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Sample records for ag111 electrodes investigated

  1. The dissolution of Ag(111) electrodes investigated by in situ scanning tunnelling microscopy

    CERN Document Server

    Wilson, T K

    1998-01-01

    voltammetric methods. This remained evident for varying extents of silver dissolution. Ag(111) electrodes were oxidised in 0.1 M KCIO sub 4 solutions by a single swept ORC of 0.77x10 sup - sup 3 C cm sup - sup 2. The final rest potential of the Ag(111) working electrode was over the potential range of -36 mV to 114 mV versus the SCE where the silver islands of the reformed surface are believed to be unstable. Results show that a majority of silver islands of all sizes are stable with time, whereas the silver islands with irregular shapes tended to evolve to exhibit higher degrees of spherical geometry. Additionally, the position of the silver islands did not remain constant during the acquisition of STM images. Results from in situ STM demonstrated that the underlying step-terrace morphology of the Ag(111) electrodes did not remain constant with time. Both macroscale and nanoscale changes to the Ag(111) electrode surface were observed. It is concluded that this is due to the transport of material along and fr...

  2. Epitaxial growth of diindenoperylene ultrathin films on Ag(111) investigated by LT-STM and LEED.

    Science.gov (United States)

    Huang, Han; Sun, Jia-Tao; Feng, Yuan Ping; Chen, Wei; Wee, Andrew Thye Shen

    2011-12-21

    The epitaxial growth of the 1st and 2nd monolayer (ML) diindenoperylene (DIP) on Ag(111) has been systematically investigated using low temperature scanning tunneling microscopy, low energy electron diffraction and first-principles calculations. At one ML regime, DIP molecules commensurately arrange in either herringbone or brick-wall superstructures, depending on the deposition rate. Tip-induced structural transformation from herringbone to brick-wall is observed. Calculations based on density functional theory reveal that the top site of Ag(111) is energetically favorable for both superstructures. The 2nd ML DIP aggregate in either herringbone or brick-wall superstructures depending on the arrangements of the 1st ML DIP, indicating that the structural properties of DIP thin films on Ag(111) are sensitive to growth conditions. The observed variation in DIP ultrathin film structure may result in different electronic properties and have implications for DIP-based organic electronic devices, such as organic field-effect transistors or organic photovoltaic cells.

  3. Investigation of the electron dynamics at the PTCDA/Ag(111)-interface; Untersuchung der Elektronendynamik an der PTCDA-Ag (111) - Grenzflaeche

    Energy Technology Data Exchange (ETDEWEB)

    Schwalb, Christian

    2008-12-17

    In this work the electron dynamics at the PTCDA/Ag(111) interface have been studied with time- and angleresolved Two-photon photoemission (2PPE) as well as time-resolved photoluminescence (PL). The first part of this work concentrates on the characterization of an unoccupied electronic state, that develops 0.6 eV above the Fermi level due to the adsorption of the PTCDA molecules, whereas the shockley surface state of the clean surface vanishes. The measurements clearly identify this state as an interface state that is located between the metal surface and the first layer of the molecules. Dispersion measurements yield an effective mass of this state of 0.39 m{sub e} at the Gamma-point and show backfolding at the zone boundaries of the rectangular PTCDA unit cell. Time-resolved measurements show a surprisingly short lifetime of t=54 fs, clearly indicating a strong coupling of the state with the metal. This behaviour can be explained by a shift of the shockley surface state. This for the clean Ag(111)-surface normally occupied state shifts above the Fermi level because of the highly polarizable PTCDA molecules. Calculations with a one dimensional model potential support this interpretation. Angleresolved lifetime measurements as a function of parallel momentum show a correlation of the decay dynamics of the interface state with the measured bandstructure. The observed drop of the lifetime for larger parallel momentum is significantly smaller as expected for the pure shockley state. This behaviour can be explained due to a hybridisation of the shockley state with the LUMO+1 of the first PTCDA monolayer for k parallel >>0. The second part of this work deals with the intramolecular excitation at the PTCDA/Ag(111) interface after excitation with laser pulses with 2.33 eV and 4.66 eV photon energy. Time-resolved photoluminescence measurements show a strong rise in the PL-lifetime as a function of PTCDA coverage, that can be explained by an increase in the crystallinity of

  4. Low-temperature scanning tunneling microscopy/ultraviolet photoelectron spectroscopy investigation of two-dimensional crystallization of C60: pentacence binary system on Ag(111)

    Science.gov (United States)

    Lin Zhang, Jia; Hong Liang Zhang, Kelvin; Qiang Zhong, Jian; Chao Niu, Tian; Chen, Wei

    2012-02-01

    Atomic scale investigation of temperature-dependent two-dimensional (2 D) crystallization processes of fullerene-C60 on pentacene-covered Ag(111) surface has been carried out by in situ low-temperature scanning tunneling microscopy (LT-STM) experiments. To evaluate the effect of molecule-substrate interfacial interactions on the 2 D crystallization of C60: pentacene binary system, we also carried out the same self-assembly experiments of C60 on monolayer pentacene covered graphite substrate. It is revealed that temperature-dependent structural transition of various ordered C60 nanoassemblies is strongly influenced by the molecule-Ag(111) interfacial interactions, and further mediated by the weak C60-pentacene intermolecular interactions. In situ ultraviolet photoelectron spectroscopy (UPS) has been used to evaluate the nature of the intermolecular interactions between C60 and pentacene films.

  5. First-principles study of surface plasmons on Ag(111) and H/Ag(111)

    DEFF Research Database (Denmark)

    Yan, Jun; Jacobsen, Karsten Wedel; Thygesen, Kristian Sommer

    2011-01-01

    Linear-response time-dependent density functional theory is used to investigate the relation between molecular bonding and surface plasmons for the model system H/Ag(111). We employ an orbital-dependent exchange-correlation functional to obtain a correct description of the Ag 3d band, which is cr...

  6. Toward the microscopic identification of anions and cations at the ionic liquid|Ag(111) interface: a combined experimental and theoretical investigation.

    Science.gov (United States)

    Buchner, Florian; Forster-Tonigold, Katrin; Uhl, Benedikt; Alwast, Dorothea; Wagner, Nadja; Farkhondeh, Hanieh; Gross, Axel; Behm, R Jürgen

    2013-09-24

    The interaction between an adsorbed 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMP][TFSA], ionic liquid (IL) layer and a Ag(111) substrate, under ultrahigh-vacuum conditions, was investigated in a combined experimental and theoretical approach, by high-resolution scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and dispersion-corrected density functional theory calculations (DFT-D). Most importantly, we succeeded in unambiguously identifying cations and anions in the adlayer by comparing experimental images with submolecular resolution and simulated STM images based on DFT calculations, and these findings are in perfect agreement with the 1:1 ratio of anions and cations adsorbed on the metal derived from XPS measurements. Different adlayer phases include a mobile 2D liquid phase at room temperature and two 2D solid phases at around 100 K, i.e., a 2D glass phase with short-range order and some residual, but very limited mobility and a long-range ordered 2D crystalline phase. The mobility in the different adlayer phases, including melting of the 2D crystalline phase, was evaluated by dynamic STM imaging. The DFT-D calculations show that the interaction with the substrate is composed of mainly van der Waals and weak electrostatic (dipole-induced dipole) interactions and that upon adsorption most of the charge remains at the IL, leading to attractive electrostatic interactions between the adsorbed species.

  7. Adsorption of the ionic liquid [BMP][TFSA] on Au(111 and Ag(111: substrate effects on the structure formation investigated by STM

    Directory of Open Access Journals (Sweden)

    Benedikt Uhl

    2013-12-01

    Full Text Available In order to resolve substrate effects on the adlayer structure and structure formation and on the substrate–adsorbate and adsorbate–adsorbate interactions, we investigated the adsorption of thin films of the ionic liquid (IL 1-butyl-1-methylpyrrolidinium-bis(trifluoromethylsulfonylimide [BMP][TFSA] on the close-packed Ag(111 and Au(111 surfaces by scanning tunneling microscopy, under ultra high vacuum (UHV conditions in the temperature range between about 100 K and 293 K. At room temperature, highly mobile 2D liquid adsorbate phases were observed on both surfaces. At low temperatures, around 100 K, different adsorbed IL phases were found to coexist on these surfaces, both on silver and gold: a long-range ordered (‘2D crystalline’ phase and a short-range ordered (‘2D glass’ phase. Both phases exhibit different characteristics on the two surfaces. On Au(111, the surface reconstruction plays a major role in the structure formation of the 2D crystalline phase. In combination with recent density functional theory calculations, the sub-molecularly resolved STM images allow to clearly discriminate between the [BMP]+ cation and [TFSA]− anion.

  8. Monolayer solid of N-2/Ag(111)

    DEFF Research Database (Denmark)

    Bruch, L.W.; Hansen, Flemming Yssing

    1998-01-01

    An incommensurate monolayer solid of N-2/Ag(111) is modeled using extensive molecular-dynamics simulations. The conditions treated range from the low-temperature orientationally ordered solid to the melting of the solid. The properties are evaluated as a function of spreading pressure. Comparison...... is made to recent experimental data for N-2/Ag(111) and to results for N-2 adsorbed on graphite. Cu(110), and MgO(001). [S0163-1829(98)02715-5]....

  9. The role of the van der Waals interactions in the adsorption of anthracene and pentacene on the Ag(111) surface

    Science.gov (United States)

    Morbec, Juliana M.; Kratzer, Peter

    2017-01-01

    Using first-principles calculations based on density-functional theory (DFT), we investigated the effects of the van der Waals (vdW) interactions on the structural and electronic properties of anthracene and pentacene adsorbed on the Ag(111) surface. We found that the inclusion of vdW corrections strongly affects the binding of both anthracene/Ag(111) and pentacene/Ag(111), yielding adsorption heights and energies more consistent with the experimental results than standard DFT calculations with generalized gradient approximation (GGA). For anthracene/Ag(111) the effect of the vdW interactions is even more dramatic: we found that "pure" DFT-GGA calculations (without including vdW corrections) result in preference for a tilted configuration, in contrast to the experimental observations of flat-lying adsorption; including vdW corrections, on the other hand, alters the binding geometry of anthracene/Ag(111), favoring the flat configuration. The electronic structure obtained using a self-consistent vdW scheme was found to be nearly indistinguishable from the conventional DFT electronic structure once the correct vdW geometry is employed for these physisorbed systems. Moreover, we show that a vdW correction scheme based on a hybrid functional DFT calculation (HSE) results in an improved description of the highest occupied molecular level of the adsorbed molecules.

  10. Atomic structure of "multilayer silicene" grown on Ag(111): Dynamical low energy electron diffraction analysis

    Science.gov (United States)

    Kawahara, Kazuaki; Shirasawa, Tetsuroh; Lin, Chun-Liang; Nagao, Ryo; Tsukahara, Noriyuki; Takahashi, Toshio; Arafune, Ryuichi; Kawai, Maki; Takagi, Noriaki

    2016-09-01

    We have investigated the atomic structure of the "multilayer silicene" grown on the Ag(111) single crystal surface by using low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). We measured the intensity of the LEED spot as a function of the incident electron energy (I-V curve) and analyzed the I-V curve using a dynamical LEED theory. We have found that the Si(111)(√{ 3} ×√{ 3})-Ag model well reproduces the I-V curve whereas the models consisting of the honeycomb structure of Si do not. The bias dependence of the STM image of multilayer silicene agrees with that of the Si(111)(√{ 3} ×√{ 3})-Ag reconstructed surface. Consequently, we have concluded that the multilayer silicene grown on Ag(111) is identical to the Si(111)(√{ 3} ×√{ 3})-Ag reconstructed structure.

  11. Adsorption geometry and electronic properties of flat-lying monolayers of tetracene on the Ag(111) surface

    Science.gov (United States)

    Zaitsev, N. L.; Nechaev, I. A.; Höfer, U.; Chulkov, E. V.

    2016-10-01

    The geometrical and electronic properties of the monolayer (ML) of tetracene (Tc) molecules on Ag(111) are systematically investigated by means of DFT calculations with the use of a localized basis set. The bridge and hollow adsorption positions of the molecule in the commensurate γ -Tc/Ag(111) are revealed to be the most stable and equally favorable irrespective to the approximation chosen for the exchange-correlation functional. The binding energy is entirely determined by the long-range dispersive interaction. The former lowest unoccupied molecular orbital remains being unoccupied in the case of γ -Tc/Ag(111) as well as in the α phase with increased coverage. The unit cell of the α phase with point-on-line registry was adapted for calculations based on the available experimental data and computed structures of the γ phase. The calculated position of the Tc/Ag(111) interface state is found to be noticeably dependent on the lattice constant of the substrate, however its energy shift with respect to the Shockley surface state of the unperturbed clean side of the slab is sensitive only to the adsorption distance and in good agreement with the experimentally measured energy shift.

  12. Imaging and manipulation of a polar molecule on Ag(111)

    DEFF Research Database (Denmark)

    Lin, R.; Braun, K.F.; Tang, H.;

    2001-01-01

    A scanning tunneling microscope (STM) was applied to image and laterally manipulate isolated phosphangulene molecules on Ag(111) at 6 K. Atomic-resolution images clearly revealed three characteristic types of appearances (three-lobed, fish and bump shape) for the adsorbed molecules, which could c......! their manipulating processes can be much more complex in comparison with atoms and small molecules. Such information can shed light on the involved mechanisms on a molecular seals. (C) 2001 Published by Elsevier Science B.V....

  13. Atomic oxygen adsorption and absorption on Rh(111) and Ag(111)

    Science.gov (United States)

    Derouin, Jonathan D.

    A central question in the field of heterogeneous catalysis is how surface structure and subsurface species influence catalytic behavior. One key to answering that question is determining which surface structures and subsurface species are present under catalytically relevant conditions. This dissertation presents results of Auger electron spectroscopy, low energy electron diffraction, temperature programmed desorption, and scanning tunneling microscopy experiments on oxidized Rh(111) and Ag(111) crystals. Exposing Rh(111) to O2 produced a predominately (2 x 1) adlayer, but even after extended dosing, (2 x 2) domains were also present. Exposing Rh(111) to atomic oxygen yielded O coverages greater than 0.5 ML and (1 x 1) domains were observed to form along terrace step edges. However, (2 x 1) and (2 x 2) domains were still present. Atomic oxygen was used to oxidize Ag(111) in order to study the effect of sample temperature as well as oxygen flux and energy. When atomic oxygen was generated using a lower temperature thermal cracker, a variety of previously reported surface structures were observed. When O was generated using a higher filament temperature, the surface became highly corrugated, layers of Ag 2O appeared to form, and little subsurface oxygen was observed. To investigate the role of sample temperature, the Ag(111) sample was held at various temperatures while being exposed to atomic oxygen. For short doses, sample temperature had minimal effect on surface reconstruction. For longer doses, changes in sample temperature in the range of 490 K to 525 K had a substantial impact on surface reconstruction and subsurface oxygen absorption. Higher temperature dosing yielded the same surface structures which were observed after short doses. Lower temperature dosing with atomic oxygen resulted in subsurface oxygen formation and new structures which covered the surface. The results indicate the rich complexity of oxygen/transition metal interactions and illustrate how

  14. Incommensurate growth of Co thin film on close-packed Ag(111) surface

    Science.gov (United States)

    Barman, Sukanta; Menon, Krishna Kumar S. R.

    2016-05-01

    Growth of ultrathin Co layers on close-packed Ag(111)were investigated by means of Low Energy Electron Diffraction (LEED), X-ray Photoelectron Spectroscopy (XPS) and Angle-resolved Photoemission Spectroscopy(ARPES) techniques. The close-packed hexagonal face of Co(0001), exhibits a lattice misfit about 13% with Ag(111) surface which manipulates the growth to be incommensurate up to a certain thickness. The strain field causes aperiodic height undulation in the sub-angstrom regime of the film which was confirmed by p(1 × 1) LEED pattern along with a 6-fold moiré reconstruction pattern in the lower film thickness (up to ˜2ML). The evolution of the LEED pattern was studied with increasing film coverage. Lattice strain was measured with respect to the relative positions of these double spots as a functionof film thickness. Almost a constant strain (˜13%) in the full range of film thickness explains the moiré pattern formation in order to stabilize the incommensurate growth. For higher film coverages, an epitaxial well-ordered commensurate growth was observed. Core level and valance band electronic structures of these films were studied by XPS and ARPES techniques.

  15. From hydrogen bonding to metal coordination and back: Porphyrin-based networks on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Studener, F., E-mail: f.studener@rug.nl; Müller, K.; Stöhr, M., E-mail: m.a.stohr@rug.nl [Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG Groningen (Netherlands); Marets, N.; Bulach, V., E-mail: bulach@unistra.fr; Hosseini, M. W., E-mail: hosseini@unistra.fr [Laboratoire de Tectonique Moléculaire, UMR UDS-CNRS 7140, Université de Strasbourg, 4 rue Blaise Pascal, 67070 Strasbourg (France)

    2015-03-14

    The self-assembly of a metal-free porphyrin bearing two pyridyl coordinating sites and two pentyl chains at trans meso positions was investigated under ultrahigh vacuum on a Ag(111) surface by scanning tunneling microscopy (STM). The STM measurements revealed a well-ordered close-packed structure with a rhombic unit cell for coverages ≤1 monolayer with their molecular plane parallel to the surface. The growth direction of the molecular islands is aligned along the step edges, which are restructured due to molecule-substrate interactions. The shorter unit cell vector of the molecular superstructure follows the 〈1-10〉 direction of the Ag(111) substrate. Hydrogen bonds between pyridyl and pyrrole groups of neighboring molecules as well as weak van der Waals forces between the pentyl chains stabilize the superstructure. Deposition of cobalt atoms onto the close-packed structure at room temperature leads to the formation of a hexagonal porous network stabilized by metal-ligand bonding between the pyridyl ligands and the cobalt atoms. Thermal annealing of the Co-coordination network at temperatures >450 K results in the transformation of the hexagonal network into a second close-packed structure. Changes in the molecule-substrate interactions due to metalation of the porphyrin core with Co as well as intermolecular interactions can explain the observed structural transformations.

  16. 2D vibrational properties of epitaxial silicene on Ag(111)

    Science.gov (United States)

    Solonenko, Dmytro; Gordan, Ovidiu D.; Le Lay, Guy; Sahin, Hasan; Cahangirov, Seymur; Zahn, Dietrich R. T.; Vogt, Patrick

    2017-03-01

    The two-dimensional silicon allotrope, silicene, could spur the development of new and original concepts in Si-based nanotechnology. Up to now silicene can only be epitaxially synthesized on a supporting substrate such as Ag(111). Even though the structural and electronic properties of these epitaxial silicene layers have been intensively studied, very little is known about its vibrational characteristics. Here, we present a detailed study of epitaxial silicene on Ag(111) using in situ Raman spectroscopy, which is one of the most extensively employed experimental techniques to characterize 2D materials, such as graphene, transition metal dichalcogenides, and black phosphorous. The vibrational fingerprint of epitaxial silicene, in contrast to all previous interpretations, is characterized by three distinct phonon modes with A and E symmetries. Both, energies and symmetries of theses modes are confirmed by ab initio theory calculations. The temperature dependent spectral evolution of these modes demonstrates unique thermal properties of epitaxial silicene and a significant electron-phonon coupling. These results unambiguously support the purely two-dimensional character of epitaxial silicene up to about 300 °C, whereupon a 2D-to-3D phase transition takes place. The detailed fingerprint of epitaxial silicene will allow us to identify it in different environments or to study its modifications.

  17. Sb-enhanced nucleation in the homoepitaxial growth of Ag(111)

    NARCIS (Netherlands)

    van der Vegt, H.A.; Meijer, J.A.; Vrijmoeth, J; Behm, R.J.; Vlieg, E.

    1998-01-01

    The effect of Sb on the homoepitaxial growth mode of a Ag(111) surface has been studied by scanning tunneling microscopy. In a previous paper we reported on the effect of Sb on the interlayer diffusion barrier of Ag(111). Here we describe in more detail the effect of Sb on the island nucleation and

  18. Comparative Study of Hypophosphite H2PO2- Adsorption on Ni(111) and Ag(111) Surfaces by DFT

    Institute of Scientific and Technical Information of China (English)

    ZENG,Yue; OU,Li-Hui; LI,Ze-Lin; XIAO,Xiao-Ming; XIA,Shao-Xi

    2007-01-01

    Surface structures and electronic properties of hypophosphite H2PO2- on Ni(111) and Ag(111) surfaces were investigated by means of density functional theory at B3LYP/6-31 + +G(d,p) level. The most stable structure was that in which the H2PO2- adsorbs with its two P-O bonds faced to the substrate surface. The results of the Mulliken population analysis showed that because of the subtle difference of electron configuration, the adsorption energy was larger on the Ni surface than on the Ag surface, and the amounts of both donation and back donation were larger on the Ni(111) surface than on the Ag(111) surface. There were more negative Mulliken charge transfer from H2PO2- to substrate clusters on Ni surface than on Ag surface and more positive Mulliken charges on P atom in Ni4H2PO2- than in Ag4H2PO2-, which means that P atom in Ni4H2PO2- is easily attacked by a nucleophile such as OH-. Thus, H2PO2- is more easily oxidated on Ni(111) surface than on Ag(111) suface. These results indicated that the silver surface is inactive for the oxidation reaction of the hypophosphite anion.

  19. Cobalt monolayer islands on Ag(111) for ORR catalysis.

    Science.gov (United States)

    Loglio, Francesca; Lastraioli, Elisa; Bianchini, Claudio; Fontanesi, Claudio; Innocenti, Massimo; Lavacchi, Alessandro; Vizza, Francesco; Foresti, Maria Luisa

    2011-08-22

    The design of a catalyst for one of the most important electrocatalytic reactions, the oxygen reduction reaction (ORR), was done following the most recent guidelines of theoretical studies on this topic. Aim of this work was to achieve a synergic effect of two different metals acting on different steps of the ORR. The catalytic activity of Ag, already known and characterized, was enhanced by the presence of a monolayer of cobalt subdivided into nanosized islands. To obtain such a controlled nanostructure, a novel method utilizing self-assembled monolayers (SAMs) as templates was employed. In a recent study, we were able to perform a confined electrodeposition of cobalt onto Ag(111) in a template formed by selectively desorbing a short-chain thiol (3-mercaptopropionic acid, MPA) from binary SAMs using 1-dodecanthiols (DDT). This method allows for an excellent control of the morphology of the deposit by varying the molar ratio of the two thiols. Because cobalt does not deposit on silver at an underpotential, the alternative approach of surface limited redox replacement (SLRR) was used. This method, recently developed by Adžić et al., consists of the use of a monolayer of a third metal, which can be deposited at an underpotential, as a template for the spontaneous deposition of a more noble metal. Herein, we choose zinc as template for the deposition of cobalt. Ag(111) crystals were covered by monolayer islands consisting of cobalt, with the surface atomic ratios ranging from 12 to 39% for cobalt. The catalytic activity of such samples towards ORR was evaluated and the best improvement in activity was found to be that of the sample with a cobalt percentage of approximately 30% with respect to the bare silver, which is in good agreement with theoretical hypotheses.

  20. Polymorphism in Self-Assembled Structures of 9-Anthracene Carboxylic Acid on Ag(111

    Directory of Open Access Journals (Sweden)

    Bo Xu

    2012-06-01

    Full Text Available Surface self-assembly process of 9-anthracene carboxylic acid (AnCA on Ag(111 was investigated using STM. Depending on the molecular surface density, four spontaneously formed and one annealed AnCA ordered phases were observed, namely a straight belt phase, a zigzag double-belt phase, two simpler dimer phases, and a kagome phase. The two high-density belt phases possess large unit cells on the scale length of 10 nm, which are seldom observed in molecular self-assembled structures. This structural diversity stems from a complicated competition of different interactions of AnCA molecules on metal surface, including intermolecular and molecular-substrate interactions, as well as the steric demand from high molecular surface density.

  1. Germanium adsorption on Ag(111): an AES-LEED and STM study.

    Science.gov (United States)

    Oughaddou, H; Mayne, A; Aufray, B; Bibérian, J P; Le Lay, G; Ealet, B; Dujardin, G; Kara, A

    2007-09-01

    The adsorption of germanium on Ag(111) has been investigated using Scanning Tunneling Microscopy, Auger Electron Spectroscopy and Low Energy Electron Diffraction. From the shape of the Auger peak-to-peak versus time curves, we deduce that at room temperature the growth mode is nearly layer-by-layer at least for the first two layers. In the sub-monolayer range, the growth starts by the formation of a (mean square root of 3 x mean square root of 3)R30 degrees surface superstructure which is complete at 1/3 monolayer coverage. Beyond this coverage a rectangular c(mean square root of 3 x 7) superstructure is observed. STM images reveal that this last reconstruction is formed by an ordered arrangement of self-assembled Ge tetramers giving rise to a surprising undulation of the surface.

  2. A Study of Surfactant-Induced Growth of Ag on Ag (111)

    Institute of Scientific and Technical Information of China (English)

    WU Li-Li; HU Juan-Mei; WU Feng-Min

    2008-01-01

    A new growth model is introduced to describe surfactant-induced growth of Ag on Ag (111) with realistic physical parameters. In this model, the A-S exchange mechanism is considered for the first time. Using the Monte Carlo simulations, the influence of exchange mechanism, surface temperature T, the exchange barrier Eex, and the coverage of surfactant θM on the growth mode and morphology during multilayer film growth of Ag/Ag (111) are studied in detail. Both the referenced value of surfactant coverage and the method to obtain perfect layer-by-layer film in surfactant-induced Ag/Ag (111) system are provided. Our simulation results are consistent with many experimental observations for surfactant-induced growth of Ag on Ag (111).

  3. Adsorbate-induced facetting reconstruction and self-organized domain patterning of vicinal Ag(111) surfaces; Adsorbatinduzierte richtungsabhaengige Facettierung und selbstorganisierte Domaenen-Musterbildung auf vizinalen Ag(111)-Oberflaechen

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, Stefan

    2007-02-05

    This thesis investigates structural aspects of adsorbate-induced facetting of vicinal Ag(111) surfaces. It is mainly based on scanning tunneling microscope (STM) and low energy electron diffraction (LEED) experiments performed under UHV conditions. The planar dye-molecule perylene-3,4,9,10-tetracarboxilicacid-dianhydride (PTCDA) adsorbs preferentially at the step edges of the 8.5 Ag(111) vicinal surfaces used in the experiments. It causes a facetting reconstruction by the formation of (111) terraces and facets with a high step density. Moreover, two distinct preferential inclinations of facets were observed, which can only be explained by the selective influence of the adsorbate superstructure. In terms of thermodynamics, the facetting reconstruction can be described as an orientational phase separation, adapted to the constraints of planar surfaces. This concept is capable of explaining the local facetting phenomena. The formalism used predicts an important role of nucleation kinetics. This aspect is taken into account by introducing an additional phase of mobile molecules (2D molecular gas), which cannot be measured directly. Furthermore, strong arguments for the appearance of a critical island size for the PTCDA/ Ag(111) superstructure were found. This work presents structural information of all stable superstructures of PTCDA on vicinal Ag(111) surfaces. Altogether 16 such superstructures were found, 3 of which had been observed and published before. Density and commensurability were found to systematically depend on the step-structure. The two preferred inclinations of facets are related to two characteristic types of domain boundaries of the herringbone superstructure to the adjacent (111)-terrace. On the (111) terraces, small islands of metastable superstructures were found. Facets and (111) terraces form a regular grating-like domain pattern with a variable structural width of 5 to 75 nm. STM measurements show direct evidence for a long-range interaction

  4. Controllable molecular registration state in self-assembly of 3(5)-(9-anthryl)pyrazole molecule on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Dou, Ruifen; Tilkorn, Arno; Zhong, Dingyong; Wang, Wenchong; Chi, Lifeng; Fuchs, Harald [Physikalisches Institut, Universitaet Muenster, 48149 Muenster (Germany); Wang, Yue [Key Laboratory for Supramolecular Structure and Materials of Ministry of Education, Jilin University, Changchun (Japan)

    2007-07-01

    The highly-ordered molecular structures of 3(5)-(9-anthryl)pyrazole (ANP) have been investigated on Ag(111) by low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Through tailoring film preparation, two different superstructures, {alpha} and {beta}, corresponding to two different molecular registration states have been obtained on Ag(111). At the low substrate temperature (229 K), the structure can be prepared, in which the ANP molecule is adsorbed the surface with the anthryl-group plane tilting in respect to the substrate surface. After annealing the sample to room temperature, it is found that the structure {alpha} gradually evolves into the structure {beta} with four molecules bound together through the hydrogen bonds among them and the anthryl-group plane parallel to the substrate surface to compromise to forming hydrogen bonds. Our analysis reveals a fact that the adsorbate-substrate interaction dominated in the structure {alpha} can change into the hydrogen-bonds prevailed over the structure {beta} as mediating the growth temperature, which is responsible for the variation in the molecular registration states from the anthryl group plane tilting with the substrate surface to parallel to surface.

  5. Absence of a Dirac cone in silicene on Ag(111): First-principles density functional calculations with a modified effective band structure technique

    Science.gov (United States)

    Wang, Yun-Peng; Cheng, Hai-Ping

    2013-06-01

    We investigate the currently debated issue of the existence of the Dirac cone in silicene on an Ag(111) surface, using first-principles calculations based on density functional theory to obtain the band structure. By unfolding the band structure in the Brillouin zone of a supercell to that of a primitive cell, followed by projecting onto Ag and silicene subsystems, we demonstrate that the Dirac cone in silicene on Ag(111) is destroyed. Our results clearly indicate that the linear dispersions observed in both angular-resolved photoemission spectroscopy [P. Vogt , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.108.155501 108, 155501 (2012)] and scanning tunneling spectroscopy [L. Chen , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.109.056804 109, 056804 (2012)] come from the Ag substrate and not from silicene.

  6. Surface-state enhancement of tunneling thermopower on the Ag(111) surface.

    Science.gov (United States)

    Maksymovych, Petro; Kelly, Simon J; Cerdá, Jorge I

    2014-12-23

    Thermoelectric effects in tunnel junctions are currently being revisited for their prospects in cooling and energy harvesting applications, and as sensitive probes of electron transport. Quantitative interpretation of these effects calls for advances in both theory and experiment, particularly with respect to the electron transmission probability across a tunnel barrier which encodes the energy dependence and the magnitude of tunneling thermopower. Using noble metal surfaces as clean model systems, we demonstrate a comparatively simple and quantitative approach where the transmission probability is directly measured experimentally. Importantly, we estimate not only thermovoltage, but also its energy and temperature dependencies. We have thus resolved surface-state enhancement of thermovoltage, which manifests as 10-fold enhancement of thermopower on terraces of the Ag(111) surface compared to single-atom step sites and surface-supported nanoparticles. To corroborate experimental analysis, the methodology was applied to the transmission probability obtained from first-principles calculations for the (111) surfaces of the three noble metals, finding good agreement between overall trends. Surface-state effects themselves point to a possibility of achieving competitive performance of all-metal tunnel junctions when compared to molecular junctions. At the same time, the approach presented here opens up possibilities to investigate the properties of nominally doped or gated thermoelectric tunnel junctions as well as temperature gradient in nanometer gaps.

  7. Adsorption geometry and interface states: Relaxed and compressed phases of NTCDA/Ag(111)

    Science.gov (United States)

    Jakob, P.; Zaitsev, N. L.; Namgalies, A.; Tonner, R.; Nechaev, I. A.; Tautz, F. S.; Höfer, U.; Sánchez-Portal, D.

    2016-09-01

    The theoretical modeling of metal-organic interfaces represents a formidable challenge, especially considering the delicate balance of various interaction mechanisms and the large size of the involved molecular species. In the present study, the energies of interface states, which are known to display a high sensitivity to the adsorption geometry and electronic structure of the deposited molecular species, have been used to test the suitability and reliability of current theoretical approaches. Two well-ordered overlayer structures (relaxed and compressed monolayers) of 1,4,5,8-naphthalene-tetracarboxylic acid dianhydride (NTCDA) on Ag(111) have been investigated using two-photon photoemission to derive precise interface-state energies for these closely related systems. The experimental values are reproduced by our density-functional theory (DFT) calculations with two approaches to treat dispersion interactions (semi-empirical correction DFT-D3 and parametrized functional optB88) and basis set approaches (localized numerical atomic orbitals, plane waves) with remarkable accuracy. Our results underline the trustworthiness and some of the limitations of current DFT-based methods regarding the description of geometric and electronic properties of metal-organic interfaces.

  8. Silver sulphide growth on Ag(111): A medium energy ion scattering study

    Science.gov (United States)

    Window, A. J.; Hentz, A.; Sheppard, D. C.; Parkinson, G. S.; Woodruff, D. P.; Noakes, T. C. Q.; Bailey, P.

    2010-08-01

    The interaction of S 2 with Ag(111) under ultra-high vacuum conditions has been investigated by medium energy ion scattering (MEIS). 100 keV He + MEIS measurements provide a direct confirmation of a previous report, based on thermal desorption, that the growth of multilayer films of Ag 2S occurs through a continuous corrosion process. These films show a commensurate (√7 × √7)R19° unit mesh in low energy electron diffraction, consistent with the epitaxial growth of (111) layers of the high-temperature F-cubic phase of Ag 2S. The substantial range of co-existing film thicknesses found indicates that the growth must be in the form of variable-thickness islands. The use of 100 keV H + incident ions leads to a very rapid decrease in the sulphide film thickness with increasing exposure that we attribute to an unusual chemical leaching, with implanted H atoms interacting with S atoms and desorption of H 2S from the surface.

  9. Processes of adsorption/desorption of iodides and cadmium cations onto/from Ag(111

    Directory of Open Access Journals (Sweden)

    VLADIMIR D. JOVIĆ

    2011-02-01

    Full Text Available In this work, the adsorption/desorption processes of iodides and cadmium cations in the presence of iodides onto/from Ag(111 were investigated. It was shown that both processes were complex, characterized by several peaks on the cyclic voltammograms (CVs. By PeakFit analysis of the recorded CVs and subsequent fitting of the obtained peaks by the Frumkin adsorption isotherm, the interaction parameter (f and the Gibbs energy of adsorption (DGads for each adsorbed phase were determined. In the case of iodide adsorption, four peaks were characterized by negative values of f, indicating attractive lateral interaction between the adsorbed anions, while two of them possessed value of f < –4, indicating phase transition processes. The adsorption/desorption processes of cadmium cations (underpotential deposition – UPD of cadmium in the presence of iodide anions was characterized by two main peaks, each of them being composed of two or three peaks with negative values of f. By the analysis of charge vs. potential dependences obtained either from the CVs or current transients on potentiostatic pulses, it was concluded that adsorbed iodides did not undergo desorption during the process of Cd UPD, but became replaced by Cd ad-atoms and remained adsorbed on top of a Cd layer and/or in between Cd the ad-atoms.

  10. Growth and ordering of Ni(II) diphenylporphyrin monolayers on Ag(111) and Ag/Si(111) studied by STM and LEED.

    Science.gov (United States)

    Murphy, B E; Krasnikov, S A; Cafolla, A A; Sergeeva, N N; Vinogradov, N A; Beggan, J P; Lübben, O; Senge, M O; Shvets, I V

    2012-02-01

    The room temperature self-assembly and ordering of (5,15-diphenylporphyrinato)nickel(II) (NiDPP) on the Ag(111) and Ag/Si(111)-(√3 × √3)R30° surfaces have been investigated using scanning tunnelling microscopy and low-energy electron diffraction. The self-assembled structures and lattice parameters of the NiDPP monolayer are shown to be extremely dependent on the reactivity of the substrate, and probable molecular binding sites are proposed. The NiDPP overlayer on Ag(111) grows from the substrate step edges, which results in a single-domain structure. This close-packed structure has an oblique unit cell and consists of molecular rows. The molecules in adjacent rows are rotated by approximately 17° with respect to each other. In turn, the NiDPP molecules form three equivalent domains on the Ag/Si(111)-(√3 × √3)R30° surface, which follow the three-fold symmetry of the substrate. The molecules adopt one of three equivalent orientations on the surface, acting as nucleation sites for these domains, due to the stronger molecule-substrate interaction compared to the case of the Ag(111). The results are explained in terms of the substrate reactivity and the lattice mismatch between the substrate and the molecular overlayer.

  11. Dipole Formation at Interfaces of Alkanethiolate Self-assembled Monolayers and Ag(111)

    NARCIS (Netherlands)

    Rusu, Paul C.; Giovannetti, Gianluca; Brocks, Geert

    2007-01-01

    The formation of interface dipoles in self-assembled monolayers (SAMs) of −CH3 and −CF3 terminated short-chain alkanethiolates on Ag(111) is studied by means of density functional theory calculations. The interface dipoles are characterized by monitoring the change in the surface work function upon

  12. Diffusion of Six-Atom Cu Islands on Cu(111) and Ag(111)

    Institute of Scientific and Technical Information of China (English)

    Sardar Sikandar Hayat; I.Ahmad; M.Arshad Choudhry

    2011-01-01

    Diffusion of Cu hexamer islands on Cu(111) and Ag(111) is studied using a molecular dynamics simulation technique with many-body potentials obtained from the embedded atom method. Simulations are carried out at temperatures 300, 500 and 700 K, showing that shape-changing multiple-atom processes are more helpful for the diffusion rather than concerted motion of islands. Arrhenius plots of the diffusion coefficients provide effective energy barrier values of 161.29 ± 5 meV for Cu(111) and 179.34 ± 5 meV for Ag(111) surfaces. At 700K, one pop-up atom among island atoms is observed with correlative changes in the position and shape of the lower-layer adatoms.%@@ Diffusion of Cu hexamer islands on Cu(111) and Ag(111) is studied using a molecular dynamics simulation technique with many-body potentials obtained from the embedded atom method.Simulations are carried out at temperatures 300,500 and 700 K,showing that shape-changing multiple-atom processes are more helpful for the diffusion rather than concerted motion of islands.Arrhenius plots of the diffusion coefficients provide effective energy barrier values of 161.29 ± 5 meV for Cu(111) and 179.34 ± 5 meV for Ag(111) surfaces.At 700K,one pop-up atom among island atoms is observed with correlative changes in the position and shape of the lower-layer adatoms.

  13. A theoretical study of a ZnO graphene analogue: adsorption on Ag(111) and hydrogen transport

    Energy Technology Data Exchange (ETDEWEB)

    Demiroglu, Ilker; Illas, Francesc; Bromley, Stefan T [Department de Quimica Fisica and Institut de Quimica Teorica i Computacional (IQTCUB), Universitat de Barcelona (UB), C/MartI i Franques 1, E-08028 Barcelona (Spain); Stradi, Daniele, E-mail: s.bromley@ub.edu [Departamento de Quimica, Universidad Autonoma de Madrid, Ciudad Universitaria de Cantoblanco, E-28049 Madrid (Spain)

    2011-08-24

    A single sheet of zinc oxide (ZnO) based on the same flat two-dimensional (2D) hexagonal topology as graphene, but with alternating neighbouring Zn and O atoms in place of carbon atoms, is studied theoretically. Following experimental studies, the adsorption of 2D-ZnO with the Ag(111) surface is investigated using density functional theory, with and without a semi-empirical correction for dispersive interactions, and with classical interatomic potentials. The interaction of H atoms with the hexagonal Zn{sub 3}O{sub 3} rings of 2D-ZnO is given special attention where multi-centre bond formation is observed to significantly assist the transport of H atoms through the 2D-ZnO sheet.

  14. A theoretical study of a ZnO graphene analogue: adsorption on Ag(111) and hydrogen transport.

    Science.gov (United States)

    Demiroglu, Ilker; Stradi, Daniele; Illas, Francesc; Bromley, Stefan T

    2011-08-24

    A single sheet of zinc oxide (ZnO) based on the same flat two-dimensional (2D) hexagonal topology as graphene, but with alternating neighbouring Zn and O atoms in place of carbon atoms, is studied theoretically. Following experimental studies, the adsorption of 2D-ZnO with the Ag(111) surface is investigated using density functional theory, with and without a semi-empirical correction for dispersive interactions, and with classical interatomic potentials. The interaction of H atoms with the hexagonal Zn(3)O(3) rings of 2D-ZnO is given special attention where multi-centre bond formation is observed to significantly assist the transport of H atoms through the 2D-ZnO sheet.

  15. L-tyrosine on Ag(111): universality of the amino acid 2D zwitterionic bonding scheme?

    Energy Technology Data Exchange (ETDEWEB)

    Reichert, Joachim; Barth, Johannes V. [Physik Department E20, TU Muenchen (Germany); Department of Physics and Astronomy, University of British Columbia, Vancouver (Canada); Schiffrin, Agustin [Max-Planck-Institut fuer Quantenoptik, Garching (Germany); Auwaerter, Willi; Marschall, Matthias [Physik Department E20, TU Muenchen (Germany); Weber-Bargioni, Alexander [Department of Physics and Astronomy, University of British Columbia, Vancouver (Canada); Dell' Angela, Martina; Cvetko, Dean; Bavdek, Gregor; Cossaro, Albano; Morgante, Alberto [C.N.R.-INFM, Laboratorio Nazionale TASK, Trieste (Italy)

    2010-07-01

    We present a combined study of the adsorption and ordering of the L-tyrosine amino acid on close-packed noble-metal surfaces in ultra-high vacuum by means of low-temperature STM, XPS and NEXAFS spectroscopy. Our high resolution topographical STM data reveal noncovalent molecular dimerization within the highly ordered one-dimensional nanostructures, which recalls the geometrical pattern already seen in the L-methionine/Ag(111) system and supports a universal bonding scheme for amino acids on the Ag(111) surface. XPS measurements reveal a zwitterionic adsorption, whereas NEXAFS experiments show a tilted adsorption configuration of the phenol moiety. This enables the interdigitation between aromatic side-chains of adjacent molecules via parallel-displaced {pi}-{pi} interactions which, along with the hydrogen-bonding capability of the hydroxyl functionality, could provide an explanation for the emergence of the self-assembled supramolecular nanoribbons.

  16. Two-photon Photo-emission of Ultrathin Film PTCDA Morphologies on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Aram; Yang, Aram; Shipman, Steven T.; Garrett-Roe, Sean; Johns, James; Strader, Matt; Szymanski, Paul; Muller, Eric; Harris, Charles B.

    2007-11-29

    Morphology- and layer-dependent electronic structure and dynamics at the PTCDA/Ag(111) interface have been studied with angle-resolved two-photon photoemission. In Stranski-Krastanov growth modes, the exposed wetting layer inhibited the evolution of the vacuum level and valence band to bulk values. For layer-by-layer growth, we observed the transition of electron structure from monolayer to bulk values within eight monolayers. Effective masses and lifetimes of the conduction band and the n=1 image potential state were measured to be larger for disordered layers. The effective mass was interpreted in the context of charge mobility measurements.

  17. Interference of spin states in photoemission from Sb/Ag(111) surface alloys

    Energy Technology Data Exchange (ETDEWEB)

    Meier, Fabian; Osterwalder, Juerg; Hugo Dil, J [Physik-Institut, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Petrov, Vladimir [St Petersburg Polytechnical University, 29 Polytechnicheskaya Street, 195251 St Petersburg (Russian Federation); Mirhosseini, Hossein; Henk, Juergen [Max-Planck-Institut fuer Mikrostrukturphysik, D-06120 Halle (Saale) (Germany); Patthey, Luc, E-mail: jan-hugo.dil@psi.ch [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen (Switzerland)

    2011-02-23

    Using a three-dimensional spin polarimeter we have gathered evidence for the interference of spin states in photoemission from the surface alloy Sb/Ag(111). This system features a small Rashba-type spin splitting of a size comparable to the momentum broadening of the quasiparticles, thus causing an intrinsic overlap between states with orthogonal spinors. Besides a small spin polarization caused by the spin splitting, we observe a large spin polarization component in the plane normal to the quantization axis of the Rashba effect. Strongly suggestive of coherent spin rotation, this effect is largely independent of the photon energy and photon polarization. (fast track communication)

  18. Unconventional Fermi surface spin patterns in the (Bi/Pb/Sb)/Ag(111) surface alloy

    Energy Technology Data Exchange (ETDEWEB)

    Meier, Fabian; Dil, Hugo [Physik Institut Universitaet Zuerich (Switzerland); Swiss Light Source PSI (Switzerland); Petrov, Vladimir [Physics Institute St Petersburg (Russian Federation); Patthey, Luc [Swiss Light Source PSI (Switzerland); Osterwalder, Juerg [Physik Institut Universitaet Zuerich (Switzerland)

    2009-07-01

    By a controllable change in the stoichiometry of the long range ordered mixed surface alloy (Bi/Pb/Sb)/Ag(111) the Rashba and Fermi energy can be tuned over a wide range. We show by spin and angle-resolved photoemission spectroscopy that the spin structure of the individual surface state bands remain unaffected despite the random intermixing of the adatoms. We further report on the observation of unconventional Fermi surface spin textures. These spin textures are found when the Fermi energy lies between the crossing point and the apex of the Rashba type Kramer's pair. The results will be discussed in the context of spin transport.

  19. The fate of the 2√3 × 2√3R(30° silicene phase on Ag(111

    Directory of Open Access Journals (Sweden)

    Zhi-Long Liu

    2014-09-01

    Full Text Available Silicon atoms deposited on Ag(111 produce various single layer silicene sheets with different buckling patterns and periodicities. Low temperature scanning tunneling microscopy reveals that one of the silicene sheets, the hypothetical √7 × √7 silicene structure, on 2√3 × 2√3 Ag(111, is inherently highly defective and displays no long-range order. Moreover, Auger and photoelectron spectroscopy measurements reveal its sudden death, to end, in a dynamic fating process at ∼300 °C. This result clarifies the real nature of the 2√3 × 2√3R(30° silicene phase and thus helps to understand the diversity of the silicene sheets grown on Ag(111.

  20. The adsorption geometry of PTCDA on Ag(111). An NIXSW study

    Energy Technology Data Exchange (ETDEWEB)

    Hauschild, Annegret

    2007-12-14

    The bonding lengths of a large pi-conjugated molecule which was adsorbed on a metal surface were determined for the first molecular layer. The system consisting of the organic molecules 3,4,9,10-Perylenetetracarboxylic dianhydride (PTCDA) grown on a silver(111) surface was investigated. PTCDA on Ag(111) appears in two phases in the first layer: The commensurate long range ordered monolayer at room temperature (RT phase) is a stable phase, whereas the disordered phase which is grown at temperatures below 160 K (LT phase) is a metastable phase. The bonding distance of the molecules from the surface is an indication for the bonding strength. Distortions of the molecules from the planar geometry give additional information on the bonding mechanism. Using NIXSW, the vertical distance of the molecules was investigated by the core-level C1s transition. Since carbon is the main element of the molecules, its vertical distance corresponds to the averaged molecular distance. Furthermore, the distances of the oxygen atoms of the molecules were determined by using the O1s transition. In the molecule, two types of chemically different oxygen atoms exist: the four outer carboxylic oxygen atoms and the two inner anhydride oxygen atoms. For the first time, this chemical shift of one atom sort within a molecule was utilized for a separation of the photoemission spectra which were taken in a standing wave experiment. Within this work, different vertical positions for atoms of the same element could be identified. For the RT phase an average molecular bonding distance of 2.86 A was measured. For the LT phase the corresponding value is 2.80 A. Thus, the molecules in the LT phase are 0.06 A closer to the Ag surface than the molecules in the RT phase, this result clearly is significant. In the LT phase, a stronger intramolecular distortion was observed, the oxygen atoms lie 0.14 A below the carbon core, whereas the molecules in the RT phase do not exhibit such a strong distortion, the

  1. Adsorption and Decomposition of EtO on Cl-modified Ag(111)at Low Temperatures

    Institute of Scientific and Technical Information of China (English)

    吴凯; 王德峥; 魏绪明; 曹玉明; 郭燮贤

    1994-01-01

    The adsorption and decomposition of ethylene oxide(EtO)on Cl-modified and oxygen-pre-covered Ag(111)at low temperatures with high resolution electron energy loss spectroscopy(HREELS)arestudied.At 140 K,EtO is molecularly adsorbed on the surface.At above 230K.with atomic oxygen on thesurface,a small amount of EtO decomposes into ethylene and is oxidized to produce some oxidation productsas water,etc.while with dioxygen on the surface,a large amount of EtO decomposes into ethylene and isoxidized to produce large amounts of oxidation products like water and so on.The experimental resultsshowed that chlorine can,on the one hand,decrease the adsorption amount of EtO and,on the other hand,inhibit the further oxidation of EtO.

  2. Role of thermal processes in dewetting of epitaxial Ag(111) film on Si(111)

    Science.gov (United States)

    Sanders, Charlotte E.; Zhang, Chendong; Kellogg, Gary L.; Shih, Chih-Kang

    2014-12-01

    Epitaxially grown silver (Ag) film on silicon (Si) is an optimal plasmonic device platform, but its technological utility has been limited by its tendency to dewet rapidly under ambient conditions (standard temperature and pressure). The mechanisms driving this dewetting have not heretofore been determined. In this study, scanning probe microscopy and low-energy electron microscopy are used to compare the morphological evolution of epitaxial Ag(111)/Si(111) under ambient conditions with that of similarly prepared films heated under ultra-high vacuum (UHV) conditions. Dewetting in both cases is seen to be initiated with the formation of pinholes, which might function to relieve strain in the film. We find that in the UHV environment, dewetting is determined by thermal processes, while under ambient conditions, thermal processes are not required. We conclude that dewetting in ambient conditions is triggered by some chemical process, most likely oxidation.

  3. Structures of Adatom Clusters on Ag(111) Surface by Genetic Algorithm

    Institute of Scientific and Technical Information of China (English)

    SUN Zhi-Hua; LIU Qing-Wei; LI Yu-Fen; ZHUANG Jun

    2004-01-01

    @@ We study the structures of Ag adatom clusters supported on the metal Ag(111) surface using the genetic algorithm (GA). The atomic interactions are modelled by the surface-embedded-atom method. The lowest-energy structures of adatom clusters with sizes n = 3-20 are obtained, in which n = 7, 10, 12, 14, 16, 19 are the magic numbers.Furthermore, we give a series of structures with energies close to the lowest energy (the lower-energy isomers), and the structure features are studied in detail. Except for some magic clusters and small clusters, every configuration of adatom clusters generally has two distinct adsorption ways, so the isomers always appear in pairs.

  4. Two-photon Photoemission of Organic Semiconductor Molecules on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Aram [Univ. of California, Berkeley, CA (United States)

    2008-05-01

    Angle- and time-resolved two-photon photoemission (2PPE) was used to study systems of organic semiconductors on Ag(111). The 2PPE studies focused on electronic behavior specific to interfaces and ultrathin films. Electron time dynamics and band dispersions were characterized for ultrathin films of a prototypical n-type planar aromatic hydrocarbon, PTCDA, and representatives from a family of p-type oligothiophenes.In PTCDA, electronic behavior was correlated with film morphology and growth modes. Within a fewmonolayers of the interface, image potential states and a LUMO+1 state were detected. The degree to which the LUMO+1 state exhibited a band mass less than a free electron mass depended on the crystallinity of the layer. Similarly, image potential states were measured to have free electron-like effective masses on ordered surfaces, and the effective masses increased with disorder within the thin film. Electron lifetimes were correlated with film growth modes, such that the lifetimes of electrons excited into systems created by layer-by-layer, amorphous film growth increased by orders of magnitude by only a few monolayers from the surface. Conversely, the decay dynamics of electrons in Stranski-Krastanov systems were limited by interaction with the exposed wetting layer, which limited the barrier to decay back into the metal.Oligothiophenes including monothiophene, quaterthiophene, and sexithiophene were deposited on Ag(111), and their electronic energy levels and effective masses were studied as a function of oligothiophene length. The energy gap between HOMO and LUMO decreased with increasing chain length, but effective mass was found to depend on domains from high- or low-temperature growth conditions rather than chain length. In addition, the geometry of the molecule on the surface, e.g., tilted or planar, substantially affected the electronic structure.

  5. Experimental and theoretical study of the adsorption of fumaramide [2]rotaxane on Au(111) and Ag(111) surfaces

    NARCIS (Netherlands)

    Mendoza, S.M.; Whelan, C.M.; Jalkanen, J.-P.; Zerbetto, F.; Gatti, F.; Kay, E.R.; Leigh, D.A.; Lubomska, Monika; Rudolf, Petra

    2005-01-01

    Thin films of fumaramide [2] rotaxane, a mechanically interlocked molecule composed of a macrocycle and a thread in a "bead and thread" configuration, were prepared by vapor deposition on both Ag(111) and Au(111) substrates. X-ray photoelectron spectroscopy (XPS) and high-resolution electron-energy-

  6. Two-photon photoemission study of the coverage-dependent electronic structure of chemisorbed alkali atoms on a Ag(111) surface.

    Science.gov (United States)

    Wang, Lei-Ming; Sametoglu, Vahit; Winkelmann, Aimo; Zhao, Jin; Petek, Hrvoje

    2011-09-01

    We report a systematic investigation of the electronic structure of chemisorbed alkali atoms (Li-Cs) on a Ag(111) surface by two-photon photoemission spectroscopy. Angle-resolved two-photon photoemission spectra are obtained for 0-0.1 monolayer coverage of alkali atoms. The interfacial electronic structure as a function of periodic properties and the coverage of alkali atoms is observed and interpreted assuming ionic adsorbate/substrate interaction. The energy of the alkali atom σ-resonance at the limit of zero coverage is primarily determined by the image charge interaction, whereas at finite alkali atom coverages, it follows the formation of a dipolar surface field. The coverage- and angle-dependent two-photon photoemission spectra provide information on the photoinduced charge-transfer excitation of adsorbates on metal surfaces. This work complements the previous work on alkali/Cu(111) chemisorption [Phys. Rev. B 2008, 78, 085419].

  7. Submonolayer and multilayer growth of titaniumoxide-phthalocyanine on Ag(111)

    Science.gov (United States)

    Kröger, Ingo; Stadtmüller, Benjamin; Kumpf, Christian

    2016-11-01

    For exploiting the full potential of organic materials for future organic electronic devices it is of crucial importance to understand structural and electronic properties of metal-organic interfaces and adsorbate systems, in particular electronic interactions and growth mechanisms. Phthalocyanine molecules represent one class of materials which are very frequently discussed in this context. They feature an appealing tunability in terms of structural, electronic and magnetic properties, simply by exchanging the central (metal) atom or group of atoms. Here we present a comprehensive study of one of the model systems in this field, TiOPc on Ag(111). We discuss structure formation and growth from submonolayer to multilayer films, based on results obtained by electron diffraction, scanning tunneling microscopy, electron energy loss spectroscopy, x-ray standing waves, photoelectron spectroscopy and pair potential calculations. Similar to related metal-phthalocyanine adsorbate systems we find three distinct phases in the submonolayer regime, a disordered gas-like ‘g-phase’, a commensurate ‘c2-phase’ at low temperature, and a ‘p.o.l.-phase’ consisting of a series of point-on-line structures with continuously shrinking unit cells. For the latter a uniform TiO-up configuration (Ti-O group pointing towards vacuum) was found. Hence, the first-layer molecules form a strong dipole layer, the dipole moment of which is compensated by molecules adsorbing in the second layer at hollow-sites in TiO-down geometry (Ti-O group pointing towards the surface). The Coulomb interaction between the dipole moments in the first and second layer stabilizes this bilayer structure and causes a bilayer-by-bilayer growth mode of molecular films above a thickness of 2 ML. We report the structural properties (vertical adsorption heights, inter-layer distances, inplane orientations and positions) of the molecules in all phases in detail, and discuss the effect of inelastic dynamical charge

  8. Electronic structure of LaAg{sub 5} alloy films on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Seibel, Christoph; Bentmann, Hendrik; Forster, Frank [Universitaet Wuerzburg, Experimentelle Physik VII, Am Hubland, D-97074 Wuerzburg (Germany); Moreschini, Luca [Ecole Polytechnique Federale de Lausanne (EPFL), Institut de Physique des Nanostructures, CH-1015 Lausanne (Switzerland); Bihlmayer, Gustav [Institut fuer Festkoerperforschung, Forschungszentrum Juelich, D-52425 Juelich (Germany); Reinert, Friedrich [Universitaet Wuerzburg, Experimentelle Physik VII, Am Hubland, D-97074 Wuerzburg (Germany); Forschungszentrum Karlsruhe, Gemeinschaftslabor fuer Nanoanalytik, D-76021 Karlsruhe (Germany)

    2010-07-01

    We have characterized the growth of La on Ag(111) by UPS, XPS and LEED. At La coverages of about 4 ML or higher and subsequent annealing we observe an ordered (2x2) surface structure that is rotated by 30 with respect to the substrate. In analogy to the well-studied system CePt{sub 5}, we identify our system as a LaAg{sub 5} alloy in a CaCu{sub 5}-type structure. Employing angle-resolved photoelectron spectroscopy (ARPES) we measured the band structure along high symmetry lines and the Fermi surface (FS) of the LaAg{sub 5} films. We find several sharp bands near the Fermi level and a high anisotropy in the FS. Our results are compared to ARPES results on CePt{sub 5} and LaPt{sub 5} as well as first-principles calculations. The system shall serve as a reference for iso-structural alloys composed of other lanthanoids, such as Ce or Gd, potentially showing Kondo physics or other magnetic effects.

  9. UV photo-dissociation and photodesorption of N{sub 2}O on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ki Hyun; Watanabe, Kazuo; Menzel, Dietrich; Freund, Hans-Joachim, E-mail: watanabe@fhi-berlin.mpg.d [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin (Germany)

    2010-03-03

    Nanosecond laser induced photoreactions of N{sub 2}O adsorbed on Ag(111) have been studied by temperature programmed desorption (TPD) and mass-selected, angle-dependent time-of-flight (MS-TOF) measurements of neutral desorbing particles. N{sub 2}O molecules in the first monolayer are thermally inert but photo-dissociate into N{sub 2} + O, or photodesorb molecularly or dissociatively, at photon energies above 3.5 eV. We have found that TOF spectra of photodesorbed N{sub 2} as well as of N{sub 2}O measured at hnu = 4.7 eV consist of two velocity components. The desorption flux of the fastest component of N{sub 2}O peaks approx 25 deg. off the surface normal, whereas the others are directed in the surface normal. Origins and photo-excitation as well as photodesorption mechanisms of the N{sub 2}O and N{sub 2} signals are discussed.

  10. Dehydrocyclization of peripheral alkyl groups in porphyrins at Cu(100) and Ag(111) surfaces

    Science.gov (United States)

    Williams, Christopher G.; Wang, Miao; Skomski, Daniel; Tempas, Christopher D.; Kesmodel, Larry L.; Tait, Steven L.

    2016-11-01

    The self-assembly of organic and metal-organic species at metal surfaces is a topic of high interest for applications that can benefit from tunable surface functionalization through organic building block design. As the complexity of molecular building blocks increases to direct ordering and function, thermal stability of the adsorbate often increases opening up new surface-catalyzed reaction pathways. We report dehydrocyclization of octaethylporphyrin to tetrabenzoporphyrin on the Cu(100) and Ag(111) surfaces at 500-600 K. Dehydrocyclization of smaller species is not typically observed on these surfaces at low pressure due to short adsorption lifetimes. The dehydrocyclization of peripheral ethyl groups forms benzo groups which then undergo additional dehydrogenation. The reaction products are characterized by high resolution electron energy loss spectroscopy (HREELS), scanning tunneling microscopy (STM), and X-ray photoelectron spectroscopy (XPS). These results extend our understanding of reaction pathways that may be encountered as molecular building blocks increase in size and complexity on relatively inert surfaces.

  11. Evidence for graphite-like hexagonal AlN nanosheets epitaxially grown on single crystal Ag(111)

    Science.gov (United States)

    Tsipas, P.; Kassavetis, S.; Tsoutsou, D.; Xenogiannopoulou, E.; Golias, E.; Giamini, S. A.; Grazianetti, C.; Chiappe, D.; Molle, A.; Fanciulli, M.; Dimoulas, A.

    2013-12-01

    Ultrathin (sub-monolayer to 12 monolayers) AlN nanosheets are grown epitaxially by plasma assisted molecular beam epitaxy on Ag(111) single crystals. Electron diffraction and scanning tunneling microscopy provide evidence that AlN on Ag adopts a graphite-like hexagonal structure with a larger lattice constant compared to bulk-like wurtzite AlN. This claim is further supported by ultraviolet photoelectron spectroscopy indicating a reduced energy bandgap as expected for hexagonal AlN.

  12. Adsorption of chlorine on Ag(111): No subsurface Cl at low coverage

    Science.gov (United States)

    Gava, Paola; Kokalj, Anton; de Gironcoli, Stefano; Baroni, Stefano

    2008-10-01

    The adsorption of molecular and atomic chlorine on perfect Ag(111) surface has been studied and characterized by means of extensive density-functional-theory calculations. For the molecular adsorption, we find that the dissociation of Cl2 proceeds with an almost vanishing barrier. As for the adsorption of atomic Cl, on-surface, subsurface, and substitutional adsorptions are considered as a function of the coverage. At coverage lower than 1/2 ML, the on-surface adsorption displays the most exothermic chemisorption energies, whereas the mixed on-surface+subsurface and on-surface+substitutional adsorption modes become competitive with pure on-surface adsorption at about 1/2 ML of coverage and at higher coverages even preferred. The analysis of the adsorption free energy as a function of chlorine chemical potential reveals that the on-surface (3×3)R30° adsorption phase is thermodynamically the most stable over a very broad range of Cl chemical potential. The mixed adsorption modes become thermodynamically more stable at high coverage for values of the Cl chemical potential that are substantially larger than those needed to form silver chloride. This finding seems to indicate that the formation of mixed adsorption phases, if they would ever occur, cannot be due to thermodynamic equilibrium but can only result from kinetic effects. We also find that the presence of open surface steps does not stabilize the subsurface Cl adsorption at low coverage. However due to the stronger Cl-surface interaction near steps, the mixed on-surface+subsurface adsorption on Ag(210) at high coverage becomes thermodynamically the most stable phase at Cl chemical potential close to that needed for the formation of bulk AgCl.

  13. An economical and convenient experiment setup for electrode investigation.

    Science.gov (United States)

    Aryan, Naser Pour; Rieger, Viola; Brendler, Christian; Rothermel, Albrecht

    2012-01-01

    Electrodes are among the critical components of neural stimulation devices. Investigating electrode properties like electrode impedance, charge injection capacity, and electrode corrosion limits plays an important role in electrode development. There are many commercial devices available for this purpose. Although useful, these devices are usually expensive and often offer more functions than required. We propose a versatile setup, composed of a LabVIEW program, a National Instruments multifunctional board, and a circuit built of discrete commercial elements. The system offers basic functions used in electrochemical investigation like current and voltage injection, cyclic voltammetry, and impedance spectroscopy. It offers the functionalities of both a potentiostat and an arbitrary waveform generator. It has already been applied elsewhere.

  14. Site-specific dissociation dynamics of H{sub 2}/D{sub 2} on Ag(111) and Co(0001) and the validity of the site-averaging model

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Xixi [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Jiang, Bin [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Xie, Daiqian, E-mail: dqxie@nju.edu.cn, E-mail: hguo@unm.edu [Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Guo, Hua, E-mail: dqxie@nju.edu.cn, E-mail: hguo@unm.edu [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2015-09-21

    Dissociative chemisorption of polyatomic molecules on metal surfaces involves high-dimensional dynamics, of which quantum mechanical treatments are computationally challenging. A promising reduced-dimensional approach approximates the full-dimensional dynamics by a weighted average of fixed-site results. To examine the performance of this site-averaging model, we investigate two distinct reactions, namely, hydrogen dissociation on Co(0001) and Ag(111), using accurate first principles potential energy surfaces (PESs). The former has a very low barrier of ∼0.05 eV while the latter is highly activated with a barrier of ∼1.15 eV. These two systems allow the investigation of not only site-specific dynamical behaviors but also the validity of the site-averaging model. It is found that the reactivity is not only controlled by the barrier height but also by the topography of the PES. Moreover, the agreement between the site-averaged and full-dimensional results is much better on Ag(111), though quantitative in neither system. Further quasi-classical trajectory calculations showed that the deviations can be attributed to dynamical steering effects, which are present in both reactions at all energies.

  15. Unveiling the atomic structure and electronic properties of atomically thin boron sheets on an Ag(111) surface.

    Science.gov (United States)

    Shu, Haibo; Li, Feng; Liang, Pei; Chen, Xiaoshuang

    2016-09-15

    Two-dimensional (2D) boron sheets (i.e., borophene) have a huge potential as a basic building block in nanoelectronics and optoelectronics; such a situation is greatly promoted by recent experiments on fabrication of borophene on silver substrates. However, the fundamental atomic structure of borophene on the Ag substrate is still under debate, which greatly impedes further exploration of its properties. Herein, the atomic structure and electronic properties of borophene on an Ag(111) surface have been studied using first-principles calculations and ab initio molecular dynamics simulations. Our results reveal that there exist three energetically favorable borophene structures (β5, χ1, and χ2) on the Ag(111) surface and their simulated STM images are in good agreement with experimental results, suggesting the coexistence of boron phases during the growth. All these stable borophene structures have a planar structure with slight surface buckling (∼0.15 Å) and relatively high hexagonal vacancy density (1/6 and 1/5) and exhibit typical metallic conductivity. These findings not only can be applied to solve the experimental controversies about the atomic structure of borophene on the Ag substrate but also provide a theoretical basis for exploring the fundamental properties and applications of 2D boron sheets.

