Effect Of Scan Rate Research Articles

Activated carbon based paste electrodes for the simultaneous and effective detection of divalent cadmium and lead ions in wastewater

ABSTRACT Heavy metals (HM) have gained significant attention in terms of regular monitoring and detection owing to their toxicity, non-biodegradability, and persistence. Current techniques for detecting HM are expensive, cumbersome, and require sophisticated instruments and skilled labour. Hence, developing cheap, rapid, energy-efficient, and accurate sensors is imperative and electrochemical techniques have emerged as promising tools. The current study involves the fabrication of an electrochemical sensor for the concurrent detection of lead (Pb2+) and cadmium (Cd2+) ions using modified carbon paste electrodes (mCPE). Activated carbon (AC) with a BET surface area of 1118 m2 g−1 was obtained by chemical activation and thermal treatment of the waste rubberwood sawdust. AC-Graphite, AC-Reduced Graphene Oxide (RGO), and AC-RGO-Chitosan were the types of mCPEs that were utilised. The electrochemical behaviours and effects of pH, concentration, and scan rate were studied using Cyclic voltammetry (CV). Studies on detection were conducted using CV and linear sweep voltammetry. Although all the 3 mCPEs detected Cd2+ and Pb2+ in the simulated wastewater, the CPE with RGO and AC could detect Cd2+ as low as 10.91 µg L−1 and Pb2+ as low as 14.01 µg L−1. The work explored the possibility of using AC as a potential sustainable substitute for graphite in CPE.

Voltammetric determination of daclatasvir dihydrochloride at bimetallic Ag/Co nanoparticles modified carbon paste electrode

In this work, a sensitive and cost-effective voltammetric method was proposed for the determination of daclatasvir dihydrochloride (DAC.2HCl) at a bimetallic Ag/Co nanoparticles-modified carbon paste electrode. Potential cyclization was used for the electro-deposition of the nanoparticles. The number of potential cycles needed for deposition was optimized. Surface characterization of the prepared sensor was performed using scanning electron microscope imaging (SEM). The electroanalysis of DAC was performed using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Results of the scan rate effect indicated a dual diffusion-adsorption mechanism of DAC electrooxidation that involved two electrons. A very wide concentration range, from 5 × 10−9 to 10−4 M, was detected and divided into two segments with a low detection limit of 0.387 nM in 0.1 M phosphate buffer solution/pH 2.6. The electroactivity of the developed sensor toward DAC, sensitivity, reproducibility, repeatability, robustness, and selectivity were investigated. This sensor was successfully applied for the determination of DAC in pharmaceutical and urine samples.

Modified Ultra Micro-Carbon Electrode for Efficient Ammonia Sensing for Water Quality Assessment.

Ammonia is one of the most prominent and hazardous water pollutants; hence its selective and sensitive detection in water is crucial for monitoring water quality and determining its usability. In the present work, a simple, cost-effective electrochemical sensor for the detection of ammonia is presented. Multi-walled carbon nanotubes modified ultra-micro-carbon thread electrode (UME/MWCNT) has been realized. The electro-catalytic activity of ammonia is studied by voltammetry and amperometry techniques and the results are presented. The microscopic characterization of UME/MWCNT for surface morphology analysis was also carried out. Further, the UME/MWCNT based electrochemical sensor was tested for its practical application by exploring various parameters like the effect of scan rate, pH and interference from co-existing bio-chemicals like nitrate, nitrite, phosphate, hydrazine, H2 [Formula: see text] uric acid, ascorbic acid and dopamine along with real sample analysis. The developed sensor can efficiently detect ammonia in a linear range of [Formula: see text] to 1 mM which is well within the permissible safe drinking water limit. The limit of detection (LoD) and limit of quantification (LoQ) obtained for the developed sensor were [Formula: see text] and [Formula: see text] respectively. The negligible interference, good reproducibility, and appreciable recovery values indicated the potential of the developed UME for real-time ammonia detection. As a flexible electrode, UME can be further modified and fabricated as a microfluidic or a miniaturized device for a portable electrochemical sensing platform in future.

