA the linear range of 0.2-0.7 μmol L−1, LOD of 0.066μmol L−1 and sensitivity  54.821 μAμM−1 cm−2, for UA the linear range of 0.05–1.2 μmolL−1, lower detection limit of 0.066 μmolL−1 and sensitivity of 0.515 μAμM−1 cm−2, The MWCNT-Zn(II)TAPc/GCE shows good repeatability, stability and reproducibility.

In this research, a Glassy Carbon Electrode (GCE) was modified with glucose oxidase (GOx)/chitosan (CS)/Graphene Oxide (GO) nanofibers for the detection of glucose via the electrospinning method. To do this, GOx was trapped among the two CS/GO nanofibers layers. Concerning electrochemical properties and producing conditions, the optimum amounts for GOx and GO in the deposited layer were 20 mg/mL and 20 % w/w, respectively. An investigation on the effects of pH, time of oxygen dissolving in the test solution, and scan rate on electrochemical behavior revealed that the peak current increased with increasing the oxygen dissolving time up to 20 min and scan rate values. However, the redox processes showed more symmetric anodic and cathodic structures at slow scan rates. Also, the highest current was obtained at a pH of 7.4. The result showed that the electrochemical process of GOx occurs through a two-proton and two-electron transformation. Additionally, the sensor exhibited excellent reproducibility and stability properties. It was concluded that the use of nanofibrous structure and the immobilization of the glucose oxidase among the two CS/GO nanofibers layers enhanced the electrochemical properties significantly due to the penetration of water-soluble glucose molecules in the porous nanofiber layers, which helped efficiently catalyze the oxidation of glucose and facile direct electron transfer for GOx. The resultant modified electrodes exhibited a high sensitivity of 1006.86 μA/mMcm2 and a low detection limit of 0.02 mM with a wide linear range of 0.05–20 mM.

Mill scale is a by-product of hot rolling steel generated in a rolling mill and has the potential to be transformed into hematite. Owing to hematite's many uses; mill scale has a high economic value and may be used as a battery anode. The impact of CaCO3 pellet quantity and calcination time on hematite purity, as well as the effect of deposition duration and voltage on coating thickness. The calcination duration has a considerable effect on the purity of the resulting hematite, while the addition of CaCO3 pellets lowered the purity by around 6%. Attaining the thickest hematite coating on an aluminium surface required a 40 V treatment and a deposition time of 30 minutes. Alternately arranged aluminium ions (Al3+) and oxide ions (O2-) form an ionic connection. Whereas aluminium ions on the surface of aluminium are positively charged, oxide ions are negatively charged in order to generate an electrostatic interaction. During the discharge phase, the voltage decreased from 1.02 to 0.70 V. This research contributes to the development of more efficient and effective manufacturing procedures for hematite and its battery anode applications.

Electrochemical methods have become increasingly popular in the pharmaceutical and drug analysis sectors due to their numerous benefits, such as high sensitivity, selectivity, and specificity. Electrochemical-based nanomaterials are adjustable and can be influenced by the type of electrode used and the applied potential. Electroanalytical methods have proven to be a useful analytical technology that has seen increased utility in the pharmaceutical business in recent years. In the last five years, there have been significant developments in the synthesis and use of novel electrochemical sensors in drug analysis. These developments have been driven by advancements in instrumentation and an increased understanding of electrochemical methods. This review concludes the current state-of-the-art in electrochemical sensors for pharmaceutical analysis and future perspectives in this field. We highlight the need for more standardized methods for the determination of biologically important compounds such as dopamine, guanine, adenine, and uric acid using electrochemical sensors and the development of multiplexed sensors for simultaneous analysis of multiple drugs.

The effect of Pd nanoparticles geometry has been studied on modifying Fc and Fc-COOH-based electrodes. It has been found to have more reliable results before and after Pd use with Fc-COOH modified electrode. The sensing activity has been performed for ascorbic acid and found quite good results with Fc-COOH-based electrode and surprising results with Pd-modified Fc and Fc-COOH-based electrode, which is further confirmed by performing amperometry titration and observed much high current in case of PdNPs modified Fc-COOH based electrode. The rise in anodic peak current from 14.5A to 33.01A and 1.30A to 3.63 A for Fc and Fc-COOH modified electrodes under a similar environment. The current function continuously rises from 10 to 16A/(mV)0.5 and 6.5 to 13.4A/(mV)0.5. The Rct value decreases from 12.8 k to 1.9 k and 8.3 k to 1.5 krespectively. Electrochemical impedance spectroscopy has also been studied, confirming that PdNPs modified Fc and Fc-COOH-based electrodes having low Rct value, the faster charge transfer is compassionate toward ascorbic acid. Transmission electron microscopy, PXRD, and CV have all been used to characterize the nanomaterial with the following major investigation:(i) The average size of PdNPs1&PdNPs2 is found 18nm & 8nm, (ii) It has been discovered that the palladium content influences both the electrocatalytic effectiveness of novel modified electrode materials and the oxidoreduction electrochemistry of ferrocene and Fc-COOH, and(iii) The modified electrode has an extremely low detection limit for ascorbic acid of < 5 μM

This article reports a detailed report of the synthesis and depiction of iron oxide nanomaterials (FeONPs) and their electroanalytical application. Electrochemical examination of Guanine (GU) and Dopamine (DA) is performed by synthesized iron oxide nanoparticles modified with carbon paste electrode (CPE) using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques. Peak potential of GU along with DA at FeOMCPE are 0.76 and 0.14V respectively. A good linear response was obtained by CV of GU and DA, in the concentration ranges 10-70 and10-70 μM respectively and the LOD value for GU along with DA was observed to be 5.3 and 4.6 μM. The result shows that the FeOMCPE exhibited good analytical performance and high electro-catalytic activity of DA and GU.