  16. Manipulation of the surface density of states of Ag(111) by means of resonators: Experiment and theory

    Science.gov (United States)

    Fernández, J.; Moro-Lagares, María; Serrate, D.; Aligia, A. A.

    2016-08-01

    We show that the density of surface Shockley states of Ag(111) probed by the differential conductance G (V )=d I /d V by a scanning-tunneling microscope (STM) can be enhanced significantly at certain energies and positions introducing simple arrays of Co or Ag atoms on the surface, in contrast to other noble-metal surfaces. Specifically we have studied resonators consisting of two parallel walls of five atoms deposited on the clean Ag(111) surface. A simple model in which the effect of the adatoms is taken into account by an attractive local potential and a small hybridization between surface and bulk at the position of the adatoms explains the main features of the observed G (V ) and allows us to extract the proportion of surface and bulk states sensed by the STM tip. These results might be relevant to engineer the surface spectral density of states, to study the effects of surface states on the Kondo effect, and to separate bulk and surface contributions in STM studies of topological surface states.

  17. XPS of oxygen atoms on Ag(111) and Ag(110) surfaces: accurate study with SAC/SAC-CI combined with dipped adcluster model.

    Science.gov (United States)

    Ishikawa, Atsushi; Nakatsuji, Hiroshi

    2013-08-01

    O1s core-electron binding energies (CEBE) of the atomic oxygens on different Ag surfaces were investigated by the symmetry adapted cluster-configuration interaction (SAC-CI) method combined with the dipped adcluster model, in which the electron exchange between bulk metal and adsorbate is taken into account properly. Electrophilic and nucleophilic oxygens (O(elec) and O(nuc)) that might be important for olefin epoxidation in a low-oxygen coverage condition were focused here. We consider the O1s CEBE as a key property to distinguish the surface oxygen states, and series of calculation was carried out by the Hartree-Fock, Density functional theory, and SAC/SAC-CI methods. The experimental information and our SAC/SAC-CI results indicate that O(elec) is the atomic oxygen adsorbed on the fcc site of Ag(111) and that O(nuc) is the one on the reconstructed added-row site of Ag(110) and that one- and two-electron transfers occur, respectively, to the O(elec) and O(nuc) adclusters from the silver surface.

  18. Quasi-1D States Confined in a Self-Assembled Organic Super-Lattice of TTF-TCNQ on Ag(111)

    Science.gov (United States)

    Jeon, Seokmin; Ganesh, Panchapakesan; Sumpter, Bobby; Cerdá, Jorge Iribas; Maksymovych, Petro; CNMS Team; ICMM-CSIC Team

    2015-03-01

    Organic charge transfer complexes (CTC) have drawn much attention due to their potential applications to conducting or semiconducting organic thin films and contacts in devices. TTF-TCNQ is a historic organic CTC with one of the highest conductivity values among numerous organic conductors. As a two-component molecular material, TTF-TCNQ in a low-dimension form on a surface naturally creates monolayer super-lattices with corrugated electrostatic potential and adsorbate-induced strain. Generally this will lead to strong confinement of the surface states, although the detailed response of the surface electronic structure remains to be understood. We investigated TTF-TCNQ monolayer films grown on Ag(111), Au(111) and Ag(100) surfaces using STM/STS at 4.3 K. Confinement of sp-derived surface states was indeed ubiquitous, including spontaneous formation of quantum dots and quasi-1D bands. The small periodicity of the lattice caused a complete depopulation of the surface states, with up to 1 eV upshift of the band minimum - much stronger effect than normally observed in assemblies. This also allows us to infer the height of the confining potential using 1D Kronig-Penney model and critically assess the long-standing problem of molecule-surface charge transfer. A portion of this research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

  19. Impact of a molecular wetting layer on the structural and optical properties of tin(II)-phthalocyanine multilayers on Ag(111)

    Science.gov (United States)

    Gruenewald, Marco; Peuker, Julia; Meissner, Matthias; Sojka, Falko; Forker, Roman; Fritz, Torsten

    2016-03-01

    We investigate ultrathin highly ordered layers of tin(II)-phthalocyanine (SnPc) on top of a monolayer (ML) of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Ag(111). The films are analyzed structurally by means of scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) as well as optically using differential reflectance spectroscopy (DRS). We find that the first ML of SnPc is entirely rearranged upon bilayer (BL) formation, yielding a commensurate registry in higher-order coincidence with the underlying PTCDA lattice. SnPc layers adsorbed on top self-assemble in further BLs. Within each BL the molecules are arranged pairwise, i.e., stacked as physical dimers, providing a characteristic absorption spectrum with strongly redshifted components compared to SnPc monomers. This altered spectral envelope mainly originates from strong orbital overlap of stacked molecules within each BL. In contrast, adjacent BLs show only weak orbital overlap, which is responsible for an additional redshift of the low-energy transition band. Our results demonstrate that a simple modification of the metal substrate surface, e.g., by a PTCDA wetting layer, has beneficial effects on structural ordering of SnPc multilayers adsorbed on top. The impact on the optical absorption spectrum manifests in a narrow and intense absorption peak in the near-infrared spectral region which is significantly less pronounced if the PTCDA layer is omitted.

  20. The Investigation of EDM Parameters on Electrode Wear Ratio

    Directory of Open Access Journals (Sweden)

    Reza Atefi

    2012-05-01

    Full Text Available Electrical Discharge Machining (EDM is a well-established machining option for manufacturing geometrically complex or hard material parts that are extremely difficult-to-machine by conventional machining processes. The non-contact machining technique has been continuously evolving from a mere tool and die making process. In this study, the influence of different electro discharge machining parameters (current, pulse on-time, pulse off-time, arc voltage on the electrode wear ratio as a result of application copper electrode to hot work steel DIN1.2344 has been investigated. Design of the experiment was chosen as full factorial. Artificial neural network has been used to choose proper machining parameters and to reach certain electrode wear ratio. Finally a hybrid model has been designed to reduce the artificial neural network errors. The experiment results indicated a good performance of proposed method in optimization of such a complex and non-linear problems.

  1. Resonant core spectroscopies of the charge transfer interactions between C60 and the surfaces of Au(111), Ag(111), Cu(111) and Pt(111)

    Science.gov (United States)

    Gibson, Andrew J.; Temperton, Robert H.; Handrup, Karsten; O'Shea, James N.

    2017-03-01

    Charge transfer interactions between C60 and the metal surfaces of Ag(111), Cu(111), Au(111) and Pt(111) have been studied using synchrotron-based photoemission, resonant photoemission and X-ray absorption spectroscopies. By placing the X-ray absorption and valence band spectra on a common binding energy scale, the energetic overlap of the unoccupied molecular orbitals with the density of states of the underlying metal surface have been assessed in the context of possible charge transfer pathways. Resonant photoemission and resonant Auger data, measuring the valence region as a function of photon energy for C60 adsorbed on Au(111) reveals three constant high kinetic energy features associated with Auger-like core-hole decay involving an electron transferred from the surface to the LUMO of the molecule and electrons from the three highest occupied molecular orbitals, respectively and in the presence of ultra-fast charge transfer of the originally photoexcited molecule to the surface. Data for the C60/Ag(111) surface reveals an additional Auger-like feature arising from a core-hole decay process involving more than one electron transferred from the surface into the LUMO. An analysis of the relative abundance of these core-hole decay channels estimates that on average 2.4 ± 0.3 electrons are transferred from the Ag(111) surface into the LUMO. A core-hole clock analysis has also been applied to assess the charge transfer coupling in the other direction, from the molecule to the Au(111) and Ag(111) surfaces. Resonant photoemission and resonant Auger data for C60 molecules adsorbed on the Pt(111) and Cu(111) surfaces are shown to exhibit no super-Auger features, which is attributed to the strong modification of the unoccupied molecular orbitals arising from stronger chemical coupling of the molecule to the surface.

  2. In situ nonlinear optical spectroscopy of electron-phonon couplings at alkali-doped C{sub 60}/Ag(111) interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kakudji, Ernest [Research Centre in Physics of Matter and Radiation (PMR), University of Namur (FUNDP), B-5000 Namur (Belgium); Physics Department, University of Kinshasa (UNIKIN), Kinshasa (CD); Silien, Christophe [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Lis, Dan; Cecchet, Francesca; Thiry, Paul A.; Peremans, Andre; Caudano, Yves [Research Centre in Physics of Matter and Radiation (PMR), University of Namur (FUNDP), B-5000 Namur (Belgium); Nouri, Abdelkader [Laboratoire Materiaux, Ecole Normale Superieure d' Enseignement Technique (ENSET), Oran 31000 (Algeria)

    2010-08-15

    We use doubly resonant, infrared-visible sum-frequency generation spectroscopy (DR-SFG) to probe vibrational and electronic properties of C{sub 60} and K-doped C{sub 60} monolayers adsorbed on Ag(111) single crystal under ultra-high vacuum (UHV). We recorded the interface SFG spectra for five visible wavelengths. We observe a strong dependence of the SFG intensity of the totally symmetric A{sub g}(2) mode of the fullerene while scanning the visible wavelength, due to the DR-SFG phenomenon. The SFG intensity of the A{sub g}(2) mode is the strongest at 488 nm and at 532 nm for the pure and fully doped monolayers, respectively. These results demonstrate the occurrence of electron-phonon couplings at the C{sub 60}/Ag(111) and saturated K/C{sub 60}/Ag(111) interfaces. They enable us to determine the energy of the coupled electronic transition and to link the electronic resonance to the h{sub u} (HOMO) to t{sub 1g} (LUMO + 1) transition of C{sub 60}. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  3. Investigation on a Novel Capacitive Electrode for Geophysical Surveys

    Directory of Open Access Journals (Sweden)

    Zhiyu Wang

    2016-01-01

    Full Text Available Nonpolarizable electrodes are applied widely in the electric field measurement for geophysical surveys. However, there are two major problems: (1 systematic errors caused by poor electrical contact in the high resistive terrains and (2 environmental damage associated with using nonpolarizable electrodes. A new alternative structure of capacitive electrode, which is capable of sensing surface potential through weak capacitive coupling, is presented to solve the above problems. A technique is introduced to neutralize distributed capacitance and input capacitance of the detection circuit. With the capacitance neutralization technique, the transmission coefficient of capacitive electrode remains stable when environmental conditions change. The simulation and field test results indicate that the new capacitive electrode has an operating bandwidth range from 0.1 Hz to 1 kHz. The capacitive electrodes have a good prospect of the applications in geophysical prospecting, especially in resistive terrains.

  4. Interfacial charge rearrangement and intermolecular interactions: Density-functional theory study of free-base porphine adsorbed on Ag(111) and Cu(111)

    CERN Document Server

    Müller, Moritz; Maurer, Reinhard J; Reuter, Karsten

    2015-01-01

    We employ dispersion-corrected density-functional theory to study the adsorption of tetrapyrrole 2H-porphine (2H-P) at Cu(111) and Ag(111). Various contributions to adsorbate-substrate and adsorbate-adsorbate interactions are systematically extracted to analyze the self-assembly behavior of this basic building block to porphyrin-based metal-organic nanostructures. This analysis reveals a surprising importance of substrate-mediated van der Waals interactions between 2H-P molecules, in contrast to negligible direct dispersive interactions. The resulting net repulsive interactions rationalize the experimentally observed tendency for single molecule adsorption.

  5. A study of the O/Ag(111) system with scanning tunneling microscopy and x-ray photoelectron spectroscopy at ambient pressures

    Science.gov (United States)

    Heine, Christian; Eren, Baran; Lechner, Barbara A. J.; Salmeron, Miquel

    2016-10-01

    The interaction of O2 with the Ag(111) surface was studied with scanning tunneling microscopy (STM) in the pressure range from 10- 9 Torr to 1 atm at room temperature and with X-ray photoelectron spectroscopy (XPS) up to 0.3 Torr O2 in the temperature range from RT to 413 K. STM images show that the Ag(111) surface topography is little affected in regions with large flat terraces, except for the appearance of mobile features due to oxygen atoms at pressures above 0.01 Torr. In regions where the step density is high, the surface became rough under 0.01 Torr of O2, due to the local oxidation of Ag. Various chemical states of oxygen due to chemisorbed, oxide and subsurface species were identified by XPS as a function of pressure and temperature. The findings from the STM images and XPS measurements indicate that formation of an oxide phase, the thermodynamically stable form at room temperature under ambient O2 pressure, is kinetically hindered in the flat terrace areas but proceeds readily in regions with high-step density.

  6. Electrochemical investigation of NO at single-wall carbon nanotubes modified electrodes

    Indian Academy of Sciences (India)

    Tingliang Xia; Hongmei Bi; Keying Shi

    2010-05-01

    The NO electro-oxidation was investigated at various single-wall carbon nanotubes (SWCNTs) modified electrodes by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Compared with the glassy carbon electrode, the SWCNTs modified electrodes possess higher electro-catalytic activity to NO electro-oxidation. CV results indicate that the peak current density of NO electro-oxidation at the SWCNT-COOH (SWCNTs with carboxyl groups) modified electrode is the highest and the peak potential is the most negative among the four kinds of electrodes. EIS indicates that the charge transfer resistance of NO electro-oxidation at the SWCNT-COOH modified electrode is the least. The determined factors (charge transfer and mass transfer of diffusion) of NO electro-oxidation are different in varied potential region. The mechanism of NO electro-oxidation reaction at the SWCNTs modified electrodes is also discussed.

  7. Reversible and irreversible dilation of lithium-ion battery electrodes investigated by in-situ dilatometry

    Science.gov (United States)

    Sauerteig, Daniel; Ivanov, Svetlozar; Reinshagen, Holger; Bund, Andreas

    2017-02-01

    The technique of electrochemical in-situ dilatometry is applied to study the intercalation induced macroscopic expansion of electrodes for lithium-ion batteries. A full cell setup is used to investigate the expansion under real conditions. This method enables in-situ measurement of expansion under defined pressure, using conventional electrodes, separators and electrolytes. To understand the influence of the microstructure, the swelling behavior of different LiNi1/3 Mn1/3 Co1/3 O2 (NMC) positive electrodes and graphite negative electrodes is measured and systematically analyzed. A theoretical approach for assessment of reversible electrode displacement in a full cell is developed, by using a low number of material specific input parameters. Electrochemical in-situ dilatometry is able to show differences in irreversible dilation depending on electrode design and therefore it is a powerful technique for stability and lifetime assessment.

  8. Investigation of Top/Bottom electrode and Diffusion Barrier Layer for PZT Thick Film MEMS Sensors

    DEFF Research Database (Denmark)

    Hindrichsen, Christian Carstensen; Pedersen, Thomas; Thomsen, Erik Vilain

    2008-01-01

    Top and bottom electrodes for screen printed piezoelectric lead zirconate titanate, Pb(ZrxTi1 - x)O3 (PZT) thick film are investigated with respect to future MEMS devices. Down to 100 nm thick E-beam evaporated Al and Pt films are patterned as top electrodes on the PZT using a lift-off process...

  9. Formation of complex wedding-cake morphologies during homoepitaxial film growth of Ag on Ag(111): atomistic, step-dynamics, and continuum modeling

    Energy Technology Data Exchange (ETDEWEB)

    Li Maozhi [Department of Physics, Renmin University of China, Beijing 100872 (China); Han, Yong [Institute of Physical Research and Technology, Iowa State University, Ames, IA 50011 (United States); Thiel, P A [Departments of Chemistry and Materials Science and Engineering and Ames Laboratory-USDOE, Iowa State University, Ames, IA 50011 (United States); Evans, J W [Department of Mathematics and Ames Laboratory-USDOE, Iowa State University, Ames, IA 50010 (United States)

    2009-02-25

    An atomistic lattice-gas model is developed which successfully describes all key features of the complex mounded morphologies which develop during deposition of Ag films on Ag(111) surfaces. We focus on this homoepitaxial thin film growth process below 200 K. The unstable multilayer growth mode derives from the presence of a large Ehrlich-Schwoebel step-edge barrier, for which we characterize both the step-orientation dependence and the magnitude. Step-dynamics modeling is applied to further characterize and elucidate the evolution of the vertical profiles of these wedding-cake-like mounds. Suitable coarse-graining of these step-dynamics equations leads to instructive continuum formulations for mound evolution.

  10. Influence of the adsorption geometry of PTCDA on Ag(111 on the tip–molecule forces in non-contact atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Gernot Langewisch

    2014-01-01

    Full Text Available Perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA adsorbed on a metal surface is a prototypical organic–anorganic interface. In the past, scanning tunneling microscopy and scanning tunneling spectroscopy studies of PTCDA adsorbed on Ag(111 have revealed differences in the electronic structure of the molecules depending on their adsorption geometry. In the work presented here, high-resolution 3D force spectroscopy measurements at cryogenic temperatures were performed on a surface area that contained a complete PTCDA unit cell with the two possible geometries. At small tip-molecule separations, deviations in the tip-sample forces were found between the two molecule orientations. These deviations can be explained by a different electron density in both cases. This result demonstrates the capability of 3D force spectroscopy to detect even small effects in the electronic properties of organic adsorbates.

  11. LEED I-V and DFT structure determination of the (√3 × √3)R30° Pb-Ag(111) surface alloy.

    Science.gov (United States)

    McLeod, I M; Dhanak, V R; Lahti, M; Matilainen, A; Pussi, K; Zhang, K H L

    2011-07-06

    The deposition of 1/3 of a monolayer of Pb on Ag(111) leads to the formation of PbAg(2) surface alloy with a long range ordered (√3 × √3)R30° superstructure. A detailed analysis of this structure using low-energy electron diffraction (LEED) I-V measurements together with density functional theory (DFT) calculations is presented. We find strong correlation between experimental and calculated LEED I-V data, with the fit between the two data sets having a Pendry's reliability factor of 0.21. The Pb atom is found to replace one top layer Ag atom in each unit cell, forming a substitutional PbAg(2) surface alloy, as expected, with the Pb atoms residing approximately 0.4 Å above the Ag atoms due to their size difference. DFT calculations are in good agreement with the LEED results.

  12. Structure and stability of acrolein and allyl alcohol networks on Ag(111) from density functional theory based calculations with dispersion corrections

    Science.gov (United States)

    Ferullo, Ricardo M.; Branda, Maria Marta; Illas, Francesc

    2013-11-01

    The interaction of acrolein and allyl alcohol with the Ag(111) surface has been studied by means of periodic density functional theory based calculations including explicitly dispersion terms. Different coverage values have been explored going from isolated adsorbed molecules to isolated dimers, interacting dimers or ordered overlayers. The inclusion of the dispersion terms largely affects the calculated values of the adsorption energy and also the distance between adsorbed molecule and the metallic surface but much less the adsorbate-adsorbate interactions. Owing to the large dipole moment of acrolein, the present calculations predict that at high coverage this molecule forms a stable extensive two-dimensional network on the surface, caused by the alignment of the adsorbate dipoles. For the case of allyl alcohol, dimers and complex networks exhibit similar stability.

  13. Analyzing relationships between surface perturbations and local chemical reactivity of metal sites: Alkali promotion of O2 dissociation on Ag(111)

    Science.gov (United States)

    Xin, Hongliang; Linic, Suljo

    2016-06-01

    Many commercial heterogeneous catalysts are complex structures that contain metal active sites promoted by multiple additives. Developing fundamental understanding about the impact of these perturbations on the local surface reactivity is crucial for catalyst development and optimization. In this contribution, we develop a general framework for identifying underlying mechanisms that control the changes in the surface reactivity of a metal site (more specifically the adsorbate-surface interactions) upon a perturbation in the local environment. This framework allows us to interpret fairly complex interactions on metal surfaces in terms of specific, physically transparent contributions that can be evaluated independently of each other. We use Cs-promoted dissociation of O2 as an example to illustrate our approach. We concluded that the Cs adsorbate affects the outcome of the chemical reaction through a strong alkali-induced electric field interacting with the static dipole moment of the O2/Ag(111) system.

  14. Investigation of electrode distance impact on PEO coating formation assisted by simulation

    Science.gov (United States)

    Ma, Xun; Blawert, Carsten; Höche, Daniel; Zheludkevich, Mikhail L.; Kainer, Karl U.

    2016-12-01

    The influence of electrode distance between anode and cathode during plasma electrolytic oxidation (PEO) process on the coating formation was investigated by combining experiments and simulation. Firstly a model was built to simulate the effect of electrode distance on the anodic current distribution using finite element analyses. Complementary, PEO coatings were fabricated on AM50 magnesium alloy in an alkaline electrolyte with different electrode distances applying constant voltage. Phase composition, coating morphology and thickness were studied for both the front and back sides of the PEO coating depending on the electrode distance. For paralleled plate-like electrodes, based on coating uniformity, an optimum electrode distance of 60-80 mm was identified under the chosen experimental conditions. Via correlation of simulation and experimental results, the influence of electrode distance on coating formation is explored. It is demonstrated that under constant voltage mode, PEO coating formation is affected by electrode distance on both front and back sides of magnesium substrates. This effect is ascribed to the influence of electrode distance on the current distribution in the bath and to the related average current density on the surfaces.

  15. Investigation of ITO free transparent conducting polymer based electrode

    Science.gov (United States)

    Sharma, Vikas; Sapna, Sachdev, Kanupriya

    2016-05-01

    The last few decades have seen a significant improvement in organic semiconductor technology related to solar cell, light emitting diode and display panels. The material and structure of the transparent electrode is one of the major concerns for superior performance of devices such as OPV, OLED, touch screen and LCD display. Commonly used ITO is now restricted due to scarcity of indium, its poor mechanical properties and rigidity, and mismatch of energy levels with the active layer. Nowadays DMD (dielectric-metal-dielectric) structure is one of the prominent candidates as alternatives to ITO based electrode. We have used solution based spin coated polymer layer as the dielectric layer with silver thin film embedded in between to make a polymer-metal-polymer (PMP) structure for TCE applications. The PMP structure shows low resistivity (2.3 x 10-4Ω-cm), high carrier concentration (2.9 x 1021 cm-3) and moderate transparency. The multilayer PMP structure is characterized with XRD, AFM and Hall measurement to prove its suitability for opto-electronic device applications.

  16. Investigation of Planar Pick-up and Kicker Electrodes for Stochastic Cooling

    CERN Document Server

    Balk, M; Weiland, T; Nolden, F; Caspers, Friedhelm

    2002-01-01

    The success of stochastic cooling crucially depends on the interaction between the beam and high frequency devices for detection (pick-up electrodes) and deflection (kicker electrodes). This contribution shows the theoretical investigation of a planar electrode to be used for stochastic cooling of secondary particles with a beta of 0.83. The coupling to the beam is realised by a slot line. Transition networks are added to extract the signal. The detailed investigation is performed via a numerical electromagnetic field analysis. The longitudinal kick of the deflectors is calculated as a function of the beam position and scaled to the applied voltage. According to the Panofsky-Wenzel theorem the transverse kick is obtained simultaneously. The electromagnetic properties of the discussed electrode are compared to existing ones as currently in use in the ESR storage ring (GSI, Darmstadt).

  17. Investigating microbial activities of electrode-associated microorganisms in real-time

    Directory of Open Access Journals (Sweden)

    Sanja eAracic

    2014-11-01

    Full Text Available Electrode-associated microbial biofilms are essential to the function of bioelectrochemical systems. These systems exist in a number of different configurations but all rely on electroactive microorganisms utilizing an electrode as either an electron acceptor or an electron donor to catalyze biological processes. Investigations of the structure and function of electrode-associated biofilms are critical to further the understanding of how microbial communities are able to reduce and oxidize electrodes. The community structure of electrode-reducing biofilms is diverse and often dominated by Geobacter spp. whereas electrode-oxidizing biofilms are often dominated by other microorganisms. The application of a wide range of tools, such as high-throughput sequencing and metagenomic data analyses, provide insight into the structure and possible function of microbial communities on electrode surfaces. However, the development and application of techniques that monitor gene expression profiles in real-time are required for a more definite spatial and temporal understanding of the diversity and biological activities of these dynamic communities. This mini-review summarizes the key gene expression techniques used in bioelectrochemical systems research, which have led to a better understanding of population dynamics, cell-cell communication and molecule-surface interactions in mixed and pure BES communities

  18. Electrochemical Investigation of Carbon as Additive to the Negative Electrode of Lead-Acid Battery

    Directory of Open Access Journals (Sweden)

    Fernandez Matthew M.

    2015-01-01

    Full Text Available The increasing demand of cycle life performance of Pb-acid batteries requires the improvement of the negative Pb electrode’s charge capacity. Electrochemical investigations were performed on Pb electrode and Pb+Carbon (Carbon black and Graphite electrodes to evaluate the ability of the additives to enhance the electrochemical faradaic reactions that occur during the cycle of Pb-acid battery negative electrode. The electrodes were characterized through Cyclic Voltammetry (CV, Potentiodynamic Polarization (PP, and Electrochemical Impedance Spectroscopy (EIS. CV revealed that the addition of carbon on the Pb electrode increased anodic and cathodicreactions by tenfold. The kinetics of PbSO4 passivation measured through PPrevealed that the addition of Carbon on the Pb electrode accelerated the oxide formation by tenfold magnitude. The Nyquist plot measured through EIS suggest that the electrochemical mechanism and reaction kinetics is under charge-transfer. From the equivalent circuit and physical model, Pb+CB1 electrode has the lowest EIS parameters while Pb+G has the highest which is attributed to faster faradaic reaction.The Nyquist plot of the passivated Pb+CB1 electrode showed double semicircular shape. The first layer represents to the bulk passive PbSO4 layer and the second layer represents the Carbon+PbSO4 layer. The enhancements upon addition of carbon on the Pb electrode were attributed to the additive’s electrical conductivity and total surface area. The electrochemical active sites for the PbSO4 to nucleate and spread increases upon addition of electrical conductive and high surface area carbon additives.

  19. Quantum mechanics capacitance molecular mechanics modeling of core-electron binding energies of methanol and methyl nitrite on Ag(111) surface

    Science.gov (United States)

    Löytynoja, T.; Li, X.; Jänkälä, K.; Rinkevicius, Z.; Ågren, H.

    2016-07-01

    We study a newly devised quantum mechanics capacitance molecular mechanics (QMCMM) method for the calculation of core-electron binding energies in the case of molecules adsorbed on metal surfaces. This yet untested methodology is applied to systems with monolayer of methanol/methyl nitrite on an Ag(111) surface at 100 K temperature. It was found out that the studied C, N, and O 1s core-hole energies converge very slowly as a function of the radius of the metallic cluster, which was ascribed to build up of positive charge on the edge of the Ag slab. Further analysis revealed that an extrapolation process can be used to obtain binding energies that deviated less than 0.5 eV against experiments, except in the case of methanol O 1s where the difference was as large as 1.8 eV. Additional QM-cluster calculations suggest that the latter error can be connected to the lack of charge transfer over the QM-CMM boundary. Thus, the results indicate that the QMCMM and QM-cluster methods can complement each other in a holistic picture of molecule-adsorbate core-ionization studies, where all types of intermolecular interactions are considered.

  20. van der Waals-corrected Density Functional Theory simulation of adsorption processes on noble-metal surfaces: Xe on Ag(111), Au(111), and Cu(111)

    CERN Document Server

    Silvestrelli, Pier Luigi

    2016-01-01

    The DFT/vdW-WF2s1 method based on the generation of localized Wannier functions, recently developed to include the van der Waals interactions in the Density Functional Theory and describe adsorption processes on metal surfaces by taking metal-screening effects into account, is applied to the case of the interaction of Xe with noble-metal surfaces, namely Ag(111), Au(111), and Cu(111). The study is also repeated by adopting the DFT/vdW-QHO-WF variant relying on the Quantum Harmonic Oscillator model which describes well many-body effects. Comparison of the computed equilibrium binding energies and distances, and the $C_3$ coefficients characterizing the adatom-surface van der Waals interactions, with available experimental and theoretical reference data shows that the methods perform well and elucidate the importance of properly including screening effects. The results are also compared with those obtained by other vdW-corrected DFT schemes, including PBE-D, vdW-DF, vdW-DF2, rVV10, and by the simpler Local Dens...

  1. The molecular dynamic study of anharmonic effects at Cu(111) and Ag(111) surfaces in the presence of Cu- and Ag-trimer island

    Energy Technology Data Exchange (ETDEWEB)

    Shah, Zulfiqar Ali [Department of Physics, Hazara University, Mansehra 21300 (Pakistan); Hayat, Sardar Sikandar, E-mail: sikandariub@yahoo.com [Department of Physics, Hazara University, Mansehra 21300 (Pakistan); Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63120 (Pakistan); Rehman, Z. [Department of Physics, Hazara University, Mansehra 21300 (Pakistan); Bouafia, Farida [LMPM, Mechanical Engineering Department, University of Sidi Bel Abbes, Sidi Bel Abbes 22000 (Algeria)

    2014-05-01

    The molecular dynamics (MD) technique based on semi-empirical potentials, is used to carry out the diffusion of Cu- and Ag-trimer on Cu- and Ag(111) surface at 300, 500 and 700 K temperatures. The constant energy MD simulation elaborates the anharmonic effects at the surface such as fissures, dislocations and vacancy creation, in the presence of island. The fissures and dislocations formed are in the range of 1.5–4 Å and 1–7 Å, respectively, from the island's position. The Cu and Ag islands both diffuse easily on Cu(111) surface, manipulate that the trend of diffusion is faster on Cu surface as compared to Ag surface. The process of breaking and opening of the island has also been observed. Moreover, a surface atom popped-up at 700 K by creating a vacancy near the Cu island on Ag surface. The rate of diffusion increases with the increase in temperature, both for homo- and hetero-cases.

  2. Quantum mechanics capacitance molecular mechanics modeling of core-electron binding energies of methanol and methyl nitrite on Ag(111) surface.

    Science.gov (United States)

    Löytynoja, T; Li, X; Jänkälä, K; Rinkevicius, Z; Ågren, H

    2016-07-14

    We study a newly devised quantum mechanics capacitance molecular mechanics (QMCMM) method for the calculation of core-electron binding energies in the case of molecules adsorbed on metal surfaces. This yet untested methodology is applied to systems with monolayer of methanol/methyl nitrite on an Ag(111) surface at 100 K temperature. It was found out that the studied C, N, and O 1s core-hole energies converge very slowly as a function of the radius of the metallic cluster, which was ascribed to build up of positive charge on the edge of the Ag slab. Further analysis revealed that an extrapolation process can be used to obtain binding energies that deviated less than 0.5 eV against experiments, except in the case of methanol O 1s where the difference was as large as 1.8 eV. Additional QM-cluster calculations suggest that the latter error can be connected to the lack of charge transfer over the QM-CMM boundary. Thus, the results indicate that the QMCMM and QM-cluster methods can complement each other in a holistic picture of molecule-adsorbate core-ionization studies, where all types of intermolecular interactions are considered.

  3. Van Der Waals-Corrected Density Functional Theory Simulation of Adsorption Processes on Noble-Metal Surfaces: Xe on Ag(111), Au(111), and Cu(111)

    Science.gov (United States)

    Silvestrelli, Pier Luigi; Ambrosetti, Alberto

    2016-10-01

    The DFT/vdW-WF2s1 method based on the generation of localized Wannier functions, recently developed to include the van der Waals interactions in the density functional theory and describe adsorption processes on metal surfaces by taking metal-screening effects into account, is applied to the case of the interaction of Xe with noble-metal surfaces, namely Ag(111), Au(111), and Cu(111). The study is also repeated by adopting the DFT/vdW-QHO-WF variant relying on the quantum harmonic oscillator model which describes well many body effects. Comparison of the computed equilibrium binding energies and distances, and the C_3 coefficients characterizing the adatom-surface van der Waals interactions, with available experimental and theoretical reference data shows that the methods perform well and elucidates the importance of properly including screening effects. The results are also compared with those obtained by other vdW-corrected DFT schemes, including PBE-D, vdW-DF, vdW-DF2, rVV10, and by the simpler local density approximation and semi-local (PBE) generalized gradient approximation approaches.

  4. Investigation of materials for inert electrodes in aluminum electrodeposition cells

    Energy Technology Data Exchange (ETDEWEB)

    Haggerty, J. S.; Sadoway, D. R.

    1987-09-14

    Work was divided into major efforts. The first was the growth and characterization of specimens; the second was Hall cell performance testing. Cathode and anode materials were the subject of investigation. Preparation of specimens included growth of single crystals and synthesis of ultra high purity powders. Special attention was paid to ferrites as they were considered to be the most promising anode materials. Ferrite anode corrosion rates were studied and the electrical conductivities of a set of copper-manganese ferrites were measured. Float Zone, Pendant Drop Cryolite Experiments were undertaken because unsatisfactory choices of candidate materials were being made on the basis of a flawed set of selection criteria applied to an incomplete and sometimes inaccurate data base. This experiment was then constructed to determine whether the apparatus used for float zone crystal growth could be adapted to make a variety of important based melts and their interactions with candidate inert anode materials. The third major topic was Non Consumable Anode (Data Base, Candidate Compositions), driven by our perception that the basis for prior selection of candidate materials was inadequate. Results are presented. 162 refs., 39 figs., 18 tabs.

  5. Investigation of top electrode for PZT thick films based MEMS sensors

    DEFF Research Database (Denmark)

    Hindrichsen, Christian Carstensen; Pedersen, Thomas; Kristiansen, Paw T.;

    2010-01-01

    In this work processing of screen printed piezoelectric PZT thick films on silicon substrates is investigated for use in future MEMS devices. E-beam evaporated Al and Pt are patterned on PZT as a top electrode using a lift-off process with a line width down to 3 mu m. Three test structures are used...

  6. Investigation of Top/bottom Electrode and Diffusion Barrier Layer for PZT thick film MEMS Sensors

    DEFF Research Database (Denmark)

    Pedersen, Thomas; Hindrichsen, Christian Carstensen; Lou-Møller, R.;

    2007-01-01

    In this work screen printed piezoelectric Ferroperm PZ26 lead zirconate titanate (PZT) thick film is used for two MEMS devices. A test structure is used to investigate several aspects regarding bottom and top electrodes. 450 nm ZrO2 thin film is found to be an insufficient diffusion barrier layer...

  7. A Novel Micro-hole Electrode Used to Investigate Electron Transfer Reactions at ITIES

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A novel micro-hole electrode was fabricated to investigate the electron transfer reaction at the interface between two immiscible electrolyte solutions (ITIES). The electron transfer reaction between ferro/ferricyanide in aqueous phase (W) and ferrocene in 1, 2-dichloroethane (O) phase was studied as a test experiment. The results showed that the diffusion coefficient obtained from the micro-hole electrode was consistent with that obtained at macro-interface. Due to its simplicity and the very small IR drop it will be a useful tool for the study of ITIES systems.

  8. A Novel Micro—hole Electrode Used to Investigate Electron Transfer Reactions at ITIES

    Institute of Scientific and Technical Information of China (English)

    DongPingZHAN; BingLiangWU

    2002-01-01

    A novel micro-hole electrode was fabricated to investigate the electron transfer reaction at the interface between two immiscible electrolyte solutions (ITIES). The electron transfer reaction between feero/ferricyanide in aqueous phase(W) and ferrocene in 1,2-dichloroethane (O) phase was studied as a test experiment. The results showed that the diffusion coefficient obtained from the micro-hole electrode was consistent with that obtained at macro-interface. Due to its simplicity and the very small IR drop it will be a useful tool for the study of ITIES systems.

  9. The Investigation of Oscillographic Chronopotentiometry at Silver Disk Electrode and Its Mechanism

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new method of oscillographic chronopotentiometry at silver disk electrode was investigated .By using it, a series of ions such as Pb, In, Cr, Tl, Bi etc. were determined. The detection limits are two or three orders of magnitude lower than those by oscillographic chronopotentiometry at mercury electrode. The proposed method is characterized by fine sensitivity、stable oscillogram and no mercury. The research on the mechanism of this method shows that these achievements are caused by the characterristics of silver electroxidation and electroreduction and the oscillographic chronopotentiometry (OC).

  10. Electrical and electromagnetic investigations for HVDC ground electrode sites in India

    Science.gov (United States)

    Manglik, A.; Verma, S. K.; Muralidharan, D.; Sasmal, R. P.

    High Voltage Direct Current (HVDC) power transmission systems require setting up of specially designed ground electrodes at terminal ends of the transmission line to close the circuit with an earth return path. The design parameters of these electrodes need the information about the electrical conductivity structure within a radius and depth of several km of the site in order to ensure that the injected current penetrates deep enough into the earth. Further, detailed conductivity structure, up to 100-200 m depth, of the electrode site covering an area of less than a sq. km is also needed to ensure safe limits for the step and touch potential at the site. Electrical and electromagnetic methods are very useful tools for this purpose. However, artificial source variants such as deep direct current (DC) resistivity sounding pose logistic problems for target depths greater than a couple of kilometers and in inaccessible areas. We have employed magnetotelluric (MT) and electrical resistivity tomography (ERT) tools to investigate the detailed deep and shallow electrical conductivity structure, respectively, of several potential sites in India for a ±800 kV, 6000 MW HVDC multi-terminal system. Investigations of a site in Assam revealed the presence of highly resistive crustal rocks at the depth of about 1.3 km beneath a thick pile of conductive sediments, rendering the site unsuitable even though the shallow conductivity was favorable. At another site identified after analyzing available geological and geophysical data, we inferred the presence of conductive structure up to at least 4.0 km depth. ERT investigation at this site revealed a favorable conductive structure except for the presence of a 20-m-thick near-surface resistive layer. This information has been useful for the electrode design. We suggest that a strategy suitably combining MT and ERT is useful in the selection of ground electrode sites.

  11. Identification of Ag-acceptors in $^{111}\\!$Ag $^{111}\\!$Cd doped ZnTe and CdTe

    CERN Document Server

    Hamann, J; Deicher, M; Filz, T; Lany, S; Ostheimer, V; Strasser, F; Wolf, H; Wichert, T

    2000-01-01

    Nominally undoped ZnTe and CdTe crystals were implanted with radioactive $^{111}\\!$Ag, which decays to $^{111}\\!$Cd, and investigated by photoluminescence spectroscopy (PL). In ZnTe, the PL lines caused by an acceptor level at 121 meV are observed: the principal bound exciton (PBE) line, the donor-acceptor pair (DAP) band, and the two-hole transition lines. In CdTe, the PBE line and the DAP band that correspond to an acceptor level at 108 meV appear. Since the intensities of all these PL lines decrease in good agreement with the half-life of $^{111}\\!$Ag of 178.8 h, both acceptor levels are concluded to be associated with defects containing a single Ag atom. Therefore, the earlier assignments to substitutional Ag on Zn- and Cd-lattice sites in the respective II-VI semiconductors are confirmed. The assignments in the literature of the S$_1$, S$_2$, and S$_3$ lines in ZnTe and the X$\\scriptstyle^\\textrm{Ag}_{1}\\,\\,,$ X$\\scriptstyle^\\textrm{Ag}_{2}$/ C$\\scriptstyle^\\textrm{Ag}_{1}\\,$ and C$\\scriptstyle^\\textrm{...

  12. Identification of Ag-acceptors in $^{111}Ag^{111}Cd$ doped ZnTe and CdTe

    CERN Document Server

    Hamann, J; Deicher, M; Filz, T; Lany, S; Ostheimer, V; Strasser, F; Wolf, H; Wichert, T

    2000-01-01

    Nominally undoped ZnTe and CdTe crystals were implanted with radioactive /sup 111/Ag, which decays to /sup 111/Cd, and investigated by photoluminescence spectroscopy (PL). In ZnTe, the PL lines caused by an acceptor level at 121 meV are observed: the principal bound exciton (PBE) line, the donor-acceptor pair (DAP) band, and the two-hole transition lines. In CdTe, the PBE line and the DAP band that correspond to an acceptor level at 108 meV appear. Since the intensities of all these PL lines decrease in good agreement with the half-life of /sup 111/Ag of 178.8 h, both acceptor levels are concluded to be associated with defects containing a single Ag atom. Therefore, the earlier assignments to substitutional Ag on Zn- and Cd-lattice sites in the respective II-VI semiconductors are confirmed. The assignments in the literature of the S/sub 1/, S /sub 2/, and S/sub 3/ lines in ZnTe and the X/sub 1//sup Ag/, X/sub 2 //sup Ag//C/sub 1//sup Ag/, and C/sub 2//sup Ag/ lines in CdTe to Ag- related defect complexes are ...

  13. Investigation on the electrocatalytic characteristics of SnO2 electrodes with nanocoating prepared by electrodeposition method

    Institute of Scientific and Technical Information of China (English)

    LIU JunFeng; FENG YuJie

    2009-01-01

    SnO2 electrodes have many advantages in the degradation of toxic or bio-refractory organic wastewater, and SnO2 is a kind of anode material which has the potential to be widely used. Electrocatalytic effi-ciency and service life of Ti\\SnO2 electrodes are key factors that can influence its applications. In order to enhance the electrocatalytic characteristics of Ti\\SnO2 electrodes, a type of electrocatalytic electrode with nanocoating was prepared by direct current (DC) electrodeposition method and thermal oxidation technique. With phenol as the model pollutant, the electrochemical degradation efficiencies of elec-trodes with nanocoating and non-nanocoating were investigated. It was demonstrated that the elec-trodes with nanocoating have higher efficiency than that of electrodes with non-nanocoating. The degradation time was decreased 33.3% for the same amount of phenol's degradation. The crystal structure of surface coating, the micrograph of electrode surface and the chemical environment of Sn and Sb in the electrode surface were analyzed with the help of XRD, SEM and XPS. The results showed that the surface of electrode was mainly SnO2 crystal with rutile structure and that much adsorbed oxygen in nanocoating was the dominant factor for enhancing the electrocatalytic characteristics.

  14. Investigation on the electrocatalytic characteristics of SnO2 electrodes with nanocoating prepared by electrodeposition method

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    SnO2 electrodes have many advantages in the degradation of toxic or bio-refractory organic wastewater,and SnO2 is a kind of anode material which has the potential to be widely used.Electrocatalytic effi-ciency and service life of Ti\\SnO2 electrodes are key factors that can influence its applications.In order to enhance the electrocatalytic characteristics of Ti\\SnO2 electrodes,a type of electrocatalytic electrode with nanocoating was prepared by direct current(DC)electrodeposition method and thermal oxidation technique.With phenol as the model pollutant,the electrochemical degradation efficiencies of elec-trodes with nanocoating and non-nanocoating were investigated.It was demonstrated that the elec-trodes with nanocoating have higher efficiency than that of electrodes with non-nanocoating.The degradation time was decreased 33.3% for the same amount of phenol’s degradation.The crystal structure of surface coating,the micrograph of electrode surface and the chemical environment of Sn and Sb in the electrode surface were analyzed with the help of XRD,SEM and XPS.The results showed that the surface of electrode was mainly SnO2 crystal with rutile structure and that much adsorbed oxygen in nanocoating was the dominant factor for enhancing the electrocatalytic characteristics.

  15. An Investigation of Groundwater Flow on a Coastal Barrier using Multi Electrode Profiling

    DEFF Research Database (Denmark)

    Poulsen, Søren Erbs; Christensen, Steen; Rasmussen, Keld Rømer;

    2008-01-01

    probes, having closely spaced electrodes from above the groundwater table to a depth of 5 m below sea level, have been installed and tested. Using this system we will monitor resistivity and thus groundwater salinity variations in space and time. Analyzing the measurements using density dependent......Preliminary geophysical and hydrogeological investigations indicate that multi-electrode profiling (MEP) can be used to monitor groundwater salinity on a coastal barrier where a shallow thin aquifer discharges to the North Sea. A monitoring system including five groups of piezometers and five MEP...... groundwater modeling we hope to be able to quantify how time varying recharge, tides, and storms hitting the barrier affect groundwater flow and discharge to the sea. At the conference we will present monitoring results from the winter and spring 2008....

  16. Electrochemical investigation of nickel pattern electrodes in H2/H2O and CO/CO2 atmospheres

    DEFF Research Database (Denmark)

    Ehn, A.; Høgh, Jens Valdemar Thorvald; Graczyk, M.;

    2010-01-01

    In this study, nickel pattern electrodes were electrochemically investigated in a three-electrode setup, operating both with H2 / H2 O and CO/ CO2 atmospheres. Heating introduced structural differences in the nickel layer among the pattern electrodes, which appear to affect the electrode...

  17. Investigation of the fabrication parameters of thick film metal oxide-polymer pH electrodes

    CERN Document Server

    Gac, A

    2002-01-01

    This thesis describes a study into the development of an optimum material and fabrication process for the production of thick film pH electrodes. These devices consist of low cost, miniature and rugged pH sensors formed by screen printing a metal oxide bearing paste onto a high temperature (approx 850 deg C) fired metal back contact supported on a standard alumina substrate. The pH sensitive metal oxide layer must be fabricated at relatively low temperatures (<300 deg C) in order to maintain the pH sensitivity of the layer and hence requires the use of a suitably stable low temperature curing binder. Bespoke fabricated inks are derived from a Taguchi style factorial experimental plans in which, different binder types, curing temperatures, hydration level and percentage mixtures of different metal oxides and layer thicknesses were investigated. The pH responses of 18 printed electrodes per batch were assessed in buffer solutions with respect to a commercial reference electrode forming a complete potentiomet...

  18. In-situ Microscopic FT-IR Spectroelectrochemical Investigation of Polythiophene Film Modified Electrode

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A polythiophene film was electrochemically deposited on a Pt micro-plate electrode and investigated by cyclic voltammetry and in-situ reflection microscopic FTIR spectroscopy. The FTIR analysis showed that the electropolymerization of thiophene on the Pt surface was affected by the surface adsorption processes of thiophene molecules. Two adsorption modes were identified. Two structure models of the polythiophene chain were observed simultaneously. It was proposed that the good conductibility of the polythiophene film was originated from a co-vibratory equilibrium of the link part of model Ⅰ and model Ⅱ.

  19. Solid State Multinuclear Magnetic Resonance Investigation of Electrolyte Decomposition Products on Lithium Ion Electrodes

    Science.gov (United States)

    DeSilva, J .H. S. R.; Udinwe, V.; Sideris, P. J.; Smart, M. C.; Krause, F. C.; Hwang, C.; Smith, K. A.; Greenbaum, S. G.

    2012-01-01

    Solid electrolyte interphase (SEI) formation in lithium ion cells prepared with advanced electrolytes is investigated by solid state multinuclear (7Li, 19F, 31P) magnetic resonance (NMR) measurements of electrode materials harvested from cycled cells subjected to an accelerated aging protocol. The electrolyte composition is varied to include the addition of fluorinated carbonates and triphenyl phosphate (TPP, a flame retardant). In addition to species associated with LiPF6 decomposition, cathode NMR spectra are characterized by the presence of compounds originating from the TPP additive. Substantial amounts of LiF are observed in the anodes as well as compounds originating from the fluorinated carbonates.

  20. Investigation of electrolyte wetting in lithium ion batteries: Effects of electrode pore structures and solution

    Science.gov (United States)

    Sheng, Yangping

    Beside natural source energy carriers such as petroleum, coal and natural gas, the lithium ion battery is a promising man-made energy carrier for the future. This is a similar process evolved from horse-powered era to engine driven age. There are still a lot of challenges ahead like low energy density, low rate performance, aging problems, high cost and safety etc. In lithium ion batteries, investigation about manufacturing process is as important as the development of material. The manufacturing of lithium ion battery, including production process (slurry making, coating, drying etc.), and post-production (slitting, calendering etc.) is also complicated and critical to the overall performance of the battery. It includes matching the capacity of anode and cathode materials, trial-and-error investigation of thickness, porosity, active material and additive loading, detailed microscopic models to understand, optimize, and design these systems by changing one or a few parameters at a time. In the manufacturing, one of the most important principles is to ensure good wetting properties between porous solid electrodes and liquid electrolyte. Besides the material surface properties, it is the process of electrolyte transporting to fill the pores in the electrode after injection is less noticed in academic, where only 2-3 drops of electrolyte are needed for lab coin cell level. In industry, the importance of electrolyte transport is well known and it is considered as part of electrolyte wetting (or initial wetting in some situations). In consideration of practical usage term, electrolyte wetting is adopted to use in this dissertation for electrolyte transporting process, although the surface chemistry about wetting is not covered. An in-depth investigation about electrolyte wetting is still missing, although it has significant effects in manufacturing. The electrolyte wetting is determined by properties of electrolyte and electrode microstructure. Currently, only viscosity

  1. Investigation of activated carbon adsorbent electrode for electrosorption-based uranium extraction from seawater

    Energy Technology Data Exchange (ETDEWEB)

    Yim, Man Sung; Ismail, Aznan Fazli [Dept. of Nuclear and Quantum Engineering (NQe), 291 Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2015-08-15

    To support the use of nuclear power as a sustainable electric energy generating technology, long-term supply of uranium is very important. The objective of this research is to investigate the use of new adsorbent material for cost effective uranium extraction from seawater. An activated carbon-based adsorbent material is developed and tested through an electrosorption technique in this research. Adsorption of uranium from seawater by activated carbon electrodes was investigated through electrosorption experiments up to 300 minutes by changing positive potentials from +0.2V to +0.8V (vs. Ag/AgCl). Uranium adsorption by the activated carbon electrode developed in this research reached up to 3.4 g-U/kg-adsorbent material, which is comparable with the performance of amidoxime-based adsorbent materials. Electrosorption of uranium ions from seawater was found to be most favorable at +0.4V (vs. Ag/AgCl). The cost of chemicals and materials in the present research was compared with that of the amidoxime-based approach as part of the engineering feasibility examination.

  2. Benchmark investigation of diamondoid-functionalized electrodes for nanopore DNA sequencing

    Science.gov (United States)

    Sivaraman, Ganesh; Amorim, Rodrigo G.; Scheicher, Ralph H.; Fyta, Maria

    2016-10-01

    Small diamond-like particles, diamondoids, have been shown to effectively functionalize gold electrodes in order to sense DNA units passing between the nanopore-embedded electrodes. In this work, we present a comparative study of Au(111) electrodes functionalized with different derivatives of lower diamondoids. Focus is put on the electronic and transport properties of such electrodes for different DNA nucleotides placed within the electrode gap. The functionalization promotes a specific binding to DNA leading to different properties for the system, which provides a tool set to systematically improve the signal-to-noise ratio of the electronic measurements across the electrodes. Using quantum transport calculations, we compare the effectiveness of the different functionalized electrodes in distinguishing the four DNA nucleotides. Our results point to the most effective diamondoid functionalization of gold electrodes in view of biosensing applications.

  3. EXPERIMENTAL INVESTIGATION ON ELECTRICAL DISCHARGE MACHINING OF TITANIUM ALLOY USING COPPER, BRASS AND ALUMINUM ELECTRODES

    Directory of Open Access Journals (Sweden)

    S. DHANABALAN

    2015-01-01

    Full Text Available In the present study, an evaluation has been done on Material Removal Rate (MRR, Surface Roughness (SR and Electrode Wear Rate (EWR during Electrical Discharge Machining (EDM of titanium alloy using copper, brass and aluminum electrodes. Analyzing previous work in this field, it is found that electrode wear and material removal rate increases with an increase current. It is also found that the electrode wear ratio increases with an increase in current. The higher wear ratio is found during machining of titanium alloy using a brass electrode. An attempt has been made to correlate the thermal conductivity and melting point of electrode with the MRR and electrode wear. The MRR is found to be high while machining titanium alloy using brass electrode. During machining of titanium alloy using copper electrodes, a comparatively smaller quantity of heat is absorbed by the work material due to low thermal conductivity. Due to the above reason, the MRR becomes very low. Duringmachining of titanium alloy using aluminium electrodes, the material removal rate and electrode wear rate are only average value while machining of titanium alloy using brass and copper electrodes.

  4. Experimental investigation of cooling of a plate by ionic wind from a corona-forming wire electrode

    Science.gov (United States)

    Elagin, I. A.; Yakovlev, V. V.; Ashikhmin, I. A.; Stishkov, Yu. K.

    2016-08-01

    We report on the results of experimental investigations of the kinematic structure of ionic wind from a wire electrode placed near a heated plate, which plays the role of the earthed electrode. Experiments are carried out in a wide range of voltages for different polarities of the wire for several values of the electrode gap. We compare the structures of the flows emerging as a result of natural convection in open air for different positions of the plate and in the presence of a fast ionic wind jet that considerably intensifies heat transfer in the boundary layer at the heated planar electrode. Local temperature distributions over the plate surface are obtained, as well as the integral dependences of the effective heat removal on the electric parameters of the corona discharge. The velocity of air flows with ionic wind reaches 4 m/s, and the heat power removed from the plate for fixed overheating increases ninefold compared to the situation with natural convection.

  5. Investigation of a new electrode array technology for a central auditory prosthesis.

    Directory of Open Access Journals (Sweden)

    Roger Calixto

    Full Text Available Ongoing clinical studies on patients recently implanted with the auditory midbrain implant (AMI into the inferior colliculus (IC for hearing restoration have shown that these patients do not achieve performance levels comparable to cochlear implant patients. The AMI consists of a single-shank array (20 electrodes for stimulation along the tonotopic axis of the IC. Recent findings suggest that one major limitation in AMI performance is the inability to sufficiently activate neurons across the three-dimensional (3-D IC. Unfortunately, there are no currently available 3-D array technologies that can be used for clinical applications. More recently, there has been a new initiative by the European Commission to fund and develop 3-D chronic electrode arrays for science and clinical applications through the NeuroProbes project that can overcome the bulkiness and limited 3-D configurations of currently available array technologies. As part of the NeuroProbes initiative, we investigated whether their new array technology could be potentially used for future AMI patients. Since the NeuroProbes technology had not yet been tested for electrical stimulation in an in vivo animal preparation, we performed experiments in ketamine-anesthetized guinea pigs in which we inserted and stimulated a NeuroProbes array within the IC and recorded the corresponding neural activation within the auditory cortex. We used 2-D arrays for this initial feasibility study since they were already available and were sufficient to access the IC and also demonstrate effective activation of the central auditory system. Based on these encouraging results and the ability to develop customized 3-D arrays with the NeuroProbes technology, we can further investigate different stimulation patterns across the ICC to improve AMI performance.

  6. Experimental Investigation into the Performance of Large-scale Earthing Electrodes%Experimental Investigation into the Performance of Large-scale Earthing Electrodes

    Institute of Scientific and Technical Information of China (English)

    D. Guo; D. Lathi; H. Griffiths; N. Harid; A. Ainsley; A. Haddad

    2011-01-01

    Analytical and numerical simulation techniques have been developed for the calculation of earth resistance/ impedance and to estimate the potential distribution in the vicinity of earth electrodes. However, very little literature is available on experimental validation of these calculation techniques. To address this, a programme of experimental tests on various earth electrodes has been carried out at the lower water reservoir of a hydro pumped-storage power station in North Wales. In this paper, the earthing test facility at Dinorwig power station is described including the details of the experimental set up. The results from experimental tests on a 5 m× 5 m earth grid, immersed in water and energized under ac, dc and impulse, are presented. The values of measured earth resistance/impedance and water surface potential distributions are compared with those obtained from analytical calculations and detailed numerical computer simulations.

  7. In-situ contact electrical resistance technique for investigating corrosion inhibitor adsorption on copper electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Moretti, G.; Quartarone, G.; Zingales, A. [Univ. of Venice (Italy). Dept. of Chemistry; Molokanov, V.V. [Russian Academy of Sciences, Moscow (Russian Federation). Inst. of Physical Chemistry

    1998-02-01

    Traditional electrochemical tests and the contact electrical resistance technique (CER) were used to investigate the effect on corrosion of pure copper (99.999 wt%) of adding benzotriazole (BTA) and 1-hydroxybenzotriazone (1-OH-BTA) to acidic solutions (sulfuric acid [H{sub 2}SO{sub 4}], pH = 1.7, and sodium sulfate [Na{sub 2}SO{sub 4}] until total sulfate [SO{sub 4}{sup 2{minus}}] concentration = 0.1 M). This technique permitted growth of oxide and/or salt films as well as adsorption of the organic inhibitors on the copper surface to be evaluated. Formation of copper oxide ([Cu{sub 2}O]{sub 2})., sulfate (CuSo{sub 4}{center_dot}5H{sub 2}O), thiocyanate (CuSCN), and halogenyde (CuI, CuBr, and CuCl) films on copper electrodes was followed in situ in sulfate solutions at various pH values under low overpotentials. Effects of pH, solution anion content, and/or the amount of BTA or 1-OH-BTA on electrical resistance (R) of the surface films formed on pure copper electrodes were treated. BTA acted as a more efficient corrosion inhibitor than 1-OH-BTA, reaching inhibition percentages (IP) of {approximately}90% compared to those of 1-OH-BTA, which reached a maximum of {approximately}76% in 2 {times} 10{sup {minus}3} M solutions. It was possible to distinguish between maximum R of the surface film, found in solutions containing BTA, associated with the adsorption of neutral inhibitor molecules, and the sharp rise in R attributable to [Cu(BTA)]{sub n} complex formation.

  8. X-ray Photoelectron Spectroscopy Investigation on Electrochemical Degradation of Proton Exchange Membrane Fuel Cell Electrodes

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma; Dhiman, Rajnish; Skou, Eivind Morten

    2015-01-01

    pressed ionomer) but have identical, commercial catalyst and catalyst loading. A significant degree of carbon corrosion, platinum migration and ionomer degradation were observed in the electrodes after the treatment. The degradation of the ionomer in the electrode is more severe than that of membrane...

  9. Investigation of ISIS and Brookhaven National Laboratory ion source electrodes after extended operation

    Energy Technology Data Exchange (ETDEWEB)

    Lettry, J.; Gerardin, A.; Pereira, H.; Sgobba, S. [CERN, 1211 Geneva 23 (Switzerland); Alessi, J. [BNL, P.O. Box 5000, Upton, New York 11973-5000 (United States); Faircloth, D. [RAL, Harwell Oxford, Didcot OX11 0QX (United Kingdom); Kalvas, T. [University of Jyvaskyla, P.O.Box 35, FI-40014 (Finland)

    2012-02-15

    Linac4 accelerator of Centre Europeen de Recherches Nucleaires is under construction and a RF-driven H{sup -} ion source is being developed. The beam current requirement for Linac4 is very challenging: 80 mA must be provided. Cesiated plasma discharge ion sources such as Penning or magnetron sources are also potential candidates. Accelerator ion sources must achieve typical reliability figures of 95% and above. Investigating and understanding the underlying mechanisms involved with source failure or ageing is critical when selecting the ion source technology. Plasma discharge driven surface ion sources rely on molybdenum cathodes. Deformation of the cathode surfaces is visible after extended operation periods. A metallurgical investigation of an ISIS ion source is presented. The origin of the deformation is twofold: Molybdenum sputtering by cesium ions digs few tenths of mm cavities while a growth of molybdenum is observed in the immediate vicinity. The molybdenum growth under hydrogen atmosphere is hard and loosely bound to the bulk. It is, therefore, likely to peel off and be transported within the plasma volume. The observation of the cathode, anode, and extraction electrodes of the magnetron source operated at BNL for two years are presented. A beam simulation of H{sup -}, electrons, and Cs{sup -} ions was performed with the IBSimu code package to qualitatively explain the observations. This paper describes the operation conditions of the ion sources and discusses the metallurgical analysis and beam simulation results.

  10. Investigation of ISIS and Brookhaven National Laboratory ion source electrodes after extended operation

    Energy Technology Data Exchange (ETDEWEB)

    Lettry J.; Alessi J.; Faircloth, D.; Gerardin, A.; Kalvas, T.; Pereira, H.; Sgobba, S.

    2012-02-23

    Linac4 accelerator of Centre Europeen de Recherches Nucleaires is under construction and a RF-driven H{sup -} ion source is being developed. The beam current requirement for Linac4 is very challenging: 80 mA must be provided. Cesiated plasma discharge ion sources such as Penning or magnetron sources are also potential candidates. Accelerator ion sources must achieve typical reliability figures of 95% and above. Investigating and understanding the underlying mechanisms involved with source failure or ageing is critical when selecting the ion source technology. Plasma discharge driven surface ion sources rely on molybdenum cathodes. Deformation of the cathode surfaces is visible after extended operation periods. A metallurgical investigation of an ISIS ion source is presented. The origin of the deformation is twofold: Molybdenum sputtering by cesium ions digs few tenths of mm cavities while a growth of molybdenum is observed in the immediate vicinity. The molybdenum growth under hydrogen atmosphere is hard and loosely bound to the bulk. It is, therefore, likely to peel off and be transported within the plasma volume. The observation of the cathode, anode, and extraction electrodes of the magnetron source operated at BNL for two years are presented. A beam simulation of H{sup -}, electrons, and Cs{sup -} ions was performed with the IBSimu code package to qualitatively explain the observations. This paper describes the operation conditions of the ion sources and discusses the metallurgical analysis and beam simulation results.

  11. Electroanalytical investigation and determination of pefloxacin in pharmaceuticals and serum at boron-doped diamond and glassy carbon electrodes.

    Science.gov (United States)

    Uslu, Bengi; Topal, Burcu Dogan; Ozkan, Sibel A

    2008-02-15

    The anodic behavior and determination of pefloxacin on boron-doped diamond and glassy carbon electrodes were investigated using cyclic, linear sweep, differential pulse and square wave voltammetric techniques. In cyclic voltammetry, pefloxacin shows one main irreversible oxidation peak and additional one irreversible ill-defined wave depending on pH values for both electrodes. The results indicate that the process of pefloxacin is irreversible and diffusion controlled on boron-doped diamond electrode and irreversible but adsorption controlled on glassy carbon electrode. The peak current is found to be linear over the range of concentration 2x10(-6) to 2x10(-4)M in 0.5M H(2)SO(4) at about +1.20V (versus Ag/AgCl) for differential pulse and square wave voltammetric technique using boron-doped diamond electrode. The repeatability, reproducibility, precision and accuracy of the methods in all media were investigated. Selectivity, precision and accuracy of the developed methods were also checked by recovery studies. The procedures were successfully applied to the determination of the drug in pharmaceutical dosage forms and humans serum samples with good recovery results. No electroactive interferences from the excipients and endogenous substances were found in the pharmaceutical dosage forms and biological samples, respectively.

  12. LiCoO2 electrode/electrolyte interface of Li-ion batteries investigated by electrochemical impedance spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The storage behavior and the first delithiation of LiCoO2 electrode in 1 mol/L LiPF6-EC:DMC:DEC electrolyte were investigated by electrochemical impedance spectroscopy (EIS). It has found that, along with the increase of storage time, the thickness of SEI film increases, and some organic carbonate lithium compounds are formed due to spontaneous reactions occurring between the LiCoO2 electrode and the electrolyte. When electrode potential is changed from 3.8 to 3.95 V, the reversible breakdown of the resistive SEI film occurs, which is attributed to the reversible dissolution of the SEI film component. With the increase of electrode potential, the thickness of SEI film increases rapidly above 4.2 V, due to overcharge reactions. The inductive loop observed in impedance spectra of the LiCoO2 electrode in Li/LiCoO2 cells is attributed to the formation of a Li1-xCoO2/LiCoO2 concentration cell. Moreover, it has been demonstrated that the lithium-ion insertion-deinsertion in LiCoO2 hosts can be well described by both Langmuir and Frumkin insertion isotherms, and the symmetry factor of charge transfer has been evaluated at 0.5.

  13. An Investigation of Ionic Flows in a Sphere-Plate Electrode Gap

    Science.gov (United States)

    Z. Alisoy, H.; Alagoz, S.; T. Alisoy, G.; B. Alagoz, B.

    2013-10-01

    This paper presents analyses of ion flow characteristics and ion discharge pulses in a sphere-ground plate electrode system. As a result of variation in electric field intensity in the electrode gap, the ion flows towards electrodes generate non-uniform discharging pulses. Inspection of these pulses provides useful information on ionic stream kinetics, the effective thickness of ion cover around electrodes, and the timing of ion clouds discharge pulse sequences. A finite difference time domain (FDTD) based space-charge motion simulation is used for the numerical analysis of the spatio-temporal development of ionic flows following the first Townsend avalanche, and the simulation results demonstrate expansion of the positive ion flow and compression of the negative ion flow, which results in non-uniform discharge pulse characteristics.

  14. XPS investigations of electrolyte/electrode interactions for various Li-ion battery materials

    Energy Technology Data Exchange (ETDEWEB)

    Oswald, S.; Mikhailova, D.; Scheiba, F.; Reichel, P.; Fiedler, A.; Ehrenberg, H. [IFW Dresden, Dresden (Germany)

    2011-05-15

    For future Li-ion battery applications the search for both new design concepts and materials is necessary. The electrodes of the batteries are always in contact with electrolytes, which are responsible for the transport of Li ions during the charging and discharging process. A broad range of materials is considered for both electrolytes and electrodes so that very different chemical interactions between them can occur, while good cycling behavior can only be obtained for stable solid-electrolyte interfaces. X-ray photoelectron spectroscopy (XPS) was used to study the most relevant interactions between various electrode materials in contact with different electrolyte solutions. It is shown how XPS can provide useful information on reactivities and thus preselect suitable electrode/electrolyte combinations, prior to electrochemical performance tests. (orig.)