Laser-treatment-induced surface integrity modifications of stainless steel

Scanning of a high-power laser beam on the surface of martensitic stainless steel (SS420) has been studied, addressing the effect of scanning rate V on integrity modifications in the near-surface regions. Structural, compositional, and crystallographic characterizations revealed the presence of ablations, surface melting/resolidification, surface oxidations, and austenite (γ-phase) precipitations when V ≤ 20 mm s−1. Melt pool (MP), heat affected zone (HAZ), and base material have been clearly distinguished at the cross-section of the slow-scanned samples. Adjacent MPs partially overlapped when V = 5 mm s−1. The γ-phase precipitations solely occurred in the MPs, i.e., of ∼ 400 μm deep for V = 5 mm s−1, while oxidations dominantly occurred in the surface regions of shallower than ∼30 μm within the MPs. Compositional analysis revealed increased Cr-, Mn-, and Si-to-Fe ratios at the laser-scanned surface but without variations along the surface normal direction. The enhanced surface hardness has been achieved up to 805 HV, and the hardness monotonically decreased when moving deeper (i.e., ∼1000 μm) into the base material. These observations shed new light on surface engineering of metallic alloys via laser-based direct energy treatments.

Electrochemical Characterisation and Confirmation of Antioxidative Properties of Ivermectin in Biological Medium.

Ivermectin (IVM) is a drug from the group of anthelmintics used in veterinary and human medicine. Recently, interest in IVM has increased as it has been used for the treatment of some malignant diseases, as well as viral infections caused by the Zika virus, HIV-1 and SARS-CoV-2. The electrochemical behaviour of IVM was investigated using cyclic (CV), differential pulse (DPV) and square wave voltammetry (SWV) at glassy carbon electrode (GCE). IVM showed independent oxidation and reduction processes. The effect of pH and scan rate indicated the irreversibility of all processes and confirmed the diffusion character of oxidation and reduction as an adsorption-controlled process. Mechanisms for IVM oxidation at the tetrahydrofuran ring and reduction of the 1,4-diene structure in the IVM molecule are proposed. The redox behaviour of IVM in a biological matrix (human serum pool) showed a pronounced antioxidant potential similar to that of Trolox during short incubation, whereas a prolonged stay among biomolecules and in the presence of an exogenous pro-oxidant (tert-butyl hydroperoxide, TBH) resulted in a loss of its antioxidant effect. The antioxidant potential of IVM was confirmed by voltametric methodology which is proposed for the first time.

Highly sensitive electrochemical sensor based on carbon paste electrode modified with graphene nanoribbon-CoFe2O4@NiO and ionic liquid for azithromycin antibiotic monitoring in biological and pharmaceutical samples.

In this report, Azithromycin (Azi) antibiotic was measured by carbon paste electrode (CPE) improved by graphene nanoribbon-CoFe2O4@NiO nanocomposite and 1-hexyl-3 methylimidazolium hexafluorophosphate (HMIM PF6) as an ionic liquid binder. The electrochemical behavior of Azi on the graphene nanoribbon-CoFe2O4@NiO/HMIM PF6/CPE is investigated by voltammetric methods, and the results showed that the modifiers improve the conductivity and electrochemical activity of the CPE. According to obtained data, the electrochemical behavior of Azi is related to pH. under optimum conditions, the sensor has linear ranges from 10µM to 2mM with a LOD of 0.66µM. The effect of scan rate and chronoamperometry were studied, which showed that the Azi electro-oxidation is diffusion controlled with the diffusion coefficient of 9.22 × 10-6 cm2/s. The reproducibility (3.15%), repeatability (2.5%), selectivity, and stability (for 30days) tests were investigated, which results were acceptable. The actual sample analysis confirmed that the proposed sensor is an appropriate electrochemical tool for Azi determination in urine and Azi capsule.

