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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. Investigation of unoccupied electronic states in PTCDA/Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Sachs, Soenke; Krause, Stefan; Schoell, Achim [Universitaet Wuerzburg (Germany). Experimentelle Physik II; Schwalb, Christian; Marks, Manuel; Hoefer, Ulrich [Universitaet Marburg (Germany). Fachbereich Physik; Umbach, Eberhard [Universitaet Wuerzburg (Germany). Experimentelle Physik II; Forschungszentrum Karlsruhe (Germany)

    2008-07-01

    Energetics, momentum and time evolution of electronic states in organic semiconductors and at their interfaces are fundamental properties that strongly determine the performance in electronic applications. All of these properties can be explored with two-photon photoelectron (2PPE) spectroscopy for occupied and in particular for unoccupied electronic states. In the archetypal system perylene-tetracarboxylic-dianhydride (PTCDA) on single crystal Ag(111) surfaces considerable differences between the electronic states of chemisorbed monolayer films and multilayer films are eminent. These differences, which are due to the altered chemical environment of PTCDA- and as well Ag-derived states in the vicinity of the interface, can be tracked with 2PPE. A new unoccupied interface state at the Ag/PTCDA interface with a free-electron like dispersion and comparatively short lifetime is detected that influences the charge injection characteristics considerably. The results of the 2PPE spectroscopy are compared to the results of complementary spectroscopies like UPS, IPES, and STS.

  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. Adsorption of bay-substituted perylene bisimide dyes on Ag(111) investigated by PES and NEXAFS

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, Markus; Krause, Stefan; Haeming, Marc; Schoell, Achim [Universitaet Wuerzburg (Germany). Experimentelle Physik II; Schmidt, Ruediger; Wuerthner, Frank [Universitaet Wuerzburg (Germany). Institut fuer Organische Chemie; Reinert, Friedrich [Universitaet Wuerzburg (Germany). Experimentelle Physik II; Gemeinschaftslabor fuer Nanoanalytik, Forschungszentrum Karlsruhe (Germany)

    2009-07-01

    Perylene tetracarboxylic acid bisimides (PBI) are among the best available n-conducting organic materials. Halogen substituents attached to the perylene bay positions change the molecular structure by introducing a twist angle into the usually planar perylene backbone. This influences the optical properties, the stacking of the molecules, as well as the electronic properties. Moreover, the molecular conformation is also expected to effect the interaction with metal contacts, an aspect of crucial importance for electronic devices. We report on a high resolution photoemission (PES) and x-ray absorption (NEXAFS) study of the electronic structure and the molecular orientation of ultra-thin films of the planer PBI-H{sub 4}, and the core twisted PBI-Cl{sub 4} on Ag(111) substrates. In the monolayer regime, substantial changes in the UPS and XPS data with respect to the bulk samples clearly indicate a covalent interaction at the interface. In the valence regime charge transfer induced occupied states are observed at the Fermi-level. This is corroborated by the NEXAFS results, which allow probing a possible change of the molecular conformation due to the interfacial interaction.

  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...

  6. 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.

  7. Point defects in epitaxial silicene on Ag(111) surfaces

    Science.gov (United States)

    Liu, Hongsheng; Feng, Haifeng; Du, Yi; Chen, Jian; Wu, Kehui; Zhao, Jijun

    2016-06-01

    Silicene, a counterpart of graphene, has achieved rapid development due to its exotic electronic properties and excellent compatibility with the mature silicon-based semiconductor technology. Its low room-temperature mobility of ∼100 cm2 V‑1 s‑1, however, inhibits device applications such as in field-effect transistors. Generally, defects and grain boundaries would act as scattering centers and thus reduce the carrier mobility. In this paper, the morphologies of various point defects in epitaxial silicene on Ag(111) surfaces have been systematically investigated using first-principles calculations combined with experimental scanning tunneling microscope (STM) observations. The STM signatures for various defects in epitaxial silicene on Ag(111) surface are identified. In particular, the formation energies of point defects in Ag(111)-supported silicene sheets show an interesting dependence on the superstructures, which, in turn, may have implications for controlling the defect density during the synthesis of silicene. Through estimating the concentrations of various point defects in different silicene superstructures, the mystery of the defective appearance of \\sqrt{13}× \\sqrt{13} and 2\\sqrt{3}× 2\\sqrt{3} silicene in experiments is revealed, and 4 × 4 silicene sheet is thought to be the most suitable structure for future device applications.

  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...

  9. Current-induced switching of PTCDA on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Neucheva, Olga; Weiss, Christian; Temirov, Ruslan; Tautz, Frank Stefan [Institut fuer Bio- und Nanosysteme (IBN-3), Forschungszentrum Juelich, 52425 Juelich (Germany); JARA-Fundamental of Future Information Technology, Forschungszentrum Juelich, 52425 Juelich (Germany)

    2009-07-01

    A low temperature scanning tunneling microscope (LT-STM) has been used to investigate electron transport through a single PTCDA molecule on Ag(111). Under certain conditions, one of the carboxylic oxygen atoms of the PTCDA molecule establishes a chemical bond with the STM tip, forming a covalently bound single molecular junction. In this contribution, we investigate the process of contact formation as a function of parameters such as distance, bias voltage and electrical current through the molecular junction. In a narrow distance and voltage interval, bistable switching of the oxygen atom between a high- and low-conductance state is observed. The implications of this observation are discussed.

  10. The instability of silicene on Ag(111)

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    Acun, A.; Poelsema, B.; Zandvliet, H. J. W.; Gastel, R. van [Physics of Interfaces and Nanomaterials, MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)

    2013-12-23

    We have used low energy electron microscopy to directly visualize the formation and stability of silicene layers on a Ag(111) substrate. Theoretical calculations call into question the stability of this graphene-like analog of silicon. We find that silicene layers are intrinsically unstable against the formation of an “sp{sup 3}-like” hybridized, bulk-like silicon structure. The irreversible formation of this bulk-like structure is triggered by thermal Si adatoms that are created by the silicene layer itself. To add injury to insult, this same instability prevents the formation of a fully closed silicene layer or a thicker bilayer, rendering the future large-scale fabrication of silicene layers on Ag substrates unlikely.

  11. Hindered rotational physisorption states of H2 on Ag(111) surfaces.

    Science.gov (United States)

    Kunisada, Y; Kasai, H

    2015-07-15

    We have investigated the physisorption states of H2 on Ag(111) surfaces. To clarify the accurate adsorption properties of H2 on Ag(111), we performed first-principles calculations based on spin-polarized density functional theory (DFT) with the semiempirical DFT-D2 method and the newly-developed exchange functional with the non-local correlation functional vdW-DF2 (rev-vdW-DF2). We constructed exhaustive potential energy surfaces, and revealed that non-negligible out-of-plane potential anisotropy with a perpendicular orientation preference exists even for H2 physisorption on planar Ag(111), as predicted by previous results of resonance-enhanced multiphoton ionization spectroscopy and temperature-programmed desorption experiments. Therefore, the molecular rotational ground states of ortho-H2 split into two energy levels in the anisotropic potential. The obtained adsorption energy and the number of bound states, including the zero-point energies and the rotational energy shift, agree with diffractive and rotationally mediated selective adsorption scattering resonance measurements. The origin of the potential anisotropy on Ag(111) is a combination of the London dispersion interaction and the virtual transition of the metal electron to the unoccupied molecular state. PMID:26151425

  12. Two-dimensional pentacene:3,4,9,10-perylenetetracarboxylic dianhydride supramolecular chiral networks on Ag(111).

    Science.gov (United States)

    Chen, Wei; Li, Hui; Huang, Han; Fu, Yuanxi; Zhang, Hong Liang; Ma, Jing; Wee, Andrew Thye Shen

    2008-09-17

    Self-assembly of the binary molecular system of pentacene and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Ag(111) has been investigated by low-temperature scanning tunneling microscopy, molecular dynamics (MD), and density functional theory (DFT) calculations. Well-ordered two-dimensional (2D) pentacene:PTCDA supramolecular chiral networks are observed to form on Ag(111). The 2D chiral network formation is controlled by the strong interfacial interaction between adsorbed molecules and the underlying Ag(111), as revealed by MD and DFT calculations. The registry effect locks the adsorbed pentacene and PTCDA molecules into specific adsorption sites due to the corrugation of the potential energy surface. The 2D supramolecular networks are further constrained through the directional CO...H-C multiple intermolecular hydrogen bonding between the anhydride groups of PTCDA and the peripheral aromatic hydrogen atoms of the neighboring pentacene molecules. PMID:18722423

  13. 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.

  14. Magnetic and electronic structure of Mn nanostructures on Ag(111) and Au(111)

    Science.gov (United States)

    Cardias, R.; Bezerra-Neto, M. M.; Ribeiro, M. S.; Bergman, A.; Szilva, A.; Eriksson, O.; Klautau, A. B.

    2016-01-01

    We present results of the electronic and magnetic structure of Mn nanowires adsorbed on Ag(111) and Au(111) surfaces. For finite Mn nanowires on Ag(111) and Au(111) surfaces, our ab initio results show that the large difference between the spin-orbit splitting of these two surfaces leads to completely different magnetic configurations. The magnetic ordering for Mn nanowires adsorbed on Ag(111) is governed by the strong exchange interaction between Mn adatoms. For Mn nano-chains on Au(111), the competition between Heisenberg and Dzyaloshinskii-Moriya interactions leads to a complex magnetic structure of the clusters considered here. Among the more conspicuous results we note a spin-spiral helical type for the nanowire with seven atoms, and a complex magnetic configuration incommensurate with the substrate lattice for a double-sized Mn wire. The effect of the structural relaxation is also investigated, showing sensitivity of the exchange interactions to the bond distance to the substrate. We also demonstrate that small changes in the band filling of these Mn chains results in drastically different changes of the interatomic exchange. Finally, we show that dispersion of the electronic energy spectrum is possible even in nanostructures with bounded spatial extension.

  15. Electron dynamics at the PTCDA/Ag(111) interface studied with 2PPE

    Energy Technology Data Exchange (ETDEWEB)

    Marks, Manuel; Schwalb, Christian; Hoefer, Ulrich [Fachbereich Physik und Zentrum fuer Materialwissenschaften, Philipps-Universitaet Marburg (Germany); Sachs, Soenke; Schoell, Achim [Universitaet Wuerzburg (Germany). Experimentelle Physik II; Umbach, Eberhard [Universitaet Wuerzburg (Germany). Experimentelle Physik II; Forschungszentrum Karlsruhe (Germany)

    2008-07-01

    We investigated epitaxial grown PTCDA (3,4,9,10-perylene-tetracarboxylic acid-dianhydride) on the Ag(111) surface as model system for a metal-organic interface by means of time- and angle-resolved two-photon photoemission (2PPE). In the presence of thin PTCDA films, an unoccupied state with an effective electron mass of 0.39 m{sub e} is observed in the projected band gap of Ag 0.6 eV above E{sub F}. Its inelastic electronic lifetime is {approx_equal}50 fs and the state has an appreciable metallic character, significantly exceeding that of the image-potential states. We assign the new state to a mixture of the former Ag(111) Shockley surface state and the LUMO+1 of the first PTCDA monolayer (ML). In contrast to this interface state, which changes only weakly with PTCDA coverage, the binding energy of the first image-potential state shows a strong dependence. It increases by 135 meV for 1 ML, compared to clean Ag(111), but with absorption of the second ML, a subsequent drop of -70 meV relative to the clean surface occurs. A similar coverage dependence can be seen in the effective electron mass, which decreases by 20% from the first to the second PTCDA layer.

  16. Enhanced Rashba spin-orbit splitting in Bi/Ag(111) and Pb/Ag(111) surface alloys from first principles

    OpenAIRE

    Bihlmayer, G; Blügel, S.; Chulkov, E. V.

    2007-01-01

    We present first-principles calculations of a (root 3x root 3) R30 degrees Bi/Ag (111)-ordered surface alloy, which has recently been investigated experimentally using angle-resolved photoemission spectroscopy. The surface states in the L-projected bulk band gap show a Rashba-type spin-orbit splitting which is three times larger than what has been observed on a clean Bi (111) surface. This large enhancement can be explained by the strong distortion of the surface-state wave function which is ...

  17. Late growth stages and post-growth diffusion in organic epitaxy: PTCDA on Ag(111)

    OpenAIRE

    Krause, B.; Duerr, A. C.; Schreiber, F.; Dosch, H.; Seeck, O.H.

    2004-01-01

    The late growth stages and the post-growth diffusion of crystalline organic thin films have been investigated for 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Ag(111), a model system in organic epitaxy. In situ x-ray measurements at the anti-Bragg point during the growth show intensity oscillations followed by a time-independent intensity which is independent of the growth temperature. At T > 350 K, the intensity increases after growth up to a temperature-dependent saturation value...

  18. Self-assembled rows of Ni porphyrin dimers on the Ag(111) surface

    OpenAIRE

    SENGE, Mathias; SERGEEVA, NATALIA

    2010-01-01

    PUBLISHED The growth and ordering of 5-(10,15,20-triphenylporphyrinatonickel(II))dimer (NiTPP-dimer) molecules on the Ag(111) surface have been investigated using scanning tunnelling microscopy/spectroscopy (STM/STS) and low-energy electron diffraction (LEED). At one monolayer (ML) coverage the NiTPP-dimer forms a well-ordered close-packed molecular layer in which the porphyrin molecules have a flat orientation with the molecular plane lying parallel to the substrate. STM and LEED data obt...

  19. Electron spectroscopy of organic heterointerfaces: SnPc/PTCDA/Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Greif, Michael; Haeming, Marc; Wiessner, Michael; Schoell, Achim [Universitaet Wuerzburg, Experimentelle Physik VII, D-97074 Wuerzburg (Germany); Reinert, Friedrich [Universitaet Wuerzburg, Experimentelle Physik VII, D-97074 Wuerzburg (Germany); FZK Karlsruhe, Gemeinschaftslabor fuer Nanoanalytik, D-76021 Karlsruhe (Germany)

    2010-07-01

    Heterointerfaces between different organic molecules are an issue of great technologic relevance. However, structurally well-defined ultrathin interfaces which are suited for the investigation with surface sensitive techniques are difficult to prepare. In order to exploit its potential as a model system in this respect we have investigated hetero-layers consisting of tin-phthalocyanine (SnPc) and perylene-tetracarboxylic acid dianhydride (PTCDA) deposited on clean Ag(111) surfaces with photoelectron spectroscopy (XPS and UPS), X-ray absorption and low energy electron diffraction (LEED). The spectroscopic signatures of the two compounds can be distinguished unambiguously in the core and valence spectra. For ultra-thin SnPc layers deposited on a single layer of PTCDA on Ag(111) structural information can be derived from angle resolved XPS and NEXAFS. The data indicates that a closed monomolecular layer of flat lying SnPc is established. This is corroborated by the UPS spectra which show a characteristic splitting of the SnPc HOMO signal due to dimer formation only for SnPc coverages beyond one layer. Moreover, LEED was applied in order to investigate the lateral ordering.

  20. Electronic structure of ultra thin organic hetero-interfaces - SnPc/PTCDA/Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Schoell, Achim; Haeming, Marc; Greif, Michael; Wiessner, Michael [Universitaet Wuerzburg, Experimentelle Physik VII, D-97074 Wuerzburg (Germany); Reinert, Friedrich [Universitaet Wuerzburg, Experimentelle Physik VII, D-97074 Wuerzburg (Germany); Karlsruhe Institute of Technology, Gemeinschaftslabor fuer Nanoanalytik, D-76021 Karlsruhe (Germany)

    2010-07-01

    While the interfaces of molecules to a substrate have been studied extensively, knowledge about the interface between different molecular compounds is still relatively scarce. This is to some extend caused by the fact that these interfaces, which are of great relevance for opto-electronic devices consisting out of multiple organic compounds, are more complicated to access experimentally. Structurally well defined model systems, which allow for a systematic and detailed investigation of the interface characteristics, are thus of great importance. In this work we provide data from x-ray absorption and photoelectron spectroscopy on the organic heterolayer system tin-phthalocyanine (SnPc)/perylen-tetracarboxylicacid dianhydride (PTCDA). We show, that SnPc, prepared on a Ag(111) surface precovered by a monolayer of PTCDA, forms a well defined interface with a closed first layer of flat lying molecules. Moreover, the bonding of the SnPc molecules to the PTCDA interlayer is clearly non-covalent and a detailed inspection of the valence spectra shows that the respective molecular signatures can be distinguished well. The SnPc/PTCDA/Ag(111) system is thus well-suited for further investigations employing complicated techniques.

  1. Luminescence from 3,4,9,10-perylenetetracarboxylic dianhydride on Ag(111) surface excited by tunneling electrons in scanning tunneling microscopy.

    Science.gov (United States)

    Ino, Daisuke; Yamada, Taro; Kawai, Maki

    2008-07-01

    The electronic excitations induced with tunneling electrons into adlayers of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Ag(111) have been investigated by in situ fluorescence spectroscopy in scanning tunneling microscopy (STM). A minute area of the surface is excited by an electron tunneling process in STM. Fluorescence spectra strongly depend on the coverage of PTCDA on Ag(111). The adsorption of the first PTCDA layer quenches the intrinsic surface plasmon originated from the clean Ag(111). When the second layer is formed, fluorescence spectra are dominated by the signals from PTCDA, which are interpreted as the radiative decay from the manifold of first singlet excited state (S(1)) of adsorbed PTCDA. The fluorescence of PTCDA is independent of the bias polarity. In addition, the fluorescence excitation spectrum agrees with that by optical excitation. Both results indicate that S(1) is directly excited by the inelastic impact scattering of electrons tunneling within the PTCDA adlayer. PMID:18624490

  2. Dynamical bi-stability of single-molecule junctions: A combined experimental/theoretical study of PTCDA on Ag(111)

    OpenAIRE

    Brumme, Thomas; Neucheva, Olga; Toher, Cormac; Gutiérrez, Rafael; Weiss, Christian; Temirov, Ruslan; Greuling, Andreas; Kaczmarski, Marcin; Rohlfing, Michael; Tautz, Stefan; Cuniberti, Gianaurelio

    2010-01-01

    The dynamics of a molecular junction consisting of a PTCDA molecule between the tip of a scanning tunneling microscope and a Ag(111) surface have been investigated experimentally and theoretically. Repeated switching of a PTCDA molecule between two conductance states is studied by low-temperature scanning tunneling microscopy for the first time, and is found to be dependent on the tip-substrate distance and the applied bias. Using a minimal model Hamiltonian approach combined with density-fun...

  3. Dynamical bistability of single-molecule junctions: A combined experimental and theoretical study of PTCDA on AG(111)

    OpenAIRE

    Brumme, T.; Neucheva, O.A.; Cuniberti, G.; Toher, C.; Gutiérrez, R.; Weiss, C.(Theory Center, Jefferson Lab, Newport News, VA, 23606, U.S.A.); Temirov, R.; Greuling, A.; M. Kaczmarski; Rohlfing, M.; Tautz, F. S.

    2011-01-01

    The dynamics of a molecular junction consisting of a PTCDA molecule between the tip of a scanning tunneling microscope and a Ag(111) surface have been investigated experimentally and theoretically. Repeated switching of a PTCDA molecule between two conductance states is studied by low-temperature scanning tunneling microscopy for the first time and is found to be dependent on the tip-substrate distance and the applied bias. Using a minimal model Hamiltonian approach combined with density-func...

  4. Thermal stability and partial dewetting of crystalline organic thin films: 3,4,9,10-perylenetetracarboxylic dianhydride on Ag(111)

    OpenAIRE

    Krause, B.; Dürr, A. C.; Schreiber, F.; Dosch, H.; Seeck, O

    2003-01-01

    The thermal stability and dewetting effects of crystalline organic thin films on inorganic substrates have been investigated for a model system for organic epitaxy, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Ag(111). The thin films deposited under a variety of growth conditions have been annealed stepwise and studied by in situ x-ray diffraction and noncontact atomic force microscopy. It has been found that comparatively smooth films deposited at temperatures T(g)less than or sim...

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

    Science.gov (United States)

    Studener, F; Müller, K; Marets, N; Bulach, V; Hosseini, M W; Stöhr, M

    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. PMID:25770515

  6. 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.

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

    International Nuclear Information System (INIS)

    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

  8. 2PPE measurements of PTCDA on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Schwalb, Christian; Hoefer, Ulrich [Fachbereich Physik und Zentrum fuer Materialwissenschaften, Philipps-Universitaet Marburg, D-35032 Marburg (Germany); Sachs, Soenke; Schoell, Achim; Umbach, Eberhard [Universitaet Wuerzburg, Experimentelle Physik II, D- 97074 Wuerzburg (Germany)

    2007-07-01

    Electron transfer at a metal-molecule interface plays an important role in many chemical disciplines, ranging from molecular electronics to surface photochemistry. We present measurements using time-resolved two-photon photoemission (2PPE) to probe the energetics and dynamics of electronically excited states in epitaxial 3,4,9,10perylenetetracarboxylic acid-dianhydride (PTCDA) thin films on a Ag(111) surface for a thickness range from one to ten monolayers. These measurements allow the identification and determination of the energetic positions for the lowest unoccupied molecular orbital (LUMO), and LUMO+1. Angle-resolved 2PPE-measurements show a weak dispersion for the LUMO of {proportional_to}150 meV. Our experiments indicate that the excitation process for the LUMO is mainly done by electrons from the Ag(111) substrate. Time-resolved measurements probing the dynamics of the system show an increasing of lifetime for the LUMO for increasing layer thickness from 40 to 80 fs.

  9. Change in surface states of Ag(111) thin films upon adsorption of a monolayer of PTCDA organic molecules

    International Nuclear Information System (INIS)

    The change in the electronic structure of silver thin films of different thicknesses with the Ag( 111) orientation due to the interaction with an adsorbed monolayer of ordered organic molecules of 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) has been investigated in terms of density functional theory. It has been shown that one of the two surface states of the pure films transforms into an unocc upied interface state due to the interaction so that all the main features of the initial state are retained. The relation of the resulting state to the unoccupied state experimentally observed in the PTCDA/Ag( 111 ) system by scanning tunneling and two-photon photoemission spectroscopy has been discussed.

  10. C60 chain phases on ZnPc/Ag(111) surfaces: Supramolecular organization driven by competing interactions.

    Science.gov (United States)

    Jin, W; Liu, Q; Dougherty, D B; Cullen, W G; Reutt-Robey, J E; Weeks, J; Robey, S W

    2015-03-14

    Serpentine chain C60 phases were observed in scanning tunneling microscopy (STM) images of C60 layers on zinc phthalocyanine (ZnPc) or pentacene covered Ag(111) and Au(111) surfaces. This low-density, quasi-one-dimensional organization contrasts starkly with the close-packed hexagonal phases observed for C60 layers on bare metal substrates. STM was employed to perform a detailed investigation of these chain structures for C60/ZnPc/Ag(111) heterolayers. Motivated by the similarity of these chain phases, and the chain and stripe organization occurring in dipole-fluid systems, we investigated a model based on competing van der Waals attractions and electrostatic repulsions between C60 molecules as an explanation for the driving force behind these monolayer phases. Density functional theory (DFT) calculations revealed significant charge transfer to C60 from the Ag(111) substrate, through the intervening ZnPc layer, inducing electrostatic interactions between C60 molecules. Molecular dynamics simulations performed with attractive van der Waals interactions plus repulsive dipole-dipole interactions reproduced the C60 chain phases with dipole magnitudes consistent with DFT calculations. PMID:25770499

  11. Raman analysis of first monolayers of PTCDA on Ag(111)

    International Nuclear Information System (INIS)

    We present a Raman spectroscopic analysis of the bonding properties of organic molecules on Ag(111) surfaces as a model system for organic semiconductor/metal contacts. The planar molecule 3,4,9,10-perylene-tetracarboxylicacid-dianhydride (PTCDA) is used in the present study due to its high electronic mobility and thermal stability. Vibrational signatures of the first monolayer in direct contact with the metal, especially the modes at 1310 and 1575 cm-1, are found to be shifted to lower frequencies. First principles calculations result in corresponding mode patterns, which are essentially located in the centre of the molecule thus indicating the area, where major metal interaction takes place. Furthermore, upon annealing at 450 K the vibrational frequencies of the second monolayer are modified with respect to bulk PTCDA, which reflect particular changes of the bonding situation of this layer. For subsequent layers bulk-like behaviour is observed

  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...... correspond to three distinct binding configurations. From a detailed analysis of the relative distance between neighboring three-lobed molecules we determine the adsorption site. Applying the lateral manipulation technique ws demonstrate that the molecule can be pulled, slid or pushed by the tip 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! their...

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

    DEFF Research Database (Denmark)

    Lin, Rong; 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...... correspond to three distinct binding configurations. From a detailed analysis of the relative distance between neighboring three-lobed molecules we determine the adsorption site. Applying the lateral manipulation technique ws demonstrate that the molecule can be pulled, slid or pushed by the tip 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! their...

  14. DFT study of PTCDA on Ag(111) including a STM tip

    Energy Technology Data Exchange (ETDEWEB)

    Greuling, Andreas; Kaczmarski, Marcin; Rohlfing, Michael [Universitaet Osnabrueck, Fachbereich Physik, Barbarastrasse 7, 49069 Osnabrueck (Germany)

    2010-07-01

    Any progress in the field of molecular electronics requires a detailed knowledge of conduction through molecules. As a prerequisite, detailed knowledge of the geometrical structure of a model system like the system PTCDA on Ag(111) probed with a STM tip is of big importance. In experiment it is possible to peel the PTCDA from the surface by using a STM tip above a corner oxygen atom. Furthermore, the molecule flips from the surface to the tip and back under certain tip-surface distance and voltage conditions. Here, we investigate these mechanisms by employing ab initio calculations applying the widely used SIESTA code. Using Density Functional Theory (DFT) in the Local Density Approximation (LDA) we present calculated geometries for the process of peeling of the molecule. Additionally we show tip-surface interaction potentials also considering the influence of a homogeneous electrical field.

  15. 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.

  16. Exploring Ag(111) Substrate for Epitaxially Growing Monolayer Stanene: A First-Principles Study

    Science.gov (United States)

    Gao, Junfeng; Zhang, Gang; Zhang, Yong-Wei

    2016-07-01

    Stanene, a two-dimensional topological insulator composed of Sn atoms in a hexagonal lattice, is a promising contender to Si in nanoelectronics. Currently it is still a significant challenge to achieve large-area, high-quality monolayer stanene. We explore the potential of Ag(111) surface as an ideal substrate for the epitaxial growth of monolayer stanene. Using first-principles calculations, we study the stability of the structure of stanene in different epitaxial relations with respect to Ag(111) surface, and also the diffusion behavior of Sn adatom on Ag(111) surface. Our study reveals that: (1) the hexagonal structure of stanene monolayer is well reserved on Ag(111) surface; (2) the height of epitaxial stanene monolayer is comparable to the step height of the substrate, enabling the growth to cross the surface step and achieve a large-area stanene; (3) the perfect lattice structure of free-standing stanene can be achieved once the epitaxial stanene monolayer is detached from Ag(111) surface; and finally (4) the diffusion barrier of Sn adatom on Ag(111) surface is found to be only 0.041 eV, allowing the epitaxial growth of stanene monolayer even at low temperatures. Our above revelations strongly suggest that Ag(111) surface is an ideal candidate for growing large-area, high-quality monolayer stanene.

  17. Manipulation/Extraction of Adatom on a Mound: AG(111)

    International Nuclear Information System (INIS)

    We present results of an extensive study of the manipulation/extraction of an atom from a small Ag mound on Ag(111) using a Ag tip. Molecular dynamics (MD) and molecular static (MS) simulations were carried out using interaction potentials from the embedded atom method. In order to evaluate the manipulation capabilities of the tip, we first examine in detail the characteristics of the energy landscape in the absence of the tip. We find that the energy barrier for the extraction of the Ag atom, either through lateral (sliding downwards) or through vertical (climbing upwards) diffusion, to be about 0.3 eV. We show that the presence of the tip lowers the energy barrier for both lateral and vertical diffusion. We find that when the tip is above the edge of the mound (at a height of 2.43 A A from the Ag atom) the barrier for diffusion drops to 0.032 eV for lateral and 0.18 eV for vertical manipulation. We discuss the effect of the tip shape and geometry on the energetics, and present a detailed explanation of how the adatom is extracted from a mound in good agreement with experimental observations

  18. 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

  19. Surface stress and its consequences: In-situ study of PTCDA induced faceting of vicinal Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Pollinger, Florian; Vrdoljak, Pavo; Schmitt, Stefan; Kumpf, Christian; Schoell, Achim [Universitaet Wuerzburg, Experimentelle Physik II, Wuerzburg (Germany); Tian, Zhen; Sander, Dirk; Kirschner, Juergen [Max-Planck-Institut fuer Mikrostrukturphysik, Halle (Germany); Umbach, Eberhard [Universitaet Wuerzburg, Experimentelle Physik II, Wuerzburg (Germany); Forschungszentrum Karlsruhe (Germany)

    2008-07-01

    Adsorption of organic molecules on vicinal metal surfaces is known to promote faceting and self-organized ordering on mesoscopic scales. The adsorption of PTCDA on vicinal Ag(111) surfaces leads to grating-like structures after annealing. The system PTCDA/Ag(10 8 7) was investigated using two complementary techniques: An optical cantilever bending technique sensitive to changes in surface stress and spot-profile analysis low energy electron diffraction (SPA-LEED) to monitor the development of the interface structure during faceting. The data was compared to the related, non-faceting system PTCDA on Ag(111). Overall, we find a surface stress change of 0.7 N/m due to the PTCDA-induced faceting, whereas the adsorption of PTCDA without faceting induces a change of 0.4 N/m. Moreover, the data allows an explicit and unambiguous correlation of the surface stress change to the structural and morphological evolution of the interface during the adsorption of the PTCDA adlayer. In conclusion, the results provide experimental evidence for significant surface stress induced by an organic adsorbate and for its importance for faceting and long-range ordering at metal-organic interfaces.

