scholarly journals An Immunosensor for Pathogenic Staphylococcus aureus Based on Antibody Modified Aminophenyl-Au Electrode

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Amani Chrouda ◽  
Mohamed Braiek ◽  
Karima Bekir Rokbani ◽  
Amina Bakhrouf ◽  
Abderrazak Maaref ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Electron Transfer ◽  
Gold Electrode ◽  
High Selectivity ◽  
Electrochemical Impedance ◽  
Transfer Resistance ◽  
Acidic Aqueous Solution ◽  
Stepwise Assembly ◽  
Electron Transfer Resistance

The objective of this work is to elaborate an immunosensing system which will detect and quantify Staphylococcus aureus bacteria. A gold electrode was modified by electrografting of 4-nitrophenyl diazonium, in situ synthesized in acidic aqueous solution. The immunosensor was fabricated by immobilizing affinity-purified polyclonal anti S. aureus antibodies on the modified gold electrode. Cyclic voltammetry (CV) and Faradaic Electrochemical Impedance Spectroscopy (EIS) were employed to characterize the stepwise assembly of the immunosensor. The performance of the developed immunosensor was evaluated by monitoring the electron-transfer resistance detected using Faradaic EIS. The experimental results indicated a linear relationship between the relative variation of the electron transfer resistance and the logarithmic value of S. aureus concentration, with a slope of 0.40 ± 0.08 per decade of concentration. A low quantification limit of 10±2 CFU per ml and a linear range up to 107±2×106 CFU per mL were obtained. The developed immunosensors showed high selectivity to Escherichia coli and Staphylococcus saprophyticus.

scholarly journals Fabrication of an Amperometric Flow-Injection Microfluidic Biosensor Based on Laccase for In Situ Determination of Phenolic Compounds

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Juan C. Gonzalez-Rivera ◽  
Johann F. Osma
Keyword(s):  
Electron Transfer ◽  
Flow Injection ◽  
Electrochemical Impedance ◽  
Limit Of Detection ◽  
Operating Conditions ◽  
Optimum Operating ◽  
Transfer Resistance ◽  
Injection Flow ◽  
Microfluidic Biosensor

We aim to develop an in situ microfluidic biosensor based on laccase fromTrametes pubescenswith flow-injection and amperometry as the transducer method. The enzyme was directly immobilized by potential step chronoamperometry, and the immobilization was studied using cyclic voltammetry and electrochemical impedance spectroscopy. The electrode response by amperometry was probed using ABTS and syringaldazine. A shift of interfacial electron transfer resistance and the electron transfer rate constant from 18.1 kΩ to 3.9 MΩ and 4.6 × 10−2 cm s−1to 2.1 × 10−4 cm s−1, respectively, evidenced that laccase was immobilized on the electrode by the proposed method. We established the optimum operating conditions of temperature (55°C), pH (4.5), injection flow rate (200 µL min−1), and applied potential (0.4 V). Finally, the microfluidic biosensor showed better lower limit of detection (0.149 µM) and sensitivity (0.2341 nA µM−1) for ABTS than previous laccase-based biosensors and the in situ operation capacity.

scholarly journals Electrochemical triggering of lipid bilayer lift-off oscillation at the electrode interface

2019 ◽  
Vol 16 (150) ◽  
pp. 20180626 ◽  
Author(s):  
Nikolay V. Ryzhkov ◽  
Natalya A. Mamchik ◽  
Ekaterina V. Skorb
Keyword(s):  
Lipid Bilayer ◽  
Gold Electrode ◽  
Electrochemical Impedance ◽  
Solid Support ◽  
Polymer Support ◽  
Layer By Layer ◽  
Free Standing ◽  
Electrochemical Approach ◽  
Lift Off