Impact of boron doping on microporous carbon for enhancing the electrochemical sensitivity of vitamin D3

Vitamin D deficiency is becoming a severe burden worldwide, the rapid lifestyle changes are an important cause of that. As a result, rapid, cost-effective, and discriminating sensors for the determination of vitamin D are highly required. Herein, we report, a non-enzymatic sensitive electrochemical method for the determination of vitamin D3 using boron-doped microporous carbon (BMC) as a sensing matrix. The Boron was systematically integrated into the microporous carbon (MC) matrix to increase the electrochemical property. Among the synthesized materials, the MC modified with 5 wt.% boron showed better sensor performance than the others. The kinetics and concentration studies indicate that the rate of electro oxidation on the surface of the modified electrode is significantly faster than that of the unmodified electrode. The scan rate effect and pH studies provide the number of electron transfers, transfer coefficient, and diffusion coefficient of vitamin D3 which are 2, 0.52, and 18.49x10–12 cm2s-1, respectively. The electrolytic pH had a large impact on the oxidation potential, and its activity was significantly closer to that of the previously reported boron-doped diamond electrode. The BMC-5 modified electrode has a great linear range (0.5 μM–42 μM) and a low detection limit (1.45 μM). Hence, from this study, it is concluded that the low-cost and stable BMC is an alternate matrix for the determination of vitamin D3.

Electrochemical deposition of Ag nanoparticles on ITO-coated glass: effect of different cyclic voltammetry scan rates on Ag deposition

This work aims to investigate the effect of different cyclic voltammetry scan rates on silver nanoparticles deposition on ITO-coated glass aiming to obtain improve its optical and electrical properties. The deposition was evaluated using different physical, chemical and optical characterization techniques, such as SEM, XRD, FTIR, UV–visible and electrochemical tests. Cyclic voltammetry was used to measure the Ag deposition at two different scan rates (20 CV at 10 mV/s and 100 CV at 30 mV/s). The characterization results have confirmed the formation of a homogeneous crystal layer of silver on ITO, which exhibited high transmittance in the visible light region. According to the cyclic voltammetry measurements, the outer spheres of the Ag NPs associated with the redox reaction illustrate the typical reduction and oxidation waves of Ag in the range of (−100 to +700) mV. The quantification using Cyclic voltammetry measurements has shown that the Ag nanoparticles deposition on ITO thin films are inversely proportional to the scan rates; in other words, higher deposition is obtained at lower scan rates.

Exploring the linear relationship between potential dynamics and interfacial capacitance: implications for enhancing the turnover frequency in electrochemical water splitting

Effect of scan rate over intrinsic activity or TOF for OER, has been analysed for the very first time. It has found that increased TOF value varies as a function of scan rate which arises due to increased interfacial capacitance.

Polymer modified carbon paste electrode for the electrochemical analysis of Tartrazine

The tartrazine (TZ) analysis is useful for both environment and health. In the present work, a electrode was fabricated for the determination of TZ by electro-polymerization of niacin on the electrode surface. For this purpose, fabrication of poly (niacin) modified carbon paste electrode (PNMCPE) was done using phosphate buffer solution (PBS) of 0.2 M at pH 7.0. Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS), and Field emission scanning electron microscopy (FE-SEM) methods were used to study the electrochemical responce and surface morphology of the PNMCPE and bare carbon paste electrode (BCPE) materials. Various parameters such as effect of scan rate, active surface area, material conductivity and resistivity, detection limit, and effect of pH were analyzed in 0.6 to 1.1 V of potential range using 0.2 M PBS as a supporting electrolyte. The electrochemical oxidation of TZ was analyzed in presence of different interfering ions and organic compounds on the electrode surface. The obtained values of limit of detection (LOD) and limit of quantification (LOQ) for TZ are found to be 0.1246 µM and 0.4155 µM, respectively. Furthermore, the fabricated electrode was used to analyze TZ in food sample to confirm its analytical application.

Development of manganese oxide nanoparticles based chemical sensor for sensitive determination of an antiviral drug valaciclovir

The electrochemical analysis of valaciclovir (VAL) was carried out by electro-deposition of manganese oxide nanoparticles on glassy carbon electrode (MnO2/GCE). The surface morphology of prepared sensor material was analysed by scanning electron microscopy (SEM). Effects of scan rate, solution pH, and concentration variation on the electrochemical behaviour of VAL were studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The increase in anodic current by the use of a modified electrode (5.76 μA) compared with the peak current of bare GCE (1.18 μA) confirms the enhancement of the surface area and catalytic property of manganese oxide nanoparticles. A linear response in the concentration of VAL was observed by DPV from 1.0 × 10−8 M to 14.0 × 10−6 M at the sensor. The limit of detection and quantification were found to be 0.95 nM and 3.17 nM, respectively. The real-world application of the sensor was validated by applying for pharmaceutical and real sample analysis. Thus, it has been proved that the proposed electrochemical sensor has a strong potential to be employed in quality control laboratories for the testing of pharmaceutical products.