  20. Substrate dependent bonding distances of PTCDA - A comparative XSW study on Cu(111) and Ag(111)

    OpenAIRE

    Gerlach, A; Sellner, S.; Schreiber, F.; Koch, N; Zegenhagen, J.

    2006-01-01

    We study the adsorption geometry of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) on Ag(111) and Cu(111) using X-ray standing waves. The element-specific analysis shows that the carbon core of the molecule adsorbs in a planar configuration, whereas the oxygen atoms experience a non-trivial and substrate dependent distortion. On copper (silver) the carbon rings resides 2.66 A (2.86 A) above the substrate. In contrast to the conformation on Ag(111), where the carboxylic oxygen atoms are...

  1. 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.

  2. Tailoring metal-organic hybrid interfaces: heteromolecular structures with varying stoichiometry on Ag(111)

    Science.gov (United States)

    Stadtmüller, Benjamin; Henneke, Caroline; Soubatch, Serguei; Tautz, F. Stefan; Kumpf, Christian

    2015-02-01

    The physical properties of interfaces between organic semiconductors and metal surfaces crucially influence the performance of organic electronic devices. In order to enable the tailoring of such metal-organic hybrid interfaces we study the adsorption of heteromolecular thin films containing the prototypical molecules copper-II-phthalocyanine (CuPc) and 3,4,9,10-perylene-tetra-carboxylic-dianhydride (PTCDA) on the Ag(111) surface. Here, we demonstrate how the lateral order can be tuned by changing the relative coverage of both adsorbates on the surface. The layer growth has been studied in real time with low energy electron microscopy, and—for different stoichiometries—the geometric properties of three heteromolecular submonolayer phases have been investigated using high resolution low energy electron diffraction and low temperature scanning tunneling microscopy. Furthermore, we have used a theoretical approach based on van der Waals and electrostatic potentials in order to reveal the influence of the intermolecular and the molecule-substrate interactions on the lateral order of heteromolecular films.

  3. Interface dipoles of organic molecules on Ag(111) in hybrid density-functional theory

    Science.gov (United States)

    Hofmann, Oliver T.; Atalla, Viktor; Moll, Nikolaj; Rinke, Patrick; Scheffler, Matthias

    2013-12-01

    We investigate the molecular acceptors 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) and 4,5,9,10-pyrenetetraone (PYTON) on Ag(111) using density-functional theory (DFT). For two groups of the Heyd-Scuseria-Ernzerhof (HSE(α, ω)) family of exchange-correlation functionals (ω = 0 and 0.2 Å) we study the isolated components as well as the combined systems as a function of the amount of exact-exchange (α). We find that hybrid functionals favour electron transfer to the adsorbate. Comparing with experimental work function data, for α ≈ 0.25 we report a notable but small improvement over (semi) local functionals for the interface dipole. Although Kohn-Sham eigenvalues are only approximate representations of ionization energies, incidentally, at this value also the density of states agrees well with the photoelectron spectra. However, increasing α to values for which the energy of the lowest unoccupied molecular orbital matches the experimental electron affinity in the gas phase worsens both the interface dipole and the density of states. Our results imply that semi-local DFT calculations may often be adequate for conjugated organic molecules on metal surfaces and that the much more computationally demanding hybrid functionals yield only small improvements.

  4. Self-Assembly of Tetraphenyldibenzoperiflanthene (DBP) Films on Ag(111) in the Monolayer Regime.

    Science.gov (United States)

    Kirchhuebel, Tino; Gruenewald, Marco; Sojka, Falko; Kera, Satoshi; Bussolotti, Fabio; Ueba, Takahiro; Ueno, Nobuo; Rouillé, Gaël; Forker, Roman; Fritz, Torsten

    2016-03-01

    Tetraphenyldibenzoperiflanthene (DBP) is a promising candidate as a component of highly efficient organic photovoltaic cells and organic light-emitting diodes. The structural properties of thin films of this particular lander-type molecule on Ag(111) were investigated by complementary techniques. Highly ordered structures were obtained, and their mutual alignment was characterized by means of low-energy electron diffraction (LEED). Scanning tunneling microscopy (STM) images reveal two slightly different arrangements within the first monolayer (ML), both describable as specific herringbone patterns with two molecules per unit cell whose dibenzoperiflanthene framework is parallel to the surface. In contrast, single DBP molecules in the second ML were imaged with much higher intramolecular resolution, resembling the shape of the frontier orbitals in the gas phase as calculated by means of density functional theory (DFT). Further deposition leads to the growth of highly ordered bilayer islands on top of the first ML with identical unit cell dimensions and orientation but slightly inclined molecules. This suggests that the first ML acts as a template for the epitaxial growth of further layers. Simultaneously, a significant number of second-layer molecules mainly located at step edges or scattered over narrow terraces do not form highly ordered aggregates. PMID:26844381

  5. Interface dipoles of organic molecules on Ag(111) in hybrid density-functional theory

    International Nuclear Information System (INIS)

    We investigate the molecular acceptors 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) and 4,5,9,10-pyrenetetraone (PYTON) on Ag(111) using density-functional theory (DFT). For two groups of the Heyd–Scuseria–Ernzerhof (HSE(α, ω)) family of exchange-correlation functionals (ω = 0 and 0.2 Å) we study the isolated components as well as the combined systems as a function of the amount of exact-exchange (α). We find that hybrid functionals favour electron transfer to the adsorbate. Comparing with experimental work function data, for α ≈ 0.25 we report a notable but small improvement over (semi) local functionals for the interface dipole. Although Kohn–Sham eigenvalues are only approximate representations of ionization energies, incidentally, at this value also the density of states agrees well with the photoelectron spectra. However, increasing α to values for which the energy of the lowest unoccupied molecular orbital matches the experimental electron affinity in the gas phase worsens both the interface dipole and the density of states. Our results imply that semi-local DFT calculations may often be adequate for conjugated organic molecules on metal surfaces and that the much more computationally demanding hybrid functionals yield only small improvements. (paper)

  6. Thermal and Electronic Fluctuations of Flexible Adsorbed Molecules: Azobenzene on Ag(111)

    Science.gov (United States)

    Maurer, Reinhard J.; Liu, Wei; Poltavsky, Igor; Stecher, Thomas; Oberhofer, Harald; Reuter, Karsten; Tkatchenko, Alexandre

    2016-04-01

    We investigate the thermal and electronic collective fluctuations that contribute to the finite-temperature adsorption properties of flexible adsorbates on surfaces on the example of the molecular switch azobenzene C12 H10 N2 on the Ag(111) surface. Using first-principles molecular dynamics simulations, we obtain the free energy of adsorption that accurately accounts for entropic contributions, whereas the inclusion of many-body dispersion interactions accounts for the electronic correlations that govern the adsorbate binding. We find the adsorbate properties to be strongly entropy driven, as can be judged by a kinetic molecular desorption prefactor of 1024 s-1 that largely exceeds previously reported estimates. We relate this effect to sizable fluctuations across structural and electronic observables. A comparison of our calculations to temperature-programed desorption measurements demonstrates that finite-temperature effects play a dominant role for flexible molecules in contact with polarizable surfaces, and that recently developed first-principles methods offer an optimal tool to reveal novel collective behavior in such complex systems.

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

    International Nuclear Information System (INIS)

    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. (paper)

  8. 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. PMID:22223550

  9. Conductance of Ag atoms and clusters on Ag(111): Spectroscopic and time-resolved data

    Energy Technology Data Exchange (ETDEWEB)

    Sperl, A.; Kroeger, J.; Berndt, R. [Institut fuer Experimentelle und Angewandte Physik, Christian-Albrechts-Universitaet zu Kiel (Germany)

    2010-05-15

    The evolution of the electronic structure of linear atomic Ag chains on Ag(111) has been explored atom by atom using low-temperature scanning tunnelling microscopy and spectroscopy. Electronic states confined to the linear chains are well described within a particle-in-a-box model. The evolution of an unoccupied Ag monomer resonance during the synthesis of an Ag dimer reveals that the Ag-Ag interaction is predominantly direct owing to the large spatial extension of p wave functions of the adsorbed atoms. The hopping dynamics of a single Ag atom adsorbed on Ag(111) have been monitored by time-resolved two-level conductance fluctuations of the tunnel junctions. Effective temperatures of the junction and diffusion barrier heights in the presence of the tip were extracted from a voltage-dependent analysis of the fluctuation rate. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  10. A three-dimensional self-learning kinetic Monte Carlo model: application to Ag(111)

    International Nuclear Information System (INIS)

    The reliability of kinetic Monte Carlo (KMC) simulations depends on accurate transition rates. The self-learning KMC method (Trushin et al 2005 Phys. Rev. B 72 115401) combines the accuracy of rates calculated from a realistic potential with the efficiency of a rate catalog, using a pattern recognition scheme. This work expands the original two-dimensional method to three dimensions. The concomitant huge increase in the number of rate calculations on the fly needed can be avoided by setting up an initial database, containing exact activation energies calculated for processes gathered from a simpler KMC model. To provide two representative examples, the model is applied to the diffusion of Ag monolayer islands on Ag(111), and the homoepitaxial growth of Ag on Ag(111) at low temperatures.

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

    OpenAIRE

    Yang, Aram

    2008-01-01

    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 ...

  12. Untersuchung der Elektronendynamik an der PTCDA/Ag(111)-Grenzfläche

    OpenAIRE

    Schwalb, Christian

    2009-01-01

    Im Rahmen dieser Arbeit wird die Elektronendynamik an der PTCDA/Ag(111)-Grenzfläche mit Hilfe von zeit- und winkelaufgelöster Zweiphotonen-Photoemission (2PPE) sowie zeitaufgelöster Photolumineszenz-Spektroskopie (PL) untersucht. Der erste Teil der Arbeit widmet sich der Charakterisierung eines unbesetzten elektronischen Zustands, der sich durch die Adsorption der PTCDA-Moleküle 0.6 eV oberhalb der Fermienergie ausbildet, während ...

  13. Long-range surface faceting induced by chemisorption of PTCDA on stepped Ag(111) surfaces

    Science.gov (United States)

    Schmitt, Stefan; Schöll, Achim; Umbach, Eberhard

    2016-01-01

    The organic molecule PTCDA preferentially adsorbs on steps of vicinal Ag(111) surfaces and bunches them to well defined facet planes. These depend on coverage and annealing temperature and are independent of the nominal step direction and angle of inclination of the unreconstructed initial surface. We study the development of the facets and present a map of all 16 types of facets in a stereographic triangle of 35° off the [111]-direction. The faceting mechanism is interpreted as orientational phase separation originating from different bonding strengths of PTCDA on various facets. The faceting drives the system to the minimum of its surface free energy.

  14. Growth and structure of the organic molecule PTCDA on Ag(111)

    OpenAIRE

    Krause, Bärbel

    2002-01-01

    Thin 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) films with the average thickness d between 50 and 200 Å, and the deposition rate F between 1 and 10 Å/min, have been deposited by molecular beam epitaxy on Ag(111). The films have been studied by atomic force microscopy and X-ray diffraction. It has been found that their structural and morphological properties vary significantly with the growth conditions. A transition from relatively smooth films to island growth on top of 2 wetting...

  15. Manipulation resolves non-trivial structure of corrole monolayer on Ag(111).

    Science.gov (United States)

    Tebi, Stefano; Aldahhak, Hazem; Serrano, Giulia; Schöfberger, Wolfgang; Rauls, Eva; Schmidt, Wolf Gero; Koch, Reinhold; Müllegger, Stefan

    2016-01-15

    Non-trivial arrangement of molecules within a molecular network complicates structure determination due to interdigitation, partial overlap, or stacking. We demonstrate that combined imaging and lateral manipulation with a scanning tunneling microscope resolves the intricate structure of a molecular network in two-dimensions in a straightforward manner. The network, formed by a monolayer of 5,10,15-tris(pentafluorophenyl)-corrole molecules on Ag(111), is manipulated for the first time with single-molecule precision. Our results reveal a shingle-like packing of partially overlapping corrole molecules. Density functional theory calculations support our findings. PMID:26629708

  16. Atomic structure of Ag(111) saturated with chlorine: Formation of Ag3Cl7 clusters

    Science.gov (United States)

    Andryushechkin, B. V.; Cherkez, V. V.; Gladchenko, E. V.; Zhidomirov, G. M.; Kierren, B.; Fagot-Revurat, Y.; Malterre, D.; Eltsov, K. N.

    2011-08-01

    The structure of saturated chlorine layer on Ag(111) has been studied with low temperature scanning tunneling microscopy and density functional theory. For the first time atomic-resolution STM images of saturated chlorine coverage have been obtained. STM images demonstrate coexistence of the domain with (3 × 3)-like reconstruction and numerous bright objects identified as Ag3Cl7 clusters. According to our model supported by DFT calculations, clusters are formed on the boundaries between the adjacent (3×3) antiphase domains. These boundaries have a characteristic triangular shape and are formed by six chlorine atoms chemisorbed on the triangular silver island with local periodicity (1 × 1).

  17. Site-specific dissociation dynamics of H2/D2 on Ag(111) and Co(0001) and the validity of the site-averaging model

    International Nuclear Information System (INIS)

    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

  18. Benzene derivatives adsorbed to the Ag(111) surface: Binding sites and electronic structure

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Daniel P.; Tymińska, Nina; Zurek, Eva, E-mail: ezurek@buffalo.edu [Department of Chemistry, State University of New York at Buffalo, Buffalo, New York 14260-3000 (United States); Simpson, Scott [Department of Chemistry, State University of New York at Buffalo, Buffalo, New York 14260-3000 (United States); School of Science, Penn State Erie, The Behrend College, 4205 College Drive, Erie, Pennsylvania 16563 (United States)

    2015-03-14

    Dispersion corrected Density Functional Theory calculations were employed to study the adsorption of benzenes derivatized with functional groups encompassing a large region of the activated/deactivated spectrum to the Ag(111) surface. Benzenes substituted with weak activating or deactivating groups, such as methyl and fluoro, do not have a strong preference for adsorbing to a particular site on the substrate, with the corrugations in the potential energy surface being similar to those of benzene. Strong activating (N(CH{sub 3}){sub 2}) and deactivating (NO{sub 2}) groups, on the other hand, possess a distinct site preference. The nitrogen in the former prefers to lie above a silver atom (top site), but in the latter a hollow hexagonal-closed-packed (H{sub hcp}) site of the Ag(111) surface is favored instead. Benzenes derivatized with classic activating groups donate electron density from their highest occupied molecular orbital to the surface, and those functionalized with deactivating groups withdraw electron density from the surface into orbitals that are unoccupied in the gas phase. For benzenes functionalized with two substituents, the groups that are strongly activating or deactivating control the site preference and the other groups assume sites that are, to a large degree, dictated by their positions on the benzene ring. The relative stabilities of the ortho, meta, and para positional isomers of disubstituted benzenes can, in some cases, be modified by adsorption to the surface.

  19. Benzene derivatives adsorbed to the Ag(111) surface: Binding sites and electronic structure

    International Nuclear Information System (INIS)

    Dispersion corrected Density Functional Theory calculations were employed to study the adsorption of benzenes derivatized with functional groups encompassing a large region of the activated/deactivated spectrum to the Ag(111) surface. Benzenes substituted with weak activating or deactivating groups, such as methyl and fluoro, do not have a strong preference for adsorbing to a particular site on the substrate, with the corrugations in the potential energy surface being similar to those of benzene. Strong activating (N(CH3)2) and deactivating (NO2) groups, on the other hand, possess a distinct site preference. The nitrogen in the former prefers to lie above a silver atom (top site), but in the latter a hollow hexagonal-closed-packed (Hhcp) site of the Ag(111) surface is favored instead. Benzenes derivatized with classic activating groups donate electron density from their highest occupied molecular orbital to the surface, and those functionalized with deactivating groups withdraw electron density from the surface into orbitals that are unoccupied in the gas phase. For benzenes functionalized with two substituents, the groups that are strongly activating or deactivating control the site preference and the other groups assume sites that are, to a large degree, dictated by their positions on the benzene ring. The relative stabilities of the ortho, meta, and para positional isomers of disubstituted benzenes can, in some cases, be modified by adsorption to the surface

  20. Lateral interaction and structures in Cl adlayers on the Ag(111) surface

    International Nuclear Information System (INIS)

    Graphical abstract: The sharpness of the order-disorder transition for the (√3 x √3)R30o structure depends on the rate of cooling, as is illustrated by two plots obtained with Monte Carlo simulation for the 2 K (solid line) and 5 K (dash line) temperature steps. Display Omitted Highlights: →Energies of lateral interaction for Cl on Ag(111) are determined from DFT. → Structures and order-disorder transitions are studied via Monte Carlo simulations. → The disordering of the (√3 x √3)R30o structure is abrupt. → Antiphase domains of the honeycomb structure cancel the (2 x 2) LEED pattern. - Abstract: The lateral interaction and formation of ordered structures in Cl submonolayers adsorbed on Ag(111) surface at low coverages (up to 0.5 ML), when the diffusion of Cl into the bulk is negligible, have been studied by Monte Carlo method using parameters of the lateral interaction estimated from DFT calculations. The transition temperature and sharpness of the order-disorder transition for the (√3 x √3)R30o structure, derived from the Monte Carlo simulation, are in good agreement with available experimental data. It has been demonstrated that a restricted mobility of adsorbed Cl atoms can result, for a relatively high rate of the cooling of the layer, in the formation of domain structures. For imperfect domain structures, the model LEED patterns show a characteristic splitting of reflections due to phase shifts for electrons scattered at different domains.

  1. Band structure of hydrogenated silicene on Ag(111): Evidence for half-silicane

    Science.gov (United States)

    Wang, W.; Olovsson, W.; Uhrberg, R. I. G.

    2016-02-01

    In the case of graphene, hydrogenation removes the conductivity due to the bands forming the Dirac cone by opening up a band gap. This type of chemical functionalization is of the utmost importance for electronic applications. As predicted by theoretical studies, a similar change in the band structure is expected for silicene, the closest analog to graphene. We here report a study of the atomic and electronic structures of hydrogenated silicene with hydrogen on one side, the so-called half-silicane. The ("2 √{3 }×2 √{3 } ") phase of silicene on Ag(111) was used in this Rapid Communication since it can be formed homogeneously across the entire surface of the Ag substrate. Low-energy electron diffraction and scanning tunneling microscopy data clearly show that hydrogenation changes the structure of silicene on Ag(111) resulting in a (1 × 1) periodicity with respect to the silicene lattice. The hydrogenated silicene also exhibits a quasiregular (2 √{3 }×2 √{3 } )-like arrangement of vacancies. Angle-resolved photoelectron spectroscopy revealed two dispersive bands which can be unambiguously assigned to half-silicane. The common top of these bands is located at ˜0.9 eV below the Fermi level. We find that the experimental bands are closely reproduced by the theoretical band structure of free-standing silicene with H adsorbed on the upper hexagonal sublattice.

  2. Dynamics of electron transport at the PTCDA/Ag(111)-interface studied with time-resolved 2PPE

    Energy Technology Data Exchange (ETDEWEB)

    Schwalb, Christian; Marks, Manuel B.; Hoefer, Ulrich [Fachbereich Physik, Zentrum fuer Materialwissenschaften, Philipps-Universitaet Marburg, D-35032 Marburg (Germany); Sachs, Soenke; Schoell, Achim [Universitaet Wuerzburg, Experimentelle Physik II, D-97074 Wuerzburg (Germany); Umbach, Eberhard [Universitaet Wuerzburg, Experimentelle Physik II, D-97074 Wuerzburg (Germany); Forschungszentrum Karlsruhe, D-76021 Karlsruhe (Germany)

    2009-07-01

    Time-resolved two-photon photoemission (2PPE) is able to provide very detailed information about the electronic structure and the dynamics of electron transfer processes of well-ordered interfaces between organic semiconductors and metals. As a model system we have investigated thin epitaxial PTCDA films on Ag(111). A dispersing unoccupied state with an effective electron mass of 0.39 m{sub e} at the anti {gamma}-point emerges 0.6 eV above the metallic Fermi level E{sub F}. Its short lifetime of 55 fs is a clear indication that this state has a strong overlap with the metal and essentially originates from an upshift of the Shockley surface state of the Ag substrate. In order to investigate the role of the interface state for charge carrier injection, we populate the LUMO of PTCDA in films of varying thickness and simultaneously record fluorescence and photoemission spectra. A long lived component observed in the 2PPE signal close to E{sub F} clearly correlates with film thickness and fluorescence lifetime.

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

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhi-Long; Wang, Mei-Xiao; Liu, Canhua, E-mail: canhualiu@sjtu.edu.cn, E-mail: depadova@ism.cnr.it, E-mail: guy.lelay@univ-amu.fr; Jia, Jin-Feng [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093 (China); Vogt, Patrick [Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstraße 36, 10623 Berlin (Germany); Quaresima, Claudio; Ottaviani, Carlo; De Padova, Paola, E-mail: canhualiu@sjtu.edu.cn, E-mail: depadova@ism.cnr.it, E-mail: guy.lelay@univ-amu.fr [CNR-ISM, via Fosso del Cavaliere, Rome 00133 (Italy); Olivieri, Bruno [ISAC-CNR, via Fosso del Cavaliere 100, Rome (Italy); Lay, Guy Le, E-mail: canhualiu@sjtu.edu.cn, E-mail: depadova@ism.cnr.it, E-mail: guy.lelay@univ-amu.fr [Aix-Marseille Université, CNRS, PIIM UMR 7345, 13397, Marseille (France)

    2014-09-01

    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)

  4. 3D-force-spectroscopy and -dissipation data of an organic-inorganic interface: PTCDA on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Braun, Daniel-Alexander; Langewisch, Gernot; Fuchs, Harald; Schirmeisen, Andre [CeNTech (Center for Nanotechnology) and Institute of Physics, University of Muenster (Germany)

    2009-07-01

    Organic semiconductors have attracted intensive research over the last years. Especially the adsorption of {pi}-conjugated organic molecules on metal substrates in view of potential applications in organic and molecular electronics gained a lot of interest. One of the most studied molecules is 3,4,9,10-perylenetetracarboxylic-dianhydride (PTCDA) and it has been investigated on a wide range of substrates. Noncontact atomic force microscopy (ncAFM) experiments with PTCDA adsorbed on Cu(111) revealed, that the intramolecular contrast of PTCDA-molecules depends strongly on the local adsorption environment. Here we present experimental ncAFM results of 3-dimensional force and dissipation spectroscopy experiments of PTCDA adsorbed on Ag(111) with submolecular resolution. The dissipation is understood as a hysteresis of forces between approach and retraction of the tip and is caused by bistabilities in the potential energy surface of the tip-sample system. Therefore the dissipation signal can reveal information about the mechanical properties of individual molecules.

  5. Electronic structure at the perylene-tetracarboxylic acid dianhydride/Ag(111) interface studied with two-photon photoelectron spectroscopy.

    Science.gov (United States)

    Sachs, Sönke; Schwalb, Christian H; Marks, Manuel; Schöll, Achim; Reinert, Friedrich; Umbach, Eberhard; Höfer, Ulrich

    2009-10-14

    The electronic structure of the prototype metal/organic contact 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) on a Ag(111)-surface has been investigated using time- and angle-resolved two-photon photoelectron spectroscopy (2PPE). Our analysis addresses particularly the nature of the interface state (IS) emerging at the interface due to the substrate-adsorbate interaction [C. H. Schwalb, S. Sachs, M. Marks et al., Phys. Rev. Lett. 101, 146801 (2008)]. Its free-electron-like dispersion and a possible backfolding at the surface Brillouin zone boundaries are discussed. Time-resolved pump-probe experiments reveal the inelastic electron lifetime along the dispersion parabola and show its decrease for increasing parallel momentum. The temperature dependence of the peak linewidth indicates a coupling of the IS to molecular vibrations. Moreover, additional aspects are addressed, such as the determination of the electron attenuation length of photoelectrons for low kinetic energy originating from the IS and the work function change of the sample upon PTCDA adsorption with very high energy resolution. PMID:19831458

  6. 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

  7. Vermessung von Dispersion und Elektronendynamik der NTCDA/Ag(111) Grenzflächenzustände mittels 2-Photonen-Photoemission

    OpenAIRE

    Schmidt, Benjamin

    2010-01-01

    Vermessung der Bildpotentialzustände sowie des Interfacezustands an der NTCDA/Ag(111)-Grenzfläche im Vergleich zum wohlbekannten PTCDA/Ag(111)-Modellsystem. Untersucht werden sowohl die Dispersion als auch die Elektronendynamik der Zustände.

  8. Formation of surface oxides and Ag2O thin films with atomic oxygen on Ag(111)

    Science.gov (United States)

    Derouin, Jonathan; Farber, Rachael G.; Heslop, Stacy L.; Killelea, Daniel R.

    2015-11-01

    The nature of the oxygen species adsorbed to silver surfaces is a key component of the heterogeneously catalyzed epoxidation of ethylene and partial oxidation of methanol over silver catalysts. We report the formation of two different silver-oxygen species depending on the flux and energy of incident gas-phase oxygen atoms on an Ag(111) surface. A combination of surface science techniques was used to characterize the oxidized surfaces. Atomic oxygen was generated with an Ir filament; lower temperatures created surface oxides previously reported. When O was deposited with a higher filament temperature, the surface became highly corrugated, little subsurface oxygen was observed, and thin layers of Ag2O were likely formed. These results show that the energy and flux of oxygen are important parameters in the chemical identity and abundance of oxygen on silver surfaces and suggest that formation of the Ag2O thin film hinders formation of subsurface oxygen.

  9. Relaxation of surface stress induced by an organic adsorbate: PTCDA on vicinal Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Pollinger, Florian; Vrdoljak, Pavo; Fertig, Dominik; Schmitt, Stefan; Kumpf, Christian; Schoell, Achim; Umbach, Eberhard [Universitaet Wuerzburg, Experimentelle Physik II, Am Hubland, 97074 Wuerzburg (Germany); Tian, Zhen; Sander, Dirk; Kirschner, Juergen [Max-Planck-Institut fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany)

    2007-07-01

    Self-organization of metallic surfaces on large scales can be induced by the adsorption of organic molecules and has been observed in several experiments. One example is the growth of 3,4,9,10-perylenetetracarboxylic-acid dianhydride (PTCDA) on stepped (8.5 -vicinal) Ag(111) surfaces. At elevated temperatures, the adsorbate molecules lead to a bunching of substrate steps, which agglomerate to facets of critical sizes. The facets arrange in a coverage-dependent grating-like pattern on a mesoscopic length scale. The resulting order requires a long-range interaction which is mediated by the substrate. It can be explained by a change of surface stress induced by the adsorbate layer. Experimentally, such a change is directly accessible by an optical cantilever bending technique. We monitored the bending of a faceting thin Ag(10 8 7) crystal with this method in order to quantify the occurring relaxation of surface stress.

  10. Light emission from Ag(111) driven by inelastic tunneling in the field emission regime.

    Science.gov (United States)

    Martínez-Blanco, Jesús; Fölsch, Stefan

    2015-07-01

    We study the light emission from a Ag(111) surface when the bias voltage on a scanning tunneling microscope (STM) junction is ramped into the field emission regime. Above the vacuum level, scanning tunneling spectroscopy (STS) shows a series of well defined resonances associated with the image states of the surface, which are Stark shifted due to the electric field provided by the STM tip. We present photon-energy resolved measurements that unambiguously show that the mechanism for light emission is the radiative decay of surface localized plasmons excited by the electrons that tunnel inelastically into the Stark shifted image states. Our work illustrates the effect of the tip radius both in the STS spectrum and the light emission maps by repeating the experiment with different tips. PMID:26045477

  11. Dynamics of Spatially Confined Bisphenol A Trimers in a Unimolecular Network on Ag(111).

    Science.gov (United States)

    Lloyd, Julian A; Papageorgiou, Anthoula C; Fischer, Sybille; Oh, Seung Cheol; Saǧlam, Özge; Diller, Katharina; Duncan, David A; Allegretti, Francesco; Klappenberger, Florian; Stöhr, Martin; Maurer, Reinhard J; Reuter, Karsten; Reichert, Joachim; Barth, Johannes V

    2016-03-01

    Bisphenol A (BPA) aggregates on Ag(111) shows a polymorphism between two supramolecular motifs leading to formation of distinct networks depending on thermal energy. With rising temperature a dimeric pairing scheme reversibly converts into a trimeric motif, which forms a hexagonal superstructure with complex dynamic characteristics. The trimeric arrangements notably organize spontaneously into a self-assembled one-component array with supramolecular BPA rotors embedded in a two-dimensional stator sublattice. By varying the temperature, the speed of the rotors can be controlled as monitored by direct visualization. A combination of scanning tunneling microscopy and dispersion-corrected density-functional tight-binding (DFTB-vdW(surf)) based molecular modeling reveals the exact atomistic position of each molecule within the assembly as well as the driving force for the formation of the supramolecular rotors. PMID:26849384

  12. Structure of chlorine on Ag(111): Evidence of the (3×3) reconstruction

    Science.gov (United States)

    Andryushechkin, B. V.; Cherkez, V. V.; Gladchenko, E. V.; Zhidomirov, G. M.; Kierren, B.; Fagot-Revurat, Y.; Malterre, D.; Eltsov, K. N.

