Search results for: electrochemical potentiokinetic reactivation test (EPR)

Authors: Yongkui Cui, Fengping Wang, Hailei Zhao, Muhammad Zubair Iqbal, Ziya Wang, Yan Li, Pengpeng LV

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The novel 3D SnO cabbages self-assembled by nanosheets were successfully synthesized via template-free hydrothermal growth method under facile conditions.The XRD results manifest that the as-prepared SnO is tetragonal phase. The TEM and HRTEM results show that the cabbage nanosheets are polycrystalline structure consisted of considerable single-crystalline nanoparticles. Two typical Raman modes A1g=210 and Eg=112 cm-1 of SnO are observed by Raman spectroscopy. Moreover, galvanostatic cycling tests has been performed using the SnO cabbages as anode material of lithium ion battery and the electrochemical results suggest that the synthesized SnO cabbage structures are a promising anode material for lithium ion batteries.

Keywords: electrochemical property, hydrothermal synthesis, lithium ion battery, stannous oxide

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Authors: Theo H. G. Moundzounga

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Arsenic and 2-chlorophenol are priority pollutants that pose serious health threats to humans and ecology. An electrochemical sensor, based on graphitic carbon nitride (g-C₃N₄) and carbon dots (CDs), was fabricated and used for the determination of arsenic and 2-chlorophenol. The g-C₃N₄/CDs nanocomposite was prepared via microwave irradiation heating method and was dropped-dried on the surface of the glassy carbon electrode (GCE). Transmission electron microscopy (TEM), X-ray diffraction (XRD), photoluminescence (PL), Fourier transform infrared spectroscopy (FTIR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) were used for the characterization of structure and morphology of the nanocomposite. Electrochemical characterization was done by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrochemical behaviors of arsenic and 2-chlorophenol on different electrodes (GCE, CDs/GCE, and g-C₃N₄/CDs/GCE) was investigated by differential pulse voltammetry (DPV). The results demonstrated that the g-C₃N₄/CDs/GCE significantly enhanced the oxidation peak current of both analytes. The analytes detection sensitivity was greatly improved, suggesting that this new modified electrode has great potential in the determination of trace level of arsenic and 2-chlorophenol. Experimental conditions which affect the electrochemical response of arsenic and 2-chlorophenol were studied, the oxidation peak currents displayed a good linear relationship to concentration for 2-chlorophenol (R²=0.948, n=5) and arsenic (R²=0.9524, n=5), with a linear range from 0.5 to 2.5μM for 2-CP and arsenic and a detection limit of 2.15μM and 0.39μM respectively. The modified electrode was used to determine arsenic and 2-chlorophenol in spiked tap and effluent water samples by the standard addition method, and the results were satisfying. According to the measurement, the new modified electrode is a good alternative as chemical sensor for determination of other phenols.

Keywords: electrochemistry, electrode, limit of detection, sensor

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Authors: Tareg Omar Mansour, Khaled Omar Elhaji

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Model solutions of pentanol in the salt water of various concentrations were subjected to electrochemical oxidation using a dimensionally stable anode (DSA) and a platinised titanium cathode. The removal of pentanol was analysed over time using gas chromatography (GC) and by monitoring the total organic carbon (TOC) concentration of the reaction mixture. It was found that the removal of pentanol occurred more efficiently at higher salinities and higher applied electrical current values. When using a salt concentration of 20,000 ppm and an applied current of 100 mA there was a decrease in concentration of pentanol of 15 %. When the salt concentration and applied current were increased to 58,000 ppm and 500 mA respectively, the decrease in concentration was improved to 64 %.

Keywords: dimensionally stable anode (DSA), total organic hydrocarbon (TOC), gas chromatography mass spectrometry (GCMS), electrochemical oxidation

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Authors: Ana P. R. N. Barroso, Maurício N. Kleinberg, Frederico R. Silva, Rodrigo F. Guimarães, Marcelo M. V. Parente, Walney S. Araújo

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The fight against accelerated wear of the equipment used in the oil and gas sector is a challenge for minimizing maintenance costs. Corrosion being one of the main agents of equipment deterioration, we seek alternative materials that exhibit improved corrosion resistance at low cost of production. This study aims to evaluate the corrosion behavior of experimental alloys containing 15% and 17% of chromium (Cr) and 5% of molybdenum (Mo) in comparison with an AISI 444 commercial alloy. Microstructural analyzes were performed on samples of the alloys before and after the electrochemical tests. Two samples of each solubilized alloy were also taken for analysis of the corrosion behavior by testing potentiodynamic polarization (PP) and Electrochemical Impedance Spectroscopy (EIS) with immersion time of 24 hours in electrolytic solution with acidic character. The graphics obtained through electrochemical tests of PP and EIS indicated that among the experimental alloys, the alloy with higher chromium content (17%) had a higher corrosion resistance, confirming the beneficial effect of adding chromium. When comparing the experimental alloys with the AISI 444 commercial alloy, it is observed that the AISI 444 commercial alloy showed superior corrosion resistance to that of the experimental alloys for both assays, PP and EIS. The microstructural analyzes performed after the PP and EIS tests confirmed the results previously described. These results suggest that the addition of these levels of molybdenum did not favor the electrochemical behavior of experimental ferritic alloys for the electrolytic medium studied.