Comparison of carbon paste and boron-doped diamond electrodes for determination of cefepime in pharmaceutical dosage forms and biological samples

The electrochemical analysis of cefepime, a fourth-generation cephalosporin, was investigated in the direction of oxidation using a carbon paste (CP) electrode and a boron-doped diamond (BDD) electrode. The optimum paste composition was determined as 25 % mineral oil-75 % graphite powder for the CP electrode. The effects of different pHs and scan rates on the anodic peak potential and peak current of cefepime were investigated. Scan rate studies were carried out in the range of 5–200 mV s −1 (vs. Ag/AgCl). It was found that the CP electrode had an adsorption-controlled process and the BDD electrode had a diffusion-controlled process under some adsorption effect. The linear ranges of cefepime obtained for the CP electrode were determined as 0.08–10 μM (correlation coefficient; r = 0.998) for differential pulse stripping voltammetry with a detection limit of 3.73 nM and 0.4–10 μM ( r = 0.998) for square wave stripping voltammetry with a detection limit of 22.1 nM. For the BDD electrode, cefepime gave a linear range of 0.04–10 μM ( r = 0.999) for differential pulse voltammetry with a detection limit of 1.58 nM and 0.4–60 μM ( r = 0.998) for square wave voltammetry with a detection limit 11.0 nM. The precision of the proposed methods was examined by repeatability studies and presented by relative standard deviation (RSD) values below 1.76 %. Quantitative analysis of cefepime from pharmaceutical dosage forms and human serum samples using the developed methods was performed for both electrodes without any separation or filtering pretreatment. Recoveries were between 99.41 and 102.07 % for pharmaceutical dosage forms and between 99.79 and 100.50 % for human serum samples, with RSD ranging from 0.70 % to 0.98 %. • Sensitive detection of cefepime helps to increase the effectiveness of treatment. • Side effects in the treatment can be reduced by the determination of cefepime. • Oxidative determination of cefepime can be done using non-toxic solid electrodes. • Carbon paste and boron doped diamond electrodes offer advantages over each other. • Voltammetric methods enable determination from serum samples without pretreatment.

Design and manufacture of a customized, large-size and high-strength bioactive HA osteoid composite ceramic by stereolithography

Stereolithography (SLA) ceramic printing is still a challenge to establish the adaptability between printing parameters and curing properties, and to meet large-size, high mechanical and good biological properties through structural optimization. In this study, a 3D printed ceramic scaffold with a customized, large-size and high-strength bioactive osteoid structure was achieved by SLA. The interaction effects of laser power, spot spacing, and scanning rate on the curing behaviour of HA slurry were investigated. Next, a compact shell/porous core with different volume ratios was fabricated to meet the requirement of high mechanical strength for load-bearing parts by SLA. Finally, the effect of different microchannel structural units on vascularization was explored based on a modelling algorithm. In conclusion, HA composite scaffolds with large-size, high strength and excellent biological properties were developed by using SLA ceramic printing technology. High strength and structure suitable for blood vessel growth provide a basis for bioceramic repair of large bone defects.

Ambiguities and best practices in the determination of active sites and real surface area of monometallic electrocatalytic interfaces

Determining the number of electrocatalytically accessible sites (ECAS) and real surface area (RSA) for any given electrocatalyst precisely is important in energy conversion electrocatalysis as these are directly used in the determination of intrinsic activity markers. For monometallic electrocatalysts and electrocatalysts of just one type of active site, there believed to be ways of making precise determination of ECAS and RSA using underpotential deposition (UPD), stripping, and redox-charge integration employing transient voltammetric sweeping techniques. This transient nature of sweeping techniques makes the determination of ECAS and RSA relatively less reliable. This study is directed at examining the effects of scan rate in the determination of ECAS and RSA taking Ni(OH)2/CC and Pt wire as model catalytic electrodes. The results suggest that the scan rate and the determined ECAS and RSA values are inversely related and the lowest possible scan rate set experiment was witnessed to give the highest possible ECAS or RSA values with LSV/CV.