    2010-05-01

    The structure of the chlorine induced reconstruction of Ag(111) has been studied by a combination of low-temperature scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and density-functional theory (DFT). We demonstrate that previously observed mysterious LEED pattern arises as a result of diffraction from a system of small (15-30Å) triangular antiphase domains with a new (3×3) superstructure. In our model supported by DFT calculations, within a (3×3) unit cell the upper silver layer reconstructs forming a couple of three-atom triangles placed in fcc and hcp sites of the substrate. Chlorine atoms occupy fourfold hollow sites between these triangles. The corner holes, which look like depressions in the STM images, are also occupied by chlorine atoms.

  13. Slow positron studies on single crystals of Ag(100), Ag(111) and Cu(111)

    International Nuclear Information System (INIS)

    Monoenergetic positrons were employed to examine positronium formation as a function of sample temperature (300 to 1200 K) and incident energy (0 to 5 keV) on Ag(100), Ag(111) and Cu(111) surfaces with submonolayer contamination. In these metals at the higher temperatures, positronium formation becomes the dominant process. A one-dimensional diffusion model is fit to the data as a function of incident energy. Th positronium fraction is found to be an activated process and is identified as detrapping from a surface state and an estimate of the depth of this trap is extracted. The diffusion length is found to be temperature independent before the onset of vacancy trapping. At the higher temperatures vacancy trapping is observed by the decrease in the positron diffusion length at the higher incident voltages. A vacancy formation energy is extracted from the data and is generally lower than the accepted bulk values. 18 references

  14. Diffusion of Cu adatoms and dimers on Cu(111) and Ag(111) surfaces

    Science.gov (United States)

    Mińkowski, Marcin; Załuska-Kotur, Magdalena A.

    2015-12-01

    Diffusion of Cu adatoms and dimers on Cu(111) and Ag(111) surfaces is analyzed based on ab initio surface potentials. Single adatom diffusion is compared with dimer diffusion on both surfaces. Surface geometry makes the adatoms jump alternately between two states in the same way in both systems, whereas dimers undergo more complex diffusion process that combines translational and rotational motion. Small difference in the surface lattice constant between Cu and Ag crystals results in a completely different energy landscape for dimer jumps. As an effect the character of diffusion process changes. Homogeneous Cu dimer diffusion is more difficult and dimers rather rotate within single surface cell, whereas diffusion over Ag surface is faster and happens more smoothly. The temperature dependence of diffusion coefficient and its parameters: energy barrier and prefactor is calculated and compared for both surfaces.

  15. 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.

  16. Theoretical study of PTCDA adsorbed on the coinage metal surfaces, Ag(111), Au(111) and Cu(111)

    Energy Technology Data Exchange (ETDEWEB)

    Romaner, L; Nabok, D; Puschnig, P; Ambrosch-Draxl, C [Chair of Atomistic Modelling and Design of Materials, University of Leoben, Franz-Josef-Strasse 18, A-8700 Leoben (Austria); Zojer, E [Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz (Austria)], E-mail: lorenz.romaner@unileoben.ac.at

    2009-05-15

    A thorough understanding of the adsorption of molecules on metallic surfaces is a crucial prerequisite for the development and improvement of functionalized materials. A prominent representative within the class of {pi}-conjugated molecules is 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) which, adsorbed on the Ag(111), Au(111) or Cu(111) surfaces, shows characteristic trends for work-function modification, alignment of molecular levels with the substrate Fermi energy and binding distances. We carried out density functional theory (DFT) calculations to investigate to what extent these trends can be rationalized on a theoretical basis. We used different density functionals (DF) including a fully non-local van der Waals (vdW) DF capable of describing dispersion interactions. We show that, rather independent of the DF, the calculations yield level alignments and work-function modifications consistent with ultra-violet photoelectron spectroscopy when the monolayer is placed onto the surfaces at the experimental distances (as determined from x-ray standing wave experiments). The lowest unoccupied molecular orbital is occupied on the Ag and Cu surfaces, whereas it remains unoccupied on the Au surface. Simultaneously, the work function increases for Ag but decreases for Cu and Au. Adsorption distances and energies, on the other hand, depend very sensitively on the choice of the DF. While calculations in the local density approximation bind the monolayer consistently with the experimental trends, the generalized gradient approximation in several flavors fails to reproduce realistic distances and energies. Calculations employing the vdW-DF reveal that substantial bonding contributions arise from dispersive interactions. They yield reasonable binding energies but larger binding distances than the experiments.

  17. Theoretical study of PTCDA adsorbed on the coinage metal surfaces, Ag(111), Au(111) and Cu(111)

    International Nuclear Information System (INIS)

    A thorough understanding of the adsorption of molecules on metallic surfaces is a crucial prerequisite for the development and improvement of functionalized materials. A prominent representative within the class of π-conjugated molecules is 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) which, adsorbed on the Ag(111), Au(111) or Cu(111) surfaces, shows characteristic trends for work-function modification, alignment of molecular levels with the substrate Fermi energy and binding distances. We carried out density functional theory (DFT) calculations to investigate to what extent these trends can be rationalized on a theoretical basis. We used different density functionals (DF) including a fully non-local van der Waals (vdW) DF capable of describing dispersion interactions. We show that, rather independent of the DF, the calculations yield level alignments and work-function modifications consistent with ultra-violet photoelectron spectroscopy when the monolayer is placed onto the surfaces at the experimental distances (as determined from x-ray standing wave experiments). The lowest unoccupied molecular orbital is occupied on the Ag and Cu surfaces, whereas it remains unoccupied on the Au surface. Simultaneously, the work function increases for Ag but decreases for Cu and Au. Adsorption distances and energies, on the other hand, depend very sensitively on the choice of the DF. While calculations in the local density approximation bind the monolayer consistently with the experimental trends, the generalized gradient approximation in several flavors fails to reproduce realistic distances and energies. Calculations employing the vdW-DF reveal that substantial bonding contributions arise from dispersive interactions. They yield reasonable binding energies but larger binding distances than the experiments.

  18. Ab initio study of origin and properties of a metal-organic interface state of the PTCDA/Ag(111) system

    OpenAIRE

    Zaitsev, N. L.; Nechaev, I. A.; P. M. Echenique; Chulkov, E. V.

    2010-01-01

    We present a detailed study of a monolayer film of 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) on Ag(111) (the PTCDA/Ag(111) system). The study is done within density functional theory with the use of the periodic slab model. The slab is chosen to contain a PTCDA monolayer film on a silver thin film of different thicknesses (6, 9, and 12 layers) with the (111) orientation. We show that one of two surface states of the pure Ag(111) films transforms into an unoccupied interface s...

  19. Nature of free-electron-like states in PTCDA molecules adsorbed on an Ag(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Persson, Mats; Dyer, Matthew [Surface Science Research Centre, University of Liverpool, L69 3BX Liverpool (United Kingdom)

    2009-07-01

    Advances in molecular assembly experiments on metal surfaces and potential applications arising from them call for a better understanding of the electronic structure at the interface of metals and organic systems. There is a high interest in delocalized electronic states, because of their potential use in molecular and opto-electronics applications. Recently, unoccupied, free-electron-like states arising in mono layers of 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) molecules adsorbed on an Ag(111) surface at energies close to the Fermi energy have been observed by scanning tunneling and photoemission spectroscopies. So as to reveal the nature of these delocalized states we have carried out a density functional study of the electronic structure and local density of states of these systems. We show that the observed free-electron state originates from a Shockley surface state (SS) at the zone centre of the bare surface. The SS is shifted up by the interaction with the organic overlayer.

  20. Complex Stoichiometry reordering of PTCDA on Ag(111) upon K Intercalation

    Science.gov (United States)

    Brivio, G. P.; Baby, A.; Zwick, C.; Gruenewald, M.; Forker, R.; Fritz, T.; Fratesi, G.; Hofmann, O. T.; Zojer, E.

    Alkali metal atoms are a simple yet efficient n-type dopant of organic semiconductors. However, the molecular crystal structures need be controlled and well understood in order to optimize the electronic properties (charge carrier density and mobility) of the target material. Here, we report that potassium intercalation into PTCDA monolayer domains on a Ag(111) substrate induces distinct stoichiometry-dependent structural reordering processes, resulting in highly ordered and large KxPTCDA domains. The emerging structures are analyzed by low temperature scanning tunneling microscopy (STM), scanning tunneling hydrogen microscopy (STHM), and low-energy electron diffraction (LEED) as a function of the stoichiometry and by density functional theory (DFT) calculations. Large stable monolayer domains are found for x=2,4. The epitaxy types for all intercalated stages are determined as point-on-line. The K atoms adsorb in the vicinity of the oxygen atoms of the PTCDA molecules, and their positions are determined with sub-Angstrom precision. This is a crucial prerequisite for the prospective assessment of the electronic properties of such composite films, as they depend on the mutual alignment between donor atoms and acceptor molecules.

  1. Quasi-freestanding epitaxial silicene on Ag(111) by oxygen intercalation.

    Science.gov (United States)

    Du, Yi; Zhuang, Jincheng; Wang, Jiaou; Li, Zhi; Liu, Hongsheng; Zhao, Jijun; Xu, Xun; Feng, Haifeng; Chen, Lan; Wu, Kehui; Wang, Xiaolin; Dou, Shi Xue

    2016-07-01

    Silicene is a monolayer allotrope of silicon atoms arranged in a honeycomb structure with massless Dirac fermion characteristics similar to graphene. It merits development of silicon-based multifunctional nanoelectronic and spintronic devices operated at room temperature because of strong spin-orbit coupling. Nevertheless, until now, silicene could only be epitaxially grown on conductive substrates. The strong silicene-substrate interaction may depress its superior electronic properties. We report a quasi-freestanding silicene layer that has been successfully obtained through oxidization of bilayer silicene on the Ag(111) surface. The oxygen atoms intercalate into the underlayer of silicene, resulting in isolation of the top layer of silicene from the substrate. In consequence, the top layer of silicene exhibits the signature of a 1 × 1 honeycomb lattice and hosts massless Dirac fermions because of much less interaction with the substrate. Furthermore, the oxidized silicon buffer layer is expected to serve as an ideal dielectric layer for electric gating in electronic devices. These findings are relevant for the future design and application of silicene-based nanoelectronic and spintronic devices. PMID:27532041

  2. High resolution photoelectron spectroscopy at the SnPc/Ag(111) interface

    Energy Technology Data Exchange (ETDEWEB)

    Scheuermann, C.; Haeming, M.; Kroeger, I.; Stadler, C.; Kumpf, C.; Schoell, A.; Reinert, F.; Umbach, E. [Universitaet Wuerzburg, Experimentelle Physik II, 97074 Wuerzburg (Germany)

    2008-07-01

    Phthalocyanines are interesting for applications in organic devices due to the potential of tailoring their properties by introducing different metal ligands into the heterocycle. Some derivates offer the potential of tuning the work function of metal contacts due to an intrinsic dipole moment. We present a high resolution photoelectron spectroscopy study on SnPc submonolayers on Ag(111). Based on a structural analysis, which shows the existence of different adsorption phases with different orientation of the molecular dipoles depending on temperature and coverage, the PES data indicate a significant effect on the surface work function. The valence and core spectra allow identifying a covalent interaction at the interface with the appearance of a new state at EF. Moreover, the data provide evidence for a systematic weakening of the interfacial interaction with increasing coverage. This is accompanied by a constriction of the substrate-adsorbate charge transfer, which becomes evident from an analysis of the core level line shapes. As a consequence, a comprehensive description of the electronic structure in the contact regime, of the resulting interface dipole, and of work function effects needs to account not only for structural properties such as the intrinsic molecular geometry, but also for intermolecular- and interfacial interactions which may involve significant charge transfer.

  3. Structural and electronic properties of thin organic heterointerfaces SnPc/PTCDA/Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Haeming, Mark; Sauer, Christoph; Greif, Michael; Schoell, Achim [Universitaet Wuerzburg, Experimentelle Physik VII, Wuerzburg (Germany); Reinert, Friedrich [Universitaet Wuerzburg, Experimentelle Physik VII, Wuerzburg (Germany); KIT, Gemeinschaftslabor fuer Nanoanalytik, Karlsruhe (Germany)

    2011-07-01

    Knowledge about the structural and electronic properties of organic heterointerfaces is of vital importance for electronic devices based on organic semiconductors. Yet information about these systems is still scarce due to difficulties in preparing well defined interfaces. With tin-phtalocyanine (SnPc) deposited on a Ag(111) surface precovered by perylene-tetracarboxylic acid dianhydride (PTCDA) we present a well suited model system to gain insight into such heterointerfaces. Photoelectron spectroscopy (XPS and UPS) as well as near edge X-ray absorption fine structure (NEXAFS) studies are applied in order to gain both structural and electronic information. Distinct features in core-level and valence spectra allow us to unambiguously distinguish between both molecules. We show clear evidence that SnPc forms a flat lying wetting layer on top of PTCDA with a mainly physisorptive character. Moreover a rigid level shift of all spectroscopic SnPc features with respect to the homomolecular SnPc films is observed, similar to what is known for Schottky contacts, which corresponds to a change in work function. We demonstrate that the built-in electric field at the interface can be explained by the formation of an interface dipole, which extends over several adsorbate monolayers.

  4. Butanethiol adsorption and dissociation on Ag (111): A periodic DFT study

    Science.gov (United States)

    Li, Aixiao; Piquemal, Jean-Philip; Richardi, Johannes; Calatayud, Monica

    2016-04-01

    The molecular and dissociative adsorption of butanethiol (C4H9SH) on regular Ag (111) surfaces has been studied by means of periodic ab initio density functional techniques. In molecular form, butanethiol is bound to the surface only by weak polarization-induced forces with the C-S axis tilted by 38° relative to the normal surface. The S atom occupies a position between a hollow fcc and a bridge site. In the dissociative adsorption process, the S-H bond breaks leading to butanethiolate. The S atom of the thiolate also occupies a threefold position, slightly displaced to a hollow fcc site compared to the thiol adsorption case. The C-S axis of the thiolate is tilted by about 37°. The calculated adsorption energies show that the butanethiol and butanethiolate have similar adsorption ability. The computed reaction pathway for the S-H dissociation gives an activation energy of 0.98 eV indicating that the thiolate formation from thiol, although not spontaneous at room temperature, might be feasible on silver surfaces. The dissociation process induces both adsorbate and surface polarization with a significant charge transfer from the substrate to the adsorbate.

  5. The nature of the observed free-electron-like state in a PTCDA monolayer on Ag(111)

    OpenAIRE

    Dyer, Matthew S.; Persson, Mats

    2009-01-01

    A free-electron like band has recently been observed in a monolayer of PTCDA (3,4,9,10-perylene tetracarboxylic dianhydride) molecules on Ag(111) by two-photon photoemission [Schwalb et al., Phys. Rev. Lett. 101, 146801 (2008)] and scanning tunneling spectroscopy [Temirov et al., Nature 444, 350 (2006)]. Using density functional theory calculations, we find that the observed free-electron like band originates from the Shockley surface state band being dramatically shifted up in energy by the ...

  6. The nature of the observed free-electron-like state in a PTCDA monolayer on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Dyer, Matthew S; Persson, Mats, E-mail: msd30@liv.ac.u [Surface Science Research Centre, University of Liverpool, Liverpool L69 3BX (United Kingdom)

    2010-06-15

    A free-electron-like band has recently been observed in a monolayer of 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) molecules on Ag(111) by two-photon photoemission (Schwalb et al 2008 Phys. Rev. Lett. 101 146801) and scanning tunneling spectroscopy (Temirov et al 2006 Nature 444 350). Using density functional theory calculations, we find that the observed free-electron-like band originates from the Shockley surface state band being dramatically shifted up in energy by the interaction with the adsorbed molecules, while it also acquires a substantial admixture with a molecular band.

  7. The nature of the observed free-electron-like state in a PTCDA monolayer on Ag(111)

    International Nuclear Information System (INIS)

    A free-electron-like band has recently been observed in a monolayer of 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) molecules on Ag(111) by two-photon photoemission (Schwalb et al 2008 Phys. Rev. Lett. 101 146801) and scanning tunneling spectroscopy (Temirov et al 2006 Nature 444 350). Using density functional theory calculations, we find that the observed free-electron-like band originates from the Shockley surface state band being dramatically shifted up in energy by the interaction with the adsorbed molecules, while it also acquires a substantial admixture with a molecular band.

  8. 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.

  9. 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.

  10. Monitoring Si growth on Ag(111) with scanning tunneling microscopy reveals that silicene structure involves silver atoms

    International Nuclear Information System (INIS)

    Using scanning tunneling microscopy (STM), the elaboration of the so-called silicene layer on Ag(111) is monitored in real time during Si evaporation at different temperatures. It is shown that the growth of silicene is accompanied by the release of about 65% of the surface Ag atoms from the Si covered areas. We observe that Si islands develop on the Ag terraces and Si strips at the Ag step edges, progressively forming ordered (4×4), (√(13)×√(13)) R13.9°, and dotted phases. Meanwhile, displaced Ag atoms group to develop additional bare Ag terraces growing round the Si islands from the pristine Ag step edges. This indicates a strong interaction between Si and Ag atoms, with an important modification of the Ag substrate beneath the surface layer. This observation is in contradiction with the picture of a silicene layer weakly interacting with the unreconstructed Ag substrate, and strongly indicates that the structure of silicene on Ag(111) corresponds either to a Si-Ag surface alloy or to a Si plane covered with Ag atoms

  11. 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.

  12. Self-learning kinetic Monte Carlo simulations of self-diffusion of small Ag islands on the Ag(111) surface

    Science.gov (United States)

    Islamuddin Shah, Syed; Nandipati, Giridhar; Karim, Altaf; Rahman, Talat S.

    2016-01-01

    We studied self-diffusion of small two-dimensional Ag islands, containing up to ten atoms, on the Ag(111) surface using self-learning kinetic Monte Carlo (SLKMC) simulations. Activation barriers are calculated using the semi-empirical embedded atom method (EAM) potential. We find that two- to seven-atom islands primarily diffuse via concerted translation processes with small contributions from multi-atom and single-atom processes, while eight- to ten-atom islands diffuse via single-atom processes, especially edge diffusion, corner rounding and kink detachment, along with a minimal contribution from concerted processes. For each island size, we give a detailed description of the important processes, and their activation barriers, responsible for its diffusion.

  13. Structure and growth of dotriacontane films on SiO_2 and Ag(111) surfaces: synchrotron X-ray scattering and molecular dynamics simulations

    DEFF Research Database (Denmark)

    Mo, H.; Trogisch, S.; Taub, H.;

    2004-01-01

    We report synchrotron X-ray scattering experiments and molecular dynamics simulations of the structure and growth mode of dotriacontane (n-C32H(66) or C32) films adsorbed on Ag(111) and SiO2-coated Si(100) substrates. On the SiO2 surface, the X-ray measurements confirm a structural model of the...

  14. Complex Stoichiometry-Dependent Reordering of 3,4,9,10-Perylenetetracarboxylic Dianhydride on Ag(111) upon K Intercalation.

    Science.gov (United States)

    Zwick, Christian; Baby, Anu; Gruenewald, Marco; Verwüster, Elisabeth; Hofmann, Oliver T; Forker, Roman; Fratesi, Guido; Brivio, Gian Paolo; Zojer, Egbert; Fritz, Torsten

    2016-02-23

    Alkali metal atoms are frequently used for simple yet efficient n-type doping of organic semiconductors and as an ingredient of the recently discovered polycyclic aromatic hydrocarbon superconductors. However, the incorporation of dopants from the gas phase into molecular crystal structures needs to be controlled and well understood in order to optimize the electronic properties (charge carrier density and mobility) of the target material. Here, we report that potassium intercalation into the pristine 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) monolayer domains on a Ag(111) substrate induces distinct stoichiometry-dependent structural reordering processes, resulting in highly ordered and large KxPTCDA domains. The emerging structures are analyzed by low-temperature scanning tunneling microscopy, scanning tunneling hydrogen microscopy (ST[H]M), and low-energy electron diffraction as a function of the stoichiometry. The analysis of the measurements is corroborated by density functional theory calculations. These turn out to be essential for a correct interpretation of the experimental ST[H]M data. The epitaxy types for all intercalated stages are determined as point-on-line. The K atoms adsorb in the vicinity of the oxygen atoms of the PTCDA molecules, and their positions are determined with sub-Ångström precision. This is a crucial prerequisite for the prospective assessment of the electronic properties of such composite films, as they depend rather sensitively on the mutual alignment between donor atoms and acceptor molecules. Our results demonstrate that only the combination of experimental and theoretical approaches allows for an unambiguous explanation of the pronounced reordering of KxPTCDA/Ag(111) upon changing the K content. PMID:26718635

  15. 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.

  16. Slow positrons in metal single crystals. I. Positronium formation at Ag(100), Ag(111), and Cu(111) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Lynn, K.G.; Welch, D.O.

    1980-07-01

    Monoenergetic positrons, with an incident energy of 0 --5 keV, were focused onto Ag(100), Ag(111), and Cu(111) surfaces with submonolayer contamination, and positronium formation was studied as a function of sample temperature from 300 to 1200 K. The data were fitted with a simple positron diffusion model including surface and vacancy trapping, assuming that positronium is formed only at the surface. The formation of part of the positronium fraction is found to be a temperature-activated process which is identified as detrapping from a surface state, and an estimate of the binding energy in this trap is deduced. The diffusion length is found to be only slightly temperature dependent between room temperature and the onset of vacancy trapping. At the higher sample temperatures positron trapping at thermally generated vacancies is observed by the decrease in the positron diffusion length at the higher incident voltages. A vacancy formation energy is extracted from the data and is generally found to be lower than the values obtained from bulk measurements.

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

    OpenAIRE

    Gernot Langewisch; Jens Falter; André Schirmeisen; Harald Fuchs

    2014-01-01

    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 tha...

  18. Reactivity of Ultra-Thin ZnO Films Supported by Ag(111) and Cu(111): A Comparison to ZnO/Pt(111)

    OpenAIRE

    Pan, Q.; B. Liu; McBriarty, M.; Martynova, Y.; Groot, I. de; Wang, S.; Bedzyk, M.; Shaikhutdinov, S.; Freund, H.

    2014-01-01

    We studied structure and reactivity of ZnO(0001) ultrathin films grown on Ag(111) and Cu(111) single crystal surfaces. Structural characterization was carried out by scanning tunneling microscopy, Auger electron spectroscopy, low-energy electron diffraction, and temperature programmed desorption. The CO oxidation behavior of the films was studied at low temperature (450 K) at near atmospheric pressures using gas chromatography. For ZnO/Cu(111), it is shown that under reaction conditions ZnO r...

  19. Adsorbatinduzierte richtungsabhängige Facettierung und selbstorganisierte Domänen-Musterbildung auf vizinalen Ag(111)-Oberflächen

    OpenAIRE

    Schmitt, Stefan

    2007-01-01

    Die vorliegende Arbeit beschäftigt sich mit den strukturellen Aspekten einer adsorbat-induzierten Facettierung von vizinalen Ag(111)-Oberflächen. Bei dem Adsorbat handelte es sich um das organische Molekül Perylen-3,4,9,10-Tetracarbonsäure-Dianhydrid (PTCDA). Die Experimente wurden unter Ultrahochvakuum-Bedingungen durchgeführt, die Charakterisierung erfolgte hauptsächlich mit den Messmethoden Rastertunnelmikroskopie (STM) und niederenergetische Elektronenbeugung (LEED). Das planare Farbstoff...

  20. Photoelektronenspektroskopische Untersuchungen zur Adsorption und Reaktivität von Co(II)-, Zn(II)- und Fe(II)-Porphyrinen auf Ag(111)

    OpenAIRE

    Flechtner, Ken-Dominic

    2007-01-01

    Im Rahmen der vorliegenden Arbeit wurden verschiedene Metalloporphyrinschichten im Ultrahochvakuum auf Ag(111) bezüglich der Wechselwirkung mit der Silberoberfläche, der In Situ Herstellung solcher Metalloporphyrinschichten und der Koordination kleiner Moleküle in Axialposition untersucht. Das Ultrahochvakuum eröffnet dabei die Möglichkeit, die Eigenschaften, wie Reaktivität oder elektronische Struktur der Metalloporphyrine im lösungsmittelfreien Zustand zu studieren, d.h. störungsfrei zu cha...

  1. Direct Visualization of Surface Phase of Oxygen Molecules Physisorbed on the Ag(111) Surface: A Two-dimensional Quantum Spin System

    Science.gov (United States)

    Yamamoto, Shunji; Yoshida, Yasuo; Imada, Hiroshi; Kim, Yousoo; Hasegawa, Yukio

    Oxygen molecule (O2) is one of the smallest molecular magnets with an S = 1 quantum spin. This makes O2 attractive as a building block of low-dimensional (LD) quantum spin systems. Recently, the existence of a spin in physisorbed O2 on Ag(111) was confirmed by the ortho-para conversion of molecular hydrogen. Therefore, there is a strong need for STM-based techniques with single-molecule resolution in order to verify the potential of the O2/Ag(111) for LD quantum spin systems. Here we report the real-space observation of oxygen molecules physisorbed on an Ag(111) surface by using low-temperature scanning tunneling microscopy and spectroscopy. A well-ordered O2 structure was observed, and the lattice was distorted from an isosceles triangular lattice. The distortion can be explained by the competition between the magnetic and elastic instabilities of the O2 lattice. In differential tunneling conductance spectra, we found no feature of the Kondo resonance at 4.7 K; in contrast, the physisorbed O2 on Ag(110) showed a clear Kondo resonance at 18 K. Based on these observations, we discuss the realization of an S = 1 two-dimensional antiferromagnetic quantum spin system.

  2. 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.

  3. Self-assembled two-dimensional nanoporous molecular arrays and photoinduced polymerization of 4-bromo-4′-hydroxybiphenyl on Ag(111)

    International Nuclear Information System (INIS)

    Self-assembled two-dimensional molecular arrays and photoinduced polymerization of 4-bromo-4′-hydroxybiphenyl on Ag(111) were studied using low-temperature scanning tunneling microscopy combined with density functional theory calculations. Square-like self-assembled structures of 4-bromo-4′-hydroxybiphenyl stabilized by intermolecular hydrogen and halogen bonds were transformed into hexagonal nanopores of biphenyl biradicals by 266 nm UV laser irradiation at 80 K. The biradicals further coupled to each other and formed covalently linked polyphenylene polymer chains at room temperature

  4. Self-assembled two-dimensional nanoporous molecular arrays and photoinduced polymerization of 4-bromo-4′-hydroxybiphenyl on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Qian; He, Jing Hui [Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore); Singapore-Peking University Research Centre for a Sustainable Low-Carbon Future, 1 CREATE Way, #15-01, CREATE Tower, Singapore 138602 (Singapore); Zhang, Jia Lin [Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore); Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China); Wu, Kai [Singapore-Peking University Research Centre for a Sustainable Low-Carbon Future, 1 CREATE Way, #15-01, CREATE Tower, Singapore 138602 (Singapore); BNLMS, SKLSCUSS, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Xu, Guo Qin [Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore); Singapore-Peking University Research Centre for a Sustainable Low-Carbon Future, 1 CREATE Way, #15-01, CREATE Tower, Singapore 138602 (Singapore); National University of Singapore (Suzhou) Research Institute, Suzhou (China); Wee, Andrew Thye Shen [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Chen, Wei, E-mail: phycw@nus.edu.sg [Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore); Singapore-Peking University Research Centre for a Sustainable Low-Carbon Future, 1 CREATE Way, #15-01, CREATE Tower, Singapore 138602 (Singapore); National University of Singapore (Suzhou) Research Institute, Suzhou (China); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore)

    2015-03-14

    Self-assembled two-dimensional molecular arrays and photoinduced polymerization of 4-bromo-4′-hydroxybiphenyl on Ag(111) were studied using low-temperature scanning tunneling microscopy combined with density functional theory calculations. Square-like self-assembled structures of 4-bromo-4′-hydroxybiphenyl stabilized by intermolecular hydrogen and halogen bonds were transformed into hexagonal nanopores of biphenyl biradicals by 266 nm UV laser irradiation at 80 K. The biradicals further coupled to each other and formed covalently linked polyphenylene polymer chains at room temperature.