  15. Investigation of electro-oxidation activity of Pt-CNTs/GC electrodes

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The morphology and structure of Pt-CNTs/GC electrodes were characterized via Transmission Electron Microscopy (TEM) and selected area electron diffraction.The electro-oxidation behavior of CO and methanol on Pt-CNTs/GC electrodes were studied with cyclic voltommograms or chronoamperometry.Three oxidation peaks were observed for CO absorbed on PtCNTs/GC electrodes.Methanol was found to be dissociated spontaneously on the electrode to produce a strong absorbed intermediate CO.Among the three oxidation peaks,peak Ⅰ was presumed to be due to the bridged CO absorption while peaks Ⅱ and Ⅲ were attributed to the split in the linear CO which is absorbed on the PtCNTs/GC nanocluster with different particle size and Pt film.The oxidation current of methanol on the Pt-CNTs/GC electrode did not always increase with the increase in the amount of Pt loading,The result indicates that there is an optimal Pt loading for methanol oxidation.It is necesSary to select the catalyst with proper Pt loading when the anode of a direct-methanol fuel cell is prepared.

  16. Electrochemical Investigation of Catechol at Poly(niacinamide Modified Carbon Paste Electrode: A Voltammetric Study

    Directory of Open Access Journals (Sweden)

    A. B. Teradale

    2016-01-01

    Full Text Available A polymeric thin film modified electrode, that is, poly(niacinamide modified carbon paste electrode (MCPE, was developed for the electrochemical determination of catechol (CC by using cyclic voltammetric technique. Compared to bare carbon paste electrode (BCPE, the poly(niacinamide MCPE shows good electrocatalytic activity towards the oxidation of catechol in phosphate buffer solution (PBS of physiological pH 7.4. All experimental parameters were optimized. Poly(niacinamide modified carbon paste electrode gave a linear response between concentration of CC and its anodic peak current in the range within 20.6–229.0 μM. The limit of detection (3S/M and limit of quantification (10S/M were 1.497 μM and 4.99 μM, respectively. From the study of scan rate variation, the electrode process was found to be adsorption-controlled. The involvement of protons and electrons in the oxidation of CC was found to be equal. The probable electropolymerisation mechanism of niacinamide was proposed. Finally, this method can be used in development of a sensor for sensitive determination of CC.

  17. Investigation of Interface between Ge Electrodes and Ionic Liquid Electrolytes for Electric Double Layer Capacitors

    Science.gov (United States)

    Abeysinghe, R. M.; Oguchi, H.; Kuwano, H.

    2016-11-01

    This study discusses novel way of use of ionic liquids to develop Ge-based electrodes for electric double layer capacitors (EDLC). We found that ionic liquids change their electrochemical properties depending on the amount of the absorbed water. Wet ionic liquids work as solvents to dissolve Ge and make porous structures, whereas dry ones work as electrolytes of the EDLCs. The former property was used to increase surface area of the electrodes which is desired to increase the capacity of EDLCs. This method showed another advantage in contrast to the dry ionic liquids; wet ones could fill the complex Ge pores in parallel to porous structure formation. Finally, after porous formation, we dried the ionic liquid at 100 °C and prepared the EDLCs composed of Ge porous electrodes. Cyclic voltammetry and impedance measurements indicated that the obtained devices can work as EDLCs.

  18. Investigation of Electrolysis Process Performance by Graphite Electrodes for De-Colorization of Phenolphthalein and Phenol Red from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Mohamadreza Massoudinejad

    2015-11-01

    Full Text Available This study elucidates the de-colorization of phenolphthalein and phenol red from aqueous solution through electrochemical oxidation technique. An electrochemical reactor had 1 liter volume that used 2 graphite electrodes. Effect of electric power voltage, inter electrode distance and electrolyte concentration was investigated in this system. It was found that the optimum conditions for completely removal of phenolphthalein was at voltage of 48 V, retention time of 9 minutes, distance between the electrode of 5 cm, and the salt concentration of 1.5 g/l. Also completely removal of phenol red was at voltage of 48 V, retention time of 8 minutes, distance between the electrode of 5 cm, and the salt concentration of 2 g/l. Phenol red and phenolphthalein COD removal efficiency was 85 and 80 percent respectively. The results suggest that the electrolysis process is an effective way to removal of phenolphthalein and phenol red color from effluent, because of it can completely remove the color in a short time.

  19. Investigation of gas concentration cell based on LiSiPO electrolyte and Li2CO3, Au electrode

    Institute of Scientific and Technical Information of China (English)

    ZHU YongMing; CHU WingFong; WEPPNER Werner

    2009-01-01

    Solid lithium ion conducting electrochemical cells using LiSiPO as solid electrolyte and Li2CO3 mixed with Au as electrodes were prepared and employed as chemical sensors for the detection of CO2 gas.The EMF of the cell depends on the concentration of CO2 in air according to the partial pressure de-pendence of Nernst's law in the investigated range from 100 to 2000 ppm over the temperature range from 473 K to 673 K.

  20. Self-assembled structures of 4‧-([2,2‧:6‧,2″-terpyridine]-4‧-yl)-[1,1‧-phenyl]-4-carboxylic acid molecules induced by metal atoms on ag(111) surface

    Science.gov (United States)

    Ling, Jie; Lu, Yan; Liu, Lacheng; Liu, Xiaoqing; Wang, Li

    2016-07-01

    The self-assembled supramolecular structures of 4‧-([2,2‧:6‧,2″-terpyridine]-4‧-yl)-[1,1‧-phenyl]-4-carboxylic acid (Y) molecules on Ag(111) surface induced by metal elements have been studied by scanning tunneling microscopy. After annealing, the as-deposited monolayer of Y molecules shows four kinds of well-ordered structures due to the competition between dipole interaction, hydrogen bonding and Van der Waals interaction. Introduced Cu atoms drive ordered monolayer into a self-assembled supramolecular structure with bright spots. Deposited Ag atoms cause the monolayer change to a windmill shape self-assembled supramolecular structure. Though the Cu and Ag are in the same group of the periodic table, a Cu atom connects two COOH groups and an Ag atom trends to bind to three COOH groups during the formation of metal-organic bonding within both induced structures. Such result suggests that the self-assembled structures formed by metal-organic coordination bonding can be controlled by choosing the number of metal-organic coordination bonds, which can be helpful to design metal-organic molecular architectures comprising functional building blocks.

  1. Experimental and modeling investigations on the effects of electrode flooding on the performance of PEM fuel cells

    Science.gov (United States)

    Lin, Guangyu

    Electrode flooding, one of the major causes of poor performance of a proton exchange membrane (PEM) fuel cell, is still not fully understood. However, a comprehensive understanding of this phenomenon and the dynamics of water in the electrode is critical to the optimization of the performance of PEM fuel cells. Mathematical models were developed to study the effect of electrode flooding on the fuel cell performance. Experiments were also conducted to investigate the effect of the thickness and wetproof level of gas diffusion media on the electrode flooding level and cell performance. The modeling and experimental studies showed that liquid water accumulated in the gas diffusion and catalyst layers if it was not removed efficiently. Excessive liquid water accumulation could lead to electrode flooding and significantly impact the fuel cell performance. Any means that could facilitate liquid water removal from the cathode were found to enhance the cell performance. High operating temperature, high in-plane liquid water permeability of the gas diffusion layer, more channels and smaller shoulder widths were predicted to increase the fuel cell performance. The decrease in the in-plane electronic conductivity of the gas diffusion layer was not found to affect the fuel cell performance; however, a highly non-uniform distribution of the electronic current density was observed within the electrode. Excessive catalyst loading would not improve the fuel cell performance. On the contrary, it might reduce the fuel cell performance due to the increased thickness of the catalyst layer. Adding polytetrafluroethylene (PTFE) to the gas diffusion layer could enhance gas and water transport when a fuel cell operated under flooding situation. But excessive PTFE loading may make the electrodes more prone to flooding. It was also found that a thinner gas diffusion material without the microporous layer was more sensitive to water accumulation than a thicker one. Higher performance was

  2. Investigation of a Nanophotonic Sensor with Electrode Modified by Semiconductor Quantum Dots

    Directory of Open Access Journals (Sweden)

    O.A. Sushko

    2014-10-01

    Full Text Available This paper focuses on optical sensors, namely nanophotonic ones intended for liquid media contained polynuclear aromatics assay. Developed by us nanophotonic sensor includes optically transparent working electrode modified by quantum-dimensional structures such as spherical semiconductor quantum dots (QDs. Monomolecular layer of QDs is plotted onto the electrode by Langmuir-Blodgett technology. Particular attention is paid to the processes of assay in nanophotonic sensor. As an analyte we used polycyclic aromatic hydrocarbon (PAH such as benzo[a]pyrene (BP, which is known for its carcinogenic properties. The developed nanophotonic sensor can be used in ecology for organic carcinogens detection in water objects of environment as well as for biomedical, physical chemical assays and some others.

  3. Investigation of a Solution-Processable, Nonspecific Surface Modifier for Low Cost, High Work Function Electrodes.

    Science.gov (United States)

    Hinckley, Allison C; Wang, Congcong; Pfattner, Raphael; Kong, Desheng; Zhou, Yan; Ecker, Ben; Gao, Yongli; Bao, Zhenan

    2016-08-03

    We demonstrate the ability of the highly fluorinated, chemically inert copolymer poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) to significantly increase the work function of a variety of common electrode materials. The work function change is hypothesized to occur via physisorption of the polymer layer and formation of a surface dipole at the polymer/conductor interface. When incorporated into organic solar cells, an interlayer of PVDF-HFP at an Ag anode increases the open circuit voltage by 0.4 eV and improves device power conversion efficiency by approximately an order of magnitude relative to Ag alone. Solution-processable in air, PVDF-HFP thin films provide one possible route toward achieving low cost, nonreactive, high work function electrodes.

  4. Investigation of Machine-ability of Inconel 800 in EDM with Coated Electrode

    Science.gov (United States)

    Karunakaran, K.; Chandrasekaran, M.

    2017-03-01

    The Inconel 800 is a high temperature application alloy which is classified as a nickel based super alloy. It has wide scope in aerospace engineering, gas Turbine etc. The machine-ability studies were found limited on this material. Hence This research focuses on machine-ability studies on EDM of Inconel 800 with Silver Coated Electrolyte Copper Electrode. The purpose of coating on electrode is to reduce tool wear. The factors pulse on Time, Pulse off Time and Peck Current were considered to observe the responses of surface roughness, material removal rate, tool wear rate. Taguchi Full Factorial Design is employed for Design the experiment. Some specific findings were reported and the percentage of contribution of each parameter was furnished

  5. Mass spectrometry investigations on electrolyte degradation products for the development of nanocomposite electrodes in lithium ion batteries.

    Science.gov (United States)

    Gireaud, Laurent; Grugeon, Sylvie; Pilard, Serge; Guenot, Pierre; Tarascon, Jean-Marie; Laruelle, Stephane

    2006-06-01

    In the continuing challenge to find new routes to improve the performance of commercial lithium ion batteries cycling in alkyl carbonate-based electrolyte solutions, original designs, and new electrode materials are under active worldwide investigation. Our group has focused on the electrochemical behavior of a new generation of nanocomposite electrodes showing improved capacities (up to 3 times the capacity of conventional electrode materials). However, moving down to "nanometric-scale" active materials leads to a significant increase in electrolyte degradation, compared to that taking place within commercial batteries. Postmortem electrolyte studies on experimental coin cells were conducted to understand the degradation mechanisms. Structural analysis of the organic degradation products were investigated using a combination of complementary high-resolution mass spectrometry techniques: desorption under electron impact, electrospray ionization, and gas chromatography coupled to a mass spectrometer equipped with electron impact and chemical ionization ion sources. Numerous organic degradation products such as ethylene oxide oligomers (with methyl, hydroxyl, phosphate, and methyl carbonate endings) have been characterized. In light of our findings, possible chemical or electrochemical pathways are proposed to account for their formation. A thorough knowledge of these degradation mechanisms will enable us to propose new electrolyte formulations to optimize nanocomposite-based lithium ion battery performance.

  6. Investigation on the Electrochemical Polymerization of Catechol by Means of Rotating Ring—disk Electrode

    Institute of Scientific and Technical Information of China (English)

    孔泳; 穆绍林

    2003-01-01

    The electrolysis of catechol was studied in the pH values of 1 to 10. The results from the rotating ring-disk electrode (RRDE) experiments show that at low pH values,the electrochemical polymerization of catechol was performed by one step,and at higher pH values,the electrochemical polymerization of catechol was carried out by two steps,i.e.oxidation of catechol and followed by polymerization.The intermediates generated at the disk were detected at the ring electrode in the ring potential region of -0.2 to 0 V(vs.Ag/AgCl).One of reasons for the decrease in the ratio of ir to id with increasing the ring potential is caused by formation of positively charged intermediates at the disk electrode.This ratio increases with increasing the rotation rate of the RRDE,which indicates that the intermediates are not stable.A shielding effect during polymerization of catechol was observed when the ring potential was set at 0.1 V (vs.Ag/AgCl).The electron spin resonance(ESR) of polycatechol show that polycatechol possesses unpaired electrons.The images of polycatechol films synthesized at differentconditions are described.

  7. In Situ Radiographic Investigation of (De)Lithiation Mechanisms in a Tin-Electrode Lithium-Ion Battery.

    Science.gov (United States)

    Sun, Fu; Markötter, Henning; Zhou, Dong; Alrwashdeh, Saad Sabe Sulaiman; Hilger, Andre; Kardjilov, Nikolay; Manke, Ingo; Banhart, John

    2016-05-10

    The lithiation and delithiation mechanisms of multiple-Sn particles in a customized flat radiography cell were investigated by in situ synchrotron radiography. For the first time, four (de)lithiation phenomena in a Sn-electrode battery system are highlighted: 1) the (de)lithiation behavior varies between different Sn particles, 2) the time required to lithiate individual Sn particles is markedly different from the time needed to discharge the complete battery, 3) electrochemical deactivation of originally electrochemically active particles is reported, and 4) a change of electrochemical behavior of individual particles during cycling is found and explained by dynamic changes of (de)lithiation pathways amongst particles within the electrode. These unexpected findings fundamentaly expand the understanding of the underlying (de)lithiation mechanisms inside commercial lithium-ion batteries (LIBs) and would open new design principles for high-performance next-generation LIBs.

  8. Investigation of the Dynamics of a Clamped-Clamped Microbeam Near the Third Mode Using a Partial Electrode

    KAUST Repository

    Masri, Karim M.

    2014-08-17

    We present an investigation of the dynamics of a clamped-clamped microbeam excited electrostatically near its third mode. To maximize the response at the third mode, a partial electrode configuration is utilized. A multi-mode Galerkin method is used to develop a reduced order model (ROM) of the beam. A shooting method to find the periodic motion is utilized to generate frequency response curves. The curves show hardenining behavior and dynamic pull-in. We show that the dynamic amplitude of the partial configuration is higher than that of a full electrode configuration. These results are promising for the use of higher-order modes for mass detection and for ultra sensitive resonant sensors.

  9. Investigations of spectral characteristics of modified photo-electrodes made of TiO{sub 2} and SrTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Sarkisyan, A.G.; Aroutiounian, V.M.; Shahnazaryan, G.E.; Arakelyan, V.M.; Zargaryan, Y.G.; Begoyan, K.H. [Yerevan State Univ., Department of Physics of Semiconductors, Yerevan (Armenia); Turner, J.A. [National Renewable Energy Laboratory, Golden, Colorado (United States)

    2003-09-01

    The photocurrent spectral dependences of ceramic photo-electrodes made of semiconductor oxides TiO{sub 2} and SrTiO{sub 3} modified by means of partial reduction, doped with impurities or fluorinated are investigated. The spectral distribution of the quantum yield is calculated and the character of the interband optical transitions near the edge of the fundamental absorption of the semiconductor photo-electrode is investigated. The presence of two direct and two indirect optical transitions in the investigated semiconductor photo-electrodes is established. The threshold photon energies corresponding to these transitions are calculated. (authors)

  10. Numerical Investigation of Thermal Effect in Plasma Electrode Pockels Cell for High Average Power

    Institute of Scientific and Technical Information of China (English)

    CAO Ding-Xiang; ZHANG Xiong-Jun; ZHENG Wan-Guo; HE Shao-Bo; SUI Zhan

    2006-01-01

    @@ The average power of a Pockels cell is limited by thermal effects arising from the optical absorption of the laser pulse. These thermal effects can be managed by configuring the switch as a plasma-electrode thin plate Pockels cell, which works under heat-capacity operation. Simulation results show that, based on KD*P (in thickness 0.5cm) at an average power loading of 1 kW, the aperture integrated depolarization loss at 1.06 um is less than 10% in 5min working time.

  11. Investigation of Electrochemical Behaviour of Quercetin on the Modified Electrode Surfaces with Procaine and Aminophenyl in Non-Aquous Medium

    Directory of Open Access Journals (Sweden)

    Ibrahim Ender Mulazimoglu

    2008-01-01

    Full Text Available In this study, cyclic voltammetry and electrochemical ımpedance spectroscopy have been used to investigate the electrochemical behaviour of quercetin (3,3′,4′,5,7-pentahydroxyflavone on the procaine and aminophenyl modified electrode. The modification of procaine and aminophenyl binded electrode surface with quercetin was performed in +0,3/+2,8 V (for procaine and +0,4/+1,5 V (for aminophenyl potential range using 100 mV s-1 scanning rate having 10 cycle. A solution of 0.1 M tetrabutylammonium tetrafluoroborate in acetonitrile was used as a non-aquous solvent. For the modification process a solution of 1 mM quercetin in 0.1 M tetrabutylammonium tetrafluoroborate was used. In order to obtain these two surface, a solution of 1 mM procaine and 1 mM nitrophenyl diazonium salt in 0.1 M tetrabutylammonium tetrafluoroborate was used. By using these solutions bare glassy carbon electrode surface was modified. Nitrophenyl was reduced to amine group in 0.1 M HCl medium on the nitrophenyl modified glassy carbon elelctrode surface. Procaine modified glassy carbon electrode surface was quite electroactive. Although nitrophenyl modified glassy carbon elelctrode surface was electroinactive, it was activated by reducing nitro group into amine group. For the characterization of the modified surface 1 mM ferrocene in 0.1 M tetrabutylammonium tetrafluoroborate for cyclic voltammetry and 1 mM ferricyanide/ferrocyanide (1:1 mixture in 0,1 M KCl for electrochemical impedance spectroscopy were used.

  12. Ionic liquid modified carbon paste electrode and investigation of its electrocatalytic activity to hydrogen peroxide

    Indian Academy of Sciences (India)

    Erhan Canbay; Hayati Türkmen; Erol Akyilmaz

    2014-05-01

    This paper reports on the preparation and advantages of novel amperometric biosensors in the presence of hydrophobic ionic liquid (IL), 1-methyl-3-butylimidazolium bromide ([MBIB]). Carbon paste bio-sensor has been constructed by entrapping horseradish peroxidase in graphite and IL mixed with paraffin oil as a binder. The resulting IL/graphite material brings new capabilities for electrochemical devices by combining the advantages of ILs composite electrodes. Amounts of H2O2 were amperometrically detected by monitoring current values at reduction potential (–0.15 V) of K3Fe(CN)6. Decrease in biosensor responses were linearly related to H2O2 concentrations between 10 and 100 M with 2 s response time. Limit of detection of the biosensor were calculated to be 3.98 M for H2O2. In the optimization studies of the biosensor some parameters such as optimum pH, optimum temperature, enzyme amount, interference effects of some substances on the biosensor response, reproducibility and storage stability were carried out. The promising results are ascribed to the use of an ionic liquid, which forms an excellent charge-transfer bridge and wide electrochemical windows in the bulk of carbon paste electrode.

  13. Comparative Analysis of Cobalt Oxide Nanoisland Stability and Edge Structures on Three Related Noble Metal Surfaces: Au (111), Pt (111) and Ag (111)

    DEFF Research Database (Denmark)

    Fester, Jakob; Bajdich, Michal; Walton, Alexander

    2016-01-01

    Metal oxide nanostructures and thin films grown on metallic substrates have attracted strong attention as model catalysts and as interesting inverse catalyst systems in their own right. In this study, we investigate the role of metal support in the growth and stabilization of cobalt oxide nanostr...

  14. Synthesis and Investigation of Electrical Properties of Nanopowders Produced by Spark Erosion of Silver Electrodes in the Air

    Directory of Open Access Journals (Sweden)

    Alexey Efimov

    2016-12-01

    Full Text Available The synthesis parameters and results of investigation of electrical properties of nanopowders produced by a spark erosion of silver electrodes in the air are presented. The powders are composed mostly of metallic silver (52.9 wt. % and silver nitrate (46.5 wt. % particles with the size less than 50 nm as determined from the transmission electron microscopy images and their specific surface area is ranging from 4 to 11 m2/g. The powder production rate is estimated at 0.4 g/h. The corresponding particulate films demonstrated the ultimate resistivity of 3∙10–4 Ω∙cm at room temperature.

  15. Comprehensive Investigation of Silver Nanoparticle/Aluminum Electrodes for Copper Indium Sulfide/Polymer Hybrid Solar Cells

    DEFF Research Database (Denmark)

    Arar, Mario; Pein, Andreas; Haas, Wernfried

    2012-01-01

    Electrode materials are primarily chosen based on their work function to suit the energy levels of the absorber materials. In this paper, we focus on the modification of aluminum cathodes with a thin silver interlayer (2 nm) in copper indium sulfide/poly[(2,7-silafluorene)-alt-(4,7-di-2-thienyl-2...... nanoparticles in an aluminum oxide matrix between the absorber layer and the aluminum cathode. In combination with complementary optical investigations, the origin of the improvement is ascribed to a facilitated charge extraction....

  16. Structural and electrochemical investigation of waste newspaper based electrodes for supercapacitor applications

    Directory of Open Access Journals (Sweden)

    Adinaveen T.

    2016-06-01

    Full Text Available There is a general consensus to develop renewable energy storage and conversion technologies to replace fossil fuel energy for sustainable development. Currently, the development of high performance energy storage and conversion devices is an important step on the road to alternative energy technologies. With a special focus on the upgradation of waste to valuable energy, this paper presents an effective synthetic method that utilizes waste newspapers as the precursor to prepare the activated carbon electrodes by the pyrolysis and chemical activation processes. The amorphous nature and surface morphology of the carbon samples were confirmed by XRD and SEM analysis, respectively. Activated waste newspaper carbon (AWNP showed good electrochemical properties at 800 °C and its specific capacitance at a scan rate of 2 mV/s was found to be 380 F/g. It is important to mention that the source of the raw material is cost effective and suitable for green technology.

  17. CO adsorption on electrode of Pt nanoparticles investigated by cyclic voltammetry and in situ FTIR spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Pt nanoparticles were prepared by the chemical reduction method. The average diameter of Pt nanoparticles was determined to be 2.5 nm by TEM. The electrochemical properties of Pt nanoparticles were studied by cyclic voltammetry. In comparison with massive Pt, the oxidation current peak of CO adsorbed on Pt nanoparticles is broader. Twin adsorbates of CO on Pt nanoparticles were determined by in situ FTIRS for the first time. It has revealed that the linear and twin-bonded CO can be converted into bridge-bonded CO with the variation of electrode potential. A series of special properties of Pt nanoparticles, such as enhanced IR absorption of CO adsorbates, were also observed.

  18. Experimental and theoretical investigations of functionalized boron nitride as electrode materials for Li-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Fan; Nemeth, Karoly; Bareño, Javier; Dogan, Fulya; Bloom, Ira D.; Shaw, Leon L.

    2016-01-01

    The feasibility of synthesizing functionalized h-BN (FBN) via the reaction between molten LiOH and solid h-BN is studied for the first time and its first ever application as an electrode material in Li-ion batteries is evaluated. Density functional theory (DFT) calculations are performed to provide mechanistic understanding of the possible electrochemical reactions derived from the FBN. Various materials characterizations reveal that the melt-solid reaction can lead to exfoliation and functionalization of h-BN simultaneously, while electrochemical analysis proves that the FBN can reversibly store charges through surface redox reactions with good cycle stability and coulombic efficiency. DFT calculations have provided physical insights into the observed electrochemical properties derived from the FBN.

  19. Novel 3D plasmonic nano-electrodes for cellular investigations and neural interfaces

    Science.gov (United States)

    Malerba, Mario; Dipalo, Michele; Messina, Gabriele C.; Amin, Hayder; La Rocca, Rosanna; Shalabaeva, Victoria; Simi, Alessandro; Maccione, Alessandro; Berdondini, Luca; De Angelis, Francesco

    2014-08-01

    We propose the development of an innovative plasmonic-electronic multifunctional platform, capable at the same time of performing chemical analysis and electronic recordings from a cellular interface. The system, based on 3D hollow metallic nanotubes, integrated on customized multi-electrode-arrays, allows the study of neuronal signaling over different lengths, spanning from the molecular, to the cellular, to the network scale. Here we show that the same structures are efficient electric field enhancers, despite the continuous metal layer at the base, which connects them to the electric components of the integrated circuits. The methodology we propose, due to its simplicity and high throughput, has the potential for further improvements both in the field of plasmonics, and in the integration on large areas of commercial active electronic devices.

  20. The use of single-electrode wireless EEG in biobehavioral investigations.

    Science.gov (United States)

    Poltavski, Dmitri V

    2015-01-01

    The purpose of this chapter is to introduce novice and intermediate EEG researchers to a convenient and user-friendly EEG system from NeuroSky, Inc. In our recent study we were interested in changes in the frontal cortical EEG activity of healthy adults as a function of accommodative stress during performance of a sustained attention task. We used a commercially available low-cost wireless EEG device from NeuroSky (MindSet), which has a single active Fp1 dry electrode capable of recording research-grade EEG coupled with powerful noise-filtering and data software support. The convenience and ease-of-use of MindSet is further enhanced with validated eSense meters of Attention and Meditation. In this chapter we also provide additional data analytic support for EEG power spectrum using SPSS syntax commonly used in many biobehavioral sciences.

  1. Investigation of membrane electrode assemblies (MEAs) for efficient and optimum performance of polymer electrolyte membrane (PEM) fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Okafor, A.C.; Mogbo, H.M.C. [Missouri Univ. of Science and Technology, Rolla, MO (United States). Dept. of Mechanical and Aerospace Engineering

    2009-07-01

    The core component of a proton exchange membrane (PEM) fuel cell is the membrane electrode assembly (MEA) which includes an assembled stack of ion exchange membrane reaction catalysts, and the electrodes that converts hydrogen ions into electricity. This study investigated various MEAs in an effort to improve fuel cell performance and durability. First, a literature review of different commercially available and innovative PEM fuel cell MEAs was conducted. The best performing MEAs were then investigated in terms of fuel cell output voltage, operating temperature, thermal and chemical stability, methanol permeability, proton conductivity, and hydrogen crossover. The selected MEAs based on their high output voltage, ability to withstand chemical/radical attacks, overall fuel cell performance, and other excellent physical properties were identified as phosphoric acid-doped polybenzimidazole (PBI/H{sub 3}PO{sub 4}), disulfonated poly(sulfide sulfone)s (SPSSF), and Nafion 212. Finally, in-house designed and manufactured bipolar plates of different materials and flow field configurations are being used to validate these 3 identified MEAs in a single fuel cell and 3 fuel cell stacks.

  2. Investigation Of The EMF Versus State Of Charge Behavior Of Individual Electrodes In New And Cycled Sony 18650 HC Cells

    Science.gov (United States)

    Dudley, G.; Mattle, T.

    2011-10-01

    Individual electrode EMFs of new and cycled Sony 18650 HC cells have been measured with the help of a lithium reference electrode inserted into complete cells. Results have revealed the relative contribution of each electrode to voltage hysteresis (the difference in cell EMF between charge and discharge at the same state of charge).They have also shown changes to the shape of the positive electrode EMF versus state of charge in cycled compared to beginning of life cells.

  3. Structural investigation of MF, RF and DC sputtered Mo thin films for backside photovoltaic electrode

    Science.gov (United States)

    Małek, Anna K.; Marszałek, Konstanty W.; Rydosz, Artur M.

    2016-12-01

    Recently photovoltaics attracts much attention of research and industry. The multidirectional studies are carried out in order to improve solar cells performance, the innovative materials are still searched and existing materials and technology are optimized. In the multilayer structure of CIGS solar cells molybdenum (Mo) layer is used as a back contact. Mo layers meet all requirements for back side electrode: low resistivity, good adhesion to the substrate, high optical reflection in the visible range, columnar structure for Na ions diffusion, formation of an ohmic contact with the ptype CIGS absorber layer, and high stability during the corrosive selenization process. The high adhesion to the substrate and low resistivity in single Mo layer is difficult to be achieved because both properties depend on the deposition parameters, particularly on working gas pressure. Therefore Mo bilayers are applied as a back contact for CIGS solar cells. In this work the Mo layers were deposited by medium frequency sputtering at different process parameters. The effect of substrate temperature within the range of 50°C-200°C and working gas pressure from 0.7 mTorr to 7 mTorr on crystalline structure of Mo layers was studied.

  4. Investigations of Thallium(Ⅰ) Underpotential Deposition on the Silver Rotating Disk Electrode and Its Analytical Application

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The cyclic voltammetry(CV) and the square-wave technique were used for the investigations of thallium(Ⅰ) underpotential deposition(UPD) on the silver electrode. A solution of 10 \\{mmol/L\\} HClO4+10 mmol/L NaCl was selected as the supporting electrolyte. The calibration plots for Tl(Ⅰ) concentration in the range of 2×10-9—1×10-7 mol/L were obtained. The detection limit was 5×10-10 mol/L. For the solutions of 4.0×10-9 mol/L thallium added before the urine sample pretreatment procedure, the average recovery was 105.6% with a relative standard deviation(RSD) of 15.5%.

  5. Investigation of Coral-Like Cu2O Nano/Microstructures as Counter Electrodes for Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Chih-Hung Tsai

    2015-08-01

    Full Text Available In this study, a chemical oxidation method was employed to fabricate coral-like Cu2O nano/microstructures on Cu foils as counter electrodes (CEs for dye-sensitized solar cells (DSSCs. The Cu2O nano/microstructures were prepared at various sintering temperatures (400, 500, 600 and 700 °C to investigate the influences of the sintering temperature on the DSSC characteristics. First, the Cu foil substrates were immersed in an aqueous solution containing (NH42S2O8 and NaOH. After reacting at 25 °C for 30 min, the Cu substrates were converted to Cu(OH2 nanostructures. Subsequently, the nanostructures were subjected to nitrogen sintering, leading to Cu(OH2 being dehydrated into CuO, which was then deoxidized to form coral-like Cu2O nano/microstructures. The material properties of the Cu2O CEs were comprehensively determined using a scanning electron microscope, energy dispersive X-ray spectrometer, X-ray diffractometer, Raman spectrometer, X-ray photoelectron spectroscope, and cyclic voltameter. The Cu2O CEs sintered at various temperatures were used in DSSC devices and analyzed according to the current density–voltage characteristics, incident photon-to-current conversion efficiency, and electrochemical impedance characteristics. The Cu2O CEs sintered at 600 °C exhibited the optimal electrode properties and DSSC performance, yielding a power conversion efficiency of 3.62%. The Cu2O CEs fabricated on Cu foil were generally mechanically flexible and could therefore be applied to flexible DSSCs.

  6. Investigation of the oxygen reduction activity on silver - a rotating disc electrode study

    Energy Technology Data Exchange (ETDEWEB)

    Wiberg, G.K.H.; Mayrhofer, K.J.J.; Arenz, M. [Lehrstuhl fuer Physikalische Chemie, Technische Universitaet Muenchen, D-85748 Garching (Germany)

    2010-08-15

    In this study the oxygen reduction reaction (ORR) is investigated on a nanoparticulate silver electrocatalyst in alkaline solution. The catalytic activity of the catalyst is determined both in terms of mass activity as well as specific activity and turn over frequency, respectively. It is demonstrated that the established mass activities are independent of the applied catalyst loading, an essential requirement for a reasonable analysis. The determination of the electrochemically active surface area (ECA) or the number of electrochemically accessible sites (N{sub ECAS}), respectively, is performed by the underpotential deposition of lead. The obtained value of the activity is compared to activities of polycrystalline silver and platinum measured in the same electrolyte, as well as to literature data. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  7. Investigating Surface and Interface Phenomena in LiFeBO3 Electrodes Using Photoelectron Spectroscopy Depth Profiling

    DEFF Research Database (Denmark)

    Maibach, Julia; Younesi, Reza; Schwarzburger, Nele

    2014-01-01

    The formation of surface and interface layers at the electrodes is highly important for the performance and stability of lithium ion batteries. To unravel the surface composition of electrode materials, photoelectron spectroscopy (PES) is highly suitable as it probes chemical surface and interfac...

  8. Investigation of High-k Dielectrics and Metal Gate Electrodes for Non-volatile Memory Applications

    Science.gov (United States)

    Jayanti, Srikant

    Due to the increasing demand of non-volatile flash memories in the portable electronics, the device structures need to be scaled down drastically. However, the scalability of traditional floating gate structures beyond 20 nm NAND flash technology node is uncertain. In this regard, the use of metal gates and high-k dielectrics as the gate and interpoly dielectrics respectively, seem to be promising substitutes in order to continue the flash scaling beyond 20nm. Furthermore, research of novel memory structures to overcome the scaling challenges need to be explored. Through this work, the use of high-k dielectrics as IPDs in a memory structure has been studied. For this purpose, IPD process optimization and barrier engineering were explored to determine and improve the memory performance. Specifically, the concept of high-k / low-k barrier engineering was studied in corroboration with simulations. In addition, a novel memory structure comprising a continuous metal floating gate was investigated in combination with high-k blocking oxides. Integration of thin metal FGs and high-k dielectrics into a dual floating gate memory structure to result in both volatile and non-volatile modes of operation has been demonstrated, for plausible application in future unified memory architectures. The electrical characterization was performed on simple MIS/MIM and memory capacitors, fabricated through CMOS compatible processes. Various analytical characterization techniques were done to gain more insight into the material behavior of the layers in the device structure. In the first part of this study, interfacial engineering was investigated by exploring La2O3 as SiO2 scavenging layer. Through the silicate formation, the consumption of low-k SiO2 was controlled and resulted in a significant improvement in dielectric leakage. The performance improvement was also gauged through memory capacitors. In the second part of the study, a novel memory structure consisting of continuous metal FG

  9. Investigation of the Alkaline Electrochemical Interface and Development of Composite Metal/Metal-Oxides for Hydrogen and Oxygen Electrodes

    Science.gov (United States)

    Bates, Michael

    electrolyte. The HER kinetics of numerous binary & ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. Furthermore a model of the double layer interface is proposed, which helps explain the observed ensemble effect in the presence of AEI. In Chapter 3, Ni-Fe and Ni-Fe-Co mixed-metal-oxide (MMO) films were investigated for oxygen evolution reaction (OER) activity in 0.1M KOH on high surface area Raney-Nickel supports. During investigations of MMO activity, aniline was identified as a useful "capping agent" for synthesis of high-surface area MMO-polyaniline (PANI) composite materials. A Ni-Fe-Co/PANI-Raney-Ni catalyst was developed which exhibits enhanced mass-activity compared to state-of-the-art Ni-Fe OER electrocatalysts reported to date. The morphology of the MMO catalyst film on PANI/Raney-Ni support provides excellent dispersion of active-sites and should maintain high active-site utilization for catalyst loading on gas-diffusion electrodes. In Chapter 4, the de-activation of reversible-hydrogen electrode catalysts was investigated and the development of a Pt-Ir-Nx/C catalyst is reported, which exhibits significantly increased stability in the HBr/Br 2 electrolyte. In contrast a Pt-Ir/C catalyst exhibited increased tolerance to high-voltage cycling and in particular showed recovery of electrocatalytic activity after reversible de-activation (presumably from bromide adsorption and subsequent oxidative bromide stripping). Under the harshest testing conditions of high-voltage cycling or exposure to Br2 the Pt-based catalyst showed a trend in stability: Pt < Pt-Ir < Pt-Ir-Nx. (Abstract shortened by UMI.).

  10. Performance investigation of InAs based dual electrode tunnel FET on the analog/RF platform

    Science.gov (United States)

    Anand, Sunny; Sarin, R. K.

    2016-09-01

    In this paper for the first time, InAs based doping-less Tunnel FET is proposed and investigated. This paper also demonstrates and discusses the impact of gate stacking (SiO2 + HfO2) with equivalent oxide thickness EOT = 0.8 for analog/RF performance. The charge plasma technique is used to form source/drain region on an intrinsic InAs body by selecting proper work function of metal electrode. The paper compares different combinations of gate stacking (SiO2 and HfO2) on the basis of different analog and RF parameters such as transconductance (gm), transconductance to drive current ratio (gm/ID), output conductance (gd), intrinsic gain (AV), total gate capacitance (Cgg) and unity-gain cutoff frequency (fT). The proposed device produces an ON state current of ION ∼6 mA along with ION/IOFF ∼1012, point subthreshold slope (SS ∼ 1.9 mV/dec), average subthreshold slope (AV-SS ∼ 14.2 mV/dec) and cut-off frequency in Terahertz. The focus of this work is to eliminate the fabrication issues and providing the enhanced performance compared to doped device.

  11. Experimental Investigation of the Effects of Various Plasma Actuator Configurations on Lift and Drag Coefficients of a Circular Cylinder Including the Effects of Electrodes

    Institute of Scientific and Technical Information of China (English)

    Siavash TABATABAEIAN; Masoud MIRZAEI; Asghar SADIGHZADEH; Vahid DAMIDEH; Abdollah SHADARAM

    2012-01-01

    In this paper,the effects of the existence of plasma actuator electrodes and also various configurations of the actuator for controlling the flow field around a circular cylinder are experimentally investigated.The cylinder is made of PVC (Polyvinyl Chloride) and considered as a dielectric barrier.Two electrodes are flush-mounted on the surface of the cylinder and are connected to a DC high voltage power supply for generation of electrical discharge.Pressure distribution results show that the existence of the electrodes and also the plasma are able to change the pressure distribution around the cylinder and consequently the lift and drag coefficients.It is found that the effect of the existence of the electrodes is comparable with the effect of plasma actuator in controlling the flow field around the cylinder and this effect is not reported by other researchers.Eventually it is concluded that the existence of the electrodes or any extra objects on the cylinder and also the existence of the plasma are capable of changing the flow field structure around the cylinder so that the behavior of the lift and drag coefficients of the cylinder will be changed significantly.

  12. Preparation of CuInS{sub 2}/TiO{sub 2} nanotube heterojunction arrays electrode and investigation of its photoelectrochemical properties

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tingting [School of Environmental Science and Technology, State Key Laboratory of Fine Chemical, Key Laboratory of Industrial Ecology and Environmental Engineering of Ministry of Education, Dalian University of Technology, Dalian 116024, Liaoning (China); College of Civil Engineering and Architecture, Liaoning Technical University, Fuxin 123000 (China); Li, Xinyong, E-mail: xyli@dlut.edu.cn [School of Environmental Science and Technology, State Key Laboratory of Fine Chemical, Key Laboratory of Industrial Ecology and Environmental Engineering of Ministry of Education, Dalian University of Technology, Dalian 116024, Liaoning (China); Zhao, Qidong; Teng, Wei [School of Environmental Science and Technology, State Key Laboratory of Fine Chemical, Key Laboratory of Industrial Ecology and Environmental Engineering of Ministry of Education, Dalian University of Technology, Dalian 116024, Liaoning (China)

    2014-11-15

    Graphical abstract: Schematic illustration of the synthesis steps of CuInS{sub 2}/TiO{sub 2} heterojunction arrays electrode. - Highlights: • CuInS{sub 2}/TiO{sub 2} nanotube heterojunction arrays electrode was successfully fabricated via a modified SILAR method. • Morphology, chemical compositions and the photoelectrochemical properties were studied. • The formed heterojunction structure is demonstrated as n–n type heterojunction. - Abstract: CuInS{sub 2}/TiO{sub 2} nanotube heterojunction arrays electrode was synthesized via a modified successive ionic layer adsorption and reaction (SILAR) method. The morphology, crystalline structure and chemical composition of the composite electrode were characterized with field-emission scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS), respectively. The optical properties were investigated by UV–vis diffusion reflection spectra (DRS) and photoluminescence (PL) spectra as well as the photoelectrochemical measurements. Significantly enhanced photoelectrochemical properties of CuInS{sub 2}/TiO{sub 2} NTs electrode were observed under visible light irradiation, which could be attributed to the high absorption coefficient of CuInS{sub 2} in visible region and the heterostructure formed between CuInS{sub 2} and TiO{sub 2}.

  13. 粒子电极堆放方式对三维电极体系性能的影响研究%Investigation of the packing model of particle electrode on the efficiency of three-dimensional electrode reactor

    Institute of Scientific and Technical Information of China (English)

    钟锐超; 周德鸿; 陈卫国; 纪庆升

    2011-01-01

    通过对自制的粒子电极串进行实验,探讨了一种消除三维电极反应床中短路电流的新方法,并研究了不同粒子堆放方式对电催化效果的影响.结果表明,粒子本身长度的适当增长,使其与溶液电位差增大,废水脱色率也随之增大.采用B-β型粒子电极串在20V电压下反应60min,14mm长的粒子电极对直接湖蓝5B废水的脱色率可达到71.4%,比7mm长的粒子电极高出10%.另外,粒子电极串由于减少了短路电流,从而使废水脱色率高于常规填充床.采用B-β型粒子电极串在20V电压下反应30min,粒子电极串脱色率可达到66.9%,而使用等量的粒子电极在常规填充床中则只有45.3%的脱色率.%Based on homemade regular particle electrodes,a novel method for eliminating the short circuit current in three-dimensional reactor was proposed and the effect of the packing model of particle electrode on electrocatalysis was investigated.The results indicated that the potential difference between particle electrode and solution increased and the decolorization ratio for dye wastewater improved with the increase in the length of particle at an appropriate range.When decolorization was performed on 14 mm particle electrode in B-β packing model at 20 V for 60 min,the decolorization ratio for direst sky blue 5B wastewater was 71.4%,which was 10% higher than that on 7 mm particle electrode in B-β packing model in the same conditions.Furthermore,the decolorization ratio for wastewater was improved due to the elimination of short circuit current.The decolorization ratio reached 66.9% on particle electrode in B-β packing model at 20 V for 30 min,while only 45.3% of decolorization ratio was obtained from conventional packing reactor in the same amount.

  14. Electrochemical Investigation of Coenzyme Q10 on Silver Electrode in Ethanol Aqueous Solution and Its Determination Using Differential Pulse Voltammetry.

    Science.gov (United States)

    Li, Dan; Deng, Wei; Xu, Hu; Sun, Yinxing; Wang, Yuhong; Chen, Shouhui; Ding, Xianting

    2016-08-01

    The electrochemistry reduction of coenzyme Q10 (CoQ10) on silver electrodes has been investigated in mixed solvent containing 95 vol. % ethanol and 5 vol. % water. A combination of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) is employed to explore the mechanism of redox processes of CoQ10 in the presence and absence of oxygen, respectively. It has been proved that the redox reaction of CoQ10 is highly dependent on the oxygen in the solution compared with that of CoQ0, which may be attributed to the isoprenoid side chain effect of CoQ10 Moreover, the effects of experimental variables such as electrolyte component, pH, temperature, and sonication time on the amperometric and potentiometric responses of CoQ10 are presented. The differential pulse voltammetry method has been developed for the quantification of the CoQ10 in the complex samples. Under the optimum conditions, the method is linear over the concentration range of 1.00 × 10(-7) to 1.00 × 10(-3) mol/L (8.63 × 10(-2) to 8.63 × 10(2) mg/kg). The limit of detection (3σ/k) is 3.33 × 10(-8) mol/L (2.88 × 10(-2) mg/kg). The recoveries of the spiked samples are between 91% and 108%. The presented method can be applied to the analysis of CoQ10 in real samples without any pretreatment.

  15. Investigation of the impact of insulator material on the performance of dissimilar electrode metal-insulator-metal diodes

    Science.gov (United States)

    Alimardani, Nasir; King, Sean W.; French, Benjamin L.; Tan, Cheng; Lampert, Benjamin P.; Conley, John F.

    2014-07-01

    The performance of thin film metal-insulator-metal (MIM) diodes is investigated for a variety of large and small electron affinity insulators using ultrasmooth amorphous metal as the bottom electrode. Nb2O5, Ta2O5, ZrO2, HfO2, Al2O3, and SiO2 amorphous insulators are deposited via atomic layer deposition (ALD). Reflection electron energy loss spectroscopy (REELS) is utilized to measure the band-gap energy (EG) and energy position of intrinsic sub-gap defect states for each insulator. EG of as-deposited ALD insulators are found to be Nb2O5 = 3.8 eV, Ta2O5 = 4.4 eV, ZrO2 = 5.4 eV, HfO2 = 5.6 eV, Al2O3 = 6.4 eV, and SiO2 = 8.8 eV with uncertainty of ±0.2 eV. Current vs. voltage asymmetry, non-linearity, turn-on voltage, and dominant conduction mechanisms are compared. Al2O3 and SiO2 are found to operate based on Fowler-Nordheim tunneling. Al2O3 shows the highest asymmetry. ZrO2, Nb2O5, and Ta2O5 based diodes are found to be dominated by Frenkel-Poole emission at large biases and exhibit lower asymmetry. The electrically estimated trap energy levels for defects that dominate Frenkel-Poole conduction are found to be consistent with the energy levels of surface oxygen vacancy defects observed in REELS measurements. For HfO2, conduction is found to be a mix of trap assisted tunneling and Frenkel-Poole emission. Insulator selection criteria in regards to MIM diodes applications are discussed.

  16. Cyclic voltammetric investigations of microstructured and platinum-covered glassy carbon electrodes in contact with a polymer electrolyte membrane

    Energy Technology Data Exchange (ETDEWEB)

    Scherer, G.G.; Veziridis, Z.; Staub, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Freimuth, H. [Inst. fuer Mikrotechnik Mainz IMM, Mainz (Germany)

    1997-06-01

    Model gas diffusion electrodes were prepared by microstructuring glassy carbon surfaces with high aspect ratios and subsequent deposition of platinum. These electrodes were characterized by hydrogen under-potential deposition (H-upd) in contact with a polymer electrolyte membrane employing cyclic voltametry. H-upd was found on platinum areas not in direct contact to the solid electrolyte, as long as a continuous platinum-path existed. A carbon surface between platinum acts as barrier for H-upd. (author) 4 figs., 5 refs.

  17. Attaining 2D Black Phosphorus and Investigations into Floating-Electrode Dielectric Barrier Discharge Treatment of Solutions

    Science.gov (United States)

    Smith, Joshua Benjamin

    -ray diffraction, transmission electron microscopy, and Raman spectroscopy have confirmed successful growth of 2D black phosphorus from red phosphorus thin films for potential uses in 2D semiconductor applications. Additionally, this work discusses some of the chemistry occurring in solution as a result of nonthermal plasma treatment from a floating-electrode dielectric barrier discharge (FE-DBD) configuration. Nonthermal plasma generation allows for the treatment of heat sensitive materials. This has opened up the field to numerous clinical applications of nonthermal plasma treatment including sterilization and wound healing along with potentials in dentistry, dermatology, and even food industries. FE-DBD plasma treatment of water was found to provide a wide-range antimicrobial solution that remained active following 2 years of aging. This plasma-treated water was found to generate a number of ROS/RNS and the formation of these components was studied and verified with UV/Vis and ESR spectroscopy. Enhanced effects were observed when cell culture medium was plasma treated, suggesting the formation of additional reactive species from the plasma treatment of a variety of biomolecules. It is essential to understand these effects for a number of reasons. The possibility to generate a wide range of antimicrobial solutions from air, water, and basic biomolecules could provide a solution for those bacteria that have developed antibiotic resistances. Simultaneously, information into the reaction mechanisms of this FE-DBD plasma treatment can be investigated. All of the applications mentioned above involve complex networks of basic biomolecules, from skin tissue to bacteria cell walls. This work analyzes the effects of plasma treatment on several biomolecule solutions and simultaneously takes aim at understanding some of the potential mechanisms of plasma treatment. Studies were carried out using NMR and GC/MS. This information was used to investigate the possible targeted areas for FE

  18. Development of Carbon Based optically Transparent Electrodes from Pyrolyzed Photoresist for the Investigation of Phenomena at Electrified Carbon-Solution Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Donner, Sebastian [Iowa State Univ., Ames, IA (United States)

    2007-01-01

    The work presented herein describes a fundamental investigations of carbon as electrode material by using the pyrolysis of photoresist to create an optically transparent material. The development of these carbon-based optically transparent electrodes (C-OTEs) enables investigations of molecular interactions within the electrical double layer, processes that are central to a wide range of important phenomena, including the impact of changes in the surface charge density on adsorption. The electrochemical importance of carbon cannot be understated, having relevance to separations and detection by providing a wide potential window and low background current in addition to being low cost and light weight. The interactions that govern the processes at the carbon electrode surface has been studied extensively. A variety of publications from the laboratories of McCreery and Kinoshita provide in depth summaries about carbon and its many applications in electrochemistry. These studies reveal that defects, impurities, oxidation, and a variety of functional groups create adsorption sites on carbon surfaces with different characteristics. The interest in C-OTEs was sparked by the desire to study and understand the behavior of individual molecules at electrified interfaces. It draws on the earlier development of Electrochemically Modulated Liquid Chromatography (EMLC), which uses carbon as the stationary phase. EMLC takes advantage of changing the applied potential to the carbon electrode to influence the retention behavior of analytes. However, perspectives gained from, for example, chromatographic measurements reflect the integrated response of a large ensemble of potentially diverse interactions between the adsorbates and the carbon electrode. Considering the chemically and physically heterogeneous surface of electrode materials such as glassy carbon, the integrated response provides little insight into the interactions at a single molecule level. To investigate individual

  19. Fabrication of Carbon-Platinum Interdigitated Array Electrodes and Their Application for Investigating Homogeneous Hydrogen Evolution Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fei; Divan, Ralu; Parkinson, Bruce A.

    2015-06-29

    Carbon interdigitated array (IDA) electrodes have been applied to study the homogeneous hydrogen evolution electrocatalyst [Ni(PPh2NBn2)2]2+ (where PPh2NBn2 is 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane). The existence of reaction intermediates in the catalytic cycle is inferred from the electrochemical behavior of a glassy carbon disk electrodes and carbon IDA electrodes. The currents on IDA electrodes for an EC’ (electron transfer reaction followed by a catalytic reaction) mechanism are derived from the number of redox cycles and the contribution of non-catalytic currents. The catalytic reaction rate constant was then extracted from the IDA current equations. Applying the IDA current and kinetic equations to the electrochemical response of the [Ni(PPh2NBn2)2]2+ catalyst yielded a rate constant of 0.10 s-1 for the hydrogen evolution reaction that agrees with the literature value. The quantitative analysis of IDA cyclic voltammetry can be used as a simple and straightforward method for determining rate constants in other catalytic systems. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for DOE. Use of the Center for Nanoscale Materials was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

  20. Investigation of in-situ electrode formation with respect to potential applications in intermediate temperature solid oxide fuel cells

    OpenAIRE

    Fang, Qingping

    2007-01-01

    The novel SEA (Single Element Arrangement) concept for SOFC consists of a single material to complete the whole galvanic cell. Essential of the SEA concept is the in-situ electrode formation. Such kind of material becomes mixed ionic and electronic conducting in the surface region, while still being predominantly ionically conducting inside under the working conditions. Electronic short circuit will be blocked by the region where ionic conduction is dominant, allowing the generation of electr...

  1. Role of iron oxide impurities in electrocatalysis by multiwall carbon nanotubes: An investigation using a novel magnetically modified ITO electrodes

    Indian Academy of Sciences (India)

    Kanchan M Samant; Vrushali S Joshi; Kashinath R Patil; Santosh K Haram

    2014-04-01

    The role of iron oxide impurities in the electrocatalytic properties of multiwall carbon nanotubes (MWCNTs) prepared by catalytic chemical vapour decomposition method (CCVD) is studied in detail. A novel magnetically modified electrodes have been developed by which MWCNTs were immobilized on indium-tin oxide (ITO) electrodes, without any chemical binders. The electro-catalytic oxidation of dopamine, and reduction of hydrogen peroxide have been studied by cyclic voltammetry on magnetically modified electrodes with (i) MWCNTs with occluded iron oxide impurities (Fe-MWCNTs), (ii) MWCNTs grown on iron oxide nanoparticle particulate films (Io-MWCNTs) and (iii) pristine iron oxide nanoparticle particulate film (Io-NPs). A shift towards less positive potentials for the oxidation of dopamine was observed which is in the order of Fe-MWCNTs < Io-MWCNTs < Io-NPs. Similarly, trend towards less negative potentials for the reduction of hydrogen peroxide was observed. Thus, the electrocatalytic activities displayed by MWCNTs have been attributed to the iron oxide impurities associated with it. The systematic variation was related to the nature of interaction of iron oxide nanoparticles with MWCNT surface.

  2. Magnetohydrodynamic electrode

    Science.gov (United States)

    Boquist, Carl W.; Marchant, David D.

    1978-01-01

    A ceramic-metal composite suitable for use in a high-temperature environment consists of a refractory ceramic matrix containing 10 to 50 volume percent of a continuous high-temperature metal reinforcement. In a specific application of the composite, as an electrode in a magnetohydrodynamic generator, the one surface of the electrode which contacts the MHD fluid may have a layer of varying thickness of nonreinforced refractory ceramic for electrode temperature control. The side walls of the electrode may be coated with a refractory ceramic insulator. Also described is an electrode-insulator system for a MHD channel.

  3. Graphite electrode thermal behavior and solid electrolyte interphase investigations: Role of state-of-the-art binders, carbonate additives and lithium bis(fluorosulfonyl)imide salt

    Science.gov (United States)

    Forestier, Coralie; Grugeon, Sylvie; Davoisne, Carine; Lecocq, Amandine; Marlair, Guy; Armand, Michel; Sannier, Lucas; Laruelle, Stephane

    2016-10-01

    The risk of thermal runaway is, for Li-ion batteries, a critical issue for large-scale applications. This results in manufacturers and researchers placing great emphasis on minimizing the heat generation and thereby mitigating safety-related risks through the search for suitable materials or additives. To this end, an in-depth stepwise investigation has been undertaken to provide a better understanding of the exothermic processes that take place at the negative electrode/electrolyte interface as well as an increased visibility of the role of the state-of-the-art electrode binders, additives and lithium salt by means of the classical DSC technique. A reliable experimental set up helped quantify the beneficial or harmful contribution of binder polymers to the exothermic behavior of the CMC/SBR containing graphite electrode film in contact with 1 M LiPF6 in EC:DMC:EMC (1:1:1 v/v/v) electrolyte. Further, the role of the VC, FEC and VEC electrolyte additives (2 wt%) in reinforcing the protective SEI layer towards thermally induced electrolyte reduction is discussed in the light of infrared spectroscopy and transmission electron microscopy analyzes results. Moreover, after a preliminary corrosion study of LiPF6/LiFSI mixtures, we showed that the 0.66/0.33 M composition can be used in commercial NMC-based LiBs with a positive effect on the thermal runaway.

  4. Long Term Stability Investigation of Solid Oxide Electrolysis Cell with Infiltrated Porous YSZ Air Electrode Under High Current

    DEFF Research Database (Denmark)

    Veltzé, Sune; Ovtar, Simona; Simonsen, Søren Bredmose

    2015-01-01

    activity, due to high surface area of catalyst nano particles. Advantage of infiltration is also separate production of electrolyte backbone structure with good ionic connectivity and mechanical properties. With this study we present the results of a solid oxide cell with infiltrated porous yttria...... and the backbone, and perovskite catalyst material. Cobalt doped lanthanum nickelate was used as the perovskite catalyst due to its excellent performance. The cell was tested in steam electrolysis for at least 2000h. This initial test indicate that a stable air electrode was formed, and that the cell performance...

  5. Investigation And Optimization Of EDM Process Of AISI 4140 Alloy Steel Using Various Tool Electrodes: A Review Paper

    Directory of Open Access Journals (Sweden)

    Kishor Lal ,

    2014-11-01

    Full Text Available The purpose of this research work is to determine the optimized settings of key machining factors like pulse on time, discharge current and duty cycle for AISI 4140 alloy steel using various tool electrodes. The output responses will be measured are material removal rate (MRR,surface roughness(SR and tool wear rate(TWR. Mathematical models are proposed for the above are L27 orthogonal array. The micro structural changes in the work piece after machining process will also be examined by the use of SEM.

  6. Investigation and improvement of a novel double-working-electrode electrochemical system for organic matter treatment from high-salinity wastewater.

    Science.gov (United States)

    Yu, Han; Zhao, Min; Zhang, Linus; Dong, Heng; Yu, Hongbing; Chen, Ze

    2017-02-03

    The novel double-working-electrode electrochemical system with air diffusion cathode (ADC) and Ti/SnO2-Sb anode (TSSA) has shown higher efficiency and lower energy consumption for the degradation of organic pollutant from high-salinity wastewater, compared to the traditional single anode system. To further investigate and improve this system, in this work, firstly the effect of vital factors of the double-working-electrode electrochemical system including initial methyl orange (MO) concentration, NaCl concentration and initial pH value of organic solution were investigated, using MO as the targeted organic pollutant, carbon black ADC (CBAC) as cathode and stainless steel mesh electrode (SSME) as control. Besides, for the further improvement of removal performance, a novel home-made activated carbon-ADC (ACAC) was studied as cathode with the same investigation process. The results showed that, in the experiments studying the effect of both initial MO and NaCl concentrations, the removal performance was in the order of TSSA-ACAC > TSSA-CBAC > TSSA-SSME in all conditions of initial MO and NaCl concentrations. However, with the pH value reduced from 6.0 to 3.0, the performances of three systems turned to be much closer to each other. Besides, ACAC played a synergistic role in MO removal by greatly improving the MO removal performance and enhancing its adaptability to the reactor parametric variation. ACAC created a weak acidic environment for accelerating the indirect electro-oxidation of MO on TSSA. The MO degradation pathways in the three systems were the same but the TSSA-ACAC system gave a higher degradation kinetics order.

  7. Nanoparticle-electrode collision processes: Investigating the contact time required for the diffusion-controlled monolayer underpotential deposition on impacting nanoparticles

    Science.gov (United States)

    Cutress, Ian J.; Rees, Neil V.; Zhou, Yi-Ge; Compton, Richard G.

    2011-09-01

    Recent work on faradaic processes occurring during thermal nanoparticle-electrode collisions contrasts significantly from analogous research using ultrasonically-driven microparticles, where no faradaic signals were found. It is suggested that this might be explained by the differences in both particle size and contact time. To investigate this, we present results from adapted Monte Carlo random walk simulations. Using the underpotential deposition of thallium onto silver nanoparticles as a model system, it is found that an estimated minimum contact time of ca. 10-4 s is required to deposit a complete monolayer (from a 10 mM solution) onto a nanoparticle of radius 45 nm.

  8. Vanadium Oxide Electrochemical Capacitors: An Investigation into Aqueous Capacitive Degradation, Alternate Electrolyte-Solvent Systems, Whole Cell Performance and Graphene Oxide Composite Electrodes

    Science.gov (United States)

    Engstrom, Allison Michelle

    Vanadium oxide has emerged as a potential electrochemical capacitor material due to its attractive pseudocapacitive performance; however, it is known to suffer from capacitive degradation upon sustained cycling. In this work, the electrochemical cycling behavior of anodically electrodeposited vanadium oxide films with various surface treatments in aqueous solutions is investigated at different pH. Quantitative compositional analysis and morphological studies provide additional insight into the mechanism responsible for capacitive degradation. Furthermore, the capacitance and impedance behavior of vanadium oxide electrochemical capacitor electrodes is compared for both aqueous and nonaqueous electrolyte-solvent systems. Alkali metal chloride and bromide electrolytes were studied in aqueous systems, and nonaqueous systems containing alkali metal bromides were studied in polar aprotic propylene carbonate (PC) or dimethyl sulfoxide (DMSO) solvents. The preferred aqueous and nonaqueous systems identified in the half-cell studies were utilized in symmetric vanadium oxide whole-cells. An aqueous system utilizing a 3.0 M NaCl electrolyte at pH 3.0 exhibited an excellent 96% capacitance retention over 3000 cycles at 10 mV s-1. An equivalent system tested at 500 mV s-1 displayed an increase in capacitance over the first several thousands of cycles, and eventually stabilized over 50,000 cycles. Electrodes cycled in nonaqueous 1.0 M LiBr in PC exhibited mostly non-capacitive charge-storage, and electrodes cycled in LiBr-DMSO exhibited a gradual capacitive decay over 10,000 cycles at 500 mV s-1. Morphological and compositional analyses, as well as electrochemical impedance modeling, provide additional insight into the cause of the cycing behavior. Lastly, reduced graphene oxide and vanadium oxide nanowire composites have been successfully synthesized using electrophoretic deposition for electrochemical capacitor electrodes. The composite material was found to perform with a

  9. Investigation of low-voltage pulse parameters on electroporation and electrical lysis using a microfluidic device with interdigitated electrodes.

    Science.gov (United States)

    Morshed, Bashir I; Shams, Maitham; Mussivand, Tofy

    2014-03-01

    Electroporation (EP) of biological cells leads to the exchange of materials through the permeabilized cell membrane, while electrical lysis (EL) irreversibly disrupts the cell membrane. We report a microfluidic device to study these two phenomena with low-voltage excitation for lab-on-a-chip (LOC) applications. For systematic study of EP, we have employed a quantification metric: flow Index (FI) of EP. Simulation and experimental results with the microfluidic device containing interdigitated, coplanar, integrated electrodes to electroporate, and rapidly lyse biological cells are presented. H&E stained human buccal cells were subjected to various pulse magnitudes, pulsewidths, and number of pulses. Simulations show that an electric field of 25 kV/cm with a 20 V applied potential produced 1.3 (°)C temperature rise for a 5 s of excitation. For a 20 V pulse-excitation with pulse-widths between 0.5 to 5 s, EL was observed, whereas for lower excitations, only EP was observed. FI of EP is found to be a direct function of pulse magnitudes, pulsewidths, and numbers of pulses. To release DNA from nucleus, excitation-pulses of 5 s were required. Quantification of EP would be useful for systematic study of EP toward optimization with various excitation pulses, while low-voltage requirement and high yield of EP and EL are critical to develop LOC for drug delivery and cell-sample preparation, respectively.

  10. Investigation of Surface Roughness and Material Removal Rate (MRR on Tool Steel Using Brass and Copper Electrode for Electrical Discharge Grinding (EDG Process

    Directory of Open Access Journals (Sweden)

    M. Hafiz Helmi

    2009-09-01

    Full Text Available This paper presents the investigation on surface roughness and material removal rate (MRR of tool steel machined with brass and copper electrode for Electrical Discharge Grinding (EDG process. The machining parameter include pulse ON time, pulse OFF time, peak current and capacitance. Analysis of variance (ANOVA with Taguchi method is used to investigate the significant effect on the performance characteristic and the optimal cutting parameters of EDG. The result shows that, the surface roughness value when using of both tool materials are mostly influenced by pulse ON time and peak current. The capacitance parameter in both experiments was not giving any significant effect. The significant factors for the material removal rate due to the machining parameter are peak current parameter and ON time parameter but it also can increase the machining time

  11. Investigation of Cu(II) Binding to Bovine Serum Albumin by Potentiometry with an Ion Selective Electrode

    Science.gov (United States)

    Jie Liu

    2004-01-01

    A laboratory project that investigates Cu(II) bind to bovine serum albumin (BSA) in an aqueous solution is developed to assist undergraduate students in gaining better understanding of the interaction of ligands with biological macromolecule. Thus, students are introduced to investigation of Cu(II) binding to BSA by potentiometry with the Cu(II)…

  12. Investigation Of Li{sub X}CoO{sub 2} Li- Intercalation Electrodes Using X-Ray Absorption Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Haas, O.; Holzapfel, M.; Yang, X.Q. [BNL Lab (United States); Yoon, W.-S. [BNL Lab (United States); Chung, K.-Y. [BNL Lab (United States)

    2005-03-01

    Li{sub X}CoO{sub 2} was investigated with X-ray absorption spectroscopy using hard and soft X-rays and compared with some results obtained in previous investigations of La{sub (1-x)}-Ca{sub x}CoO{sub 3}, which has a similar electron configuration. (author)

  13. An Investigation of Glutathione-Platinum(II Interactions by Means of the Flow Injection Analysis Using Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Rene Kizek

    2007-07-01

    Full Text Available Despite very intensive research in the synthesising of new cytostatics, cisplatin isstill one of the most commonly used anticancer drugs. Therefore, an investigation ofinteractions of cisplatin with different biologically important amino acids, peptides andproteins is very topical. In the present paper, we utilized flow injection analysis coupledwith electrochemical detection to study and characterize the behaviour of various forms ofglutathione (reduced glutathione – GSH, oxidized glutathione – GSSG and S-nitrosoglutathione – GSNO. The optimized conditions were as follows: mobile phase consistedof acetate buffer (pH 3 with a flow rate of 1 mL min-1. Based on results obtained we chose850 mV as the optimal potential for detection of GSH and 1,100 mV as the optimalpotential for detection of GSSG and GSNO. The detection limits of GSH, GSSG andGSNO were 100 pg mL-1, 50 ng mL-1 and 300 pg mL-1, respectively. Further, the optimized technique was used for investigation of interactions between cisplatin and GSH. We were able to observe the interaction between GSH and cisplatin via decrease in the signal corresponding to glutathione. Moreover, we evaluated the formation of the complex by spectrometry. The spectrometric results obtained were in good agreement with electrochemical ones.

