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Silver Electrode (silver + electrode)
Selected AbstractsElectrochemical Detection of Anions on an Electrophoresis Microchip with Integrated Silver ElectrodeELECTROANALYSIS, Issue 13 2005Jilin Yan Abstract A poly(dimethylsiloxane)/glass hybrid microfluidic chip with integrated silver electrode is described for electrochemical detection of anions. The working electrode was directly fabricated on a glass slide and the chip formed by reversibly sealing of a PDMS slab with microchannels to the slide. Under an alkaline phosphate condition, thiocyanide and three halides were sensitively detected. Factors influencing the separation and detection procedure were discussed and optimized. Linear responses over two magnitudes were obtained with limit of detection at the micromolar level. [source] Determination of Lead and Cadmium at Silver Electrode by Subtractive Anodic Stripping Voltammetry in Plant Materials Containing TlELECTROANALYSIS, Issue 9 2005Beata Krasnod, bska-Ostr Abstract Lead and cadmium have been determined by the subtractive anodic stripping voltammetry using the square-wave mode at a silver electrode without removal of oxygen. The samples containing large amount of thallium were collected from a highly contaminated region. The presence of thallium strongly affects the peak shape of Cd. The plant material digestion was performed with HNO3/HClO4 mixture using pressurised microwave decomposition. The proposed method used for the lead determination was validated by the inter-method comparison (ICP-MS). The cadmium determination was validated using certified reference material. The results obtained, supported by statistical tests, demonstrated the usefulness of the method for the lead determination in samples containing large amounts of Cd and Tl. It is important to note that Cd can only be quantified when the thallium concentration is much lower than that of cadmium. [source] Electrochemical Detection of Anions on an Electrophoresis Microchip with Integrated Silver ElectrodeELECTROANALYSIS, Issue 13 2005Jilin Yan Abstract A poly(dimethylsiloxane)/glass hybrid microfluidic chip with integrated silver electrode is described for electrochemical detection of anions. The working electrode was directly fabricated on a glass slide and the chip formed by reversibly sealing of a PDMS slab with microchannels to the slide. Under an alkaline phosphate condition, thiocyanide and three halides were sensitively detected. Factors influencing the separation and detection procedure were discussed and optimized. Linear responses over two magnitudes were obtained with limit of detection at the micromolar level. [source] Determination of Lead and Cadmium at Silver Electrode by Subtractive Anodic Stripping Voltammetry in Plant Materials Containing TlELECTROANALYSIS, Issue 9 2005Beata Krasnod, bska-Ostr Abstract Lead and cadmium have been determined by the subtractive anodic stripping voltammetry using the square-wave mode at a silver electrode without removal of oxygen. The samples containing large amount of thallium were collected from a highly contaminated region. The presence of thallium strongly affects the peak shape of Cd. The plant material digestion was performed with HNO3/HClO4 mixture using pressurised microwave decomposition. The proposed method used for the lead determination was validated by the inter-method comparison (ICP-MS). The cadmium determination was validated using certified reference material. The results obtained, supported by statistical tests, demonstrated the usefulness of the method for the lead determination in samples containing large amounts of Cd and Tl. It is important to note that Cd can only be quantified when the thallium concentration is much lower than that of cadmium. [source] Controllable Molecular Doping and Charge Transport in Solution-Processed Polymer Semiconducting LayersADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Yuan Zhang Abstract Here, controlled p-type doping of poly(2-methoxy-5-(2,-ethylhexyloxy)- p -phenylene vinylene) (MEH-PPV) deposited from solution using tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) as a dopant is presented. By using a co-solvent, aggregation in solution can be prevented and doped films can be deposited. Upon doping the current,voltage characteristics of MEH-PPV-based