Keywords: corrosion, molybdenum, electrochemical tests, experimental alloys

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Authors: Asmae Tafraouti, Yasmina Layouni

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The fabrication of cylindrical Tungsten micro-tools with a high aspect ratio is a real challenge because of several constraints that come into during their manufacture. In this paper, we will describe the process used to fabricate these micro-tools. It consists of using electrochemical etching. We will also present the optimal protocol that makes it possible to fabricate micro-tools with a high aspect ratio in a reproducible way. Next, we will show the limit of the experimental parameters chosen to manufacture micro-tools from a wire with an initial diameter of Φ_0=250µm. The protocol used allows obtaining an average diameter of Φ=88µm ±1 µm over a length of L=3.5mm.

Keywords: drop-off effect, electrochemical etching, micro-electrical discharge machining, tungsten micro-tools

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Authors: Seval Yilmaz, Filiz Bayrakci Karel, Ali Savas Koparal

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Textile products produced by leather have been indispensable for human consumption. Various chemicals are used to enhance the durability of end-products in the processing of leather products. The wastewaters from the leather industry which contain these chemicals exhibit toxic effects on the receiving environment and threaten the natural ecosystem. In this study, leather industry wastewater (LIW), which has high loads of contaminants, was treated using advanced treatment techniques instead of conventional methods. During the experiments, the performance of electrochemical methods was investigated. During the electrochemical experiments, the performance of batch electrooxidation (EO) using boron-doped diamond (BDD) electrodes with monopolar configuration for removal of chemical oxygen demand (COD) from LIW were investigated. The influences of electrolysis time, current density (which varies as 5 mA/cm², 10 mA/cm², 20 mA/cm², 30 mA/cm², 50 mA/cm²) and initial pH (which varies as 3,80 (natural pH of LIW), 7, 9) on removal efficiency were investigated in a batch stirred cell to determine the best treatment conditions. The current density applied to the electrochemical reactors is directly proportional to the consumption of electric energy, so electrical energy consumption was monitored during the experiment. The best experimental conditions obtained in electrochemical studies were as follows: electrolysis time = 60 min, current density = 30.0 mA/cm², pH 7. Using these parameters, 53.59% COD removal rates for LIW was achieved and total energy consumption was obtained as 13.03 kWh/m³. It is concluded that electrooxidation process constitutes a plausible and developable method for the treatment of LIW.

Keywords: BDD electrodes, COD removal, electrochemical treatment, leather industry wastewater

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Authors: Mohamed Benaicha, Mahdi Allam

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A new two stage electrochemical process as a safe, large area and low processing cost technique for the production of semi-conducting CuInSe2 (CIS) thin films is studied. CuIn precursors were first potentiostatically electrodeposited onto molybdenum substrates from an acidic thiocyanate electrolyte. In a second stage, the prepared metallic CuIn layers were used as substrate in the selenium electrochemical deposition system and subjected to a thermal treatment in vacuum atmosphere, to eliminate binary phase formation by reaction of the Cu2-x Se and InxSey selenides, leading to the formation of CuInSe2 thin film. Electrochemical selenization from aqueous electrolyte is introduced as an alternative to toxic and hazardous H2Se or Se vapor phase selenization used in physical techniques. In this study, the influence of film deposition parameters such as bath composition, temperature and potential on film properties was studied. The electrochemical, morphological, structural and compositional properties of electrodeposited thin films were characterized using various techniques. Results of Cyclic and Stripping-Cyclic Voltammetry (CV, SCV), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray microanalysis (EDX) investigations revealed good reproducibility and homogeneity of the film composition. Thereby optimal technological parameters for the electrochemical production of CuIn, Se as precursors for CuInSe2 thin layers are determined.

Keywords: photovoltaic, CIGS, copper alloys, electrodeposition, thin films

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Authors: Wanwisa Deenin, Abdulhadee Yakoh, Chahya Kreangkaiwal, Orawon Chailapakul, Kanitha Patarakul, Sudkate Chaiyo

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LipL32 is an outer membrane protein present only on pathogenic Leptospira species, which are the causative agent of leptospirosis. Leptospirosis symptoms are often misdiagnosed with other febrile illnesses as the clinical manifestations are non-specific. Therefore, an accurate diagnostic tool for leptospirosis is indeed critical for proper and prompt treatment. Typical diagnosis via serological assays is generally performed to assess the antibodies produced against Leptospira. However, their delayed antibody response and complicated procedure are undoubtedly limited the practical utilization especially in primary care setting. Here, we demonstrate for the first time an early-stage detection of LipL32 by an integrated lateral-flow immunoassay with electrochemical readout (eLFIA). A ferrocene trace tag was monitored via differential pulse voltammetry operated on a smartphone-based device, thus allowing for on-field testing. Superior performance in terms of the lowest detectable limit of detection (LOD) of 8.53 pg/mL and broad linear dynamic range (5 orders of magnitude) among other sensors available thus far was established. Additionally, the developed test strip provided a straightforward yet sensitive approach for diagnosis of leptospirosis using the collected human sera from patients, in which the results were comparable to the real-time polymerase chain reaction technique.