  14. Preparation and investigation of nano-thick FTO/Ag/FTO multilayer transparent electrodes with high figure of merit.

    Science.gov (United States)

    Yu, Shihui; Li, Lingxia; Lyu, Xiaosong; Zhang, Weifeng

    2016-01-01

    In order to improve the conductivity of the single-layered nano-thick F doped SnO2 (FTO) thin films, an Ag mid-layer is embedded between the FTO layers. In our work, the effects of mid-layer Ag and top FTO layer on the structural, electrical and optical properties of FTO/Ag/FTO multilayered composite structures deposited on quartz glass substrates by magnetron sputtering at 100 °C have been investigated. As the thickness of Ag mid-layer increases, the resistivity decreases. As the top FTO layer thickness increases, the resistivity increases. The highest value of figure of merit φTC is 7.8 × 10(-2 ) Ω(-1) for the FTO (20 nm)/Ag (7 nm)/FTO (30 nm) multilayers, while the average optical transmittance is 95.5% in the visible range of wavelengths and the resistivity is 8.8 × 10(-5 ) Ω·cm. In addition, we also describe the influence of Ag and top FTO layer thickness on structural, electrical and optical properties of the nano-thick FTO (20 nm)/Ag/FTO multilayers and the mechanism of the changes of electrical and optical properties at different Ag and top FTO layer thicknesses.

  15. Multi-Electrode Resistivity Probe for Investigation of Local Temperature Inside Metal Shell Battery Cells via Resistivity: Experiments and Evaluation of Electrical Resistance Tomography

    Directory of Open Access Journals (Sweden)

    Xiaobin Hong

    2015-01-01

    Full Text Available Direct Current (DC electrical resistivity is a material property that is sensitive to temperature changes. In this paper, the relationship between resistivity and local temperature inside steel shell battery cells (two commercial 10 Ah and 4.5 Ah lithium-ion cells is innovatively studied by Electrical Resistance Tomography (ERT. The Schlumberger configuration in ERT is applied to divide the cell body into several blocks distributed in different levels, where the apparent resistivities are measured by multi-electrode surface probes. The investigated temperature ranges from −20 to 80 °C. Experimental results have shown that the resistivities mainly depend on temperature changes in each block of the two cells used and the function of the resistivity and temperature can be fitted to the ERT-measurement results in the logistical-plot. Subsequently, the dependence of resistivity on the state of charge (SOC is investigated, and the SOC range of 70%–100% has a remarkable impact on the resistivity at low temperatures. The proposed approach under a thermal cool down regime is demonstrated to monitor the local transient temperature.

  16. Microvoltammetric Electrodes.

    Science.gov (United States)

    1985-09-25

    Microvoltammetric Electrodes, J. 0. Howell, R. M. Wightman, Anal. Chem., 56, 524-529 (1984). 2. Flow Rate Independent Amperometric Cell , W. L. Caudill...Electroanal. Chem., 182, 113-122 (1985). C. List of all publications 1. Flow Rate Independent Amperometric Cell , W. L. Caudill, J. 0. Howell, R. M

  17. Robust high temperature oxygen sensor electrodes

    DEFF Research Database (Denmark)

    Lund, Anders

    Platinum is the most widely used material in high temperature oxygen sensor electrodes. However, platinum is expensive and the platinum electrode may, under certain conditions, suffer from poisoning, which is detrimental for an oxygen sensor. The objective of this thesis is to evaluate electrode ......-based electrodes and one porous electrode based on the perovskite-structured strontium and vanadiumdoped lanthanum chromium oxide (LSCV) were investigated. The porous electrodes were applied on yttrium-stabilised zirconium oxide (YSZ) substrates in a collaboration with the company PBI...

  18. The influence of membrane electrode assembly water content on the performance of a polymer electrolyte membrane fuel cell as investigated by 1H NMR microscopy.

    Science.gov (United States)

    Feindel, Kirk W; Bergens, Steven H; Wasylishen, Roderick E

    2007-04-21

    The relation between the performance of a self-humidifying H(2)/O(2) polymer electrolyte membrane fuel cell and the amount and distribution of water as observed using (1)H NMR microscopy was investigated. The integrated (1)H NMR image signal intensity (proportional to water content) from the region of the polymer electrolyte membrane between the catalyst layers was found to correlate well with the power output of the fuel cell. Several examples are provided which demonstrate the sensitivity of the (1)H NMR image intensity to the operating conditions of the fuel cell. Changes in the O(2)(g) flow rate cause predictable trends in both the power density and the image intensity. Higher power densities, achieved by decreasing the resistance of the external circuit, were found to increase the water in the PEM. An observed plateau of both the power density and the integrated (1)H NMR image signal intensity from the membrane electrode assembly and subsequent decline of the power density is postulated to result from the accumulation of H(2)O(l) in the gas diffusion layer and cathode flow field. The potential of using (1)H NMR microscopy to obtain the absolute water content of the polymer electrolyte membrane is discussed and several recommendations for future research are provided.

  19. Functionalization of gold and graphene electrodes by p-maleimido-phenyl towards thiol-sensing systems investigated by EQCM and IR ellipsometric spectroscopy

    Science.gov (United States)

    Neubert, Tilmann Joachim; Rösicke, Felix; Sun, Guoguang; Janietz, Silvia; Gluba, Marc A.; Hinrichs, Karsten; Nickel, Norbert H.; Rappich, Jörg

    2017-01-01

    Electrografting of gold and graphene surfaces by functional p-(N-maleimido)phenyl groups was performed by reduction of p-(N-maleimido)phenyldiazonium tetrafluoroborate. The reduction was carried out using cyclo voltammetry coupled with micro-gravimetric measurements by means of electrochemical quartz crystal microbalance (EQCM). The overall deposited mass on gold was higher than on graphene. However, the Faradaic efficiency was lower on Au (14%) compared to graphene (22%) after the first potential scan. Subsequently, the maleimide functional groups have been tested for immobilization of terminal thiols using 2-(4-nitrobenzene)-ethane-thiol for the functionalized graphene surface and a cysteine-modified peptide for the functionalized gold surface. The functionalization by p-(N-maleimido)phenyl groups and the following thiol coupling of the particular surface was proven by infrared spectroscopic ellipsometry (IRSE). In addition, the interaction of the tetrabutylammonium and tetrafluoroborate ions present in the electrolyte with the Au and graphene electrodes was investigated by EQCM and revealed less electrostatic interaction of graphene with these ions in solution compared to the metal (Au) surface.

  20. An ionization chamber with magnetic levitated electrodes

    CERN Document Server

    Kawaguchi, T

    1999-01-01

    A new type of ionization chamber which has magnetically levitated electrodes has been developed. The electrodes are supplied voltages for the repelling of ions by a battery which is also levitated with the electrodes. The characteristics of this ionization chamber are investigated in this paper.

  1. Electrochemical and impedance investigation of the effect of lithium malonate on the performance of natural graphite electrodes in lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xiao-Guang; Dai, Sheng [Chemical Sciences Division, Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge, TN 37831 (United States)

    2010-07-01

    Lithium malonate (LM) was coated on the surface of a natural graphite (NG) electrode, which was then tested as the negative electrode in the electrolytes of 0.9 M LiPF{sub 6}/EC-PC-DMC (1/1/3, w/w/w) and 1.0 M LiBF{sub 4}/EC-PC-DMC (1/1/3, w/w/w) under a current density of 0.075 mA cm{sup -2}. LM was also used as an additive to the electrolyte of 1.0 M LiPF{sub 6}/EC-DMC-DEC (1/1/1, v/v/v) and tested on a bare graphite electrode. It was found that both the surface coating and the additive approach were effective in improving first charge-discharge capacity and coulomb efficiency. Electrochemical impedance spectra showed that the decreased interfacial impedance was coupled with improved coulomb efficiency of the cells using coated graphite electrodes. Cyclic voltammograms (CVs) on fresh bare and coated natural graphite electrodes confirmed that all the improvement in the half-cell performance was due to the suppression of the solvent decomposition through the surface modification with LM. The CV data also showed that the carbonate electrolyte with LM as the additive was not stable against oxidation, which resulted in lower capacity of the full cell with commercial graphite and LiCoO{sub 2} electrodes. (author)

  2. Electrochemical and impedance investigation of the effect of lithium malonate on the performance of natural graphite electrodes in lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xiao-Guang [ORNL; Dai, Sheng [ORNL

    2010-01-01

    Lithium malonate (LM) was coated on the surface of a natural graphite (NG) electrode, which was then tested as the negative electrode in the electrolytes of 0.9 M LiPF6/EC-PC-DMC (1/1/3, by weight) and 1.0 M LiBF4/EC-PC-DMC (1/1/3, by weight) under a current density of 0.075 mA cm-2. LM was also used as an additive to the electrolyte of 1.0 M LiPF6/EC-DMC-DEC (1/1/1, by volume) and tested on a bare graphite electrode. It was found that both the surface coating and the additive approach were effective in improving first charge discharge capacity and coulomb efficiency. Electrochemical impedance spectra showed that the decreased interfacial impedance was coupled with improved coulomb efficiency of the cells using coated graphite electrodes. Cyclic voltammograms (CVs) on fresh bare and coated natural graphite electrodes confirmed that all the improvement in the half-cell performance was due to the suppression of the solvent decomposition through the surface modification with LM. The CV data also showed that the carbonate electrolyte with LM as the additive was not stable against oxidation, which resulted in lower capacity of the full cell with commercial graphite and LiCoO2 electrodes.

  3. Electroreduction of cefetamet on mercury platinum and gold electrodes

    Directory of Open Access Journals (Sweden)

    P. ZUMAN

    2000-01-01

    Full Text Available The electroreduction of cefetamet (CEF using gold and platinum electrodes has been investigated in slightly alkaline medium (pH 8.40 where adsorption, previously observed at mercury electrode, was pronounced. This investigation was performed in order to determine whether the adsorption interfers with the reduction process even at solid electrodes and to compare with a mercury electrode.

  4. Imaging and manipulation of a polar molecule oil Ag(111)

    DEFF Research Database (Denmark)

    Lin, Rong; Braun, K.F.; Tang, H.;

    2001-01-01

    on the surface. Accompanying with the reposition, molecular rotation and/or changing of binding configurations can also be induced. It is found that the dipole moment of the molecule has minor effects on its lateral movement. The results demonstrate that due to many degrees of freedom for large molecules...

  5. Impedance spectroscopic investigation of the effect of thin azo-calix[4]arene film type on the cation sensitivity of the gold electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Mlika, R., E-mail: mlikarym@yahoo.fr [Laboratoire de Physique et Chimie des Interfaces (LPCI), Faculte des Sciences de Monastir, Avenue de l' environnement, 5000 Monastir (Tunisia); Rouis, A. [Laboratoire de Physique et Chimie des Interfaces (LPCI), Faculte des Sciences de Monastir, Avenue de l' environnement, 5000 Monastir (Tunisia); Bonnamour, I. [Universite de Lyon, Institut de Chimie et Biochimie Moleculaires et Supramoleculaires, Universite Claude Bernar, Lyon 1, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne (France); Ouada, H. Ben [Laboratoire de Physique et Chimie des Interfaces (LPCI), Faculte des Sciences de Monastir, Avenue de l' environnement, 5000 Monastir (Tunisia)

    2011-10-10

    In this work, we report the impedance spectroscopic investigation of the effect of the thin film type on the selectivity of gold/azo-calix[4]arene electrodes. For this purpose, two C1 and C3 azo-calix[4]arene derivative molecules, used as thin films, are deposited by spin-coating process on the gold surface. These thin films were first studied using contact angle measurements. This revealed a less hydrophobic character for C3 thin film, which has been attributed to the presence of hydroxyl groups at the lower rim. The sensitivity study, by Electrochemical Impedance Spectroscopy (EIS), towards Cu{sup 2+} and Eu{sup 3+} cations, has showed that the C3 thin film is more sensitive and selective towards Eu{sup 3+} than C1. This best performance is due to the presence of two ester groups acting as clips and leading to more complexation stability. The EIS results were modeled by an appropriate equivalent circuit for the aim of elucidating electrical properties of thin films. This modeling has exposed that C3 thin film presents lower ionic conductivity and limited diffusion phenomenon at the interface. Highlights: {yields} C1 and C3 azo-calix[4]arenes thin films are deposited on the gold surface. {yields} The lower hydrophobicity for C3 was attributed to the presence of hydroxyl groups. {yields} The C3 thin film is more sensitive and selective towards Eu{sup 3+} than C1 one. {yields} This best performance is due to the presence of two ester groups acting as clips.

  6. Investigation of particle inertial migration in high particle concentration suspension flow by multi-electrodes sensing and Eulerian-Lagrangian simulation in a square microchannel.

    Science.gov (United States)

    Zhao, Tong; Yao, Jiafeng; Liu, Kai; Takei, Masahiro

    2016-03-01

    The inertial migration of neutrally buoyant spherical particles in high particle concentration (αpi  > 3%) suspension flow in a square microchannel was investigated by means of the multi-electrodes sensing method which broke through the limitation of conventional optical measurement techniques in the high particle concentration suspensions due to interference from the large particle numbers. Based on the measured particle concentrations near the wall and at the corner of the square microchannel, particle cross-sectional migration ratios are calculated to quantitatively estimate the migration degree. As a result, particle migration to four stable equilibrium positions near the centre of each face of the square microchannel is found only in the cases of low initial particle concentration up to 5.0 v/v%, while the migration phenomenon becomes partial as the initial particle concentration achieves 10.0 v/v% and disappears in the cases of the initial particle concentration αpi  ≥ 15%. In order to clarify the influential mechanism of particle-particle interaction on particle migration, an Eulerian-Lagrangian numerical model was proposed by employing the Lennard-Jones potential as the inter-particle potential, while the inertial lift coefficient is calculated by a pre-processed semi-analytical simulation. Moreover, based on the experimental and simulation results, a dimensionless number named migration index was proposed to evaluate the influence of the initial particle concentration on the particle migration phenomenon. The migration index less than 0.1 is found to denote obvious particle inertial migration, while a larger migration index denotes the absence of it. This index is helpful for estimation of the maximum initial particle concentration for the design of inertial microfluidic devices.

  7. Optical second harmonic generation measurements for investigating electron injection into a pentacene field effect transistor with Au source and drain electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Eunju; Manaka, Takaaki; Tamura, Ryosuke [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo 152-8552 (Japan); Iwamoto, Mitsumasa [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo 152-8552 (Japan)], E-mail: iwamoto@pe.titech.ac.jp

    2008-03-03

    The pentacene field effect transistors (FETs)' operation for the injection carrier was revealed by means of the drain current-elapsed time (I{sub ds}-t) and optical second harmonic generation (SHG) measurements. The charge carriers forming the conducting channel of pentacene FETs were mainly holes injected from the Au source electrode. Carrier injection from source and drain electrodes was followed by the carrier trapping, and the SHG signal modulated by the change in the electric field distribution between Au the source and drain electrodes was shown. In particular, at the off state of the FET, electron injection and succeeding trapping were suggested. Furthermore, hole injection assisted by trapped electrons was also suggested.

  8. An investigation of rod electrode wear in micro-EDM%微细电火花加工圆柱电极的损耗研究

    Institute of Scientific and Technical Information of China (English)

    王元刚; 王虎; 吴蒙华; 李晓鹏; 刘宇

    2013-01-01

    应用电磁场理论对微细电火花加工(Micro Electrical Discharge Machining,Micro-EDM)损耗机理进行分析,建立了加工中工具电极电场分布的数学模型.应用Comsol Multiphysics软件对此模型进行了计算与模拟,分析了电场强度的变化对电极形状变化的影响,并指出在靠近放电点位置和底部电极形状改变后,集肤效应的作用被削弱.实验验证了仿真结果和所提出损耗机理的正确性,为电极损耗补偿策略和加工精度的提高提供了理论依据.%The mechanism of micro Electrical Discharge Machining (micro-EDM) electrode wear was discussed based on electromagnetic theory,and a mathematical model of electrode wear is established. This model is solved by Comsol Multiphysics. The shape of electrode is changing with electrode field in micro-EDM. Skin effect effects current density, but it is not serious in the proximity of discharge point. These results were verified by experiment. They provide theoretical basis for improving the precision.

  9. Ion Recognition and Analytical Application of a Fibroin Modified Electrode

    Institute of Scientific and Technical Information of China (English)

    Qiong CHENG; Tu Zhi PENG; Xiao Bo HU; Catherine F.YANG

    2004-01-01

    A novel fibroin modified electrode with ion recognition was reported. The membrane with isoelectric point of pH 4.5, was modified on graphite and carbon fiber electrodes. The pH-responsive ion recognition of the modified electrode was investigated by use of some neurocompounds. The fibroin carbon fiber electrode has been used for in-vivo determination.

  10. The electrical characterization and response to hydrogen of Schottky diodes with a resistive metal electrode-rectifying an oversight in Schottky diode investigation

    Energy Technology Data Exchange (ETDEWEB)

    Dawson, P; Feng, L; Penate-Quesada, L [Centre for Nanostructured Media, School of Maths and Physics, Queen' s University of Belfast, Belfast BT7 1NN (United Kingdom); Hill, G [EPSRC National Centre for III-V Technologies, Mappin Street, University ofSheffield, Sheffield S1 3JD (United Kingdom); Mitra, J, E-mail: P.dawson@qub.ac.uk

    2011-03-30

    Schottky-barrier structures with a resistive metal electrode are examined using the 4-point probe method where the probes are connected to the metal electrode only. The observation of a significant decrease in resistance with increasing temperature (over a range of {approx}100 K) in the diode resistance-temperature (R{sub D}-T) characteristic is considered due to charge carrier confinement to the metal electrode at low temperature (high resistance), with the semiconductor progressively opening up as a parallel current carrying channel (low resistance) with increasing temperature due to increasing thermionic emission across the barrier. A simple model is constructed, based on thermionic emission at quasi-zero bias, that generates good fits to the experimental data. The negative differential resistance (NDR) region in the R{sub D}-T characteristic is a general effect and is demonstrated across a broad temperature range for a variety of Schottky structures grown on Si-, GaAs- and InP-substrates. In addition the NDR effect is harnessed in micro-scaled Pd/n-InP devices for the detection of low levels of hydrogen in an ambient atmosphere of nitrogen.

  11. Investigation of the electrochemical and electrocatalytic behavior of positively charged gold nanoparticle and L-cysteine film on an Au electrode

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Lingyan [Chongqing Key Laboratory of Analytical Chemistry, College of Chemistry and Chemical Engineering, Southwest China University, Chongqing 400715 (China); Forensic Identification Center, Southwest University of Political Science and Law, Chongqing 401120 (China); Yuan Ruo [Chongqing Key Laboratory of Analytical Chemistry, College of Chemistry and Chemical Engineering, Southwest China University, Chongqing 400715 (China)]. E-mail: yuanruo@swu.edu.cn; Chai Yaqing [Chongqing Key Laboratory of Analytical Chemistry, College of Chemistry and Chemical Engineering, Southwest China University, Chongqing 400715 (China); Li Xuelian [Chongqing Key Laboratory of Analytical Chemistry, College of Chemistry and Chemical Engineering, Southwest China University, Chongqing 400715 (China)

    2007-07-16

    Positively charged gold nanoparticle (positively charged nano-Au), which was prepared, characterized by {xi}-potential and transmission electron microscopy (TEM) was used in combination with L-cysteine to fabricate a modified electrode for electrocatalytic reaction of biomolecules. Compared with electrodes modified by negatively charged gold nanoparticle/L-cysteine, or L-cysteine alone, the electrode modified by the positively charged gold nanoparticle/L-cysteine exhibited excellent electrochemical behavior toward the oxidation of biomolecules such as ascorbic acid, dopamine and hydrogen peroxide. Moreover, the proposed mechanism for electrocatalytic response of positively charged gold nanoparticle was discussed. The immunosensor showed a specific to ascorbic acid in the range 5.1 x 10{sup -7}-6.7 x 10{sup -4} M and a low detection limit of 1.5 x 10{sup -7} M. The experimental results demonstrate that positively charged gold nanoparticle have more efficient electrocatalytic reaction than negatively charged gold nanoparticle, which opens up new approach for fabricating sensor.

  12. Powder processing of hybrid titanium neural electrodes

    Science.gov (United States)

    Lopez, Jose Luis, Jr.

    A preliminary investigation into the powder production of a novel hybrid titanium neural electrode for EEG is presented. The rheological behavior of titanium powder suspensions using sodium alginate as a dispersant are examined for optimal slip casting conditions. Electrodes were slip cast and sintered at 950°C for 1 hr, 1000°C for 1, 3, and 6 hrs, and 1050°C for 1 hr. Residual porosities from sintering are characterized using Archimedes' technique and image analysis. The pore network is gel impregnated by submerging the electrodes in electrically conductive gel and placing them in a chamber under vacuum. Gel evaporation of the impregnated electrodes is examined. Electrodes are characterized in the dry and gelled states using impedance spectrometry and compared to a standard silver- silver chloride electrode. Power spectral densities for the sensors in the dry and gelled state are also compared. Residual porosities for the sintered specimens were between 50.59% and 44.81%. Gel evaporation tests show most of the impregnated gel evaporating within 20 min of exposure to atmospheric conditions with prolonged evaporation times for electrodes with higher impregnated gel mass. Impedance measurements of the produced electrodes indicate the low impedance of the hybrid electrodes are due to the increased contact area of the porous electrode. Power spectral densities of the titanium electrode behave similar to a standard silver-silver chloride electrode. Tests suggest the powder processed hybrid titanium electrode's performance is better than current dry contact electrodes and comparable to standard gelled silver-silver chloride electrodes.

  13. Methods on Investigating Properties of Electrode/Electrolyte Interfaces in Lithium-Ion Batteries%锂离子电池电极界面特性研究方法

    Institute of Scientific and Technical Information of China (English)

    秦银平; 庄全超; 史月丽; 江利; 孙智; 孙世刚

    2011-01-01

    The rechargeable lithium-ion battery has been extensively used in mobile communication and portable instruments due to its many advantages, such as high volumetric and gravimetric energy density and low self-discharge rate. In addition, it is the most promising candidate as the power source for (hybrid) electric vehicles and stationary energy storage. The properties of electrode/electrolyte interfaces play an important role in the electrochemical performance of the electrode material and a battery, such as the capacities, irreversible charge "loss", rate capability and cyclability. In present paper, the methods to investigate the properties of electrode/electrolyte interfaces, for example, traditional electrochemical methods, microscopy methods, spectroscopic methods, electrochemical quartz crystal microgravimetry (EQCM) are summarized. The principles, advantages and disadvantages of these methods and their applications in investigating the properties of electrode/electrolyte interfaces, especially the progress in the combination of these methods to investigate the properties of electrode/electrolyte interfaces, are introduced in detail, and these methods will be considerable to study the new materials or the traditional materials for lithium-ion batteries in the future.%电极界面特性是影响锂离子电池充放电循环容量与稳定性的重要因素.本文总结了目前对电极界面特性进行研究的方法,主要包括传统的电化学方法、显微方法、谱学方法、电化学石英微晶天平等,重点论述了上述研究方法的原理、优缺点和在研究电极界面特性中的应用,以及这些方法相结合所取得的一些研究进展,并指出在今后的工作中,无论是对新材料的研究还是传统材料的研究,这些方法都仍将发挥重要作用.

  14. First-cycle defect evolution of Li1-xNi1/3Mn1/3Co1/3O2 lithium ion battery electrodes investigated by positron annihilation spectroscopy

    Science.gov (United States)

    Seidlmayer, Stefan; Buchberger, Irmgard; Reiner, Markus; Gigl, Thomas; Gilles, Ralph; Gasteiger, Hubert A.; Hugenschmidt, Christoph

    2016-12-01

    In this study the structure and evolution of vacancy type defects in lithium ion batteries are investigated in respect of crystallographic properties. The relation between positron annihilation and electronic structure is discussed in terms of structural dynamics during the lithiation process. Samples of Li1-xNi1/3Mn1/3Co1/3O2 (NMC-111) electrodes with decreasing lithium content (x = 0-0.7) covering the whole range of state of charge were electrochemically prepared for the non-destructive analysis using positron coincidence Doppler broadening spectroscopy (CDBS). The positron measurements allowed us to observe the evolution of the defect structure caused by the delithiation process in the NMC-111 electrodes. The combination of CDBS with X-ray diffraction for the characterization of the lattice structures enabled the analysis of the well-known kinetic-hindrance-effect in the first charge-discharge cycle and possible implications of vacancy ordering. In particular, CDBS revealed the highest degree of relithiation after discharge to 3.0 V at 55 °C. For the first time, we report on the successful application of CDBS on NMC-111 electrodes yielding new insights in the important role of defects caused by the delithiation process and the kinetic hindrance effect.

  15. Effect of electrode shape on grounding resistances - Part 1

    DEFF Research Database (Denmark)

    Ingeman-Nielsen, Thomas; Tomaskovicova, Sonia; Dahlin, Torleif

    2016-01-01

    . The focus-one protocol is a new method for estimating single electrode grounding resistances by measuring the resistance between a single electrode in an ERT array and all the remaining electrodes connected in parallel. For large arrays, the measured resistance is dominated by the grounding resistance...... of the electrode under test, the focus electrode. We have developed an equivalent circuit model formulation for the resistance measured when applying the focus-one protocol. Our model depends on the individual grounding resistances of the electrodes of the array, the mutual resistances between electrodes......, and the instrument input impedance. Using analytical formulations for the potentials around prolate and oblate spheroidal electrode models (as approximations for rod and plate electrodes), we have investigated the performance and accuracy of the focus-one protocol in estimating single-electrode grounding resistances...

  16. [Effects of different electrodes on bioelectrical impedance values].

    Science.gov (United States)

    Nakadomo, F; Tanaka, K; Yokoyama, T; Maeda, K

    1990-01-01

    Effects of different electrodes on bioelectrical impedance values measured by the Selco bioelectrical impedance plethysmograph (SIF-881, Japan) were investigated using 8 adult females (age: 35.3 +/- 7.6 yr, Ht: 156.9 +/- 3.8 cm, Wt: 57.1 +/- 9.9 kg, and hydrodensitometrically determined body fat: 29.4 +/- 6.0%). The Lectec MP3000 electrode (Liberty Carton, USA) and the Bipolar electrode (Sanwa, Japan) produced significantly higher impedance values when compared to the Disposable electrode (Adovance, Japan) and the ECG electrode (Nihon Kohden, Japan). The coefficient of variation was significantly lower for the Disposable electrode (0.8%) and the ECG electrode (0.2%) than that for the Lectec MP3000 electrode (2.3%) and the Bipolar electrode (4.9%). In conclusion, the ECG electrode provides higher bioelectrical impedance values with the highest reproducibility in the assessment of human body composition by the bioelectrical impedance plethysmography.

  17. Electrocatalytic activity of bismuth doped silver electrodes

    CERN Document Server

    Amjad, M

    2002-01-01

    Investigation of redox reactions on silver, and bismuth doped silver electrodes in aqueous KOH solutions, by using potentiostatic steady-state polarization technique, has been carried out. The redox wave potential and current displacements along with multiplicity of the latter have been examined. These electrodes were employed for the oxidation of organic molecules such as ethylamine in alkaline media. Subsequently, these electrodes were ranked with respect to their activity for the redox reactions. (author)

  18. Vibrational Stark Effect of the Electric-Field Reporter 4-Mercaptobenzonitrile as a Tool for Investigating Electrostatics at Electrode/SAM/Solution Interfaces

    Directory of Open Access Journals (Sweden)

    Peter Hildebrandt

    2012-06-01

    Full Text Available 4-mercaptobenzonitrile (MBN in self-assembled monolayers (SAMs on Au and Ag electrodes was studied by surface enhanced infrared absorption and Raman spectroscopy, to correlate the nitrile stretching frequency with the local electric field exploiting the vibrational Stark effect (VSE. Using MBN SAMs in different metal/SAM interfaces, we sorted out the main factors controlling the nitrile stretching frequency, which comprise, in addition to external electric fields, the metal-MBN bond, the surface potential, and hydrogen bond interactions. On the basis of the linear relationships between the nitrile stretching and the electrode potential, an electrostatic description of the interfacial potential distribution is presented that allows for determining the electric field strengths on the SAM surface, as well as the effective potential of zero-charge of the SAM-coated metal. Comparing this latter quantity with calculated values derived from literature data, we note a very good agreement for Au/MBN but distinct deviations for Ag/MBN which may reflect either the approximations and simplifications of the model or the uncertainty in reported structural parameters for Ag/MBN. The present electrostatic model consistently explains the electric field strengths for MBN SAMs on Ag and Au as well as for thiophenol and mercaptohexanoic acid SAMs with MBN incorporated as a VSE reporter.

  19. Design, development, and demonstration of a fully LabVIEW controlled in situ electrochemical Fourier transform infrared setup combined with a wall-jet electrode to investigate the electrochemical interface of nanoparticulate electrocatalysts under reaction conditions.

    Science.gov (United States)

    Nesselberger, Markus; Ashton, Sean J; Wiberg, Gustav K H; Arenz, Matthias

    2013-07-01

    We present a detailed description of the construction of an in situ electrochemical ATR-FTIR setup combined with a wall-jet electrode to investigate the electrocatalytic properties of nanoparticulate catalysts in situ under controlled mass transport conditions. The presented setup allows the electrochemical interface to be probed in combination with the simultaneous determination of reaction rates. At the same time, the high level of automation allows it to be used as a standard tool in electrocatalysis research. The performance of the setup was demonstrated by probing the oxygen reduction reaction on a platinum black catalyst in sulfuric electrolyte.

  20. Reproducibility of ERG responses obtained with the DTL electrode.

    Science.gov (United States)

    Hébert, M; Vaegan; Lachapelle, P

    1999-03-01

    Previous investigators have suggested that the DTL fibre electrode might not be suitable for the recording of replicable electroretinograms. We present experimental evidence that when used adequately, this electrode does permit the recording of highly reproducible retinal potentials.

  1. Long Life Nickel Electrodes for Nickel-Hydrogen Cells: Fiber Substrates Nickel Electrodes

    Science.gov (United States)

    Rogers, Howard H.

    2000-01-01

    Samples of nickel fiber mat electrodes were investigated over a wide range of fiber diameters, electrode thickness, porosity and active material loading levels. Thickness' were 0.040, 0.060 and 0.080 inches for the plaque: fiber diameters were primarily 2, 4, and 8 micron and porosity was 85, 90, and 95%. Capacities of 3.5 in. diameter electrodes were determined in the flooded condition with both 26 and 31% potassium hydroxide solution. These capacity tests indicated that the highest capacities per unit weight were obtained at the 90% porosity level with a 4 micron diameter fiber plaque. It appeared that the thinner electrodes had somewhat better performance, consistent with sintered electrode history. Limited testing with two-positive-electrode boiler plate cells was also carried out. Considerable difficulty with constructing the cells was encountered with short circuits the major problem. Nevertheless, four cells were tested. The cell with 95% porosity electrodes failed during conditioning cycling due to high voltage during charge. Discharge showed that this cell had lost nearly all of its capacity. The other three cells after 20 conditioning cycles showed capacities consistent with the flooded capacities of the electrodes. Positive electrodes made from fiber substrates may well show a weight advantage of standard sintered electrodes, but need considerably more work to prove this statement. A major problem to be investigated is the lower strength of the substrate compared to standard sintered electrodes. Problems with welding of leads were significant and implications that the electrodes would expand more than sintered electrodes need to be investigated. Loading levels were lower than had been expected based on sintered electrode experiences and the lower loading led to lower capacity values. However, lower loading causes less expansion and contraction during cycling so that stress on the substrate is reduced.

  2. FUEL CELL ELECTRODE MATERIALS

    Science.gov (United States)

    FUEL CELL ELECTRODE MATERIALS. RAW MATERIAL SELECTION INFLUENCES POLARIZATION BUT IS NOT A SINGLE CONTROLLING FACTOR. AVAILABLE...DATA INDICATES THAT AN INTERRELATIONSHIP OF POROSITY, AVERAGE PORE VOLUME, AND PERMEABILITY CONTRIBUTES TO ELECTRODE FUEL CELL BEHAVIOR.

  3. A Simple Hydrogen Electrode

    Science.gov (United States)

    Eggen, Per-Odd

    2009-01-01

    This article describes the construction of an inexpensive, robust, and simple hydrogen electrode, as well as the use of this electrode to measure "standard" potentials. In the experiment described here the students can measure the reduction potentials of metal-metal ion pairs directly, without using a secondary reference electrode. Measurements…

  4. Microresonator electrode design

    Science.gov (United States)

    Olsson, III, Roy H.; Wojciechowski, Kenneth; Branch, Darren W.

    2016-05-10

    A microresonator with an input electrode and an output electrode patterned thereon is described. The input electrode includes a series of stubs that are configured to isolate acoustic waves, such that the waves are not reflected into the microresonator. Such design results in reduction of spurious modes corresponding to the microresonator.

  5. Insulated ECG electrodes

    Science.gov (United States)

    Portnoy, W. M.; David, R. M.

    1973-01-01

    Insulated, capacitively coupled electrode does not require electrolyte paste for attachment. Other features of electrode include wide range of nontoxic material that may be employed for dielectric because of sputtering technique used. Also, electrode size is reduced because there is no need for external compensating networks with FET operational amplifier.

  6. Preparation of poly(3,4-ethylenedioxythiophene) nanofibers modified pencil graphite electrode and investigation of over-oxidation conditions for the selective and sensitive determination of uric acid in body fluids

    Energy Technology Data Exchange (ETDEWEB)

    Özcan, Ali, E-mail: aozcan3@anadolu.edu.tr; İlkbaş, Salih

    2015-09-03

    In this study, we have performed the preparation of over-oxidized poly(3,4-ethylenedioxythiophene) nanofibers modified pencil graphite electrode (Ox-PEDOT-nf/PGE) to develop a selective and sensitive voltammetric uric acid (UA) sensor. It was noted that the over-oxidation potential and time had a prominent effect on the UA response of the Ox-PEDOT-nf/PGE. Characterizations of PEDOT-nf/PGE and Ox-PEDOT-nf/PGE have been performed by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The highest voltammetric response of UA was obtained at pH 2.0. A linear relationship between the concentration of UA and oxidation peak currents was observed in the concentration range of 0.01–20.0 μM. The detection limit (1.3 nM according to S/N = 3) and reproducibility (RSD: 4.6 % for N:10) have also been determined. The effects of different substances on the determination of UA have been investigated. A very high peak separation value of 423 mV was obtained between UA and ascorbic acid which is the major interfering substance for UA. The use of Ox-PEDOT-nf/PGE has been successfully tested in the determination of UA in human blood serum and urine samples for the first time in the literature. - Highlights: • Modification of pencil graphite with over-oxidized PEDOT nanofibers was performed. • The prepared electrodes were used in the voltammetric determination of uric acid. • The over-oxidation potential and time has a prominent effect on the responses. • A very high peak separation (463 mV) was obtained between ascorbic and uric acids. • Analytical application of the electrodes was successfully tested in real samples.

  7. Interaction of vitamin B1 with bovine serum albumin investigation using vitamin B1-selective electrode: potentiometric and molecular modeling study.

    Science.gov (United States)

    Hosseinzadeh, Reza; Khorsandi, Khatereh

    2016-09-01

    Vitamin B1 or thiamin is one of the B vitamins. All B vitamins help the body to convert food (carbohydrates) into fuel (glucose), which produces energy. The B vitamins are necessary for healthy skin, eyes, hair, and liver. It also could help the nervous system function properly, and is necessary for brain functions. Drug interactions with protein can affect the distribution of the drug and eliminate the drug in living systems. In this study, the binding of thiamine hydrochloride (vitamin B1) to bovine serum albumin (BSA) was evaluated using a new proposed vitamin B1 (thiamine)-selective membrane electrode under various experimental conditions, such as pH, ionic strength, and protein concentration; in addition molecular modeling was applied as well. The binding isotherms plotted based on potentiometric data and analyzed using the Wyman binding potential concept. The apparent binding constant was determined and used for the calculation of intrinsic Gibbs free energy of binding. According to the electrochemical and molecular docking results, it can be concluded that the hydrophobic interactions and hydrogen binding are major interactions between BSA and vitamin B1.

  8. Investigation of electrodeposited cobalt sulphide counter electrodes and their application in next-generation dye sensitized solar cells featuring organic dyes and cobalt-based redox electrolytes

    Science.gov (United States)

    Swami, Sanjay Kumar; Chaturvedi, Neha; Kumar, Anuj; Kapoor, Raman; Dutta, Viresh; Frey, Julien; Moehl, Thomas; Grätzel, Michael; Mathew, Simon; Nazeeruddin, Mohammad Khaja

    2015-02-01

    Cobalt sulphide (CoS) films are potentiodynamically deposited on fluorine-doped tin oxide (FTO) coated glass substrates employing one, three and five sweep cycles (CoS-I, CoS-III and CoS-V respectively). Analysis of the CoS-III film by impedance spectroscopy reveals a lower charge transfer resistance (RCT) than that measured for Pt CE (0.75 Ω cm-2 and 0.85 Ω cm-2, respectively). The CoS films are used as counter electrodes (CE) in dye-sensitized solar cells (DSSCs) featuring the combination of a high absorption coefficient organic dye (C218) and the cobalt-based redox electrolyte [Co(bpy)3]2/3+. DSSCs fabricated with the CoS-III CE yield the highest short-circuit current density (JSC) of 12.84 mA cm-2, open circuit voltage (VOC) of 805 mV and overall power conversion efficiency (PCE) of 6.72% under AM 1.5G illumination (100 mW cm-2). These values are comparable to the performance of an analogous cell fabricated with the Pt CE (PCE = 6.94%). Owing to relative lower cost (due to the inherit earth abundance of Co) and non-toxicity, CoS can be considered as a promising alternative to the more expensive Pt as a CE material for next-generation DSSCs that utilize organic dyes and cobalt-based redox electrolytes.

  9. Plastic Membrane Sensor from a Disposed Combined Glass Electrode

    Science.gov (United States)

    Marafie, Hayat M.; Shoukry, Adel F.; Alshatti, Laila A.

    2007-01-01

    The construction of combined plastic membrane electrode for hydralazinium cation from a disposed glass electrode is described. A variety of electrodes could be prepared by students using other types of polymers, plasticizers, or exchangers which could also help to study effects of pH and temperature, or environmental investigations.

  10. Why is the electroanalytical performance of carbon paste electrodes involving an ionic liquid binder higher than paraffinic binders? A simulation investigation.

    Science.gov (United States)

    Ghatee, M H; Namvar, S; Zolghadr, A R; Moosavi, F

    2015-10-14

    Recently, carbon paste electrodes (CPE) fabricated using an ionic liquid (IL) binder have shown enhanced electroanalytical performance over conventional paraffinic binders. Molecular dynamics (MD) simulations of graphite mixed with ionic liquid and with paraffin binder can unravel the potential atomistic factors responsible for such enhancement. Based on an experimentally optimized binder/graphite mass ratio, which has been reported to be crucial for such a performance, comprehensive simulations (at 323 K) are performed with the ensembles involving an ionic liquid binder (1-butyl-3-methylimidazolium hexafluorophosphate, [C4mim]PF6) and a paraffin binder (n-C20H42) mixed with graphite comprising large-size hexagonal-shaped double graphene plates. Structural analysis indicates both binders form only a monolayer on the graphite surface, covering the surface locally by IL but all-encompassing by paraffin. With charged and uncharged graphite, the IL monolayer tends to cover mainly the graphite center without approaching the edge planes. On the contrary, a monolayer of the paraffin binder covers uniformly the center, near the center, and the edge planes. Cations and anions of the IL form well-defined two dimensional pentagonal matrixes with characteristic high adsorption energy, almost 2.4 times higher than paraffin adsorption. The cation and anion coordination ability of the IL is responsible for such a local distribution. The simulation of these phenomena under experimental conditions unravels strong two-dimensional coordination properties inherent to the ionic liquid when distributed over the graphite surface. This direct MD simulation comparison of the IL properties with an organic liquid counterpart, made for the first time, can be used to explain the high electroanalytical performance (electron transfer) of CPEs involving an IL binder over paraffin binders.

  11. Electrode porosity and effective electrocatalyst activity in electrode-membrane-assemblies (MEAs) of PEMFCs

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, A.; Wendt, H. [Institut fuer Chemische Technologie, Darmstadt (Germany)

    1996-12-31

    New production technologies of membrane-electrode-assemblies for PEWCs which ensure almost complete catalyst utilization by {open_quotes}wetting{close_quotes} the internal catalyst surface with the ionomeric electrolyte, allow for a reduction of Pt-loadings from prior 4 mg cm{sup -2} to now less than 0.5 mg cm{sup -2}. Such electrodes are not thicker than from 5 to 10 {mu}m. Little has been published hitherto about the detailed micromorphology of such electrodes and the role of electrode porosity on electrode performance. It is well known, that the porosity of thicker fuel cell electrodes, e.g. of PAFC or AFC electrodes is decisive for their performance. Therefore the issue of this investigation is to measure and to modify the porosity of electrodes prepared by typical MEA production procedures and to investigate the influence of this porosity on the effective catalyst activity for cathodic reduction of oxygen from air in membrane cells. It may be anticipated that any mass transfer hindrance of gaseous reactants into porous electrodes would manifest itself rather in the conversion of dilute gases than in the conversion of pure gases (e.g. neat oxygen). Therefore in this investigation the performance of membrane cell cathodes with non pressurized air had been compared to that with neat oxygen at cathodes which had a relatively low Pt-loading of 0.15 mg cm{sup -2}.

  12. Electrochemical characterization of electrolytes and electrodes for lithium-ion batteries. Development of a new measuring method for electrochemical investigations on electrodes with the electrochemical quartz crystal microbalance (EQCM); Elektrochemische Charakterisierung von Elektrolyten und Elektroden fuer Lithium-Ionen-Batterien. Entwicklung einer neuen Messmethode fuer elektrochemische Untersuchungen an Elektroden mit der EQCM

    Energy Technology Data Exchange (ETDEWEB)

    Moosbauer, Dominik Johann

    2010-11-09

    In this work the conductivities of four different lithium salts, LiPF6, LiBF4, LiDFOB, and LiBOB in the solvent mixture EC/DEC (3/7) were investigated. Furthermore, the influence of eight ionic liquids (ILs) as additives on the conductivity and electrochemical stability of lithium salt-based electrolytes was studied. The investigated salts were the well-known lithium LiPF6 and LiDFOB. Conductivity studies were performed over the temperature range (238.15 to 333.15) K. The electrochemical stabilities of the solutions were determined at aluminum electrodes. The salt solubility of LiBF4 and LiDFOB in EC/DEC (3/7) was measured with the quartz crystal microbalance (QCM), a method developed in our group. Moreover, a method to investigate interactions between the electrolyte and electrode components with the electrochemical quartz crystal microbalance (EQCM) was developed. First, investigations of corrosion and passivation effects on aluminum with different lithium salts were performed and masses of deposited products estimated. Therefore, the quartzes were specially prepared with foils. Active materials of cathodes, in this work lithium iron phosphate (LiFePO4), were also investigated with the EQCM by a new method. [German] In dieser Arbeit wurden die Leitfaehigkeiten von vier unterschiedlichen Salzen, LiPF6, LiBF4, LiDFOB und LiBOB in dem Loesemittelgemisch EC/DEC (3/7) untersucht. Des Weiteren wurde der Einfluss von acht Ionischen Fluessigkeiten (ILs) als Additive fuer Lithium-Elektrolyte auf die elektrochemische Stabilitaet und die Leitfaehigkeit studiert. Die untersuchten Salze waren LiPF6 und LiDFOB. Die Leitfaehigkeitsmessungen wurden in einem Temperaturbereich von (238,15 bis 333,15) K durchgefuehrt. Die elektrochemischen Stabilitaeten der Elektrolyte fanden an Aluminium statt. Mit einer an der Arbeitsgruppe entwickelten neuen Methode wurden zudem die Salzloeslichkeiten von LiBF4 und LiDFOB in EC/DEC (3/7) mit der Quarzmikrowaage (QCM) bestimmt. Weiterhin wurden

  13. Handbook of reference electrodes

    CERN Document Server

    Inzelt, György; Scholz, Fritz

    2013-01-01

    Reference Electrodes are a crucial part of any electrochemical system, yet an up-to-date and comprehensive handbook is long overdue. Here, an experienced team of electrochemists provides an in-depth source of information and data for the proper choice and construction of reference electrodes. This includes all kinds of applications such as aqueous and non-aqueous solutions, ionic liquids, glass melts, solid electrolyte systems, and membrane electrodes. Advanced technologies such as miniaturized, conducting-polymer-based, screen-printed or disposable reference electrodes are also covered. Essen

  14. Pocket ECG electrode

    Science.gov (United States)

    Lund, Gordon F. (Inventor)

    1982-01-01

    A low-noise electrode suited for sensing electrocardiograms when chronically and subcutaneously implanted in a free-ranging subject. The electrode comprises a pocket-shaped electrically conductive member with a single entrance adapted to receive body fluids. The exterior of the member and the entrance region is coated with electrical insulation so that the only electrolyte/electrode interface is within the member remote from artifact-generating tissue. Cloth straps are bonded to the member to permit the electrode to be sutured to tissue and to provide electrical lead flexure relief.

  15. Surface modification of recording electrodes

    OpenAIRE

    Iaci Miranda Pereira; Sandhra Maria de Carvalho; Rodrigo Lambert Oréfice; Marcelo Bariatto Andrade Fontes; Lilian Anee Muniz Arantes; Núbia Figueiró; Maria de Fátima Leite; Hercules Pereira Neves

    2013-01-01

    Waterborne Polyurethanes (PUs) are a family of polymers that contains urethane linkages synthesized in an aqueous environment and are thus free of organic solvents. Recently, waterborne PUs have been extensively studied for biomedical applications because of their biocompatibility. The present work investigates the following: (1) the impact on electrical performance of electrode materials (platinum and silicon) modified chemically by a layer of waterborne PU, and (2) the behavior of rat cardi...

  16. Complete electrode model in EEG: relationship and differences to the point electrode model

    Science.gov (United States)

    Pursiainen, S.; Lucka, F.; Wolters, C. H.

    2012-02-01

    In electroencephalography (EEG) source analysis, a primary current density generated by the neural activity of the brain is reconstructed from external electrode voltage measurements. This paper focuses on accurate and effective simulations of EEG through the complete electrode model (CEM). The CEM allows for the incorporation of the electrode size, shape and effective contact impedance into the forward simulation. Both neural currents in the brain and shunting currents between the electrodes and the skin can affect the measured voltages in the CEM. The goal of this study was to investigate the CEM by comparing it with the point electrode model (PEM), which is the current standard electrode model for EEG. We used a three-dimensional, realistic and high-resolution finite element head model as the reference computational domain in the comparison. The PEM could be formulated as a limit of the CEM, in which the effective impedance of each electrode goes to infinity and the size tends to zero. Numerical results concerning the forward and inverse errors and electrode voltage strengths with different impedances and electrode sizes are presented. Based on the results obtained, limits for extremely high and low impedance values of the shunting currents are suggested.

  17. Membrane Bioprobe Electrodes

    Science.gov (United States)

    Rechnitz, Garry A.

    1975-01-01

    Describes the design of ion selective electrodes coupled with immobilized enzymes which operate either continuously or on drop-sized samples. Cites techniques for urea, L-phenylalanine and amygdalin. Micro size electrodes for use in single cells are discussed. (GH)

  18. Experimental investigation of the effect of indium content on the CuIn{sub 5}S{sub 8} electrodes using electrochemical impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gannouni, M., E-mail: gm_mounir@yahoo.fr; Assaker, I. Ben; Chtourou, R.

    2015-01-15

    This paper reports on the use of electrochemical impedance spectroscopy to investigate the electrochemical behavior of spinel CuIn{sub 5}S{sub 8}/electrolyte interface. The CuIn{sub 5}S{sub 8} spinel films have been potentiostatically deposited onto indium tin oxide (ITO)-coated glass substrate. CuCl{sub 2} and InCl{sub 3} mixed solutions with different [Cu]/[In] ratios were used as cation precursor and Na{sub 2}S{sub 2}O{sub 3} as the anion precursor in acidic solution and at room temperature. The effect of the [Cu]/[In] ratio in the precursor solution on the structural, chemical stoichiometry, and morphological properties of prepared samples, as well as the electrochemical behavior of the CuIn{sub 5}S{sub 8}/electrolyte interface was investigated. The electrochemical impedance spectroscopy data have been modeled using an equivalent circuit approach. Several parameters such as, flat-band potential and free carrier concentration were determined by the change in the Mott–Schottky plots.

  19. A semiconductor based electrode

    Energy Technology Data Exchange (ETDEWEB)

    Khamatani, A.; Kobayasi, K.

    1983-03-30

    The semiconductor electrode is submerged into an electrolyte which is held in the illuminated chamber. The other electrode is placed in a dark chamber connected with the channel to be illuminated, which has a partition in the form of a membrane. An electric current flows in the external circuit of the element with illumination of the first electrode. The illuminated electrode is covered with a thin film of a substance which is stable with the action of the electrolyte. The film is made of Si02, A1203, GaN or A1N. The protective coating makes it possible to use materials less stable than Ti02 in a rutile modification, but which have higher characteristics than the GaP, GaAs, CdS and InP, for making the electrode.

  20. Improved technology for manufacture of carbon electrodes

    Indian Academy of Sciences (India)

    A Platon; A Dumbrava; N Iutes-Petrescu; Luzia Simionescu

    2000-02-01

    Current industrial carbon electrodes are typically manufactured by blending petroleum coke particles (the filler) with molten coal tar pitch (the binder) and extruding the resultant mix to form the `green electrode’. This is then baked under controlled conditions. In case of usage as anodes in steel electric furnaces (or as other carbon and graphite products), the electrodes could undergo further processing like pitch impregnation or graphitization. During heat treatment, some of the organics are destructively distilled, vaporized or decomposed, resulting in carbon deposition in the electrode. As the vaporized materials exit the body of the electrode they cause porosity in the walls, which results in reduction in density, current carrying capacity and flexural strength. The paper presents investigations to improve some physico-chemical characteristics of these electrodes (such as coefficient of thermal expansion, mechanical strengths, density, pore volume, porosity etc.), obtained in different manufacture steps, by addition of varieties of coal tar pitch. These include attempts to improve the chemical compatibility of the coke-pitch system in the mixture and establish the method and the point of introduction of additive, the concentration required and appropriate analytical control during the entire manufacture. Methods of analysis used include thermogravimetry and porosimetry. The microstructure of the electrodes is investigated through a wide range and the data obtained include pore size and pore volume distribution, surface area, porosity, particle size distribution and type of pores. The overall results clearly indicate better characteristics and performance for electrodes with additives as against electrodes without them, such as lower porosity, lower thermal expansion coefficients and greater mechanical strength. These data are analyzed with respect to the process step and electrode type.

  1. Materials analyses and electrochemical impedance of implantable metal electrodes.

    Science.gov (United States)

    Howlader, Matiar M R; Ul Alam, Arif; Sharma, Rahul P; Deen, M Jamal

    2015-04-21

    Implantable electrodes with high flexibility, high mechanical fixation and low electrochemical impedance are desirable for neuromuscular activation because they provide safe, effective and stable stimulation. In this paper, we report on detailed materials and electrical analyses of three metal implantable electrodes - gold (Au), platinum (Pt) and titanium (Ti) - using X-ray photoelectron spectroscopy (XPS), scanning acoustic microscopy, drop shape analysis and electrochemical impedance spectroscopy. We investigated the cause of changes in electrochemical impedance of long-term immersed Au, Pt and Ti electrodes on liquid crystal polymers (LCPs) in phosphate buffered saline (PBS). We analyzed the surface wettability, surface and interface defects and the elemental depth profile of the electrode-adhesion layers on the LCP. The impedance of the electrodes decreased at lower frequencies, but increased at higher frequencies compared with that of the short-term immersion. The increase of impedances was influenced by the oxidation of the electrode/adhesion-layers that affected the double layer capacitance behavior of the electrode/PBS. The oxidation of the adhesion layer for all the electrodes was confirmed by XPS. Alkali ions (sodium) were adsorbed on the Au and Pt surfaces, but diffused into the Ti electrode and LCPs. The Pt electrode showed a higher sensitivity to surface and interface defects than that of Ti and Au electrodes. These findings may be useful when designing electrodes for long-term implantable devices.

  2. Copper(I) electrode function of two types of copper(II) ion-selective electrodes.

    Science.gov (United States)

    Neshkova, M; Sheytanov, H

    1985-08-01

    The response of two types of solid-state copper ion-selective electrodes with homogeneous membranes of CuAgSe and Cu(2-x)Se has been investigated in copper(I) solutions, prepared electrochemically by insitu generation from a copper anode in chloride medium. The selectivity coefficient K(pot)(Cu+, Cu(2+)) both types of electrodes has been determined. It is 10(-5.7) for the copper selenide sensor, and 10(-6.2) for the copper silver selenide one. These values are very close to that calculated for an exchange reaction proceeding on the electrode surface. The similarity in K(pot)(Cu+ ,Cu(2+)) values for different chalcogenidebased sensors suggests a common potential-generating mechanism. High chloride concentration does not interfere with the electrode response towards Cu(I), but distorts the electrode response to Cu(II).

  3. Solid Reference Electrode of Metallurgical Oxygen Sensor

    Institute of Scientific and Technical Information of China (English)

    LOU Tian-jun; KONG Xiang-hua; HUANG Ke-qin; LIU Qing-guo

    2006-01-01

    The thermal equilibrium state of the reference electrode was investigated. The results show that the temperature difference between the inside and the outside of zirconia tube was very small and the Seebeck effect can be ignored after the sensor was dipped into liquid steel for more than 2 s. A special sensor was designed to test the relation between the EMF (electromotive force) of sensor and the thermal equilibrium state of the reference electrode. Based on these results, it is suggested that the peak in EMF curve was caused by the change of oxygen potential in reference electrode before the thermal equilibrium was reached. If NiO was added by 2%-5% to the Cr/Cr2O3 reference electrode, the peak in EMF curve could be eliminated.

  4. Understanding the Effects of Electrode Formulation on the Mechanical Strength of Composite Electrodes for Flexible Batteries.

    Science.gov (United States)

    Gaikwad, Abhinav M; Arias, Ana Claudia

    2017-02-22

    Flexible lithium-ion batteries are necessary for powering the next generation of wearable electronic devices. In most designs, the mechanical flexibility of the battery is improved by reducing the thickness of the active layers, which in turn reduces the areal capacity and energy density of the battery. The performance of a battery depends on the electrode composition, and in most flexible batteries, standard electrode formulation is used, which is not suitable for flexing. Even with considerable efforts made toward the development of flexible lithium-ion batteries, the formulation of the electrodes has received very little attention. In this study, we investigate the relation between the electrode formulation and the mechanical strength of the electrodes. Peel and drag tests are used to compare the adhesion and cohesion strength of the electrodes. The strength of an electrode is sensitive to the particle size and the choice of polymeric binder. By optimizing the electrode composition, we were able to fabricate a high areal capacity (∼2 mAh/cm(2)) flexible lithium-ion battery with conventional metal-based current collectors that shows superior electrochemical and mechanical performance in comparison to that of batteries with standard composition.

  5. Note: electrode polarization of Galinstan electrodes for liquid impedance spectroscopy.

    Science.gov (United States)

    Mellor, Brett L; Kellis, Nathan A; Mazzeo, Brian A

    2011-04-01

    Electrode polarization is a significant obstacle in the impedance measurements of ionic liquids. An atomically smooth electrode surface could potentially reduce unwanted impedance contributions from electrode polarization. Liquid metal electrodes were formed by adhering Galinstan to acrylic plates in a parallel-plate capacitor arrangement. Electrode polarization was compared to a similar cell with stainless steel electrodes. The impedance of salt and protein solutions (β-lactoglobulin) was measured from 40 Hz to 110 MHz. Because of oxide layer formation, the performance of the Galinstan electrode is significantly different than the theoretical ideal.

  6. Fabric-Based Wearable Dry Electrodes for Body Surface Biopotential Recording.

    Science.gov (United States)

    Yokus, Murat A; Jur, Jesse S

    2016-02-01

    A flexible and conformable dry electrode design on nonwoven fabrics is examined as a sensing platform for biopotential measurements. Due to limitations of commercial wet electrodes (e.g., shelf life, skin irritation), dry electrodes are investigated as the potential candidates for long-term monitoring of ECG signals. Multilayered dry electrodes are fabricated by screen printing of Ag/AgCl conductive inks on flexible nonwoven fabrics. This study focuses on the investigation of skin-electrode interface, form factor design, electrode body placement of printed dry electrodes for a wearable sensing platform. ECG signals obtained with dry and wet electrodes are comparatively studied as a function of body posture and movement. Experimental results show that skin-electrode impedance is influenced by printed electrode area, skin-electrode interface material, and applied pressure. The printed electrode yields comparable ECG signals to wet electrodes, and the QRS peak amplitude of ECG signal is dependent on printed electrode area and electrode on body spacing. Overall, fabric-based printed dry electrodes present an inexpensive health monitoring platform solution for mobile wearable electronics applications by fulfilling user comfort and wearability.

  7. Porous Electrode Studies.

    Science.gov (United States)

    1980-07-01

    representation and analysis for their observed current distributions. Simonsson won the young author’s award of the Electrochemical Society for his paper...and T. Katan, Proc. Symp. Energy Storage and Conversion, the Electrochemical Society 77-6, 770 (1977) The optimum thickness of porous electrodes is...Chloride Electrodes; Surface Morphology on Charging and Dis- charging," T. Katan, S. Szpak, and D. N. Bennion, The Electrochemical Society , 143rd National

  8. Investigation of Anodic Oxidation Mechanism of Na2S Solution on Graphite Electrode%石墨电极上硫化钠的阳极氧化机理探索

    Institute of Scientific and Technical Information of China (English)

    易清风

    2000-01-01

    Electrochemical behavior of aqueous sodium sulfide solution at graphite anode,under the condition of different concentrations of Na2S and different temperatures,has been investigated by cyclic voltammetry and chronopotentiometry.The results show that the anodic oxidation of aqueous sulfide solution is irreversible and that polysulfides are formed in rate-determining step of the anodic oxidation.With the increase of electrolytic temperature,potentials corresponding to anodic peaks shift to more negative and those corresponding to cathodic peaks shift to more positive,which indicates that the elevating of temperature is favorable to both oxidation of the sulfide and reduction of products polysulfides or elemental sulfur.Rate constants ks of standard electrode reaction for anodic oxidation of Na2S solution are between 10- 4.08~ 10- 4.35cm· s- 1 at 70℃ .Chronopotentiometric studies show two potential peaks in time-potential curve for a smaller current density value.The potential peaks may result from a self-catalytic effect taking place due to both dissolution of elemental sulfur by S2- ,HS- and ,and transition reactions among polysulfides.The potential peaks disappear with the increasing of anodic current density.

  9. Investigation into real-time pressure sensing properties of SnO{sub 2}, TiO{sub 2}, and TiO{sub 2}/ZnO thick films with interdigitated electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Korostynska, O., E-mail: olga.korostynska@dit.ie [School of Physics, Dublin Institute of Technology, Dublin (Ireland); Arshak, A. [Department of Physics, University of Limerick, Limerick (Ireland); Arshak, K. [Electronic and Computer Engineering Department, University of Limerick, Limerick (Ireland); Morris, D. [Ballybrien, Ballymacarbry, Clonmel Co., Tipperary (Ireland)

    2011-09-25

    Highlights: > The pressure sensing properties of metal oxides thick film capacitors are reported. > At the applied load of 5 kPa, the response times of 2.5 s, 5.6 s and 4 s were recorded for SnO{sub 2}, TiO{sub 2}, and TiO{sub 2}/ZnO sensors, respectively. > These pressure sensors have long-term stability and low hysteresis. > They are reusable, as their electrical properties were restored by annealing. - Abstract: The pressure sensing properties of nanocomposite SnO{sub 2}, TiO{sub 2}, and TiO{sub 2}/ZnO thick film capacitors with interdigitated electrodes are investigated. To form the dielectric layers, the metal oxides powders were respectively mixed with isopropanol, wet ball milled for 24 h, then the mixtures were dried at 120 deg. C and further the powders were placed under 2 tonnes of pressure to form pellets, which were fired at 1250 deg. C (rate of 5 deg. C/min) in a vacuum of 6 x 10{sup -3} mbar for 5 h, followed by cooling (rate of 3 deg. C/min). After firing, the resultant nanopowders were mixed with 7 wt.% of polyvinyl butyral (binder) and suitable amount of ethylenglycolmonobutylether (solvent) to form the pastes. These were screen-printed over the Ag electrodes on alumina substrates to form SnO{sub 2}, TiO{sub 2}, and TiO{sub 2}/ZnO capacitor pressure sensors accordingly. The evaluation of pressure sensing properties of these sensors was performed using a HP 4192A Impedance Analyser, which recorded the changes in the values of the capacitances under different mechanical stresses. At the applied load of 5 kPa, the response times of 2.5 s, 5.6 s and 4 s were recorded for SnO{sub 2}, TiO{sub 2}, and TiO{sub 2}/ZnO sensors, respectively. In addition to instant response times, these pressure sensors have the advantage of being reusable, as their electrical properties were restored to the original value after annealing for 2 h at 80 deg. C. Moreover, one year later after the initial testing, the sensors were still operational and produced similar time

  10. Sensor employing internal reference electrode

    DEFF Research Database (Denmark)

    2013-01-01

    The present invention concerns a novel internal reference electrode as well as a novel sensing electrode for an improved internal reference oxygen sensor and the sensor employing same.......The present invention concerns a novel internal reference electrode as well as a novel sensing electrode for an improved internal reference oxygen sensor and the sensor employing same....

  11. A multi-electrode biomimetic electrolocation sensor

    Science.gov (United States)

    Mayekar, K.; Damalla, D.; Gottwald, M.; Bousack, H.; von der Emde, G.

    2012-04-01

    We present the concept of an active multi-electrode catheter inspired by the electroreceptive system of the weakly electric fish, Gnathonemus petersii. The skin of this fish exhibits numerous electroreceptor organs which are capable of sensing a self induced electrical field. Our sensor is composed of a sending electrode and sixteen receiving electrodes. The electrical field produced by the sending electrode was measured by the receiving electrodes and objects were detected by the perturbation of the electrical field they induce. The intended application of such a sensor is in coronary diagnostics, in particular in distinguishing various types of plaques, which are major causes of heart attack. For calibration of the sensor system, finite element modeling (FEM) was performed. To validate the model, experimental measurements were carried out with two different systems. The physical system was glass tubing with metal and plastic wall insertions as targets. For the control of the experiment and for data acquisition, the software LabView designed for 17 electrodes was used. Different parameters of the electric images were analyzed for the prediction of the electrical properties and size of the inserted targets in the tube. Comparisons of the voltage modulations predicted from the FEM model and the experiments showed a good correspondence. It can be concluded that this novel biomimetic method can be further developed for detailed investigations of atherosclerotic lesions. Finally, we discuss various design strategies to optimize the output of the sensor using different simulated models to enhance target recognition.

  12. Improving myoelectric pattern recognition robustness to electrode shift by changing interelectrode distance and electrode configuration.

    Science.gov (United States)

    Young, Aaron J; Hargrove, Levi J; Kuiken, Todd A

    2012-03-01

    Pattern recognition of myoelectric signals for prosthesis control has been extensively studied in research settings and is close to clinical implementation. These systems are capable of intuitively controlling the next generation of dexterous prosthetic hands. However, pattern recognition systems perform poorly in the presence of electrode shift, defined as movement of surface electrodes with respect to the underlying muscles. This paper focused on investigating the optimal interelectrode distance, channel configuration, and electromyography feature sets for myoelectric pattern recognition in the presence of electrode shift. Increasing interelectrode distance from 2 to 4 cm improved pattern recognition system performance in terms of classification error and controllability (p pattern recognition control. Finally, we investigated different feature sets for pattern recognition control using a linear discriminant analysis classifier and found that an autoregressive set significantly (p < 0.01) reduced sensitivity to electrode shift compared to a traditional time-domain feature set.

  13. Composite carbon foam electrode

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, S.T.; Pekala, R.W.; Kaschmitter, J.L.

    1997-05-06

    Carbon aerogels used as a binder for granulated materials, including other forms of carbon and metal additives, are cast onto carbon or metal fiber substrates to form composite carbon thin film sheets. The thin film sheets are utilized in electrochemical energy storage applications, such as electrochemical double layer capacitors (aerocapacitors), lithium based battery insertion electrodes, fuel cell electrodes, and electrocapacitive deionization electrodes. The composite carbon foam may be formed by prior known processes, but with the solid particles being added during the liquid phase of the process, i.e. prior to gelation. The other forms of carbon may include carbon microspheres, carbon powder, carbon aerogel powder or particles, graphite carbons. Metal and/or carbon fibers may be added for increased conductivity. The choice of materials and fibers will depend on the electrolyte used and the relative trade off of system resistivity and power to system energy. 1 fig.

  14. Composite carbon foam electrode

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, Steven T. (San Leandro, CA); Pekala, Richard W. (Pleasant Hill, CA); Kaschmitter, James L. (Pleasanton, CA)

    1997-01-01

    Carbon aerogels used as a binder for granularized materials, including other forms of carbon and metal additives, are cast onto carbon or metal fiber substrates to form composite carbon thin film sheets. The thin film sheets are utilized in electrochemical energy storage applications, such as electrochemical double layer capacitors (aerocapacitors), lithium based battery insertion electrodes, fuel cell electrodes, and electrocapacitive deionization electrodes. The composite carbon foam may be formed by prior known processes, but with the solid particles being added during the liquid phase of the process, i.e. prior to gelation. The other forms of carbon may include carbon microspheres, carbon powder, carbon aerogel powder or particles, graphite carbons. Metal and/or carbon fibers may be added for increased conductivity. The choice of materials and fibers will depend on the electrolyte used and the relative trade off of system resistivty and power to system energy.