  5. Investigation of localization of DNA molecules using triangular metal electrodes with varying separation

    Science.gov (United States)

    Prasad, D. Nagendra; Ghonge, Sudarshan; Banerjee, Souri

    2016-04-01

    In this paper we investigate the effect of separation of triangular metal electrodes with both convex and concave geometries, on the localization of suspended DNA molecules under the combined effect of dielectrophoresis and AC electro-osmosis through simulations using COMSOL Multiphysics. Trapping points are realized within the electrodes which are found to vary with the separation of the electrodes.

  6. Investigation of Bioglass-Electrode Interfaces after Thermal Poling

    OpenAIRE

    Mariappan, C. R.; Roling, B.

    2007-01-01

    Electrical and electrochemical processes in a bioactive soda-lime phosphosilicate glasses and in a bioabsorbable soda-lime phosphate glass during thermal poling were studied by means of thermally stimulated depolarization current measurements, ac impedance spectroscopy, and SEM/EDX analyses. The thermal poling was done by sputtering thin Pt electrode films onto the faces of the glass samples and by applying voltages up to 1 kV to the electrodes at temperatures up to 513 K. The poling leads to...

  7. Investigation of vapour-grown conductive polymer/heteropolyacid electrodes

    International Nuclear Information System (INIS)

    Heteropolyacid-doped conductive polymer coatings were grown by vapour transport of monomer (pyrrole or N-methylpyrrole) onto carbon paper coated with aqueous oxidant solutions (heteropolyacids or iron(III) chloride). Coated electrodes were studied by scanning electron microscopy and cyclic voltammetry. Polymer/heteropolyanion coatings had smooth morphologies giving pseudocapacitance of up to 422 F g-1 (with respect to active polymer material) and 0.45 F cm-2 (geometric area of the electrode)

  8. Comparative investigation on electrochemical behavior of hydroquinone at carbon ionic liquid electrode, ionic liquid modified carbon paste electrode and carbon paste electrode

    International Nuclear Information System (INIS)

    Ionic liquid, 1-heptyl-3-methylimidazolium hexafluorophosphate (HMIMPF6), has been used to fabricate two new electrodes, carbon ionic liquid electrode (CILE) and ionic liquid modified carbon paste electrode (IL/CPE), using graphite powder mixed with HMIMPF6 or the mixture of HMIMPF6/paraffin liquid as the binder, respectively. The electrochemical behaviors of hydroquinone at the CILE, the IL/CPE and the CPE were investigated in phosphate buffer solution. At all these electrodes, hydroquinone showed a pair of redox peaks. The order of the current response and the standard rate constant of hydroquinone at these electrodes were as follows: CILE > IL/CPE > CPE, while the peak-to-peak potential separation was in an opposite sequence: CILE < IL/CPE < CPE. The results show the superiority of CILE to IL/CPE and CPE, and IL/CPE to CPE in terms of promoting electron transfer, improving reversibility and enhancing sensitivity. The CILE was chosen as working electrode to determine hydroquinone by differential pulse voltammetry, which can be used for sensitive, simple and rapid determination of hydroquinone in medicated skin cosmetic cream

  9. 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.

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

    Science.gov (United States)

    Langewisch, Gernot; Falter, Jens; Schirmeisen, André; Fuchs, Harald

    2014-01-01

    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. PMID:24611130

  11. 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.

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

    Science.gov (United States)

    Langewisch, Gernot; Falter, Jens; Fuchs, Harald

    2014-01-01

    Summary 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. PMID:24611130

  13. 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.

  14. Investigation of copper electrodes for mercuric iodide detector applications

    Energy Technology Data Exchange (ETDEWEB)

    Bao, X.J.; Schlesinger, T.E. (Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA (USA)); James, R.B.; Stulen, R.H. (Advanced Materials Division, Sandia National Laboratories, Livermore, CA (USA)); Ortale, C.; van den Berg, L. (EG G Energy Measurements, Inc., Goleta, CA (USA))

    1990-06-15

    Copper diffusion in mercuric iodide was studied by low-temperature photoluminescence (PL) spectroscopy and Auger electron spectroscopy. A broad radiative emission band at a wavelength of about 6720 A in the PL spectra was found to be related to Cu incorporation in the crystal. PL spectra obtained from surface doping experiments indicate that Cu is a rapid diffuser in HgI{sub 2} bulk material. Auger electron spectroscopy performed as a function of depth from the crystal surface confirms the rapid bulk diffusion process of Cu in HgI{sub 2}. Fabrication of HgI{sub 2} nuclear detectors with Cu electrodes indicates that Cu is not acceptable as an electrode material, which is consistent with the fact that it diffuses easily into the bulk crystal and introduces new radiative recombination centers.

  15. Investigation of copper electrodes for mercuric iodide detector applications

    Science.gov (United States)

    Bao, X. J.; Schlesinger, T. E.; James, R. B.; Stulen, R. H.; Ortale, C.; van den Berg, L.

    1990-06-01

    Copper diffusion in mercuric iodide was studied by low-temperature photoluminescence (PL) spectroscopy and Auger electron spectroscopy. A broad radiative emission band at a wavelength of about 6720 Å in the PL spectra was found to be related to Cu incorporation in the crystal. PL spectra obtained from surface doping experiments indicate that Cu is a rapid diffuser in HgI2 bulk material. Auger electron spectroscopy performed as a function of depth from the crystal surface confirms the rapid bulk diffusion process of Cu in HgI2. Fabrication of HgI2 nuclear detectors with Cu electrodes indicates that Cu is not acceptable as an electrode material, which is consistent with the fact that it diffuses easily into the bulk crystal and introduces new radiative recombination centers.

  16. The Investigation of EDM Parameters on Electrode Wear Ratio

    OpenAIRE

    Reza Atefi; Navid Javam; Ali Razmavar; Farhad Teimoori

    2012-01-01

    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 resul...

  17. Electrochemical investigation of platinum electrode in solid electrolyte cell

    Energy Technology Data Exchange (ETDEWEB)

    Jaccoud, Arnaud; Foti, Gyoergy; Comninellis, Christos [Ecole Polytechnique Federale de Lausanne (EPFL), Institute of Chemical Sciences and Engineering, CH-1015 Lausanne (Switzerland)

    2006-01-05

    Electro-oxidation of platinum film electrode deposited on yttria-stabilized zirconia (YSZ) is examined in situ using potential programmed voltammetry at 450 C in oxygen containing atmosphere. Under prolonged anodic oxidation different sorts of oxidized species are formed which are consumed subsequently during a linear cathodic potential scan resulting in three distinct reduction peaks, one of them being fairly reversible while the two others strongly irreversible. Higher oxidation potential and longer time of polarization favor the irreversible processes. The coexistence of three electrochemical processes is explained with the extension of the triple phase boundary. The rapid first process is identified as formation of PtO{sub x} at the electrode/metal interface, the second process - a much slower, parallel one - is related to the phenomenon of oxygen backspillover at the metal/gas interface, and the slowest third process - consecutive to the first one - is attributed to growth of the PtO{sub x} layer at the electrode/metal interface toward the bulk of the metal by analogy to electro-oxidation of platinum in aqueous liquid electrochemistry. (authors)

  18. 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 with...

  19. 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.

  20. Adsorption geometry, conformation, and electronic structure of 2H-octaethylporphyrin on Ag(111) and Fe metalation in ultra high vacuum

    Science.gov (United States)

    Borghetti, Patrizia; Santo, Giovanni Di; Castellarin-Cudia, Carla; Fanetti, Mattia; Sangaletti, Luigi; Magnano, Elena; Bondino, Federica; Goldoni, Andrea

    2013-04-01

    Due to the growing interest in the ferromagnetic properties of Fe-octaethylporphyrins (Fe-OEP) for applications in spintronics, methods to produce stable Fe-porphyrins with no Cl atoms are highly demanded. Here, we demonstrate the formation of Fe-OEP layers on Ag(111) single crystal by the ultra high vacuum in situ metalation of the free-base 2H-2,3,7,8,12,13,17,18-octaethylporphyrin (2H-OEP) molecules. The metalation proceeds exactly as in the case of 2H-5,10,15,20-tetraphenylporphyrin (2H-TPP) on the same substrate. An extensive surface characterization by means of X-ray photoemission spectroscopy, valence band photoemission, and NEXAFS with synchrotron radiation light provides information on molecular conformation and electronic structure in the monolayer and multilayer cases. We demonstrate that the presence of the ethyl groups affects the tilt of the adsorbed molecules, the conformation of the macrocycle, and the polarization screening in multilayers, but has only a minor effect in the metalation process with respect to 2H-TPP.

  1. 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...

  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.

    2016-07-01

    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.

  3. 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. PMID:27421423

  4. 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.

  5. Self-Diffusion of small Ag and Ni islands on Ag(111) and Ni(111) using the self-learning kinetic Monte Carlo method

    Science.gov (United States)

    Islamuddin Shah, Syed; Nandipati, Giridhar; Kara, Abdelkader; Rahman, Talat S.

    2012-02-01

    We have applied a modified Self-Learning Kinetic Monte Carlo (SLKMC) method [1] to examine the self-diffusion of small Ag and Ni islands, containing up to 10 atom, on the (111) surface of the respective metal. The pattern recognition scheme in this new SLKMC method allows occupancy of the fcc, hcp and top sites on the fcc(111) surface and employs them to identify the local neighborhood around a central atom. Molecular static calculations with semi empirical interatomic potential and reliable techniques for saddle point search revealed several new diffusion mechanisms that contribute to the diffusion of small islands. For comparison we have also evaluated the diffusion characteristics of Cu clusters on Cu(111) and compared results with previous findings [2]. Our results show a linear increase in effective energy barriers scaling almost as 0.043, 0.051 and 0.064 eV/atom for the Cu/Cu(111), Ag/Ag(111), and Ni/Ni(111) systems, respectively. For all three systems, diffusion of small islands proceeds mainly through concerted motion, although several multiple and single atom processes also contribute. [1] Oleg Trushin et al. Phys. Rev. B 72, 115401 (2005) [2] Altaf Karim et al. Phys. Rev. B 73, 165411 (2006)

  6. Normal-incidence x-ray standing-wave determination of the adsorption geometry of PTCDA on Ag(111): Comparison of the ordered room-temperature and disordered low-temperature phases

    OpenAIRE

    Hauschild, A.; Temirov, R.; Soubatch, S.; Bauer, O.; Schöll, A.; Cowie, B.C.C.; Lee, T. -L.; Tautz, F. S.; Sokolowski, M.

    2010-01-01

    Normal incidence x-ray standing wave (NIXSW) experiments have been performed for monolayers of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) adsorbed on the Ag(111) surface. Two phases were analyzed: the low-temperature phase (LT phase), which is disordered and obtained for deposition at substrate temperatures below 150 K, and the ordered phase, which is obtained for deposition at room temperature (RT phase). From the NIXSW analysis the vertical bonding distances to the Ag surface wer...

  7. 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

  8. Investigation on the Corona Discharge in Blade-to-Plane Electrode Configuration

    Science.gov (United States)

    Kaci, Meziane; Ait Said, Hakim; Laifaoui, Abdelkrim; Aissou, Massinissa; Nouri, Hamou; Zebboudj, Youcef

    2015-12-01

    The aim of this work is to analyze the characteristics of the corona discharge in blade-to-plane electrode configuration. An experimental investigation has been carried out on the geometric parameters that govern the formation of both positive and negative corona discharges, such as the inter-electrode distance, the blade-to-blade spacing, and the number of the discharging blades. The current-voltage characteristics, the breakdown voltage, and the Warburg current distribution were measured. The assisted corona discharge is an example of a blade electrode discharge that can be used to reduce the operating voltage of a conventional corona discharge. The current-voltage characteristics of both positive and negative corona discharges in a blade-to-plane electrode configuration are of the Townsend's law form. The general formula proposed by Meng et al. can also be applied in this system. It has been shown that the breakdown voltage and the corona conductance are strongly affected by the inter-electrode distance. To obtain a maximum current, the blade electrodes should be distant from each other by a value of 2 a ≥ h. To obtain a constant value of current, the blade electrodes should be separated by a value of 2 a >> h, confirming the Cooperman's law. The current density distribution is satisfied; an exponent of 5.0 is taken for positive polarity and an exponent of 4.8 for negative polarity.

  9. 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.

  10. Electrochemical investigation of thermically treated graphene oxides as electrode materials for vanadium redox flow battery

    International Nuclear Information System (INIS)

    Highlights: • Graphene oxide is synthesized at high temperatures in a reducing environment. • Treated graphene oxide-based electrodes are prepared by the wet impregnation method. • Electrochemical performance is evaluated as a function of the physico-chemical properties. - Abstract: Thermically treated graphene oxides (TT-GOs) are synthesized at different temperatures, 100 °C, 150 °C, 200 °C and 300 °C in a reducing environment (20% H2/He) and investigated as electrode materials for vanadium redox flow battery (VRFB) applications. The treated graphene oxide-based electrodes are prepared by the wet impregnation method using carbon felt (CF) as support. The main aim is to achieve a suitable distribution of the dispersed graphene oxides on the CF surface in order to investigate the electrocatalytic activity for the VO2+/VO2+ and V2+/V3+ redox reactions in the perspective of a feasible large area electrodes scale-up for battery configuration of practical interest. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are carried out in a three electrode half-cell to characterize the electrochemical properties of the TT-GO-based electrodes. Physico-chemical characterizations are carried out to corroborate the electrochemical results. The TT-GO sample treated at 100 °C (TT-GO-100) shows the highest electrocatalytic activity in terms of peak to peak separation (ΔE = 0.03 V) and current density intensity (∼0.24 A cm−2 at 30 mV/s) both toward the VO2+/VO2+ and V2+/V3+ redox reactions. This result is correlated to the presence of hydroxyl (−OH) and carboxyl (−COOH) species that act as active sites. A valid candidate is individuated as effective anode and cathode electrode in the perspective of electrodes scale-up for battery configuration of practical interest

  11. Investigations of rate limitation in nanostructured composite electrodes and experiments towards a 3D Li-ion microbattery

    OpenAIRE

    Johns, Phillip A.

    2011-01-01

    The factors effecting discharge rate limitation within LiFePO4 composite electrode structures have been investigated. It was found that for composite electrodes containing ‘small particles’ of active material solid state processes are not necessarily rate limiting. A simple model has been developed to describe the rate limitation that occurs in the composite electrode structure due to electrolyte concentration, electrode thickness and lithium ion transference number. The conformal electrodepo...

  12. 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.

  13. Observation and modeling of conformational molecular structures driving the self-assembly of tri-adamantyl benzene on Ag(111).

    Science.gov (United States)

    Calmettes, Bastien; Estrampes, Nicolas; Coudret, Christophe; Roussel, Thomas J; Faraudo, Jordi; Coratger, Roland

    2016-07-27

    The self-organization of tri-adamantyl (TAB) benzene molecules has been investigated using low temperature scanning tunneling microscopy (LT-STM). The molecular structures have also been studied using molecular modeling. In particular, these calculations have been performed on large areas (1000 nm(2)) from the atomic structure of the molecular building block, combining molecular dynamics (MD) and Monte-Carlo (MC) approaches. These investigations show that the structure of the molecule and its flexibility allow for the formation of different networks as a function of surface coverage. The calculations demonstrate that the stability of the largest structures is obtained through the increase of the interfacial energy induced by the rotation of the adamantyl groups, a behavior whose consequences explain the subtle contrasts observed in the experimental STM images. PMID:26667964

  14. 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

    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...

  15. 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...

  16. 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...... for thick film PZT sintered at 850degC. E-beam evaporated Al and Pt is patterned on PZT with a lift-off process with a line width down to 3 mum. The roughness of the PZT is found to have a strong influence on the conductance of the top electrode....

  17. 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.

  18. 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.

  19. 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).

  20. Investigations on structural iron electrochemical properties in layered silicates using massive mica electrodes

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Nuclear waste repositories are being installed in deep excavated rock formations in some places in Europe to isolate and store radioactive waste. In France, the Callovo-Oxfordian formation (COx) is a potential candidate for a nuclear waste repository. The redox reactivity of COx clay rock samples are already under study using microscopic, spectrometric and wet analysis techniques. In order to cross and overcome certain limits by improvement in the knowledge, specific electrodes should be constructed and devoted to the deepening of the electrochemical behaviour of the COx system in different situations. Iron is one of the most common redox species in soils and sedimentary rocks. Iron-bearing phyllosilicates play key roles in various biogeochemical processes. The complexity of the physical and chemical changes involving their structural iron makes the studies of its redox properties challenging. Most of the recent reported efforts were focused on probing Fe redox on finely powdered clay particles, and have been hampered by inadequate interactions between particles and electrodes. Moreover, such experiments usually involve redox probe ions, thus adding supplementary difficulties in the determination of structural iron redox parameters such as redox potential (Eh) and kinetics. The present study aims at qualitatively investigating the above mentioned phenomena on minerals like iron-bearing micas. In the current work, we present initial insights regarding efforts to build a direct electrical interface between solid electrodes and conveniently shaped macroscopic mica crystals in order to investigate the redox properties of structural iron in dry and aqueous environments, in the presence of representative perturbations. A classical three electrode system has been used for voltammetric measurements. Platinum plate was the counter electrode. Potentials have been measured against either silver-silver chloride electrode or

  1. 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.

  2. Voltammetric investigation of the dissociative electron transfer to polychloromethanes at catalytic and non-catalytic electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Isse, Abdirisak Ahmed; Sandona, Giancarlo; Durante, Christian [Dipartimento di Scienze Chimiche, Universita di Padova, Via Marzolo 1, 35131 Padova (Italy); Gennaro, Armando [Dipartimento di Scienze Chimiche, Universita di Padova, Via Marzolo 1, 35131 Padova (Italy)], E-mail: armando.gennaro@unipd.it

    2009-04-30

    The electrochemical behavior of CCl{sub 4}, CHCl{sub 3} and CH{sub 2}Cl{sub 2} has been investigated by cyclic voltammetry at glassy carbon and silver electrodes in DMF + 0.1 M Et{sub 4}NClO{sub 4} in the absence and presence of a good proton donor. At both electrodes, each compound exhibits a series of reduction peaks which represent sequential hydrodechlorination steps up to methane. The nature of the electrode material and the proton availability of the medium affect drastically the voltammetric pattern of the compounds. Silver exhibits extraordinary electrocatalytic properties toward the reduction process, with positive shifts of the peak potentials of about 0.57-0.95 V as compared to glassy carbon. Reduction of any polychloromethane, CH{sub n}Cl{sub (4-n)} (n = 0-2), yields the carbanion CH{sub n}Cl{sub (3-n)}{sup -} which partitions into two reaction channels: (i) protonation and (ii) Cl{sup -} elimination to give a carbene :CH{sub n}Cl{sub (2-n)}. If a strong proton donor is added into the solution, sequential hydrodechlorination becomes the principal reaction route at both electrodes. When, instead, purposely added acid is not present in solution, both reaction pathways ought to be considered. In these conditions, when possible, self-protonation reactions play an important role in the overall reduction process.

  3. 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.

  4. 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.

  5. 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...

  6. 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...

  7. Investigation of Lithium-Air Battery Discharge Product Formed on Carbon Nanotube and Nanofiber Electrodes

    Science.gov (United States)

    Mitchell, Robert Revell, III

    Carbon nanotubes have been actively investigated for integration in a wide variety of applications since their discovery over 20 years ago. Their myriad desirable material properties including exceptional mechanical strength, high thermal conductivities, large surface-to-volume ratios, and considerable electrical conductivities, which are attributable to a quantum mechanical ability to conduct electrons ballistically, have continued to motivate interest in this material system. While a variety of synthesis techniques exist, carbon nanotubes and nanofibers are most often conveniently synthesized using chemical vapor deposition (CVD), which involves their catalyzed growth from transition metal nanoparticles. Vertically-aligned nanotube and nanofiber carpets produced using CVD have been utilized in a variety of applications including those related to energy storage. Li-air (Li-O2) batteries have received much interest recently because of their very high theoretical energy densities (3200 Wh/kgLi2O2 ). which make them ideal candidates for energy storage devices for future fully-electric vehicles. During operation of a Li-air battery O2 is reduced on the surface a porous air cathode, reacting with Li-ions to form lithium peroxide (Li-O2). Unlike the intercalation reactions of Li-ion batteries, discharge in a Li-air cell is analogous to an electrodeposition process involving the nucleation and growth of the depositing species on a foreign substrate. Carbon nanofiber electrodes were synthesized on porous substrates using a chemical vapor deposition process and then assembled into Li-O2 cells. The large surface to volume ratio and low density of carbon nanofiber electrodes were found to yield a very high gravimetric energy density in Li-O 2 cells, approaching 75% of the theoretical energy density for Li 2O2. Further, the carbon nanofiber electrodes were found to be excellent platforms for conducting ex situ electron microscopy investigations of the deposition Li2O2 phase

  8. 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.

  9. 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.

  10. Using Silver Nano-Particle Ink in Electrode Fabrication of High Frequency Copolymer Ultrasonic Transducers: Modeling and Experimental Investigation

    Directory of Open Access Journals (Sweden)

    Adit Decharat

    2015-04-01

    Full Text Available High frequency polymer-based ultrasonic transducers are produced with electrodes thicknesses typical for printed electrodes obtained from silver (Ag nano-particle inks. An analytical three-port network is used to study the acoustic effects imposed by a thick electrode in a typical layered transducer configuration. Results from the network model are compared to experimental findings for the implemented transducer configuration, to obtain a better understanding of acoustical effects caused by the additional printed mass loading. The proposed investigation might be supportive of identification of suitable electrode-depositing methods. It is also believed to be useful as a feasibility study for printed Ag-based electrodes in high frequency transducers, which may reduce both the cost and production complexity of these devices.

  11. 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

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

    International Nuclear Information System (INIS)

    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 (∼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 potentiometric circuit. The evaluation criteria used in the study included the device-to-device variation in sensitivity of the pH sensors and their sensitivity variation as a function of time. The results indicated the importance of the choice of binder type in particular on the performance characteristics. Reproducible device-to-device variation in sensitivity was determined for the best inks found, whatever the ink fabrication batch. A reduction in the sensitivity variation with time has been determined using the mathematical models derived from an experimental plan. The lack of reproducibility of the sensitivity magnitude, regardless of the ink manufacturing batch, seems to be a recurrent problem with prototype inks. Experimental sub-Nernstian responses are discussed in the light of possible pH mechanisms. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Gac, Arnaud

    2002-07-01

    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 potentiometric circuit. The evaluation criteria used in the study included the device-to-device variation in sensitivity of the pH sensors and their sensitivity variation as a function of time. The results indicated the importance of the choice of binder type in particular on the performance characteristics. Reproducible device-to-device variation in sensitivity was determined for the best inks found, whatever the ink fabrication batch. A reduction in the sensitivity variation with time has been determined using the mathematical models derived from an experimental plan. The lack of reproducibility of the sensitivity magnitude, regardless of the ink manufacturing batch, seems to be a recurrent problem with prototype inks. Experimental sub-Nernstian responses are discussed in the light of possible pH mechanisms. (author)

  14. Investigation on the dielectric properties of (Ba, Sr)TiO3 thin films on hybrid electrodes

    International Nuclear Information System (INIS)

    Ba0.65Sr0.35TiO3 (BST) thin films were deposited on Pt/Ti/SiO2/Si, RuO2/SiO2/Si and RuO2/Pt/Ti/SiO2/Si substrates by radio frequency magnetron sputtering technique. The effects of these bottom electrodes on the microstructure and dielectric properties of the BST thin films were investigated by using X-ray diffraction (XRD), atomic force microscope (AFM), transmission electron microscopy (TEM) and electrical measurements. The BST thin films on RuO2/Pt hybrid bottom electrodes exhibit good crystalline and interfacial structure with a thinner transition layer. Dielectric measurement reveals that the films on RuO2/Pt hybrid electrodes have comparable dielectric constant and loss tangent with the films on Pt electrode, and the dielectric tunability of BST films on RuO2/Pt reaches 38.2%, which is higher than that of BST films on a single Pt or RuO2 electrode. The BST thin films on RuO2/Pt exhibit lower leakage current density by nearly two orders' of magnitude than that on RuO2 electrode. The higher tunability and lower leakage current of the films on RuO2/Pt hybrid bottom electrodes are mainly attributed to the RuO2 layer, which facilitates the nucleation and growth of BST films, and inhibits the interfacial diffusion between the BST films and bottom electrodes. The results show a potential for RuO2/Pt hybrid electrodes replacing Pt electrode in microelectronic device applications.

  15. Investigation of Electrode Erosion Mechanism of Multi-Phase AC Arc by High-Speed Video Camera

    International Nuclear Information System (INIS)

    A multi-phase AC arc has been applied to the glass melting technology. However, the electrode erosion is one of the most considerable issues to be solved. In order to investigate the erosion mechanism of the multi-phase AC arc, the combination of the high-speed video camera and the band-pass filters was introduced to measure the electrode temperature. Results indicated the tip temperature of the electrode surface in the 12-phase arc was lower than that in the 2-phase arc, while erosion rate in 12-phase arc was higher than that in the 2-phase arc. Furthermore, the dynamic behaviour of the vapours in the arc was investigated by using the same high-speed camera system. The tungsten electrode mainly evaporates at the anodic period during AC cycle. The oxygen concentration in the arc increases with larger number of the phases, resulting in the higher erosion rate in the 12-phase arc.

  16. 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.

  17. Investigation of Effect of Welding Current on Welding Penetration in Covered Electrode Arc Welding And MIG Welding

    OpenAIRE

    Bekir ÇEVİK

    2013-01-01

    In this study, the effect of welding current on penetration in covered electrode arc welding and MIG (Metal Inert Gas) welding was investigated. St 37 quality steel materials were used in the experiments. Three different welding current (60, 90 and 120 A with covered electrode arc welding, 100, 125 and 155 A with MIG welding) was selected for welding process and was made 200 mm long weld. The welded specimens were cut particular lengths, then metallographic tests were performed. As a result o...

  18. Impedance spectroscopy investigation of electrophysical characteristics of the electrode-liquid crystal interface

    Science.gov (United States)

    Belyaev, B. A.; Drokin, N. A.

    2015-01-01

    The behavior of frequency dependences of the impedance of a capacitive measuring cell with a liquid crystal has been investigated in the frequency range from 10-1 to 105 Hz. A method for determining electrophysical characteristics of the liquid crystal in the bulk and at the liquid crystal-metal electrode interface has been proposed and tested for liquid crystals of the alkyl cyanobiphenyl series, which are doped with ionic surfactants. The method is based on the use of an equivalent electrical circuit, which makes it possible to approximate the impedance spectra with the required accuracy, and also on the determination of the frequency at the singular point in the impedance spectra, at which the reactive component of the electric current flowing through the liquid-crystal cell is negligible compared to the active component.

  19. 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.

  20. In situ X-ray diffraction investigation of zinc based electrode in Ni–Zn secondary batteries

    International Nuclear Information System (INIS)

    In situ/in operando X-ray diffraction coupled with electrochemical cycling of ZnO based electrodes in KOH electrolyte has been used as a powerful tool in order to investigate the influence of additives. The technique has been performed in order to highlight the role of bismuth based conductive additives on the cycling ability of the electrode. It enables to clearly evidence the conversion of zinc oxide to zinc metal. During the first charge, it also helps to visualize the conversion of Bi2O3 additive into metallic bismuth prior to ZnO reduction which leads to the formation of an electronic pathway at the nanometer scale complementary from the current collector and the TiN percolation conductive network. Additionally, each Bi2O3 grain seems to be converted in a single bismuth grain which is not agglomerated with other bismuth particles even after 50 cycles. This behaviour leads to a steady capacity of the zinc based electrode compared to the same electrode without Bi2O3 additive. Subsequently, in situ XRD investigation of Zn based negative electrode in nickel–zinc batteries can be a powerful tool to design new composite electrode with long term cycling efficiency

  1. Investigation of supercapacitors with carbon electrodes obtained from argon-acetylene arc plasma

    OpenAIRE

    Kavaliauskas, Žydrūnas

    2010-01-01

    The dissertation examines topics related to the formation of supercapacitors using plasma technology and their analysis. Plasma spray technology was used to form supercapacitors electrodes. Carbon was deposited on stainless steel surface using the atmospheric pressure argon-acetylene plasma. The deposition of nickel oxide on the surface of carbon electrodes was made using magnetron sputtering method. The influence of acetylene amount to the supercapacitors electrodes and the electrical charac...

  2. 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

    X-ray photoelectron spectroscopy studies were systematically carried out on the electrodes before and after the electrochemical stress tests in an aqueous electrolyte at 20 °C and 70 °C. The electrodes have different ionomer structures (no ionomer, only ionomer, physically mixed ionomer and hot...