Keywords: leptospirosis, electrochemical detection, lateral flow immunosensor, point-of-care testing, early-stage detection

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Authors: Fredrick O. Okumu, Mangaka C. Matoetoe

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Silver-platinum (Ag-Pt) bimetallic nanoparticles (NPs) with varying mole fractions (1:1, 1:3 and 3:1) were prepared by co-reduction of hexachloroplatinate and silver nitrate with sodium citrate. Upon successful formation of both monometallic and bimetallic (BM) core shell nanoparticles, cyclic voltammetry (CV) was used to characterize the NPs. The drop coated nanofilms on the GC substrate showed characteristic peaks of monometallic Ag NPs; Ag+/Ag0 redox couple as well as the Pt NPs; hydrogen adsorption and desorption peaks. These characteristic peaks were confirmed in the bimetallic NPs voltammograms. The following varying current trends were observed in the BM NPs ratios; GCE/Ag-Pt 1:3 > GCE/Ag-Pt 3:1 > GCE/Ag-Pt 1:1. Fundamental electrochemical properties which directly or indirectly affects the applicability of films such as; diffusion coefficient (D), electroactive surface coverage, electrochemical band gap, electron transfer coefficient (α) and charge (Q) were assessed using Randles - Sevcik plot and Laviron’s equations . High charge and surface coverage was observed in GCE/Ag-Pt 1:3 which supports its enhanced current. GCE/Ag-Pt 3:1 showed high diffusion coefficient while GCE/Ag-Pt 1:1 possessed high electron transfer coefficient that is facilitated by its high apparent heterogeneous rate constant relative to other BM NPs ratios. Surface redox reaction was determined as adsorption controlled in all modified GCEs. Surface coverage is inversely proportional to size; therefore the surface coverage data suggests that Ag-Pt 1:1 NPs have a small particle size. Generally, GCE/Ag-Pt 1:3 depicts the best electrochemical properties.

Keywords: characterization, core-shell, electrochemical, nanoparticles

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Authors: Megha, Diksha, Seema Rani, Balwinder Kaur, Harminder Kaur

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Fe₃O₄@SiO₂@SB functionalized magnetic nanoparticles were synthesized and used to detect heavy metal ions such as Pb²⁺, Hg²⁺, and Cd²⁺ in water. The formation of Fe₃O₄@SiO₂@SB nanocatalyst was confirmed by XRD, SEM, TEM, and IR. The simultaneous determination of analyte cations was carried out using square wave anodic stripping voltammetry (SWASV). Investigation and optimisation were done to study how experimental variables affected the performance of the modified magnetic electrode. Pb²⁺, Hg²⁺, and Cd²⁺ were successfully detected using the designed sensor in the presence of various possibly interfering ions. The recovery rate was found to be 97.5% for Pb²⁺, 96.2% for Hg²⁺, 103.5% for Cd²⁺. The electrochemical sensor was also employed to determine the presence of heavy metal ions in drinking water samples, which are well below the World Health Organization (WHO) guidelines.

Keywords: magnetic nanoparticles, heavy metal ions, electrochemical sensor, environmental water samples

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Authors: Basanti Ekka, Talis Juhna

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Dairy industrial effluents originated by the typical processing activities are composed of various organic and inorganic constituents, and these include proteins, fats, inorganic salts, antibiotics, detergents, sanitizers, pathogenic viruses, bacteria, etc. These contaminants are harmful to not only human beings but also aquatic flora and fauna. Because consisting of large classes of contaminants, the specific targeted removal methods available in the literature are not viable solutions on the industrial scale. Therefore, in this on-going research, a series of coagulation, electrochemical, and catalytic methods will be employed. The bulk coagulation and electrochemical methods can wash off most of the contaminants, but some of the harmful chemicals may slip in; therefore, specific catalysts designed and synthesized will be employed for the removal of targeted chemicals. In the context of Latvian dairy industries, presently, work is under progress on the characterization of dairy effluents by total organic carbon (TOC), Inductively Coupled Plasma Mass Spectrometry (ICP-MS)/ Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), High-Performance Liquid Chromatography (HPLC), Gas Chromatography-Mass Spectrometry (GC-MS), and Mass Spectrometry. After careful evaluation of the dairy effluents, a cost-effective natural coagulant will be employed prior to advanced electrochemical technology such as electrocoagulation and electro-oxidation as a secondary treatment process. Finally, graphene oxide (GO) based hybrid materials will be used for post-treatment of dairy wastewater as graphene oxide has been widely applied in various fields such as environmental remediation and energy production due to the presence of various oxygen-containing groups. Modified GO will be used as a catalyst for the removal of remaining contaminants after the electrochemical process.

Keywords: catalysis, dairy wastewater, electrochemical method, graphene oxide

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Authors: Dahmane Mohamed, Tab Asma, Trari Mohamed

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BaMnO₃ nanoparticles were synthesized by a nitrate route. Its structure and physical properties were characterized by means of X-ray powder diffraction, radio crystallographic analysis, ultraviolet-visible absorption spectroscopy in diffuse reflectance mode, infrared spectroscopy, and electrochemical measurements. The optical study showed that barium manganese oxide presents a direct transition with band energy 2.13 eV. The electrochemical study allowed us to identify the redox peaks and the corrosion parameters. Capacitance measurement clearly showed n-type conductivity. The photodegradation of paracetamol by BaMnO₃ was followed by UV-visible spectrophotometry; the results were then confirmed by HPLC. BaMnO₃ has shown its photocatalytic efficiency in the photodegradation of 10 mg/L paracetamol under solar irradiation, with a yield of ≈ 88%. The kinetic study has shown that paracetamol degrades with first-order kinetics.