hole-only devices are increased by several orders of magnitude and a clear Ohmic behavior is observed at low bias. Taking the density dependence of the hole mobility into account the free hole concentration due to doping can be derived. It is found that a molar doping ratio of 1 F4-TCNQ dopant per 600 repeat units of MEH-PPV leads to a free carrier density of 4,×,1022,m,3. Neglecting the density-dependent mobility would lead to an overestimation of the free hole density by an order of magnitude. The free hole densities are further confirmed by impedance measurements on Schottky diodes based on F4-TCNQ doped MEH-PPV and a silver electrode. [source] Adsorption of 4,4,-thiobisbenzenethiol on silver surfaces: surface-enhanced Raman scattering studyJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2008Yuling Wang Abstract Adsorption of 4,4,-thiobisbenzenethiol (4,4,-TBBT) on a colloidal silver surface and a roughened silver electrode surface was investigated by means of surface-enhanced Raman scattering (SERS) for the first time, which indicates that 4,4,-TBBT is chemisorbed on the colloidal silver surface as dithiolates by losing two H-atoms of the SH bond, while as monothiolates on the roughened silver electrode. The different orientations of the molecules on both silver surfaces indicate the different adsorption behaviors of 4,4,-TBBT in the two systems. It is inferred from the SERS signal that the two aromatic rings in 4,4,-TBBT molecule are parallel to the colloidal silver surface as seen from the disappearance of ,CH band (3054 cm,1), which is a vibrational mode to be used to determine the orientation of a molecule on metals according to the surface selection rule, while on the roughened silver electrode surface they are tilted to the surface as seen from the enhanced signal of ,CH. The orientation of the C-S bond is tilted with respect to the silver surface in both cases as inferred from the strong enhancement of the ,CS. SERS spectra of 4,4,-TBBT on the roughened silver electrode with different applied potentials reveal that the enhancement of 4,4,-TBBT on the roughened silver electrode surface may be related to the chemical mechanism (CM). More importantly, the adsorption of 4,4,-TBBT on the silver electrode is expected to be useful to covalently adsorb metal nanoparticles through the free SH bond to form two- or three- dimensional nanostructures. Copyright © 2007 John Wiley & Sons, Ltd. [source] In situ Raman spectra of an NAD+ -modified silver electrode at various potentialsJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2004Haifeng Yang Abstract At various potentials, the in situ confocal Raman technique was employed to detect SERS signals from a silver electrode surface modified with NAD+ through a self-assembled monolayer (SAM) method. The SERS bands of the NAD+ molecule are much more sensitive to changes in the applied potential compared with experimental results reported previously. It is demonstrated in detail that the NAD+ molecules undergo reorientation at or desorption from the silver electrode surface with a potential shift from ,0.5 to 0.0 V vs a saturated calomel electrode based on a charge-transfer mechanism for explanation of the SERS signals. The effect of buffer electrolytes on the results of the SERS experiment was also investigated. Copyright © 2004 John Wiley & Sons, Ltd. [source] Failure Mechanism of a Low-Temperature-Cofired Ceramic Capacitor with an Inner Ag ElectrodeJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010Yi-Ting Shih Failure mechanism of a multilayer ceramic capacitor (MLCC) made of a low-fire BaNd2Ti4O12(BNT)+ZnO,B2O3 (ZB) dielectric with an inner pure silver electrode at elevated temperatures and voltages has been investigated. A nonlinear current,voltage leakage characteristic is found when the degradation of MLCC occurs, and the time to failure decreases with increasing either the temperature or the voltage. Results of microstructure, composition, and impedance analyses reveal that the failure is caused by silver diffusion in the ZB glass during sintering and highly accelerated life test. [source] Surface-enhanced Raman difference between bombesin and its modified analogues on the colloidal and electrochemically roughen silver surfacesBIOPOLYMERS, Issue 10 2008Edyta Podstawka Abstract In this article, surface-enhanced Raman scattering (SERS) spectra of bombesin (BN) and its six modified analogues ([D-Phe12]BN, [Tyr4]BN, [Tyr4,D-Phe12]BN, [D-Phe12,Leu14]BN, [Leu13 -®-Leu14]BN, and [Lys3]BN) on a colloidal silver surface are reported and compared with SERS spectra of these species immobilized onto an ellectrochemically roughen silver electrode. Changes in enhancement and wavenumber of proper bands upon adsorption on different silver surfaces are consistent with BN and its analogues adsorption primarily through Trp8. Slightly different adsorption states of these molecules are observed depending upon natural amino acids substitution. For example, the indole ring in all the peptides interacts with silver nanoparticles in a edge-on orientation. It is additionally coordinated to the silver through the N1H bond for all the peptides, except [Phe12]BN. This is in contrary to the results obtained for the silver roughen electrode that show direct but not strong N1H/Ag interaction for all peptides except [D-Phe12,Leu14]BN and [Leu13 -®-Leu14]BN. For BN only CO is not involved in the chemical coordination with the colloidal surface. [Lys3]BN and BN also adsorb with the CN bond of NH2 group normal and horizontal, respectively, to the colloidal surface, whereas CNH2 in other peptides is tilted to this surface. Also, the Trp8 CH2 moiety of only [Tyr4]BN, [Lys3]BN, and [Tyr4,D-Phe12]BN coordinates to Ag, whereas the Phe12 ring of [Phe12]BN, [Tyr4,D-Phe12]BN, and [D-Phe12,Leu14]BN assists in the peptides binding only on the colloidal silver. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 807,819, 2008. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] New Anthraquinone Derivatives as Electrochemical Redox Indicators for the Visualization of the DNA Hybridization ProcessELECTROANALYSIS, Issue 1 2010Agata Kowalczyk Abstract Interactions of dsDNA and ssDNA, at the surface of gold and silver electrodes, with three novel anthraquinone derivatives: 3-(9,,10,-dioxo-9,,10,-dihydro-anthracen-1-yl)-7,11-di(carboxymethyl)-3,7,11-triazatridecanedioic acid, (AQ-1); 1-(9,,10,-dioxo-9,,10,-dihydro-anthracen-1yl)-9-carboxymethyl-5-methyl-1,5,9-triazaundecanoicacid, (AQ-2); and N -(2-(9,10-dioxo-9,10-dihydro-anthracen-1-ylamino)ethyl)-2-(1,4,10,13-tetraoxa-7,16-diazacyclooctadecan-7-yl)acetamide, (AQ-3) are studied. These derivatives are well soluble in water and phosphate buffer solutions. The square wave voltammetric behavior of these redox indicators is described and the parameters of interactions with DNA are reported. It is also pointed out that these compounds can be employed as the hybridization indicators. The difference in the binding ability of the particular redox indicator to single and double stranded DNA can be used for the detection of the complementary nucleic acids. [source] Amalgam Electrodes for ElectroanalysisELECTROANALYSIS, Issue 8 2003Řyvind Mikkelsen Abstract Liquid mercury is a unique material for the indicator electrode in voltammetry. One reason for this is the high overvoltage for hydrogen formation, thus extending the actual potential window. Diluted amalgams are important reaction products in voltammetric (polarographic) processes, however liquid amalgams are rarely used directly as electrode material for analytical purposes. Because of the fact that voltammetry is very suitable for field and remote monitoring, issues concerning the use of mercury electrodes in environmental analyses have led to considerable research effort aimed at finding alternative tools with acceptable performance. Solid electrodes are such alternatives. Different types of electrodes are reviewed. In particular, solid amalgam electrodes are very promising, with acceptable low toxicity to be used for field measurements. Solid amalgam electrodes are easy and cheap to construct and are stable over a reasonable time up to several weeks. Assessment of the toxicity risk and the long time stability for remote and unattended monitoring is discussed. The differences between solid dental amalgam electrodes, made by using techniques known from dental clinical practice, and mercury film or mercury layer electrodes on solid substrates are reviewed. In particular the dental technique for constructing solid amalgam electrodes gives advantage because it's fast and inexpensive. Also the technique for making dental amalgam has been explored and optimized over years by