In situ studies of transmembrane channels often require a model bioinspired artificial lipid bilayer (LB) decoupled from its underlaying support. Obtaining free-standing lipid membranes is still a challenge. In this study, we suggest an electrochemical approach for LB separation from its solid support via hydroquinone oxidation. Layer-by-layer deposition of polyethylenimine (PEI) and polystyrene sulfonate (PSS) on the gold electrode was performed to obtain a polymeric nanocushion of [PEI/PSS] 3 /PEI. The LB was deposited on top of an underlaying polymer support from the dispersion of small unilamellar vesicles due to their electrostatic attraction to the polymer support. Since lipid zwitterions demonstrate pH-dependent charge shifting, the separation distance between the polyelectrolyte support and LB can be adjusted by changing the environmental pH, leading to lipid molecules recharge. The proton generation associated with hydroquinone oxidation was studied using scanning vibrating electrode and scanning ion-selective electrode techniques. Electrochemical impedance spectroscopy is suggested to be a powerful instrument for the in situ observation of processes associated with the LB–solid support interface. Electrochemical spectroscopy highlighted the reversible disappearance of the LB impact on impedance in acidic conditions set by dilute acid addition as well as by electrochemical proton release on the gold electrode due to hydroquinone oxidation.

scholarly journals Corrosion of Ferritic Steels in High Temperature Molten Salt Coolants for Nuclear Applications

2008 ◽  
Vol 1125 ◽  
Author(s):  
Joseph Farmer ◽  
Bassem El-dasher ◽  
Magdalena Serrano de Caro ◽  
James Ferreira
Keyword(s):  
High Temperature ◽  
Electrochemical Impedance ◽  
Measurement Techniques ◽  
Complex Impedance ◽  
Ferritic Steels ◽  
Valuable Insight ◽  
Oxide Dispersion ◽  
Transfer Resistance ◽  
Molten Fluoride

ABSTRACTCorrosion of ferritic steels, including oxide dispersion strengthened (ODS) variants, in high temperature molten fluoride salts may limit the life of advanced reactors, including some hybrid systems that are now under consideration. In some cases, the steel may be protected through galvanic coupling with other less noble materials with special neutronic properties such as beryllium. This paper reports the development of a model for predicting corrosion rates for various ferritic steels, with and without oxide dispersion strengthening, in FLiBe (Li2BeF4) and FLiNaK (Li-Na-K-F) coolants at temperatures up to 800 °C. Mixed potential theory is used to account for the protection of steel by beryllium, Tafel kinetics are used to predict rates of dissolution as a function of temperature and potential, and the thinning of the mass-transfer boundary layer with increasing Reynolds number is accounted for with dimensionless correlations. The model also accounts for the deceleration of corrosion as the coolants become saturated with dissolved chromium and iron. Electrochemical impedance spectroscopy has been used for the initial in situ study of an ODS ferritic steel in high-temperature molten fluoride salt environments, with the complex impedance spectra obtained at its open circuit corrosion potential (OCP) interpreted in terms of the basic components of the equivalent circuit, which include the electrolyte conductivity, the interfacial charge transfer resistance, and the interfacial capacitance. Such in situ measurement techniques may provide valuable insight into the degradation of materials under realistic conditions.

Electrochemical impedance spectroscopy study of electron transfer at poly(3,4-ethylenedioxythiophene) containing gold nanoparticles coating

2011 ◽  
Vol 76 (12) ◽  
pp. 1433-1445
Author(s):  
Stelian Lupu
Keyword(s):  
Gold Nanoparticles ◽  
Electron Transfer ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Au Nanoparticles ◽  
Electrochemical Impedance ◽  
Electrochemical Polymerization ◽  
Composite Coatings ◽  
Supporting Electrolyte ◽  
Transfer Resistance

Electrochemical impedance spectroscopy (EIS) was used for characterization of electron transfer in various redox probes, such as the redox couple ferrocyanide-ferricyanide, ferrocene, ferrocenemethanol, and the poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymer containing gold nanoparticles. The PEDOT coating was deposited onto platinum (Pt) and glassy carbon (GC) electrodes by galvanostatic electrochemical polymerization from an aqueous solution containing 10–2 M EDOT and 10–1 M LiClO4 as supporting electrolyte. The PEDOT-Au nanoparticles composite coating was prepared by droplet deposition of Au nanoparticles on top of the Pt/PEDOT and GC/PEDOT modified electrodes. The pure PEDOT and PEDOT-Au nanoparticles composite coatings were investigated using EIS and cyclic voltammetry (CV) in 10–1 M LiClO4 solution containing various redox probes. The impedance spectra were recorded at the formal redox potential of the redox probes. The charge transfer resistance (Rct), solution resistance (Rs), exchange current density (i0), standard rate constant (k0), and double-layer capacitance (Cdl) were calculated from the EIS data.