The present study aims to introduce a highly sensitive electrochemical sensor for quantification of trace amounts of Sumatriptan (SUM) in biological fluids. To immobilize a stable nano film of β-cyclodextrin (β-CD) on a glassy carbon electrode (GCE), electropolymerization of monomer was carried out within 0.1 M phosphate buffer with pH 6.0 utilizing cyclic voltammetry to yield polymerized β-CD (pβ-CD). The morphological characterization of pβ-CD/GCE was examined by Field emission scanning electron microscopy (FESEM). The electrochemical redox action of SUM on pβ-CD/GCE was scrutiny studied by cyclic voltammetry and chronocoulometry. The electrochemical parameters including the electron transfer coefficient (α), the standard heterogeneous rate constant (ks), the surface area of the electrode (A), the electron transfer number (n), and the surface coverage (Γ) were estimated to be 0.38, 1.23×10-3 cm s-1, 0.06 cm2, 1, 1.07×10-8 mol cm-2, respectively. At optimized criteria, a substantial enhancement was attained toward the electrooxidation of SUM on the developed electrode compared to the bare GCE, resulting in wide linear ranges of 0.0622.47µM and 2.4752.1µM with a low detection limit of 27 nM. The developed sensor was successfully employed for quantification of SUM in human blood serum and urine samples with good selectivity and acceptable recoveries, proving its utility for further applications as a sensitive and reliable sensor.

A novel electrochemical immunoelectrode was fabricated for Serum Amyloid A protein (SAA) sensing using gold nanoparticles modified electrode. The present study reports the optimisation of electrochemical deposition parameters for gold nanoparticles (AuNPs) on ITO (Indium-tin-oxide) surface. AuNPs were electrochemically deposited on APTES (3-Aminopropyl) triethoxysilane) modified ITO surface to prepare working electrode (AuNP/APTES/ITO). This electrode is further used to fabricate immunoelectrode SAA-Ab/AuNP/APTES/ITO by immobilising SAA specific antibodies (SAA ½ Ab) on its surface. Characterization of prepared immunoelectrode is done by electrochemical characterization techniques (differential pulse voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy), scanning electron microscopy and XRD. Sensing by electrochemical techniques revealed that fabricated immunoelectrode can detect SAA when 10 μl of it (from initial concentration of 10 fg/ml to 105 fg/ml) is poured on immunoelectrode and kept for 10 minutes every time. Linearity equation is obtained with lowest used concentration of SAA biomarker 10 fg/ml and the limit of detection (LOD) has been calculated using the equation 3σ/sensitivity which comes out to be 6.867 fg/ml.

In this paper, phenol was determined in a liquid solution based on fabricating a phenol-selective electrode by cyclic voltammetry (CV). The carbon pa s te electrode was modified with nickel oxide nanoparticles (NiO) which were doped with nitrogen carbon quantum dots (NCQD) as the NiO-NCQD nanocomposite. The modified carbon pa s te electrode was manufactured in a laboratory and the effect of pH was s tudied. In the optimized condition, the be s t results were created at pH 7.0 and 4.0 using KH2PO4 buffer solution. By voltammetry, the voltage was optimized, and the be s t value for the voltages was obtained at 0.04166V and 0.05991V for pH 4 and 7, respectively. The scan rate (SR) was s tudied and the be s t SR was achieved at 100 mv s-1 for both pH. Due to the results, a wide linear dynamic range between 10 to 1000 μM was obtained. Also, the s tandard phenol solution was analyzed by high-performance liquid chromatography (HPLC). The retention time (RT), the wavelength maximum (λ max: nm), and the peak area equation of HPLC were achieved at 2.982 min, 270 nm, and (Area=40420CPhenol+ 43.557), respectively by the concentration range of 0.1-5.0 mg L-1. The modified carbon pa s te electrode with NiO-NCQD was used for determining phenol by cyclic voltammetry and compared with the HPLC technique. The results showed that there was no significant difference between the two methods.

In the present work, the BiVO4 nanoparticles (BiVO4/NPs) were synthesized using the co-precipitation method and characterized by the X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) techniques. The BiVO4/NPs were utilized as electrode modifiers with carbon paste electrode (BiVO4/MCPE), and the as-prepared modified electrode surface was pretreated with NaOH (BiVO4/NaOH/MCPE). The pretreated modified electrode was used for the simultaneous determination of acetaminophen (ACOP) and adrenaline (AD) by using cyclic voltammetry (CV) and differential pulse voltammetric (DPV) techniques. The influence of variation of concentration of ACOP and AD was investigated at BiVO4/NaOH/MCPE. The limit of detection (LOD) and limit of quantification (LOQ) of both ACOP and AD at BiVO4/NaOH/MCPE, respectively were determined, the LOD was found to be 3.3 µM for ACOP and 5.9 μM for AD, and LOQ was found to be 11.1 µM for ACOP and 17.8 μM for AD, respectively. Moreover, the BiVO4/NaOH/MCPE is used for the sensitive and selective determination of ACOP and AD in real samples.