dentists, giving advantage when the same technique is used for constructing electrodes. Dental amalgam electrodes has been found to act similar to a silver electrodes, but with high overvoltage towards hydrogen. This make it possible to use the dental amalgam electrode for detection of zinc, cobalt and nickel in additions to other metals like lead, copper, thallium, cadmium, bismuth, iron etc. Also the use for reducible organic compounds is expected to be promising. [source] Microchip electrophoresis in low-temperature co-fired ceramics technology with contactless conductivity measurementELECTROPHORESIS, Issue 14 2009Georg Fercher Abstract In this paper a novel micromachined contactless conductivity CE device produced in low temperature co-fired ceramics (LTCC) is introduced. The application of LTCC multilayer technology provides a promising method for the contactless detection of conductive compounds because of its increased dielectric constant compared with glass or plastics. The capacitive coupling of the excitation signal into the microchannel across the LTCC substrate is improved, resulting in better detection sensitivity. Two silver electrodes located externally at opposite sides at the end of the separation channel act as detector. Impedance variations in the channel are measured without galvanic contact between electrodes and fluid. Inorganic ions are separated in less than 1,min with this novel ceramic device. The limit of detection is 10,,M for potassium. [source] Dielectric Properties of a Printed Sol,Gel Matrix Composite,ADVANCED ENGINEERING MATERIALS, Issue 5 2010Tobias Lehnert Low temperature processable materials with high dielectric constants are required for application on flexible organic substrates, for example, in printed electronics. To date, mainly organic polymers with embedded functional particles have been investigated for this purpose. For the first time, we present a printable dielectric composite material composed of ferroelectric high permittivity particles (BaTiO3) bonded by a mainly inorganic sol,gel derived network. The exemplary optimization of the properties by varying the sol,gel precursor illustrates the potential of sol,gel chemistry for printable functional materials. An operational gravure printed capacitor including printed silver electrodes is presented. The measured dielectric constants are among the highest reported in literature for low temperature cured films with moderate dissipation factors. Besides these promising dielectric properties, this composite film shows a ferroelectric response. [source] Effects of (-)bicuculline and gamma-aminobutyric acid on the NiCl2 mediated stimulation of the ERG b-wave amplitude from the isolated superfused vertebrate retinaACTA OPHTHALMOLOGICA, Issue 2007T SCHNEIDER Purpose: NiCl2 (15 ,M) stimulates the b-wave amplitude of vertebrate retina, up to 1.5-fold through its blocking of E/R-type voltage-gated Ca2+ channels. Assuming that these channels may trigger the release of the inhibitory neurotransmitter GABA, we tested the effect of (-)bicuculline and GABA itself. Methods: We have used a superfused vertebrate retina assay, testing retina from bovine (Lüke et al., 2005: Brain Res Brain Res Protoc 16 : 27-36). The retina was separated from the underlying pigment epithelium and mounted on a mesh occupying the center of the perfusing chamber. The electroretinogram was recorded in the surrounding nutrient medium via two silver/silver-chloride electrodes on either side of the retina. The recording chamber containing a piece of retina was placed in an electrically and optically insulated air thermostat. The retina was dark-adapted and the electroretinogram was elicited at intervals of five min using a single white flash for stimulation. Results: (-)Bicuculline increased the b-wave amplitude to a similar extent as observed in parallel recordings for low NiCl2 (15 ,M). The GABA effect was biphasic, and let to a transient stimulation after NiCl2 application. Those retina segments which did not respond to NiCl2 (15 ,M), also could not be stimulated by bicuculline and vice versa. Conclusions: The stimulatory effect of NiCl2 on the ERG b-wave amplitude is mediated by a NiCl2-sensitive, probably Cav2.3 / voltage-gated Ca2+-channel triggered GABA-release, and GABA itself may act on at least two different receptors. [source] | |||||||||||||