Keywords: BaMnO₃, photodegradation, paracetamol, electrochemical measurements, solar light

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Authors: Usha N. Murthy, H. B. Rekha, Mahaveer Devoor

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The introduction of more stringent pollution regulations, in relation to financial and social pressures for sustainable development, has pressed toward limiting the volumes of industrial and domestic effluents discharged into the environment-as well as to increase the efforts within research and development of new or more efficient wastewater treatment technologies. Considering both discharge volume and effluent composition, wastewater generated by the textile industry is rated as the most polluting among all industrial sectors. The pollution load is mainly due to spent dye baths, which are composed of unreacted dyes, dispersing agents, surfactants, salts and organics. In the present investigation, the textile dye wastewater was characterized by high colour, chemical oxygen demand (COD), total dissolved solids (TDS) and pH. Electrochemical oxidation process for four plate electrodes was carried out at five different current intensities, out of which 0.14A has achieved maximum percentage removal of COD with 75% and 83% of colour. The COD removal rate in kg COD/h/m2 decreases with increase in the current intensity. The energy consumption increases with increase in the current intensity. Hence, textile dye wastewater can be effectively pre-treated by electrochemical oxidation method where the process limits objectionable colour while leaving the COD associated with organics left for natural degradation thus causing a sustainable reduction in pollution load.

Keywords: electrochemical treatment, COD, colour, environmental engineering

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Authors: Alex Soares Castro, Matheus Manoel Teles de Menezes, Larissa Silva de Azevedo, Ana Carolina Caleffi Patelli, Osmair Vital de Oliveira, Aline Thais Bruni, Marcelo Firmino de Oliveira

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Considering the problem of the seizure of illicit drugs, as well as the development of electrochemical sensors using chemically modified electrodes, this work shows the study of the electrochemical activity of cocaine in carbon paste electrode chemically modified with Cu (II) trans 3-MeO salcn complex. In this context, cyclic voltammetry was performed on 0.1 mol.L⁻¹ KCl supporting electrolyte at a scan speed of 100 mV s⁻¹, using an electrochemical cell composed of three electrodes: Ag /AgCl electrode (filled KCl 3 mol.L⁻¹) from Metrohm® (reference electrode); a platinum spiral electrode, as an auxiliary electrode, and a carbon paste electrode chemically modified with Cu (II) trans 3-MeO complex (as working electrode). Two forms of cocaine were analyzed: cocaine hydrochloride (pH 3) and cocaine free base form (pH 8). The PM7 computational method predicted that the hydrochloride form is more stable than the free base form of cocaine, so with cyclic voltammetry, we found electrochemical signal only for cocaine in the form of hydrochloride, with an anodic peak at 1.10 V, with a linearity range between 2 and 20 μmol L⁻¹ had LD and LQ of 2.39 and 7.26x10-5 mol L⁻¹, respectively. The study also proved that cocaine is adsorbed on the surface of the working electrode, where through an irreversible process, where only anode peaks are observed, we have the oxidation of cocaine, which occurs in the hydrophilic region due to the loss of two electrons. The mechanism of this reaction was confirmed by the ab-inito quantum method.

Keywords: ab-initio computational method, analytical method, cocaine, Schiff base complex, voltammetry

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Authors: Soledad Carinelli, Iñigo Fernández, José Luis González-Mora, Pedro A. Salazar-Carballo

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Mastitis is the most relevant inflammatory disease in cattle, affecting the animal health and causing important economic losses on dairy farms. This disease takes place in the mammary gland or udder when some opportunistic microorganisms, such as Staphylococcus aureus, Streptococcus agalactiae, Corynebacterium bovis, etc., invade the teat canal. According to the severity of the inflammation, mastitis can be classified as sub-clinical, clinical and chronic. Standard methods for mastitis detection include counts of somatic cells, cell culture, electrical conductivity of the milk, and California test (evaluation of “gel-like” matrix consistency after cell lysed with detergents). However, these assays present some limitations for accurate detection of subclinical mastitis. Currently, haptoglobin, an acute phase protein, has been proposed as novel and effective biomarker for mastitis detection. In this work, an electrochemical biosensor based on polydopamine-modified magnetic nanoparticles (MNPs@pDA) for haptoglobin detection is reported. Thus, MNPs@pDA has been synthesized by our group and functionalized with hemoglobin due to its high affinity to haptoglobin protein. The protein was labeled with specific antibodies modified with alkaline phosphatase enzyme for its electrochemical detection using an electroactive substrate (1-naphthyl phosphate) by differential pulse voltammetry. After the optimization of assay parameters, the haptoglobin determination was evaluated in milk. The strategy presented in this work shows a wide range of detection, achieving a limit of detection of 43 ng/mL. The accuracy of the strategy was determined by recovery assays, being of 84 and 94.5% for two Hp levels around the cut off value. Milk real samples were tested and the prediction capacity of the electrochemical biosensor was compared with a Haptoglobin commercial ELISA kit. The performance of the assay has demonstrated this strategy is an excellent and real alternative as screen method for sub-clinical bovine mastitis detection.

Keywords: bovine mastitis, haptoglobin, electrochemistry, magnetic nanoparticles, polydopamine

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Authors: Aliya Kurbanova, Nurlan Akhmetov, Abilmansur Yeshmuratov, Yerzhigit Sugurbekov, Ramiz Zulkharnay, Gulzat Demeuova, Murat Baisariyev, Gulnar Sugurbekova

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Last decades crude oils have tended to become more challenge to process due to increasing amounts of sour and heavy crude oils. Some crude oils contain high vanadium and nickel content, for example Pavlodar LLP crude oil, which contains more than 23.09 g/t nickel and 58.59 g/t vanadium. In this study, we used two types of metal removing methods such as solvent extraction and electrochemical. The present research is conducted for comparative analysis of the deasphalting with organic solvents (cyclohexane, carbon tetrachloride, chloroform) and electrochemical method. Applying the cyclic voltametric analysis (CVA) and Inductively coupled plasma mass spectrometry (ICP MS), these mentioned types of metal extraction methods were compared in this paper. Maximum efficiency of deasphalting, with cyclohexane as the solvent, in Soxhlet extractor was 66.4% for nickel and 51.2% for vanadium content from crude oil. Percentage of Ni extraction reached maximum of approximately 55% by using the electrochemical method in electrolysis cell, which was developed for this research and consists of three sections: oil and protonating agent (EtOH) solution between two conducting membranes which divides it from two capsules of 10% sulfuric acid and two graphite electrodes which cover all three parts in electrical circuit. Ions of metals pass through membranes and remain in acid solutions. The best result was obtained in 60 minutes with ethanol to oil ratio 25% to 75% respectively, current fits into the range from 0.3A to 0.4A, voltage changed from 12.8V to 17.3V.