High-Temperature Performance of Amorphous Nickel Hydroxide Coated with La(OH)3

2011 ◽  
Vol 311-313 ◽  
pp. 1365-1369
Author(s):  
Chang Jiu Liu ◽  
Mei Rong Qi ◽  
Chun Xiao Xing
Keyword(s):  
High Temperature ◽  
Nickel Hydroxide ◽  
Electrochemical Impedance ◽  
Electrochemical Performances ◽  
X Ray Diffraction ◽  
Transfer Resistance ◽  
X Ray ◽  
Temperature Performance ◽  
Chemical Coprecipitation Method ◽  
Electron Transfer Resistance

La(OH)3coated amorphous nickel hydroxide was prepared by chemical coprecipitation method. The microstructure, surface morphology and chemical composition of the prepared sample were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). Electrochemical performances of the sample were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge/discharge measurements. The results demonstrated that the coating of La(OH)3 dramatically decreased electron transfer resistance and increased oxygen evolution potential of amorphous nickel hydroxide. Moreover, the high-temperature performance of amorphous nickel hydroxide was significantly improved after the coating of La(OH)3.

Effect of Morphology of Conducting Polymer on DNA Sensing

2011 ◽  
Vol 700 ◽  
pp. 211-214
Author(s):  
Bhuvaneswari Kannan ◽  
David E. Williams ◽  
Jadranka Travas-Sejdic
Keyword(s):  
Electron Transfer ◽  
Electrode Surface ◽  
Electrochemical Impedance ◽  
Charge Transfer Resistance ◽  
Electron Charge ◽  
Dna Sensors ◽  
Transfer Resistance ◽  
Electron Charge Transfer ◽  
Kinetics Of ◽  
Biosensor Applications

Electrochemical DNA sensors can be constructed by understanding basic interfacial electron transfer between solid surface-electrolyte-DNA interfaces. The kinetics of this heterogeneous process can be significantly affected by the microstructure and roughness of the electrode surface. By understanding this concept, in this paper; we compared the performance of micro electrodes containing poly(Py-co-PAA) with macro electrode containing same copolymer, showing that micro electrodes are more sensitive than the macro electrodes for biosensor applications. Sensors based on the copolymer electropolymerised on both micro and macro electrodes were evaluated across a range of oligonucleotide concentrations. The interfacial electron charge transfer resistance between the solution and electrode surface was studied using electrochemical impedance spectroscopy (EIS).

scholarly journals Electrochemical Impedance Spectroscopy Microsensor Based on Molecularly Imprinted Chitosan Film Grafted on a 4-Aminophenylacetic Acid (CMA) Modified Gold Electrode, for the Sensitive Detection of Glyphosate

2021 ◽  
Vol 9 ◽  
Author(s):  
Fares Zouaoui ◽  
Saliha Bourouina-Bacha ◽  
Mustapha Bourouina ◽  
Albert Alcacer ◽  
Joan Bausells ◽  
...  
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Gold Electrode ◽  
High Selectivity ◽  
Electrochemical Impedance ◽  
Chitosan Film ◽  
Molecularly Imprinted ◽  
Cyclic Voltammetry Measurement ◽  
Scanning Electron

A novel electrochemical impedance spectroscopy (EIS) microsensor was implemented for the dosage of traces of glyphosate, in real and synthetic water samples. Molecularly imprinted chitosan was covalently immobilized on the surface of the microelectrode previously modified with 4-aminophenylacetic acid (CMA). The characterization of the resulting microelectrodes was carried out by using cyclic voltammetry measurement (CV), scanning electron microscopy (SEM), and electrochemical impedance spectrometry (EIS). EIS responses of the CS-MIPs/CMA/Au microsensor toward GLY was well-proportional to the concentration in the range from 0.31 × 10−9 to 50 × 10−6 mg/mL indicating a good correlation. The detection limit of GLY was 1 fg/mL (S/N = 3). Moreover, this microsensor showed good reproducibility and repeatability, high selectivity, and can be used for the detection of GLY in river water.

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