  15. The Composite Insertion Electrode

    DEFF Research Database (Denmark)

    Atlung, Sven; Zachau-Christiansen, Birgit; West, Keld;

    1984-01-01

    . The theoretical basis for such electrodes is discussedand, using a simplified model, equations are derived to describe the distribution of potential and current duringdischarge/charge operation. Under the assumption that the insertion compound particles are small enough to ensureequilibrium, and that the local...... electrode potential depends linearly on the degree of insertion, these equations are solvedto obtain analytical expressions for the discharge curve. It is shown that the parameters which determine the dischargebehavior for a given discharge current are simply related to the effective ionic and electronic...

  16. Ion-selective electrodes

    CERN Document Server

    Mikhelson, Konstantin N

    2013-01-01

    Ion-selective electrodes (ISEs) have a wide range of applications in clinical, environmental, food and pharmaceutical analysis as well as further uses in chemistry and life sciences. Based on his profound experience as a researcher in ISEs and a course instructor, the author summarizes current knowledge for advanced teaching and training purposes with a particular focus on ionophore-based ISEs. Coverage includes the basics of measuring with ISEs, essential membrane potential theory and a comprehensive overview of the various classes of ion-selective electrodes. The principles of constructing I

  17. Single Electrode Heat Effects

    DEFF Research Database (Denmark)

    Jacobsen, Torben; Broers, G. H. J.

    1977-01-01

    SP, of theelectrode reaction. eta is the overvoltage at the electrode. This equation is appliedto a high temperature carbonate fuel cell. It is shown that the Peltier entropyterm by far exceeds the heat production due to the irreversible losses, and thatthe main part of heat evolved at the cathode is reabsorbed......The heat evolution at a single irreversibly working electrode is treated onthe basis of the Brønsted heat principle. The resulting equation is analogous to the expression for the total heat evolution in a galvanic cellwith the exception that –DeltaS is substituted by the Peltier entropy, Delta...

  18. Reference Electrodes in Metal Corrosion

    Directory of Open Access Journals (Sweden)

    S. Szabó

    2010-01-01

    Full Text Available With especial regard to hydrogen electrode, the theoretical fundamentals of electrode potential, the most important reference electrodes and the electrode potential measurement have been discussed. In the case of the hydrogen electrode, it have been emphasised that there is no equilibrium between the hydrogen molecule (H2 and the hydrogen (H+, hydronium (H3O+ ion in the absence of a suitable catalyst. Taking into account the practical aspects as well, the theorectical basis of working of hydrogen, copper-copper sulphate, mercury-mercurous halide, silver-silver halide, metal-metal oxide, metal-metal sulphate and “Thalamid” electrodes, has been discussed.

  19. Kinetics of electrochemical process of galena electrode in diethyldithiocarbamate solution

    Institute of Scientific and Technical Information of China (English)

    覃文庆; 邱冠周; 胡岳华; 徐竞

    2001-01-01

    The electrode process of galena in diethyldithiocarbamate (DDTC) solution at pH 11.4 has been investigated using cyclic voltammetry, potentiostatic and chronopotentiometry. Electrodeposit of PbD2 on galena electrode surface can occur while the electrode potential is higher than -0.05V. The relationship between the current density caused by diffusion and reaction time has been ascertained, and the diffusion coefficient of DDTC on galena surface in DDTC solution is about 1.12×10-6 cm2/s. A passive PbD2 film covers the surface of galena electrode.

  20. A New Ritodrine Selective Electrode and its Pharmaceutical Application

    Directory of Open Access Journals (Sweden)

    Reda Ammar

    2010-01-01

    Full Text Available A novel ritodrine hydrochloride ion-selective PVC membrane electrode based on ion-pair complex of ritodrine-tetra phenyl borate was prepared with di-n-butyl phosphate as a plasticizer. The influences of membrane composition, temperature, pH of the test solution and foreign ions on the electrode performance were investigated. The electrode showed a Nernstian response over a wide ritodrine concentration range (1×10−5- 1×10−2 M with a slope of 59.33 mV decade−1 and was found to be very selective, precise and usable within the pH range 3-7.5. The standard electrode potentials, E°, were determined at different temperatures and used to calculate the isothermal temperature coefficient (dE°/dT of the electrode, which was 0.00075. The electrode was successfully used for potentiometric determination of ritodrine hydrochloride both in pure solutions and in pharmaceutical preparations.

  1. ERG electrode in pediatric patients: comparison of DTL fiber, PVA-gel, and non-corneal skin electrodes.

    Science.gov (United States)

    Coupland, S G; Janaky, M

    1989-04-01

    Hard contact lens electrodes have been the type most frequently used in pediatric electroretinography but they are not well-tolerated by patients. The Dawson Trick Litzkow fiber electrode is better tolerated but it is fragile and difficult to sterilize. A new electrode made from anomalous polyvinyl alcohol gel is inexpensive, has stable electrical recording properties, and can be discarded after use. Dermal electrodes have been used for electroretinogram recording for some time; however, there are few reports that directly compare their performance against standard contact lens assemblies. We compared the DTL and the polyvinyl gel electrodes in the same group of subjects and investigated their recording characteristics along with non corneal skin electrodes placed on the infraorbital ridge. Signal-averaged electroretinogram were obtained under both scotopic and photopic stimulation conditions and the implicit time and amplitudes of the a- and b-waves were determined. Overall, dermal recordings generally had shorter implicit times and lower amplitudes than with the fiber or gel electrodes. The dermal electrodes were best tolerated and outlasted the corneal in repeated use. Since amplitude characteristics of the dermal electrodes were generally about 50% of that obtained with corneal electrodes, we feel that under standardized conditions they are acceptable for most clinical recording situations in infants and young children.

  2. Porous graphite electrodes for rechargeable ion-transfer batteries

    Energy Technology Data Exchange (ETDEWEB)

    Novak, P.; Scheifele, W.; Haas, O. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The influence of preparation pressure and pore-forming additives on the properties of graphite-based, Li{sup +}-intercalating electrodes for ion-transfer batteries have been investigated. The electrochemical performance of graphite electrodes could be improved by adjusting the porosity. Specific charge of >300 Ah/kg (with respect to the graphite mass) could be achieved. (author) 4 figs., 2 refs.

  3. Development of nanoporous gold electrodes for electrochemical applications

    DEFF Research Database (Denmark)

    Quan, Xueling; Fischer, Lee MacKenzie; Boisen, Anja

    2011-01-01

    In this work we have used simple microfabrication techniques and chemical de-alloying of co-sputtered AgAu alloys to create nanoporous gold (np-Au) electrodes. The physical properties of the np-Au electrodes were investigated using scanning electron microscopy with energy dispersive X-ray analysi...

  4. Kinetic Studies on Ni-YSZ Composite Electrodes

    DEFF Research Database (Denmark)

    Njodzefon, Jean-Claude; Sudireddy, Bhaskar Reddy; Hjelm, Johan;

    2015-01-01

    AC and DC techniques were applied to investigate the electrochemical reaction kinetics of porous composite Ni/8-mol% yttria-stabilized zirconia (Ni/8YSZ) solid oxide cell (SOC) electrodes using a novel pseudo-3-electrode cell geometry. From OCV impedance spectra an activation energy Ea of 1.13 eV...

  5. A finite element analysis of the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in tDCS.

    Science.gov (United States)

    Faria, Paula; Hallett, Mark; Miranda, Pedro Cavaleiro

    2011-12-01

    We investigated the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in transcranial direct current stimulation (tDCS). For this purpose, we used the finite element method to compute the distribution of the current density in a four-layered spherical head model using various electrode montages, corresponding to a range of electrode sizes and inter-electrode distances. We found that smaller electrodes required slightly less current to achieve a constant value of the current density at a reference point on the brain surface located directly under the electrode center. Under these conditions, smaller electrodes also produced a more focal current density distribution in the brain, i.e. the magnitude of the current density fell more rapidly with distance from the reference point. The combination of two electrodes with different areas produced an asymmetric current distribution that could lead to more effective and localized neural modulation under the smaller electrode than under the larger one. Focality improved rapidly with decreasing electrode size when the larger electrode sizes were considered but the improvement was less marked for the smaller electrode sizes. Also, focality was not affected significantly by inter-electrode distance unless two large electrodes were placed close together. Increasing the inter-electrode distance resulted in decreased shunting of the current through the scalp and the cerebrospinal fluid, and decreasing electrode area resulted in increased current density on the scalp under the edges of the electrode. Our calculations suggest that when working with conventional electrodes (25-35 cm(2)), one of the electrodes should be placed just 'behind' the target relative to the other electrode, for maximum current density on the target. Also electrodes with areas in the range 3.5-12 cm(2) may provide a better compromise between focality and current density in the scalp than the traditional

  6. Submicron electrode gaps fabricated by gold electrodeposition at interdigitated electrodes

    NARCIS (Netherlands)

    Megen, M.J.J; Olthuis, W.; Berg, van den A.

    2014-01-01

    Electrodes with submicron gaps are desired for achieving high amplification redox cycling sensors. In this contribution we report the use of electrodeposition of gold in order to decrease the inter-electrode spacing at interdigitated electrodes. Using this method submicron spacings can be obtained w

  7. Dry EEG Electrodes

    Directory of Open Access Journals (Sweden)

    M. A. Lopez-Gordo

    2014-07-01

    Full Text Available Electroencephalography (EEG emerged in the second decade of the 20th century as a technique for recording the neurophysiological response. Since then, there has been little variation in the physical principles that sustain the signal acquisition probes, otherwise called electrodes. Currently, new advances in technology have brought new unexpected fields of applications apart from the clinical, for which new aspects such as usability and gel-free operation are first order priorities. Thanks to new advances in materials and integrated electronic systems technologies, a new generation of dry electrodes has been developed to fulfill the need. In this manuscript, we review current approaches to develop dry EEG electrodes for clinical and other applications, including information about measurement methods and evaluation reports. We conclude that, although a broad and non-homogeneous diversity of approaches has been evaluated without a consensus in procedures and methodology, their performances are not far from those obtained with wet electrodes, which are considered the gold standard, thus enabling the former to be a useful tool in a variety of novel applications.

  8. Single Electrode Heat Effects

    DEFF Research Database (Denmark)

    Jacobsen, Torben; Broers, G. H. J.

    1977-01-01

    for the oxygen electrode reaction is estimatedfrom thermodynamic data and reasonable agreement with the experimentalresults is found. It is concluded that the main contribution to the Peltierentropy arises from the transition from gaseous to liquid state, whereas thetransfer entropies of the ionic species...

  9. Measurement of electrode-tissue interface impedance for improvement of a transcutaneous data transmission using human body as transmission medium.

    Science.gov (United States)

    Okamoto, Eiji; Kato, Yoshikuni; Kikuchi, Sakiko; Mitamura, Yoshinori

    2014-01-01

    The electrical property between an electrode and skin or tissue is one of the important issues for communication performance of the transcutaneous communication system (TCS) using a human body as a conductive medium.In this study, we used a simple method to measure interface resistance between the electrode and skin on the surface of the body. The electrode-electrode impedance was measured by a commercially available LCR meter with changes in the distance between two electrodes on an arm of a healthy male subject, and we obtained the tissue resistivity and electrode-skin interface resistance using the cross-sectional area of the arm.We also measured transmission gain of the TCS on the surface of the body, and we investigated the relationship between electrode-skin interface resistance and transmission gain. We examined four kinds of electrodes: a stainless steel electrode, a titanium electrode, an Ag-AgCl electrode and an Ag-AgCl paste electrode. The stainless steel electrode, which had lower electrode-skin resistance, had higher transmission gain.The results indicate that an electrode that has lower electrode-skin resistance will contribute to improvement of the performance of the TCS and that electrode-skin interface resistance is one of valuable evaluation parameters for selecting an optimum electrode for the TCS.

  10. Ion-selective electrode reviews

    CERN Document Server

    Thomas, J D R

    1985-01-01

    Ion-Selective Electrode Reviews, Volume 7 is a collection of papers that covers the applications of electrochemical sensors, along with the versatility of ion-selective electrodes. The coverage of the text includes solid contact in membrane ion-selective electrodes; immobilized enzyme probes for determining inhibitors; potentiometric titrations based on ion-pair formation; and application of ion-selective electrodes in soil science, kinetics, and kinetic analysis. The text will be of great use to chemists and chemical engineers.

  11. Electroanalysis with carbon paste electrodes

    CERN Document Server

    Svancara, Ivan; Walcarius, Alain; Vytras, Karel

    2011-01-01

    Introduction to Electrochemistry and Electroanalysis with Carbon Paste-Based ElectrodesHistorical Survey and GlossaryField in Publication Activities and LiteratureCarbon Pastes and Carbon Paste ElectrodesCarbon Paste as the Binary MixtureClassification of Carbon Pastes and Carbon Paste ElectrodesConstruction of Carbon Paste HoldersCarbon Paste as the Electrode MaterialPhysicochemical Properties of Carbon PastesElectrochemical Characteristics of Carbon PastesTesting of Unmodified CPEsIntera

  12. Microtitrimetry by differential electrolytic potentiometry using metallic electrodes and nanomaterials modified metallic electrodes

    Science.gov (United States)

    Amro, Abdulaziz Nabil

    For the first time silver wire electrodes have been coated with carbon nanotubes using floating catalyst chemical vapor deposition (CVD) method. The production of CNTs has been conducted in a horizontal tubular reactor. Acetylene gas was used as a carbon source. Ferrocene has been used as a catalyst precursor for the growth of CNT. Different parameters have been optimized to get a high yield of CNTs and ensure their growth on the silver electrodes using univariate method. The parameters studied include the hydrogen flow rate, acetylene flow rate, temperature of the furnace, time of the reaction and the location of the electrodes in the reactor tube. The optimum conditions for those parameters were: for hydrogen and acetylene, the flow rates were 25 mL /min and 75 mL / min respectively. The furnace temperature was found to be 700 °C and the reaction time was 15 minutes. Regarding the location of the silver wires it should be located in the first 10 cm of the front side of the tube. Scanning electron microscopy (SEM) and transition electron microscopy (TEM) have been used to characterize carbon on silver electrodes. According to the experimental results, TEM figures show that CNT produced on Silver wire is multiwall carbon nanotubes MWCNT. Silver electrodes either pure or coated with CNT were used as indicating systems in micro titration using both dc differential electrolytic potentiometry (DEP) and mark-space bias DEP techniques. All types of titrimetric reactions were investigated using different types of electrodes like Pt and gold for oxidation reduction titrations, antimony electrodes for acid base titrations, silver electrodes for precipitation titrations in addition to Ag-CNT electrodes. End points at volumes of 1 microL were determined. Different parameters were optimized like the current density, the percentage bias, the volume of the sample and the concentrations of the reactants. Microtitrimetry has been applied on several types of analytes; Ferrous

  13. Interdigitated ring electrodes: Theory and experiment

    CERN Document Server

    Barnes, Edward O; Pozo-Ayuso, Diego F; Castaño-Alvarez, Mario; Lewis, Grace E M; Dale, Sara E C; Marken, Frank; Compton, Richard G

    2013-01-01

    The oxidation of potassium ferrocyanide, K_4Fe(CN)_6, in aqueous solution under fully supported conditions is carried out at interdigitated band and ring electrode arrays, and compared to theoretical models developed to simulate the processes. Simulated data is found to fit well with experimental results using literature values of diffusion coefficients for Fe(CN)_6^(4-) and Fe(CN)_6^(3-). The theoretical models are used to compare responses from interdigitated band and ring arrays, and the size of ring array required to approximate the response to a linear band array is investigated. An equation is developed for the radius of ring required for a pair of electrodes in a ring array to give a result with 5% of a pair of electrodes in a band array. This equation is found to be independent of the scan rate used over six orders of magnitude.

  14. AC Dielectrophoresis Using Elliptic Electrode Geometry

    Directory of Open Access Journals (Sweden)

    S. M. Rezaul Hasan

    2011-01-01

    Full Text Available This paper presents negative AC dielectrophoretic investigations using elliptic electrode geometry. Simulations of the electric field gradient variation using various ratios of the semimajor and the semiminor axis were carried out to determine the optimum elliptic geometry for the dielectrophoretic electrokinetics of specimen in an assay with laminar (low Reynolds number fluid flow. Experimental setup of the elliptic electrode assembly using PCB fabrication and electrokinetic accumulation of specimen in a dielectrophoretic cage is also being reported. Using an actuating signal between 1 kHz and 1 MHz, successful trapping of 45 μm polystyrene beads suspended in distilled water was demonstrated due to negative dielectrophoresis near 100 kHz using the novel elliptic electrode.

  15. Cleaved-edge-overgrowth nanogap electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Luber, Sebastian M; Bichler, Max; Abstreiter, Gerhard; Tornow, Marc, E-mail: m.tornow@tu-bs.de [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, 85748 Garching (Germany)

    2011-02-11

    We present a method to fabricate multiple metal nanogap electrodes of tailored width and distance in parallel, on the cleaved plane of a GaAs/AlGaAs heterostructure. The three-dimensional patterned structures are obtained by a combination of molecular-beam-epitaxial regrowth on a crystal facet, using the cleaved-edge-overgrowth (CEO) method, and subsequent wet selective etching and metallization steps. SEM and AFM studies reveal smooth and co-planar electrodes of width and distance of the order of 10 nm. Preliminary electrical characterization indicates electrical gap insulation in the 100 M{Omega} range with k{Omega} lead resistance. We propose our methodology to realize multiple electrode geometries that would allow investigation of the electrical conductivity of complex nanoscale objects such as branched organic molecules.

  16. Electroformed Electrodes for Electrical-Discharge Machining

    Science.gov (United States)

    Werner, A.; Cassidenti, M.

    1984-01-01

    Copper electrodes replace graphite electrodes in many instances of electrical-discharge machining (EDM) of complex shapes. Copper electrodes wear longer and cause less contamination of EDM dielectric fluid than do graphite electrodes.

  17. Electrode Kinetics and Gas Conversion in Solid Oxide Cells

    DEFF Research Database (Denmark)

    Njodzefon, Jean-Claude

    for operation in the different fuels, operation temperature and operation modes it is important to understand the kinetics of the SOC electrodes. This thesis was aimed at understanding the kinetics of the SOC under different operation conditions of temperature, polarization, and fuel mixture. For investigations...... conditions of temperature and current density nano particles were also found on Ni particles, identified as ZrO2 and attributed the major cause of fuel electrode ageing. In cyclic operation these enhancing conditions were not maintained long-enough for severe nickel precipitation. It is known...... compared well with those reported in literature and their evolution with temperature was similar to that reported in literature based on porous Ni/YSZ fuel electrodes. From the two investigated oxygen electrodes, the higher performing (La0.6Sr0.4)0.99CoO3/Ce0.9Gd0.1O1.95 (LSC/CGO) oxygen electrode showed...

  18. Nanoscale biomemory composed of recombinant azurin on a nanogap electrode.

    Science.gov (United States)

    Chung, Yong-Ho; Lee, Taek; Park, Hyung Ju; Yun, Wan Soo; Min, Junhong; Choi, Jeong-Woo

    2013-09-13

    We fabricate a nanoscale biomemory device composed of recombinant azurin on nanogap electrodes. For this, size-controllable nanogap electrodes are fabricated by photolithography, electron beam lithography, and surface catalyzed chemical deposition. Moreover, we investigate the effect of gap distance to optimize the size of electrodes for a biomemory device and explore the mechanism of electron transfer from immobilized protein to a nanogap counter-electrode. As the distance of the nanogap electrode is decreased in the nanoscale, the absolute current intensity decreases according to the distance decrement between the electrodes due to direct electron transfer, in contrast with the diffusion phenomenon of a micro-electrode. The biomemory function is achieved on the optimized nanogap electrode. These results demonstrate that the fabricated nanodevice composed of a nanogap electrode and biomaterials provides various advantages such as quantitative control of signals and exclusion of environmental effects such as noise. The proposed bioelectronics device, which could be mass-produced easily, could be applied to construct a nanoscale bioelectronics system composed of a single biomolecule.

  19. Electrical characteristic of the titanium mesh electrode for transcutaneous intrabody communication to monitor implantable artificial organs.

    Science.gov (United States)

    Okamoto, Eiji; Kikuchi, Sakiko; Mitamura, Yoshinori

    2016-09-01

    We have developed a tissue-inducing electrode using titanium mesh to obtain mechanically and electrically stable contact with the tissue for a new transcutaneous communication system using the human body as a conductive medium. In this study, we investigated the electrical properties of the titanium mesh electrode by measuring electrode-tissue interface resistance in vivo. The titanium mesh electrode (Hi-Lex Co., Zellez, Hyogo, Japan) consisted of titanium fibers (diameter of 50 μm), and it has an average pore size of 200 μm and 87 % porosity. The titanium mesh electrode has a diameter of 5 mm and thickness of 1.5 mm. Three titanium mesh electrodes were implanted separately into the dorsal region of the rat. We measured the electrode-electrode impedance using an LCR meter for 12 weeks, and we calculated the tissue resistivity and electrode-tissue interface resistance. The electrode-tissue interface resistance of the titanium mesh electrode decreased slightly until the third POD and then continuously increased to 75 Ω. The electrode-tissue interface resistance of the titanium mesh electrode is stable and it has lower electrode-tissue interface resistance than that of a titanium disk electrode. The extracted titanium mesh electrode after 12 weeks implantation was fixed in 10 % buffered formalin solution and stained with hematoxylin-eosin. Light microscopic observation showed that the titanium mesh electrode was filled with connective tissue, inflammatory cells and fibroblasts with some capillaries in the pores of the titanium mesh. The results indicate that the titanium mesh electrode is a promising electrode for the new transcutaneous communication system.

  20. Investigation on Electrochemical Behavior of Interaction between Salvianolic Acid B and Bovine Serum Albumin at DNA Modified Electrode%丹酚酸B与牛血清白蛋白相互作用的电化学研究

    Institute of Scientific and Technical Information of China (English)

    王月荣; 刘馥婷; 章弘扬; 张敏; 胡坪

    2012-01-01

    在0.01 mol·L-1磷酸盐缓冲溶液(pH 7.4)中,用循环伏安法和方波伏安法研究了丹酚酸B与牛血清白蛋白相互作用前后在DNA修饰玻碳电极上的电化学行为.实验表明,丹酚酸B在此修饰电极上于0.100 V处产生良好的氧化峰,加入牛血清白蛋白后,丹酚酸B的电子转移系数α和表观电子传递速率常数ks均发生了变化,氧化峰电位正移,峰电流减小.根据氧化电流的变化求得丹酚酸B和牛血清白蛋白相互作用的结合常数β=1.00×108L·mol-1,结合数m=1.71,表明丹酚酸B与牛血清白蛋白生成了结合比约为2:1的非电活性复合物.该结果与荧光光谱法的研究结果一致.%The electrochemical behavior of interaction between salvianolic acid B ( SalB) and bovine serum album in ( BSA) was investigated by cyclic voltammetry and square wave voltammetry based on DNA-modified glass carbon electrode (GCE) in 0.01 mol/L phosphate buffer solution ( pH 7.4). SalB generated a sensitive oxidation peak of 0. 100 V at the DNA-modified GCE. After addition of BSA into the SalB solution, the oxidation current decreased and the peak potential shifted positively. The electrochemical parameters, such as the charge-transfer coefficient a and the standard electron-transfer rate constant ks were also changed. The binding number m of 1. 71 and the binding constant β of 1. 00 x 10 L/mol were calculated according to the data of the oxidation current, which indicated that SalB could combine with BSA to generate a non-electric complexes with combination ratio of 2 : 1. The results were in agreement with that provided by the fluorescence spectrometric method.

  1. Electrode models in electrical impedance tomography

    Institute of Scientific and Technical Information of China (English)

    WANG M.

    2005-01-01

    This paper presents different views on electrode modelling, which include electrode electrochemistry models for modelling the effects of electrode-electrolyte interface, electric field electrode models for modelling electrode geometry, and electrode models for modelling the effects of electrode common mode voltage and double layer capacitance. Taking the full electrode models into consideration .in electrical impedance tomography (EIT) will greatly help the optimised approach to a good solution and further understanding of the measurement principle.

  2. Ion-selective electrode reviews

    CERN Document Server

    Thomas, J D R

    1983-01-01

    Ion-Selective Electrode Reviews, Volume 5 is a collection of articles that covers ion-speciation. The book aims to present the advancements of the range and capabilities of selective ion-sensors. The topics covered in the selection are neutral carrier based ion-selective electrodes; reference electrodes and liquid junction effects in ion-selective electrode potentiometry; ion transfer across water/organic phase boundaries and analytical; and carbon substrate ion-selective electrodes. The text will be of great use to chemists and chemical engineers.

  3. Magnetohydrodynamic generator electrode

    Science.gov (United States)

    Marchant, David D.; Killpatrick, Don H.; Herman, Harold; Kuczen, Kenneth D.

    1979-01-01

    An improved electrode for use as a current collector in the channel of a magnetohydrodynamid (MHD) generator utilizes an elongated monolithic cap of dense refractory material compliantly mounted to the MHD channel frame for collecting the current. The cap has a central longitudinal channel which contains a first layer of porous refractory ceramic as a high-temperature current leadout from the cap and a second layer of resilient wire mesh in contact with the first layer as a low-temperature current leadout between the first layer and the frame. Also described is a monolithic ceramic insulator compliantly mounted to the frame parallel to the electrode by a plurality of flexible metal strips.

  4. Composite electrodes for lithium batteries.

    Energy Technology Data Exchange (ETDEWEB)

    Hackney, S. A.; Johnson, C. S.; Kahaian, A. J.; Kepler, K. D.; Shao-Horn, Y.; Thackeray, M. M.; Vaughey, J. T.

    1999-02-03

    The stability of composite positive and negative electrodes for rechargeable lithium batteries is discussed. Positive electrodes with spinel-type structures that are derived from orthorhombic-LiMnO{sub 2} and layered-MnO{sub 2} are significantly more stable than standard spinel Li[Mn{sub 2}]O{sub 4} electrodes when cycled electrochemically over both the 4-V and 3-V plateaus in lithium cells. Transmission electron microscope data of cycled electrodes have indicated that a composite domain structure accounts for this greater electrochemical stability. The performance of composite Cu{sub x}Sn materials as alternative negative electrodes to amorphous SnO{sub x} electrodes for lithium-ion batteries is discussed in terms of the importance of the concentration of the electrochemically inactive copper component in the electrode.

  5. Comparative investigation of unipolar resistance switching effect of Pt/Mg{sub 0.6}Zn{sub 0.4}O/Pt devices with different electrode patterns for nonvolatile memory application

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xinman [South China Normal University, Institute of Optoelectronic Materials and Technology, Guangzhou (China); Sun Yat-Sen University, State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Guangzhou (China); Wu, Guangheng; Hu, Wei; Zhou, Hong; Bao, Dinghua [Sun Yat-Sen University, State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Guangzhou (China)

    2012-08-15

    Electrically induced unipolar resistance switching effects of Mg{sub 0.6}Zn{sub 0.4}O thin films with two top Pt electrodes (MZO-T) and top and bottom Pt electrodes (MZO-B) were demonstrated and compared for nonvolatile memory applications. The obtained resistance ratios of high-resistance states (HRS) to low-resistance states (LRS) for MZO-B and MZO-T devices were above seven and four orders of magnitude, respectively, and exhibited a slight degradation with voltage. For both the devices, the conduction mechanisms were dominated by ohmic conduction in LRS and trap-controlled space charge limited current in HRS. Furthermore, a filamentary model was applied to explain the switching behaviors for both the devices considering the asymmetric interface defects and film thickness. The results also suggest that resistance switching behaviors can be regulated by interface defect engineering. (orig.)

  6. Poly-Alizarin red S/multiwalled carbon nanotube modified glassy carbon electrode for the boost up of electrocatalytic activity towards the investigation of dopamine and simultaneous resolution in the presence of 5-HT: A voltammetric study

    Energy Technology Data Exchange (ETDEWEB)

    Reddaiah, K. [Electrochemical Research Laboratory, Department of Chemistry, S.V.U. College of Sciences, Sri Venkateswara University, Tirupati 517 502, Andhra Pradesh (India); Madhusudana Reddy, T., E-mail: tmsreddysvu@gmail.com [Electrochemical Research Laboratory, Department of Chemistry, S.V.U. College of Sciences, Sri Venkateswara University, Tirupati 517 502, Andhra Pradesh (India); Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455 (United States); Venkata Ramana, D.K. [Department of Safety Engineering, Dongguk University, 123 Dongdae-ro, Gyeongju, Gyeongbuk 780 714 (Korea, Republic of); Subba Rao, Y. [DST-PURSE Centre, Sri Venkateswara University, Tirupati 517502, Andhra Pradesh (India)

    2016-05-01

    Poly-Alizarin red S/multiwalled carbon nanotube film on the surface of glassy carbon electrode (poly-AzrS/MWCNT/GCE) was synthesized by electrochemical process and was used for the sensitive and selective determination of dopamine (DA) by employing voltammetric techniques. The electrocatalytic response of the modified electrode was found to exhibit admirable activity. The simultaneous determination of dopamine in the presence of serotonin (5-HT) was found to exhibit very good response at poly-AzrS/MWCNTs/GCE. The effect of pH, scan rate, accumulation time and concentration of dopamine was studied at the developed poly-AzrS/MWCNTs/GCE. The poly-AzrS/MWCNTs/GCE exhibited an efficient electron mediating behavior together with well resolved peaks for dopamine, in 0.1 mol/dm{sup 3} phosphate buffer (PBS) solution of pH 7.0. The limit of detection (LOD) and limit of quantification (LOQ) were found to be as 1.89 × 10{sup −7} mol/dm{sup 3} and 6.312 × 10{sup −7} mol/dm{sup 3} respectively with a dynamic range from 1 × 10{sup −6} to 1.8 × 10{sup −5} mol/dm{sup 3}. The interfacial electron transfer behavior of DA was studied by electrochemical impedance spectroscopy (EIS); the studies showed that the charge transfer rate was enhanced at poly-AzrS/MWCNTs/GCE when compared with bare GCE and poly-AzrS/GCE. - Highlights: • The poly-AzrS/MWCNTs/GCE showed good sensitivity towards DA sensing. • The sensor reduced the overoxidation potentials for DA. • This electrode was successfully used for simultaneous sensing of DA and 5-HT. • The electrode was effectively used for the determination of DA in pharmaceutical formulations.

  7. Investigation of mediated oxidation of ascorbic acid by ferrocenemethanol using large-amplitude Fourier transformed ac voltammetry under quasi-reversible electron-transfer conditions at an indium tin oxide electrode.

    Science.gov (United States)

    Lertanantawong, Benchaporn; O'Mullane, Anthony P; Zhang, Jie; Surareungchai, Werasak; Somasundrum, Mithran; Bond, Alan M

    2008-09-01

    The ability of the technique of large-amplitude Fourier transformed (FT) ac voltammetry to facilitate the quantitative evaluation of electrode processes involving electron transfer and catalytically coupled chemical reactions has been evaluated. Predictions derived on the basis of detailed simulations imply that the rate of electron transfer is crucial, as confirmed by studies on the ferrocenemethanol (FcMeOH)-mediated electrocatalytic oxidation of ascorbic acid. Thus, at glassy carbon, gold, and boron-doped diamond electrodes, the introduction of the coupled electrocatalytic reaction, while producing significantly enhanced dc currents, does not affect the ac harmonics. This outcome is as expected if the FcMeOH (0/+) process remains fully reversible in the presence of ascorbic acid. In contrast, the ac harmonic components available from FT-ac voltammetry are predicted to be highly sensitive to the homogeneous kinetics when an electrocatalytic reaction is coupled to a quasi-reversible electron-transfer process. The required quasi-reversible scenario is available at an indium tin oxide electrode. Consequently, reversible potential, heterogeneous charge-transfer rate constant, and charge-transfer coefficient values of 0.19 V vs Ag/AgCl, 0.006 cm s (-1) and 0.55, respectively, along with a second-order homogeneous chemical rate constant of 2500 M (-1) s (-1) for the rate-determining step in the catalytic reaction were determined by comparison of simulated responses and experimental voltammograms derived from the dc and first to fourth ac harmonic components generated at an indium tin oxide electrode. The theoretical concepts derived for large-amplitude FT ac voltammetry are believed to be applicable to a wide range of important solution-based mediated electrocatalytic reactions.

  8. Nano-scale Electrodes for Molecular/Organic Electronics

    Institute of Scientific and Technical Information of China (English)

    K.Tsukagoshi

    2007-01-01

    1 Results Nanometer-scale electrodes with a nano-junction allow us to investigate conduction properties of nano-materials. Because many nano-materials usually form grain boundaries or domain boundaries with high tunneling resistance, it is difficult to investigate the intrinsic properties through a series of tunneling resistance. To make direct contact with the single nano-material, such as a single polymer string, we developed nano-scale electrodes. By using these nano-electrodes as new tool, we invest...

  9. The effect of different electrodes on the electronic transmission of benzene junctions: Analytical approach

    Energy Technology Data Exchange (ETDEWEB)

    Mohebbi, Razie; Seyed-Yazdi, Jamileh, E-mail: j.seyedyazdi@vru.ac.ir

    2016-06-01

    In this paper we have investigated the electronic transmission of systems electrode–benzene–electrode using the Landauer approach. The effect of different electrodes made of metal (Au) and semiconductors (Si, TiO{sub 2}) is investigated. These three electrodes are compared between them and the results show that the electronic transmission of benzene junctions, when using semiconductor electrodes, is associated to a gap in transmission which is due to the electrodes band gap. As a consequence, a threshold voltage is necessary to obtain conducting channels.

  10. Measurements of Plasma Potential Distribution in Segmented Electrode Hall Thruster

    Energy Technology Data Exchange (ETDEWEB)

    Y. Raitses; D. Staack; N.J. Fisch

    2001-10-16

    Use of a segmented electrode placed at the Hall thruster exit can substantially reduce the voltage potential drop in the fringing magnetic field outside the thruster channel. In this paper, we investigate the dependence of this effect on thruster operating conditions and segmented electrode configuration. A fast movable emissive probe is used to measure plasma potential in a 1 kW laboratory Hall thruster with semented electrodes made of a graphite material. Relatively small probe-induced perturbations of the thruster discharge in the vicinity of the thruster exit allow a reasonable comparison of the measured results for different thruster configurations. It is shown that the plasma potential distribution is almost not sensitive to changes of the electrode potential, but depends on the magnetic field distribution and the electrode placement.

  11. New doped tin dioxide electrodes for electrochemical ozone generation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y.H.; Li, G.; Liang, Y.R.; Nie, Z.Z.; Chen, Q.Y. [Xi' an Jiaotong Univ., Xi' an (China). State Key Laboratory of Multiphase Flow, Dept. of Environmental Engineering

    2010-07-01

    In this study, nickel (Ni) and antimony (Sb) doped tin dioxide (SnO{sub 2}) were prepared using a dip-coating pyrolysis method. The sol-gel dip coating method was used to prepare the Ni-Sb-SnO{sub 2} electrode. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses were conducted to compare the morphology, crystallinity, composition and oxidation states achieved using the 2 different preparation methods. Results of the evaluation showed that electrodes prepared by the sol-gel method were much different than those prepared using the dip-coating pyrolysis method. Silver (Ag) and cerium (Ce) were doped onto the Ni and Sb doped SnO{sub 2}, and the relations between electrode properties and performance were investigated. Results demonstrated that Ag and Ce doping significantly improved electrode performance. The sol-gel dip coating method also significantly improved electrode performance. 2 refs., 1 fig.

  12. Nanostructured gold and platinum electrodes on silicon structures for biosensing

    Science.gov (United States)

    Ogurtsov, V. I.; Sheehan, M. M.

    2005-01-01

    Gold and platinum metal electrodes on Si/SiO2 having undergone anisotropic potassium hydroxide (KOH) etch treatment are considered. This treatment etches at different rates and directions in the material resulting in creation of numerous pyramid shaped holes in the silicon substrate. This surface is used to make metal electrodes with increased electrode efficiency. The electrodes can serve as the sensors or as the sensor substrates (for surface polymer modification) and because both gold and platinum are inert they have applications for food safety biosensing. Wine, an economically significant food product, was chosen as a matrix, and impedance spectroscopy (EIS) was selected as a method of investigation of electrode behaviour. Based on results of EIS, different complexity equivalent circuits were determined by applying fitting mean square root optimisation of sensor complex impedance measurements.

  13. A Reliable Reference Electrode in Molten Carbonate and Its Applications

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A Ag|AgCl reference electrode which can be used in molten carbonate media has been described in this paper.It consists of a silver wire immersed in a solution of AgCl(1mol%) in (Li0.62,K0.38)2CO3,with a zirconia junction.The main properties of reference electrode,such as reproducibility ,stability and reversibility, were checked.The results have demonstrated that the reference electrode is reliable.With such reference electrode catalysis of various electrode materials to oxygen reduction in molten alkali carbonate media was investigated.It is found that as catalysts for oxygen reduction oxidized nickel-niobium alloy is superior to nickel oxide.

  14. Accuracy of Plantar Electrodes Compared with Hand and Foot Electrodes in Fat-free-mass Measurement

    Directory of Open Access Journals (Sweden)

    Michel Y. Jaffrin

    2014-01-01

    Full Text Available This paper investigates the measurement of fat-free mass (FFM by bioimpedance using foot-to-foot impedancemeters (FFI with plantar electrodes measuring the foot-to-foot resistance R34 and hand-to-foot medical impedancemeters. FFM measurements were compared with corresponding data using Dual X-ray absorptiometry (DXA. Equations giving FFM were established using linear multiple regression on DXA data in a first group of 170 subjects. For validation, these equations were used on a second group of 86 subjects, and FFM were compared with DXA data; no significant difference was observed. The same protocol was repeated, but using electrodes on the right hand and foot in standing position to measure the hand to-foot resistance R13. Mean differences with DXA were higher for R13 than for R34. Effect of electrode size and feet position on resistance was also investigated. R34 decreased when electrode area increased or if feet were moved forward. It decreased if feet were moved backward. A proper configuration of contact electrodes can improve measurement accuracy and reproducibility of FFI.

  15. Gas sensor with multiple internal reference electrodes and sensing electrodes

    DEFF Research Database (Denmark)

    2016-01-01

    The invention relates to a potentiometric gas sensor, or potentiometric gas detection element, with multiple internal reference electrodes and multiple sensing electrodes for determining the concentrations of gas components in a gaseous mixture. The sensor for gas detection comprises: a solid...... electrolyte, at least two sensing electrodes (SEs) in solid contact with the electrolyte, and at least two internal reference electrodes (IREs) in solid contact with the electrolyte, wherein each IRE comprises a composite material, comprising a binary mixture of a metal and a metal oxide dispersed to form...

  16. Chronic impedance spectroscopy of an endovascular stent-electrode array

    Science.gov (United States)

    Opie, Nicholas L.; John, Sam E.; Rind, Gil S.; Ronayne, Stephen M.; Grayden, David B.; Burkitt, Anthony N.; May, Clive N.; O'Brien, Terence J.; Oxley, Thomas J.

    2016-08-01

    Objective. Recently, we reported a minimally invasive stent-electrode array capable of recording neural signals from within a blood vessel. We now investigate the use of electrochemical impedance spectroscopy (EIS) measurements to infer changes occurring to the electrode-tissue interface from devices implanted in a cohort of sheep for up to 190 days. Approach. In a cohort of 15 sheep, endovascular stent-electrode arrays were implanted in the superior sagittal sinus overlying the motor cortex for up to 190 days. EIS was performed routinely to quantify viable electrodes for up to 91 days. An equivalent circuit model (ECM) was developed from the in vivo measurements to characterize the electrode-tissue interface changes occurring to the electrodes chronically implanted within a blood vessel. Post-mortem histological assessment of stent and electrode incorporation into the wall of the cortical vessels was compared to the electrical impedance measurements. Main results. EIS could be used to infer electrode viability and was consistent with x-ray analysis performed in vivo, and post-mortem evaluation. Viable electrodes exhibited consistent 1 kHz impedances across the 91 day measurement period, with the peak resistance frequency for the acquired data also stable over time. There was a significant change in 100 Hz phase angles, increasing from -67.8° ± 8.8° at day 0 to -43.8° ± 0.8° at day 91, which was observed to stabilize after eight days. ECM’s modeled to the data suggested this change was due to an increase in the capacitance of the electrode-tissue interface. This was supported by histological assessment with >85% of the implanted stent struts covered with neointima and incorporated into the blood vessel within two weeks. Conclusion. This work demonstrated that EIS could be used to determine the viability of electrode implanted chronically within a blood vessel. Impedance measurements alone were not observed to be a useful predictor of alterations occurring

  17. Gold electrodes from recordable CDs

    Science.gov (United States)

    Angnes; Richter; Augelli; Kume

    2000-11-01

    Gold electrodes are widely used in electrochemistry and electroanalytical chemistry. The notable performance when used in stripping analysis of many ionic species and the extraordinary affinity of thio compounds for its surface make these electrodes very suitable for many applications. This paper reports a simple and novel way to construct gold electrodes (CDtrodes) using recordable CDs as the gold source. The nanometer thickness of the gold layer of recordable disks (50-100 nm) favors the construction of band nanoelectrodes with areas as small as 10(-6) cm2. The plane surface can be easily used for the construction of conventional-sized gold electrodes for batch or flow injection analysis or even to obtain electrodes as large as 100 cm2. The low price of commercial recordable CDs allows a "one way use". The evaluation and applicability of these electrodes in the form of nanoelectrodes, in batch and associated with flow cells, are illustrated in this paper.

  18. Continuous Separation of Cesium Based on NiHCF/PTCF Electrode by Electrochemically Switched Ion Exchange

    Institute of Scientific and Technical Information of China (English)

    孙斌; 郝晓刚; 王忠德; 张忠林; 刘世斌; 官国清

    2012-01-01

    Nickel hexacyanoferrate (NiHCF) film was synthesized on porous three-dimensional carbon felt (PTCF) substrate by repetitious batch chemical depositions, and the NiHCF/PTCF electrode was used as electrochemically switched ion exchange (ESIX) electrode in a packed bed for continuous separation for cesium ions. The morphologies of the prepared electrodes were characterized by scanning electron microscopy and the effects of solution concentration on the ion-exchange capacity of the electrodes were investigated by cyclic voltammetry technique. Cycling stability and long-term storage stability of NiHCF/PTCF electrodes were also studied. The NiHCF/PTCF electrodes with excellent ion-exchange ability were used to assemble a diaphragm-isolated ESIX reactor for cesium separation. Continuous separation of cesium and regeneration of NiHCF/PTCF electrode based on the diaphragm-isolated reactor were performed in a laboratory-scale two-electrode system.

  19. Characterization of Transition-Metal Oxide Deposition on Carbon Electrodes of a Supercapacitor

    Directory of Open Access Journals (Sweden)

    Ying-Chung Chen

    2016-12-01

    Full Text Available In order to fabricate the composite electrodes of a supercapacitor, transition-metal oxide materials NiO and WO3 were deposited on carbon electrodes by electron beam evaporation. The influences of various transition-metal oxides, scan rates of cyclic voltammograms (CVs, and galvanostatic charge/discharge tests on the characteristics of supercapacitor were studied. The charge/discharge efficiency and the lifetime of the composite electrodes were also investigated. It was found that the composite electrodes exhibited more favorable capacitance properties than those of the carbon electrodes at high scan rates. The results revealed the promotion of the capacitance property of the supercapacitor with composite electrode and the improving of the decay property in capacitance at high scan rate. In addition, the charge/discharge efficiency is close to 100% after 5000 cycles, and the composite electrode retains strong adhesion between the electrode material and the substrate.

  20. Boron-Doped Nanocrystalline Diamond Electrodes for Neural Interfaces: In vivo Biocompatibility Evaluation.

    Science.gov (United States)

    Alcaide, María; Taylor, Andrew; Fjorback, Morten; Zachar, Vladimir; Pennisi, Cristian P

    2016-01-01

    Boron-doped nanocrystalline diamond (BDD) electrodes have recently attracted attention as materials for neural electrodes due to their superior physical and electrochemical properties, however their biocompatibility remains largely unexplored. In this work, we aim to investigate the in vivo biocompatibility of BDD electrodes in relation to conventional titanium nitride (TiN) electrodes using a rat subcutaneous implantation model. High quality BDD films were synthesized on electrodes intended for use as an implantable neurostimulation device. After implantation for 2 and 4 weeks, tissue sections adjacent to the electrodes were obtained for histological analysis. Both types of implants were contained in a thin fibrous encapsulation layer, the thickness of which decreased with time. Although the level of neovascularization around the implants was similar, BDD electrodes elicited significantly thinner fibrous capsules and a milder inflammatory reaction at both time points. These results suggest that BDD films may constitute an appropriate material to support stable performance of implantable neural electrodes over time.

  1. Fabrication of a three-electrode battery using hydrogen-storage materials

    Science.gov (United States)

    Roh, Chi-Woo; Seo, Jung-Yong; Moon, Hyung-Seok; Park, Hyun-Young; Nam, Na-Yun; Cho, Sung Min; Yoo, Pil J.; Chung, Chan-Hwa

    2015-04-01

    In this study, an energy storage device using a three-electrode battery is fabricated. The charging process takes place during electrolysis of the alkaline electrolyte where hydrogen is stored at the palladium bifunctional electrode. Upon discharging, power is generated by operating the alkaline fuel cell using hydrogen which is accumulated in the palladium hydride bifunctional electrode during the charging process. The bifunctional palladium electrode is prepared by electrodeposition using a hydrogen bubble template followed by a galvanic displacement reaction of platinum in order to functionalize the electrode to work not only as a hydrogen storage material but also as an anode in a fuel cell. This bifunctional electrode has a sufficiently high surface area and the platinum catalyst populates at the surface of electrode to operate the fuel cell. The charging and discharging performance of the three-electrode battery are characterized. In addition, the cycle stability is investigated.

  2. Electrodynamic Arrays Having Nanomaterial Electrodes

    Science.gov (United States)

    Trigwell, Steven (Inventor); Biris, Alexandru S. (Inventor); Calle, Carlos I. (Inventor)

    2013-01-01

    An electrodynamic array of conductive nanomaterial electrodes and a method of making such an electrodynamic array. In one embodiment, a liquid solution containing nanomaterials is deposited as an array of conductive electrodes on a substrate, including rigid or flexible substrates such as fabrics, and opaque or transparent substrates. The nanomaterial electrodes may also be grown in situ. The nanomaterials may include carbon nanomaterials, other organic or inorganic nanomaterials or mixtures.

  3. Jointed Holder For Welding Electrodes

    Science.gov (United States)

    Gilbert, Jeffrey L.

    1991-01-01

    Adjustable-angle holder enables use of standard straight electrode with custom-fabricated bent gas cup for welding in difficult-to-reach places. Electrode replaced easily, without removing cup, with aid of tool loosening miniature collet nut on holder. Consumes fewer electrodes for given amount of welding. Angle of holder continuously adjustable to fit angle of gas cup or geometry of part welded. Holder made double-jointed to accommodate gas cup having compound angles.

  4. Coated carbon nanotube array electrodes

    Science.gov (United States)

    Ren, Zhifeng; Wen, Jian; Chen, Jinghua; Huang, Zhongping; Wang, Dezhi

    2008-10-28

    The present invention provides conductive carbon nanotube (CNT) electrode materials comprising aligned CNT substrates coated with an electrically conducting polymer, and the fabrication of electrodes for use in high performance electrical energy storage devices. In particular, the present invention provides conductive CNTs electrode material whose electrical properties render them especially suitable for use in high efficiency rechargeable batteries. The present invention also provides methods for obtaining surface modified conductive CNT electrode materials comprising an array of individual linear, aligned CNTs having a uniform surface coating of an electrically conductive polymer such as polypyrrole, and their use in electrical energy storage devices.

  5. Ion-selective electrode reviews

    CERN Document Server

    Thomas, J D R

    1982-01-01

    Ion-Selective Electrode Reviews, Volume 3, provides a review of articles on ion-selective electrodes (ISEs). The volume begins with an article on methods based on titration procedures for surfactant analysis, which have been developed for discrete batch operation and for continuous AutoAnalyser use. Separate chapters deal with detection limits of ion-selective electrodes; the possibility of using inorganic ion-exchange materials as ion-sensors; and the effect of solvent on potentials of cells with ion-selective electrodes. Also included is a chapter on advances in calibration procedures, the d

  6. Electrodes for Semiconductor Gas Sensors.

    Science.gov (United States)

    Lee, Sung Pil

    2017-03-25

    The electrodes of semiconductor gas sensors are important in characterizing sensors based on their sensitivity, selectivity, reversibility, response time, and long-term stability. The types and materials of electrodes used for semiconductor gas sensors are analyzed. In addition, the effect of interfacial zones and surface states of electrode-semiconductor interfaces on their characteristics is studied. This study describes that the gas interaction mechanism of the electrode-semiconductor interfaces should take into account the interfacial zone, surface states, image force, and tunneling effect.

  7. Nickel hydroxide modified electrodes for urea determination

    Directory of Open Access Journals (Sweden)

    Luiz Henrique Dall´Antonia

    2007-03-01

    Full Text Available Nickel hydroxide films were prepared by electrodeposition from a solution Ni(NO32 0,05 mol L ?¹ on ITO electrodes (Tin oxide doped with Indium on PET-like plastic film, applying a current of - 0,1 A cm ?² during different time intervals between 1800 and 7200 s. The electrochemical behavior of the nickel hydroxide electrode was investigated through a cyclic voltammogram, in NaOH 1,0 mol L ?¹, where it was observed two peaks in the profile in 0,410 and 0,280 V, corresponding to redox couple Ni(II/Ni(III. A sensor for urea presenting a satisfactory answer can be obtained when, after the deposit of the film of Ni(OH2 on the electrode of nickel, it is immersed in a solution of NaOH 1,0 mol L ?¹ and applying a potential of + 0,435 V, where the maximum of the anodic current occurs in the cyclic voltammogram. Analyzing the results it can be observed that, for a range of analite concentration between 5 to 50 m mol L ?¹, the behavior is linear and the sensibility found was of 20,3 mA cm?² (mol L?¹?¹, presenting reproducibility confirming the nickel hydroxide electrodes utilization for the determination of urea.

  8. Investigation of Underpotential Deposition of Lead on Rotating Silver Disk Electrode by Chronocoulometry%铅于旋转银盘电极上欠电位沉积的计时库仑法研究

    Institute of Scientific and Technical Information of China (English)

    王春明; 包永军; 杜永令

    2001-01-01

    用计时库仑法研究了Pb2+于旋转Ag盘电极(Ag-RDE)上的欠电位沉积(UPD)性质。实验证明,支持电解质(0.01 mol/LHN03+0.01 mol/L NaCl)中Cl-离子的存在有利于取得稳态条件下UPD-Pb的电量值。其氧化过程电量(Qa),代表Pb2+吸附单层被定量转化为UPD Pb单层的量,Qa的平均值为393.3μC/cm2,相应于2×10-9 mol/cm2 Pb2+表面复盖量。%The monolayer charge of lead underpotential deposition (UPD) was studied by chronocoulometry. On the rotating silver disk electrode (Ag-RDE), the monolayer charge of UPD lead could reaches steady state at different Pb2+ concentration levels by changing reduction time of UPD Pb2+ . A supporting electrolyte solution of 0.01 mol/L HNO3 + 0.01 mol/L NaCl was used. The steady state charge measured was 393.3 μC/cm2, which corresponded to a surface cover of 2 × 10-9 mol/cm2 Pb2+ on the electrode surface.

  9. Poly-Alizarin red S/multiwalled carbon nanotube modified glassy carbon electrode for the boost up of electrocatalytic activity towards the investigation of dopamine and simultaneous resolution in the presence of 5-HT: A voltammetric study.

    Science.gov (United States)

    Reddaiah, K; Madhusudana Reddy, T; Venkata Ramana, D K; Subba Rao, Y

    2016-05-01

    Poly-Alizarin red S/multiwalled carbon nanotube film on the surface of glassy carbon electrode (poly-AzrS/MWCNT/GCE) was synthesized by electrochemical process and was used for the sensitive and selective determination of dopamine (DA) by employing voltammetric techniques. The electrocatalytic response of the modified electrode was found to exhibit admirable activity. The simultaneous determination of dopamine in the presence of serotonin (5-HT) was found to exhibit very good response at poly-AzrS/MWCNTs/GCE. The effect of pH, scan rate, accumulation time and concentration of dopamine was studied at the developed poly-AzrS/MWCNTs/GCE. The poly-AzrS/MWCNTs/GCE exhibited an efficient electron mediating behavior together with well resolved peaks for dopamine, in 0.1 mol/dm(3) phosphate buffer (PBS) solution of pH 7.0. The limit of detection (LOD) and limit of quantification (LOQ) were found to be as 1.89 × 10(-7) mol/dm(3) and 6.312 × 10(-7) mol/dm(3) respectively with a dynamic range from 1 × 10(-6) to 1.8 × 10(-5) mol/dm(3). The interfacial electron transfer behavior of DA was studied by electrochemical impedance spectroscopy (EIS); the studies showed that the charge transfer rate was enhanced at poly-AzrS/MWCNTs/GCE when compared with bare GCE and poly-AzrS/GCE.

  10. Understanding Periodic Dislocations in 2D Supramolecular Crystals: The PFP/Ag(111) Interface

    DEFF Research Database (Denmark)

    Goiri, E.; García Lastra, Juan Maria; Corso, M.;

    2012-01-01

    In-plane dislocation networks arise in both inorganic and organic films as a way of relieving the elastic strain that builds up at the substrate interface. In molecule/surface systems, supramolecular interactions are weak and more complex (compared to the atomic bonds in inorganic films), and the...

  11. PTCDA induced faceting of a vicinal Ag(111) surface: an in-situ LEEM study

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Thomas; Marchetto, Helder; Sala, Alessandro; Freund, Hajo [Fritz-Haber-Institut, Abt. CP, 14195 Berlin (Germany); Pollinger, Florian; Schmitt, Stefan; Maier, Florian C.; Reinert, Friedrich T. [Universitaet Wuerzburg, EP II, 97074 Wuerzburg (Germany); Umbach, Eberhard [Universitaet Wuerzburg, EP II, 97074 Wuerzburg (Germany); Forschungszentrum Karlsruhe, 76021 Karlsruhe (Germany)

    2009-07-01

    Adsorption of organic molecules on vicinal metal surfaces is known to promote faceting and self-organized ordering on mesoscopic scales. In the temperature range between 400 K and 620 K the adsorption of PTCDA on a Ag(10 8 7) surface has been studied in-situ and in real-time by LEEM (low energy electron microscopy) and LEED, using the SMART microscope. The deposition of one organic layer leads to grating-like structures. The direct observation reveals a two-step process: first, facets with an angle of ca. 25 inclination are formed with (111) orientated areas in between, whereas only the facets are covered by PTCDA. In a second step the bare (111) areas are covered by PTCDA, forming a complete monolayer. The temperature dependence of the structure sizes and the influence of inhomogeneity in the initial substrate step density are discussed.

  12. Structural and electronic properties of polar MnO ultrathin film grown on Ag(111)

    Science.gov (United States)

    Kundu, Asish K.; Menon, Krishnakumar S. R.

    2016-05-01

    Surface electronic structure of ultrathin polar MnO film was studied by Low-energy Electron Diffraction (LEED) and Photoemission Spectroscopic (PES) techniques. Epitaxial monolayer to facet formation with increasing film thickness has been observed by LEED. Our LEED result shows p(2x2) surface reconstruction along with facet formation, stabilize the polar MnO(111) surface. The core levels and the valence band electronic structure of MnO films have been studied as a function of film thickness using X-ray and ultraviolet photoelectron spectroscopy techniques.

  13. Point Electrode Studies of the Solid Electrolyte-Electrode Interface

    DEFF Research Database (Denmark)

    Jacobsen, Torben

    \\parbox[t]{7.3cm}{Strong anodic activation due to computer communication error.} It is seen that as long as the electrode is kept at the equilibrium potential, the capacity pr.\\,unit area is constant, indicating a stable reaction zone. Polarising the electrode a decrease in this ratio is observed. Although......In the development of new electrode materials for high temperature Solid Oxide Fuel Cells methods are needed for the electrochemical evaluation of the catalytic properties of the materials. A major problem in the comparison of materials is how to determine the geometry and the effective length...... of the active reaction zone, the triple phase boundary. One way of solving this is by the application of point electrodes where the electrode-electrolyte contact is assumed to be circular with a radius calculated from the high frequency impedance. The perimeter is the taken as the length of the reaction zone...

  14. Organic electrode coatings for next-generation neural interfaces.

    Science.gov (United States)

    Aregueta-Robles, Ulises A; Woolley, Andrew J; Poole-Warren, Laura A; Lovell, Nigel H; Green, Rylie A

    2014-01-01

    Traditional neuronal interfaces utilize metallic electrodes which in recent years have reached a plateau in terms of the ability to provide safe stimulation at high resolution or rather with high densities of microelectrodes with improved spatial selectivity. To achieve higher resolution it has become clear that reducing the size of electrodes is required to enable higher electrode counts from the implant device. The limitations of interfacing electrodes including low charge injection limits, mechanical mismatch and foreign body response can be addressed through the use of organic electrode coatings which typically provide a softer, more roughened surface to enable both improved charge transfer and lower mechanical mismatch with neural tissue. Coating electrodes with conductive polymers or carbon nanotubes offers a substantial increase in charge transfer area compared to conventional platinum electrodes. These organic conductors provide safe electrical stimulation of tissue while avoiding undesirable chemical reactions and cell damage. However, the mechanical properties of conductive polymers are not ideal, as they are quite brittle. Hydrogel polymers present a versatile coating option for electrodes as they can be chemically modified to provide a soft and conductive scaffold. However, the in vivo chronic inflammatory response of these conductive hydrogels remains unknown. A more recent approach proposes tissue engineering the electrode interface through the use of encapsulated neurons within hydrogel coatings. This approach may provide a method for activating tissue at the cellular scale, however, several technological challenges must be addressed to demonstrate feasibility of this innovative idea. The review focuses on the various organic coatings which have been investigated to improve neural interface electrodes.

  15. Carbon nanotube electrodes for effective interfacing with retinal tissue.

    Science.gov (United States)

    Shoval, Asaf; Adams, Christopher; David-Pur, Moshe; Shein, Mark; Hanein, Yael; Sernagor, Evelyne

    2009-01-01

    We have investigated the use of carbon nanotube coated microelectrodes as an interface material for retinal recording and stimulation applications. Test devices were micro-fabricated and consisted of 60, 30 mum diameter electrodes at spacing of 200 mum. These electrodes were coated via chemical vapor deposition of carbon nanotubes, resulting in conducting, three dimensional surfaces with a high interfacial area. These attributes are important both for the quality of the cell-surface coupling as well as for electro-chemical interfacing efficiency. The entire chip was packaged to fit a commercial multielectrode recording and stimulation system. Electrical recordings of spontaneous spikes from whole-mount neonatal mouse retinas were consistently obtained minutes after retinas were placed over the electrodes, exhibiting typical bursting and propagating waves. Most importantly, the signals obtained with carbon nanotube electrodes have exceptionally high signal to noise ratio, reaching values as high as 75. Moreover, spikes are marked by a conspicuous gradual increase in amplitude recorded over a period of minutes to hours, suggesting improvement in cell-electrode coupling. This phenomenon is not observed in conventional commercial electrodes. Electrical stimulation using carbon nanotube electrodes was also achieved. We attribute the superior performances of the carbon nanotube electrodes to their three dimensional nature and the strong neuro-carbon nanotube affinity. The results presented here show the great potential of carbon nanotube electrodes for retinal interfacing applications. Specifically, our results demonstrate a route to achieve a reduction of the electrode down to few micrometers in order to achieve high efficacy local stimulation needed in retinal prosthetic devices.

  16. Improving acousto-optical interaction by high aspect ratio electrodes

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard

    by conventional interdigital transducers consisting of thin electrodes deposited at the surface. In this work the finite element method is employed to investigate if the acousto-optical interaction can be enhanced by generating the SAWs by interdigital transducers consisting of high aspect ratio electrodes...... these new types of SAWs compared to using the waves generated by the conventional interdigital transducer with thin electrodes. Thus, this indicates a way to improve acousto-optical interaction for integrated modulators, which have important applications such as optical phase shifters....

  17. Lightning electromagnetic field generated by grounding electrode considering soil ionization

    Institute of Scientific and Technical Information of China (English)

    ZENG Rong; HE Jinliang; ZHANG Bo; GAO Yanqing

    2006-01-01

    A circuit model with lumped time-variable parameter is proposed to calculate the transient characteristic of grounding electrode under lightning current, which takes into consideration the dynamic and nonlinear effect of soil ionization around the grounding electrode. The ionization phenomena in the soil are simulated by means of time-variable parameters under appropriate conditions. The generated electromagnetic field in the air is analyzed by using electrical dipole theory and image theory when the lightning current flows into the grounding electrode. The influence of soil ionization on the electromagnetic field is investigated.

  18. Light addressable gold electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Khalid, Waqas

    2011-07-01

    The main objective carried out in this dissertation was to fabricate Light Amplified Potentiometric sensors (LAPS) based upon the semiconductor nanoparticles (quantum dots) instead of its bulk form. Quantum dots (QDs) were opted for this device fabrication because of their superior fluorescent, electric and catalytic properties. Also in comparison to their bulk counterparts they will make device small, light weighted and power consumption is much lower. QDs were immobilized on a Au substrate via 1,4 benzene dithiol (BDT) molecule. Initially a self-assembled monolayer (SAM) of BDT was established on Au substrate. Because of SAM, the conductivity of Au substrate decreased dramatically. Furthermore QDs were anchored with the help of BDT molecule on Au substrate. When QDs immobilized on Au substrate (QD/Au) via BDT molecule were irradiated with UV-visible light, electron-hole pairs were generated in QDs. The surface defect states in QDs trapped the excited electrons and long lived electron-hole pairs were formed. By the application of an appropriate bias potential on Au substrate the electrons could be supplied or extracted from the QDs via tunneling through BDT. Thus a cathodic or anodic current could be observed depending upon bias potential under illumination. However without light illumination the QD/Au electrode remained an insulator. To improve the device different modifications were made, including different substrates (Au evaporated on glass, Au evaporated on mica sheets and Au sputtered on SiO{sub 2}/Si) and different dithiol molecules (capped and uncapped biphenyl 4,4' dithiol and capped and uncapped 4,4' dimercaptostilbenes) were tried. Also different QD immobilization techniques (normal incubation, spin coating, layer by layer assembly (LbL) of polyelectrolytes and heat immobilization) were employed. This device was able to detect electrochemically different analytes depending upon the QDs incorporated. For example CdS QDs were able to detect 4

  19. ELECTROCHEMISTRY OF FUEL CELL ELECTRODES.

    Science.gov (United States)

    optimization of fuel cell electrodes. Hydrogen oxidation and reduction, the reduction of oxygen, and the oxidation of formic acid, a soluble organic...substance, were selected for these studiees because of their relevance to fuel cell systems and because of their relative simplicity. The electrodes

  20. Making EDM Electrodes By Stereolithography

    Science.gov (United States)

    Barlas, Philip A.

    1988-01-01

    Stereolithography is computer-aided manufacturing technique. Used to make models and molds of electrodes for electrical-discharge machining (EDM). Eliminates intermediate steps in fabrication of plastic model of object used in making EDM electrode to manufacture object or mold for object.

  1. Plasma Activation of Integrated Carbon Nanotube Electrodes for Electrochemical Detection of Catechol

    Institute of Scientific and Technical Information of China (English)

    WANG Shenggao; WANG Tao; LI Yanqiong; ZHAO Xiujian; HAN Jianjun; WANG Jianhua

    2007-01-01

    In this study,integrated multi-wall carbon nanotube (MWCNT) electrodes were prepared in the holes of glass directly by microwave plasma chemical vapour deposition (MWPCVD).The electrochemical behaviour of catechol at the integrated MWCNT electrodes was investigated.The oxygen plasma treated CNT electrodes had better electrochemical performance for the analysis of catechol than that of as-synthesized CNT electrodes.Both the as-synthesized CNTs and plasma treated CNTs were characterized by TEM(transmission electron microscopy,XPS(X-ray photoelectron spectroscopy) and Raman spectroscopy.The results revealed that the oxygen plasma activation is an effective method to enhance the electrochemical properties of CNT electrodes.

  2. In-situ Raman spectroscopy as a characterization tool for carbon electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Panitz, J.-C.; Joho, F.B.; Novak, P. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Lithium intercalation and de-intercalation into/from graphite electrodes in a nonaqueous electrolyte has been studied using in-situ Raman spectroscopy. Our experiments give information on the electrode-electrolyte interface with improved spatial resolution. The spectra taken from the electrode surface change with electrode potential. In this way, information on the nature of the chemical species present during charging and discharging half cycles is gained. For the first time, mapping techniques were applied to investigate if lithium intercalation proceeds homogeneously on the carbon electrode. (author) 3 figs., 1 tab., 4 refs.

  3. Site Selection for Hvdc Ground Electrodes

    Science.gov (United States)

    Freire, P. F.; Pereira, S. Y.