One-dimensional conductive Ni3(HHTP)2 @ woven fabrics with controlled engineering design towards high-efficiency EDL electrodes

In this work, one-dimensional (1D) conductive MOFs Ni3(HHTP)2 with nanorod-like morphology on the surface of a woven fabric was synthesized by an in-situ growth method. Based on a three-electrode system, the effects of substrate concentration, scan rate and current density on electrode properties were investigated, respectively. The results showed that Ni3(HHTP)2 @ woven fabric-3 (NHWF-3) demonstrated the largest area capacitance at 5 mV s−1 and reached up to 360 μF cm−2 at 20 μA cm−2. Most importantly, the material still maintained 58.3% (210 μF cm−2) of the initially areal specific capacitance when the current density was increased 5 times to 100 μA cm−2. According to the electrochemical impedance spectroscopy (EIS) curve, NHWF-3 has the smallest semicircle radius in the high-frequency region, indicating that it has the lowest internal transfer resistance and the best conductivity. Thus, this study provides a good example for the simple preparation and practical applications of conductive MOFs composites.

Evaluation of the electrochemical response of Saccharomyces cerevisiae using screen-printed carbon electrodes (SPCE) modified with oxidized multi-walled carbon nanotubes dispersed in water – Nafion®

The evaluation of the electrochemical determination of Saccharomyces cerevisiae was carried out using a screen-printed carbon electrode (SPCE) modified with Nafion-dispersed oxidized multi-walled carbon nanotubes (OMWCNT). The morphology was studied using scanning electron microscopy (SEM), showing a complete modification of the surface with the nanotubes and yeast interaction with them instead of the graphite surface. The redox couple Fe(CN)64−/Fe(CN)63− was used to determine the electroactive area, the heterogeneous transfer constant, and the Nafion® effect. Results showed increases in electroactive area and heterogeneous transfer constant of 146% and 20.4%, respectively, due to the presence of nanotubes. Studies of the Nafion® effect showed that the polymeric membrane affects the electroactive area but not the heterogeneous transfer constant. Studies of the scan rate effect show that yeast oxidation is an irreversible mixed control process. As the concentration and scan rate increased, the anodic potential shifted toward more anodic values. The relationship between yeast concentration and the anodic current density (current/electroactive area) of yeast showed a linear range between 0.61 and 7.69 g L−1, the limit of detection (LOD) and the limit of quantification (LOQ) were 0.17 g L−1, and 0.61 g L−1, respectively, and the sensibility obtained was 0.03 μA L g−1 mm−2. These results show that with the screen-printed carbon electrodes it is possible to improve the electrochemical determination of this microorganism, enhancing the analytical parameters and quantification, allowing greater portability and decreasing measurement times and associated waste.

TO THE PROBLEM ON THE OXIDATION MECHANISM OF AZO DYES ON MODIFIED CARBON-PASTE ELECTRODES

In the current study, using a carbon-paste electrode modified with β-cyclodextrin oligosaccharide, the oxidation mechanism of some useful food azo dyes as Sunset Yellow FCF, Tartrazine, Allura Red AC, Carmoisine, Ponceau 4R was established. Cyclic voltammetry was used to investigation redox behaviour of studied food azo dyes (Sunset Yellow FCF, Tartrazine, Allura Red AC, Carmoisine, Ponceau 4R). It was established that such dyes as Sunset Yellow FCF and Ponceau 4R are oxidized quasi-reversibly, and such as Tartrazine, Carmoisine and Allura Red AC are completely irreversibly oxidized. It was noted that for all dyes, except Tartrazine, after oxidation on a cyclic voltammogram, a new reversibly redox pair is formed. This may indicate the formation of new electroactive fragments during the oxidation of azo dyes (Sunset Yellow FCF, Allura Red AC, Carmoisine, Ponceau 4R). Based on the conducted studies of the effect of pH and scanning rate on the oxidation potential of studied azo dyes, it was established that 2 electrons and 1 proton participate in the oxidation process for all dyes, except for Carmoisine, for which oxidation takes place with the participation of 1 proton and 1 electron. Based on the obtained information, as well as using information from our previous studies on the redox behavior of azo dyes (Sunset Yellow FCF, Tartrazine, Allura Red AC, Carmoisine, Ponceau 4R) on carbon-paste electrode modified by silica impregnated with cetylpyridinium chloride cationic surfactant, a scheme for the oxidation of azo dyes was proposed. According to the scheme, oxidation takes place with the participation of an irreversible chemical reaction, which leads to the further rearrangement of bonds with the breaking of the azo group of dyes and the formation of new electroactive fragments.