Keywords: demetallization, deasphalting, electrochemical removal, heavy metals, petroleum engineering, solvent extraction

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Authors: B. B. S. Pereira, M. O. Souza, L. P. Zanetti, L. C. S. Oliveira, J. R. P. Moreno, M. P. Souza, V. R. Colturato, C. M. Machado

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Background: The introduction of prophylactic or preemptive therapies has effectively decreased the CMV mortality rates after hematopoietic stem cell transplantation (HSCT). CMV antigenemia (pp65) or quantitative PCR are methods currently approved for CMV surveillance in pre-emptive strategies. Commercial assays are preferred as cut-off levels defined by in-house assays may vary among different protocols and in general show low reproducibility. Moreover, comparison of published data among different centers is only possible if international standards of quantification are included in the assays. Recently, the World Health Organization (WHO) established the first international standard for CMV detection. The real time PCR COBAS Ampliprep/ CobasTaqMan (CAP/CTM) (Roche®) was developed using the WHO standard for CMV quantification. However, the cut-off for the introduction of antiviral has not been determined yet. Methods: We conducted a retrospective study to determine: 1) the sensitivity and specificity of the new CMV CAP/CTM test in comparison with pp65 antigenemia to detect episodes of CMV infection/reactivation, and 2) the cut-off of viral load for introduction of ganciclovir (GCV). Pp65 antigenemia was performed and the corresponding plasma samples were stored at -20°C for further CMV detection by CAP/CTM. Comparison of tests was performed by kappa index. The appearance of positive antigenemia was considered the state variable to determine the cut-off of CMV viral load by ROC curve. Statistical analysis was performed using SPSS software version 19 (SPSS, Chicago, IL, USA.). Results: Thirty-eight patients were included and followed from August 2014 through May 2015. The antigenemia test detected 53 episodes of CMV infection in 34 patients (89.5%), while CAP/CTM detected 37 episodes in 33 patients (86.8%). AG and PCR results were compared in 431 samples and Kappa index was 30.9%. The median time for first AG detection was 42 (28-140) days, while CAP/CTM detected at a median of 7 days earlier (34 days, ranging from 7 to 110 days). The optimum cut-off value of CMV DNA was 34.25 IU/mL to detect positive antigenemia with 88.2% of sensibility, 100% of specificity and AUC of 0.91. This cut-off value is below the limit of detection and quantification of the equipment which is 56 IU/mL. According to CMV recurrence definition, 16 episodes of CMV recurrence were detected by antigenemia (47.1%) and 4 (12.1%) by CAP/CTM. The duration of viremia as detected by antigenemia was shorter (60.5% of the episodes lasted ≤ 7 days) in comparison to CAP/CTM (57.9% of the episodes lasting 15 days or more). This data suggests that the use of antigenemia to define the duration of GCV therapy might prompt early interruption of antiviral, which may favor CMV reactivation. The CAP/CTM PCR could possibly provide a safer information concerning the duration of GCV therapy. As prolonged treatment may increase the risk of toxicity, this hypothesis should be confirmed in prospective trials. Conclusions: Even though CAP/CTM by ROCHE showed great qualitative correlation with the antigenemia technique, the fully automated CAP/CTM did not demonstrate increased sensitivity. The cut-off value below the limit of detection and quantification may result in delayed introduction of pre-emptive therapy.

Keywords: antigenemia, CMV COBAS/TAQMAN, cytomegalovirus, antiviral cut-off

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Authors: Zahrasadat Hosseini, Jie Yuan

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Point-of-care (POC) diagnostic devices based on lab-on-a-chip (LOC) technology have the potential to revolutionize medical diagnostics. However, the development of an ideal microfluidic system based on LOC technology for diagnostics purposes requires overcoming several obstacles, such as improving sensitivity, selectivity, portability, cost-effectiveness, and prototyping methods. While numerous studies have introduced technologies and systems that advance these criteria, existing systems still have limitations. Electrochemical enzyme-linked immunosorbent assay (e-ELISA) in a LOC device offers numerous advantages, including enhanced sensitivity, decreased turnaround time, minimized sample and analyte consumption, reduced cost, disposability, and suitability for miniaturization, integration, and multiplexing. In this study, we present a novel design and fabrication method for a microfluidic diagnostic platform that integrates screen-printed electrochemical carbon/silver chloride electrodes on flexible printed circuit boards with flexible, multilayer, polydimethylsiloxane (PDMS) microfluidic networks to accurately manipulate and pre-immobilize analytes for performing electrochemical enzyme-linked immunosorbent assay (e-ELISA) for multiplexed quantification of blood serum biomarkers. We further demonstrate fast, cost-effective prototyping, as well as accurate and reliable detection performance of this device for quantification of interleukin-6-spiked samples through electrochemical analytics methods. We anticipate that our invention represents a significant step towards the development of user-friendly, portable, medical-grade, POC diagnostic devices.

