Nanosized magnetite and nafion modified gold wire electrode for electrochemical monitoring of nitrite in water

Using the gold wire and cotton wick electrodes, the electroretinograms of mice and rats were measured, and then they were compared. The results obtained were as follows: 1) There were no remarkable differences in the latencies and amplitudes of a- and b-waves, amplitudes and numbers of waves of oscillatories between two different electrodes. 2) It was easy to make and maintain the gold wire electrode as compared with the cotton wick electrode. From these results, it appears that the gold wire electrode is useful for measuring the electroretinogram of small laboratory animals.

Electrochemical impedance spectroscopy study of Concanavalin A binding to self-assembled monolayers of mannosides on gold wire electrodes

Sensors that detect NO x by a change in impedance were fabricated with gold wire electrodes and YSZ electrolyte. The effects of temperature, NO x species, flow rate, and cross sensitivity to O2 were quantified and evaluated. The largest phase angle shift due to NO x was found at the lowest temperature investigated (600 °C). Linear relationships existed between the shift in phase angle and NO x quantity up to 100 ppm. NO2 evoked a larger response than NO at 650 °C. A reversible poisoning effect was observed following exposure to NO2. The sensing impedance signal at 10 Hz was invariant to total flow rate. Cross sensitivity to O2 was noted. Although O2 evoked a much smaller response than NO x , the larger quantity of O2 of lean exhaust necessitated compensation.

We report a facile electrosynthesis (constant current of 0.5 mA) of gold-curcumin (Au-CM) nanocomposite using a gold wire (anode) and glassy carbon electrode (cathode, GCE) in a solution of curcumin. A thin and stable film of the nanocomposite was deposited on the GCE in 30 minutes. Extensive morphological and structural characterizations were carried out by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and BET analysis, which confirmed the formation of gold nanoparticles enveloped by a porous network of curcumin. Hydrogen evolution reaction (HER) was carried out in an aqueous solution of 0.5 M sulfuric acid with the modified GCEs. Enhanced hydrogen evolution activity was observed with Au-CM/GCE by a reduction in potential from -0.43 V (Au/GCE) to -0.32 V (Au-CM/GCE) (vs. Ag/AgCl: RE) with a 2-fold increase in current density compared to bare gold. A decrease in charge transfer resistance (9.13 kΩ to 82.6 Ω) was observed with the rise in cathodic potential from (-0.3 V to -0.48 V) at Au-CM/GCE, implying the facile nature of reaction at higher potential due to faster electron flow across the electrode-electrolyte interface. This is the first report wherein the curcumin network in the Au-CM nanocomposite aids in reducing 110 mV potential during the HER compared to bare Au. Figure 1

We use substituted polyanilines for the construction of new polymer electrodes for interaction studies with the redox protein cytochrome c (cyt c) and the enzyme sulfite oxidase (SO). For these purposes four different polyaniline copolymers are chemically synthesized. Three of them are copolymers, containing 2-methoxyaniline-5-sulfonic acid with variable ratios of aniline; the fourth copolymer consists of 3-amino-benzoic acid and aniline. The results show that all polymers are suitable for being immobilized as thin stable films on gold wire and indium tin oxide (ITO) electrode surfaces from DMSO solution. This can be demonstrated by cyclic voltammetry and UV-Vis spectroscopy measurements. Moreover, cyt c can be electrochemically detected not only in solution, but also immobilized on top of the polymer films. Furthermore, the appearance of a significant catalytic current has been demonstrated for the sulfonated polyanilines, when the polymer-coated protein electrode is being measured upon addition of sulfite oxidase, confirming the establishment of a bioanalytical signal chain. Best results have been obtained for the polymer with highest sulfonation grade. The redox switching of the polymer by the enzymatic reaction can also be analyzed by following the spectral properties of the polymer electrode.

We use substituted polyanilines for the construction of new polymer electrodes for interaction studies with the redox protein cytochrome c (cyt c) and the enzyme sulfite oxidase (SO). For these purposes four different polyaniline copolymers are chemically synthesized. Three of them are copolymers, containing 2-methoxyaniline-5-sulfonic acid with variable ratios of aniline; the fourth copolymer consists of 3-amino-benzoic acid and aniline. The results show that all polymers are suitable for being immobilized as thin stable films on gold wire and indium tin oxide (ITO) electrode surfaces from DMSO solution. This can be demonstrated by cyclic voltammetry and UV-Vis spectroscopy measurements. Moreover, cyt c can be electrochemically detected not only in solution, but also immobilized on top of the polymer films. Furthermore, the appearance of a significant catalytic current has been demonstrated for the sulfonated polyanilines, when the polymer-coated protein electrode is being measured upon addition of sulfite oxidase, confirming the establishment of a bioanalytical signal chain. Best results have been obtained for the polymer with highest sulfonation grade. The redox switching of the polymer by the enzymatic reaction can also be analyzed by following the spectral properties of the polymer electrode.