  3. Investigation of Pt, Ti, TiN, and nano-porous carbon electrodes for implantable cardioverter-defibrillator applications

    Energy Technology Data Exchange (ETDEWEB)

    Norlin, A.; Pan, J.; Leygraf, C

    2004-09-15

    The electrochemical behavior and stability of Pt, Ti, TiN, and nano-porous carbon for implantable cardioverter-defibrillator (ICD) electrode application were investigated in a phosphate buffered saline solution. The electrochemical interfacial properties were examined by electrochemical impedance spectroscopy, and the potential and current response during ICD shock pulses were recorded by a digital oscilloscope. Changes in surface composition and structure were investigated using X-ray photoelectron spectroscopy and environmental scanning electron microscopy. When exposed to anodic 700 V shock pulses with duration of 10 ms, only Pt was stable, nano-porous carbon electrode was slightly attacked, whereas Ti and TiN electrodes suffered severe degradation. Upon cathodic shock pulsing, all the materials were stable, but Ti and TiN electrodes with a smooth surface showed evidence of hydrogen adsorption. Porous and rough electrodes produced less gas evolution compared to a smooth surfaces, due to a higher amount of charge transferred through non-Faradaic processes. The reason for this could be higher interfacial capacity due to the large surface area.

  4. The fabrication, characterisation and electrochemical investigation of screen-printed graphene electrodes.

    Science.gov (United States)

    Randviir, Edward P; Brownson, Dale A C; Metters, Jonathan P; Kadara, Rashid O; Banks, Craig E

    2014-03-14

    We report the fabrication, characterisation (SEM, Raman spectroscopy, XPS and ATR) and electrochemical implementation of novel screen-printed graphene electrodes. Electrochemical characterisation of the fabricated graphene electrodes is undertaken using an array of electroactive redox probes and biologically relevant analytes, namely: potassium ferrocyanide(II), hexaammine-ruthenium(III) chloride, N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), β-nicotinamide adenine dinucleotide (NADH), L-ascorbic acid (AA), uric acid (UA) and dopamine hydrochloride (DA). The electroanalytical capabilities of the fabricated electrodes are also considered towards the sensing of AA and DA. The electrochemical and (electro)analytical performances of the fabricated screen-printed graphene electrodes are considered with respect to the relative surface morphologies and material compositions (elucidated via SEM, Raman, XPS and ATR spectroscopy), the density of electronic states (% global coverage of edge-plane like sites/defects) and the specific fabrication conditions utilised. Comparisons are made between two screen-printed graphene electrodes and alternative graphite based screen-printed electrodes. The graphene electrodes are fabricated utilising two different commercially prepared 'graphene' inks, which have long screen ink lifetimes (>3 hours), thus this is the first report of a true mass-reproducible screen-printable graphene ink. Through employment of appropriate controls/comparisons we are able to report a critical assessment of these screen-printed graphene electrodes. This work is of high importance and demonstrates a proof-of-concept approach to screen-printed graphene electrodes that are highly reproducible, paving the way for mass-producible graphene sensing platforms in the future. PMID:24458292

  5. Electrochemical and spectroscopic investigations of immobilized de novo designed heme proteins on metal electrodes

    DEFF Research Database (Denmark)

    Albrecht, Tim; Li, WW; Ulstrup, Jens;

    2005-01-01

    configuration. The proteins possess different binding domains on the top surfaces of the bundles to allow for electrostatic, covalent, and hydrophobic binding to metal electrodes. Electrostatic immobilization was achieved for proteins with lysine-rich binding domains (MOP-P) that adsorb to electrodes covered by...... electron-transfer rate constant of 13 s(-1) is similar to those reported for natural heme proteins with comparable electron-transfer distances, which indicates that covalently bound synthetic heme proteins provide efficient electronic communication with a metal electrode as a prerequisite for potential...

  6. Investigation of the work function fluctuations of electrodes for high precision low energy experiments

    International Nuclear Information System (INIS)

    High precision experiments at low energies are used in several areas of fundamental physics. Examples are, a.o., high precision beta decay experiments and experiments using Penning traps for mass measurements or for g-factor measurements. The knowledge of the potentials and potential differences inside these experiments is crucial to achieve the desired sensitivities. However, the potentials are modified by the work function of the electrodes, which can show fluctuations of of several hundred meV, both spatially and temporally. For the low energy precision experiments aSPECT and KATRIN we have commissioned and studied a scanning Kelvin probe system to investigate the work function fluctuations of gold surfaces on different substrates. Since the Kelvin probe is a relative method, also photoelectron spectroscopy was performed additionally to obtain information on the absolute work functions. The temporal stability of the work functions of the surfaces was also tested, as well as the influence of standard cleaning procedures for ultra-high vacuum applications and bake-out. This poster presents the results of these measurements.

  7. Investigations of electrochemical oxygen transfer reaction on boron-doped diamond electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Kapalka, Agnieszka; Foti, Gyoergy [Institute of Chemical Sciences and Engineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Comninellis, Christos [Institute of Chemical Sciences and Engineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)], E-mail: christos.comninellis@epfl.ch

    2007-12-31

    In this paper, the electrochemical oxygen transfer reaction (EOTR) is studied on boron-doped diamond electrodes using simple C{sub 1} organic compounds (methanol and formic acid). The kinetics of both oxygen evolution (side reaction) and organics oxidation (main reaction) has been investigated using boron-doped diamond microelectrodes-array (BDD MEA). Oxygen evolution, in the high-potential region, takes place with a Tafel slope of 120 mV dec{sup -1} and zero reaction order with respect to H{sup +}. In the presence of organics, a shift of the polarization curves to lower potentials is observed while the Tafel slopes remain close to 120 mV dec{sup -1}. A simplified model of C{sub 1} organics oxidation is proposed. Both water discharge and organics oxidation are assumed to be fast reactions. The slowest step of the studied EOTR is the anodic discharge of hydroxyl radicals to oxygen. Further in this work, electrolysis of formic acid on boron-doped diamond macroelectrode is presented. In order to achieve 100% current efficiency, electrolysis was carried out under programmed current, in which the current density was adjusted to the limiting value.

  8. Investigation of membrane electrode assembly (MEA) hot-pressing parameters for proton exchange membrane fuel cell

    International Nuclear Information System (INIS)

    The hot-pressing conditions for fabricating the membrane electrode assembly (MEA) of a proton exchange membrane fuel cell (PEMFC) was investigated by using a 2n full factorial design. Time, temperature and pressure were key parameters that were varied from 500 to 1500 psi, 1 to 5 min and 100 to 160 deg. C, respectively. The results from the full factorial analysis indicated that the order of significance of the main MEA fabricating effects was temperature, pressure, time-temperature interaction and pressure-time-temperature interaction. By examining the cell performance curves, the lower fabrication conditions of temperature and pressure were suitable for MEA preparation. The conductive layer between the membrane and the catalyst layer became thin at high pressure and high temperature, as seen from scanning electron microscopy (SEM) images. In the ranges of condition studied, the most suitable hot-pressing condition for MEA fabrication was at 100 deg. C, 1000 psi and 2 min. This condition provided the highest maximum power density from the MEA and the best contact at the interfaces between the gas diffusion layer, the active layer and the electrolyte membrane. The experimental results were verified by testing with a commercial MEA in the same operating condition and with the same equipment. The performance of the fabricated MEA was better than that of the commercial one

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

    International Nuclear Information System (INIS)

    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

  10. 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.

  11. 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.

  12. Electrochemical fabrication of lanthanum-doped TiO2 nanotube array electrode and investigation of its photoelectrochemical capability

    International Nuclear Information System (INIS)

    Highlights: ► La-doped TiO2 nanotube array electrode was successfully fabricated by electrochemical method. ► The doped electrode showed high photoelectrocatalytic activity for degradation of PNP. ► Effective separation of photogenerated electron–hole pairs. -- Abstract: Highly ordered lanthanum-doped (La-doped) TiO2 nanotube arrays were prepared by electrochemical anodization process on a Ti sheet, followed by cathodic electrochemical process using lanthanum nitrate solution as the La source, and at last were analyzed by SEM, XPS, FTIR, XRD, and DRS characterization techniques. The analytical results demonstrated that the La doping could promoted phase transformation of TiO2 from the anatase to rutile. Red shifted and enhanced absorption intensities of certain peaks in both UV and visible light regions were also observed. Moreover, a new state of Ti3+ was founded after calcinations. The photoelectrochemical results indicated that La doping can significantly enhance the photoconversion efficiency of the TiO2 nanotube array electrode. The maximum photoconversion efficiency was 0.598%, which was obviously more than 2-fold higher than the undoped one (0.257%) under the same supporting electrolyte solution. The photoelectrocatalytic (PEC) degradation result of p-nitrophenol (PNP) was used to investigate the PEC activities of the as-prepared electrode. The La-doped TiO2 nanotube array electrode showed much higher degradation efficiencies (99.33%) than the undoped TiO2 nanotube array electrode (70.16%) under the same condition

  13. Investigation of polyaniline films doped with Fe3+ as the electrode material for electrochemical supercapacitors

    International Nuclear Information System (INIS)

    Highlights: • The PANI/Fe3+ films were synthesized by CV on stainless steel wire mesh. • The growth rate of PANI/Fe3+ films were greatly increased. • The PANI/Fe3+ films show a larger specific capacitance and lower resistance. • The relationship between electrochemical properties of a serious of transition metal ions doped PANI and the ratio of electronic affinity and ionic radius (Ea/r) has also been researched. - Abstract: H+ and Fe3+ ions co–doped polyaniline were synthesized by cyclic voltammetry onto the stainless steel mesh with various concentration of ferric chloride (FeCl3·6H2O) in electrolyte. The structure and morphology of PANI and PANI/Fe3+ films were characterized by Fourier transform infrared (FT–IR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) techniques. The electrochemical properties of PANI and PANI/Fe3+ films were investigated by cyclic voltammetry, galvanostatic charge–discharge test and electrochemical impedance spectroscopy (EIS) in 0.5 mol L−1 H2SO4 electrolyte in three–electrode system. The PANI/0.2 M Fe3+ film shows a larger specific capacitance of 602 F g−1 at a current density of 3 mA/cm2 and lower resistance compared with the pure PANI film. The relationship between electrochemical properties of a serious of transition metal ions doped PANI/Mn+ (Mn+ = Mn2+, Co2+, Ni2+, Cu2+, Zn2+ and Fe3+) films and the ratio of electronic affinity and ionic radius (Ea/r) has also been researched

  14. 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.

  15. 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.

  16. 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......,1,3-benzothiadiazole)] (PSiF-DBT) nanocomposite solar cells, which improves the fill factor compared to pure aluminum electrodes. A comprehensive structural investigation was performed by means of transmission electron microscopy and time-of-flight secondary ion mass spectrometry revealing the presence of silver...... 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....

  17. Electrochemical investigation of functionalized graphene aerogel with different amount of p-phenylenediamine as an advanced electrode material for supercapacitors

    Science.gov (United States)

    Gholipour-Ranjbar, Habib; Ganjali, Mohammad Reza; Norouzi, Parviz; Naderi, Hamid Reza

    2016-07-01

    Graphene aerogel has attracted great attention as a new and efficient electrode material for supercapacitors. It can be expected that functionalization of graphene aerogels can further improve their capability. In this study, graphene aerogel functionalized with different amount of p-phenylenediamine (PPD) and the effect of PPD amount on the supercapacitive performance of functionalized graphene aerogel (FGA) was investigated. Structural characterizations showed that PPD molecules initiated graphene aerogel sheets assembly into three-dimensional structures and also increasing PPD amount led to increase in surface area. Electrochemical investigations proved that the FGA with larger pore size showed enhanced supercapacitive performance compared with the FGA with smaller pore size. The optimized FGA-based electrode exhibited outstanding specific capacitance (SC) of 385 F g‑1 at a discharge current density of 1 A g‑1, good rate capability (215 F g‑1 at 20 A g‑1), and exceptionally high cyclic stability by displaying 25% increase in SC after 5000 cycle.

  18. EXPERIMENTAL INVESTIGATION OF ELECTRICAL DISCHARGE IN LIQUID INITIATED BETWEEN CONE CHANNEL ELECTRODES

    OpenAIRE

    A.V. Sakun; K.V. Korytchenko; Yuferov, V. B.; Ozerov, A. N.; Vinnikov, D. V.; A.P. Mesenko

    2013-01-01

    This paper delves into electrical discharge in liquid between cone channel electrodes as applied to a problem of cavity initiation with shock waves focusing. The velocity of the cavitation pocket directed motion has been determined. Curves of the liquid transparency variation at 650 nm wave length have been obtained. Low pressure influence on acoustic signals under shock waves focusing has been evaluated.

  19. INVESTIGATION OF SURFACING TECHNOLOGICAL OPPORTUNITIES BY THE INDIRECT THREE-PHASE ARC WITH CONSUMABLE ELECTRODES

    OpenAIRE

    Bezrukih, A.; Meister, R; Lubnin, M.; Gotovko, S.

    2010-01-01

    This paper is devoted to the high-effective process of surfacing by the indirect three-phase arc with covered electrodes. The share of the parent metal in the surfaced one does not exceed 10 % which is infeasible for one-arc surfacing.

  20. 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.

  1. 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.

  2. Investigation into peculiarities of the mercury-graphite electrode and discharge-ionization of mercury on graphite. Communication 4. Effect of mercury quantity deposited on the graphite electrode on metal oxidation currents

    International Nuclear Information System (INIS)

    Investigations of ionization process of mercury and cadmium electrodeposited simultaneously on the graphite electrode showed, that a boundary ration founded for some metals from Isub(maxMe)-Csub(Hg (II)) dependence (as indicated in literature) can not be objective parameter for characteristics of metal-mercury graphite electrode system. Boundary ratio calculated by the use of Isub(maxMe)-Qsub(Hg) or Qsub(Me)-Qsub(Hg) dependences remains constant and is independent on electrolyse conditions. After boundary ratio has been reached, analytical signal of determined element is independent on quantity of mercury on the electrode surface and metal concentration in mercury phase

  3. 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. PMID:27076373

  4. 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.

  5. Sol-gel derived carbon ceramic electrode for the investigation of the electrochemical behavior and electrocatalytic activity of neodymium hexacyanoferrate

    International Nuclear Information System (INIS)

    The electrochemical properties of an electroactive rare earth metal hexacyanoferrate, neodymium hexacyanoferrate (NdHCF) were studied by mechanically attaching NdHCF samples to the surface of carbon ceramic electrodes (CCEs) derived from sol-gel technique. The resulting modified electrodes exhibit well-defined redox responses with the formal potential of 0.241 V (versus SCE) at a scan rate of 20 mV s-1 in 0.5 M KCl solution. The voltammetric characteristics of the NdHCF-modified CCEs in the presence of different alkali metal cations (Li+, Na+, K+, Rb+ and Cs+) were investigated by voltammetry. The NdHCF-modified CCEs presented a good electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2), and was used for amperometric detection of H2O2. In addition, the NdHCF-CCEs exhibited a distinct advantage of simple preparation, surface renewal, good stability and reproducibility

  6. Photoelectrochemical investigation of methylene blue immobilised on zirconium phosphate modified carbon paste electrode in flow injection system

    International Nuclear Information System (INIS)

    The adsorption of methylene blue (MB) onto zirconium phosphate (ZrP) was studied and the adsorption capacity value and isotherms were determined. The adsorption capacity of ZrP was increased after being exposed to gas phase n-butyl amine. The adsorbed MB on ZrP was used as a modifier material in carbon paste electrode (MCPE), which in turn was used in voltammetric investigations and flow injection (FI) amperometric determination of ascorbic acid (AA). A quasi-reversible electrode reaction of adsorbed MB was exhibited. A home made flow-through electrochemical cell with a suitable transparent window for irradiation of the electrode surface was constructed and used for amperometric FI studies. The photoamperometric-FI conditions were optimised as 1.5 mL min-1 flow rate, a 25 cm transmission tubing length, a 100 μL injection volume, and a constant applied potential of +100 mV versus SCE. The calibration curve for AA was linear over the concentration range from 1.0 x 10-6 to 4.0 x 10-5 M. The relative standard deviation of four replicate injections of 3.0 x 10-5 M AA was 1.2%. The results obtained for AA determination in pharmaceutical products are in good agreement with those obtained using the procedure involving the reaction between triiodide and AA

  7. Investigation of high voltage discharges in low pressure gases through large ceramic superconducting electrodes

    OpenAIRE

    Podkletnov, Evgeny; Modanese, Giovanni

    2002-01-01

    A device has been built and tested, in which a ceramic superconducting cathode and a copper anode cause electrical discharges in low pressure gases, at temperatures between 50 and 70 K. The electrodes are connected to a capacitors array charged up to 2000 kV; peak currents are of the order of 10^4 A. The cathode has the diameter of 10 cm and is fabricated by OCMTG technology. In discharges at voltage above 500 kV two new phenomena were observed, probably related to each other. First, the disc...

  8. 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.

  9. In-situ x-ray investigation of hydrogen charging in thin film bimetallic electrodes

    International Nuclear Information System (INIS)

    Hydrogen uptake and discharge by thin metallic films under potentiostatic control was studied using x-ray diffraction at the National Synchrotron Light Source (NSLS). The formation of metal-hydrogen phases in Pd, Pd-capped Nb and Pd/Nb multilayer electrode structures was deduced from x-ray diffraction data and correlated with the cyclic voltammetry (CV) peaks. The x-ray data was also used to construct a plot of the hydrogen concentration as a function of cell potential for a multilayered thin film. copyright 1997 Materials Research Society

  10. Hybrid direct carbon fuel cell anode processes investigated using a 3-electrode half-cell setup

    DEFF Research Database (Denmark)

    Deleebeeck, Lisa; Arenillas, A.; Menendez, J.A.;

    2015-01-01

    anthracite and bituminous coals, as well as carbon black, were tested, revealing similar open circuit potential and activation energies in mixed 96-4vol% N2-CO2 and 50-50vol% CO-CO2 environments between 700 and 800°C. Bituminous coal showed the highest activity, likely associated to a high O/C ratio...... and hydrogen content. Based on acquired data, a reaction scheme was proposed for processes at the working electrode, including the role of bubble formation in the vicinity of the electrochemically active solid/molten medium interface....

  11. Investigation on the electrode process of the Mn(II)/Mn(III) couple in redox flow battery

    International Nuclear Information System (INIS)

    The Mn(II)/Mn(III) couple has been recognized as a potential anode for redox flow batteries to take the place of the V(IV)/V(V) in all-vanadium redox battery (VRB) and the Br2/Br- in sodium polysulfide/bromine (PSB) because it has higher standard electrode potential. In this study, the electrochemical behavior of the Mn(II)/Mn(III) couple on carbon felt and spectral pure graphite were investigated by cyclic voltammetry, steady polarization curve, electrochemical impedance spectroscopy, transient potential-step experiment, X-ray diffraction and charge-discharge experiments. Results show that the Mn(III) disproportionation reaction phenomena is obvious on the carbon felt electrode while it is weak on the graphite electrode owing to its fewer active sites. The reaction mechanism on carbon felt was discussed in detail. The reversibility of Mn(II)/Mn(III) is best when the sulfuric acid concentration is 5 M on the graphite electrode. Performance of a RFB employing Mn(II)/Mn(III) couple as anolyte active species and V(III)/V(II) as catholyte ones was evaluated with constant-current charge-discharge tests. The average columbic efficiency is 69.4% and the voltage efficiency is 90.4% at a current density of 20 mA cm-2. The whole energy efficiency is 62.7% close to that of the all-vanadium battery and the average discharge voltage is about 14% higher than that of an all-vanadium battery. The preliminary exploration shows that the Mn(II)/Mn(III) couple is electrochemically promising for redox flow battery

  12. Combined voltammetric and spectroscopic investigation of binding interaction between nifedipine and human serum albumin on polyelectrolyte modified ITO electrode

    International Nuclear Information System (INIS)

    Highlights: • The polyelectrolyte coated ITO surface was used as working electrode. • HSA was bounded onto modified electrode surface. • The interaction of nifedipine with HSA was studied. • Electrochemical and fluorescence techniques were used for characterization. -- Abstract: The binding interaction between the drug molecule, nifedipine (Nf), and the human serum albumin (HSA) on polyelectrolyte modified indium tin oxide (ITO) electrode has been investigated by the combination of electrochemical and fluorescence spectroscopy techniques. Surface modification has also been characterized by scanning electron microscopy (SEM) and Contact Angle (CA) measurements in each step. The cyclic voltammetry, electrochemical impedance parameters (peak potential difference (ΔEp)), peak current difference (ΔIp) and charge-transfer resistance (Rct) indicate that nifedipine strongly interacted with human serum albumin molecule on the polyelectrolyte modified ITO electrode surface. Stern–Volmer quenching constant Ka is inversely correlated with the temperature, which indicates that the probable quenching mechanism of the nifedipine-human serum albumin binding reaction is initiated by complex formation. The results obtained from these techniques showed that Nf could bind to HSA. The binding constant (Kb) and the number of binding sites (n) of the drug with HSA at different temperatures were determined. At 298 K, Kb was found as 4.04 × 10−3 and n was 1.08 for Nf-HSA. According to the van’t Hoff equation, the thermodynamic parameters, ΔG, ΔH and ΔS, were obtained, showing the involvement of hydrophobic and electrostatic force in this interaction

  13. Percolation modeling investigation of TPB formation in a solid oxide fuel cell electrode-electrolyte interface

    International Nuclear Information System (INIS)

    A Monte Carlo percolation model has been developed and utilized to characterize the factors controlling triple phase boundary (TPB) formation in an SOFC electrode. The model accounts for (1) electronic conductor, ionic conductor, and gas phase percolation, (2) competition between percolation of gas and electronically conducting phases, and (3) determination of continuous, though not necessarily fully percolating, paths from TPBs to the bulk phases. The model results show that physical processes near the TPB, such as sorbate transport, significantly affect TPB formation in a composite electrode. Active TPB formation is found to be most significantly dependent upon continuous and competing percolation of multiple phases. Simultaneously requiring continuous paths and accounting for non-continuous boundary conditions results in lower active TPB formation levels (up to 8% of possible sites) than presented in the literature (75% of possible sites). In addition, the varying ratio of active to potential TPB sites predicted by the current model (up to 80%) differs significantly from the constant reported in the literature (80%), which lacks analyses of three-phase percolation, gas phase paths, and gas/current collector boundary conditions. This dependence of active TPB formation on percolation of all three phases is important to understand as a basis for determining SOFC performance and optimization

  14. 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.

  15. Investigation of the electrochemical behavior of multilayers film assembled porphyrin/gold nanoparticles on gold electrode

    International Nuclear Information System (INIS)

    Multilayers film of nanostructured gold nanoparticles (AuNPs) has been fabricated based on the layer-by-layer (LBL) technique using a self-assembled monolayer of 5,15-di-[p-(6-mercaptohexyl)-phenyl]-10,20-diphenylporphyrin (trans-PPS2). AuNPs act as physical cross-link points in the multilayers. Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) are applied to study the formation of the organic-inorganic multilayers film and have determined the electrochemical parameters, i.e., the heterogeneous electron transfer rate constant (Ket). The observed phenomena indicate that the electron transfer (ET) process is affected by material properties and the molecular structure of self-assembled monolayers (SAMs). Using the high sensitivity of ET of ferricyanide to the modification of the gold surface with multilayers film, we select this reaction as a probe to study the different modification stages at this modified electrode. ET is retarded on the trans-PPS2 alternative deposition of layers on the electrode surface and is accelerated on the AuNPs' layers. SECM images are used to collect surface information in the course of the successive modification process. SECM images obtained from bare and different modification stages show very high resolution with different topographies.

  16. Investigation of the electrochemical behavior of multilayers film assembled porphyrin/gold nanoparticles on gold electrode

    Energy Technology Data Exchange (ETDEWEB)

    Lu Xiaoquan, E-mail: luxq@nwnu.edu.c [College of Chemistry and Chemical Engineering, Northwest Normal University, No. 967 Anning Eastern Road, Lanzhou, Gansu 730070 (China); Zhi Fupeng; Shang Hui; Wang Xiaoyan; Xue Zhonghua [College of Chemistry and Chemical Engineering, Northwest Normal University, No. 967 Anning Eastern Road, Lanzhou, Gansu 730070 (China)

    2010-04-15

    Multilayers film of nanostructured gold nanoparticles (AuNPs) has been fabricated based on the layer-by-layer (LBL) technique using a self-assembled monolayer of 5,15-di-[p-(6-mercaptohexyl)-phenyl]-10,20-diphenylporphyrin (trans-PPS{sub 2}). AuNPs act as physical cross-link points in the multilayers. Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) are applied to study the formation of the organic-inorganic multilayers film and have determined the electrochemical parameters, i.e., the heterogeneous electron transfer rate constant (K{sub et}). The observed phenomena indicate that the electron transfer (ET) process is affected by material properties and the molecular structure of self-assembled monolayers (SAMs). Using the high sensitivity of ET of ferricyanide to the modification of the gold surface with multilayers film, we select this reaction as a probe to study the different modification stages at this modified electrode. ET is retarded on the trans-PPS{sub 2} alternative deposition of layers on the electrode surface and is accelerated on the AuNPs' layers. SECM images are used to collect surface information in the course of the successive modification process. SECM images obtained from bare and different modification stages show very high resolution with different topographies.

  17. 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.

  18. 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.

  19. Electrochemical and spectroscopic investigations of immobilized de novo designed heme proteins on metal electrodes

    DEFF Research Database (Denmark)

    Albrecht, Tim; Li, WW; Ulstrup, Jens;

    2005-01-01

    On the basis of rational design principles, template-assisted four-helix-bundle proteins that include two histidines for coordinative binding of a heme were synthesized. Spectroscopic and thermodynamic characterization of the proteins in solution reveals the expected bis-histidine coordinated heme...... involves the coupling of electron transfer and heme ligand dissociation, which was analyzed by time-resolved SERR spectroscopy. Electron transfer was found to be significantly slower for the mono-histidine-coordinated than for the bis-histidine-coordinated heme. For the latter, the formal heterogeneous...... electron-transfer rate constant of 13 s(-1) is similar to those reported for natural heme proteins with comparable electron-transfer distances, which indicates that covalently bound synthetic heme proteins provide efficient electronic communication with a metal electrode as a prerequisite for potential...

  20. 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.

  1. Investigation of the porous nanostructured Cu/Ni/AuNi electrode for sodium borohydride electrooxidation

    International Nuclear Information System (INIS)

    An electrochemical approach to nanostructured Cu/Ni/AuNi catalyst design using the electrodeposition process followed by galvanic replacement technique is presented. The procedure consisted of the electrodeposition of Ni–Zn on the Ni coating with subsequent replacement of the zinc by gold at open circuit potential in a gold containing alkaline solution. The surface morphologies and compositions of coatings were determined by energy dispersive X-ray and scanning electron microscopy techniques. The results showed that the Cu/Ni/AuNi coatings were porous composing of discrete Au nanoparticles. The electrocatalytic activity of Cu/Ni/AuNi electrodes for sodium borohydride electro-oxidation was studied using cyclic voltammetry, chronoamperometry, chronopotentiometry and electrochemical impedance spectroscopy techniques. The electro-oxidation current on Cu/Ni/AuNi catalyst is much higher than that on flat Au catalyst. The onset potential and peak potential on Cu/Ni/AuNi catalysts are more negative than that on flat Au catalyst for borohydride electrooxidation. The impedance behavior also shows different patterns, capacitive, and negative resistances and inductive loops at different applied anodic potentials. All results show that the Cu/Ni/AuNi catalysts can be applied as potential anode catalysts for the direct borohydride fuel cells

  2. 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; Thydén, Karl Tor Sune; Kiebach, Wolff-Ragnar; Küngas, Rainer

    stabilised zirconia (YSZ) backbone air electrode and Ni/YSZ cermet fuel electrode. The SOC was tested at electrolysis conditions under high current (up to -1 A/cm2). The porous YSZ electrodes was infiltrated with gadolinium-doped ceria oxide (CGO), to act as a barrier layer between the catalyst and the...

  3. Ascorbic Acid Rejection Characteristics of Modified Platinum Electrodes: A Shelf Life Investigation

    OpenAIRE

    Andrea M. Wynne; Finnerty, Niall J.

    2015-01-01

    Ascorbic acid (AA) is the principle interferent present in brain extracellular fluid that can inhibit the ability of electrochemical sensors to selectively detect a particular analyte of interest. Considerable efforts have been made in recent times to develop highly selective membrane coatings to counteract the drawbacks associated with AA interference during in vivo monitoring. The primary objective of the work described within was to investigate the long term effect of storing such selecti...

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

    OpenAIRE

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

    2012-01-01

    Linac4 accelerator of Centre Européen de Recherches Nucléaires is under construction and a RFdriven H− 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 sourc...