Keywords: lab-on-a-chip, point-of-care diagnostics, electrochemical ELISA, biomarker quantification, fast prototyping

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Authors: Zahrasadat Hosseini, Jie Yuan

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Point-of-care (POC) diagnostic devices based on lab-on-a-chip (LOC) technology have the potential to revolutionize medical diagnostics. However, the development of an ideal microfluidic system based on LOC technology for diagnostics purposes requires overcoming several obstacles, such as improving sensitivity, selectivity, portability, cost-effectiveness, and prototyping methods. While numerous studies have introduced technologies and systems that advance these criteria, existing systems still have limitations. Electrochemical enzyme-linked immunosorbent assay (e-ELISA) in a LOC device offers numerous advantages, including enhanced sensitivity, decreased turnaround time, minimized sample and analyte consumption, reduced cost, disposability, and suitability for miniaturization, integration, and multiplexing. In this study, we present a novel design and fabrication method for a microfluidic diagnostic platform that integrates screen-printed electrochemical carbon/silver chloride electrodes on flexible printed circuit boards with flexible, multilayer, polydimethylsiloxane (PDMS) microfluidic networks to accurately manipulate and pre-immobilize analytes for performing electrochemical enzyme-linked immunosorbent assay (e-ELISA) for multiplexed quantification of blood serum biomarkers. We further demonstrate fast, cost-effective prototyping, as well as accurate and reliable detection performance of this device for quantification of interleukin-6-spiked samples through electrochemical analytics methods. We anticipate that our invention represents a significant step towards the development of user-friendly, portable, medical-grade POC diagnostic devices.

Keywords: lab-on-a-chip, point-of-care diagnostics, electrochemical ELISA, biomarker quantification, fast prototyping

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Authors: Shekher Kummari, V. Sunil Kumar, K. Vengatajalabathy Gobi

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A simple, cost-effective, reusable and reagent-free electrochemical biosensor is developed with functionalized multiwall carbon nanotube paste electrode (f-CNTPE) for the sensitive and selective determination of the important chemotherapeutic drug methotrexate (MTX), which is widely used for the treatment of various cancer and autoimmune diseases. The electrochemical response of the fabricated electrode towards the detection of MTX is examined by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). CV studies have shown that f-CNTPE electrode system exhibited an excellent electrocatalytic activity towards the oxidation of MTX in phosphate buffer (0.2 M) compared with a conventional carbon paste electrode (CPE). The oxidation peak current is enhanced by nearly two times in magnitude. Applying the DPV method under optimized conditions, a linear calibration plot is achieved over a wide range of concentration from 4.0×10⁻⁷ M to 5.5×10⁻⁶ M with the detection limit 1.6×10⁻⁷ M. further, by applying the SWV method a parabolic calibration plot was achieved starting from a very low concentration of 1.0×10⁻⁸ M, and the sensor could detect as low as 2.9×10⁻⁹ M MTX in 10 s and 10 nM were detected in steady state current-time analysis. The f-CNTPE shows very good selectivity towards the specific recognition of MTX in the presence of important biological interference. The electrochemical biosensor detects MTX in-vitro directly from pharmaceutical sample, undiluted urine and human blood serum samples at a concentration range 5.0×10⁻⁷ M with good recovery limits.

Keywords: amperometry, electrochemical detection, human blood serum, methotrexate, MWCNT, SWV

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Authors: Nadia Hammouda, Kamel Belmokre

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Organic coatings are widely employed in the corrosion protection of most metal surfaces, particularly steel. They provide a barrier against corrosive species present in the environment, due to their high resistance to oxygen, water and ions transport. This study focuses on the evaluation of corrosion protection performance of epoxy paint on the carbon steel surface in sea water by Electrochemical Impedance Spectroscopy (EIS). The electrochemical behavior of painted surface was estimated by EIS parameters that contained paint film resistance, paint film capacitance and double layer capacitance. On the basis of calculation using EIS spectrums it was observed that pore resistance (Rpore) decreased with the appearance of doubled layer capacitance (Cdl) due to the electrolyte penetration through the film. This was further confirmed by the decrease of diffusion resistance (Rd) which was also the indicator of the deterioration of paint film protectiveness.

Keywords: epoxy paints, carbon steel, electrochemical impedance spectroscopy, corrosion mechanisms, seawater

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Authors: Ádám Vass, István Bakos, Irina Borbáth, Zoltán Pászti, István Sajó, András Tompos

Abstract:

Important requirements for the anode side electrocatalysts of polymer electrolyte membrane (PEM) fuel cells are CO-tolerance, stability and corrosion resistance. Carbon is still the most common material for electrocatalyst supports due to its low cost, high electrical conductivity and high surface area, which can ensure good dispersion of the Pt. However, carbon becomes degraded at higher potentials and it causes problem during application. Therefore it is important to explore alternative materials with improved stability. Molybdenum-oxide can improve the CO-tolerance of the Pt/C catalysts, but it is prone to leach in acidic electrolyte. The Mo was stabilized by isovalent substitution of molybdenum into the rutile phase titanium-dioxide lattice, achieved by a modified multistep sol-gel synthesis method optimized for preparation of Ti0.7Mo.3O2-C composite. High degree of Mo incorporation into the rutile lattice was developed. The conductivity and corrosion resistance across the anticipated potential/pH window was ensured by mixed oxide – activated carbon composite. Platinum loading was carried out using NaBH4 and ethylene glycol; platinum content was 40 wt%. The electrocatalyst was characterized by both material investigating methods (i.e. XRD, TEM, EDS, XPS techniques) and electrochemical methods (cyclic-voltammetry, COads stripping voltammetry, hydrogen oxidation reaction on rotating disc electrode). The electrochemical activity of the sample was compared to commercial 40 wt% Pt/C (Quintech) and PtRu/C (Quintech, Pt= 20 wt%, Ru= 10 wt%) references. Enhanced CO tolerance of the electrocatalyst prepared using the Ti0.7Mo.3O2-C composite material was evidenced by the appearance of a CO-oxidation related 'pre-peak' and by the pronounced shift of the maximum of the main CO oxidation peak towards less positive potential compared to Pt/C. Fuel cell polarization measurements were also carried out using Bio-Logic and Paxitech FCT-150S test device. All details on the design, preparation, characterization and testing by both electrochemical measurements and fuel cell test device of electrocatalyst supported on Ti0.7Mo.3O2-C composite material will be presented and discussed.