Multi-walled and single-walled carbon nanotubes were synthesized on platinum plate (MWCNTs/pt) and gold wire (SWCNTs/Au) electrodes, respectively, using a chemical vapor deposition (CVD) method. These carbon nanotube-modified electrodes were immersed into solutions of glucose oxidase (GOX) and D-fructose dehydrogenase (FDH) to immobilize these enzymes onto the electrode surfaces. After GOX was immobilized onto the MWCNT/Pt electrode, the well-defined catalytic oxidation current was increased from ca. -0.45 V (vs. Ag/AgCl/saturated KCl), which was close to the redox potential of flavin adenine dinucleotide as a prosthetic group of GOX under physiological pH values. Furthermore, catalytic oxidation currents of fructose based on direct heterogeneous electron transfer reactions between FDH and the SWCNT/Pt electrode were observed.

Electrochemical detection of vancomycin using aptamer - screen - printed carbon surfaces.

Preparation and molecular recognition of cyclodextrin monolayers with different cavity size on a gold wire electrode

A flexible and self-supported nanoporous gold wire electrode with a seamless structure for electrochemical ascorbic acid sensor

Electroporation is a technique with which DNA molecules can be delivered into cells in a chamber using high electric field pulses. The limited amount of target cells and the potential risk from the high voltage are the two drawbacks in this technique. This study aimed to fabricate an electroporation chip to manage large amount of cells continuously with a lower applied voltage. The electroporation chip, consisting of a micro-channel with thin film electrodes made of gold or platinum wire electrodes on both sides, was fabricated on PMMA material using evaporation, photolithography, wet- etching, lift-off, and fusion-bonding methods. The suspension fluid of Huh-7 cell lines (1 x 106 cells/ml) mixed with 10 micrometers plasmids equipped with lacZ genes in a volume of 500 (mu) l flowed through the channel with a variety of flow rates under a series of square pulses. The transfection rate was evaluated with blue-staining cells under X-Gal stain 24 hours later. The dimensions of the channel were 5 mm wide, 0.2 mm high, and 25 mm long. Two types of electrodes, parallel-plate type and parallel-line type electrodes, were fabricated and tested in these experiments. The fabricated microchip can deliver genes into the flowing of cells. The electric pulse frequency that determines the shock number for each cell for a fixed flow rate can be optimized for better transfection and survival rates.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The development of polypyrrole as a potential mediator membrane candidate for sodium dodecyl sulfate (SDS) sensor electrode has been investigated. The polypyrrole membrane was synthesized electrochemically from the pyrrole and coated at the surface of a 1.0 mm diameter of the gold-wire electrode. Electropolymerization of pyrrole and coating of the polypyrrole produced was performed by cyclic voltammetry technique in the electrochemical cell containing supporting electrolyte of 0.01 M NaClO4 with an optimum potential range of -0.9 V–1.0 V, the scanning rate of 100 mV/s, an electric current of 2 mA, and running of potential scanning of 10 cycles. By using the similar optimal parameters of cyclic voltammetry, electropolymerization of 0.01 M pyrrole solution containing 0.001 M SDS also produces a polypyrrole membrane coated at the gold-wire electrode surface. These coated electrodes have the potential response-ability toward DS- anions in the concentration range of 10-7 M–10-5 M with a limit of detection of 10-7 M and sensitivity of electrode of 9.9 mV/decade. This finding shows that the SDS solution’s role is as supporting electrolyte and also as a source of DS- dopant during the pyrrole electropolymerization processes. Dopants are trapped in the polymer membrane during the electrochemical formation of polypyrrole and role as ionophores for DS- anion in the analyte solution. A potential response to the electrode phenomena is excellent basic scientific information for further synthesis of conducting polymer and development of conducting polymer-coated wire electrode model, especially in the construction of ion-selective electrode (ISE) for the determination of anionic surfactants with those models.

Cyclic voltammetric studies with gold wire electrodes covered with lipoyl γ-cyclodextrins: positional isomerism effect of the modified cyclodextrins on monolayer quality and electrochemical responses on soluble probes

Chronopotentiometry of Selenium(IV) ion in strong phosphoric acid

Electrocatalytic reduction of organic peroxides in organic solvents by microperoxidase-11 immobilized as a monolayer on a gold electrode