    2014-12-01

    High-Voltage Direct Current (HVDC) transmission systems are composed of a bipole transmission line with a converter substation at each end. Each substation may be equipped with a HVDC ground electrode, which is a wide area (up to 1 km Ø) and deep (from 3 to 100m) electrical grounding. When in normal operation, the ground electrode will dissipate in the soil the unbalance of the bipole (~1.5% of the rated current). When in monopolar operation with ground return, the HVDC electrode will inject in the soil the nominal pole continuous current, of about 2000 to 3000 Amperes, continuously for a period up to a few hours. HVDC ground electrodes site selection is a work based on extensive geophysical and geological surveys, in order to attend the desired design requirements established for the electrodes, considering both its operational conditions (maximum soil temperature, working life, local soil voltage gradients etc.) and the interference effects on the installations located up to 50 km away. This poster presents the geophysical investigations conducted primarily for the electrodes site selection, and subsequently for the development of the crust resistivity model, which will be used for the interference studies. A preliminary site selection is conducted, based on general geographical and geological criteria. Subsequently, the geology of each chosen area is surveyed in detail, by means of electromagnetic/electrical geophysical techniques, such as magnetotelluric (deep), TDEM (near-surface) and electroresistivity (shallow). Other complementary geologic and geotechnical surveys are conducted, such as wells drilling (for geotechnical characterization, measurement of the water table depth and water flow, and electromagnetic profiling), and soil and water sampling (for measurement of thermal parameters and evaluation of electrosmosis risk). The site evaluation is a dynamic process along the surveys, and some sites will be discarded. For the two or three final sites, the

  4. Electrode for a lithium cell

    Science.gov (United States)

    Thackeray, Michael M.; Vaughey, John T.; Dees, Dennis W.

    2008-10-14

    This invention relates to a positive electrode for an electrochemical cell or battery, and to an electrochemical cell or battery; the invention relates more specifically to a positive electrode for a non-aqueous lithium cell or battery when the electrode is used therein. The positive electrode includes a composite metal oxide containing AgV.sub.3O.sub.8 as one component and one or more other components consisting of LiV.sub.3O.sub.8, Ag.sub.2V.sub.4O.sub.11, MnO.sub.2, CF.sub.x, AgF or Ag.sub.2O to increase the energy density of the cell, optionally in the presence of silver powder and/or silver foil to assist in current collection at the electrode and to improve the power capability of the cell or battery.

  5. Composite electrode/electrolyte structure

    Science.gov (United States)

    Visco, Steven J.; Jacobson, Craig P.; DeJonghe, Lutgard C.

    2004-01-27

    Provided is an electrode fabricated from highly electronically conductive materials such as metals, metal alloys, or electronically conductive ceramics. The electronic conductivity of the electrode substrate is maximized. Onto this electrode in the green state, a green ionic (e.g., electrolyte) film is deposited and the assembly is co-fired at a temperature suitable to fully densify the film while the substrate retains porosity. Subsequently, a catalytic material is added to the electrode structure by infiltration of a metal salt and subsequent low temperature firing. The invention allows for an electrode with high electronic conductivity and sufficient catalytic activity to achieve high power density in ionic (electrochemical) devices such as fuel cells and electrolytic gas separation systems.

  6. Carbon Nanotube Electrodes for Effective Interfacing with Retinal Tissue

    OpenAIRE

    Shoval, Asaf; Adams, Christopher; David-Pur, Moshe; Shein, Mark; Hanein, Yael; Sernagor, Evelyne

    2009-01-01

    We have investigated the use of carbon nanotube coated microelectrodes as an interface material for retinal recording and stimulation applications. Test devices were micro-fabricated and consisted of 60, 30 μm diameter electrodes at spacing of 200 μm. These electrodes were coated via chemical vapor deposition of carbon nanotubes, resulting in conducting, three dimensional surfaces with a high interfacial area. These attributes are important both for the quality of the cell-surface coupling as...

  7. The problem of skin-electrode processes during medical electrography.

    Science.gov (United States)

    Tatarenko, L

    1975-01-01

    The processes were studied which take place at the skin-electrode zone when surface electrodes are applied to the human body for the medical electrography (ECG, EEG, EMG, etc.). These processes were investigated from the point of view of their influence on the distortion-resistence and the precision of the biopotential registration; they were studied also as a possible source of bioinformation. The results of the experimental research are discussed.

  8. Sputtered iridium oxide films (SIROFs) for neural stimulation electrodes

    OpenAIRE

    Cogan, Stuart F.; Ehrlich, Julia; Plante, Timothy D.; Smirnov, Anton; Shire, Douglas B.; Gingerich, Marcus; Rizzo, Joseph F

    2004-01-01

    Sputtered iridium oxide films (SIROFs) deposited by DC reactive sputtering from an iridium metal target have been characterized in vitro for their potential as neural recording and stimulation electrodes. SIROFs were deposited over gold metallization on flexible multielectrode arrays fabricated on thin (15 µm) polyimide substrates. SIROF thickness and electrode areas of 200–1300 nm and 1960–125600 µm2, respectively, were investigated. The charge-injection capacities of the SIROFs were evaluat...

  9. Advantage of four-electrode over two-electrode defibrillators

    Science.gov (United States)

    Bragard, J.; Šimić, A.; Laroze, D.; Elorza, J.

    2015-12-01

    Defibrillation is the standard clinical treatment used to stop ventricular fibrillation. An electrical device delivers a controlled amount of electrical energy via a pair of electrodes in order to reestablish a normal heart rate. We propose a technique that is a combination of biphasic shocks applied with a four-electrode system rather than the standard two-electrode system. We use a numerical model of a one-dimensional ring of cardiac tissue in order to test and evaluate the benefit of this technique. We compare three different shock protocols, namely a monophasic and two types of biphasic shocks. The results obtained by using a four-electrode system are compared quantitatively with those obtained with the standard two-electrode system. We find that a huge reduction in defibrillation threshold is achieved with the four-electrode system. For the most efficient protocol (asymmetric biphasic), we obtain a reduction in excess of 80% in the energy required for a defibrillation success rate of 90%. The mechanisms of successful defibrillation are also analyzed. This reveals that the advantage of asymmetric biphasic shocks with four electrodes lies in the duration of the cathodal and anodal phase of the shock.

  10. Preset Electrodes for Electrical-Discharge Machining

    Science.gov (United States)

    Coker, Bill E.

    1987-01-01

    New electrode holder for electrical-discharge machining (EDM) provides for repeatable loading and setting of many electrodes. New holder is rotating-index tool carrying six, eight, or more electrodes. Before use, all electrodes set with aid of ring surrounding tool, and locked in position with screws. When electrode replaced, EDM operator pulls spring-loaded pin on tool so it rotates about center pin. Fresh electrode then rotated into position against workpiece.

  11. Virtual electrodes around anatomical structures and their roles in defibrillation

    Science.gov (United States)

    Vigmond, Edward; Bishop, Martin

    2017-01-01

    Background Virtual electrodes from structural/conductivity heterogeneities are known to elicit wavefront propagation, upon field-stimulation, and are thought to be important for defibrillation. In this work we investigate how the constitutive and geometrical parameters associated with such anatomical heterogeneities, represented by endo/epicardial surfaces and intramural surfaces in the form of blood-vessels, affect the virtual electrode patterns produced. Methods and results The steady-state bidomain model is used to obtain, using analytical and numerical methods, the virtual electrode patterns created around idealized endocardial trabeculations and blood-vessels. The virtual electrode pattern around blood-vessels is shown to be composed of two dominant effects; current traversing the vessel surface and conductivity heterogeneity from the fibre-architecture. The relative magnitudes of these two effects explain the swapping of the virtual electrode polarity observed, as a function of the vessel radius, and aid in the understanding of the virtual electrode patterns predicted by numerical bidomain modelling. The relatively high conductivity of blood, compared to myocardium, is shown to cause stronger depolarizations in the endocardial trabeculae grooves than the protrusions. Conclusions The results provide additional quantitative understanding of the virtual electrodes produced by small-scale ventricular anatomy, and highlight the importance of faithfully representing the physiology and the physics in the context of computational modelling of field stimulation. PMID:28253365

  12. Film stresses and electrode buckling in organic solar cells

    KAUST Repository

    Brand, Vitali

    2012-08-01

    We investigate the film stresses that develop in the polymer films and metal electrodes of poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) bulk heterojunction (BHJ) organic solar cells. A compressive biaxial stress of ∼-36 MPa was measured in PEDOT:PSS while a tensile stress of ∼6 MPa was measured in the BHJ layer. We then analyze the effect of electrode deposition rate on the film stresses in the Al electrode. Compressive stresses of ∼-100 to -145 MPa in the Al electrode lead to a buckling instability resulting in undulating electrode surface topography. The BHJ layer was found to have the lowest cohesion (∼1.5-1.8 J/m 2) among the layers of the solar cell and dependent on the Al electrode deposition rate. The cohesive failure path in the BHJ layer exhibited the same periodicity and orientation of the Al electrode buckling topography. We discuss the implications of the film stresses on damage processes during device fabrication and operation. © 2012 Elsevier B.V. All rights reserved.

  13. Effect of Calendering on Electrode Wettability in Lithium Ion Batteries

    Directory of Open Access Journals (Sweden)

    Yangping eSheng

    2014-12-01

    Full Text Available Controlling the wettability between the porous electrode and the electrolyte in lithium ion batteries can improve both the manufacturing process and the electrochemical performance of the cell. The wetting rate, which is the electrolyte transport rate in the porous electrode, can be quantified using the wetting balance. The effect of the calendering process on the wettability of anode electrodes was investigated. A graphite anode film with an as-coated thickness of 59 μm was used as baseline electrode film and was calendered to produce films with thickness ranging from 55 to 41 µm. Results show that wettability is improved by light calendering from an initial thickness of 59 μm to a calendered thickness of 53 μm where the wetting rate increased from 0.375 to 0.589 mm/s0.5. Further calendering below 53 µm resulted in a decrease in wetting rates to a minimum observed value of 0.206 mm/s0.5 at a calendered thickness of 41 μm. Under the same electrolyte, wettability of the electrode is controlled to a great extent by the pore structure in the electrode film which includes parameters such as porosity, pore size distribution, pore geometry and topology. Relations between the wetting behavior and the pore structure as characterized by mercury intrusion and electron microscopy exist and can be used to manipulate the wetting behavior of electrodes.

  14. Capacitance enhancement via electrode patterning

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Tuan A.; Striolo, Alberto, E-mail: a.striolo@ucl.ac.uk [School of Chemical, Biological and Materials Engineering, The University of Oklahoma, Norman, Oklahoma 73019 (United States); Department of Chemical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom)

    2013-11-28

    The necessity of increasing the energy density in electric double layer capacitors to meet current demand is fueling fundamental and applied research alike. We report here molecular dynamics simulation results for aqueous electrolytes near model electrodes. Particular focus is on the effect of electrode patterning on the structure of interfacial electrolytes, and on the potential drop between the solid electrodes and the bulk electrolytes. The latter is estimated by numerically integrating the Poisson equation using the charge densities due to water and ions accumulated near the interface as input. We considered uniform and patterned electrodes, both positively and negatively charged. The uniformly charged electrodes are modeled as graphite. The patterned ones are obtained by removing carbon atoms from the top-most graphene layer, yielding nanoscopic squares and stripes patterns. For simplicity, the patterned electrodes are effectively simulated as insulators (the charge remains localized on the top-most layer of carbon atoms). Our simulations show that the patterns alter the structure of water and the accumulation of ions at the liquid-solid interfaces. Using aqueous NaCl solutions, we found that while the capacitance calculated for three positively charged electrodes did not change much, that calculated for the negatively charged electrodes significantly increased upon patterning. We find that both water structure and orientation, as well as ion accumulation affect the capacitance. As electrode patterning affects differently water structure and ion accumulation, it might be possible to observe ion-specific effects. These results could be useful for advancing our understanding of electric double layer capacitors, capacitive desalination processes, as well as of fundamental interfacial electrolytes properties.

  15. Capacitance enhancement via electrode patterning

    Science.gov (United States)

    Ho, Tuan A.; Striolo, Alberto

    2013-11-01

    The necessity of increasing the energy density in electric double layer capacitors to meet current demand is fueling fundamental and applied research alike. We report here molecular dynamics simulation results for aqueous electrolytes near model electrodes. Particular focus is on the effect of electrode patterning on the structure of interfacial electrolytes, and on the potential drop between the solid electrodes and the bulk electrolytes. The latter is estimated by numerically integrating the Poisson equation using the charge densities due to water and ions accumulated near the interface as input. We considered uniform and patterned electrodes, both positively and negatively charged. The uniformly charged electrodes are modeled as graphite. The patterned ones are obtained by removing carbon atoms from the top-most graphene layer, yielding nanoscopic squares and stripes patterns. For simplicity, the patterned electrodes are effectively simulated as insulators (the charge remains localized on the top-most layer of carbon atoms). Our simulations show that the patterns alter the structure of water and the accumulation of ions at the liquid-solid interfaces. Using aqueous NaCl solutions, we found that while the capacitance calculated for three positively charged electrodes did not change much, that calculated for the negatively charged electrodes significantly increased upon patterning. We find that both water structure and orientation, as well as ion accumulation affect the capacitance. As electrode patterning affects differently water structure and ion accumulation, it might be possible to observe ion-specific effects. These results could be useful for advancing our understanding of electric double layer capacitors, capacitive desalination processes, as well as of fundamental interfacial electrolytes properties.

  16. Carbon nanotube electrodes for effective interfacing with retinal tissue

    Directory of Open Access Journals (Sweden)

    Asaf Shoval

    2009-04-01

    Full Text Available We have investigated the use of carbon nanotube microelectrodes as an interface material for retinal recording and stimulation applications. Test devices were micro-fabricated and consisted of 60 pristine 30 um electrodes coated with chemical vapor deposited carbon nanotubes, resulting in conducting, three dimensional surfaces with a high effective interfacial area. These attributes are important both for the quality of the cell-surface coupling as well as for electro-chemical interfacing efficiency. The entire chip was packaged to fit a commercial multielectrode recording and stimulation system. Electrical recordings of spontaneous spikes from whole-mount neonatal mouse retinas were consistently obtained minutes after retinas were placed over the electrodes, exhibiting typical bursting and propagating waves. Most importantly, the signals obtained with carbon nanotube electrodes have exceptionally high signal to noise ratio, reaching values as high as 75. Moreover, spikes are marked by a conspicuous gradual increase in amplitude recorded over a period of minutes to hours, suggesting improvement in cell-electrode coupling. This phenomenon is not observed in conventional commercial electrodes. Electrical stimulation using carbon nanotube electrodes was also achieved. We attribute the superior performances of the carbon nanotube electrodes to their three dimensional nature and the strong neuro-carbon nanotube affinity. The results presented here show the great potential of carbon nanotube electrodes for retinal interfacing applications. Specifically, our results demonstrate a route to achieve a reduction in the electrode size down to few micrometers in order to achieve high efficacy local stimulation needed in retinal prosthetic devices.

  17. Nanostructured copper particles-incorporated Nafion-modified electrode for oxygen reduction

    Indian Academy of Sciences (India)

    T Selvaraju; R Ramaraj

    2005-10-01

    The electrocatalytic activity of nanostructured copper particles (represented as Cunano) incorporated Nafion (Nf) film-coated glassy carbon (GC) electrode (GC/Nf/Cunano) towards oxygen reduction was investigated in oxygenated 0.1 M phosphate buffer (pH 7.2). The electrodeposited Cunano in Nf film was characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity of Cunano at the modified electrode towards oxygen reduction was studied using cyclic voltammetry technique. The molecular oxygen reduction at the GC/Nf/Cunano-modified electrode started at a more positive potential than at a bare GC electrode. A possible reaction mechanism was proposed in which oxygen reduction may proceed through two-step two-electron processes at the GC/Nf/Cunano electrode. The GC/Nf/Cunano electrode shows higher stability for oxygen reduction in neutral solution and the electrode may find applications in fuel cells.

  18. An analytical model for electrode-ceramic interaction in multilayer piezoelectric actuators

    Institute of Scientific and Technical Information of China (English)

    B. L. Wang; J. C. Han

    2007-01-01

    The present paper develops an analytical model for multi-electrodes in multi-layered piezoelectric actuators, in which the electrodes are vertical to and terminated at the edges of the medium and electroelastic field concentrations ahead of the electrodes in the multilayer piezoelectric actuators are examined. By considering a representative unit in realistic multilayers, the problem is formulated in terms of electric potential between the electrode tips and results in a system of singular integral equations in which the electric potential is taken as unknown function. Effects are investigated of electrode spacing and piezoelectric coupling on the singular electroelastic fields at the electrode tips, and closed-form expressions are given for the electromechanical field near the electrode tips. Exact solution for un-coupled dielectrics is provided, where no piezoelectric coupling is present.

  19. Electrocatalytic Activity of Ti/TiO2 Electrodes in H2SO4 Solution

    Institute of Scientific and Technical Information of China (English)

    王雅琼; 童宏扬; 许文林

    2003-01-01

    Ti/TiO2 electrodes were prepared with the polymeric precursor method (PPM). The structure and morphology of Ti/TiO2 electrodes were examined with XRD and ESEM. The voltammetric charge (q*) of Ti/TiO2 electrodes as cathode in 0.5 mol/L H2SO4 solution was investigated with cyclic voltammetry. It was found that the electrocatalytic activity of the Ti/TiO2 electrodes was affected by the structure and morphology of the Ti/TiO2 electrodes, in other words, was affected by the calcination conditions of preparing the electrodes. The value of q*ln was considerably larger than that of q*out,which means that the 'inner' active surface area was much larger than the 'outer' active surface area, and 'inner' active surface played a main role in the electrocatalytic activity of the Ti/TiO2 electrodes.

  20. Development of a Compact Wireless Laplacian Electrode Module for Electromyograms and Its Human Interface Applications

    Directory of Open Access Journals (Sweden)

    Akira Ichikawa

    2013-02-01

    Full Text Available In this study, we developed a compact wireless Laplacian electrode module for electromyograms (EMGs. One of the advantages of the Laplacian electrode configuration is that EMGs obtained with it are expected to be sensitive to the firing of the muscle directly beneath the measurement site. The performance of the developed electrode module was investigated in two human interface applications: character-input interface and detection of finger movement during finger Braille typing. In the former application, the electrode module was combined with an EMG-mouse click converter circuit. In the latter, four electrode modules were used for detection of finger movements during finger Braille typing. Investigation on the character-input interface indicated that characters could be input stably by contraction of (a the masseter, (b trapezius, (c anterior tibialis and (d flexor carpi ulnaris muscles. This wide applicability is desirable when the interface is applied to persons with physical disabilities because the disability differs one to another. The investigation also demonstrated that the electrode module can work properly without any skin preparation. Finger movement detection experiments showed that each finger movement was more clearly detectable when comparing to EMGs recorded with conventional electrodes, suggesting that the Laplacian electrode module is more suitable for detecting the timing of finger movement during typing. This could be because the Laplacian configuration enables us to record EMGs just beneath the electrode. These results demonstrate the advantages of the Laplacian electrode module.

  1. Forward and inverse effects of the complete electrode model in neonatal EEG.

    Science.gov (United States)

    Pursiainen, S; Lew, S; Wolters, C H

    2017-03-01

    This paper investigates finite element method-based modeling in the context of neonatal electroencephalography (EEG). In particular, the focus lies on electrode boundary conditions. We compare the complete electrode model (CEM) with the point electrode model (PEM), which is the current standard in EEG. In the CEM, the voltage experienced by an electrode is modeled more realistically as the integral average of the potential distribution over its contact surface, whereas the PEM relies on a point value. Consequently, the CEM takes into account the subelectrode shunting currents, which are absent in the PEM. In this study, we aim to find out how the electrode voltage predicted by these two models differ, if standard size electrodes are attached to a head of a neonate. Additionally, we study voltages and voltage variation on electrode surfaces with two source locations: 1) next to the C6 electrode and 2) directly under the Fz electrode and the frontal fontanel. A realistic model of a neonatal head, including a skull with fontanels and sutures, is used. Based on the results, the forward simulation differences between CEM and PEM are in general small, but significant outliers can occur in the vicinity of the electrodes. The CEM can be considered as an integral part of the outer head model. The outcome of this study helps understanding volume conduction of neonatal EEG, since it enlightens the role of advanced skull and electrode modeling in forward and inverse computations.NEW & NOTEWORTHY The effect of the complete electrode model on electroencephalography forward and inverse computations is explored. A realistic neonatal head model, including a skull structure with fontanels and sutures, is used. The electrode and skull modeling differences are analyzed and compared with each other. The results suggest that the complete electrode model can be considered as an integral part of the outer head model. To achieve optimal source localization results, accurate electrode

  2. Electrode materials for microbial fuel cells: nanomaterial approach

    KAUST Repository

    Mustakeem, Mustakeem

    2015-11-05

    Microbial fuel cell (MFC) technology has the potential to become a major renewable energy resource by degrading organic pollutants in wastewater. The performance of MFC directly depends on the kinetics of the electrode reactions within the fuel cell, with the performance of the electrodes heavily influenced by the materials they are made from. A wide range of materials have been tested to improve the performance of MFCs. In the past decade, carbon-based nanomaterials have emerged as promising materials for both anode and cathode construction. Composite materials have also shown to have the potential to become materials of choice for electrode manufacture. Various transition metal oxides have been investigated as alternatives to conventional expensive metals like platinum for oxygen reduction reaction. In this review, different carbon-based nanomaterials and composite materials are discussed for their potential use as MFC electrodes.

  3. Chiral Recognition of Amino Acids by Magnetoelectrodeposited Cu Film Electrodes

    Directory of Open Access Journals (Sweden)

    Iwao Mogi

    2011-01-01

    Full Text Available Chiral behavior of magnetoelectrodeposited (MED Cu film electrodes was investigated for the electrochemical reactions of amino acids. The Cu films were electrodeposited under a magnetic field of 5 T perpendicular to the electrode surface. Such MED Cu films were employed as an electrode, and cyclic voltammograms were measured for the electrochemical reactions of several kinds of amino acids. Chiral behavior was clearly observed as oxidation current difference between the enantiomers of alanine, aspartic acid, and glutamic acid. The MED film electrodes with the thickness of 50~500 nm exhibited such chiral behavior, and their surface morphologies had network structures, which could be induced by the micro-MHD effect.

  4. Inkjet Printing of Back Electrodes for Inverted Polymer Solar cells

    DEFF Research Database (Denmark)

    Angmo, Dechan; Sweelssen, Jorgen; Andriessen, Ronn;

    2013-01-01

    in an otherwise fast roll-to-roll production line. In this paper, the applicability of inkjet printing in the ambient processing of back electrodes in inverted polymer solar cells with the structure ITO/ZnO/P3HT:PCBM/PEDOT:PSS/ Ag is investigated. Furthermore, the limitation of screen printing, the commonly......Evaporation is the most commonly used deposition method in the processing of back electrodes in polymer solar cells used in scientifi c studies. However, vacuum-based methods such as evaporation are uneconomical in the upscaling of polymer solar cells as they are throughput limiting steps...... employed method in the ambient processing of back electrode, is demonstrated and discussed. Both inkjet printing and screen printing of back electrodes are studied for their impact on the photovoltaic properties of the polymer solar cells measured under 1000 Wm−2 AM1.5. Each ambient processing technique...

  5. Kinetic Studies on Ni-YSZ Composite Electrodes

    DEFF Research Database (Denmark)

    Njodzefon, Jean-Claude; Hjelm, Johan; Graves, Christopher R.

    2015-01-01

    . Furthermore, when polarized, the cell heats up due to joule heating of the electrolyte but also the electrodes either heat or cool due to exothermic oxidation or endothermic reduction of gaseous reactant species. Kinetic investigation of SOC electrodes independent of the above effects thus requires...... transfer at the reaction sites gas conversion at the flow fields, and ohmic drop across the electrolyte. Since these processes occur in both electrodes and some of them with overlapping characteristic frequencies, it is particularly challenging to isolate and characterize a particular mechanism...... compositions using the same instrument. The tests are carried out in a single gas atmosphere with maximum flow rate of 6 L/h. Results and Discussion Current density vs working electrode overpotential curves recorded in the temperature range 800 – 650°C in a 50/50 H2/H2O fuel mixture are displayed in figure 1(a...

  6. Non-polarisable dry electrode based on NASICON ceramic.

    Science.gov (United States)

    Gondran, C; Siebert, E; Fabry, P; Novakov, E; Gumery, P Y

    1995-05-01

    A NASICON-type ceramic (high sodium ion conductor) is proposed to record bioelectric signals. The electrode does not need gel before its application. The principle of the measurements is based on a sodium ion exchange between the skin and the material. Electrical measurements performed in saline solutions show that the electrode is slightly polarisable. The skin-electrode impedance was investigated. The impedance decreases as a function of the time of application. The resistive component is the major source of the impedance change. This can be explained by the perspiration process which occurs immediately with time after the application of the NASICON-based electrode on the skin. The skin condition is also an important parameter. NaCl saline solution or abrasion causes the resistance to decrease markedly.

  7. Synchronized Current Oscillations of Formic Acid Electro-oxidation in a Microchip-based Dual-Electrode Flow Cell

    Science.gov (United States)

    Kiss, István Z.; Munjal, Neil; Martin, R. Scott

    2009-01-01

    We investigate the oscillatory electro-oxidation of formic acid on platinum in a microchip-based dual-electrode cell with microfluidic flow control. The main dynamical features of current oscillations on single Pt electrode that had been observed in macro-cells are reproduced in the microfabricated electrochemical cell. In dual-electrode configuration nearly in-phase synchronized current oscillations occur when the reference/counter electrodes are placed far away from the microelectrodes. The synchronization disappears with close reference/counter electrode placements. We show that the cause for synchronization is weak albeit important, bidirectional electrical coupling between the electrodes; therefore the unidirectional mass transfer interactions are negligible. The experimental design enables the investigation of the dynamical behavior in micro-electrode arrays with well-defined control of flow of the electrolyte in a manner where the size and spacing of the electrodes can be easily varied. PMID:20160883

  8. Synchronized Current Oscillations of Formic Acid Electro-oxidation in a Microchip-based Dual-Electrode Flow Cell.

    Science.gov (United States)

    Kiss, István Z; Munjal, Neil; Martin, R Scott

    2009-12-30

    We investigate the oscillatory electro-oxidation of formic acid on platinum in a microchip-based dual-electrode cell with microfluidic flow control. The main dynamical features of current oscillations on single Pt electrode that had been observed in macro-cells are reproduced in the microfabricated electrochemical cell. In dual-electrode configuration nearly in-phase synchronized current oscillations occur when the reference/counter electrodes are placed far away from the microelectrodes. The synchronization disappears with close reference/counter electrode placements. We show that the cause for synchronization is weak albeit important, bidirectional electrical coupling between the electrodes; therefore the unidirectional mass transfer interactions are negligible. The experimental design enables the investigation of the dynamical behavior in micro-electrode arrays with well-defined control of flow of the electrolyte in a manner where the size and spacing of the electrodes can be easily varied.

  9. Probing Electrode Heterogeneity Using Fourier-Transformed Alternating Current Voltammetry: Application to a Dual-Electrode Configuration.

    Science.gov (United States)

    Tan, Sze-Yin; Unwin, Patrick R; Macpherson, Julie V; Zhang, Jie; Bond, Alan M

    2017-03-07

    Quantitative studies of electron transfer processes at electrode/electrolyte interfaces, originally developed for homogeneous liquid mercury or metallic electrodes, are difficult to adapt to the spatially heterogeneous nanostructured electrode materials that are now commonly used in modern electrochemistry. In this study, the impact of surface heterogeneity on Fourier-transformed alternating current voltammetry (FTACV) has been investigated theoretically under the simplest possible conditions where no overlap of diffusion layers occurs and where numerical simulations based on a 1D diffusion model are sufficient to describe the mass transport problem. Experimental data that meet these requirements can be obtained with the aqueous [Ru(NH3)6](3+/2+) redox process at a dual-electrode system comprised of electrically coupled but well-separated glassy carbon (GC) and boron-doped diamond (BDD) electrodes. Simulated and experimental FTACV data obtained with this electrode configuration, and where distinctly different heterogeneous charge transfer rate constants (k(0) values) apply at the individual GC and BDD electrode surfaces, are in excellent agreement. Principally, because of the far greater dependence of the AC current magnitude on k(0), it is straightforward with the FTACV method to resolve electrochemical heterogeneities that are ∼1-2 orders of magnitude apart, as applies in the [Ru(NH3)6](3+/2+) dual-electrode configuration experiments, without prior knowledge of the individual kinetic parameters (k(0)1 and k(0)2) or the electrode size ratio (θ1:θ2). In direct current voltammetry, a difference in k(0) of >3 orders of magnitude is required to make this distinction.

  10. Removal of suspended solids and turbidity from marble processing wastewaters by electrocoagulation: Comparison of electrode materials and electrode connection systems

    Energy Technology Data Exchange (ETDEWEB)

    Solak, Murat [Duezce University, Kaynasli Vocational School, Environmental Protection and Control Department, 81900 Duezce (Turkey); Kilic, Mehmet, E-mail: kavi@mmf.sdu.edu.tr [Sueleyman Demirel University, Engineering and Architecture Faculty, Environmental Engineering Department, 32260 Isparta (Turkey); Hueseyin, Yazici; Sencan, Aziz [Sueleyman Demirel University, Engineering and Architecture Faculty, Environmental Engineering Department, 32260 Isparta (Turkey)

    2009-12-15

    In this study, removal of suspended solids (SS) and turbidity from marble processing wastewaters by electrocoagulation (EC) process were investigated by using aluminium (Al) and iron (Fe) electrodes which were run in serial and parallel connection systems. To remove these pollutants from the marble processing wastewater, an EC reactor including monopolar electrodes (Al/Fe) in parallel and serial connection system, was utilized. Optimization of differential operation parameters such as pH, current density, and electrolysis time on SS and turbidity removal were determined in this way. EC process with monopolar Al electrodes in parallel and serial connections carried out at the optimum conditions where the pH value was 9, current density was approximately 15 A/m{sup 2}, and electrolysis time was 2 min resulted in 100% SS removal. Removal efficiencies of EC process for SS with monopolar Fe electrodes in parallel and serial connection were found to be 99.86% and 99.94%, respectively. Optimum parameters for monopolar Fe electrodes in both of the connection types were found to be for pH value as 8, for electrolysis time as 2 min. The optimum current density value for Fe electrodes used in serial and parallel connections was also obtained at 10 and 20 A/m{sup 2}, respectively. Based on the results obtained, it was found that EC process running with each type of the electrodes and the connections was highly effective for the removal of SS and turbidity from marble processing wastewaters, and that operating costs with monopolar Al electrodes in parallel connection were the cheapest than that of the serial connection and all the configurations for Fe electrode.

  11. Thin film fuel cell electrodes.

    Science.gov (United States)

    Asher, W. J.; Batzold, J. S.

    1972-01-01

    Earlier work shows that fuel cell electrodes prepared by sputtering thin films of platinum on porous vycor substrates avoid diffusion limitations even at high current densities. The presented study shows that the specific activity of sputtered platinum is not unusually high. Performance limitations are found to be controlled by physical processes, even at low loadings. Catalyst activity is strongly influenced by platinum sputtering parameters, which seemingly change the surface area of the catalyst layer. The use of porous nickel as a substrate shows that pore size of the substrate is an important parameter. It is noted that electrode performance increases with increasing loading for catalyst layers up to two microns thick, thus showing the physical properties of the sputtered layer to be different from platinum foil. Electrode performance is also sensitive to changing differential pressure across the electrode. The application of sputtered catalyst layers to fuel cell matrices for the purpose of obtaining thin total cells appears feasible.

  12. The Character of Photo-electrochemistry of Palladium Implanted TiO2 Nano-crystalline Electrode

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new electrode was prepared by using Pd implanted into nano-crystalline TiO2 and the character of photo-electrochemistry of implanted electrodes was investigated. The energy band structure of nano-crystalline TiO2 has not changed after implantation with Pd. The photo-current (iph) of palladium implanted TiO2 nano-crystalline electrode is larger than that of pure TiO2 nano-crystalline electrode.

  13. Electron transfer at sensitized semiconductor electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Spitler, M.T.

    1977-03-01

    Electron transfer from the excited state of sensitizing dyes to the conduction band of semiconductors has been studied through photoelectrochemical techniques. Two systems were analyzed in detail: rhodamine B on ZnO and rose bengal on TiO/sub 2/. Prior to electrochemical experimentation, the adsorption characteristics of these dyes were investigated using ZnO, ZnS, and TiO/sub 2/ single crystals as substrates. Absorbance measurements of the adsorbed dye were taken as a function of the solution concentration of the dye. Adsorption isotherms heats of adsorption were also established; they were similar to literature data reported for adsorption of these dyes on powdered substrates. Using the absorbance data, the quantum efficiency for photoinjection of electrons from rhodamine B into a ZnO electrode was determined to be 2.7 x 10/sup -2/. This value was independent of the dye surface concentration down to 50% coverage of the electrode. With the assumption that not all of the rhodamine B adsorbed on the electrode has the same rate of electron injection, a kinetic model for the time decay of the photocurrent was developed; data were analyzed according to this theory. A rate constant for photoreduction of the adsorbed dye was determined for the reducing agents. 86 references.

  14. High Speed, Low Cost Fabrication of Gas Diffusion Electrodes for Membrane Electrode Assemblies

    Energy Technology Data Exchange (ETDEWEB)

    DeCastro, Emory S.; Tsou, Yu-Min; Liu, Zhenyu

    2013-09-20

    Fabrication of membrane electrode assemblies (MEAs) depends on creating inks or pastes of catalyst and binder, and applying this suspension to either the membrane (catalyst coated membrane) or gas diffusion media (gas diffusion electrode) and respectively laminating either gas diffusion media or gas diffusion electrodes (GDEs) to the membrane. One barrier to cost effective fabrication for either of these approaches is the development of stable and consistent suspensions. This program investigated the fundamental forces that destabilize the suspensions and developed innovative approaches to create new, highly stable formulations. These more concentrated formulations needed fewer application passes, could be coated over longer and wider substrates, and resulted in significantly lower coating defects. In March of 2012 BASF Fuel Cell released a new high temperature product based on these advances, whereby our customers received higher performing, more uniform MEAs resulting in higher stack build yields. Furthermore, these new materials resulted in an “instant” increase in capacity due to higher product yields and material throughput. Although not part of the original scope of this program, these new formulations have also led us to materials that demonstrate equivalent performance with 30% less precious metal in the anode. This program has achieved two key milestones in DOE’s Manufacturing R&D program: demonstration of processes for direct coating of electrodes and continuous in-line measurement for component fabrication.

  15. Stimulation and recording electrodes for neural prostheses

    CERN Document Server

    Pour Aryan, Naser; Rothermel, Albrecht

    2015-01-01

    This book provides readers with basic principles of the electrochemistry of the electrodes used in modern, implantable neural prostheses. The authors discuss the boundaries and conditions in which the electrodes continue to function properly for long time spans, which are required when designing neural stimulator devices for long-term in vivo applications. Two kinds of electrode materials, titanium nitride and iridium are discussed extensively, both qualitatively and quantitatively. The influence of the counter electrode on the safety margins and electrode lifetime in a two electrode system is explained. Electrode modeling is handled in a final chapter.

  16. Implanted electrodes for multi-month EEG.

    Science.gov (United States)

    Jochum, Thomas; Engdahl, Susannah; Kolls, Brad J; Wolf, Patrick

    2014-01-01

    An implanted electroencephalogram (EEG) recorder would help diagnose infrequent seizure-like events. A proof-of-concept study quantified the electrical characteristics of the electrodes planned for the proposed recorder. The electrodes were implanted in an ovine model for eight weeks. Electrode impedance was less than 800 Ohms throughout the study. A frequency-domain determination of sedation performed similarly for surface versus implanted electrodes throughout the study. The time-domain correlation between an implanted electrode and a surface electrode was almost as high as between two surface electrodes (0.86 versus 0.92). EEG-certified clinicians judged that the implanted electrode quality was adequate to excellent and that the implanted electrodes provided the same clinical information as surface electrodes except for a noticeable amplitude difference. No significant issues were found that would stop development of the EEG recorder.

  17. Investigation of reaction mechanisms during electroreduction of carbon dioxide on lead electrode for the production of organic compounds; Etude des mecanismes reactionnels de l'electro-reduction du dioxyde de carbone sur le plomb en vue de sa transformation en des composes organiques

    Energy Technology Data Exchange (ETDEWEB)

    Innocent, B

    2008-09-15

    The aim of this work was to promote the reduction of CO{sub 2} through its electrochemical conversion (electro-synthesis) on a lead electrode into high added value products. Depending on the nature of electrolyte, the electro-reduction of carbon dioxide leads to different products. Various electrolytes (aqueous or organic, protic or aprotic) were used to study two mechanisms: hydrogenation (formation of formate) and electro-dimerization (synthesis of oxalate). Cyclic voltammetry studies have been carried out for electrochemically characterizing CO{sub 2} reduction on Pb. The electrochemical investigation of the electrode electrolyte interface has shown that the process of CO{sub 2} electro-reduction is a mass transfer control both in the organic and aqueous media. Electrochemical experiments (cyclic voltammetry, chrono-amperometry) coupled with in situ infrared reflectance spectroscopic techniques (SPAIRS, SNIFTIRS) have also shown that in aqueous medium (7 {<=}pH{<=}9) hydrogeno-carbonate ions were reduced to formate. The modification of solvent (propylene carbonate) leads selectively to oxalate as the main reaction product. Long-term electrolyses were performed in a filter-press cell to deal large volumes. In aqueous medium, the reduction of HCO{sub 3}{sup -} to HCOO{sup -} (R{sub F} = 89% at -2.5 mA cm{sup -2} and 4 C) is always accompanied by the production of H{sub 2}. (author)

  18. Extraction electrode geometry for a calutron

    Science.gov (United States)

    Veach, A.M.; Bell, W.A. Jr.

    1975-09-23

    This patent relates to an improved geometry for the extraction electrode and the ground electrode utilized in the operation of a calutron. The improved electrodes are constructed in a partial-picture-frame fashion with the slits of both electrodes formed by two tungsten elongated rods. Additional parallel spaced-apart rods in each electrode are used to establish equipotential surfaces over the rest of the front of the ion source. (auth)

  19. Toward Uniformly Dispersed Battery Electrode Composite Materials: Characteristics and Performance.

    Science.gov (United States)

    Kwon, Yo Han; Huie, Matthew M; Choi, Dalsu; Chang, Mincheol; Marschilok, Amy C; Takeuchi, Kenneth J; Takeuchi, Esther S; Reichmanis, Elsa

    2016-02-10

    Battery electrodes are complex mesoscale systems comprised of electroactive components, conductive additives, and binders. In this report, methods for processing electrodes with dispersion of the components are described. To investigate the degree of material dispersion, a spin-coating technique was adopted to provide a thin, uniform layer that enabled observation of the morphology. Distinct differences in the distribution profile of the electrode components arising from individual materials physical affinities were readily identified. Hansen solubility parameter (HSP) analysis revealed pertinent surface interactions associated with materials dispersivity. Further studies demonstrated that HSPs can provide an effective strategy to identify surface modification approaches for improved dispersions of battery electrode materials. Specifically, introduction of surfactantlike functionality such as oleic acid (OA) capping and P3HT-conjugated polymer wrapping on the surface of nanomaterials significantly enhanced material dispersity over the composite electrode. The approach to the surface treatment on the basis of HSP study can facilitate design of composite electrodes with uniformly dispersed morphology and may contribute to enhancing their electrical and electrochemical behaviors. The conductivity of the composites and their electrochemical performance was also characterized. The study illustrates the importance of considering electronic conductivity, electron transfer, and ion transport in the design of environments incorporating active nanomaterials.

  20. Nanomolar determination of Pb (II ions by selective templated electrode

    Directory of Open Access Journals (Sweden)

    Mazloum-Ardakani Mohammad

    2012-01-01

    Full Text Available Polypyrrole modified electrode, prepared by electropolymerization of pyrrole in the presence of methyl red as a dopant, was templated with respect to Pb2+ ion and applied for potentiometric and voltammetric detection of this ion. The templating process improved the analytical response characteristics of the electrode, specially their selectivity, with respect to Pb2+ ion. The improvement depends on both the incorporated ligand (dopant and the templating process, with the latter being more vital. The potentiometric response of the electrode was linear within the Pb2+ concentration range of 2.0×10-6 to 5.0×10-2 M with a near-Nernstian slope of 28.6 mV decade-1 and a detection limit of 7.0 ×10-7 M. The electrode was also used for preconcentration differential pulse anodic stripping voltammetry (DPASV and results showed that peak currents for the incorporated lead species were dependent on the metal ion concentration in the range of 1.0×10-8 to 1.0×10-3 M. The detection limit of DPASV method was 3.5 ×10-9 M. The selectivity of the electrode with respect to some transition metal ions was investigated. The modified-templated electrode was used for the successful assay of lead in two standard reference material samples.

  1. Effect of Calendering on Electrode Wettability in Lithium-Ion Batteries

    OpenAIRE

    Yangping eSheng; Christopher R. Fell; Yong Kyu Son; Bernhard M. Metz; Junwei eJiang; Benjamin C. Church

    2014-01-01

    Controlling the wettability between the porous electrode and the electrolyte in lithium-ion batteries can improve both the manufacturing process and the electrochemical performance of the cell. The wetting rate, which is the electrolyte transport rate in the porous electrode, can be quantified using the wetting balance. The effect of the calendering process on the wettability of anode electrodes was investigated. A graphite anode film with an as-coated thickness of 59 μm was used as baseline ...

  2. Influence of patterned electrode geometry on performance of co-planar, single-chamber, solid oxide fuel cell

    Science.gov (United States)

    Ahn, Sung-Jin; Kim, Yong-Bum; Moon, Jooho; Lee, Jong-Ho; Kim, Joosun

    Co-planar, single-chamber, solid oxide fuel cells (SC-SOFCs) with linearly patterned electrode structures on one surface of the electrolyte are fabricated via a robo-dispensing method. The SC-SOFCs with various electrode patterns are prepared to investigate the relationship between electrode geometry and cell performance. The open-circuit voltage (OCV) for cells with a single electrode pair is unaffected by the anode-to-cathode distance. By contrast, for cells with multiple electrode pairs, increasing the number of electrode pairs leads to a gradual decrease in OCV. These observations confirm that the inter-mixing of product gases causes a loss in OCV and power density, which in turn reduces the oxygen partial pressure gradient between the anode and cathode. Keeping the electrode pairs apart by ∼4 mm permits cells with complex electrode geometry to exhibit higher OCVs and power densities.

  3. Influence of patterned electrode geometry on performance of co-planar, single-chamber, solid oxide fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Sung-Jin; Kim, Yong-Bum; Moon, Jooho [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea); Lee, Jong-Ho; Kim, Joosun [Nano-Materials Research Center, KIST, Seoul 136-791 (Korea)

    2007-09-27

    Co-planar, single-chamber, solid oxide fuel cells (SC-SOFCs) with linearly patterned electrode structures on one surface of the electrolyte are fabricated via a robo-dispensing method. The SC-SOFCs with various electrode patterns are prepared to investigate the relationship between electrode geometry and cell performance. The open-circuit voltage (OCV) for cells with a single electrode pair is unaffected by the anode-to-cathode distance. By contrast, for cells with multiple electrode pairs, increasing the number of electrode pairs leads to a gradual decrease in OCV. These observations confirm that the inter-mixing of product gases causes a loss in OCV and power density, which in turn reduces the oxygen partial pressure gradient between the anode and cathode. Keeping the electrode pairs apart by {proportional_to}4 mm permits cells with complex electrode geometry to exhibit higher OCVs and power densities. (author)

  4. Using mesoporous carbon electrodes for brackish water desalination.

    Science.gov (United States)

    Zou, Linda; Li, Lixia; Song, Huaihe; Morris, Gayle

    2008-04-01

    Electrosorptive deionisation is an alternative process to remove salt ions from the brackish water. The porous carbon materials are used as electrodes. When charged in low voltage electric fields, they possess a highly charged surface that induces adsorption of salt ions on the surface. This process is reversible, so the adsorbed salt ions can be desorbed and the electrode can be reused. In the study, an ordered mesoporous carbon (OMC) electrode was developed for electrosorptive desalination. The effects of pore arrangement pattern (ordered and random) and pore size distribution (mesopores and micropores) on the desalination performance was investigated by comparing OMC and activated carbon (AC). It were revealed from X-ray diffraction and N(2) sorption measurements that AC has both micropores and mesopores, whereas ordered mesopores are dominant in OMC. Their performance as potential electrodes to remove salt was evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge tests at a range of electrolyte concentrations and sweep rates. It is deduced that under the same electrochemical condition the specific capacitance values of OMC electrode (i.e. 133 F/g obtained from CV at a sweep rate of 1 mV/s in 0.1M NaCl solution) are larger than those of AC electrode (107 F/g), suggesting that the former has a higher desalting capacity than the latter. Furthermore, the OMC electrode shows a better rate capacity than the AC electrode. In addition, the desalination capacities were quantified by the batch-mode experiment at low voltage of 1.2V in 25 ppm NaCl solution (50 micros/cm conductivity). It was found that the adsorbed ion amounts of OMC and AC electrodes were 11.6 and 4.3 micromol/g, respectively. The excellent electrosorptive desalination performance of OMC electrode might be not only due to the suitable pore size (average of 3.3 nm) for the propagation of the salt ions, but also due to the ordered mesoporous structure that facilitates desorption of the

  5. Wire beam electrode technique for investigating galvanic corrosion behavior of galvanized steel-spot defect%丝束电极研究镀锌层存在点缺陷的锌/钢电偶腐蚀行为

    Institute of Scientific and Technical Information of China (English)

    张大磊; 王伟; 金有海; 唐晓; 李焰

    2011-01-01

    采用3种不同配置比例的锌/碳钢异材质丝束电极,模拟镀锌层存在不同大小点缺陷时的热浸镀钢,研究锌/钢电偶在不同腐蚀阶段的电位和电流密度分布.结果表明,在钢丝与锌丝面积比为1:120、9:112和25:96的3种情况下,锌丝均能给钢丝提供足够的阴极保护,且锌丝之间存在明显的电位、电流分布不均现象,主要阳极区先随机地在邻近钢丝的锌丝区域内转移,而后逐渐向远端锌丝扩展;钢丝之间也存在电化学参数分布不均一现象,钢丝在受到保护的同时表面会有氢原子析出,且随着阴、阳极面积比的增大,析氢电流密度逐渐减小.%Three kinds of wire beam electrodes(WBE) composed of zinc and mild steel wires were developed, which were used to simulate hot-dip galvanized steel with spot coating defect at different dimensions, to obtain the spatial distributions of potential and current density and their variations with time during the galvanic corrosion. The results show that the zinc wires within WBEs can provide enough cathodic protection to steel wires after immersed in seawater, with surface area ratio of zinc wires to steel wires as 1:120, 9:112, and 25:96, respectively. The potential and current density distributions are found to be inhomogeneous among zinc wires; firstly, the main anodic areas shift randomly among the zinc wires adjacent to steel wires, then transfer to the direction away from steel wires, and finally occur on the zinc wires farther. The similar heterogeneous phenomenon also appears on steel wires surface on which hydrogen evolution may take part in the cathodic process occurred. Meanwhile, the current density of water molecule reduction reaction decreases with the ratio of the surface area of steel wires to zinc wires increasing.

  6. Reliability of electrode wear compensation based on material removal per discharge in micro EDM milling

    DEFF Research Database (Denmark)

    Bissacco, Giuliano; Tristo, G.; Hansen, Hans Nørgaard

    2013-01-01

    This paper investigates the reliability of workpiece material removal per discharge (MRD) estimation for application in electrode wear compensation based on workpiece material removal. An experimental investigation involving discharge counting and automatic on the machine measurement of removed m...

  7. RETGEM with polyvinylchloride (PVC) electrodes

    CERN Document Server

    Razin, V I; Reshetin, A I; Filippov, S N

    2009-01-01

    This paper presents a new design of the RETGEM (Resistive Electrode Thick GEM) based on electrodes made of a polyvinylchloride material (PVC). Our device can operate with gains of 10E5 as a conventional TGEM at low counting rates and as RPC in the case of high counting rates without of the transit to the violent sparks. The distinct feature of present RETGEM is the absent of the metal coating and lithographic technology for manufacturing of the protective dielectric rms. The electrodes from PVC permit to do the holes by a simple drilling machine. Detectors on a RETGEM basis could be useful in many fields of an application requiring a more cheap manufacturing and safe operation, for example, in a large neutrino experiments, in TPC, RICH systems.

  8. Neural stimulation and recording electrodes.

    Science.gov (United States)

    Cogan, Stuart F

    2008-01-01

    Electrical stimulation of nerve tissue and recording of neural electrical activity are the basis of emerging prostheses and treatments for spinal cord injury, stroke, sensory deficits, and neurological disorders. An understanding of the electrochemical mechanisms underlying the behavior of neural stimulation and recording electrodes is important for the development of chronically implanted devices, particularly those employing large numbers of microelectrodes. For stimulation, materials that support charge injection by capacitive and faradaic mechanisms are available. These include titanium nitride, platinum, and iridium oxide, each with certain advantages and limitations. The use of charge-balanced waveforms and maximum electrochemical potential excursions as criteria for reversible charge injection with these electrode materials are described and critiqued. Techniques for characterizing electrochemical properties relevant to stimulation and recording are described with examples of differences in the in vitro and in vivo response of electrodes.

  9. Nonequilibrium Thermodynamics of Porous Electrodes

    CERN Document Server

    Ferguson, Todd R

    2012-01-01

    We review classical porous electrode theory and extend it to non-ideal active materials, including those capable of phase transformations. Using principles of non-equilibrium thermodynamics, we relate the cell voltage, ionic fluxes, and Faradaic charge-transfer kinetics to the variational electrochemical potentials of ions and electrons. The Butler-Volmer exchange current is consistently expressed in terms of the activities of the reduced, oxidized and transition states, and the activation overpotential is defined relative to the local Nernst potential. We also apply mathematical bounds on effective diffusivity to estimate porosity and tortuosity corrections. The theory is illustrated for a Li-ion battery with active solid particles described by a Cahn-Hilliard phase-field model. Depending on the applied current and porous electrode properties, the dynamics can be limited by electrolyte transport, solid diffusion and phase separation, or intercalation kinetics. In phase-separating porous electrodes, the model...

  10. Composite Electrodes for Electrochemical Supercapacitors

    Directory of Open Access Journals (Sweden)

    Yang QuanMin

    2010-01-01

    Full Text Available Abstract Manganese dioxide nanofibers with length ranged from 0.1 to 1 μm and a diameter of about 4–6 nm were prepared by a chemical precipitation method. Composite electrodes for electrochemical supercapacitors were fabricated by impregnation of the manganese dioxide nanofibers and multiwalled carbon nanotubes (MWCNT into porous Ni plaque current collectors. Obtained composite electrodes, containing 85% of manganese dioxide and 15 mass% of MWCNT, as a conductive additive, with total mass loading of 7–15 mg cm−2, showed a capacitive behavior in 0.5-M Na2SO4 solutions. The decrease in stirring time during precipitation of the nanofibers resulted in reduced agglomeration and higher specific capacitance (SC. The highest SC of 185 F g−1 was obtained at a scan rate of 2 mV s−1 for mass loading of 7 mg cm−2. The SC decreased with increasing scan rate and increasing electrode mass.

  11. Optimisation of manufacturing parameters for a Ni-Ag fuel cell electrode

    Energy Technology Data Exchange (ETDEWEB)

    Pishbin, M.H. [School of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, Tehran (Iran); Mohammadi, A.R. [Department of Mechanical Engineering, University of British Columbia, Vancouver (Canada); Nasri, M. [Information Technology Company of Iran, Tehran (Iran)

    2007-08-15

    The aim of this research is to optimise manufacturing parameters for a fuel cell electrode. The combination of nickel oxide, silver oxide and ammonium bicarbonate powders is used to produce the electrode. The main role of silver element is to increase the activity in the electrode. Ni-Ag electrode can be used in fuel cells as positive and negative electrodes. All powders are mixed in the benzene solution by a magnetic mixer and then compressed to form green electrode. The range of pressure in this step is between 40 and 160 MPa. The green electrode is sintered in hydrogen atmosphere through a tube furnace and then cooled to 200 C under argon atmosphere. The range of sintering temperature and time is 500-800 C and 10-60 min, respectively. Also, silver oxide and ammonium bicarbonate percentages are varied from 20 to 65 and 15 to 35%, respectively. All parameters including composition, pressure, sintering temperature and time are changed during electrode fabrication to achieve optimised properties in the electrode. So, it is necessary to perform several tests measuring porosity, surface area, density, weight loss, mechanical strength, shrinkage, exchange current density and metallographic photos. The optimum conditions of the electrode production resulting from this investigation include compacting pressure 60 MPa, sintering temperature 560 C, sintering time 15 min, silver oxide percentage 50% and ammonium bicarbonate percentage 27%. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  12. Metabolic Characteristics of a Glucose-Utilizing Shewanella oneidensis Strain Grown under Electrode-Respiring Conditions.

    Directory of Open Access Journals (Sweden)

    Gen Nakagawa

    Full Text Available In bioelectrochemical systems, the electrode potential is an important parameter affecting the electron flow between electrodes and microbes and microbial metabolic activities. Here, we investigated the metabolic characteristics of a glucose-utilizing strain of engineered Shewanella oneidensis under electrode-respiring conditions in electrochemical reactors for gaining insight into how metabolic pathways in electrochemically active bacteria are affected by the electrode potential. When an electrochemical reactor was operated with its working electrode poised at +0.4 V (vs. an Ag/AgCl reference electrode, the engineered S. oneidensis strain, carrying a plasmid encoding a sugar permease and glucose kinase of Escherichia coli, generated current by oxidizing glucose to acetate and produced D-lactate as an intermediate metabolite. However, D-lactate accumulation was not observed when the engineered strain was grown with a working electrode poised at 0 V. We also found that transcription of genes involved in pyruvate and D-lactate metabolisms was upregulated at a high electrode potential compared with their transcription at a low electrode potential. These results suggest that the carbon catabolic pathway of S. oneidensis can be modified by controlling the potential of a working electrode in an electrochemical bioreactor.

  13. Geometric Characteristics of Three Dimensional Reconstructed Anode Electrodes of Lithium Ion Batteries

    Directory of Open Access Journals (Sweden)

    Cheolwoong Lim

    2014-04-01

    Full Text Available The realistic three dimensional (3D microstructure of lithium ion battery (LIB electrode plays a key role in studying the effects of inhomogeneous microstructures on the performance of LIBs. However, the complexity of realistic microstructures imposes a significant computational cost on numerical simulation of large size samples. In this work, we used tomographic data obtained for a commercial LIB graphite electrode to evaluate the geometric characteristics of the reconstructed electrode microstructure. Based on the analysis of geometric properties, such as porosity, specific surface area, tortuosity, and pore size distribution, a representative volume element (RVE that retains the geometric characteristics of the electrode material was obtained for further numerical studies. In this work, X-ray micro-computed tomography (CT with 0.56 μm resolution was employed to capture the inhomogeneous porous microstructures of LIB anode electrodes. The Sigmoid transform function was employed to convert the initial raw tomographic images to binary images. Moreover, geometric characteristics of an anode electrode after 2400 cycles at the charge/discharge rate of 1 C were compared with those of a new anode electrode to investigate morphological change of the electrode. In general, the cycled electrode shows larger porosity, smaller tortuosity, and similar specific surface area compared to the new electrode.

  14. Nanoengineered membrane electrode assembly interface

    Science.gov (United States)

    Song, Yujiang; Shelnutt, John A

    2013-08-06

    A membrane electrode structure suitable for use in a membrane electrode assembly (MEA) that comprises membrane-affixed metal nanoparticles whose formation is controlled by a photochemical process that controls deposition of the metal nanoparticles using a photocatalyst integrated with a polymer electrolyte membrane, such as an ionomer membrane. Impregnation of the polymer membrane with the photocatalyst prior to metal deposition greatly reduces the required amount of metal precursor in the deposition reaction solution by restricting metal reduction substantially to the formation of metal nanoparticles affixed on or near the surface of the polymer membrane with minimal formation of metallic particles not directly associated with the membrane.

  15. Studies on the Electrochemical Characteristics of K2FeO4 Electrode

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Discharge performance of K2FeO4 electrode under different conditions was studied by the constant electric current discharge method. The electrochemical characteristics of K2FeO4 electrode were investigated for the first time by means of cyclic voltammetry. The results show that the K2FeO4 electrode made at moderate pressure (20 MPa) and discharged at lower current has better discharge performance. It is also found that K2FeO4 electrode is significantly rechargeable.

  16. PHOTOCHARGEABLE BEHAVIOR OF HYDROGEN STORAGE ALLOY ELECTRODE MODIFIED WITH TiO_2 NANOPARTICLES

    Institute of Scientific and Technical Information of China (English)

    王改田; 涂江平; 张博; 张文魁; 吴建波; 黄辉

    2004-01-01

    Photochargeable behavior of hydrogen storage alloy electrode modified with TiO_2 nanoparticles(MH/TiO_2) was investigated by measuring its photocharge-discharge characteristics. The results showed the MH/TiO_2 electrode could store light energy photoelectrochemically when it was illuminated. The potential of the MH/TiO_2 electrode could be charged to 0.843 V.The discharge time of the MH/TiO_2 electrode increased with increasing the illuminating time, The mechanism of photochargeable behavior of the MH/T...

  17. [Electrochemical reduction characteristics and mechanism of chlorinated hydrocarbon at the copper electrode].

    Science.gov (United States)

    Xu, Wen-Ying; Gao, Ting-Yao; Zhou, Rong-Feng; Ma, Lu-Ming

    2005-07-01

    The electrochemical reduction characteristics of chlorinated hydrocarbons were investigated by applying cyclic voltammetry technique. The reduction mechanism and reactivity of the chlorinated hydrocarbons at the copper electrodes were explored. The relation between the reductive reactivity at the copper electrode and the structures of this kind of compounds was discussed. The experimental results show that chlorinated paraffin hydrocarbons and a portion of chlorinated aromatic hydrocarbons could be reduced directly at the copper electrode; however, chlorinated aromatic hydrocarbons aren't easy to reduced directly at the copper electrode. The results provide a theoretical basis for the catalyzed iron inner electrolysis method.

  18. Charge transfer across the water/nitrobenzene interface bythree-electrode system

    Institute of Scientific and Technical Information of China (English)

    YUAN; Yi; (袁艺); GAO; Zhao; (高(目目空); ); ZHANG; Meiqin; (张美芹); ZHANG; Zhiquan; (张志权); SHAO; Yuanhua; (邵元华)

    2002-01-01

    A droplet of aqueous solution containing a certain molar ratio of redox couple is first attached onto a platinum electrode surface, then the resulting drop electrode is immersed into the organic solution containing very hydrophobic electrolyte. Combined with reference and counter electrodes, a classical three-electrode system has been constructed. Ion transfer (IT) and electron transfer (ET) are investigated systematically using three-electrode voltammetry. Potassium ion transfer and electron transfer between potassium ferricyanide in the aqueous phase and ferrocene in nitrobenzene are observed with potassium ferricyanide/potassium ferrocyanide as the redox couple. Meanwhile, the transfer reactions of lithium, sodium, potassium, proton and ammonium ions are obtained with ferric sulfate/ferrous sulfate as the redox couple. The formal transfer potentials and the standard Gibbs transfer energy of these ions are evaluated and consistent with the results obtained by a four-electrode system and other methods.

  19. Ion-selective electrodes with solid contact for heavy metals determination

    Directory of Open Access Journals (Sweden)

    Wardak C.

    2013-04-01

    Full Text Available Potentiometric properties of ion-selective electrodes with solid contact for lead, cadmium and zinc determination were investigated. The ionic liquids (ILs alkyl methyl imidazolium chlorides are used as lipophilic ionic additive to the membrane phase and as transducer media. The basic analytical parameters of the studied electrodes, such as the slope characteristic, the detection limit, response time, lifetime, selectivity coefficients against various inorganic cations as well as the dependence of the electrodes potential on pH were determined. The obtained electrode are characterized by good analytical parameters: theoretical characteristic slope, low detection limit, short response time and very long lifetime. The electrodes was successfully applied to the direct determination of lead, cadmium and zinc ions in waste water samples. The results obtained indicate that the electrodes provide a good alternative for the determination of these heavy metals in real samples.

  20. Preparation and properties of low-cost graphene counter electrodes for dye-sensitized solar cells

    Science.gov (United States)

    Wu, Qishuang; Shen, Yue; Wang, Qiandi; Gu, Feng; Cao, Meng; Wang, Linjun

    2013-12-01

    With the advantages of excellent electrical properties, high catalytic activity and low-cost preparation, Graphene is one of the most expected carbon materials to replace the expensive Pt as counter electrodes for dye-sensitized solar cells (DSSCs). In this paper, graphene counter electrodes were obtained by simple doctor-blade coating method on fluorine tin oxides (FTOs). The samples were investigated by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscope (SEM). Then the low-cost graphene electrodes were applied in typical sandwich-type DSSCs with TiO2 or ZnO as photoanodes, and their photoelectric conversion efficiency (η) were about 4.34% and 2.28%, respectively, which were a little lower than those of Pt electrodes but much higher than those of graphite electrodes. This law was consistent with the test results of electrochemical impedance spectroscopy (EIS). Low-cost graphene electrodes can be applied in DSSCs by process optimization.

  1. Solid electrodes in electroanalytical chemistry: present applications and prospects for high throughput screening of drug compounds.

    Science.gov (United States)

    Uslu, Bengi; Ozkan, Sibel A

    2007-08-01

    This review summarizes recent progress in the development and application of solid electrodes to the screening of pharmaceutical dosage forms and biological fluids. Recent trends and advances in the electroanalytical chemistry of solid electrodes, microelectrodes and electrochemical sensors are reviewed. The varieties of solid electrodes and their basic physico-chemical properties and some specific characteristics including some supramolecular phenomena at their surface are surveyed. This review also includes some selected designs and their applications. Despite many reviews about individual solid electrodes in the literature, this review offers the first comprehensive report on all forms of solid electrodes. Special attention is paid to the possibilities of solid electrodes in high throughput electroanalytical investigation of drug dosage forms and biological samples using modern electroanalytical techniques. Various selected studies on these subjects since 1996 are reviewed in this paper.

  2. Photorechargeable Properties of Metal Hydride-SrTiO3 Electrode

    Institute of Scientific and Technical Information of China (English)

    Wen Kui ZHANG; Xi Li TONG; Hui HUANG; Yong Ping GAN; Na HUANG

    2005-01-01

    A photosensitive metal hydride electrode was prepared by modification with perovskite-type SrTiO3 photocatalyst. The photorechargeable properties of the prepared electrodes were investigated by using electrochemical cyclic voltammetry and EIS measurements. The results showed that the modified electrode exhibited the obvious photorechargeable properties. The reduction current increased remarkably under the xeon light irradiation compared with the unmodified electrode. During the photocharging process, the potential of the modified electrode shifted quickly to negative direction and a potential plateau of about -0.90V (vs. Hg/HgO) occurred at the end of light irradiation. The corresponding discharge capacity of the electrode was about 5.4mAh/g.

  3. Correcting electrode modelling errors in EIT on realistic 3D head models.

    Science.gov (United States)

    Jehl, Markus; Avery, James; Malone, Emma; Holder, David; Betcke, Timo

    2015-12-01

    Electrical impedance tomography (EIT) is a promising medical imaging technique which could aid differentiation of haemorrhagic from ischaemic stroke in an ambulance. One challenge in EIT is the ill-posed nature of the image reconstruction, i.e., that small measurement or modelling errors can result in large image artefacts. It is therefore important that reconstruction algorithms are improved with regard to stability to modelling errors. We identify that wrongly modelled electrode positions constitute one of the biggest sources of image artefacts in head EIT. Therefore, the use of the Fréchet derivative on the electrode boundaries in a realistic three-dimensional head model is investigated, in order to reconstruct electrode movements simultaneously to conductivity changes. We show a fast implementation and analyse the performance of electrode position reconstructions in time-difference and absolute imaging for simulated and experimental voltages. Reconstructing the electrode positions and conductivities simultaneously increased the image quality significantly in the presence of electrode movement.

  4. Porous carbon-coated graphite electrodes for energy production from salinity gradient using reverse electrodialysis

    Science.gov (United States)

    Lee, Su-Yoon; Jeong, Ye-Jin; Chae, So-Ryong; Yeon, Kyeong-Ho; Lee, Yunkyu; Kim, Chan-Soo; Jeong, Nam-Jo; Park, Jin-Soo

    2016-04-01

    Performance of graphite foil electrodes coated by porous carbon black (i.e., Vulcan) was investigated in comparison with metal electrodes for reverse electrodialysis (RED) application. The electrode slurry that was used for fabrication of the porous carbon-coated graphite foil is composed of 7.2 wt% of carbon black (Vulcan X-72), 0.8 wt% of a polymer binder (polyvinylidene fluoride, PVdF), and 92.0 wt% of a mixing solvent (dimethylacetamide, DMAc). Cyclic voltammograms of both the porous carbon (i.e., Vulcan)-coated graphite foil electrode and the graphite foil electrode without Vulcan showed good reversibility in the hexacyanoferrate(III) (i.e., Fe(CN)63-) and hexacyanoferrate(II) (i.e., Fe(CN)64-) redox couple and 1 M Na2SO4 at room temperature. However, anodic and cathodic current of the Vulcan-coated graphite foil electrode was much higher than those of the graphite foil electrode. Using a bench-scale RED stack, the current-voltage polarization curve of the Vulcan-coated graphite electrode was compared to that of metal electrodes such as iridium (Ir) and platinum (Pt). From the results, it was confirmed that resistance of four different electrodes increased with the following order: the Vulcan-coated graphite foilVulcan-coated graphite foil showed 5-10% higher power density than the metal mesh electrodes. From the polarization curve of the Vulcan-coated graphite foil electrode, it was found that total resistance decreased as thickness and geometric surface area of the electrode increased.