  5. Operando X-ray Investigation of Electrode/Electrolyte Interfaces in Model Solid Oxide Fuel Cells

    OpenAIRE

    Volkov, Sergey; Vonk, Vedran; Khorshidi, Navid; Franz, Dirk; Kubicek, Markus; Kilic, Volkan; Felici, Roberto; Huber, Tobias M.; Navickas, Edvinas; Rupp, Ghislain M.; Fleig, Jürgen; Stierle, Andreas

    2016-01-01

    We employed operando anomalous surface X-ray diffraction to investigate the buried interface between the cathode and the electrolyte of a model solid oxide fuel cell with atomic resolution. The cell was studied under different oxygen pressures at elevated temperatures and polarizations by external potential control. Making use of anomalous X-ray diffraction effects at the Y and Zr K-edges allowed us to resolve the interfacial structure and chemical composition of a (100)-oriented, 9.5 mol % y...

  6. Investigation of the oxygen reduction activity on Silver – a rotating disk electrode study

    OpenAIRE

    Wiberg, Gustav K. H.; Mayrhofer, Karl J.J.; Arenz, Matthias

    2010-01-01

    Abstract 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 electrochem...

  7. In operando Raman spectroscopy as a tool for investigation of solid oxide electrodes

    DEFF Research Database (Denmark)

    Traulsen, Marie Lund; Holtappels, Peter; Walker, Robert

    polarisation. Conventionally, the solid oxide electrodes have been studied by electrochemical techniques during operation, and then analyzed post-mortem using electron microscopy, elemental analyses etc. However, accurate interpretation of the electrochemical response from the electrodes requires careful in......Solid oxide electrodes are important in a number of technologies including solid oxide fuel cells, solid oxide electrolysis cells, gas sensors and electrochemical gas purification. The electrodes operate at elevated temperatures (300-900 °C), while they are subjected to gas flow and electrical...

  8. Investigation of charge sharing among electrode strips for a CdZnTe detector

    International Nuclear Information System (INIS)

    We have investigated charge sharing among the anode strips of a CdZnTe (CZT) detector using a 30 μm collimated gamma-ray beam. We compared the laboratory measurements with the predictions from our modeling of the charge transport within the detector. The results indicate that charge sharing is a function of the interaction depth and the energy of the incoming photon. Also, depending on depth, a fraction of the electrons might drift to the inter-anode region causing incomplete charge collection. Here, we show that photoelectron range and diffusion of the charge cloud are the principal causes of charge sharing and obtain limits on the size of the electron cloud as a function of position in the detector

  9. Fabrication of La-doped TiO2 Film Electrode and investigation of its electrocatalytic activity for furfural reduction

    International Nuclear Information System (INIS)

    Lanthanum trivalent ions (La3+) doped nano-TiO2 film electrode was prepared by the sol–gel method. The prepared electrode was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The electrocatalytic properties of the roughened TiO2 film electrode towards the electrocatalytic reduction of furfural to furfural alcohol were evaluated by CV and preparative electrolysis experiments. The results of the optimum molar ratio of La: Ti was 0.005:1. Experimental evidence was presented that the La nano-TiO2 electrode exhibited higher electrocatalytic activity for the reduction of furfural than the undoped nano-TiO2 electrode in N,N-dimethylformamide medium. Bulk electrolysis studies were also carried out for the reduction of furfural and the product was confirmed by NMR

  10. 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.).

  11. Variability of electrode positions using electrode caps.

    Science.gov (United States)

    Atcherson, Samuel R; Gould, Herbert Jay; Pousson, Monique A; Prout, Tina M

    2007-01-01

    We investigated the variability of electrode positions for a multi-channel, custom electrode cap placed onto participants' heads without taking scalp measurements. The electrode positions were digitized in a three-dimensional space for 10 young adult participants on three separate occasions. Positional variability was determined for 15 selected electrodes within the three-dimensional preauricular-nasion (PAN) coordinate system and from this system, angular coordinate variability was also determined. The standard deviations of the 15 selected electrodes ranged from 3.0 to 12.7 mm in the PAN system. These data resulted in a variability of 2.0 degrees to 10.4 degrees among the angular coordinates. The measurements indicated slightly greater variability of electrode positions compared to studies when electrodes were placed using scalp measurements. The implication of this study is that the use of electrode caps may not be appropriate when electroencephalographic (EEG) or evoked potential (EP) techniques depend on accurate electrode placement. Additionally, if a longitudinal study is performed, electrode locations should be checked to ensure that they conform with previous sessions. PMID:17929157

  12. 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.

  13. Preparation of CuInS2/TiO2 nanotube heterojunction arrays electrode and investigation of its photoelectrochemical properties

    International Nuclear Information System (INIS)

    Graphical abstract: Schematic illustration of the synthesis steps of CuInS2/TiO2 heterojunction arrays electrode. - Highlights: • CuInS2/TiO2 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: CuInS2/TiO2 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 CuInS2/TiO2 NTs electrode were observed under visible light irradiation, which could be attributed to the high absorption coefficient of CuInS2 in visible region and the heterostructure formed between CuInS2 and TiO2

  14. 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}.

  15. 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

    its high theoretical capacity (220 mA h g-1) LiFeBO3 is a promising cathode material for lithium ion batteries. However, its application is limited because of significant degradation due to surface reactions upon exposure to moisture and air. Therefore, detailed compositional characterization of Li......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 interface...... transport processes, the presented combinatorial approach is a very valuable tool in characterizing battery electrodes and their interfaces. We apply this technique to lithium iron borate (LiFeBO3) battery electrodes at different cycling conditions to study the surface and interface layer evolution. Due to...

  16. Investigations of proton conducting polymers and gas diffusion electrodes in the polymer electrolyte fuel cell

    OpenAIRE

    Gode, Peter

    2005-01-01

    Polymer electrolyte fuel cells (PEFC) convert the chemically bound energy in a fuel, e.g. hydrogen, directly into electricity by an electrochemical process. Examples of future applications are energy conversion such as combined heat and power generation (CHP), zero emission vehicles (ZEV) and consumer electronics. One of the key components in the PEFC is the membrane / electrode assembly (MEA). Both the membrane and the electrodes consist of proton conducting polymers (ionomers). In the membr...

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

    OpenAIRE

    M. Hafiz Helmi; M. Azuddin; W. Abdullah

    2009-01-01

    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 ro...

  18. Electric investigation of a photo-electrochemical water splitting device based on a proton exchange membrane within drilled FTO-covered quartz electrodes: under dark and light conditions

    International Nuclear Information System (INIS)

    I-V characteristics of a photo-electrochemical (PEC) water splitting device based on a proton exchange membrane with fluorine doped tin oxide (FTO) covered quartz drilled electrodes were investigated. A nanostructured TiO2 film has been used as the anodic photo-catalyst and a supported Pt thin film has been employed as the cathodic electro-catalyst. To interpret the experimental electric data in the cell, in both dark and sunlight conditions (air mass, AM 1.5 G, 100 mW/cm2), appropriate descriptions have been used for each electrode. The cathode was modelled in terms of the Butler-Volmer approach and for the anode a semiconductor diode equation was used. Taking into account the experimental evidence that the oxygen evolving electrode overpotential in the working cell is rather large respect to the cathode (at least one order of magnitude), an approximated expression for the current is proposed. The influence on I-V of the covering of the electrode by atomic and molecular oxygen is estimated, in the linear limit, and the important role of the bubble covering factor in the behavior of the device is discussed. A model for the AC response of the cell to an external AC stimulus of small amplitude, based on a generalization of the Poisson-Nernst-Planck model with linear boundary conditions is also developed and used to interpret the electrochemical impedance spectroscopy (EIS) measurements on the PEC device allowing the determination of the two transfer coefficients at the electrodes and their dependence on the applied bias for both dark and sunlight conditions. The developed models provide useful tools to determine and compare important parameters affecting the photo-catalytic and electro-catalytic performance of the electrodes and the final efficiency of the PEM photo-electrolyzer

  19. Investigation of nanosecond pulsed dielectric barrier discharge using plate-to-plate electrode with asymmetric dielectric arrangement in airflow

    Science.gov (United States)

    Qi, Haicheng; Fan, Zhihui; Liu, Yidi; Ren, Chunsheng

    2016-05-01

    Atmospheric pressure dielectric barrier discharge plasma is produced in airflow by applying nanosecond high voltage pulses with peak voltage about 35 kV and rising time about 40 ns on a plate-to-plate electrode arrangement. The effects of airflow rate (0-50 m/s) on the discharge characteristics are investigated under different barrier conditions (the bare anode case and the bare cathode case). For both cases, the breakdown voltage and the time lag increase distinctly and the discharge intensity decreases sharply when the airflow rate increases from 0 to 30 m/s, and then keep almost constant until the airflow rate is further increased to 50 m/s. For the bare anode case (the cathode is covered by dielectric plate), the discharge mode transforms gradually from filamentary to diffuse discharge with the increasing airflow rate. While for the bare cathode case, some micro-discharge channels are still excited, though the discharge becomes more diffuse when the airflow rate is higher than 30 m/s. By acquiring the time-resolved images of the discharge, it is proved that it is the primary discharge which becomes diffuse when airflow is introduced and the following two discharges of the same voltage pulse occur principally at the positions where the primary discharge is more intense. And in both cases, the plasma temperatures are reduced, but the degree is different. All the phenomena can be explained mainly by the variation of the space charge distribution when the airflow is introduced into the discharge gap. And it is indicated that the bare anode case has an advantage in obtaining diffuse discharge.

  20. Investigation of Ir-modified carbon felt as the positive electrode of an all-vanadium redox flow battery

    International Nuclear Information System (INIS)

    Porous graphite felts have been used as electrode materials for all-vanadium redox flow batteries due to their wide operating potential range, stability as both an anode and a cathode, and availability in high surface area. In this paper, the carbon felt was modified by pyrolysis of Ir reduced from H2IrCl6. ac impedance and steady-state polarization measurements showed that the Ir-modified materials have improved activity and lowered overpotential of the desired V(IV)/V(V) redox process. Ir-modification of carbon felt enhanced the electro-conductivity of electrode materials. The Ir-material, when coated on the graphite felt electrode surface, lowered the cell internal resistance. A test cell was assembled with the Ir-modified carbon felt as the activation layer of the positive electrode, the unmodified raw felt as the activation layer of the negative electrode. At an operating current density of 20 mA cm-2, a voltage efficiency of 87.5% was achieved. The resistance of the cell using Ir-modified felt decreased 25% compared to the cell using non-modified felt

  1. 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.

  2. Investigation of novel electrode materials for electrochemically based remediation of high and low-level mixed wastes in the DOE complex. 1997 annual progress report

    International Nuclear Information System (INIS)

    'This work is focused on the preparation of novel electrode materials for the degradation of toxic wastes in the DOE complex. One of the goals of this work is to characterize whether it is possible to use controlled doping of TiO2 with species such as Nb in order to create new electrode materials that will facilitate the destruction of undesirable organics and inorganics, without light and instead only with an applied potential, in the waste tanks at the DOE sites. In the first part of this project, the authors have therefore spent an extensive amount of effort characterizing, as a baseline, the chemical and electrochemical behavior of TiO2 itself, so that they can make robust comparisons to the behavior of the Nb-doped systems in subsequent work on this project. The preparation of these electrode films is being performed by Marc Anderson at Wisconsin, who is preparing a number of different stoichiometries, grain sizes, etc. for investigation of their electrochemical properties by the Lewis group at Caltech. First they report on the progress of the electrode preparation work, and then they describe progress on the electrochemical work.'

  3. Investigation of the electroactive capability for the supercapacitor electrode with cobalt oxide rhombus nanopillar and nanobrush arrays

    Science.gov (United States)

    Liu, Yu-Bin; Lin, Lu-Yin; Huang, Ying-Yu; Tu, Chao-Chi

    2016-05-01

    Well-defined nanostructures of the cobalt oxide are designed intensively to pursue large surface area and high conductivity as the electroactive material for supercapacitors (SCs). Instead of merely fabricating effective electroactive materials, two kinds of the cobalt oxide nanostructures synthesized directly on nickel foam to achieve good contact between the material and the substrate are compared to clarify the growth mechanism and the structure-dependent SC performance. The nanobrushes are completely composed of nanoparticles while the rhombus nanopillars present integrated structure by the recrystallization of single nanopillars. A higher specific capacitance (CF) of 509 F/g is obtained for the SC electrode with CoO rhombus nanopillar array at a scan rate of 10 mV/s, comparing to that of 169 F/g for the CoO nanobrush array-based SC electrode, due to the larger electroactive surface area and less recombination sites for the former case. The CF value is enhanced by 38% as compared with the initial value after 3000 cycles of repeated charge/discharge process for the CoO rhombus nanopillar array-based SC electrode due to the activation of the material. The results provide a blue print for achieving highly efficient SC electrode by carefully designing the well-established electroactive material to attain facile and long-lasting faradic reactions.

  4. Investigations of poly(pyrrole)-coated cotton fabrics prepared in blends of anionic and cationic surfactants as flexible electrode

    International Nuclear Information System (INIS)

    Highlights: • Poly(pyrrole)-coated cotton fabrics were prepared in mixed surfactants. • The fabrics are soft, lightweight, mechanically robust, and highly electrical conductive. • Potential applications of the fabrics as flexible electrodes were tested. • The fabric electrodes exhibited high discharge capacity and excellent cycling performance. -- Abstract: In recent years, much effort has been dedicated to achieve lightweight, stretchable and flexible energy-storage devices for wearable electronics. Here we report an everyday cotton fabric coated with poly(pyrrole) as flexible electrodes. Poly(pyrrole) nanoparticles are synthesized on the fabrics via a simple chemical polymerization process with the mixed surfactants of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl benzene sulfonate (SDBS) as soft template. A highly conductive fabric with surface resistance of 14 Ω/□ can be produced by changing surfactant concentration. Such a conductive textile shows outstanding flexibility and stretchability, and demonstrates strong adhesion between the PPy and the cellulose fiber. The fabric electrode exhibits a discharge capacity of 51.7 mAh g−1 with high cycling stability (negligible decay after 100 cycles)

  5. Investigation of Novel Electrode Materials for Electrochemically-Based Remediation of High- and Low-Level Mixed Wastes in the DOE Complex - Final Report

    International Nuclear Information System (INIS)

    New materials are investigated, based on degenerately-doped titanias, for use in the electrochemical degradation of organics and nitrogen-containing compounds in sites of concern to the DOE remediation effort. The data collected in this project appear to provide a rational approach for design of more efficient nanoporous electrodes. Also, osmium complexes appear to be promising candidates for further optimization in operating photo electrochemical cells for solar energy conversion applications

  6. Investigation of Novel Electrode Materials for Electrochemically-Based Remediation of High- and Low-Level Mixed Wastes in the DOE Complex - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, N.S.; Anderson, M.

    2000-12-01

    New materials are investigated, based on degenerately-doped titanias, for use in the electrochemical degradation of organics and nitrogen-containing compounds in sites of concern to the DOE remediation effort. The data collected in this project appear to provide a rational approach for design of more efficient nanoporous electrodes. Also, osmium complexes appear to be promising candidates for further optimization in operating photo electrochemical cells for solar energy conversion applications.

  7. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Alimardani, Nasir; Tan, Cheng; Lampert, Benjamin P.; Conley, John F., E-mail: jconley@eecs.oregonstate.edu [School of Electrical Engineering and Computer Science, Oregon State University, Corvallis, Oregon 97331 (United States); King, Sean W. [Logic Technology Development, Intel Corporation, Hillsboro, Oregon 97124 (United States); French, Benjamin L. [Ocotillo Materials Laboratory, Intel Corporation, Chandler, Arizona 85248 (United States)

    2014-07-14

    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. Nb{sub 2}O{sub 5}, Ta{sub 2}O{sub 5}, ZrO{sub 2}, HfO{sub 2}, Al{sub 2}O{sub 3}, and SiO{sub 2} amorphous insulators are deposited via atomic layer deposition (ALD). Reflection electron energy loss spectroscopy (REELS) is utilized to measure the band-gap energy (E{sub G}) and energy position of intrinsic sub-gap defect states for each insulator. E{sub G} of as-deposited ALD insulators are found to be Nb{sub 2}O{sub 5} = 3.8 eV, Ta{sub 2}O{sub 5} = 4.4 eV, ZrO{sub 2} = 5.4 eV, HfO{sub 2} = 5.6 eV, Al{sub 2}O{sub 3} = 6.4 eV, and SiO{sub 2} = 8.8 eV with uncertainty of ±0.2 eV. Current vs. voltage asymmetry, non-linearity, turn-on voltage, and dominant conduction mechanisms are compared. Al{sub 2}O{sub 3} and SiO{sub 2} are found to operate based on Fowler-Nordheim tunneling. Al{sub 2}O{sub 3} shows the highest asymmetry. ZrO{sub 2}, Nb{sub 2}O{sub 5}, and Ta{sub 2}O{sub 5} 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 HfO{sub 2}, 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.

  9. 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)

    Sebastian Donner

    2007-12-01

    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

  10. Investigation of a Branchlike MoO(3)/polypyrrole hybrid with enhanced electrochemical performance used as an electrode in supercapacitors.

    Science.gov (United States)

    Zhang, Xia; Zeng, Xianzhong; Yang, Min; Qi, Yanxing

    2014-01-22

    A branchlike MoO3/polypyrrole conductive nanocomposite was facilely prepared by wrapping a homogeneous polypyrrole (PPy) layer around MoO3 nanobelts via the in situ oxidative polymerization of a self-assembled pyrrole monomer. X-ray powder diffraction characterization demonstrated that the PPy polymer does not hinder the crystallization of the MoO3 nanobelts substrate. The electrochemical tests show that the specific capacitance of 129 F g(-1) for the MoO3/PPy hybrid is higher than both pristine MoO3 and pure PPy. Moreover, the hybrid electrode with good electrical conductivity displays good cyclic stability of 90% retention after 200 cycles of charge/discharge. These results indicate a promising potential application of the MoO3/PPy nanocomposite for use as an effective electrode material in supercapacitors. PMID:24367933

  11. Bifunctional alkaline oxygen electrodes

    Science.gov (United States)

    Swette, L.; Kackley, N.; Mccatty, S. A.

    1991-01-01

    The authors describe the identification and testing of electrocatalysts and supports for the positive electrode of moderate-temperature, single-unit, rechargeable alkaline fuel cells. Recent work on Na(x)Pt3O4, a potential bifunctional catalyst, is described, as well as the application of novel approaches to the development of more efficient bifunctional electrode structures. The three dual-character electrodes considered here showed similar superior performance; the Pt/RhO2 and Rh/RhO2 electrodes showed slightly better performance than the Pt/IrO2 electrode. It is concluded that Na(x)Pt3O4 continues to be a promising bifunctional oxygen electrode catalyst but requires further investigation and development.

  12. 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...

  13. 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.

  14. Investigation of the Antioxidant Properties of Metallothionein in Transgenic Tobacco Plants using Voltammetry at a Carbon Paste Electrode

    Czech Academy of Sciences Publication Activity Database

    Shetivska, V.; Adam, V.; Prášek, J.; Macek, Tomáš; Macková, M.; Havel, L.; Dioplan, V.; Zehnálek, J.; Hubálek, J.; Kižek, R.

    2011-01-01

    Roč. 6, č. 7 (2011), s. 2869-2883. ISSN 1452-3981 Grant ostatní: GA ČR(CZ) GA522/07/0692; GA ČR(CZ) GA102/08/1546 Institutional research plan: CEZ:AV0Z40550506 Keywords : square wave voltammetry * carbon paste electrode * DNA * metallothionein Subject RIV: CG - Electrochemistry Impact factor: 3.729, year: 2011

  15. 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.

  16. Synthesis and characterization of novel dopamine-derivative:Application of modified multi-wall carbon nanotubes paste electrode for electrochemical investigation

    Institute of Scientific and Technical Information of China (English)

    Shadpour Mallakpour; Mehdi Hatami; Ali A. Ensafi; Hassan Karimi-Maleh

    2011-01-01

    Novel dopamine-derivative compound, 3,5-diamino-N-(3,4-dihydroxyphenethyl)benzamide (3,5-DAB) was prepared in two steps. In the first step dopamine hydrochloride was reacted with 3,5-dinitrobenzoyl chloride in the presence of propylene oxide. In the second step reduction of nitro groups resulted in preparation of 3,5-DAB in quantitative yield. This material was characterized using conventional spectroscopic methods such as FT-IR and 1H NMR. In addition, the redox response of a modified carbon nanotubes paste electrode of 3,5-DAB was investigated in aqueous solution at a neutral pH. The result showed that the electrode process has a guasi-reversible response, with △Ep, greater than the (59/n) mV expected for a reversible system. Finally, the diffusion coefficient for redox process in paraffin oil matrix obtained using chronoamperometry methods.

  17. In situ57Fe Moessbauer Investigation of Solid-State Redox Reactions of Lithium Insertion Electrodes for Advanced Batteries

    International Nuclear Information System (INIS)

    A novel in situ electrochemical cell for 57Fe Moessbauer measurements was developed in order to clarify the mechanisms of solid-state redox reactions in lithium insertion materials containing iron. Our in situ Moessbauer technique was successfully applied to the determination as to which transition metal ion was a redox center in the insertion electrodes, such as LiFe0.5Mn1.5O4, LiFeTiO4, or LiFe0.25Ni0.75O2, for the lithium-ion batteries.

  18. 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.

  19. Investigation the Efficiency of Electrolysis Process using 3 Dimensional Graphite Electrodes for Decolonization of Phenolphthalein and Phenol red from Aqueous Environments

    Directory of Open Access Journals (Sweden)

    Mohmmad Reza Massoudinejad

    2012-10-01

    Full Text Available Background and Objectives: The presence of chemical dyes in the water resources not only pollutes them, but also brings about death of organisms and serious indemnities to the environment through stopping oxygen production and preventing penetration of the sunlight. In this study, we investigated the efficiency of the electrolysis process for decolonization of phenolphthalein and phenol red from aqueous environment. Materials and Methods: The experiments were conducted in an electrochemical reactor having a working volume of 1 liter equipped with 2 graphite electrodes. This study was conducted at laboratory scale. Samples were prepared by dissolving two phenol red and phenolphthalein dyes in drinking water. Then, the effect of operating parameters such as voltage, inter-electrode distance, and NaCl concentration on the complete dye removal was determined considering optimum retention time using  Factorial variance analyses and the graphs were plotted using MS Excel software.Results: the results showed that the optimum conditions for completely removal of phenolphthalein was achieved applying a voltage of 48 V, the retention time of 9 minutes, 5 cm inter-electrode distance, and the salt concentration of 1.5 g/l, whereas, complete removal of phenol red was achieved applying a voltage of 48 V, the retention time of 8 minutes, 5 cm inter-electrode distance, and the salt concentration of 2 g/l. Under these conditions, COD removal efficiency for phenol red and phenolphthalein was 85 and 80 percent respectively.Conclusion: This study revealed that electrolysis process is an effective method to remove both phenolphthalein and phenol red dyes from effluent, because it can completely remove the dyes in a short time.

  20. Surface functionality and electrochemical investigations of a graphitic electrode as a candidate for alkaline energy conversion and storage devices

    Science.gov (United States)

    Soliman, Ahmed B.; Abdel-Samad, Hesham S.; Abdel Rehim, Sayed S.; Hassan, Hamdy H.

    2016-02-01

    Graphite is a typical electrocatalyst support in alkaline energy conversion and storage devices such as fuel cells, supercapacitores and lithium ion batteries. The electrochemical behaviour of a graphite electrode in 0.5 M NaOH was studied to elucidate its surface structure/electrochemical activity relationship. Graphite voltammograms are characterized by an anodic shoulder AI and a cathodic peak CI in addition to the oxygen reduction reaction plateaus, PI and PII. AI and CI were attributed to oxidation and reduction of some graphite surface function groups, respectively. Rotating ring disk electrode (RRDE) study revealed two different oxygen types assigned as inner and outer oxygen. The inner oxygen was reduced via the more efficient 4-electron pathway. The outer oxygen reduction proceeded with a lower efficient 2-electron pathway. The calculated percentages of the 4-electron pathway were ranged from 70% to 90%. A full mechanism for the graphite surface function groups changes over the studied potential window was suggested through the combination between the voltammetric, FT-IR and Raman results.

  1. Electron microscopy investigations of changes in morphology and conductivity of LiFePO4/C electrodes

    Science.gov (United States)

    Scipioni, Roberto; Jørgensen, Peter S.; Ngo, Duc-The; Simonsen, Søren B.; Liu, Zhao; Yakal-Kremski, Kyle J.; Wang, Hongqian; Hjelm, Johan; Norby, Poul; Barnett, Scott A.; Jensen, Søren H.

    2016-03-01

    In this work we study the structural degradation of a laboratory Li-ion battery LiFePO4/Carbon Black (LFP/CB) cathode by various electron microscopy techniques including low kV Focused Ion Beam (FIB)/Scanning Electron Microscopy (SEM) 3D tomography. Several changes are observed in FIB/SEM images of fresh and degraded cathodes, including cracks in the LFP particles, secondary disconnected particles, and agglomeration of CB. Low voltage (1 kV) SEM images show that the CB agglomerates have a different brightness than the fresh CB, due to charging effects. This suggests that the electronic conductivity of the CB agglomerates is low compared to that of the fresh CB particles. HRTEM analysis shows that fresh CB particles are quasi crystalline, whereas the LFP/CB interface in the degraded electrode shows amorphous carbon surrounding the LFP particles. The presence of the amorphous carbon is known to impede the electronic conductivity and thereby decreasing percolation in the cathode and reducing the electrode capacity.

  2. Numerical Investigation of Influence of Electrode Immersion Depth on Heat Transfer and Fluid Flow in Electroslag Remelting Process

    Science.gov (United States)

    Wang, Qiang; Cai, Hui; Pan, Liping; He, Zhu; Liu, Shuang; Li, Baokuan

    2016-07-01

    The influence of the electrode immersion depth on the electromagnetic, flow and temperature fields, as well as the solidification progress in an electroslag remelting furnace have been studied by a transient three-dimensional coupled mathematical model. Maxwell's equations were solved by the electrical potential approach. The Lorentz force and Joule heating were added into the momentum and energy conservation equations as a source term, respectively, and were updated at each time step. The volume of fluid method was invoked to track the motion of the metal droplet and slag-metal interface. The solidification was modeled by an enthalpy-porosity formulation. An experiment was carried out to validate the model. The total amount of Joule heating decreases from 2.13 × 105 W to 1.86 × 105 W when the electrode immersion depth increases from 0.01 m to 0.03 m. The variation law of the slag temperature is different from that of the Joule heating. The volume average temperature rises from 1856 K to 1880 K when the immersion depth increases from 0.01 m to 0.02 m, and then drops to 1869 K if the immersion depth continuously increases to 0.03 m. As a result, the deepest metal pool, which is around 0.03 m, is formed when the immersion depth is 0.02 m.

  3. Working Electrodes

    Science.gov (United States)

    Komorsky-Lovrić, Šebojka

    In electrochemistry an electrode is an electronic conductor in contact with an ionic conductor. The electronic conductor can be a metal, or a semiconductor, or a mixed electronic and ionic conductor. The ionic conductor is usually an electrolyte solution; however, solid electrolytes and ionic melts can be used as well. The term "electrode" is also used in a technical sense, meaning the electronic conductor only. If not specified otherwise, this meaning of the term "electrode" is the subject of the present chapter. In the simplest case the electrode is a metallic conductor immersed in an electrolyte solution. At the surface of the electrode, dissolved electroactive ions change their charges by exchanging one or more electrons with the conductor. In this electrochemical reaction both the reduced and oxidized ions remain in solution, while the conductor is chemically inert and serves only as a source and sink of electrons. The technical term "electrode" usually also includes all mechanical parts supporting the conductor (e.g., a rotating disk electrode or a static mercury drop electrode). Furthermore, it includes all chemical and physical modifications of the conductor, or its surface (e.g., a mercury film electrode, an enzyme electrode, and a carbon paste electrode). However, this term does not cover the electrolyte solution and the ionic part of a double layer at the electrode/solution interface. Ion-selective electrodes, which are used in potentiometry, will not be considered in this chapter. Theoretical and practical aspects of electrodes are covered in various books and reviews [1-9].