Keywords: anode electrocatalyst, composite material, CO-tolerance, TiMoOx

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Authors: Yen-Ping Peng, Ku-Fan Chen, Ken-Lin Chang, Jian Sun

Abstract:

In this study, palladium loaded titanium dioxide nanotube arrays (Pd/TNAs) was successfully synthesized by anodic oxidation etching method combined with microwave hydrothermal method, using tea or coffee as a green reductant. Pd/TNAs was employed as an electrode in a photoelectrochemcial (PEC) system to simultaneously remove azo-dye and to generate hydrogen in the anodic and cathodic chamber, respectively. The chemical and physical properties of as-synthesized Pd/TNAs were characterized by scanning electron microscopy (SEM), ultraviolet–visible spectroscopy (UV-vis), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). SEM image indicates the diameter and the length of Pd/TNAs were approximately 300 nm and 2.5 μm, respectively. XPS analyses indicate that 1.13% (atomic %) of Pd was loaded onto the surface of TNAs. UV-vis results show that the band gap of TNAs was reduced from 3.2 eV to 2.37 eV after Pd loading. In addition, the electrochemical performances of Pd/TNAs were investigated by photocurrent density test and electrochemical impedance spectroscopy (EIS). The photocurrent (4.0 mA/cm²) of Pd /TNAs was higher than that of the uncoated TNAs (1.4 mA/cm²) at a bias potential of 1 V (vs. Ag/AgCl), indicating that Pd/TNAs-C can effectively separate photogenerated electrons and holes. The mechanism of our PEC system was proposed and discussed in detail in this study.

Keywords: Pd/TNAs, photoelectrochemical, azo-dye degradation, hydrogen generation

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Authors: Nadia Hammouda, K. Belmokre

Abstract:

Organic coatings are widely employed in the corrosion protection of most metal surfaces, particularly steel. They provide a barrier against corrosive species present in the environment, due to their high resistance to oxygen, water and ions transport. This study focuses on the evaluation of corrosion protection performance of epoxy paint on the carbon steel surface in sea water by Electrochemical Impedance Spectroscopy (EIS). The electrochemical behavior of painted surface was estimated by EIS parameters that contained paint film resistance, paint film capacitance and double layer capacitance. On the basis of calculation using EIS spectrums it was observed that pore resistance (Rpore) decreased with the appearance of doubled layer capacitance (Cdl) due to the electrolyte penetration through the film. This was further confirmed by the decrease of diffusion resistance (Rd) which was also the indicator of the deterioration of paint film protectiveness.

Keywords: epoxy paints, carbon steel, electrochemical impedance spectroscopy, corrosion mechanisms, sea water

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Authors: R. Khrifou, M. Galai, R. Touir, M. Ebn Touhami, Y. Ramli

Abstract:

A 2-(5-methyl-2-Nitro-1H-imidazol-1-yl)ethyl benzoate (IMDZ-B) was synthesized and characterized using elemental analyses, NMR, and Fourier transform infrared (FTIR) techniques. Its effect on brass corrosion in 1.0 M H₃PO₄ solution was investigated by using electrochemical measurements coupled with X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX). The polarization measurements showed that the IMDZ-B acts as a mixed-type inhibitor. Indeed, it is found that the IMDZ-B compound is a very good inhibitor, and its inhibition efficiency increases with concentration to reach a maximum of 99.5 % at 10-³ M. In addition, the obtained electrochemical parameters from impedance indicated that the IMDZ-B molecules act by adsorption on metallic surfaces. This adsorption was found to obey Langmuir’s adsorption isotherm. However, the temperature effect on the performance of IMDZ-B was also studied. It is found that the IMDZ-B takes its performance at high temperatures. In addition, the obtained kinetic and thermodynamic parameters showed that the IMDZ-B molecules act via two adsorption modes, physisorption and chemisorptions, and its process is endothermic and spontaneous. Finally, the XRD and SEM/EDX analyses confirmed the electrochemical obtained results.