Synthesis and Characterization of High Entropy Alloy 23Fe-21Cr-18Ni-20Ti-18Mn for Electrochemical Sensor Applications.

High entropy alloys (HEA) are one of the modern-era alloys accelerating with greater velocity because of their excellent properties and different applications. In the present paper, we have successfully fabricated HEA (23Fe-21Cr-18Ni-20Ti-18Mn) powders by ball milling the elemental Fe, Cr, Ni, Ti, and Mn powders for 15 h. The advancement of the milling process and phase transformation of HEAs were studied by using X-ray diffraction (XRD) and scanning electron microscope (SEM). The crystallite size and the lattice strain of the HEA were calculated by using the Williamson-Hall (W-H) equation and the values were found to be 7 nm and 0.0176%, respectively. Similarly, the true lattice parameter was calculated using the Nelson-Riley (N-R) extrapolation method, and the value was found to be 3.544 Å. We have successfully investigated the electrochemical response of 15 h ball milled 23Fe-21Cr-18Ni-20Ti-18Mn HEA powders to determine the ascorbic acid (AA) using cyclic voltammetry. We have modified the carbon paste electrode with ball milled HEA of concentrations 0, 2, 4, 6, 8, and 10 mg, and among them, 8 mg HEA modified carbon paste electrode (HEA-MCPE) depicted the highest current sensitivity. We reported the effect of modifier concentration, analyte concentration, scan rate, and pH on the oxidation peak of AA. The electrochemical active surface area of carbon paste and MCPE was calculated using the Nernst equation and the values were found to be 0.0014 cm2 and 0.0027 cm2, respectively. The fabricated HEA-MCPE showed excellent current sensitivity, stability, anti-fouling, and selectivity.

Green synthesis approach to produce TiO2/rGO nanocomposite as voltammetric sensor for monitoring trace level bisphenol-A

The detection of trace level bisphenol-A (BPA) in plasticware has been successfully performed using a novel green-TiO2/rGO which was studied using electrochemical process. The green-TiO2/rGO was synthesized through green technique via one-pot synthesis using green-tea extract. The synthesized green-TiO2/rGO as sensors was characterized by fourier transform infra-Red (FTIR), X-ray Diffraction (XRD), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), and transmission electron microscopy (TEM). SEM image revealed that TiO2 successfully grew on rGO sheets in nanoscale (∼112 nm) with crystallite size of ∼7 nm from XRD diffractogram calculation. Then, the electrochemical activity was measured by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in a 0.01 M [Fe(CN)6]3–/4– in 0.1 M NaCl. The composition, pH, and scan rate effects were investigated for the optimum electrochemical process. TiO2/rGO modified CPE showed good linearity, repeatability, and accuracy with the LOD of 0.08 µM and the linearity range of 1–200 µM. The performance of the voltammetry method was very excellent a resulting similar amount of BPA detection in the actual samples compared with HPLC technique with the recovery range (%) of 98.99 ± 0.52 to 102.95 ± 1.18.

Effects of Laser Scanning Rate and Ti Content on Wear of Novel Fe-Cr-B-Al-Ti Coating Prepared via Laser Cladding

Effects of Laser Scanning Rate and Ti Content on Wear of Novel Fe-Cr-B-Al-Ti Coating Prepared via Laser Cladding