  4. 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

  5. Experimental investigation of bracket electrodes protruding into flow in the channel of a self-excited pulsed MHD generator of the Pamir type

    International Nuclear Information System (INIS)

    The results of the experimental study on the Faraday type pulsed MHD generator with discrete wire bracket electrodes, protruding into the flow are presented. The process of self-excitation proceeds more intensively as compared to normal plane uniform electrodes. By the MHD interaction maximum parameters the sharp perturbation of the parameters in the channel with discrete bracket electrodes and plane uniform electrodes, wherein the boundary layers state is essentially different, occurs practically by similar parameters of the MHD interaction, which testifies to the determining effect of voluminous electrodynamic forces on these processes

  6. Experimental investigation of discrete electrodes extending into the flow in the channel of the self-excited pulsed MHD generator of the Ural and Khibiny types

    International Nuclear Information System (INIS)

    Paper presents the results of experimental study of various configuration electrodes in the channel of powerful self-excited pulsed MHD-generator. Self-excitation process is shown to be more intensive with electrodes-champs extending into the flow. At maximal parameters of MHD-interaction the parameters in the channel with discrete electrodes-champs and with plane solid electrodes near which the state of interface layers differs essentially are abruptly disturbed under practically similar parameters of MHD-interaction slowing the governing effect of three-dimensional electrodynamic forces on these processes

  7. Theoretical investigation for Li2CuSb as multifunctional materials: Electrode for high capacity rechargeable batteries and novel materials for second harmonic generation

    International Nuclear Information System (INIS)

    Highlights: → We predict that Li2CuSb should be good electrode materials for high capacity rechargeable batteries and novel materials for SHG. → We found that intercalation of lithium leads to phase transitions, which agrees well with the experiment. → Intercalation of Li leads to increase the conductivity and break the symmetry along optical axis make the material useful for SHG application. → The microscopic second order hyperpolarizability, the vector component along the dipole moment direction is about 31.01x10-30 esu. - Abstract: Based on the first-principles electronic structure calculations, we predict that Li2CuSb should be good electrode materials for high capacity rechargeable batteries and novel materials for second harmonic generation. This prediction is based on the experimental measurements of Fransson et al. , and as step forward to do deep investigation on these materials we addressed ourselves for performing theoretical calculation. We found that intercalation of lithium leads to phase transitions, which agrees well with the experiment, increasing the conductivity of the material, and break the symmetry along the optical axis making the material useful for second harmonic generation (SHG) applications. We should emphasize that lithiated compound show very high second order optical susceptibility. We present the total charge densities in the (1 1 0) and (1 0 0) planes for the parent and lithiated phases and it was found that the parent compound shows a considerable anisotropy between the two planes in consistence with our calculated optical properties. We found that Li2CuSb possesses high second harmonic generation and its second order optical susceptibility of the total absolute value at zero frequency is equal to 142 pm/V. Based on the value of the second order optical susceptibility the microscopic second order hyperpolarizability, βijk, the vector component along the dipole moment direction is about 31.01 x 10-30 esu.

  8. An in-situ gas chromatography investigation into the suppression of oxygen gas evolution by coated amorphous cobalt-phosphate nanoparticles on oxide electrode

    Science.gov (United States)

    Gim, Jihyeon; Song, Jinju; Kim, Sungjin; Jo, Jeonggeun; Kim, Seokhun; Yoon, Jaegu; Kim, Donghan; Hong, Suk-Gi; Park, Jin-Hwan; Mathew, Vinod; Han, Junhee; Song, Sun-Ju; Kim, Jaekook

    2016-03-01

    The real time detection of quantitative oxygen release from the cathode is performed by in-situ Gas Chromatography as a tool to not only determine the amount of oxygen release from a lithium-ion cell but also to address the safety concerns. This in-situ gas chromatography technique monitoring the gas evolution during electrochemical reaction presents opportunities to clearly understand the effect of surface modification and predict on the cathode stability. The oxide cathode, 0.5Li2MnO3•0.5LiNi0.4Co0.2Mn0.4O2, surface modified by amorphous cobalt-phosphate nanoparticles (a-CoPO4) is prepared by a simple co-precipitation reaction followed by a mild heat treatment. The presence of a 40 nm thick a-CoPO4 coating layer wrapping the oxide powders is confirmed by electron microscopy. The electrochemical measurements reveal that the a-CoPO4 coated overlithiated layered oxide cathode shows better performances than the pristine counterpart. The enhanced performance of the surface modified oxide is attributed to the uniformly coated Co-P-O layer facilitating the suppression of O2 evolution and offering potential lithium host sites. Further, the formation of a stable SEI layer protecting electrolyte decomposition also contributes to enhanced stabilities with lesser voltage decay. The in-situ gas chromatography technique to study electrode safety offers opportunities to investigate the safety issues of a variety of nanostructured electrodes.

  9. An in-situ gas chromatography investigation into the suppression of oxygen gas evolution by coated amorphous cobalt-phosphate nanoparticles on oxide electrode.

    Science.gov (United States)

    Gim, Jihyeon; Song, Jinju; Kim, Sungjin; Jo, Jeonggeun; Kim, Seokhun; Yoon, Jaegu; Kim, Donghan; Hong, Suk-Gi; Park, Jin-Hwan; Mathew, Vinod; Han, Junhee; Song, Sun-Ju; Kim, Jaekook

    2016-01-01

    The real time detection of quantitative oxygen release from the cathode is performed by in-situ Gas Chromatography as a tool to not only determine the amount of oxygen release from a lithium-ion cell but also to address the safety concerns. This in-situ gas chromatography technique monitoring the gas evolution during electrochemical reaction presents opportunities to clearly understand the effect of surface modification and predict on the cathode stability. The oxide cathode, 0.5Li2MnO3∙0.5LiNi0.4Co0.2Mn0.4O2, surface modified by amorphous cobalt-phosphate nanoparticles (a-CoPO4) is prepared by a simple co-precipitation reaction followed by a mild heat treatment. The presence of a 40 nm thick a-CoPO4 coating layer wrapping the oxide powders is confirmed by electron microscopy. The electrochemical measurements reveal that the a-CoPO4 coated overlithiated layered oxide cathode shows better performances than the pristine counterpart. The enhanced performance of the surface modified oxide is attributed to the uniformly coated Co-P-O layer facilitating the suppression of O2 evolution and offering potential lithium host sites. Further, the formation of a stable SEI layer protecting electrolyte decomposition also contributes to enhanced stabilities with lesser voltage decay. The in-situ gas chromatography technique to study electrode safety offers opportunities to investigate the safety issues of a variety of nanostructured electrodes. PMID:27001370

  10. Investigations on the Cosputtered ITO-ZnO Transparent Electrode Ohmic Contacts to n-GaN

    Directory of Open Access Journals (Sweden)

    Wei-Hua Hsiao

    2016-02-01

    Full Text Available Transparent indium tin oxide (ITO and cosputtered ITO-zinc oxide (ZnO films’ contacts to an n-GaN epilayer were investigated. Both of these electrodes’ contact to the n-GaN epilayer showed Schottky behavior, although the contact resistance of the ITO-ZnO/n-GaN system was lower than that of the ITO/n-GaN system. By placing a thin Ti interlayer between the ITO-ZnO/n-GaN interface, nonalloyed ohmic contact was achieved. The inset Ti interlayer was both beneficial both for enhancing the outdiffusion of the nitrogen atoms at the surface of the n-GaN and suppressing the indiffusion of oxygen atoms from the surface of the ITO-ZnO to n-GaN. The figure-of-merit (FOM, evaluated from the specific contact resistance and optical property of the Ti/ITO-ZnO system’s contact to the n-GaN epilayer, was optimized further at an adequate thickness of the Ti interlayer.

  11. 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.

  12. Cermet electrode

    Science.gov (United States)

    Maskalick, Nicholas J.

    1988-08-30

    Disclosed is a cermet electrode consisting of metal particles of nickel, cobalt, iron, or alloys or mixtures thereof immobilized by zirconia stabilized in cubic form which contains discrete deposits of about 0.1 to about 5% by weight of praseodymium, dysprosium, terbium, or a mixture thereof. The solid oxide electrode can be made by covering a substrate with particles of nickel, cobalt, iron, or mixtures thereof, growing a stabilized zirconia solid oxide skeleton around the particles thereby immobilizing them, contacting the skeleton with a compound of praseodymium, dysprosium, terbium, or a mixture thereof, and heating the skeleton to a temperature of at least 500.degree. C. The electrode can also be made by preparing a slurry of nickel, cobalt, iron, or mixture and a compound of praseodymium, dysprosium, terbium, or a mixture thereof, depositing the slurry on a substrate, heating the slurry to dryness, and growing a stabilized zirconia skeleton around the metal particles.

  13. Investigation of the influence of copper welding electrodes on Ti-8Al-1Mo-1V and Ti-6Al-2Sn-4Zr-2Mo with respect to solid metal induced embrittlement

    International Nuclear Information System (INIS)

    Solid Metal Induced Embrittlement (SMIE) is caused by a specific combination of two solid metals in intimate contact. Cadmium, gold, silver and copper are known to cause SMIE in certain titanium alloys. Solid copper is used in welding electrodes and fixtures in various manufacturing processes for titanium parts within the aerospace industry. In the case of resistance welding, titanium alloys are in intimate contact with solid copper, since the electrodes resistively heat the titanium part under pressure during the welding process. No previous published work that investigates the risk of using copper electrodes for welding of titanium alloys is available in the literature, but an initial study using U-bend testing indicates that solid copper in contact with Ti-8Al-1V-1Mo and Ti-6Al-2Sn-4Zr-2Mo could lead to SMIE. Therefore, in the present study, resistance welded Ti-8Al-1V-1Mo and Ti-6Al-2Sn-4Zr-2Mo have been evaluated to investigate the influence of copper electrodes on these alloys. Furthermore, resistance welded specimens sputtered with copper and gold to promote SMIE have also been evaluated. No SMIE was found in the resistance welded specimens, which may be explained by the short interaction time that the copper electrodes are in intimate contact with the titanium alloy, and/or the magnitude of residual stresses after welding, which may be too low to initiate SMIE.

  14. Investigation on the electrochemical behavior of neodymium chloride at W, Al and Cd electrodes in molten LiCl-KCl eutectic

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Electrochemical behavior of neodymium (III) ion was studied in LiCl-KCl eutectic melt in the temperature range 723-798 K on inert tungsten electrode using various transient electrochemical techniques such as cyclic voltammetry, convolution voltammetry, chronopotentiometry and square wave voltammetry. The reduction of Nd(III) ion to Nd metal on tungsten electrode takes place in two steps- Nd(III)/Nd(II) and Nd(II)/Nd(0). Reduction of Nd(III) to Nd(II) showed reversible electrode behavior and that for Nd(II) to Nd metal followed the quasi-reversible behavior. Heterogeneous rate constant for the reduction, Nd(II)/Nd(0) was estimated from the convoluted voltammograms. The apparent standard electrode potentials,ENd(III)/Nd(II)*, ENd(II)/Nd(0)* and ENd(III)/Nd(0)* were estimated from the cyclic voltammograms and open circuit potentiograms. • The electrode behavior of Nd(III) ion on solid aluminium electrode and liquid cadmium electrode was studied by cyclic voltammetry. Under-potential reduction of Nd(III) ion takes place on Al and Cd cathodes in a single step with three electron transfer. The apparent standard electrode potentials, ENd(III)/Nd(Al)* and ENd(III)/Nd(Cd)* were estimated for different temperatures in the range 698-773 K. The formation of intermetallics, Al11Nd3 and Cd11Nd were studied from open circuit potential measurement on Al and Cd film electrode respectively. Thermodynamic properties of Nd-Al and Nd-Cd systems were evaluated. - Abstract: Electrochemical behavior of neodymium (III) ion was studied in LiCl-KCl eutectic melt in the temperature range 723-798 K on inert tungsten electrode using various transient electrochemical techniques such as cyclic voltammetry, convolution voltammetry, chronopotentiometry and square wave voltammetry. The reduction of Nd(III) ion to Nd metal on tungsten electrode takes place in two steps- Nd(III)/Nd(II) and Nd(II)/Nd(0). The diffusion coefficient of Nd(III) and Nd (II) ions were

  15. Electrochemical impedance spectroscopy investigations on the L-cysteine-thiolate self-assembled monolayers formed at p-GaAs(100) electrodes

    International Nuclear Information System (INIS)

    Electrochemical impedance spectroscopy investigations carried out in solutions with different pH brought evidence that the monolayers of L-cysteine-thiolate self-assembled on GaAs (hkl) electrodes exert a complex molecular control over their electrochemical behavior. The analysis of the impedance spectra coupled with that of the XPS data and the AFM images taken before and after the EIS measurements reveled that both pH and applied potential brings significant changes at the electrified interface. The most important effect of pH is the conformational change of the L-cysteine-thiolate molecule observed at pH 11 that allows the interaction of the carboxyl group with the substrate atoms. A similar conformational change occurs at pH 5.5 but only under the applied potential control, being just a consequence of another major effect of the applied electric field. This is the H+ transfer inside the L-cysteine-thiolate film, an electric field driven process but pH dependent, which results in significant charge diminution both in the organic overlayer and in the semiconductor depletion region

  16. An investigation of optimal interfacial film condition for Cu-Mn alloy based source/drain electrodes in hydrogenated amorphous silicon thin film transistors

    Directory of Open Access Journals (Sweden)

    Haruhiko Asanuma

    2012-06-01

    Full Text Available To aid in developing next generation Cu-Mn alloy based source/drain interconnects for thin film transistor liquid crystal displays (TFT-LCDs, we have investigated the optimal structure of a pre-formed oxide layer on phosphorus doped hydrogenated amorphous silicon (n+a-Si:H that does not degrade TFT electrical properties. We use transmission electron microscopy (TEM and electron energy loss spectroscopy (EELS to examine composition depth profiles of and structural information for the Cu-Mn alloy/n+a-Si:H interface region. In aiming to achieve the same electrical properties as those of TFTs having conventional Mo source/drain electrodes, we have obtained three important findings: (1 in typical TFT-LCD manufacturing processes, no Mn complex oxide layer is formed because Mn cannot diffuse substantially into an n+a-Si:H surface during low temperature (below 300°C processes and the growth of Mn complex oxide layer would also be limited by the absence of excess oxygen species; (2 a pre-formed silicon oxide layer much thicker than 1 nm severely degrades TFT electrical properties and therefore an ultrathin (≈1 nm silicon oxide layer is required to prevent the degradation; (3 Cu diffuses into an n+a-Si:H layer at oxygen-deficient spots and thus uniform surface oxidation is required to prevent the diffusion.

  17. Performance of lightweight nickel electrodes

    Science.gov (United States)

    Britton, Doris L.

    1988-01-01

    The NASA Lewis Research Center is currently developing nickel electrodes for nickel-hydrogen (Ni-H2) batteries. These electrodes are lighter in weight and have higher energy densities than the heavier state-of-the-art (SOA) sintered nickel electrodes. In the present approach, lightweight materials or plaques are used as conductive supports for the nickel hydroxide active material. These plaques (fiber and felt, nickel plated plastic and graphite) are commercial products that are fabricated into nickel electrodes by electrochemically impregnating them with active material. Evaluation is performed in half cells structured in the bipolar configuration. Initial performance tests include capacity measurements at five discharge levels, C/2, 1.0C, 1.37C, 2.0C and 2.74C. The electrodes that pass the initial tests are life cycle tested in a low earth orbit regime at 80 percent depth of discharge. Different formulations of nickel fiber materials obtained from several manufacturers are currently being tested as possible candidates for nickel electrodes. One particular lightweight fiber mat electrode has accumulated over 3000 cycles to date, with stable capacity and voltage. Life and performance data of this electrode were investigated and presented. Good dimensional stability and active material adherence have been demonstrated in electrodes made from this lightweight plaque.

  18. 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. PMID:27158288

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

    International Nuclear Information System (INIS)

    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 Cu2+ and Eu3+ cations, has showed that the C3 thin film is more sensitive and selective towards Eu3+ 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: → C1 and C3 azo-calix[4]arenes thin films are deposited on the gold surface. → The lower hydrophobicity for C3 was attributed to the presence of hydroxyl groups. → The C3 thin film is more sensitive and selective towards Eu3+ than C1 one. → This best performance is due to the presence of two ester groups acting as clips.

  20. Investigation of copper and silver nanoparticles deposited on a nitrogen-doped diamond-like carbon (N-DLC) film electrode for bio-sensing

    International Nuclear Information System (INIS)

    An electrochemical method has been employed in this work to deposit copper and silver nanoparticles onto chemical-vapor-deposited nitrogen doped hydrogen amorphous diamond-like carbon (N-DLC) film electrodes. The electrochemical behaviors of the metal-nanoparticle-modified N-DLC electrodes have been characterized in the presence of glucose and hydrogen peroxide in the electrolyte. The copper and the silver nanoparticles possess high catalytic function for the oxidation of glucose and the reduction of hydro peroxide, respectively. The well-defined reduction responses of the reduction or hydrogen peroxide give the silver-nanoparticle-modified N-DLC electrodes high potential for application in hydrogen-peroxide sensing without a label.

  1. Investigating the dependence of the temperature of high-intensity discharge (HID) lamp electrodes on the operating frequency by pyrometric measurements

    Science.gov (United States)

    Reinelt, J.; Westermeier, M.; Ruhrmann, C.; Bergner, A.; Awakowicz, P.; Mentel, J.

    2011-03-01

    Phase-resolved temperature distributions are determined along a rod-shaped tungsten electrode, by which an ac arc is operated within a model lamp filled with argon. Switched dc and sinusoidal currents are applied with amplitudes of several amperes and operating frequencies being varied between 10 Hz and 10 kHz. The temperature is deduced from the grey body radiation of the electrode being recorded with a spectroscopic measuring system. Phase-resolved values of the electrode tip temperature Ttip and of the power input Pin are determined comparing the measured temperature distributions with the integral of the one-dimensional heat balance with these parameters as integration constants. They are supplemented by phase-resolved measurements of the sum of cathode and anode fall called the electrode sheath voltage. If a switched dc current is applied it is found that both quantities are within the cathodic phase only marginally higher than for a cathode being operated with a dc current. Ttip and Pin start to decrease for low currents and to increase for high currents at the beginning of the anodic phase. But with increasing operating frequency the deviations from the cathodic phase are reduced until they cannot be resolved for frequencies of several kHz. A more pronounced modulation, but the same tendencies, is observed with a sinusoidal current waveform. For 10 kHz a diffuse arc attachment with an almost phase-independent electrode tip temperature, which deviates only marginally from that of a dc cathode, and an electrode sheath voltage proportional to the arc current is established with both current waveforms.

  2. Investigation of the effect of mechanical pressure on the performance of negative lead accumulator electrodes during partial state of charge operation

    Czech Academy of Sciences Publication Activity Database

    Bača, P.; Micka, Karel; Křivík, P.; Tonar, K.; Tošer, P.

    2012-01-01

    Roč. 207, JUN 1 2012 (2012), s. 37-44. ISSN 0378-7753 Institutional research plan: CEZ:AV0Z40400503 Keywords : Lead battery electrodes * Doping with carbon or titanium dioxide * Effect of mechanical pressure Subject RIV: CG - Electrochemistry Impact factor: 4.675, year: 2012

  3. Investigating the depth electrode-brain interface in deep brain stimulation using finite element models with graded complexity in structure and solution

    OpenAIRE

    Yousif, Nada; Liu, Xuguang

    2009-01-01

    Deep brain stimulation (DBS) is an increasingly used surgical therapy for a range of neurological disorders involving the long-term electrical stimulation of various regions of the human brain in a disorder-specific manner. Despite being used for the last 20 years, the underlying mechanisms are still not known, and disputed. In particular, when the electrodes are implanted into the human brain, an interface is created with changing biophysical properties which may impact on stimulation. We pr...

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

    International Nuclear Information System (INIS)

    Positively charged gold nanoparticle (positively charged nano-Au), which was prepared, characterized by ξ-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 10-7-6.7 x 10-4 M and a low detection limit of 1.5 x 10-7 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

  5. 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.

  6. Graphene-based electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xiao; Zeng, Zhiyuan; Fan, Zhanxi; Liu, Juqing; Zhang, Hua [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798 (Singapore)

    2012-11-27

    Graphene, the thinnest two dimensional carbon material, has become the subject of intensive investigation in various research fields because of its remarkable electronic, mechanical, optical and thermal properties. Graphene-based electrodes, fabricated from mechanically cleaved graphene, chemical vapor deposition (CVD) grown graphene, or massively produced graphene derivatives from bulk graphite, have been applied in a broad range of applications, such as in light emitting diodes, touch screens, field-effect transistors, solar cells, supercapacitors, batteries, and sensors. In this Review, after a short introduction to the properties and synthetic methods of graphene and its derivatives, we will discuss the importance of graphene-based electrodes, their fabrication techniques, and application areas. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Graphene-based electrodes.

    Science.gov (United States)

    Huang, Xiao; Zeng, Zhiyuan; Fan, Zhanxi; Liu, Juqing; Zhang, Hua

    2012-11-27

    Graphene, the thinnest two dimensional carbon material, has become the subject of intensive investigation in various research fields because of its remarkable electronic, mechanical, optical and thermal properties. Graphene-based electrodes, fabricated from mechanically cleaved graphene, chemical vapor deposition (CVD) grown graphene, or massively produced graphene derivatives from bulk graphite, have been applied in a broad range of applications, such as in light emitting diodes, touch screens, field-effect transistors, solar cells, supercapacitors, batteries, and sensors. In this Review, after a short introduction to the properties and synthetic methods of graphene and its derivatives, we will discuss the importance of graphene-based electrodes, their fabrication techniques, and application areas. PMID:22927209

  8. 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.

  9. 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)

  10. Esophageal ECG: The challenge of electrode design

    OpenAIRE

    Niederhauser, Thomas; Häberlin, Andreas; Vogel, R; Marisa, Thanks; Götte, Josef; Jacomet, Marcel

    2011-01-01

    Two commercially available electrode catheters are examined for their suitability in esophageal long-term ECG recordings. Both, electrical sensing characteristics as well as clinical acceptance were investigated in a clinical study including inpatients with cardiovascular diseases. In total, 31 esophageal ECG were obtained in 36 patients. Results showed that esophageal electrodes were well tolerated by the patients. Hemispherical electrodes with higher diameter required more insertion attempt...

  11. Micromachined electrode array

    Energy Technology Data Exchange (ETDEWEB)

    Okandan, Murat (Edgewood, NM); Wessendorf, Kurt O. (Albuquerque, NM)

    2007-12-11

    An electrode array is disclosed which has applications for neural stimulation and sensing. The electrode array, in certain embodiments, can include a plurality of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. In other embodiments of the electrode array, the electrodes can be fixed to the substrate. The electrode array can be formed from a combination of bulk and surface micromachining, and can include electrode tips having an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis.

  12. Flexible retinal electrode array

    Energy Technology Data Exchange (ETDEWEB)

    Okandan, Murat (Albuquerque, NM); Wessendorf, Kurt O. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

    2006-10-24

    An electrode array which has applications for neural stimulation and sensing. The electrode array can include a large number of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. The electrode array can be formed from a combination of bulk and surface micromachining, with electrode tips that can include an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis where the electrodes can be tailored to provide a uniform gentle contact pressure with optional sensing of this contact pressure at one or more of the electrodes.

  13. High performance cermet electrodes

    Science.gov (United States)

    Isenberg, Arnold O.; Zymboly, Gregory E.

    1986-01-01

    Disclosed is a method of increasing the operating cell voltage of a solid oxide electrochemical cell having metal electrode particles in contact with an oxygen-transporting ceramic electrolyte. The metal electrode is heated with the cell, and oxygen is passed through the oxygen-transporting ceramic electrolyte to the surface of the metal electrode particles so that the metal electrode particles are oxidized to form a metal oxide layer between the metal electrode particles and the electrolyte. The metal oxide layer is then reduced to form porous metal between the metal electrode particles and the ceramic electrolyte.

  14. Frequency response measurements in battery electrodes

    Science.gov (United States)

    Thomas, Daniel L.

    1992-01-01

    Electrical impedance spectroscopy was used to investigate the behavior of porous zinc, silver, cadmium, and nickel electrodes. State of charge could be correlated with impedance data for all but the nickel electrodes. State of health was correlated with impedance data for two AgZn cells, one apparently good and the other bad. The impedance data was fit to equivalent circuit models.

  15. 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. PMID:26372107

  16. Current-dependent electrode lattice fluctuations and anode phase evolution in a lithium-ion battery investigated by in situ neutron diffraction

    International Nuclear Information System (INIS)

    Highlights: ► Links between time-dependent structural parameters and battery performance. ► Current-dependent evolution of the anode. ► Direct correlation of LixCoO2 and LiC6 structure with battery capacity. -- Abstract: This work uses real-time in situ neutron powder diffraction to study the electrode lattice response and anode phase evolution in a commercial lithium-ion battery. We show that the time-resolved lattice response of the LixCoO2 cathode and LixC6 anode under non-equilibrium conditions varies proportionally with the applied current, where higher current results in faster structural change. Higher current also reduces the LixCoO2 cathode c lattice parameter and the LiC6 quantity that forms at the charged state of the battery, both of which are related to lower battery capacity. At the anode, we find that the LixC6 phase evolution is current-dependent

  17. Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution

    Science.gov (United States)

    Orikasa, Yuki; Gogyo, Yuma; Yamashige, Hisao; Katayama, Misaki; Chen, Kezheng; Mori, Takuya; Yamamoto, Kentaro; Masese, Titus; Inada, Yasuhiro; Ohta, Toshiaki; Siroma, Zyun; Kato, Shiro; Kinoshita, Hajime; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

    2016-05-01

    Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances.

  18. Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution.

    Science.gov (United States)

    Orikasa, Yuki; Gogyo, Yuma; Yamashige, Hisao; Katayama, Misaki; Chen, Kezheng; Mori, Takuya; Yamamoto, Kentaro; Masese, Titus; Inada, Yasuhiro; Ohta, Toshiaki; Siroma, Zyun; Kato, Shiro; Kinoshita, Hajime; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

    2016-01-01

    Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances. PMID:27193448

  19. Dry electrodes for electrocardiography

    International Nuclear Information System (INIS)

    Patient biopotentials are usually measured with conventional disposable Ag/AgCl electrodes. These electrodes provide excellent signal quality but are irritating for long-term use. Skin preparation is usually required prior to the application of electrodes such as shaving and cleansing with alcohol. To overcome these difficulties, researchers and caregivers seek alternative electrodes that would be acceptable in clinical and research environments. Dry electrodes that operate without gel, adhesive or even skin preparation have been studied for many decades. They are used in research applications, but they have yet to achieve acceptance for medical use. So far, a complete comparison and evaluation of dry electrodes is not well described in the literature. This work compares dry electrodes for biomedical use and physiological research, and reviews some novel systems developed for cardiac monitoring. Lastly, the paper provides suggestions to develop a dry-electrode-based system for mobile and long-term cardiac monitoring applications. (topical review)

  20. 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.

  1. Microresonator electrode design

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. The Composite Insertion Electrode

    DEFF Research Database (Denmark)

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

    1984-01-01

    The specific energy obtainable by discharge of porous insertion electrodes is limited by electrolyte depletion in thepores. This can be overcome using a solid ion conductor as electrolyte. The term "composite" is used to distinguishthese electrodes from porous electrodes with liquid electrolyte...

  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. 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.

  5. Effect of electrode thickness variation on operation of capacitive deionization

    OpenAIRE

    Porada, S.; Bryjak, M.; Wal, van der, A.C.; Biesheuvel, P. M.

    2012-01-01

    In capacitive deionization (CDI) water is desalinated by applying an electrical field between two porous electrodes placed on either side of a spacer channel that transports the aqueous solution. In this work we investigate the equilibrium salt adsorption and the dynamic development of the effluent salt concentration in time, both as function of spacer and electrode thicknesses. The electrode thickness will be varied in a symmetric manner (doubling both electrodes) and in an asymmetric manner...

  6. Advanced screening of electrode couples

    Science.gov (United States)

    Giner, J. D.; Cahill, K.

    1980-01-01

    The chromium (Cr(3+)/Cr(2+)) redox couple (electrolyte and electrode) was investigated to determine its suitability as negative electrode for the iron (Fe(3+)/Fe(2+))-chromium (Cr(3+)/Cr(2+)) redox flow battery. Literature search and laboratory investigation established that the solubility and stability of aqueous acidic solutions of chromium(3) chloride and chromium(2) chloride are sufficient for redox battery application. Four categories of electrode materials were tested; namely, metals and metalloid materials (elements and compounds), alloys, plated materials, and Teflon-bonded materials. In all, the relative performance of 26 candidate electrode materials was evaluated on the basis of slow scan rate linear sweep voltammetry in stirred solution. No single material tested gave both acceptable anodic an acceptable cathodic performance. However, the identification of lead as a good cathodic electrocatalyst and gold as a good anodic electrocatalyst led to the invention of the lead/gold combination electrocatalyst. This type of catalyst can be fabricated in several ways and appears to offer the advantages of each metal without the disadvantages associated with their use as single materials. This lead/gold electrocatalyst was tested by NASA-Lewis Research Center in complete, flowing, redox batteries comprising a stack of several cells. A large improvement in the battery's coulombic and energy efficiency was observed.