Keywords: low concentration, anti-corrosion brass, IMDZ-B product, phosphoric acid solution, electrochemical, SEM\EDAX analysis

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Authors: Girish Sambhaji Gund

Abstract:

The controlled nanostructure growth and its strong coupling with the current collector are key factors to achieve good electrochemical performance of faradaic-dominant electroactive materials. We employed binder-less and additive-free hydrothermal and physical vapor doping methods for the synthesis of nickel (Ni) and cobalt (Co) based compounds nanostructures (NiO, NiCo2O4, NiCo2S4) deposited on different conductive substrates such as carbon nanotube (CNT) on stainless steel, and reduced graphene oxide (rGO) and N-doped rGO on nickel foam (NF). The size and density of Ni- and Co-based compound nanostructures are controlled through the strong coupling with carbon allotropes on stainless steel and NF substrates. This controlled nanostructure of Ni- and Co-based compounds with carbon allotropes leads to stable faradaic electrochemical reactions at the material/current collector interface and within the electrode, which is consequence of strong coupling of nanostructure with functionalized carbon surface as a buffer layer. Thus, it is believed that the results provide the synergistic approaches to stabilize electrode materials physically and chemically, and hence overall electrochemical activity of faradaic dominating battery-type electrode materials through buffer layer engineering.

Keywords: metal compounds, carbon allotropes, doping, electrochemicstry, hybrid supercapacitor

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Authors: M. El Hajji, A. Hallaoui, L. Bazzi, A. Benlhachemi, O. Jbara, A. Tara, B. Bakiz, L. Bazzi, M. Hilali

Abstract:

The objective of this study was the development of zinc-copper binary oxide "Cu2O-ZnO" thin films by the electrochemical method "cathodic electrodeposition" and their uses for the degradation of a basic dye "Congo Red" by direct anodic oxidation. The anode materials synthesized were characterized by X-ray diffraction "XRD" and by scanning electron microscopy "SEM" coupled to EDS.

Keywords: Cu2O-ZnO thin films, cathodic electrodeposition, electrodegradation, Congo Red, BDD

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Authors: A. Guemache, M. Omari

Abstract:

Oxides with formula Ca1-xSrx MnO3 (0≤x≤0.2) were synthesized using co-precipitation method. The identification of the obtained phase was carried out using infrared spectroscopy and X-ray diffraction. Thermogravimetric and differential analysis was permitted to characterize different transformations of precursors which take place during one heating cycle. The study of electrochemical behavior was carried out by cyclic voltammetry and impedance spectroscopy. The obtained results show that apparent catalytic activity improved when increasing the concentration of strontium. Anodic current densities varies from 1.3 to 5.9 mA/cm2 at the rate scan of 20 mV.s-1 and a potential 0.8 V for oxides with composition x=0 to 0.2.

Keywords: oxide, co-precipitation, electrochemical properties, cathode-type

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Authors: Mandlenkosi George Robert Mahlobo, Tumelo Seadira, Major Melusi Mabuza, Peter Apata Olubambi

Abstract:

Cathodic protection (CP) has been widely considered a suitable technique for mitigating corrosion of buried metal structures. Plenty of efforts have been made in developing techniques, in particular non-destructive techniques, for monitoring and quantifying the effectiveness of CP to ensure the sustainability and performance of buried steel structures. The aim of this study was to investigate the evolution of the electrochemical processes at the steel/soil interface during the application of CP on steel in simulated soil. Carbon steel was subjected to electrochemical tests with NS4 solution used as simulated soil conditions for 4 days before applying CP for a further 11 days. A previously modified non-destructive voltammetry technique was applied before and after the application of CP to measure the corrosion rate. Electrochemical impedance spectroscopy (EIS), in combination with mathematical modeling through equivalent electric circuits, was applied to determine the electrochemical behavior at the steel/soil interface. The measured corrosion rate was found to have decreased from 410 µm/yr to 8 µm/yr between days 5 and 14 because of the applied CP. Equivalent electrical circuits were successfully constructed and used to adequately model the EIS results. The modeling of the obtained EIS results revealed the formation of corrosion products via a mixed activation-diffusion mechanism during the first 4 days, while the activation mechanism prevailed in the presence of CP, resulting in a protective film. The x-ray diffraction analysis confirmed the presence of corrosion products and the predominant protective film corresponding to the calcareous deposit.

Keywords: carbon steel, cathodic protection, NS4 solution, voltammetry, EIS

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Authors: Sujit Kumar Guchhait, Subir Paul

Abstract:

One of the major research areas is to find an alternative source of energy to fulfill the energy crisis and environmental problems. The Fuel cell is such kind of energy producing unit. Use of fuel cell to produce renewable energy for commercial purpose is limited by the high cost of Pt based electrode material. Development of high energetic, as well as inexpensive fuel cell electrode materials, is needs of hour to produce clean energy using derive bio-fuel. In this present investigation, inexpensive Cu-Ni-CeO2 electrode material has been synthesized by using pulse current. The surface morphology of the electrode materials is controlled by several deposition parameters to increase the rate of electrochemical oxidation of alcoholic fuel, ethanol. The electrochemical characterization of the developed material was done by Cyclic Voltammetry (CV) and Chronoamperometry (CA) and Electrochemical Impedance Spectroscopy test. It is interesting to find that both these materials have shown high electrocatalytic properties in terms of high exchange current density (I0), low polarization resistance (Rp) and low impedance. It is seen that the addition of CeO2 to Ni-Cu has outperformed Pt as far as high electrocatalytic properties are concerned. The exchange current density on the Cu-Ni-CeO2 electrode surface for ethanol oxidation is about eight times higher than the same on the Pt surface with much lower polarization resistance than the later. The surface morphology of the electrode materials has been revealed by Field Effect Scanning Electron Microscope (FESEM). It is seen that grains are narrow and subspherical with 3D surface containing pores in between two elongated grains. XRD study exhibits the presence of Ni and CeO2 on the Cu surface.

Keywords: electro-catalyst, alcoholic fuel, cyclic voltammetry, potentiodynamic polarization, EIS, XRD, SEM

Procedia PDF Downloads 271