  5. Analysis of SOFCs Using Reference Electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Finklea, H.; Chen, X.; Gerdes, K.; Pakalapati, S.; Celik, I.

    2013-01-01

    Reference electrodes are frequently applied to isolate the performance of one electrode in a solid oxide fuel cell. However, reference electrode simulations raise doubt to veracity of data collected using reference electrodes. The simulations predict that the reported performance for the one electrode will frequently contain performance of both electrodes. Nonetheless, recent reports persistently treat data so collected as ideally isolated. This work confirms the predictions of the reference electrode simulations on two SOFC designs, and to provides a method of validating the data measured in the 3-electrode configuration. Validation is based on the assumption that a change in gas composition to one electrode does not affect the impedance of the other electrode at open circuit voltage. This assumption is supported by a full physics simulation of the SOFC. Three configurations of reference electrode and cell design are experimentally examined using various gas flows and two temperatures. Impedance data are subjected to deconvolution analysis and equivalent circuit fitting and approximate polarization resistances of the cathode and anode are determined. The results demonstrate that the utility of reference electrodes is limited and often wholly inappropriate. Reported impedances and single electrode polarization values must be scrutinized on this basis.

  6. Electroenzymatic Reactions With Oxygen on Laccase-Modified Electrodes in Anhydrous (Pure) Organic Solvent

    DEFF Research Database (Denmark)

    Yarapolov, A.; Shleev, S.; Zaitseva, E.;

    2007-01-01

    glassy carbon and graphite electrodes with adsorbed laccase. The influence of the time for drying the laccase solution at the electrode surface on the electroreduction of oxygen was studied. Investigating the electroenzymatic oxidation reaction of catechol and hydroquinone in DMSO reveals the formation...

  7. Flexible active electrode arrays with ASICs that fit inside the rat’s spinal canal

    NARCIS (Netherlands)

    Giagka, V.; Demosthenous, A.; Donaldson, N.

    2015-01-01

    Epidural spinal cord electrical stimulation (ESCS) has been used as a means to facilitate locomotor recovery in spinal cord injured humans. Electrode arrays, instead of conventional pairs of electrodes, are necessary to investigate the effect of ESCS at different sites. These usually require a large

  8. Improved ceramic anodes for SOFCs with modified electrode/electrolyte interface

    DEFF Research Database (Denmark)

    Abdul Jabbar, Mohammed Hussain; Høgh, Jens Valdemar Thorvald; Zhang, Wei

    2012-01-01

    The electrode performance of solid oxide fuel cell anode with Pd nanoparticles at the interface of ScYSZ electrolyte and Sr0.94Ti0.9Nb0.1O3 (STN) electrode introduced in the form of metal functional layer have been investigated at temperatures below 600 °C. A metal functional layer consisting of ...

  9. Electronic transport properties of molecular junctions based on the direct binding of aromatic ring to electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Tran Nguyen, E-mail: lantran@ims.ac.jp

    2014-01-15

    Highlights: • Transport properties of molecular junction having direct binding of aromatic ring to electrode have been investigated. • The conductance of junction with sp-type electrode is higher than that of junction with sd-type electrode. • The rectifying mechanism critically depends on the nature of benzene–electrode coupling. • The p–n junction-like can be obtained even without heteroatom doping. • The negative differential resistance effect was observed for the case of sp-type electrode. - Abstract: We have used the non-equilibrium Green’s function in combination with the density functional theory to investigate the quantum transport properties of the molecular junctions including a terminated benzene ring directly coupled to surface of metal electrodes (physisorption). The other side of molecule was connected to electrode via thiolate bond (chemisorption). Two different electrodes have been studied, namely Cu and Al. Rectification and negative differential resistance behavior have been observed. We found that the electron transport mechanism is affected by the nature of benzene–electrode coupling. In other words, the transport mechanism depends on the nature of metallic electrode. Changing from sp- to sd-metallic electrode, the molecular junction changes from the Schottky to p–n junction-like diode. The transmission spectra, projected density of state, molecular projected self-consistent Hamiltonian, transmission eigenchannel, and Muliken population have been analyzed for explanation of electronic transport properties. Understanding the transport mechanism in junction having direct coupling of π-conjugate to electrode will be useful to design the future molecular devices.

  10. Performance Measurement of AMTEC Electrode

    Institute of Scientific and Technical Information of China (English)

    MA; Jun-ping; HE; Hu; LI; Si-jie; TANG; Xian; LUO; Zhi-fu

    2015-01-01

    Alkali metal thermal to electric converter(AMTEC)is a direct energy conversion device capable of near-Carnot efficiencies,and has demonstrated the performance of high power density,high current low voltage.Electrode is a key component of achieving high efficiency in an AMTEC device.A RhW alloy target was used for deposition

  11. Electrode structures of polymer-electrolyte fuel cells (PEFC). An electron microscopy approach to the characterization of the electrode structure of polymer electrolyte fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Scheiba, Frieder

    2009-01-28

    Polymer electrolyte fuel cells (PEFC) have a complex electrode structure, which usually consists of a catalyst, a catalyst support, a polymer electrolyte and pores. The materials used are largely amorphous, have a strong defective structure or have particle diameter of only a few nanometers. In the electrode the materials form highly disordered aggregated structures. Both aspects complicate a systematic structural analysis significantly. However, thorough knowledge of the electrode structure, is needed for systematic advancement of fuel cell technology and to obtain a better understanding of mass and charge carrier transport processes in the electrode. Because of the complex structure of the electrode, an approach based on the examination of electrode thin-sections by electron microscopy was chosen in this work to depicting the electrode structure experimentally. The present work presents these studies of the electrode structure. Some fundamental issues as the influence of the polymer electrolyte concentration and the polarity of the solvent used in the electrode manufacturing process were addressed. During the analysis particular attention was payed to the distribution and structure of the polymer electrolyte. A major problem to the investigations, were the low contrast between the polymer electrolyte, the catalyst support material and the embedding resin. Therefore, dilerent techniques were investigated in terms of their ability to improve the contrast. In this context, a computer-assisted acquisition procedure for energy filtered transmission electron microscopy (EF-TEM) was developed. The acquisition procedure permits a significant extension of the imageable sample. At the same time, it was possible to substantially reduce beam damage of the specimen and to minimize drift of the sample considerably. This allowed unambiguous identification of the polymer electrolyte in the electrode. It could further be shown, that the polymer electrolyte not only coats the

  12. 21 CFR 870.2360 - Electrocardiograph electrode.

    Science.gov (United States)

    2010-04-01

    ... electrode. (a) Identification. An electrocardiograph electrode is the electrical conductor which is applied to the surface of the body to transmit the electrical signal at the body surface to a processor...

  13. A method for making a hydrogen electrode

    Energy Technology Data Exchange (ETDEWEB)

    Ikeyama, M.; Ivaki, T.; Yanagikhara, N.

    1983-09-08

    A metallic grid is pressed to the surface of a foam metallic plate which contains powders of a compound which adsorb H2. The electrode is processed at the powder caking temperature. The electrode has a long service life.

  14. Fabrication and Characterisation of Membrane-Based Gold Electrodes

    DEFF Research Database (Denmark)

    Bakmand, Tanya; Kwasny, Dorota; Dimaki, Maria;

    2015-01-01

    and characterisation of the electrodes through cyclic voltammetry (CV). The continued porous nature of the membranes after metal deposition is documented and its robustness and stability is investigated. Furthermore, amperometric sensing of dopamine is demonstrated as a proof of concept to validate the usability...

  15. Electric and electrochemical properties of catalytically active oxygen electrode materials

    NARCIS (Netherlands)

    Burggraaf, A.J.; Dijk, van M.P.; Vries, de K.J.

    1986-01-01

    The electrical conductivity has been investigated of some oxygen ion and mixed conducting materials. Electrodes are prepared from thin sputtered layers of these oxides combined with a small Au or Pt strip. The kinetics of the oxygen reaction has been studied for temperatures of 820–1020 K and PO2 va

  16. Metal | polypyrrole battery with the air regenerated positive electrode

    Science.gov (United States)

    Grgur, Branimir N.

    2014-12-01

    Recharge characteristics of the battery based on the electrochemically synthesized polypyrrole cathode and aluminum, zinc, or magnesium anode in 2 M NH4Cl are investigated. It is shown that polypyrrole electrode can be regenerated by the reoxidation with the dissolved oxygen from the air. Using the polypyrrole synthesized on high surface graphite-felt electrode under modest discharge conditions, stable discharge voltage of 1.1 V is obtained. Such behavior is explained by the complex interaction of polypyrrole and hydrogen peroxide produced by the oxygen reduction reaction. The electrochemical characteristics are compared with the zinc-manganese dioxide and zinc-air systems.

  17. Oxygen reduction on teflon-bonded carbon electrode

    Institute of Scientific and Technical Information of China (English)

    周德璧; 黄可龙; 张世民

    2004-01-01

    Oxygen reduction on Teflon-bonded carbon gas diffusion electrode without catalyst in 6 mol/L KOH solution was investigated with acimpedance spectroscopy and other electrochemical techniques. The kinetic parameters were measured with an exchange current density of J0= 3.44 × 10-9 and a Tafel slope of 46 mV/dec in low overpotential range (-0.05 --0.14 V vs SCE), which are comparable with those reported on carbon supported platinum electrode. The reaction mechanism of OR and the active effect of carbon black were examined.

  18. Voltammetric determination of copper(II) using antimony film electrodes

    OpenAIRE

    Ashrafi, Amir Mansoor; Husáková, Lenka; Vytřas, Karel

    2012-01-01

    Possibility of determination of Cu(II) at antimony modified carbon paste electrode and its application in determination of trace amount of copper in real sample has been investigated. According to obtained results, it was found that SbF-CPE can be used for these purposes successfully. Both detection limit of 1.45 ppb (evaluated as 3σ) and RSD 4.8 (for 10 ppb Cu and 10 different measurements) were also evaluated. Antimony-based electrodes are environmentally friendly which is their most import...

  19. Characteristic electron transport on pyridine-linked molecular devices with graphene nanoribbons electrodes and gold electrodes

    Science.gov (United States)

    Li, Jie; Zhou, Yi; Zhang, Leining; Li, Hui

    2016-09-01

    The electrodes in the molecular devices play a crucial role in creating functional organic electronic devices. We employed the first-principles calculations to investigate the conjugated pyridine-terminated molecule-4, 4‧-vinylenedipyridine attached to monolayer zigzag graphene nanoribbons (ZGNRs) and Au electrodes. Results show that the ZGNRs-based device exhibits excellent electrical properties. It has larger equilibrium conductance or stronger transmission capacity due to higher strength of individual channel and stronger delocalization of electronic states at the Fermi level. The transmission of two devices near the Fermi level is influenced by resonant electron transport through the discrete energy and the edge states. Comparatively, different from the rising trend of gold-based device with the increasing voltage, the current of the device with ZGNRs electrodes changes in a completely different way with the augment of the applied voltage, exhibiting a negative differential resistance effect unexpectedly. The changing trends of the current through two devices are elucidated by the evolution of the transmission peak nearest to the Fermi level.

  20. 21 CFR 890.1175 - Electrode cable.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Electrode cable. 890.1175 Section 890.1175 Food... DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Diagnostic Devices § 890.1175 Electrode cable. (a) Identification. An electrode cable is a device composed of strands of insulated electrical conductors...

  1. Voltammetry at porous electrodes: A theoretical study

    CERN Document Server

    Barnes, Edward O; Li, Peilin; Compton, Richard G

    2014-01-01

    Theory is presented to simulate both chronoamperometry and cyclic voltammetry at porous electrodes fabricated by means of electro-deposition around spherical templates. A theoretical method to extract heterogeneous rate constants for quasireversible and irreversible systems is proposed by the approximation of decoupling of the diffusion within the porous electrode and of bulk diffusion to the electrode surface.

  2. Membrane electrode assembly for a fuel cell

    Science.gov (United States)

    Prakash, Surya (Inventor); Narayanan, Sekharipuram R. (Inventor); Atti, Anthony (Inventor); Olah, George (Inventor); Smart, Marshall C. (Inventor)

    2006-01-01

    A catalyst ink for a fuel cell including a catalytic material and poly(vinylidene fluoride). The ink may be applied to a substrate to form an electrode, or bonded with other electrode layers to form a membrane electrode assembly (MEA).

  3. Reducing Insertion Sites of Penetrating Multipolar Shaft Electrodes by Double Side Electrode Arrangement

    Science.gov (United States)

    2007-11-02

    Abstract-Micromachined devices with substrate-integrated elec- trodes are the key component in implantable microdevices for recording neuronal ...INSERTION SITES OF PENETRATING MULTIPOLAR SHAFT ELECTRODES BY DOUBLE SIDE ELECTRODE ARRANGEMENT T.Stieglitz1, P. Heiduschka2, M. Schuettler1, M. Gross1...and Subtitle Reducing Insertion Sites of Penetrating Multipolar Shaft Electrodes by Double Side Electrode Arrangement Contract Number Grant Number

  4. Measurement of noise and impedance of dry and wet textile electrodes, and textile electrodes with hydrogel.

    Science.gov (United States)

    Puurtinen, Merja M; Komulainen, Satu M; Kauppinen, Pasi K; Malmivuo, Jaakko A V; Hyttinen, Jari A K

    2006-01-01

    Textile sensors, when embedded into clothing, can provide new ways of monitoring physiological signals, and improve the usability and comfort of such monitoring systems in the areas of medical, occupational health and sports. However, good electrical and mechanical contact between the electrode and the skin is very important, as it often determines the quality of the signal. This paper introduces a study where the properties of dry textile electrodes, textile electrodes moistened with water, and textile electrodes covered with hydrogel were studied with five different electrode sizes. The aim was to study how the electrode size and preparation of the electrode (dry electrode/wet electrode/electrode covered with hydrogel membrane) affect the measurement noise, and the skin-electrode impedance. The measurement noise and skin-electrode impedance were determined from surface biopotential measurements. These preliminary results indicate that noise level increases as the electrode size decreases. The noise level is high in dry textile electrodes, as expected. Yet, the noise level of wet textile electrodes is quite low and similar to that of textile electrodes covered with hydrogel. Hydrogel does not seem to improve noise properties, however it may have effects on movement artifacts. Thus, it is feasible to use textile embedded sensors in physiological monitoring applications when moistening or hydrogel is applied.

  5. Single electrode dynamic clamp with StdpC.

    Science.gov (United States)

    Samu, David; Marra, Vincenzo; Kemenes, Ildiko; Crossley, Michael; Kemenes, György; Staras, Kevin; Nowotny, Thomas

    2012-10-15

    Dynamic clamp is a powerful approach for electrophysiological investigations allowing researchers to introduce artificial electrical components into target neurons to simulate ionic conductances, chemical or electrotonic inputs or connections to other cells. Due to the rapidly changing and potentially large current injections during dynamic clamp, problematic voltage artifacts appear on the electrode used to inject dynamic clamp currents into a target neuron. Dynamic clamp experiments, therefore, typically use two separate electrodes in the same cell, one for recording membrane potential and one for injecting currents. The requirement for two independent electrodes has been a limiting factor for the use of dynamic clamp in applications where dual recordings of this kind are difficult or impossible to achieve. The recent development of an active electrode compensation (AEC) method has overcome some of these prior limitations, permitting artifact-free dynamic clamp experimentation with a single electrode. Here we describe an AEC method for the free dynamic clamp software StdpC. The AEC component of StdpC is the first such system implemented for the use of non-expert users and comes with a set of semi-automated configuration and calibration procedures that facilitate its use. We briefly introduce the AEC method and its implementation in StdpC and then validate it with an electronic model cell and in two different biological preparations.

  6. Incorporation of indium tin oxide nanoparticles in PEMFC electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Wolz, Andre [Renewable Energies Group, Institute for Materials Science, Technische Universitaet Darmstadt (Germany); CRP Henri Tudor, Department of Advanced Materials and Structures, Esch-sur-Alzette (Luxembourg); Zils, Susanne; Ruch, David; Michel, Marc [CRP Henri Tudor, Department of Advanced Materials and Structures, Esch-sur-Alzette (Luxembourg); Kotov, Nicholas [University of Michigan, Department of Chemical Engineering, Ann Arbor, MI (United States); Roth, Christina [Renewable Energies Group, Institute for Materials Science, Technische Universitaet Darmstadt (Germany); Institute for Applied Materials (IAM)-Energy Storage Systems (ESS), Eggenstein-Leopoldshafen (Germany)

    2012-05-15

    Carbon materials suffer from corrosion at the cathode of polymer electrolyte membrane fuel cells (PEMFCs). In the presence of water, carbon support materials are oxidized to carbon dioxide even at low potentials. Hence, nowadays it is very fashionable to look for alternative support materials, like oxides or conductive polymers. To gain the maximum performance for a new material one should also consider an appropriate electrode structure. This study shows the results for the incorporation of nanosized alternative support materials into advanced electrode architectures. Commercially available indium tin oxide (ITO) nanoparticles (<50 nm) are used as support for Pt nanoparticles in combination with Nafion-coated multi-walled carbon nanotubes (MWCNTs) on the cathode side of a PEMFC. The MWCNTs promote a high electronic conductivity and help to form a porous network, which could accommodate the Pt/ITO nanoparticles. The microscopic investigations show a homogeneous electrode structure composed of Pt/ITO and MWCNT/Nafion multilayer. Single cell measurements show a maximum power density of 73 mW cm{sup -2} and a Pt utilization of 1468 mW mg{sub Pt}{sup -1} for the cathode. The performance data and the Pt utilization are comparable to a standard Pt/carbon black electrode possessing the same Pt loading in the electrode. Beside this, it is shown for the first time that ITO serves as support material under real fuel cell conditions. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Iron-substituted AB5-type MH electrode

    Indian Academy of Sciences (India)

    Sumita Srivastava; R K Upadhyaya

    2013-12-01

    The present investigation is aimed to study MmNi5-type (Mm = Mischmetal) hydrogen storage alloys with composition, Mm0.8La0.2Ni3.7Al0.38Co0.3Mn0.6−Mo0.02Fe ( = 0, 0.1, 0.2 and 0.3). The alloys are synthesized by radio-frequency inductionmelting. To study their electrochemical properties viameasurements of discharge capacity, activation process, rate capability and cyclic stability, electrodes are fabricated using as-synthesized and annealed version of the alloys. The maximum discharge capacity is recorded as 288 mAhg-1 for the iron concentration, = 0.1, as compared to 270 mAhg-1 for the alloy electrode without iron. Similarly, 99% cyclic stability is observed in annealed alloy electrode ( = 0.1) as compared to 78% in the alloy electrode without iron. Hence, small amount of iron-substitution ( = 0.1) in the alloy is found to improve the electrochemical properties. This improvement is thought to be due to less pulverization of the alloy in electrochemically-cycled alloy, as confirmed through structural and microstructural characterizations carried out by X-ray diffraction phase analysis and scanning electron microscopy of as-fabricated and electrochemically-cycled electrodes.

  8. Simulation of Dual-Electrode Capacitively Coupled Plasma Discharges

    Science.gov (United States)

    Lu, Yijia; Ji, Linhong; Cheng, Jia

    2016-12-01

    Dual-electrode capacitively coupled plasma discharges are investigated here to lower the non-uniformity of plasma density. The dual-electrode structure proposed by Jung splits the electrode region and increases the flexibility of fine tuning non-uniformity. Different RF voltages, frequencies, phase-shifts and electrode areas are simulated and the influences are discussed. RF voltage and electrode area have a non-monotonic effect on non-uniformity, while frequency has a monotonic effect. Phase-shift has a cyclical influence on non-uniformity. A special combination of 224 V voltage and 11% area ratio with 10 MHz lowers the non-uniformity of the original set (200 V voltage and 0% area ratio with 10 MHz) by 46.5%. The position of the plasma density peak at the probe line has been tracked and properly tuning the phase-shift can obtain the same trace as tuning frequency or voltage. supported by National Natural Science Foundation of China (No. 51405261)

  9. Flow electrification characteristics of transformer oil by rotating electrode systems

    Energy Technology Data Exchange (ETDEWEB)

    Jagadish, R.; Poovamma, P.K. [Central Power Research Inst., Bangalore (India)

    1995-07-01

    Flow electrification has been found to be the principal cause of a number of failures of forced oil cooled power transformers. Flow charging characteristics of oil/cellulose system with factors like electrode configuration, electrode material, presence of Benzotriazole (BTA), metallic contaminants and Copper coils were investigated for paraffinic oil by employing rotating electrode system. A few hydrodynamic parameters viz. Reynolds number, boundary layer thickness and friction factor were correlated with flow charging characteristics of oil for varying temperatures and concentrations of BTA. With lower concentrations of BTA in oil viz. 10 ppm and 25 ppm a marginal reduction in flow charging of oil was noticed, but about 40% reduction was observed with 150 ppm of BTA. A significant reduction in the flow charging characteristics of untreated and BTA treated oils was also observed in the presence of Copper coils and metallic particle contaminants.

  10. Graphene oxide - Polyvinyl alcohol nanocomposite based electrode material for supercapacitors

    Science.gov (United States)

    Pawar, Pranav Bhagwan; Shukla, Shobha; Saxena, Sumit

    2016-07-01

    Supercapacitors are high capacitive energy storage devices and find applications where rapid bursts of power are required. Thus materials offering high specific capacitance are of fundamental interest in development of these electrochemical devices. Graphene oxide based nanocomposites are mechanically robust and have interesting electronic properties. These form potential electrode materials efficient for charge storage in supercapacitors. In this perspective, we investigate low cost graphene oxide based nanocomposites as electrode material for supercapacitor. Nanocomposites of graphene oxide and polyvinyl alcohol were synthesized in solution phase by integrating graphene oxide as filler in polyvinyl alcohol matrix. Structural and optical characterizations suggest the formation of graphene oxide and polyvinyl alcohol nanocomposites. These nanocomposites were found to have high specific capacitance, were cyclable, ecofriendly and economical. Our studies suggest that nanocomposites prepared by adding 0.5% wt/wt of graphene oxide in polyvinyl alcohol can be used an efficient electrode material for supercapacitors.

  11. ENOBIO dry electrophysiology electrode; first human trial plus wireless electrode system.

    Science.gov (United States)

    Ruffini, Giulio; Dunne, Stephen; Farres, Esteve; Cester, Ivan; Watts, Paul C P; Silva, S P; Grau, Carles; Fuentemilla, Lluis; Marco-Pallares, Josep; Vandecasteele, Bjorn

    2007-01-01

    This paper presents the results of the first human trials with the ENOBIO electrophysiology electrode prototype plus the initial results of a new wireless prototype with flexible electrodes based on the same platform. The results indicate that a dry active electrode that employs a CNT array as the electrode interface can perform on a par with traditional "wet" electrodes for the recording of EEG, ECG, EOG and EMG. We also demonstrate a new platform combining wireless technology plus flexible electrodes for improved comfort for applications that take advantage of the dry electrode concept.

  12. An electrode with Ni(II) loaded analcime zeolite catalyst for the electrooxidation of methanol

    Institute of Scientific and Technical Information of China (English)

    Seyed Naser Azizi; Shahram Ghasemi; Neda Salek Gilani

    2014-01-01

    There is a high overvoltage in the oxidation of methanol in fuel cells, and so modified electrodes are used to decrease it. A modified electrode that used Ni(II) loaded analcime zeolite to catalyze the electrooxidation of methanol in alkaline solution was proposed. Analcime zeolite was synthesized by hydrothermal synthesis, and Ni(II) ions were incorporated into the analcime structure, which was then mixed with carbon paste to prepare modified electrode. The electrocatalytic oxidation of methanol on the surface of the modified electrode in alkaline solution was investigated by cyclic voltammetry and chronoamperometry. The effects of the scan rate of the potential, concentration of methanol, and amount of zeolite were investigated. The rate constant for the catalytic reaction of methanol was 6 × 103 cm3 mol-1 s-1 from measurements using chronoamperometry. The proposed electrode significantly improved the electron transfer rate and decreased the overpotential for methanol oxidation.

  13. Three-dimensional ordered macroporous platinum-based electrode for methanol oxidation

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In this paper, three-dimensional ordered macroporous platinum catalysts with high real surface area were synthesized using the inverted colloidal crystals template technique and have been employed for the electrooxidation of methanol. The morphology and electrocatalytic behavior of the porous Pt electrodes were investigated with atomic force microscopy and electrochemical techniques. For the same amount of Pt deposited, the real surface areas of the electrodes are 9.16 and 8.00 cm2 for the porous electrodes with pore size of 320 and 500 nm respectively, which are more than 5 times larger than the directly deposited Pt electrode (1.4 cm2). The pore size effect on the methanol electrooxidation was investigated by testing low concentration solution of methanol and porous materials with different pore sizes. The synthesized macroporous Pt electrode shows high stability toward the electrooxidation of methanol and is promising for the direct methanol fuel cell.

  14. Enhanced DNA sequencing performance through edge-hydrogenation of graphene electrodes

    CERN Document Server

    He, Yuhui; Grigoriev, Anton; Ahuja, Rajeev; Long, Shibing; Huo, ZongLiang; Liu, Ming

    2010-01-01

    We propose using graphene electrodes with hydrogenated edges for solid-state nanopore-based DNA sequencing, and perform molecular dynamics simulations in conjunction with electronic transport calculations to explore the potential merits of this idea. The results of our investigation show that, compared to the unhydrogenated system, edge-hydrogenated graphene electrodes facilitate the temporary formation of H-bonds with suitable atomic sites in the translocating DNA molecule. As a consequence, the average conductivity is drastically raised by about 3 orders of magnitude while exhibiting significantly reduced statistical variance. We have furthermore investigated how these results are affected when the distance between opposing electrodes is varied and have identified two regimes: for narrow electrode separation, the mere hindrance due to the presence of protruding hydrogen atoms in the nanopore is deemed more important, while for wider electrode separation, the formation of H-bonds becomes the dominant effect....

  15. Determination of the Trigger-Electrode Position for the Field-Distortion Spark Gap

    Institute of Scientific and Technical Information of China (English)

    汪沨; 许日; 王琦; 邱毓昌

    2002-01-01

    The optimal axial position of the trigger-electrode of the field-distortion spark gap is investigated through electric field calculation. The electric fields of the gap are calculated when locating trigger-electrode at different positions. It is shown that if the distance d between the trigger electrode and the low electric potential electrode is greater than 1.3 mm, the maximum field intensity occurs at the edge of the trigger-electrode, which will facilitate the generation of multi-channel discharge. According to calculated results, the working characteristics of the gap is investigated and it shows that when d = 1.4 mm the field distortion gap can be triggered reliably.

  16. Determination of the trigger-electrode position for the field-distortion spark gap

    CERN Document Server

    Wang Feng; Qiu Yu Chang; Xu Ri

    2002-01-01

    The optimal axial position of the trigger-electrode of the field-distortion spark gap is investigated through electric field calculation. The electric fields of the gap are calculated when locating trigger-electrode at different positions. It is shown that if the distance d between the trigger electrode and the low electric potential electrode is greater than 1.3 mm, the maximum field intensity occurs at the edge of the trigger-electrode, which will facilitate the generation of multi-channel discharge. According to calculated results, the working characteristics of the gap is investigated and it shows that when d = 1.4 mm the field distortion gap can be triggered reliably

  17. The zinc electrode - Its behaviour in the nickel oxide-zinc accumulator

    Science.gov (United States)

    Certain aspects of zinc electrode reaction and behavior are investigated in view of their application to batteries. The properties of the zinc electrode in a battery system are discussed, emphasizing porous structure. Shape change is emphasized as the most important factor leading to limited battery cycle life. It is shown that two existing models of shape change based on electroosmosis and current distribution are unable to consistently describe observed phenomena. The first stages of electrocrystallization are studied and the surface reactions between the silver substrate and the deposited zinc layer are investigated. The reaction mechanism of zinc and amalgamated zinc in an alkaline electrolyte is addressed, and the batter system is studied to obtain information on cycling behavior and on the shape change phenomenon. The effect on cycle behavior of diferent amalgamation techniques of the zinc electrode and several additives is addressed. Impedance measurements on zinc electrodes are considered, and battery behavior is correlated with changes in the zinc electrode during cycling.

  18. Kinetics of CO2 reduction in KOH/methanol electrolyte on Pb electrode

    Institute of Scientific and Technical Information of China (English)

    SONG Shuang; HE Zhi-qiao; YE Jie-xu; CHEN Jian-meng

    2007-01-01

    The electrochemical reduction of CO2 on a Pb electrode was investigated in 0.1 mol/L KOH/methanol electrolyte at different temperatures and pressures. A graphite electrode was employed as the counter electrode, and an AglAgCl ( sat. KCl) electrode was used as the reference electrode. The Tafel plots of the products by the electrochemical reduction of CO2 showed that the formation process of HCOOH differed from that of CO and the reduction of CO2 was not limited by the diffusion of CO2 in the investigated potential range. Kinetic analysis indicated that the reaction orders were 0.573 for electrochemical reduction of CO2 to CO and 0. 671 for CO2 to HCOOH in the cathodic direction.

  19. Fluoride Removal From Drinking Water by Electrocoagulation Using Iron and Aluminum Electrodes

    Directory of Open Access Journals (Sweden)

    Takdastan

    2014-07-01

    Full Text Available Background Existence of fluoride in drinking water above the permissible level causes human skeletal fluorosis. Objectives Electrocoagulation by iron and aluminum electrodes was proposed for removing fluoride from drinking water. Materials and Methods Effects of different operating conditions such as treatment time, initial pH, applied voltage, type and number of electrodes, the spaces between aluminum and iron electrodes, and energy consumption during electrocoagulation were investigated in the batch reactor. Variable concentrations of fluoride solution were prepared by mixing proper amounts of sodium fluoride with deionized water. Results Experimental results showed that aluminum electrode is more effective in fluoride removal than iron, as in 40 minutes and initial pH of 7.5 at 20 V, the fluoride removal process reached to 97.86%. The final recommendable limit of fluoride (1.5 mg/L was obtained in 10 minutes at 20 V with the aluminum electrode. Conclusions In electrocoagulation with iron and aluminum electrodes, increase of voltage, number of electrodes and reaction time as well as decrease of the spaces between electrodes, enhanced the fluoride removal efficiency from drinking water. In addition the effect of pH and initial concentration of fluoride varied with types of electrodes.

  20. Oscillatory motion of water droplets in kerosene above co-planar electrodes in microfluidic chips

    Directory of Open Access Journals (Sweden)

    Pavel Beránek

    2014-06-01

    Full Text Available We experimentally observed oscillatory motion of water droplets in microfluidic systems with coplanar microelectrodes under imposed DC electric fields. Two-electrode arrangement with no bipolar electrode and eight-electrode arrangement with six bipolar microelectrodes were investigated. Kerosene was used as the continuous phase. We studied the dependences of the oscillation frequency on the electric field intensity and ionic strength of the water phase. We found that the electric field dependence is strongly nonlinear and discussed possible reasons of this phenomenon, e.g., the droplet deformation at electrode edges that affects the charge transfer between the electrode and droplet or the interplay between the Coulomb force on free charge and the dielectrophoretic force. Our experiments further revealed that the oscillation frequency decreases with growing salt concentration in the two-electrode arrangement, but increases in the eight-electrode arrangement, which was attributed to surface tension related processes and electrochemical processes on the bipolar electrodes. Finally, we analyzed the effects of the electric field on the oscillatory motion by means of a simplified mathematical model. It was shown that the electric force imposed on the droplet charge is the key factor to induce the oscillations and the dielectrophoretic force significantly contributes to the momentum transfer at the electrode edges. For the same electric field strength, the model is able to predict the same oscillation frequency as that observed in the experiments.

  1. Effect of top electrode material on radiation-induced degradation of ferroelectric thin film structures

    Science.gov (United States)

    Brewer, Steven J.; Deng, Carmen Z.; Callaway, Connor P.; Paul, McKinley K.; Fisher, Kenzie J.; Guerrier, Jonathon E.; Rudy, Ryan Q.; Polcawich, Ronald G.; Jones, Jacob L.; Glaser, Evan R.; Cress, Cory D.; Bassiri-Gharb, Nazanin

    2016-07-01

    The effects of gamma irradiation on the dielectric and piezoelectric responses of Pb[Zr0.52Ti0.48]O3 (PZT) thin film stacks were investigated for structures with conductive oxide (IrO2) and metallic (Pt) top electrodes. The samples showed, generally, degradation of various key dielectric, ferroelectric, and electromechanical responses when exposed to 2.5 Mrad (Si) 60Co gamma radiation. However, the low-field, relative dielectric permittivity, ɛr, remained largely unaffected by irradiation in samples with both types of electrodes. Samples with Pt top electrodes showed substantial degradation of the remanent polarization and overall piezoelectric response, as well as pinching of the polarization hysteresis curves and creation of multiple peaks in the permittivity-electric field curves post irradiation. The samples with oxide electrodes, however, were largely impervious to the same radiation dose, with less than 5% change in any of the functional characteristics. The results suggest a radiation-induced change in the defect population or defect energy in PZT with metallic top electrodes, which substantially affects motion of internal interfaces such as domain walls. Additionally, the differences observed for stacks with different electrode materials implicate the ferroelectric-electrode interface as either the predominant source of radiation-induced effects (Pt electrodes) or the site of healing for radiation-induced defects (IrO2 electrodes).

  2. A Handy EEG Electrode Set for patients suffering from altered mental state.

    Science.gov (United States)

    Lepola, Pasi; Myllymaa, Sami; Töyräs, Juha; Hukkanen, Taina; Mervaala, Esa; Määttä, Sara; Lappalainen, Reijo; Myllymaa, Katja

    2015-12-01

    Although electroencephalography (EEG) is an important diagnostic tool for investigating patients with unexplained altered mental state (AMS), recording of emergency EEG is not a clinical routine. This is mainly due to the cumbersome electrode solutions. A Handy EEG Electrode Set consists of ten EEG, two EOG, two ground and two commutative reference hydrogel-coated silver wire electrodes attached to a thin polyester carrier film. The clinical usefulness of the Handy EEG Electrode Set was tested in 13 patients (five females, eight males) with AMS. EEG recordings were conducted at the same time with a standard 10-20 electrode set. The registration in the first patient case without the behind-ear electrodes (T9 and T10), indicated that these electrodes are very crucial to provide clinically relevant information from posterior regions of brain. In following 12 cases, the sensitivity and specificity for detecting EEG abnormality based on the Handy EEG Electrode Set recordings were 83 and 100 %, respectively. The Handy EEG Electrode Set proved to be easy to use and to provide valuable information for the neurophysiological evaluation of a patient suffering from AMS. However, further studies with larger number of patients are warranted to clarify the true diagnostic accuracy and applicability of this approach.

  3. Study on the Effect of the Three-Dimensional Electrode in Degradation of Methylene Blue by Lithium Modified Rectorite

    Directory of Open Access Journals (Sweden)

    Jian Huang

    2016-01-01

    Full Text Available This study presents the electrochemical degradation of methylene blue (MB wastewater in a synthetic solution using three-dimensional particle electrodes. The novel particle electrodes were fabricated in this work using the lithium modified rectorite (Li-REC. The adsorption property of the fabricated particle electrodes was studied in a series of experiments. The optimum electrochemical operating conditions of plate distance, cell voltage, and concentration of electrolyte were 2 cm, 9 V, and 0.06 mol L−1, respectively. It was also found that microwave irradiation can effectively improve the adsorption property and electrical property of the fabricated electrodes. In addition, the scanning electron microscope (SEM of the fabricated electrodes was investigated. The experimental results revealed the order of adsorption property and electrical property of the fabricated electrodes. So, fabricated electrodes are not only of low cost and mass produced, but also efficient to achieve decolorization of MB solution.

  4. Study on the Effect of the Three-Dimensional Electrode in Degradation of Methylene Blue by Lithium Modified Rectorite.

    Science.gov (United States)

    Huang, Jian; Ming, Yin'an; Du, Ying; Wang, Yingru; Wang, Ci'en

    2016-01-01

    This study presents the electrochemical degradation of methylene blue (MB) wastewater in a synthetic solution using three-dimensional particle electrodes. The novel particle electrodes were fabricated in this work using the lithium modified rectorite (Li-REC). The adsorption property of the fabricated particle electrodes was studied in a series of experiments. The optimum electrochemical operating conditions of plate distance, cell voltage, and concentration of electrolyte were 2 cm, 9 V, and 0.06 mol L(-1), respectively. It was also found that microwave irradiation can effectively improve the adsorption property and electrical property of the fabricated electrodes. In addition, the scanning electron microscope (SEM) of the fabricated electrodes was investigated. The experimental results revealed the order of adsorption property and electrical property of the fabricated electrodes. So, fabricated electrodes are not only of low cost and mass produced, but also efficient to achieve decolorization of MB solution.

  5. From permanent magnets to rechargeable hydride electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Willems, J.J.G.; Buschow, K.H.J.

    1987-02-15

    A brief historical survey is given of how the study of coercitivity mechanisms in SmCo/sub 5/ permanent-magnet materials eventually led to the discovery of the favourable hydrogen sorption properties of the compound LaNi/sub 5/. It is shown how continued research by many investigators dealing with a variety of different physical and chemical properties has resulted in an advanced understanding of some of the principles that govern hydrogen absorption and which are responsible for the changes in physical properties that accompany it. The problems associated with various applications of LaNi/sub 5/-based hydrogen-storage materials are also briefly discussed. A large part of this paper is devoted to the applicability of LaNi/sub 5/-type materials in batteries. Research in this area has resulted in the development of a new type of rechargeable battery: the nickel-hydride cell. This battery can be charged and discharged at high rates and is relatively insensitive to overcharging and overdischarging. Special attention is given to the nature of the electrode degradation process and the effect of composition variations in LaNi/sub 5/-related materials on the lifetime of the corresponding hydride electrodes when subjected to severe electrochemical charge-discharge cycles.

  6. Long life lithium batteries with stabilized electrodes

    Science.gov (United States)

    Amine, Khalil; Liu, Jun; Vissers, Donald R.; Lu, Wenquan

    2009-03-24

    The present invention relates to non-aqueous electrolytes having electrode stabilizing additives, stabilized electrodes, and electrochemical devices containing the same. Thus the present invention provides electrolytes containing an alkali metal salt, a polar aprotic solvent, and an electrode stabilizing additive. In some embodiments the additives include a substituted or unsubstituted cyclic or spirocyclic hydrocarbon containing at least one oxygen atom and at least one alkenyl or alkynyl group. When used in electrochemical devices with, e.g., lithium manganese oxide spinel electrodes or olivine or carbon-coated olivine electrodes, the new electrolytes provide batteries with improved calendar and cycle life.

  7. Method for manufacturing magnetohydrodynamic electrodes

    Science.gov (United States)

    Killpatrick, Don H.; Thresh, Henry R.

    1982-01-01

    A method of manufacturing electrodes for use in a magnetohydrodynamic (MHD) generator comprising the steps of preparing a billet having a core 10 of a first metal, a tubular sleeve 12 of a second metal, and an outer sheath 14, 16, 18 of an extrusile metal; evacuating the space between the parts of the assembled billet; extruding the billet; and removing the outer jacket 14. The extruded bar may be made into electrodes by cutting and bending to the shape required for an MDH channel frame. The method forms a bond between the first metal of the core 10 and the second metal of the sleeve 12 strong enough to withstand a hot and corrosive environment.

  8. A dry electrode for EEG recording.

    Science.gov (United States)

    Taheri, B A; Knight, R T; Smith, R L

    1994-05-01

    This paper describes the design, fabrication and testing of a prototype dry surface electrode for EEG signal recording. The new dry electrode has the advantages of no need for skin preparation or conductive paste, potential for reduced sensitivity to motion artifacts and an enhanced signal-to-noise ratio. The electrode's sensing element is a 3 mm stainless steel disk which has a 2000 A (200 nm) thick nitride coating deposited onto one side. The back side of the disk is attached to an impedance converting amplifier. The prototype electrode was mounted on a copper plate attached to the scalp by a Velcro strap. The performance of this prototype dry electrode was compared to commercially available wet electrodes in 3 areas of electroencephalogram (EEG) recording: (1) spontaneous EEG, (2) sensory evoked potentials, and (3) cognitive evoked potentials. In addition to the raw EEG, the power spectra of the signals from both types of electrodes were also recorded. The results suggest that the dry electrode performs comparably to conventional electrodes for all types of EEG signal analysis. This new electrode may be useful for the production of high resolution surface maps of brain activity where a large number of electrodes or prolonged recording times are required.

  9. Low-voltage FIB/SEM Tomography for 3D Microstructure Evolution of LiFePO4/C Electrode

    DEFF Research Database (Denmark)

    Scipioni, Roberto; Jørgensen, Peter Stanley; Ngo, Duc-The

    2015-01-01

    This work presents an investigation of the degradation mechanisms that occur in LiFePO4/C battery electrodes during charge/discharge cycling. Impedance spectra were measured on a fresh electrode and an electrode aged by cycling. The spectra were modeled with an equivalent circuit which indicates...

  10. Electrode materials for rechargeable battery

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Christopher; Kang, Sun-Ho

    2015-09-08

    A positive electrode is disclosed for a non-aqueous electrolyte lithium rechargeable cell or battery. The electrode comprises a lithium containing material of the formula Na.sub.yLi.sub.xNi.sub.zMn.sub.1-z-z'M.sub.z'O.sub.d, wherein M is a metal cation, x+y>1, 0electrode material can be synthesized using an ion-exchange reaction with a lithium salt in an organic-based solvent to partially replace sodium ions of a precursor material with lithium ions.

  11. Stretchable Micro-Electrode Array

    Energy Technology Data Exchange (ETDEWEB)

    Maghribi, M; Hamilton, J; Polla, D; Rose, K; Wilson, T; Krulevitch, P

    2002-03-08

    This paper focuses on the design consideration, fabrication processes and preliminary testing of the stretchable micro-electrode array. We are developing an implantable, stretchable micro-electrode array using polymer-based microfabrication techniques. The device will serve as the interface between an electronic imaging system and the human eye, directly stimulating retinal neurons via thin film conducting traces and electroplated electrodes. The metal features are embedded within a thin ({approx}50 micron) substrate fabricated using poly (dimethylsiloxane) (PDMS), a biocompatible elastomeric material that has very low water permeability. The conformable nature of PDMS is critical for ensuring uniform contact with the curved surface of the retina. To fabricate the device, we developed unique processes for metalizing PDMS to produce robust traces capable of maintaining conductivity when stretched (5%, SD 1.5), and for selectively passivating the conductive elements. An in situ measurement of residual strain in the PDMS during curing reveals a tensile strain of 10%, explaining the stretchable nature of the thin metalized devices.

  12. Peltier effects in electrode carbon

    Science.gov (United States)

    Hansen, Ellen Marie; Egner, Espen; Kjelstrup, Signe

    1998-02-01

    The thermoelectric power of a cell with platinum electrodes and a carbon conductor was determined. The electromotive force (emf) was measured as a function of the temperature difference between the electrodes at temperatures varying from 310 °C to 970 °C. From these measurements, the transported entropy of electric charge in carbon was found to vary from -1.7 to -1.9 J/(K mole) at temperatures around 300 °C, from -2.0 to -2.3 J/(K mole) at temperatures around 550 °C, and from -3.4 to -3.7 J/(K mole) at temperatures around 950 °C. This transported entropy had not before been determined for temperatures above 550 °C. Also, it is shown how the previously neglected surface properties can be taken into account to interpret the measurements. In the Hall-Héroult cell, the anode is made of a similar kind of carbon. Hence, the transported entropy found above can be used to describe the often neglected coupling between transport of heat and electric charge in this electrode. It is shown that the calculated electric potential profile through a coal sample will change significantly if the coupling is neglected, but the calculated temperature profile is independent of whether the coupling is neglected. New equations are also developed that can be used to evaluate the importance of the coupling in other systems.

  13. Redox electrode materials for supercapatteries

    Science.gov (United States)

    Yu, Linpo; Chen, George Z.

    2016-09-01

    Redox electrode materials, including transition metal oxides and electronically conducting polymers, are capable of faradaic charge transfer reactions, and play important roles in most electrochemical energy storage devices, such as supercapacitor, battery and supercapattery. Batteries are often based on redox materials with low power capability and safety concerns in some cases. Supercapacitors, particularly those based on redox inactive materials, e.g. activated carbon, can offer high power output, but have relatively low energy capacity. Combining the merits of supercapacitor and battery into a hybrid, the supercapattery can possess energy as much as the battery and output a power almost as high as the supercapacitor. Redox electrode materials are essential in the supercapattery design. However, it is hard to utilise these materials easily because of their intrinsic characteristics, such as the low conductivity of metal oxides and the poor mechanical strength of conducting polymers. This article offers a brief introduction of redox electrode materials, the basics of supercapattery and its relationship with pseudocapacitors, and reviews selectively some recent progresses in the relevant research and development.

  14. Applications of Ellipsometry in the Investigations of Electrode-Solution Interface%“电极/溶液”界面的椭圆偏振测量技术研究进展

    Institute of Scientific and Technical Information of China (English)

    雷惊雷; 吴良柳; 李凌杰; 巫生茂; 张胜涛

    2013-01-01

    Ellipsometry is an optical technique with high-sensitivity to quantitatively obtain surface/interface properties such as thickness and refractive index by analyzing the changes in polarized light reflected from the surface/interface. Its noncontacting and nondestructive nature makes it possible to acquire the in situ real-time information of the change at the surface/interface. Therefore, ellipsometry has been used widely in the electrochemical investigations. In this paper, based on the brief introduction of the measurement principle of ellipsometry, the current progress and the future trends of ellipsometry in electrochemistry are discussed. The applications of ellipsometry in the fields of conversion and storage of electrochemical energy, electrochemistry of materials science, electroanalysis and bioelectrochemistry are reviewed.%椭圆偏振测量技术是通过解析偏振光束在界面上或薄膜中反射或透射时偏振状态的变化,获取界面或薄膜的厚度、复折射率等性质的一种光学方法,是一种高灵敏度、非破坏性的原位实时表征技术,被广泛应用于“电极/溶液”界面的研究.本文简要介绍了椭圆偏振测量技术的基本原理及其最新发展,并着重评述了能源电化学、材料电化学、电分析与生物电化学等领域中,应用椭圆偏振测量技术研究“电极/溶液”界面的现状.

  15. Direct Electrochemistry of Horseradish Peroxidase on NiO Nanoflower Modified Electrode and Its Electrocatalytic Activity

    Directory of Open Access Journals (Sweden)

    Lijun Yan

    2016-09-01

    Full Text Available In this paper nickel oxide (NiO nanoflower was synthesized and used for the realization of direct electrochemistry of horseradish peroxidase (HRP. By using carbon ionic liquid electrode (CILE as the substrate electrode, NiO-HRP composite was casted on the surface of CILE with chitosan (CTS as the film forming material and the modified electrode was denoted as CTS/NiO-HRP/CILE. UV-Vis absorption and FT-IR spectra confirmed that HRP retained its native structure after mixed with NiO nanoflower. Direct electron transfer of HRP on the modified electrode was investigated by cyclic voltammetry with a pair of quasi-reversible redox waves appeared, indicating that the presence of NiO nanoflower on the electrode surface could accelerate the electron transfer rate between the electroactive center of HRP and the substrate electrode. Electrochemical behaviors of HRP on the modified electrode were carefully investigated. The HRP modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid with wider linear range and lower detection limit. Therefore the presence of NiO nanoflower could provide a friendly biocompatible interface for immobilizing biomolecules and keeping their native structure. The fabricated electrochemical biosensor displayed the advantages such as high sensitivity, good reproducibility and long-term stability. This work is licensed under a Creative Commons Attribution 4.0 International License.

  16. Application of Polyaniline Incorporated Carbon Particles Coated Platinum Electrode in Coulometric Titration to Determination of Polyisoprene Alcohol

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ge; LIU Meng; LIU Kuai-zhi; QU Jiang-ying; CHENG Gang; DU Zu-ling

    2003-01-01

    The feasibility of using electrodes modified with polyaniline incorporated carbon particles films for improving the precision of coulometric titration is demonstrated. The problem of large deviation produced during determining polyisoprene by coulometric titration with direct titration technique(double Pt electrodes indicating electrode) has been solved. In the titration process, polyisoprene alcohol, an electro-inactive species, is adsorbed on the surface of the bare Pt electrode, which inhibits the electrode reaction of Br- and Br2. Therefore, when the titration reaches the end-point, the detected current will slowly change with time, which can make the repeatability of end-point poor. The atomic force microscopic images show the morphology of the electrode surface of adsorbing polyisoprene alcohol. The application of the chemically modified electrode instead of the bare Pt electrode to indicating the end-point has been investigated. The results show that the Pt electrode coated with polyaniline incorporated carbon particles films is an excellent indicator electrode. This electrode has advantages that the indicating signals are sharp and repeatable at end-point. The precision and the accuracy of the determination of polyisoprene alcohol are satisfactory.

  17. Activation and discharge kinetics of metal hydride electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Johnsen, Stein Egil

    2003-07-01

    Potential step chronoamperometry and Electrochemical Impedance Spectroscopy (eis) measurements were performed on single metal hydride particles. For the {alpha}-phase, the bulk diffusion coefficient and the absorption/adsorption rate parameters were determined. Materials produced by atomisation, melt spinning and conventional casting were investigated. The melt spun and conventional cast materials were identical and the atomised material similar in composition. The particles from the cast and the melt spun material were shaped like parallelepipeds. A corresponding equation, for this geometry, for diffusion coupled to an absorption/adsorption reaction was developed. It was found that materials produced by melt spinning exhibited lower bulk diffusion (1.7E-14 m2/s) and absorption/adsorption reaction rate (1.0E-8 m/s), compared to materials produced by conventionally casting (1.1E-13 m2/s and 5.5E-8 m/s respectively). In addition, the influence of particle active surface and relative diffusion length were discussed. It was concluded that there are uncertainties connected to these properties, which may explain the large distribution in the kinetic parameters measured on metal hydride particles. Activation of metal hydride forming materials has been studied and an activation procedure, for porous electrodes, was investigated. Cathodic polarisation of the electrode during a hot alkaline surface treatment gave the maximum discharge capacity on the first discharge of the electrode. The studied materials were produced by gas atomisation and the spherical shape was retained during the activation. Both an AB{sub 5} and an AB{sub 2} alloy was successfully activated and discharge rate properties determined. The AB{sub 2} material showed a higher maximum discharge capacity, but poor rate properties, compared to the AB{sub 5} material. Reduction of surface oxides, and at the same time protection against corrosion of active metallic nickel, can explain the satisfying results of

  18. IDENTIFICATION OF CHLOROMETHANE FORMATION PATHS DURING ELECTROCHEMICAL DECHLORINATION OF TCE USING GRAPHITE ELECTRODES

    Science.gov (United States)

    The purpose of this research is to investigate the formation of chloromethane during TCE dechlorination in a mixed electrochemical reactor using graphite electrodes. Chloromethane was the major chlorinated organic compound detected in previous dechlorination experiments. In order...

  19. ZnO nanorods for simultaneous light trapping and transparent electrode application in solar cells

    KAUST Repository

    Khan, Yasser

    2011-10-01

    Efficacy of using vertically grown ZnO nanorod array in enhancing electromagnetic field intensity and serving as the top contact layer (transparent electrodes) for solar cells was investigated. © 2011 IEEE.

  20. DETERMINATION OF HETEROGENEOUS ELECTRON TRANSFER RATE CONSTANTS AT MICROFABRICATED IRIDIUM ELECTRODES. (R825511C022)

    Science.gov (United States)

    There has been an increasing use of both solid metal and microfabricated iridium electrodes as substrates for various types of electroanalysis. However, investigations to determine heterogeneous electron transfer rate constants on iridium, especially at an electron beam evapor...

  1. Performance characteristics of lead oxides in pasted lead/acid battery electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Afifi, S.E. (Electrometallurgy Lab., Central Metallurgical Research and Development Inst., Cairo (Egypt)); Saba, A.E. (Electrometallurgy Lab., Central Metallurgical Research and Development Inst., Cairo (Egypt)); Shenouda, A.Y. (Electrometallurgy Lab., Central Metallurgical Research and Development Inst., Cairo (Egypt))

    1993-10-15

    The performance characteristics of lead oxides used for the pasted type of lead/acid battery plate have been investigated. The [alpha]- and [beta]-PbO polymorphs have been prepared carefully and used for pasting model electrodes. The factors that may affect the electrical capacity of such electrodes have been studied. These are: the type of oxide; percentage of free lead; additives such as carboxymethyl cellulose, zeolite and graphite. Lead hydroxide has also been studied with special attention. Photomicrographs have been taken to examine the crystal forms that develop on the electrode surface. Finally, some industrial samples have been investigated. (orig.)

  2. First principles study of the electron density distribution in a pair of bare metallic electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Chun-Lan [Suzhou University of Science and Technology, School of Mathematics and Physics, Suzhou (China); Chen, Yu-Chang; Nghiem, Diu; Tseng, Allen; Huang, Pao-Chieh [National Chiao Tung University, Department of Electrophysics, Hsinchu (China)

    2011-07-15

    Self-consistent calculations of electron density distribution from first principles for a series of semi-infinite metals show that the electron density almost drops to zero at 8.5 a.u. away from a metal surface. The electron densities in a series of bimetallic-electrode systems with a distance between the two electrodes of 21.7 a.u. are further investigated. Spin-polarized calculations of electron density for nonmagnetic and magnetic bimetallic-electrode systems are compared. Our work is helpful for first principles investigation of spin-dependent metal-molecule-metal tunneling junctions. (orig.)

  3. Performance of the DTL electrode compared to the jet contact lens electrode in clinical testing.

    Science.gov (United States)

    Yin, Hang; Pardue, Machelle T

    2004-01-01

    To compare the recording characteristics of the DTL fiber and Jet contact lens electrodes, ERG responses were recorded from 20 normal subjects using the ISCEV standard clinical protocol. In each subject, the DTL electrode was placed in the right eye and the Jet contact lens in the left eye after 30 min of dark-adaptation. After presenting standard dark- and light-adapted stimuli, each response was analyzed for a- and b-wave amplitude and implicit time. Each subject was then asked to rate the comfort of each electrode. Responses recorded with the DTL are larger and faster for the dark-adapted dim white and red flashes. In contrast, the Jet electrode records larger responses for the dark-adapted standard flash and light-adapted flashes. Of these differences, only the standard flash is statistically significant. However, overall the DTL electrode has greater variability than the Jet electrode across all recordings. The DTL and Jet electrodes cannot be used interchangeably as demonstrated by a Bland and Altman analysis of agreement. Thus, separate normative values need to be collected for each type of electrode to accurately assess retinal function. Based on the comfort assessment of the two electrodes, the subjects preferred the DTL electrode over the Jet electrode. Due to the superior comfort level of the DTL and its similarities to the Jet contact lens electrode in ERG recordings, the DTL electrode appears to be a good alternative to the Jet electrode in routine clinical testing when used with the appropriate normative values.

  4. Electrochemical storage of hydrogen on carbon electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Jurewicz, K.; Frackowiak, E. [ICTE, Poznan University of Technology (Poland); Gautier, S.; Beguin, F. [CRMD, CNRS Universite, 45 - Orleans (France)

    2000-07-01

    Amount of hydrogen reversibly stored on an activated carbon electrode using electro-decomposition of 6 mol.l{sup -1} KOH aqueous solution has been investigated and compared data obtained under a high pressure of dihydrogen (70 bars) at 273 K. In the electrochemical method, 1.5 wt% of hydrogen was released from carbon during the oxidation process, with a well-defined plateau at ca. - 0.5 V vs Hg/HgO. Relatively smaller values were obtained for the sorption ability under a high pressure of gas. This means that the formation of nascent hydrogen during water reduction favours its easy penetration in the carbon nano-structure, even at ambient pressure and temperature. Our results show that not only carbon nano-tubes should be considered for hydrogen reservoir and that low cost materials such as activated carbons could be convenient in appropriate conditions.

  5. Plastic Membrane Electrodes of Coated Wire Type for Micro Determination of Quininium Cation in Pharmaceutical Tablets

    OpenAIRE

    2011-01-01

    Problem statement: Silver and copper all-solid state wire sensor electrodes of quininium cation with different ion exchangers have been prepared and used in pharmaceutical analysis. A comparative study with a reference method is applied in order to investigate the validity of the proposed method for potentiometric analysis of pharmaceutical compounds containing quinine. Approach: A Nernstian equation was proved for all electrodes of quinine in this research. Potentiometric investigations were...

  6. Effect of Different Electrode Materials on the Electropolymerization Process of Aniline in Nitric Acid Media

    Science.gov (United States)

    Li, Yaozong; Yi, Yun; Yang, Weifang; Liu, Xiaoqing; Li, Yuanyuan; Wang, Wei

    2017-02-01

    The electropolymerization process of aniline on different electrode surfaces such as Pt, Au, RuTi and polyaniline film in nitric acid solution containing 1 M aniline was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Proposed electrical equivalent circuits were used to give a further analysis. Results show that the electrode materials accelerate the aniline electropolymerization remarkably as a catalyst, especially the electrochemical oxidation process of monomer aniline to its cation radical, which is the key step to incur the electropolymerization reaction of aniline on the electrode surface. The polymerization of aniline on RuTi electrode has the lowest reaction resistance for its adsorption sites, and the catalytic effects of these different electrodes decrease in the order: RuTi > polyaniline film > Pt > Au. The results also show that several states of polyaniline films are formed during the potential linear scan process in nitric acid solution and the corresponding oxidation and reduction reaction are reversible.

  7. Role of SAM Chain Length in Enhancing the Sensitivity of Nanopillar Modified Electrodes for Glucose Detection

    Directory of Open Access Journals (Sweden)

    2009-02-01

    Full Text Available In this report, alkanethiol self assembled monolayers (SAM with two different chain lengths were used to immobilize the functionalizing enzyme (glucose oxidase onto gold nanopillar modified electrodes and the electrochemical processes of these functionalized electrodes in glucose detection were investigated. First, the formation of these SAMs on the nanopillar modified electrodes was characterized by the cyclic voltammetry and electrochemical impedance spectroscopy techniques, and then the detection sensitivity of these functionalized electrodes to glucose was evaluated by the amperometry technique. Results showed that the SAM of alkanethiols with a longer chain length resulted in a higher degree of surface coverage with less defect and a higher electron transfer resistance, whereas the SAM of alkanethiols with a shorter chain length gave rise to a higher detection sensitivity to glucose. This study sheds some new insight into how to enhance the sensing performance of nanopillar modified electrodes.

  8. STUDY OF THE ELECTRICAL CONDUCTIVITY OF GRAPHITE FELT EMPLOYED AS A POROUS ELECTRODE

    Directory of Open Access Journals (Sweden)

    E.O. Vilar

    1998-09-01

    Full Text Available The objective of the present work is to study the variation of the electrode distribution potential under electrical conductivity variation of graphite felt RVG 4000 ( Le Carbone Lorraine when submitted to a mechanical compression. Experimental and theoretical studies show that this electrical conductivity variation can changes the electrode potential distribution E(x working under limiting current conditions. This may occur when graphite felt is confined in an electrochemical reactor compartment or simply when it is submitted to a force performed by an electrolyte percolation in a turbulent flow. This investigation can contribute to the improvement of electrochemical cells that may use this material as an electrode. Finally, one modification is suggested in the equation that gives the electrode potential distribution E(x - E(0. In this case the parameter L (thickness in metal porous electrodes is substituted for Lf = Li (1-j, where j corresponds to the reduction factor of the initial thickness Li.

  9. Effects of the surface-adsorption of boron-doped diamond electrode on its electrochemical behavior

    Institute of Scientific and Technical Information of China (English)

    LIU Fengbin; LI Xuemin; WANG Jiadao; LIU Bing; CHEN Darong

    2006-01-01

    To elucidate the effects of the hydro- genation and oxygenation of the boron-doped diamond (BDD) electrode on its electrochemical behaviors, the surface morphologies and phases of the two surface-adsorption BDD films have been investigated and the cyclic voltammograms and AC impedance spectra have been measured at these two BDD electrodes. The results indicate that compared with the hydrogen-adsorption BDD film, oxygen-adsor- ption BDD film is less conductive, and has a larger surface roughness and a lower sp3/sp2 ratio. The oxygenated BDD film electrode possesses a wider electrochemical window, larger diamond film resistance and capacitance and a larger polarization resistance than hydrogenated BDD electrode. In addition, the effect mechanism of the surface-adsorption of BDD electrode on its electrochemical behaviors has been discussed.

  10. Advanced boundary electrode modeling for tES and parallel tES/EEG

    CERN Document Server

    Agsten, Britte; Pursiainen, Sampsa; Wolters, Carsten H

    2016-01-01

    This paper explores advanced electrode modeling in the context of separate and parallel transcranial electrical stimulation (tES) and electroencephalography (EEG) measurements. We focus on boundary condition based approaches that do not necessitate adding auxiliary elements, e.g. sponges, to the computational domain. In particular, we investigate the complete electrode model (CEM) which incorporates a detailed description of the skin-electrode interface including its contact surface, impedance and normal current distribution. The CEM can be applied for both tES and EEG electrodes which is advantageous when a parallel system is used. In comparison to the CEM, we test two important reduced approaches: the gap model (GAP) and the point electrode model (PEM). We aim to find out the differences of these approaches for a realistic numerical setting based on the stimulation of the auditory cortex. The results obtained suggest, among other things, that GAP and GAP/PEM are sufficiently accurate for the practical appli...

  11. The role of front and back electrodes in parasitic absorption in thin-film solar cells

    Directory of Open Access Journals (Sweden)

    Boccard Mathieu

    2014-07-01

    Full Text Available When it comes to parasitic absorption in thin-film silicon solar cells, most studies focus on one electrode only, most of the time the substrate (in n-i-p configuration or superstrate (in p-i-n configuration. We investigate here simultaneously the influence of the absorption in both front and back electrodes on the current density of tandem micromorph solar cells in p-i-n configuration. We compare four possible combinations of front and back electrodes with two different doping levels, but identical sheet resistance and identical light-scattering properties. In the infrared part of the spectrum, parasitic absorption in the front or back electrode is shown to have a similar effect on the current generation in the cell, which is confirmed by modeling. By combining highly transparent front and back ZnO electrodes and high-quality silicon layers, a micromorph device with a stabilized efficiency of 11.75% is obtained.

  12. Studying the Performance of Conductive Polymer Films as Textile Electrodes for Electrical Bioimpedance Measurements

    Science.gov (United States)

    Cunico, F. J.; Marquez, J. C.; Hilke, H.; Skrifvars, M.; Seoane, F.

    2013-04-01

    With the goal of finding novel biocompatible materials suitable to replace silver in the manufacturing of textile electrodes for medical applications of electrical bioimpedance spectroscopy, three different polymeric materials have been investigated. Films have been prepared from different polymeric materials and custom bracelets have been confectioned with them. Tetrapolar total right side electrical bioimpedance spectroscopy (EBIS) measurements have been performed with polymer and with standard gel electrodes. The performance of the polymer films was compared against the performance of the gel electrodes. The results indicated that only the polypropylene 1380 could produce EBIS measurements but remarkably tainted with high frequency artefacts. The influence of the electrode mismatch, stray capacitances and large electrode polarization impedance are unclear and they need to be clarified with further studies. If sensorized garments could be made with such biocompatible polymeric materials the burden of considering textrodes class III devices could be avoided.

  13. Effect of Different Electrode Materials on the Electropolymerization Process of Aniline in Nitric Acid Media

    Science.gov (United States)

    Li, Yaozong; Yi, Yun; Yang, Weifang; Liu, Xiaoqing; Li, Yuanyuan; Wang, Wei

    2016-11-01

    The electropolymerization process of aniline on different electrode surfaces such as Pt, Au, RuTi and polyaniline film in nitric acid solution containing 1 M aniline was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Proposed electrical equivalent circuits were used to give a further analysis. Results show that the electrode materials accelerate the aniline electropolymerization remarkably as a catalyst, especially the electrochemical oxidation process of monomer aniline to its cation radical, which is the key step to incur the electropolymerization reaction of aniline on the electrode surface. The polymerization of aniline on RuTi electrode has the lowest reaction resistance for its adsorption sites, and the catalytic effects of these different electrodes decrease in the order: RuTi > polyaniline film > Pt > Au. The results also show that several states of polyaniline films are formed during the potential linear scan process in nitric acid solution and the corresponding oxidation and reduction reaction are reversible.

  14. Surface effects of electrode-dependent switching behavior of resistive random-access memory

    KAUST Repository

    Ke, Jr Jian

    2016-09-26

    The surface effects of ZnO-based resistive random-access memory (ReRAM) were investigated using various electrodes. Pt electrodes were found to have better performance in terms of the device\\'s switching functionality. A thermodynamic model of the oxygen chemisorption process was proposed to explain this electrode-dependent switching behavior. The temperature-dependent switching voltage demonstrates that the ReRAM devices fabricated with Pt electrodes have a lower activation energy for the chemisorption process, resulting in a better resistive switching performance. These findings provide an in-depth understanding of electrode-dependent switching behaviors and can serve as design guidelines for future ReRAM devices.

  15. Interaction of red blood cells with a polarized electrode: evidence of long-range intermolecular forces.

    Science.gov (United States)

    Gingell, D; Fornes, J A

    1976-10-01

    We have investigated the electrostatic interaction of glutaraldehyde-fixed human red cells with a polarizable electrode carrying a defined surface charge density which can be varied continuously through a wide range. Cells in a dilute salt solution are unable to adhere to the electrode at high negative charge, but at lower negative charge densities they are reversibly adherent and can be forced off by increasing the negative polarization. Near zero electrode charge they become irreversibly stuck to the electrode and cannot be evicted even at maximum electrode polarization. Calculation of the electrostatic repulsive force using measured charge densities indicates the existence of an attractive force which may be acting over several hundred angstroms.

  16. Differential pulse voltammetric determination of metformin using copper-loaded activated charcoal modified electrode.

    Science.gov (United States)

    Gholivand, Mohammad Bagher; Mohammadi-Behzad, Leila

    2013-07-01

    A simple and sensitive carbon paste electrode has been developed for the electrochemical trace determination of metformin (MET). This sensor was designed by Copper(II)-loaded activated charcoal (Cu-AC) in the carbon paste electrode (CPE), which provides remarkably improved sensitivity and selectivity for the electrochemical stripping assay of MET. The drug was accumulated on the surface of the electrode through formation of a coordination complex with copper ions, which enhanced the sensitivity of the method. The effects of various copper(II) salts and oxidation states of copper (within the carbon paste electrode) on MET oxidation behavior were also investigated. The calibration graph was linear over the concentration range of 50 nM to 60 μM MET, and the detection limit was calculated as 9 nM. The proposed electrode was used successfully for MET determination in real matrices.

  17. Influence of carbonisation on selected engineering properties of carbon resin electrodes for electrochemical treatment of wastewater

    Energy Technology Data Exchange (ETDEWEB)

    Oke, I.A. [Obafemi Awolowo Univ., Ile-Ife (Nigeria). Dept. of Civil Engineering

    2009-10-15

    Carbon resin electrodes (CRE) developed using a non-heat treatment process were investigated in an effort to determine the influence of several properties on electrode performance. These included density; electrical resistance; microstructure; hydroscopy; stability moisture content; and compressive and flexural strength. The influences of carbonization temperature, carbon particle size, and compaction pressure were also analyzed. Results of the study showed that the electrical resistance and density of the CRE decreased with increases in carbonization temperatures. Particle size, compacting pressure, and the percentage of resin used in the electrodes also influenced electrical resistance. The carbonization of the CREs from 30 to 220 degrees C reduced specific electrical resistance and density. The carbonization temperature did not have a significant effect on wetness, compressive and flexural strength, or on the stability and moisture content of the electrodes. It was concluded that the cost of producing the CREs is significantly cheaper than the cost of heat-treated electrodes. 78 refs., 9 tabs., 8 figs.

  18. Electrochemical oxidation of methanol on Pt nanoparticles composited MnO 2 nanowire arrayed electrode

    Science.gov (United States)

    Zhao, Guang-Yu; Li, Hu-Lin

    2008-03-01

    By use of the membrane-template synthesis route, MnO 2 nanowire arrayed electrodes are successfully synthesized by means of the anodic deposition technique. The Pt nanoparticles composited MnO 2 nanowire arrayed electrodes (PME) are obtained through depositing Pt on MnO 2 nanowire arrayed electrode by cathode deposition technique. For comparison of electrochemical performance, Pt nanowire arrayed electrodes which have the same amount of Pt with PME are also prepared. The electro-oxidation of methanol on PME and Pt nanowire arrayed electrodes is investigated at room temperature by cyclic voltammetry, which show that about 110 mV decreased overpotential and 2.1-fold enhanced votammetric current are achieved on PME. The chronoamperometry result demonstrates that the resistance to carbon monoxide for PME is improved.

  19. Investigation on the structure, thermodynamic and electrochemical properties of the MmNi{sub 3.55}Mn{sub 0.4}Al{sub 0.3}Fe{sub 0.75} compound used as negative electrode in Ni–MH batteries

    Energy Technology Data Exchange (ETDEWEB)

    Ben Moussa, M., E-mail: phmoussa@yahoo.fr [Institut National de Recherche et d’Analyse Physico-chimique, Pôle Technologique de Sidi Thabet, 2020 Sidi Thabet (Tunisia); Laboratoire des Matériaux et Procédés, ESSTT, 5 Avenu Taha Hussein 1008 (Tunisia); College of Applied Sciences, Department of Physics, Umm Al Qura University, Makkah (Saudi Arabia); Abdellaoui, M. [Institut National de Recherche et d’Analyse Physico-chimique, Pôle Technologique de Sidi Thabet, 2020 Sidi Thabet (Tunisia); Lamloumi, J. [Laboratoire des Matériaux et Procédés, ESSTT, 5 Avenu Taha Hussein 1008 (Tunisia); Percheron Guégan, A. [Laboratoire de Chimie Métallurgique des Terres Rares, GLVT, 2-8 Rue Henri Dunant, F 94320, Thiais-Cedex (France)

    2013-10-25

    Highlights: •The solid–gas capacity at room temperature is equal to 3.93 H/mol. •The value pressure equilibrium is 0.024 bar. •The average radius particles decrease with number of cycles. •The hydrogen diffusion coefficient D{sub H}, increase with number of cycles. -- Abstract: The structure, thermodynamic and electrochemical properties of the hydride poly-substituted MmNi{sub 3.55}Mn{sub 0.4}Al{sub 0.3}Fe{sub 0.75} alloy used as material for negative electrode in Ni–MH batteries investigated. The solid–gas capacity and pressure equilibrium measurement at room temperature are respectively 3.93 H/mol and 0.024 bars. The chronoamperometry method shows the size of the particles (a) participating in the electrochemical reaction decrease of cycle number. The hydrogen diffusion coefficient determined by electrochemical impedance spectroscopy (EIS) increase of the number of cycles from 3.5 × 10{sup −12} cm{sup 2} s{sup −1} before cycling to 7.29 × 10{sup −10} cm{sup 2} s{sup −1} after 13 cycles charge–decharge.

  20. Cobalt Phthalocyanine Modified Electrodes Utilised in Electroanalysis: Nano-Structured Modified Electrodes vs. Bulk Modified Screen-Printed Electrodes

    Directory of Open Access Journals (Sweden)

    Christopher W. Foster

    2014-11-01

    Full Text Available Cobalt phthalocyanine (CoPC compounds have been reported to provide electrocatalytic performances towards a substantial number of analytes. In these configurations, electrodes are typically constructed via drop casting the CoPC onto a supporting electrode substrate, while in other cases the CoPC complex is incorporated within the ink of a screen-printed sensor, providing a one-shot economical and disposable electrode configuration. In this paper we critically compare CoPC modified electrodes prepared by drop casting CoPC nanoparticles (nano-CoPC onto a range of carbon based electrode substrates with that of CoPC bulk modified screen-printed electrodes in the sensing of the model analytes L-ascorbic acid, oxygen and hydrazine. It is found that no “electrocatalysis” is observed towards L-ascorbic acid using either of these CoPC modified electrode configurations and that the bare underlying carbon electrode is the origin of the obtained voltammetric signal, which gives rise to useful electroanalytical signatures, providing new insights into literature reports where “electrocatalysis” has been reported with no clear control experiments undertaken. On the other hand true electrocatalysis is observed towards hydrazine, where no such voltammetric features are witnessed on the bare underlying electrode substrate.

  1. Cobalt phthalocyanine modified electrodes utilised in electroanalysis: nano-structured modified electrodes vs. bulk modified screen-printed electrodes.

    Science.gov (United States)

    Foster, Christopher W; Pillay, Jeseelan; Metters, Jonathan P; Banks, Craig E

    2014-11-19

    Cobalt phthalocyanine (CoPC) compounds have been reported to provide electrocatalytic performances towards a substantial number of analytes. In these configurations, electrodes are typically constructed via drop casting the CoPC onto a supporting electrode substrate, while in other cases the CoPC complex is incorporated within the ink of a screen-printed sensor, providing a one-shot economical and disposable electrode configuration. In this paper we critically compare CoPC modified electrodes prepared by drop casting CoPC nanoparticles (nano-CoPC) onto a range of carbon based electrode substrates with that of CoPC bulk modified screen-printed electrodes in the sensing of the model analytes L-ascorbic acid, oxygen and hydrazine. It is found that no "electrocatalysis" is observed towards L-ascorbic acid using either of these CoPC modified electrode configurations and that the bare underlying carbon electrode is the origin of the obtained voltammetric signal, which gives rise to useful electroanalytical signatures, providing new insights into literature reports where "electrocatalysis" has been reported with no clear control experiments undertaken. On the other hand true electrocatalysis is observed towards hydrazine, where no such voltammetric features are witnessed on the bare underlying electrode substrate.

  2. Application of N-doped graphene modified carbon ionic liquid electrode for direct electrochemistry of hemoglobin

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Wei, E-mail: swyy26@hotmail.com [College of Chemistry and Chemical Engineering, Hainan Normal University, Haikou 571158 (China); Dong, Lifeng, E-mail: donglifeng@qust.edu.cn [College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China); Department of Physics, Astronomy, and Materials Science, Missouri State University, Springfield, MO 65897 (United States); Deng, Ying; Yu, Jianhua [College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China); Wang, Wencheng [College of Chemistry and Chemical Engineering, Hainan Normal University, Haikou 571158 (China); Zhu, Qianqian [College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China)

    2014-06-01

    Nitrogen-doped graphene (NG) was synthesized and used for the investigation on direct electrochemistry of hemoglobin (Hb) with a carbon ionic liquid electrode as the substrate electrode. Due to specific characteristics of NG such as excellent electrocatalytic property and large surface area, direct electron transfer of Hb was realized with enhanced electrochemical responses appearing. Electrochemical behaviors of Hb on the NG modified electrode were carefully investigated with the electrochemical parameters calculated. The Hb modified electrode exhibited excellent electrocatalytic reduction activity toward different substrates, such as trichloroacetic acid and H{sub 2}O{sub 2}, with wider dynamic range and lower detection limit. These findings show that NG can be used for the preparation of chemically modified electrodes with improved performance and has potential applications in electrochemical sensing. - Graphical abstract: The utilization of N-doped graphene enables direct electrochemistry of hemoglobin with a pair of well-defined redox peaks appearing. - Highlights: • Nitrogen-doped graphene (NG) was synthesized by a solvothermal method. • NG was used for the investigation on direct electrochemistry of hemoglobin with carbon ionic liquid electrode. • The Hb modified electrode exhibited excellent electrocatalytic activity toward different substrates.

  3. Electrocatalytic oxidation of methanol at platinum electrode modified with Eu-Fe cyanide-bridged binuclear complexes

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The electrocatalytic oxidation of methanol at the platinum electrode modified with Eu-Fe cyanide-bridged binuclear complexes (Eu-Fe film) was investigated for the first time by cyclic voltammetry.Compared with the bare platinum electrode,the results showed that the modified electrode had excellent electrocatalytic activity for the oxidation of methanol;the oxidation peak potential shifted more negatively and the peak current increased about twenty times.The electrooxidation of methanol at the modified el...

  4. Conical surface structures on model thin-film electrodes and tape-cast electrode materials for lithium-ion batteries

    Science.gov (United States)

    Kohler, R.; Proell, J.; Bruns, M.; Ulrich, S.; Seifert, H. J.; Pfleging, W.

    2013-07-01

    Three-dimensional structures in cathode materials for lithium-ion batteries were investigated in this study. For this purpose, laser structuring of lithium cobalt oxide was investigated at first for a thin-film model system and in a second step for conventional tape-cast electrode materials. The model thin-film cathodes with a thickness of 3 μm were deposited using RF magnetron sputtering on stainless steel substrates. The films were structured via excimer laser radiation with a wavelength of 248 nm. By adjusting the laser fluence, self-organized conical microstructures were formed. Using conventional electrodes, tape-cast cathodes made of LiCoO2 with a film thickness of about 80 μm on aluminum substrates were studied. It was shown that self-organizing surface structures could be formed by adjustment of the laser parameters. To investigate the formation mechanisms of the conical topography, the element composition was studied by time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy. Electrochemical cycling using a lithium anode and conventional electrolyte was applied to study the influence of the laser processing procedures on cell performance. For the model electrode system, a significantly higher discharge capacity of 80 mAh/g could be obtained after 110 cycles by laser structuring compared to 8 mAh/g of the unstructured thin film. On conventional tape-cast electrodes self-organized surface structures could also increase the cycling stability resulting in an 80 % increase in capacity after 110 cycles in comparison to the unstructured electrode.

  5. iElectrodes: A Comprehensive Open-Source Toolbox for Depth and Subdural Grid Electrode Localization

    Science.gov (United States)

    Blenkmann, Alejandro O.; Phillips, Holly N.; Princich, Juan P.; Rowe, James B.; Bekinschtein, Tristan A.; Muravchik, Carlos H.; Kochen, Silvia

    2017-01-01

    The localization of intracranial electrodes is a fundamental step in the analysis of invasive electroencephalography (EEG) recordings in research and clinical practice. The conclusions reached from the analysis of these recordings rely on the accuracy of electrode localization in relationship to brain anatomy. However, currently available techniques for localizing electrodes from magnetic resonance (MR) and/or computerized tomography (CT) images are time consuming and/or limited to particular electrode types or shapes. Here we present iElectrodes, an open-source toolbox that provides robust and accurate semi-automatic localization of both subdural grids and depth electrodes. Using pre- and post-implantation images, the method takes 2–3 min to localize the coordinates in each electrode array and automatically number the electrodes. The proposed pre-processing pipeline allows one to work in a normalized space and to automatically obtain anatomical labels of the localized electrodes without neuroimaging experts. We validated the method with data from 22 patients implanted with a total of 1,242 electrodes. We show that localization distances were within 0.56 mm of those achieved by experienced manual evaluators. iElectrodes provided additional advantages in terms of robustness (even with severe perioperative cerebral distortions), speed (less than half the operator time compared to expert manual localization), simplicity, utility across multiple electrode types (surface and depth electrodes) and all brain regions. PMID:28303098

  6. Nickel electrode for alkaline batteries

    Energy Technology Data Exchange (ETDEWEB)

    Charkey, A.; Januszkiewicz, S.

    1985-10-08

    A nickel electrode including a conductive support and a layer on the support including a mixture of a nickel active material and a graphite diluent containing a spinel type oxide, the spinel type oxide having the formula M/sub 2/Co/sub 2/O/sub 4/, where M/sub 2/ is Co, Ni, Mn, Fe, Cu, Zn or Cd, or combinations thereof, and having a weight which is in the range of 1-30 percent of the weight of the diluent.

  7. Progress in understanding SOFC electrodes

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Hansen, Karin Vels; Jørgensen, M.J.;

    2002-01-01

    The literature of SOFC electrode kinetics and mechanisms is full of contradicting details in case of both the SOFC anode and cathode processes. Only weak patterns may be identified. One interpretation is that each of the reported data sets reflects a laboratory specific nature of each...... and synthesis procedures. The paper deals with the available evidence and gives some possible explanations of observed phenomena, e.g. of the various reported effects of water and of the temperature dependence of H/D isotope effect on the SOFC anode. (C) 2002 Elsevier Science B.V. All rights reserved....

  8. A method to locate electrode placement.

    Science.gov (United States)

    Brodnick, D

    2000-01-01

    A new method uses redundancy in the 12-lead electrocardiogram (ECG) to determine the angles to all of the electrodes used to record the ECG. No other transducers or signals are needed. The method, a matrix manipulation of the standard 12-lead, would be applicable to all existing ECGs already stored on hospital systems. The invention of this method was originally motivated by the slight differences seen between ECGs acquired by the standard resting electrode placement versus those acquired in a monitoring or exercise placement. An ECG signal is acquired in multiple channels. A covariance matrix is formed. From the eigenvector solution of the matrix, the angles between the eigenvectors and the original signal vectors are determined. The angles calculated for any ECG test are compared to reference angles to determine whether the electrodes are placed in the standard ECG electrode placement, an alternative electrode placement, or an incorrect electrode placement.

  9. Stabilization of insertion electrodes for lithium batteries.

    Energy Technology Data Exchange (ETDEWEB)

    Thackeray, M. M.

    1998-09-03

    This paper discusses the techniques that are being employed to stabilize LiMn{sub 2}O{sub 4} spinel and composite Li{sub x}MnO{sub 2} positive electrodes. The critical role that spinel domains play in stabilizing these electrodes for operation at both 4 V and 3 V is highlighted. The concept of using an intermetallic electrode MM{prime} where M is an active alloying element and M{prime} is an inactive element (or elements) is proposed as an alternative negative electrode (to carbon) for lithium-ion cells. An analogy to metal oxide insertion electrodes, such as MnO{sub 2}, in which Mn is the electrochemically active ion and O is the inactive ion, is made. Performance data are given for the copper-tin electrode system, which includes the intermetallic phases eta-Cu{sub 6}Sn{sub 5} and Li{sub 2}CuSn.

  10. Secondary Ionization Coefficient of Dielectric Electrode

    Science.gov (United States)

    Kashiwagi, Yasuhide; Suzuki, Susumu; Itoh, Haruo

    Experiments for observations and stabilization of discharge paths in several electrode systems are carried out aiming at precise measurement of the secondary ionization coefficient γ of MgO film electrode. The discharge chamber is filled with Ar gas. The waveforms of the applied voltage between the electrodes and the discharge current are measured with visual observation of the discharge light. Two MgO coated electrodes are placed so that they are facing each other. For these MgO electrodes, the discharge paths take a detour, not the shortest distance. Smaller prebreakdown current pulses are observed before the breakdown. After breakdown, discontinuous discharge current is observed. Therefore, it is prepared a glass tube surrounding the discharge area. As the result, the discharge paths take a straight perpendicular for the electrode surface, and the discharge is stabilized.

  11. Lithium-aluminum-magnesium electrode composition

    Science.gov (United States)

    Melendres, Carlos A.; Siegel, Stanley

    1978-01-01

    A negative electrode composition is presented for use in a secondary, high-temperature electrochemical cell. The cell also includes a molten salt electrolyte of alkali metal halides or alkaline earth metal halides and a positive electrode including a chalcogen or a metal chalcogenide as the active electrode material. The negative electrode composition includes up to 50 atom percent lithium as the active electrode constituent and a magnesium-aluminum alloy as a structural matrix. Various binary and ternary intermetallic phases of lithium, magnesium, and aluminum are formed but the electrode composition in both its charged and discharged state remains substantially free of the alpha lithium-aluminum phase and exhibits good structural integrity.

  12. Improved electrodes and gas impurity investigations on alkaline electrolysers

    DEFF Research Database (Denmark)

    Reissner, R.; Schiller, G.; Knoeri, T.;

    Alkaline water electrolysis for hydrogenproduction is a well-established techniquebut some technological issues regarding thecoupling of alkaline water electrolysis andRenewable Energy Sources (RES) remain tobe improved....

  13. A serial dual-electrode detector based on electrogenerated bromine for capillary electrophoresis.

    Science.gov (United States)

    Du, Fuying; Cao, Shunan; Fung, Ying-Sing

    2014-12-01

    A new serial dual-electrode detector for CE has been designed and fabricated for postcolumn reaction detection based on electrogenerated bromine. A coaxial postcolumn reactor was employed to introduce bromide reagent and facilitate the fabrication of upstream generation electrode by simply sputtering Pt film onto the outer surface of the separation capillary. Bromide introduced could be efficiently converted to bromine at this Pt film electrode and subsequently detected by the downstream Pt microdisk detection electrode. Analytes that react with bromine could be determined by the decrease of bromine reduction current at the downstream electrode resulting from the reaction between analytes and bromine. The effects of serial dual-electrode detector working conditions including electrode potentials, bromide flow rate, and bromide concentration on analytical performance were investigated using glutathione (GSH) and glutathione disulfide (GSSG) as test analytes. Under the optimal conditions, detection limits down to 0.16 μM for GSH and 0.14 μM for GSSG (S/N = 3) as well as linear working ranges of two orders of magnitude for GSH and GSSG were achieved. Furthermore, the separation efficiency obtained by our dual-electrode detector design was greatly improved compared with previous reported design. The developed method has been successfully applied to determine the GSH and GSSG impurity in commercial GSH supplement.

  14. An analysis of EMG electrode configuration for targeted muscle reinnervation based neural machine interface.

    Science.gov (United States)

    Huang, He; Zhou, Ping; Li, Guanglin; Kuiken, Todd A

    2008-02-01

    Targeted muscle reinnervation (TMR) is a novel neural machine interface for improved myoelectric prosthesis control. Previous high-density (HD) surface electromyography (EMG) studies have indicated that tremendous neural control information can be extracted from the reinnervated muscles by EMG pattern recognition (PR). However, using a large number of EMG electrodes hinders clinical application of the TMR technique. This study investigated a reduced number of electrodes and the placement required to extract sufficient neural control information for accurate identification of user movement intents. An electrode selection algorithm was applied to the HD EMG recordings from each of four TMR amputee subjects. The results show that when using only 12 selected bipolar electrodes the average accuracy over subjects for classifying 16 movement intents was 93.0 (+/-3.3)%, just 1.2% lower than when using the entire HD electrode complement. The locations of selected electrodes were consistent with the anatomical reinnervation sites. Additionally, a practical protocol for clinical electrode placement was developed, which does not rely on complex HD EMG experiment and analysis while maintaining a classification accuracy of 88.7+/-4.5%. These outcomes provide important guidelines for practical electrode placement that can promote future clinical application of TMR and EMG PR in the control of multifunctional prostheses.

  15. Multilayer graphene electrodes for one-port surface acoustic wave resonator mass sensor

    Science.gov (United States)

    Leong, Ainan; Swamy, Varghese; Ramakrishnan, N.

    2017-02-01

    A one-port surface acoustic wave (SAW) resonator mass sensor composed of multilayer graphene (MLG) electrodes was investigated by the finite element method (FEM) and analyses were carried out to study the enhancement of sensitivity and the secondary effects caused by MLG electrodes on the performance of the resonator. Unlike metal electrodes, MLG electrode offers elastic loading to the contact surface, as evidenced by the increase in the surface velocity of the SAW device. In terms of the sensitivity of the mass sensor, MLG electrode showed the largest center frequency shift in response to a change in mass loading, as well as when used as a gas sensor to detect volatile organic compounds (VOCs). Also, MLG electrodes offered the least triple transit signal (TTS) and bulk acoustic wave (BAW) generations compared with Al and Au–Cr electrodes. Thus, the one-port SAW resonator with graphene electrodes not only possesses excellent performance characteristics but also gives rise to new opportunities in the development of highly sensitive mass sensors.

  16. Conductive Gel Increases the Small Tumor Treatment With Electrochemotherapy Using Needle Electrodes.

    Science.gov (United States)

    Suzuki, Daniela O H; Marques, Claudia M G; Rangel, Marcelo M M

    2016-07-01

    The combination of chemotherapy drugs and high electric field treatment in local cancer is named electrochemotherapy. The European Standard Operation Procedure of Electrochemotherapy (ESOPE) provides guidelines for treatment of cutaneous and subcutaneous tumors. The electrochemotherapy of numerous tumors varying in sizes is more convenient using needle electrodes. However, ESOPE recommends that needle electrodes are applied to deeper tumors. The application of needle electrodes to treatment of superficial small tumors seems to be practical in electrochemotherapy. Plate electrodes and gel improve the electrochemotherapy efficacy. This technique provides electric field homogeneity in irregularly shaped tissue structures (bulk tumors). We propose an investigation of needle electrode and gel in electrochemotherapy of superficial tumors. In vivo experiment with squamous cell carcinoma (SCC) spontaneous nodules in dog was used to validate the mathematical tissue model. The numerical model considers the tissue conductivity dependent on local electric field. Our studies demonstrated that conductive gel is important for effective treatment of superficial tumors with needle electrodes. The needle electrodes and gel presented reduction of medium current, increased the tumor-free margin, and improved the practical application in relation to plate electrode.

  17. Plasma spark discharge reactor and durable electrode

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Young I.; Cho, Daniel J.; Fridman, Alexander; Kim, Hyoungsup

    2017-01-10

    A plasma spark discharge reactor for treating water. The plasma spark discharge reactor comprises a HV electrode with a head and ground electrode that surrounds at least a portion of the HV electrode. A passage for gas may pass through the reactor to a location proximate to the head to provide controlled formation of gas bubbles in order to facilitate the plasma spark discharge in a liquid environment.

  18. Semiconductor devices having a recessed electrode structure

    Science.gov (United States)

    Palacios, Tomas Apostol; Lu, Bin; Matioli, Elison de Nazareth

    2015-05-26

    An electrode structure is described in which conductive regions are recessed into a semiconductor region. Trenches may be formed in a semiconductor region, such that conductive regions can be formed in the trenches. The electrode structure may be used in semiconductor devices such as field effect transistors or diodes. Nitride-based power semiconductor devices are described including such an electrode structure, which can reduce leakage current and otherwise improve performance.

  19. Semiconductor electrode with improved photostability characteristics

    Science.gov (United States)

    Frank, Arthur J.

    1987-01-01

    An electrode is disclosed for use in photoelectrochemical cells having an electrolyte which includes an aqueous constituent. The electrode includes a semiconductor and a hydrophobic film disposed between the semiconductor and the aqueous constituent. The hydrophobic film is adapted to permit charges to pass therethrough while substantially decreasing the activity of the aqueous constituent at the semiconductor surface thereby decreasing the photodegradation of the semiconductor electrode.

  20. FUEL CELL ELECTRODES FOR ACID MEDIA

    Science.gov (United States)

    fuel cell electrodes for acid media. Activated carbon electrodes were prepared, wetproofed with paraffin or Teflon, and catalyzed with platinum. The wetproofing agent was applied by immersion or electrodeposition and the catalyst applied by chemical decomposition of H2P+Cl6 solutions. Half cell studies with hydrogen anodes and oxygen (air) cathodes showed that electrochemical performance is essentially the same for paraffin and Teflontreated electrodes; however, the life of the Teflon-treated electrodes under equal conditions of load is greater than that for

  1. Electrode structure and methods of making same

    Energy Technology Data Exchange (ETDEWEB)

    Ruud, James Anthony; Browall, Kenneth Walter; Rehg, Timothy Joseph; Renou, Stephane; Striker, Todd-Michael

    2010-04-06

    A method of making an electrode structure is provided. The method includes disposing an electrocatalytic material on an electrode, applying heat to the electrocatalytic material to form a volatile oxide of the electrocatalytic material, and applying a voltage to the electrode to reduce the volatile oxide to provide a number of nano-sized electrocatalytic particles on or proximate to a triple phase boundary, where the number of nano-sized electrocatalytic particles is greater on or proximate to the triple phase boundary than in an area that is not on or proximate to the triple phase boundary, and where the triple phase boundary is disposed on the electrode.

  2. Carbon aerogel electrodes for direct energy conversion

    Science.gov (United States)

    Mayer, Steven T.; Kaschmitter, James L.; Pekala, Richard W.

    1997-01-01

    A direct energy conversion device, such as a fuel cell, using carbon aerogel electrodes, wherein the carbon aerogel is loaded with a noble catalyst, such as platinum or rhodium and soaked with phosphoric acid, for example. A separator is located between the electrodes, which are placed in a cylinder having plate current collectors positioned adjacent the electrodes and connected to a power supply, and a pair of gas manifolds, containing hydrogen and oxygen positioned adjacent the current collectors. Due to the high surface area and excellent electrical conductivity of carbon aerogels, the problems relative to high polarization resistance of carbon composite electrodes conventionally used in fuel cells are overcome.

  3. Encyclopedia of electrochemistry. Vol. 10. Modified electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Bard, A.J. [Texas Univ., Austin, TX (United States). Dept. of Chemistry; Stratmann, M. [Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany); Rubinstein, I. [Weizmann Institute of Science, Rehovot (Israel). Dept. of Materials and Interfaces; Fujihira, Masamichi [Tokyo Institute of Technology, Yokohama (Japan). Dept. of Biomolecular Engineering; Rusling, J.F. (eds.) [Connecticut Univ., Storrs, CT (United States). Dept. of Chemistry, U-60]|[Connecticut Univ., Storrs, CT (United States). Dept. of Pharmacology

    2007-07-01

    This volume contains the following topics: 1. Preparation of monolayer modified electrodes; 2. Layer-by-layer assemblies of thin films on electrodes; 3. Epitaxial electrochemical growth; 5. Other films; 6. Ex-situ methods; 7. In-situ methods; 8. Electron transfer; 9. Charge transport in polymer-modified electrodes; 10. Electrochemical reactions on modified electrodes; 11. Redox-active dendrimers in solution and as films on surfaces; 12. Electrochemical formation of organic thin films; 13. Electron transfer and transport in ordered enzyme layers.

  4. Charged Water Droplets can Melt Metallic Electrodes

    Science.gov (United States)

    Elton, Eric; Rosenberg, Ethan; Ristenpart, William

    2016-11-01

    A water drop, when immersed in an insulating fluid, acquires charge when it contacts an energized electrode. Provided the electric field is strong enough, the drop will move away to the opposite electrode, acquire the opposite charge, and repeat the process, effectively 'bouncing' back and forth between the electrodes. A key implicit assumption, dating back to Maxwell, has been that the electrode remains unaltered by the charging process. Here we demonstrate that the electrode is physically deformed during each charge transfer event with an individual water droplet or other conducting object. We used optical, electron, and atomic force microscopy to characterize a variety of different metallic electrodes before and after drops were electrically bounced on them. Although the electrodes appear unchanged to the naked eye, the microscopy reveals that each charge transfer event yielded a crater approximately 1 micron wide and 50 nm deep, with the exact dimensions proportional to the applied field strength. We present evidence that the craters are formed by localized melting of the electrodes via Joule heating in the metal and concurrent dielectric breakdown of the surrounding fluid, suggesting that the electrode locally achieves temperatures exceeding 3400°C. Present address: Dept. Materials Sci. Engineering, MIT.

  5. Electrode assemblies, plasma apparatuses and systems including electrode assemblies, and methods for generating plasma

    Science.gov (United States)

    Kong, Peter C; Grandy, Jon D; Detering, Brent A; Zuck, Larry D

    2013-09-17

    Electrode assemblies for plasma reactors include a structure or device for constraining an arc endpoint to a selected area or region on an electrode. In some embodiments, the structure or device may comprise one or more insulating members covering a portion of an electrode. In additional embodiments, the structure or device may provide a magnetic field configured to control a location of an arc endpoint on the electrode. Plasma generating modules, apparatus, and systems include such electrode assemblies. Methods for generating a plasma include covering at least a portion of a surface of an electrode with an electrically insulating member to constrain a location of an arc endpoint on the electrode. Additional methods for generating a plasma include generating a magnetic field to constrain a location of an arc endpoint on an electrode.

  6. Polystyrene Based Silver Selective Electrodes

    Directory of Open Access Journals (Sweden)

    Shiva Agarwal

    2002-06-01

    Full Text Available Silver(I selective sensors have been fabricated from polystyrene matrix membranes containing macrocycle, Me6(14 diene.2HClO4 as ionophore. Best performance was exhibited by the membrane having a composition macrocycle : Polystyrene in the ratio 15:1. This membrane worked well over a wide concentration range 5.0×10-6–1.0×10-1M of Ag+ with a near-Nernstian slope of 53.0 ± 1.0 mV per decade of Ag+ activity. The response time of the sensor is <15 s and the membrane can be used over a period of four months with good reproducibility. The proposed electrode works well in a wide pH range 2.5-9.0 and demonstrates good discriminating power over a number of mono-, di-, and trivalent cations. The sensor has also been used as an indicator electrode in the potentiometric titration of silver(II ions against NaCl solution. The sensor can also be used in non-aqueous medium with no significant change in the value of slope or working concentration range for the estimation of Ag+ in solution having up to 25% (v/v nonaqueous fraction.

  7. Desalination with carbon aerogel electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J.C.; Richardson, J.H.; Fix, D.V.

    1996-10-21

    An electrically regenerated electrosorption process known as carbon aerogel CDI was developed for continuously removing ionic impurities from aqueous streams. A salt solution flows in a channel formed by pairs of parallel carbon aerogel electrodes. Each electrode has a very high BET surface area and very low resistivity. After polarization, anions and cations are removed from electrolyte by the electric field and electrosorbed onto the carbon aerogel. The solution is thus separated into two streams, brine and water. Based on this, carbon aerogel CDI appears to be an energy-efficient alternative to evaporation, electrodialysis, and reverse osmosis. The energy required by this process is about QV/2, plus losses. Estimated energy requirement for sea water desalination is 18-27 Wh gal{sup -1}, depending on cell voltage and flow rate. The requirement for brackish water desalination is less, 1.2-2.5 Wh gal{sup -1} at 1600 ppM. This is assuming that stored electrical energy is reclaimed during regeneration.

  8. The rise of organic electrode materials for energy storage.

    Science.gov (United States)

    Schon, Tyler B; McAllister, Bryony T; Li, Peng-Fei; Seferos, Dwight S

    2016-11-07

    Organic electrode materials are very attractive for electrochemical energy storage devices because they can be flexible, lightweight, low cost, benign to the environment, and used in a variety of device architectures. They are not mere alternatives to more traditional energy storage materials, rather, they have the potential to lead to disruptive technologies. Although organic electrode materials for energy storage have progressed in recent years, there are still significant challenges to overcome before reaching large-scale commercialization. This review provides an overview of energy storage systems as a whole, the metrics that are used to quantify the performance of electrodes, recent strategies that have been investigated to overcome the challenges associated with organic electrode materials, and the use of computational chemistry to design and study new materials and their properties. Design strategies are examined to overcome issues with capacity/capacitance, device voltage, rate capability, and cycling stability in order to guide future work in the area. The use of low cost materials is highlighted as a direction towards commercial realization.

  9. Citric acid cycle biomimic on a carbon electrode.

    Science.gov (United States)

    Sokic-Lazic, Daria; Minteer, Shelley D

    2008-12-01

    The citric acid cycle is one of the main metabolic pathways living cells utilize to completely oxidize biofuels to carbon dioxide and water. The overall goal of this research is to mimic the citric acid cycle at the carbon surface of an electrode in order to achieve complete oxidation of ethanol at a bioanode to increase biofuel cell energy density. In order to mimic this process, dehydrogenase enzymes (known to be the electron or energy producing enzymes of the citric acid cycle) are immobilized in cascades at an electrode surface along with non-energy producing enzymes necessary for the cycle to progress. Six enzymatic schemes were investigated each containing an additional dehydrogenase enzyme involved in the complete oxidation of ethanol. An increase in current density is observed along with an increase in power density with each additional dehydrogenase immobilized on an electrode, reflecting increased electron production at the bioanode with deeper oxidation of the ethanol biofuel. By mimicking the complete citric acid cycle on a carbon electrode, power density was increased 8.71-fold compared to a single enzyme (alcohol dehydrogenase)-based ethanol/air biofuel cell.

  10. Modelling of an oesophageal electrode for cardiac function tomography.

    Science.gov (United States)

    Tehrani, J Nasehi; Jin, C; McEwan, A L

    2012-01-01

    There is a need in critical care units for continuous cardiopulmonary monitoring techniques. ECG gated electrical impedance tomography is able to localize the impedance variations occurring during the cardiac cycle. This method is a safe, inexpensive and potentially fast technique for cardiac output imaging but the spatial resolution is presently low, particularly for central locations such as the heart. Many parameters including noise deteriorate the reconstruction result. One of the main obstacles in cardiac imaging at the heart location is the high impedance of lungs and muscles on the dorsal and posterior side of body. In this study we are investigating improvements of the measurement and initial conductivity estimation of the internal electrode by modelling an internal electrode inside the esophagus. We consider 16 electrodes connected around a cylindrical mesh. With the random noise level set near 0.05% of the signal we evaluated the Graz consensus reconstruction algorithm for electrical impedance tomography. The modelling and simulation results showed that the quality of the target in reconstructed images was improved by up to 5 times for amplitude response, position error, resolution, shape deformation and ringing effects with perturbations located in cardiac related positions when using an internal electrode.

  11. Modelling of an Oesophageal Electrode for Cardiac Function Tomography

    Directory of Open Access Journals (Sweden)

    J. Nasehi Tehrani

    2012-01-01

    Full Text Available There is a need in critical care units for continuous cardiopulmonary monitoring techniques. ECG gated electrical impedance tomography is able to localize the impedance variations occurring during the cardiac cycle. This method is a safe, inexpensive and potentially fast technique for cardiac output imaging but the spatial resolution is presently low, particularly for central locations such as the heart. Many parameters including noise deteriorate the reconstruction result. One of the main obstacles in cardiac imaging at the heart location is the high impedance of lungs and muscles on the dorsal and posterior side of body. In this study we are investigating improvements of the measurement and initial conductivity estimation of the internal electrode by modelling an internal electrode inside the esophagus. We consider 16 electrodes connected around a cylindrical mesh. With the random noise level set near 0.05% of the signal we evaluated the Graz consensus reconstruction algorithm for electrical impedance tomography. The modelling and simulation results showed that the quality of the target in reconstructed images was improved by up to 5 times for amplitude response, position error, resolution, shape deformation and ringing effects with perturbations located in cardiac related positions when using an internal electrode.

  12. Influence of implantation on the electrochemical properties of smooth and porous TiN coatings for stimulation electrodes

    Science.gov (United States)

    Meijs, S.; Sørensen, C.; Sørensen, S.; Rechendorff, K.; Fjorback, M.; Rijkhoff, N. J. M.

    2016-04-01

    Objective. To determine whether changes in electrochemical properties of porous titanium nitride (TiN) electrodes as a function of time after implantation are different from those of smooth TiN electrodes. Approach. Eight smooth and 8 porous TiN coated electrodes were implanted in 8 rats. Before implantation, voltage transients, cyclic voltammograms and impedance spectra were recorded in phosphate buffered saline (PBS). After implantation, these measurements were done weekly to investigate how smooth and porous electrodes were affected by implantation. Main results. The electrode capacitance of the porous TiN electrodes decreased more than the capacitance of the smooth electrodes due to acute implantation under fast measurement conditions (such as stimulation pulses). This indicates that protein adhesion presents a greater diffusion limitation for counter-ions for the porous than for the smooth electrodes. The changes in electrochemical properties during the implanted period were similar for smooth and porous TiN electrodes, indicating that cell adhesion poses a similar diffusion limitation for smooth and porous electrodes. Significance. This knowledge can be used to optimize the porous structure of the TiN film, so that the effect of protein adhesion on the electrochemical properties is diminished. Alternatively, an additional coating could be applied on the porous TiN that would prevent or minimize protein adhesion.

  13. SPE Membrane Electrode and Its Application to Chemical Sensor

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The structure and proton conducting mechanism of solid polymer electrolyte (SPE) are described. Since the conductivity of electrolyte is important in SPE electrochemical cell research and development, we investigate quantitatively the conductivity of Nafion membrane and its dependence on temperature and relative humidity. Ex perimental results show that the conductivity of Nafion membrane increases with temperature and relative humidity. We also reports on the preparation and development of SPE membrane electrode with the emphasis on the mix ture pressing method and impregnation-reduction process to prepare SPE composite electrode assemblies and their application to electrochemical sensors. We also investigate and fabricate a potentiometric electrochemical sensor of hydrogen and ethylene to measure the hydrogen and ethylene partial pressure.

  14. An effective gold nanotubes electrode for amperometric biosensor.

    Science.gov (United States)

    Wang, Yunli; Zhu, Yingchun; Liu, Yanyan; Yang, Yu; Ruan, Qichao; Xu, Fangfang

    2010-12-01

    A sensitive and effective amperometric glucose biosensor based on gold nanotubes electrode (GNTE) was investigated. Gold nanotubes (GNTs), which were prepared by electroless plating of the metal within the pores of nanoporous polycarbonate (PC) track-etched membranes, were filled into a hollow teflon cylinder to construct a GNTE. Glucose oxidase (GOD) was immobilized on the electrode via glutaraldehyde cross-linkage method. The electrochemical properties were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The km value of the immobilized glucose oxidase on GNTE was 0.47 mM. The biosensor showed a linear range from 0.4 to 11 mM with excellent sensitivity of 8.77 microA cm(-2) mM(-1) and fast response time within 5 s.

  15. Electrode Materials for Lithium/Sodium-Ion Batteries

    DEFF Research Database (Denmark)

    Shen, Yanbin

    2014-01-01

    Shen systematically investigated the controlled synthesis of electrode materials for lithium/sodium ion batteries. She also investigated their formation mechanisms and structural evolution during the operation of batteries using in situ/operando X-ray diffraction techniques. The research findings...... provide insights into formation mechanisms of Li4Ti5O12 anode material from both hydrothermal and solid-state reaction. The results also contribute to a thorough understanding of the intercalation and decay mechanisms of O3/P2 layered sodium cathode materials in sodium ion batteries.......The synthesis of electrode materials for lithium/sodium ion batteries and their structural stability during lithium/sodium insertion/extraction are the two essential issues that have limited battery application in the fields requiring long cycle life and high safety. During her PhD studies, Yanbin...

  16. Electrocatalytic oxidation behavior of L-cysteine at Pt microparticles modified nanofibrous polyaniline film electrode

    Institute of Scientific and Technical Information of China (English)

    MA Song-jiang; LUO Sheng-lian; ZHOU Hai-hui; KUANG Ya-fei; NING Xiao-hui

    2008-01-01

    Platinum(Pt)/nanofibrous polyaniline(PANI) electrode was prepared by pulse galvanostatic method and characterized by scanning electron microscopy. The electrochemical behavior of L-cysteine at the Pt/nanofibrous PANI electrode was investigated by cyclic voltammetry. The results indicate that the pH value of the solution and the Pt loading of the electrode have great effect on the electrocatalytic property of the Pt/nanofibrous PANI electrode; the suitable Pt loading of the electrode is 600 μg/cm2 and the suitable pH value of the solution is 4.5 for investigating L-cysteine oxidation. The L-cysteine sensor based on the Pt/nanofibrous PANI electrode has a good selectivity, reproducibility and stability. The Pt/nanofibrous PANI electrode is highly sensitive to L-cysteine, and the linear calibration curve for the oxidation of L-cysteine can be observed in the range of 0.2-5.0 mmol/L.

  17. Photoelectrochemical and photocatalytic properties of nanocrystalline TiO II electrodes

    Science.gov (United States)

    Oliveira, Haroldo G.; Nery, Daiane C.; Paschoalino, Matheus P.; Jardim, Wilson F.; Longo, Claudia

    2007-09-01

    The electrochemical and photocatalytic properties of a TiO II film deposited on transparent electrodes were investigated. Its electrochemical behavior was typical of an n-type semiconductor electrode. Its photocatalytic activity, investigated for phenol degradation on an optical bench (area of 1 cm2, 5 mL of solution), revealed small currents (3 μA) and poor total organic carbon (TOC) removal (5 %) when the electrode was biased at + 1.1 V in the dark for 3 h. Under polychromatic irradiation, the electrode presented 25 μA of current and 12 % of phenol degradation. A better performance was achieved for photoelectrocatalytic configuration, when the electrode was irradiated and biased with + 0.6 V. Experiments done under irradiation with a metallic vapor lamp using 9 cm2 electrodes and 10 mL of solution revealed that heterogeneous photocatalysis configuration (HPC) resulted in 50 % of TOC removal, while 85 % was achieved by the electro-assisted process (EHPC). Both the configurations exhibited pseudo-first order kinetics for phenol degradation, but the rate constant was two times that of EHPC. The application of a potential bias to the TiO II porous electrode must enhance the photogenerated electron/hole separation, which minimize the charge recombination and increases its photocatalytic activity towards organic pollutant degradation.

  18. [Research on treatment of high salt wastewater by the graphite and activated carbon fiber composite electrodes].

    Science.gov (United States)

    Zhou, Gui-Zhong; Wang, Zhao-Feng; Wang, Xuan; Li, Wen-Qian; Li, Shao-Xiang

    2014-05-01

    High salinity wastewater is one of the difficulties in the field of wastewater treatment. As a new desalination technology, electrosorption technology has many advantages. This paper studied a new type of carbon-based electrodes, the graphite and activated carbon fiber composite electrodes. And the influencing factors of electrosorption and its desalination effect were investigated. The electrosorption device had optimal desalination effect when the voltage was 1. 6 V, the retention time was 60 min and the plate spacing was 1 cm. The graphite and activated carbon fiber composite electrodes were used to treat the black liquor of refined cotton and sodium copper chlorophyll wastewater to investigate its desalination effect. When the electrodes were used to treat the black liquor of refined cotton after acid treatment, the removal rate of conductivity and COD reached 58. 8% and 75. 6% respectively when 8 pairs of electrodes were used. And when the electrode was used to treat the sodium copper chlorophyll wastewater, the removal rate of conductivity and COD reached higher than 50. 0% and 13. 5% respectively when 6-8 pairs of electrodes were used.

  19. Electrochemical properties of honeycomb-like structured HFBI self-organized membranes on HOPG electrodes.

    Science.gov (United States)

    Yamasaki, Ryota; Takatsuji, Yoshiyuki; Lienemann, Michael; Asakawa, Hitoshi; Fukuma, Takeshi; Linder, Markus; Haruyama, Tetsuya

    2014-11-01

    HFBI (derived from Trichoderma sp.) is a unique structural protein, which forms a self-organized monolayer at both air/water interface and water/solid interfaces in accurate two-dimensional ordered structures. We have taken advantage of the unique functionality of HFBI as a molecular carrier for preparation of ordered molecular phase on solid substrate surfaces. The HFBI molecular carrier can easily form ordered structures; however, the dense molecular layers form an electrochemical barrier between the electrode and solution phase. In this study, the electrochemical properties of HFBI self-organized membrane-covered electrodes were investigated. Wild-type HFBI has balanced positive and negative charges on its surface. Highly oriented pyrolytic graphite (HOPG) electrodes coated with HFBI molecules were investigated electrochemically. To improve the electrochemical properties of this HFBI-coated electrode, the two types of HFBI variants, with oppositely charged surfaces, were prepared genetically. All three types of HFBI-coated HOPG electrode perform electron transfer between the electrode and solution phase through the dense HFBI molecular layer. This is because the HFBI self-organized membrane has a honeycomb-like structure, with penetrating holes. In the cases of HFBI variants, the oppositely charged HFBI membrane phases shown opposite electrochemical behaviors in electrochemical impedance spectroscopy. HFBI is a molecule with a unique structure, and can easily form honeycomb-like structures on solid material surfaces such as electrodes. The molecular membrane phase can be used for electrochemical molecular interfaces.

  20. The effect of asymmetrical electrode form after negative bias illuminated stress in amorphous IGZO thin film transistors

    Science.gov (United States)

    Su, Wan-Ching; Chang, Ting-Chang; Liao, Po-Yung; Chen, Yu-Jia; Chen, Bo-Wei; Hsieh, Tien-Yu; Yang, Chung-I.; Huang, Yen-Yu; Chang, Hsi-Ming; Chiang, Shin-Chuan; Chang, Kuan-Chang; Tsai, Tsung-Ming

    2017-03-01

    This paper investigates the degradation behavior of InGaZnO thin film transistors (TFTs) under negative bias illumination stress (NBIS). TFT devices with two different source and drain layouts were exanimated: one having a parallel format electrode and the other with UI format electrode. UI means that source/drain electrodes shapes is defined as a forked-shaped structure. The I-V curve of the parallel electrode exhibited a symmetric degradation under forward and reverse sweeping in the saturation region after 1000 s NBIS. In contrast, the I-V curve of the UI electrode structure under similar conditions was asymmetric. The UI electrode structure also shows a stretch-out phenomenon in its C-V measurement. Finally, this work utilizes the ISE-Technology Computer Aided Design (ISE-TCAD) system simulations, which simulate the electron field and IV curves, to analyze the mechanisms dominating the parallel and UI device degradation behaviors.

  1. MASS TRANSFER LIMITATION IN DIFFERENT ANODE ELECTRODE SURFACE AREAS ON THE PERFORMANCE OF DUAL CHAMBER MICROBIAL FUEL CELL

    Directory of Open Access Journals (Sweden)

    Majid Sadeqzadeh

    2012-01-01

    Full Text Available In this study, the effect of different electrode surface areas on the performance of dual chamber Microbial Fuel Cells (MFC was investigated. Four different electrodes with 12, 16, 20 and 24 cm2 surface areas were tested in an MFC system. The 20 cm2 electrode generated an output power of 76.5 mW/m2 was found to be the highest among all the electrodes tested. This might be due to better interactions with microorganism and less mass transfer limitation. In addition, this indicates that the chances for attachment of bacteria and generation of electricity in larger electrode surface areas might be limited by mass transport and by higher surface area. The output power generation was then followed by the 16, 12 and 24 cm2 electrodes which generated 69.6, 64.7 and 61.25 mW/m2 electricity, respectively.

  2. Detecting cells on the surface of a silver electrode quartz crystal microbalance using plasma treatment and graft polymerization.

    Science.gov (United States)

    Chou, Hung-Che; Yan, Tsong-Rong; Chen, Ko-Shao

    2009-10-15

    This paper utilizes a silver electrode quartz crystal microbalance (QCM) mass sensor to detect the physiology of cells. This study also investigates the plasma surface modification of silver electrode QCMs through deposition of hexamethyldisilazane (HMDSZ) films as a protection film. To improve the cell growth, this paper also performs post-treatments by surface-grafting acrylic acid (AAc), acrylamide (AAm), and oxygen plasma treatment onto the QCM electrodes. Experimental results indicate that plasma deposition is a useful technique to protect the surface of silver electrodes. This technique extends the unpeeling time of silver electrodes from 1 to 7 days. The hydrophilic silver electrode QCM surface modified by AAm exhibited a better storage time effect than other post-treatments.

  3. Mechanical measurements on lithium phosphorous oxynitride coated silicon thin film electrodes for lithium-ion batteries during lithiation and delithiation

    Science.gov (United States)

    Al-Obeidi, Ahmed; Kramer, Dominik; Boles, Steven T.; Mönig, Reiner; Thompson, Carl V.

    2016-08-01

    The development of large stresses during lithiation and delithiation drives mechanical and chemical degradation processes (cracking and electrolyte decomposition) in thin film silicon anodes that complicate the study of normal electrochemical and mechanical processes. To reduce these effects, lithium phosphorous oxynitride (LiPON) coatings were applied to silicon thin film electrodes. Applying a LiPON coating has two purposes. First, the coating acts as a stable artificial solid electrolyte interphase. Second, it limits mechanical degradation by retaining the electrode's planar morphology during cycling. The development of stress in LiPON-coated electrodes was monitored using substrate curvature measurements. LiPON-coated electrodes displayed highly reproducible cycle-to-cycle behavior, unlike uncoated electrodes which had poorer coulombic efficiency and exhibited a continual loss in stress magnitude with continued cycling due to film fracture. The improved mechanical stability of the coated silicon electrodes allowed for a better investigation of rate effects and variations of mechanical properties during electrochemical cycling.

  4. Curved Microneedle Array-Based sEMG Electrode for Robust Long-Term Measurements and High Selectivity.

    Science.gov (United States)

    Kim, Minjae; Kim, Taewan; Kim, Dong Sung; Chung, Wan Kyun

    2015-07-06

    Surface electromyography is widely used in many fields to infer human intention. However, conventional electrodes are not appropriate for long-term measurements and are easily influenced by the environment, so the range of applications of sEMG is limited. In this paper, we propose a flexible band-integrated, curved microneedle array electrode for robust long-term measurements, high selectivity, and easy applicability. Signal quality, in terms of long-term usability and sensitivity to perspiration, was investigated. Its motion-discriminating performance was also evaluated. The results show that the proposed electrode is robust to perspiration and can maintain a high-quality measuring ability for over 8 h. The proposed electrode also has high selectivity for motion compared with a commercial wet electrode and dry electrode.

  5. Curved Microneedle Array-Based sEMG Electrode for Robust Long-Term Measurements and High Selectivity

    Directory of Open Access Journals (Sweden)

    Minjae Kim

    2015-07-01

    Full Text Available Surface electromyography is widely used in many fields to infer human intention. However, conventional electrodes are not appropriate for long-term measurements and are easily influenced by the environment, so the range of applications of sEMG is limited. In this paper, we propose a flexible band-integrated, curved microneedle array electrode for robust long-term measurements, high selectivity, and easy applicability. Signal quality, in terms of long-term usability and sensitivity to perspiration, was investigated. Its motion-discriminating performance was also evaluated. The results show that the proposed electrode is robust to perspiration and can maintain a high-quality measuring ability for over 8 h. The proposed electrode also has high selectivity for motion compared with a commercial wet electrode and dry electrode.

  6. Design, fabrication and evaluation of a conforming circumpolar peripheral nerve cuff electrode for acute experimental use.

    Science.gov (United States)

    Foldes, Emily L; Ackermann, D Michael; Bhadra, Niloy; Kilgore, Kevin L; Bhadra, Narendra

    2011-03-15

    Nerve cuff electrodes are a principle tool of basic and applied electro-neurophysiology studies and are championed for their ability to achieve good nerve recruitment with low thresholds. We describe the design and method of fabrication for a novel circumpolar peripheral nerve electrode for acute experimental use. This cylindrical cuff-style electrode provides approximately 270° of radial electrode contact with a nerve for each of an arbitrary number of contacts, has a profile that allows for simple placement and removal in an acute nerve preparation, and is designed for adjustment of the cylindrical diameter to ensure a close fit on the nerve. For each electrode, the electrical contacts were cut from 25 μm platinum foil as an array so as to maintain their positions relative to each other within the cuff. Lead wires were welded to each intended contact. The structure was then molded in silicone elastomer, after which the individual contacts were electrically isolated. The final electrode was curved into a cylindrical shape with an inner diameter corresponding to that of the intended target nerve. The positions of these contacts were well maintained during the molding and shaping process and failure rates during fabrication due to contact displacements were very low. Established electrochemical measurements were made on one electrode to confirm expected behavior for a platinum electrode and to measure the electrode impedance to applied voltages at different frequencies. These electrodes have been successfully used for nerve stimulation, recording, and conduction block in a number of different acute animal experiments by several investigators.

  7. The application of hydrogen-palladium electrode for potentiometric acid-base determinations in tetrahydrofuran

    Directory of Open Access Journals (Sweden)

    Jokić Anja B.

    2013-01-01

    Full Text Available The application of the hydrogen-palladium electrode (H2/Pd as the indicator electrode for the determination of relative acidity scale (Es, mV of tetrahydrofuran (THF and the potentiometric titrations of acids in this solvent was investigated. The relative acidity scale tetrahydrofuran was determined from the difference half-neutralization potentials of perchloric acid and tetrabutylammonium hydroxide (TBAH, which were measured by using both H2/Pd-SCE and glass-SCE electrode pairs. The experimentally obtained value of Es scale THF with a H2/Pd-SCE electrode pair was 1155 mV, and those obtained with glass-SCE electrode pair 880 mV. By using a H2/Pd indicator electrode, the individual acids (benzoic acid, palmitic acid, maleic acid, acetyl acetone, α-naphthol and two component acid mixtures (benzoic acid + α-naphthol, palmitic acid + α-naphthol, maleic acid + α-naphthol and maleic acid + ftalic acid were titrated with a standard solution of TBAH. In addition, sodium methylate and potassium hydroxide proved to be very suitable titrating agents for titrating of the individual acids and the acids in mixtures, respectively. The relative error of the determination of acids in mixture was less than 3%. The results are in agreement with those obtained by a conventional glass electrode. The advantages of H2/Pd electrode over a glass electrode in potentiometric acid-base determinations in tetrahydrofuran lie in the following: this electrode gives wider relative acidity scale THF, higher the potential jumps at the titration end-point and relatively fast response time; furthermore, it is very durable, simple to prepare and can be used in the titrations of small volumes. [Projekat Ministarstva nauke Republike Srbije, br.172051

  8. Thin metal layer as transparent electrode in n-i-p amorphous silicon solar cells

    Directory of Open Access Journals (Sweden)

    Theuring Martin

    2014-07-01

    Full Text Available In this paper, transparent electrodes, based on a thin silver film and a capping layer, are investigated. Low deposition temperature, flexibility and low material costs are the advantages of this type of electrode. Their applicability in structured n-i-p amorphous silicon solar cells is demonstrated in simulation and experiment. The influence of the individual layer thicknesses on the solar cell performance is discussed and approaches for further improvements are given. For the silver film/capping layer electrode, a higher solar cell efficiency could be achieved compared to a reference ZnO:Al front contact.

  9. Influence of BaO in perovskite electrodes for the electrochemical reduction of NOx

    DEFF Research Database (Denmark)

    Simonsen, Vibe Louise Ernlund; Johnsen, M.M.; Kammer Hansen, Kent

    2007-01-01

    Using the point electrode method, the effect of BaO on electrochemical reduction of NO (x) was investigated using the perovskites La0.85Sr0.15MnO3 (LSM15) and La0.85Sr0.15CoO3 (LSCo15) as electrode materials. The experiments were carried out in the temperature range 400-600 degrees C in 1% NO and...... favored oxygen reduction compared to reduction of nitric oxide. The LSCO15 electrode containing BaO reacted to form a K2NiF4-structure and was not tested further....

  10. Electrochemical Reduction Behaviour of Zileuton at a Dropping Mercury Electrode by Polarography

    Directory of Open Access Journals (Sweden)

    N. Y. Sreedhar

    2010-01-01

    Full Text Available Electrochemical behaviour of anticancer drug zileuton was investigated by direct current polarography (DCP and differential pulse polarography using a dropping mercury electrode (DME as working electrode and Ag/AgCl reference electrode in universal buffer of pH range from 2.0 to 12.0. The drug was extracted from the dosage forms in dimethyl formamide (DMF. Kinetic parameters such as diffusion co-efficient (D and heterogeneous forward rate constants (k0f,h are evaluated and reported. The differential pulse polarographic method has been developed for the determination of this drug in pharmaceutical formulations.

  11. Alternating Pulse Current in Electrocoagulation for Wastewater Treatment to Prevent the Passivation or Al Electrode

    Institute of Scientific and Technical Information of China (English)

    MAO Xuhui; HONG Song; ZHU Hua; LIN Hui; WEI Lin; GAN Fuxing

    2008-01-01

    A novel current feed style, alternating pulse current, was proposed in electrocoagulation aiming at preventing the passivation of electrode materials. The open circuit potential (OCP) measurements after anodic and cathodic potentiodynamic polarization showed that cathodic polarization could activate Al electrode. The surface of Al electrode after alternating pulse current electrocoagulation was investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), and the results indicate that passivation of Al is not observed. Furthermore, the simulated wastewater treatment tests show that alternating pulse current electrocoagulation has a visible energy saving effect and is worthy of generalization.

  12. Electro-chemical deposition of zinc oxide nanostructures by using two electrodes

    Directory of Open Access Journals (Sweden)

    B. A. Taleatu

    2011-09-01

    Full Text Available One of the most viable ways to grow nanostructures is electro deposition. However, most electrodeposited samples are obtained by three-electrode electrochemical cell. We successfully use a much simpler two-electrode cell to grow different ZnO nanostructures from common chemical reagents. Concentration, pH of the electrolytes and growth parameters like potentials at the electrodes, are tailored to allow fast growth without complexity. Morphology and surface roughness are investigated by Scanning Electron and Air Force Microscopy (SEM and AFM respectively, crystal structure by X-Ray Diffraction measurements (XRD and ZnO stoichiometry by core level photoemission spectroscopy (XPS.

  13. Electrochemical reduction characteristics and the mechanism of chlorinated hydrocarbons at the copper electrode

    Institute of Scientific and Technical Information of China (English)

    XU Wenying; GAO Tingyao; ZHOU Rongfeng; MA Lumin

    2007-01-01

    The electrochemical reduction characteristies of chlorinated hyrdrocarbons were investigated by cyclic voltammetry technique.The reduction mechanism and activity of the chlorinated hydrocarbons at the copper electrode were explored.The relationship between the structure of chlorinated hydrocarbons and their reductive activity were discussed.The experimental results showed that chlorinated alkanes and a portion of chlorinated aromatic hydrocarbons could be reduced directly at the copper electrode.However,chlorinated aromatic hydrocarbons were not easy to reduce at the copper electrode.The results provided a theoretical basis for the catalyzed iron inner electrolysis method.

  14. Coupled diffusion and mechanics in battery electrodes

    Science.gov (United States)

    Eshghinejad, Ahmadreza

    We are living in a world with continuous production and consumption of energy. The energy production in the past decades has started to move away from petrochemical sources toward sustainable sources such as solar, wind and geothermal. Also, the energy consumption is further adapting to the sustainable sources. For instance, in recent years electric vehicles are growing fast that can consume sustainable electric energy stored in their batteries. In this direction, in order to further move toward sustainable energy, materials are becoming increasingly important for storing electric energy. Although, currently the technologies such as Li-ion batteries and solid-oxide fuel cells are commercially available for energy applications, improvements are crucial for the next generation of many other technologies producing or consuming sustainable energies. A critical aspect of the electrochemical activities involved in energy storage technologies such as Li-ion batteries and solid-oxide fuel cells is the diffusion of ions into the electrode materials. This process ultimately governs various functional properties of the batteries such as capacity and charging/discharging rates. The first goal of this dissertation is to develop mathematical tools to analyze the ionic diffusion and investigate its coupling with mechanics in electrodes. For this purpose, a thermodynamics-based modeling framework is developed and numerically solved using two numerical methods to analyze ionic diffusion in heterogeneous and structured electrodes. The next goal of this dissertation is to develop and analyze characterization techniques to probe the electrochemical processes at the nano-scale. To this end, the mathematical models are first employed to model a previously developed Atomic Force Microscopy based technique to probe local electrochemical activities called Electrochemical Strain Microscopy (ESM). This method probes the activities by inducing AC electric field to perturb ionic activities and

  15. Dry Electrodes Facilitate Remote Health Monitoring

    Science.gov (United States)

    2013-01-01

    Johnson Space Center collaborated with Blacksburg, Virginia-based NanoSonic Inc. through the SBIR program to devise a sensor to replace the traditional electrodes used for an electrocardiogram in space. In 2011, NanoSonic started marketing the dry electrodes as well as an EKGear Sensor Shirt, which is being considered for use in hospital garments, athletic apparel, and dive suits.

  16. Lithium metal oxide electrodes for lithium batteries

    Science.gov (United States)

    Thackeray, Michael M.; Kim, Jeom-Soo; Johnson, Christopher S.

    2008-01-01

    An uncycled electrode for a non-aqueous lithium electrochemical cell including a lithium metal oxide having the formula Li.sub.(2+2x)/(2+x)M'.sub.2x/(2+x)M.sub.(2-2x)/(2+x)O.sub.2-.delta., in which 0.ltoreq.xbatteries containing the electrodes.

  17. New electrosurgical ball electrode with nonstick properties

    Science.gov (United States)

    Rondinone, Joseph; Brassell, James; Miller, Scott A., III; Thorne, Jonathan O.; Rondinone, David M.; Safabash, Jason; Vega, Felix

    1998-04-01

    A new electrosurgical ball electrode (SilverBulletTM) has been developed for applying radiofrequency (RF) energy to fuse biological and other materials to tissue surfaces. Specifically, the electrode was developed for use in conjunction with the Fusion Medical Technologies, Inc. gelatin patch (RapiSealTM) for use in pulmonary surgery to seal air leaks, and in solid abdominal organ surgeries to provide hemostatic tamponade. The new electrode allows for the application of RF energy in contact mode without the problems of the electrode sticking to the gelatin patch or the underlying tissue. Designed for use with commercially available electrosurgical handpieces, the electrode consists of a stainless steel connector that fits into the hand- piece, and an electrode assembly made from silver that includes a shank region, and a tip extension extending distally from the shank region. The distal tip of the tip extension is rounded and has a length of about 10 mm. The uniqueness of this electrode is the shank region which has a cross sectional area that is larger than the tip extension. The shank region acts as a heat sink to draw away heat from the tip extension while the tip extension itself remains sufficiently small to access desired target sites and display the desired energy transfer properties. In addition to the physical design, the use of silver as the core element provides a material with high electrical and thermal conductivities. The bulk of the electrode is appropriately insulated.

  18. Electrode kinetics and double layer structure

    NARCIS (Netherlands)

    Timmer, B.; Sluyters-Rehbach, M.; Sluyters, J.H.

    1969-01-01

    Several electrochemical methods have been developed in recent years for the study of the kinetic parameters of electrode reactions. These methods have been used for obtaining an abundance of experimental data for the standard heterogeneous rate constant, ksh, of electrode reactions, mostly limited t

  19. Confinement of reaction components at electrode surface

    Energy Technology Data Exchange (ETDEWEB)

    Luca, Oana R.; Weitekamp, Raymond; Grubbs, Robert H.; Atwater, Harry A.; Mitrovic, Slobodan

    2017-03-14

    A CO.sub.2 reduction electrode includes an active layer on an electrode base. The active layer includes a polymer that includes one or more reaction components selected from a group consisting of a CO.sub.2 reduction catalyst and an activator that bonds CO.sub.2 so as to form a CO.sub.2 reduction intermediate.

  20. Testing of Electrodes, Cells and Short Stacks

    DEFF Research Database (Denmark)

    Hauch, Anne; Mogensen, Mogens Bjerg

    2017-01-01

    electrochemical measurements, and this will be the focus of this chapter. First, the important issue of understanding potential differences and measurements of potentials, which is linked to the choice of proper electrode geometries and test set up configurations for electrode and cell testing, is presented...