  7. Stabilizing dimensional changes in Si-based composite electrodes by controlling the electrode porosity: An in situ electrochemical dilatometric study

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Goojin [Green Energy System Center, Kumoh National Institute of Technology, Gumi, Gyeongbuk 730-701 (Korea, Republic of); Lee, Sang Min; Choi, Nam Soon [Battery Development Team, Samsung SDI Co., Ltd. Cheonan, Chungnam 330-300 (Korea, Republic of); Kim, Young-Ugk, E-mail: kyuang@snu.ac.kr [Battery Development Team, Samsung SDI Co., Ltd. Cheonan, Chungnam 330-300 (Korea, Republic of); Lee, Churl Kyoung [School of Advanced Materials and System Engineering, Kumoh National Institute of Technology, Gumi, Gyeongbuk, 730-701 (Korea, Republic of)

    2011-05-30

    Highlights: > A porosity-controllable Si-based composite electrode was fabricated. > PMMA showing unzipping phenomena was utilized as a pore-forming agent. > Cyclic dilation behavior was investigated with an in situ electrochemical dilatometry. > PMMA-treated electrodes exhibited improved cycle performance. > Control of electrode porosity by PMMA can be an effective way for Si-based electrodes. - Abstract: A porosity-controllable Si-based composite electrode was fabricated in the present study. Poly(methyl methacrylate) (PMMA), which possesses the unique thermal property of unzipping, was utilized as a pore-forming agent during electrode fabrication. PMMA-treated electrodes presented relatively low volume expansion and little deformation during lithiation. The cyclic dilation behavior of PMMA-treated electrodes was investigated by applying an in situ electrochemical dilatometric method, and enhanced dimensional reversibility during cycling was observed. The dilation behavior was closely related to the electrochemical performance, and PMMA-treated electrodes exhibited improved capacity retention and low impedance change during cycling. The newly generated pores in the PMMA-treated electrode can accommodate the volumetric expansion of Si-based active materials, which suppresses electrode deformation and the breakdown of the electrical network. The porosity plays an important role in Si-based electrodes. Thus, controlling the porosity through PMMA-treatment can be an effective way for the application of Si-based composite electrodes for advanced lithium-ion batteries.

  8. Effect of Particle Size on Electrode Potential and Thermodynamics of Nanoparticles Electrode in Theory and Experiment

    International Nuclear Information System (INIS)

    The particle size of electrode materials has a significant influence on the standard electrode potential and the thermodynamic properties of electrode reactions. In this paper, the size-dependent electrochemical thermodynamics has been theoretically investigated and successfully deduced electrochemical thermodynamics equations for nanoparticles electrode. At the same time, the electrode potential and thermodynamical properties of Ag2O/Ag nanoparticles electrode constructed by the solid and spherical Ag2O nanoparticles with different sizes further testified that the particle size of nanoparticles has a significant effect on electrochemical thermodynamics. The results show that the electrode potential depends on that of the smallest nanoparticle in a nanoparticles electrode which consisted of different particle sizes of nano-Ag2O. When the size of Ag2O nanoparticles reduces, the standard electrode potentials and the equilibrium constants of the corresponding electrode reactions increase, and the temperature coefficient, the mole Gibbs energy change, the mole enthalpy change and the mole entropy change decrease. Moreover, these physical quantities are all linearly related with the reciprocal of average particle size (r > 10 nm). The experimental regularities coincide with the theoretical equations

  9. A comparison study of electrodes for neonate electrical impedance tomography

    International Nuclear Information System (INIS)

    Electrical impedance tomography (EIT) is an imaging technique that has the potential to be used for studying neonate lung function. The properties of the electrodes are very important in multi-frequency EIT (MFEIT) systems, particularly for neonates, as the skin cannot be abraded to reduce contact impedance. In this work, the impedance of various clinical electrodes as a function of frequency is investigated to identify the optimum electrode type for this application. Six different types of self-adhesive electrodes commonly used in general and neonatal cardiology have been investigated. These electrodes are Ag/AgCl electrodes from the Ambu® Cardiology Blue sensors range (BR, NF and BRS), Kendall (KittyCat(TM) and ARBO®) and Philips 13953D electrodes. In addition, a textile electrode without gel from Textronics was tested on two subjects to allow comparison with the hydrogel-based electrodes. Two- and four-electrode measurements were made to determine the electrode-interface and tissue impedances, respectively. The measurements were made on the back of the forearm of six healthy adult volunteers without skin preparation with 2.5 cm electrode spacing. Impedance measurements were carried out using a Solartron SI 1260 impedance/gain-phase analyser with a frequency range from 10 Hz to 1 MHz. For the electrode-interface impedance, the average magnitude decreased with frequency, with an average value of 5 kΩ at 10 kHz and 337 Ω at 1 MHz; for the tissue impedance, the respective values were 987 Ω and 29 Ω. Overall, the Ambu BRS, Kendall ARBO® and Textronics textile electrodes gave the lowest electrode contact impedance at 1 MHz. Based on the results of the two-electrode measurements, simple RC models for the Ambu BRS and Kendall-ARBO and Textronics textile electrodes have been derived for MFEIT applications

  10. 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

  11. Electrochemistry at Nanometer-Scaled Electrodes

    Science.gov (United States)

    Watkins, John J.; Zhang, Bo; White, Henry S.

    2005-05-01

    Advances in the fabrication of nanometer-scaled electrodes during the past decade have created a number of exciting opportunities in both physical chemistry and analytical measurements. This article describes how Pt electrodes of nanometer dimensions are synthesized and characterized in a chemical laboratory. A few examples of their applications in fundamental studies of electron-transfer mechanisms and in analytical chemistry are presented. Examples include investigations of the dependence of electron-transfer kinetics and molecular diffusion on interfacial electric fields and electrochemical detection of very small quantities of a redox-active species (zeptomole detection). The concept of comparing the electrode size to the length scales of various microscopic structures (e.g., the double layer) and chemical steps that define electrochemical reactions is emphasized. This approach allows students to understand why new phenomena appear as the electrode size is reduced to the nanometer scale. A brief overview of literature describing electrochemical experimentation with nanometer-scaled electrodes is also included.

  12. Optimal geometry toward uniform current density electrodes

    International Nuclear Information System (INIS)

    Electrodes are commonly used to inject current into the human body in various biomedical applications such as functional electrical stimulation, defibrillation, electrosurgery, RF ablation, impedance imaging, and so on. When a highly conducting electrode makes direct contact with biological tissues, the induced current density has strong singularity along the periphery of the electrode, which may cause painful sensation or burn. Especially in impedance imaging methods such as the magnetic resonance electrical impedance tomography, we should avoid such singularity since more uniform current density underneath a current-injection electrode is desirable. In this paper, we study an optimal geometry of a recessed electrode to produce a well-distributed current density on the contact area under the electrode. We investigate the geometry of the electrode surface to minimize the edge singularity and produce nearly uniform current density on the contact area. We propose a mathematical framework for the uniform current density electrode and its optimal geometry. The theoretical results are supported by numerical simulations

  13. 超级电容器Mn-Pb纳米复合电极材料的电化学性能研究%Electrochemical investigation of Mn-Pb nanocomposite oxide for supercapacitor electrode material

    Institute of Scientific and Technical Information of China (English)

    张治安; 杨邦朝; 胡永达

    2006-01-01

    Mn-Pb nanocomposite oxide, as electrode material for supercapacitor, was successfully prepared by solid-state reaction of KMnO4 with manganese acetate and lead acetate at low temperature. The nanocomposite oxide was characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The capacitive characteristics of the nanocomposite oxide in 1mol/L Na2 SO4 aqueous electrolyte were investigated with cyclic voltammetry and chronopotentiometry in a three-electrode system. It was found that the nanocomposite oxide was amorphous with the particle size of 10nm. The nanocomposite oxide exhibited excellent capacitive properties within the potential range from -0.2~+0.9 (V vs. SCE), indicating a promising electrode material for supercapacitor. The specific capacitance of the nanocomposite oxide decreased with increasing discharge current and it was 180.5F/g by constant current discharge of 2mA.%利用低温固相反应法制备了Mn-Pb复合氧化物超级电容器电极材料.采用XRD、TEM、循环伏安和恒流充放电法对电极材料的形貌和结构特点以及电化学性能进行了测试分析.结果表明,复合氧化物的粒径均为纳米尺寸,呈无定型结构.复合氧化物在1mol/L Na2SO4中,电位窗口为-0.2~0.9(V vs.SCE)范围内具有典型的电容特征.纳米氧化物电极比容量随放电电流的增大而减小.当放电电流为2mA时,Mn-Pb复合氧化物电极的比容量为180.5F/g.

  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. 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

  16. Transmission electron microscopy and ferromagnetic resonance investigations of tunnel magnetic junctions using Co2MnGe Heusler alloys as magnetic electrodes

    Science.gov (United States)

    Belmeguenai, M.; Genevois, C.; Zighem, F.; Roussigné, Y.; Chérif, S. M.; Westerholt, K.; El Bahoui, A.; Fnidiki, A.; Moch, P.

    2014-01-01

    HRTEM, nano-beam electronic diffraction, energy dispersive X-rays scanning spectroscopy, Vibrating Sample Magnetometry (VSM) and FerroMagnetic Resonance (FMR) techniques are used in view of comparing (static and dynamic) magnetic and structural properties of Co2MnGe (13 nm)/Al2O3 (3 nm)/Co (13 nm) tunnel magnetic junctions (TMJ), deposited on various single crystalline substrates (a-plane sapphire, MgO(100) and Si(111)). They allow for providing a correlation between these magnetic properties and the fine structure investigated at atomic scale. The Al2O3 tunnel barrier is always amorphous and contains a large concentration of Co atoms, which, however, is significantly reduced when using a sapphire substrate. The Co layer is polycrystalline and shows larger grains for films grown on a sapphire substrate. The VSM investigation reveals in-plane anisotropy only for samples grown on a sapphire substrate. The FMR spectra of the TMJs are compared to the obtained ones with a single Co and Co2MnGe films of identical thickness deposited on a sapphire substrate. As expected, two distinct modes are detected in the TMJs while only one mode is observed in each single film. For the TMJ grown on a sapphire substrate the FMR behavior does not significantly differ from the superposition of the individual spectra of the single films, allowing for concluding that the exchange coupling between the two magnetic layers is too small to give rise to observable shifts. For TMJs grown on a Si or on a MgO substrate the resonance spectra reveal one mode which is nearly identical to the obtained one in the single Co film, while the other observed resonance shows a considerably smaller intensity and cannot be described using the magnetic parameters appropriate to the single Co2MnGe film.

  17. Transmission electron microscopy and ferromagnetic resonance investigations of tunnel magnetic junctions using Co{sub 2}MnGe Heusler alloys as magnetic electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Belmeguenai, M., E-mail: belmeguenai.mohamed@univ-paris13.fr [LSPM (CNRS-UPR 3407), Université Paris 13, 99 avenue Jean-Baptiste Clément, 93430 Villetaneuse (France); Genevois, C. [Groupe de Physique des Matériaux, UMR CNRS 6634, Site Universitaire du Madrillet, BP12, 76801 Saint Etienne du Rouvray cedex (France); Zighem, F.; Roussigné, Y.; Chérif, S.M. [LSPM (CNRS-UPR 3407), Université Paris 13, 99 avenue Jean-Baptiste Clément, 93430 Villetaneuse (France); Westerholt, K. [Institut für Experimentelle Physik, Ruhr-Universität Bochum, 44780 Bochum (Germany); El Bahoui, A.; Fnidiki, A. [Groupe de Physique des Matériaux, UMR CNRS 6634, Site Universitaire du Madrillet, BP12, 76801 Saint Etienne du Rouvray cedex (France); Moch, P. [LSPM (CNRS-UPR 3407), Université Paris 13, 99 avenue Jean-Baptiste Clément, 93430 Villetaneuse (France)

    2014-01-31

    High resolution transmission electron microscopy, nano-beam electronic diffraction, energy dispersive X-rays scanning spectroscopy, vibrating sample magnetometry (VSM) and ferromagnetic resonance (FMR) techniques are used in view of comparing (static and dynamic) magnetic and structural properties of Co{sub 2}MnGe(13 nm)/Al{sub 2}O{sub 3}(3 nm)/Co(13 nm) tunnel magnetic junctions (TMJs), deposited on various single crystalline substrates (a-plane sapphire, MgO(100) and Si(111)). They allow for providing a correlation between these magnetic properties and the fine structure investigated at atomic scale. The Al{sub 2}O{sub 3} tunnel barrier is always amorphous and contains a large concentration of Co atoms, which, however, is significantly reduced when using a sapphire substrate. The Co layer is polycrystalline and shows larger grains for films grown on a sapphire substrate. The VSM investigation reveals in-plane anisotropy only for samples grown on a sapphire substrate. The FMR spectra of the TMJs are compared to the obtained ones with a single Co and Co{sub 2}MnGe films of identical thickness deposited on a sapphire substrate. As expected, two distinct modes are detected in the TMJs while only one mode is observed in each single film. For the TMJ grown on a sapphire substrate, the FMR behavior does not significantly differ from the superposition of the individual spectra of the single films, allowing for a conclusion that the exchange coupling between the two magnetic layers is too small to give rise to observable shifts. For TMJs grown on a Si or on a MgO substrate, the resonance spectra reveal one mode which is nearly identical to the obtained one in the single Co film, while the other observed resonance shows a considerably smaller intensity and cannot be described using the magnetic parameters appropriate to the single Co{sub 2}MnGe film. The large Co concentration in the Al{sub 2}O{sub 3} interlayer prevents for a simple interpretation of the observed spectra

  18. Transmission electron microscopy and ferromagnetic resonance investigations of tunnel magnetic junctions using Co2MnGe Heusler alloys as magnetic electrodes

    International Nuclear Information System (INIS)

    High resolution transmission electron microscopy, nano-beam electronic diffraction, energy dispersive X-rays scanning spectroscopy, vibrating sample magnetometry (VSM) and ferromagnetic resonance (FMR) techniques are used in view of comparing (static and dynamic) magnetic and structural properties of Co2MnGe(13 nm)/Al2O3(3 nm)/Co(13 nm) tunnel magnetic junctions (TMJs), deposited on various single crystalline substrates (a-plane sapphire, MgO(100) and Si(111)). They allow for providing a correlation between these magnetic properties and the fine structure investigated at atomic scale. The Al2O3 tunnel barrier is always amorphous and contains a large concentration of Co atoms, which, however, is significantly reduced when using a sapphire substrate. The Co layer is polycrystalline and shows larger grains for films grown on a sapphire substrate. The VSM investigation reveals in-plane anisotropy only for samples grown on a sapphire substrate. The FMR spectra of the TMJs are compared to the obtained ones with a single Co and Co2MnGe films of identical thickness deposited on a sapphire substrate. As expected, two distinct modes are detected in the TMJs while only one mode is observed in each single film. For the TMJ grown on a sapphire substrate, the FMR behavior does not significantly differ from the superposition of the individual spectra of the single films, allowing for a conclusion that the exchange coupling between the two magnetic layers is too small to give rise to observable shifts. For TMJs grown on a Si or on a MgO substrate, the resonance spectra reveal one mode which is nearly identical to the obtained one in the single Co film, while the other observed resonance shows a considerably smaller intensity and cannot be described using the magnetic parameters appropriate to the single Co2MnGe film. The large Co concentration in the Al2O3 interlayer prevents for a simple interpretation of the observed spectra when using Si or MgO substrates. - Highlights:

  19. Use of glassy carbon as a working electrode in controlled potential coulometry.

    Science.gov (United States)

    Plock, C E; Vasquez, J

    1969-11-01

    Glassy carbon has been used as the working electrode in controlled potential coulometry. The results of coulometric investigations of chromium, copper, iron, uranium and neptunium are compared with results obtained with platinum or mercury working electrodes. The accuracy of results with the glassy carbon electrode compares favourably with the results obtainable with the other electrodes, but the precision is poorer. PMID:18960665

  20. Electrodes for microfluidic applications

    Science.gov (United States)

    Crocker, Robert W.; Harnett, Cindy K.; Rognlien, Judith L.

    2006-08-22

    An electrode device for high pressure applications. These electrodes, designed to withstand pressure of greater than 10,000 psi, are adapted for use in microfluidic devices that employ electrokinetic or electrophoretic flow. The electrode is composed, generally, of an outer electrically insulating tubular body having a porous ceramic frit material disposed in one end of the outer body. The pores of the porous ceramic material are filled with an ion conductive polymer resin. A conductive material situated on the upper surface of the porous ceramic frit material and, thus isolated from direct contact with the electrolyte, forms a gas diffusion electrode. A metal current collector, in contact with the gas diffusion electrode, provides connection to a voltage source.

  1. Bifunctional catalytic electrode

    Science.gov (United States)

    Cisar, Alan (Inventor); Murphy, Oliver J. (Inventor); Clarke, Eric (Inventor)

    2005-01-01

    The present invention relates to an oxygen electrode for a unitized regenerative hydrogen-oxygen fuel cell and the unitized regenerative fuel cell having the oxygen electrode. The oxygen electrode contains components electrocatalytically active for the evolution of oxygen from water and the reduction of oxygen to water, and has a structure that supports the flow of both water and gases between the catalytically active surface and a flow field or electrode chamber for bulk flow of the fluids. The electrode has an electrocatalyst layer and a diffusion backing layer interspersed with hydrophilic and hydrophobic regions. The diffusion backing layer consists of a metal core having gas diffusion structures bonded to the metal core.

  2. 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.

  3. Photoelectrolytic production of hydrogen using semiconductor electrodes

    Science.gov (United States)

    Byvik, C. E.; Walker, G. H.

    1976-01-01

    Experimental data for the photoelectrolytic production of hydrogen using GaAs photoanodes was presented. Four types of GaAs anodes were investigated: polished GaAs, GaAs coated with gold, GaAs coated with silver, and GaAs coated with tin. The maximum measured efficiency using a tungsten light source was 8.9 percent for polished GaAs electrodes and 6.3 percent for tin coated GaAs electrodes.

  4. AC Dielectrophoresis Using Elliptic Electrode Geometry

    OpenAIRE

    S. M. Rezaul Hasan; Aanan Khurma

    2011-01-01

    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...

  5. Surface modification of recording electrodes

    Directory of Open Access Journals (Sweden)

    Iaci Miranda Pereira

    2013-01-01

    Full Text Available 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 cardiac fibroblasts and rat cardiomyocytes when in contact with an electrode surface. Diisocyanate and poly(caprolactone diol were the main reagents for producing PUs. The electrochemical impedance of the electrode/electrolyte interface was accessed by electrochemical impedance spectroscopy. The cellular viability, proliferation, and morphology changes were investigated using an MTT assay. Cardiomyocyte adherence was observed by scanning electron microscopy. The obtained surface was uniform, flat, and transparent. The film showed good adhesion, and no peeling was detected. The electrochemical impedance decreased over time and was influenced by the ionic permeability of the PU layer. The five samples did not show cytotoxicity when in contact with neonatal rat cells.

  6. Electrode for MHD generator

    International Nuclear Information System (INIS)

    In accordance with the invention a ceramic-metal compound has been developed enabling appropriate electrodes to be prepared and also an electrode-insulator system meeting to a large extent the conditions required for use in a MHD generator. In this invention, a compound substance is made of a matrix in a refractory ceramic material containing 10 to 50% by volume of a continuous metallic reinforcement in a nonferromagnetic, electricity conducting, metal or alloy, resistant to oxidation and with a melting point above 10000C. The upper surface of an electrode made of this compound material can have a refractory ceramic layer of variable thickness to provide additional resistance to oxidation and for controlling the temperature of the electrode. The two sides of the electrode are coated with a refractory ceramic insulating material. The electrode-insulator system of the invention is an electrode having insulated side walls, a flexible separator resistant to high temperatures and an insulator in a refractory ceramic material

  7. Investigation of the Electrochemical Corrosion of Copper under a Micrometric Electrolyte Droplet Using a Three-Electrode System%用三电极体系研究铜在微液滴下的电化学腐蚀

    Institute of Scientific and Technical Information of China (English)

    程庆利; 张卫华; 陶彬

    2015-01-01

    由于大气腐蚀高阻抗的特征,传统的参比电极难以用于大气腐蚀研究之中。为了获取准确的大气腐蚀电化学信息,我们需要对传统的参比电极进行修改。本文在三电极体系中采用修改的参比电极,通过电化学阻抗和电化学极化两种方法研究铜在含有(NH4)2SO4液滴下的腐蚀行为,结果表明液滴下铜的平均腐蚀速率随着液滴体积从1到20μL增加而减小;当液滴高度不超过850μm时,平均腐蚀速率随着液滴高度的减小却迅速地增大。此外,电化学阻抗和电化学极化得出的腐蚀速率相一致,这证明修改的参比电极可以用于液滴下的大气腐蚀研究。%Owing to its high impedance, studying atmospheric corrosion using a traditional reference electrode (RE) is difficult. To obtain more accurate information on the electrochemical processes involved in atmospheric corrosion, it is necessary to improve the traditional RE. In this paper, the corrosion behavior of copper under an electrolyte droplet containing (NH4)2SO4 was investigated by electrochemical impedance spectroscopy (EIS) and polarization measurements using a three-electrode system with a modified RE. The average corrosion rate increased with decreasing electrolyte volumes (from 1 to 20μL) and with decreasing heights of the droplet at heights below 850μm. The EIS and polarization results were in agreement, thereby demonstrating that the modified RE could be effectively used to study atmospheric corrosion under an electrolyte droplet.

  8. 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

  9. Investigation into real-time pressure sensing properties of SnO2, TiO2, and TiO2/ZnO thick films with interdigitated electrodes

    International Nuclear Information System (INIS)

    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 SnO2, TiO2, and TiO2/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 SnO2, TiO2, and TiO2/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 10-3 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 SnO2, TiO2, and TiO2/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 SnO2, TiO2, and TiO2/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 responses to pressure.

  10. 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.

  11. Electrochemical Characterization of New Silver Gas Diffusion Electrodes during Oxygen Reduction in Alkaline Solution

    OpenAIRE

    Wagner, Norbert

    2013-01-01

    In order to analyze in detail the kinetics of the oxygen reduction reaction (ORR) and the influence of the porous electrode structure on the electrode performance in alkaline solution (10 M NaOH) at 80°C electrochemical impedance measurements (EIS) and cyclic voltammograms (CV) have been performed. The investigated electrodes were technical silver gas diffusion electrodes (GDE) and porous silver membranes with different pore radii ranging from 0.2 µm to 5 µm. Silver gas diffusion electrodes w...

  12. Boron-doped nanocrystalline diamond electrodes for neural interfaces: In vivo biocompatibility evaluation

    OpenAIRE

    María eAlcaide; Andrew eTaylor; Morten eFjorback; Vladimir eZachar; Cristian Pablo Pennisi

    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 ...

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

    OpenAIRE

    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 ...

  14. Composite Electrodes in Electrochemistry

    Czech Academy of Sciences Publication Activity Database

    Šebková, Světlana; Navrátil, Tomáš; Kopanica, M.

    Galway : National University of Ireland , 2004. s. 72. [International Conference on Electroanalysis /10./. 06.06.2004-10.06.2004, Galway] Keywords : electrochemistry * modern electroanalytical sensors * silver composite electrode Subject RIV: CG - Electrochemistry

  15. Nanostructured gold colloid electrodes

    International Nuclear Information System (INIS)

    Recent advances in the assembly of nanoparticle superstructures on electrodes are addressed here. Methods for the assembly and characterization of these arrays are summarized and their electronic, photoelectrochemical, and sensor applications are discussed. (orig.)

  16. 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. PMID:26241969

  17. Si film electrodes prepared on discontinuous current collector

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Gyu-bong; Im, Yeon-min; Lee, Won-rak; Lee, Sang-hun; Ji, Seong- yong [School of Materials Science and Engineering and Research Institute for Green Energy Convergence Technology, Gyeongsang National University, Gazwadong 900, Jinju, Gyeongnam 660-701 (Korea, Republic of); Kim, Guk-tae [Institute of Physical Chemistry, MEET Battery Research Center, Corrensstr 46, 48149 Münster (Germany); Nam, Tae-hyun [School of Materials Science and Engineering and Research Institute for Green Energy Convergence Technology, Gyeongsang National University, Gazwadong 900, Jinju, Gyeongnam 660-701 (Korea, Republic of); Kim, Ki-won, E-mail: kiwonkim@gnu.ac.kr [School of Materials Science and Engineering and Research Institute for Green Energy Convergence Technology, Gyeongsang National University, Gazwadong 900, Jinju, Gyeongnam 660-701 (Korea, Republic of)

    2013-11-01

    Discontinuous Si film electrodes with 400, 800, and 1700 μm discontinuous lines (break lines) were fabricated by a simple masking and etching process. The structural and electrochemical properties of continuous and discontinuous Si film electrodes were investigated by means of optical microscopy, field emission scanning electron microscopy, X-ray diffraction, and charge–discharge tests. Although all electrodes showed similar first-charge capacities in the range of 210–230 μAh/g, the discontinuous electrode exhibited improved coulombic efficiency and cyclability when compared to the continuous electrode. Up to 100 cycles, the discontinuous electrode with the shortest line distance of 400 μm demonstrated the highest efficiency (95.2%) and capacity retention (89%). Observation of the cycled Si film electrodes revealed that discontinuity enhanced the structural stability of the electrode during the charge–discharge process. - Highlights: • Si film electrodes with various distances between discontinuous lines were fabricated. • The discontinuous electrode improved coulombic efficiency and cycleability. • The discontinuous line in the Si film electrode enhanced the structural stability.

  18. Techniques of Electrode Fabrication

    Science.gov (United States)

    Guo, Liang; Li, Xinyong; Chen, Guohua

    Electrochemical applications using many kinds of electrode materials as an advanced oxidation/reduction technique have been a focus of research by a number of groups during the last two decades. The electrochemical approach has been adopted successfully to develop various environmental applications, mainly including water and wastewater treatment, aqueous system monitoring, and solid surface analysis. In this chapter, a number of methods for the fabrication of film-structured electrode materials were selectively reviewed. Firstly, the thermal decomposition method is briefly described, followed by introducing chemical vapor deposition (CVD) strategy. Especially, much attention was focused on introducing the methods to produce diamond novel film electrode owing to its unique physical and chemical properties. The principle and influence factors of hot filament CVD and plasma enhanced CVD preparation were interpreted by refereeing recent reports. Finally, recent developments that address electro-oxidation/reduction issues and novel electrodes such as nano-electrode and boron-doped diamond electrode (BDD) are presented in the overview.

  19. 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....

  20. Characterization of textile electrodes and conductors using standardized measurement setups

    International Nuclear Information System (INIS)

    Textile electrodes and conductors are being developed and used in different monitoring scenarios, such as ECG or bioimpedance spectroscopy measurements. Compared to standard materials, conductive textile materials offer improved wearing comfort and enable long-term measurements. Unfortunately, the development and investigation of such materials often suffers from the non-reproducibility of the test scenarios. For example, the materials are generally tested on human skin which is difficult since the properties of human skin differ for each person and can change within hours. This study presents two test setups which offer reproducible measurement procedures for the systematic analysis of textile electrodes and conductors. The electrode test setup was designed with a special skin dummy which allows investigation of not only the electrical properties of textile electrodes but also the contact behavior between electrode and skin. Using both test setups, eight textile electrodes and five textile conductors were analyzed and compared

  1. Reference Electrodes in Metal Corrosion

    OpenAIRE

    S. Szabó; Bakos, I.

    2010-01-01

    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 h...

  2. Capacitive de-ionization electrode

    Energy Technology Data Exchange (ETDEWEB)

    Daily, III, William D.

    2013-03-19

    An electrode "cell" for use in a capacitive deionization (CDI) reactor consists of the electrode support structure, a non-reactive conductive material, the electrode accompaniment or substrate and a flow through screen/separator. These "layers" are repeated and the electrodes are sealed together with gaskets between two end plates to create stacked sets of alternating anode and cathode electrodes in the CDI reactor.

  3. Nitrogen-doped reduced graphene oxide electrodes for electrochemical supercapacitors.

    Science.gov (United States)

    Nolan, Hugo; Mendoza-Sanchez, Beatriz; Ashok Kumar, Nanjundan; McEvoy, Niall; O'Brien, Sean; Nicolosi, Valeria; Duesberg, Georg S

    2014-02-14

    Herein we use Nitrogen-doped reduced Graphene Oxide (N-rGO) as the active material in supercapacitor electrodes. Building on a previous work detailing the synthesis of this material, electrodes were fabricated via spray-deposition of aqueous dispersions and the electrochemical charge storage mechanism was investigated. Results indicate that the functionalised graphene displays improved performance compared to non-functionalised graphene. The simplicity of fabrication suggests ease of up-scaling of such electrodes for commercial applications. PMID:24418938

  4. Effect of Electrode Configuration on Nitric Oxide Gas Sensor Behavior

    OpenAIRE

    Ling Cui; Erica P. Murray

    2015-01-01

    The influence of electrode configuration on the impedancemetric response of nitric oxide (NO) gas sensors was investigated for solid electrochemical cells [Au/yttria-stabilized zirconia (YSZ)/Au)]. Fabrication of the sensors was carried out at 1050 °C in order to establish a porous YSZ electrolyte that enabled gas diffusion. Two electrode configurations were studied where Au wire electrodes were either embedded within or wrapped around the YSZ electrolyte. The electrical response of the sen...

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

    Science.gov (United States)

    Mohebbi, Razie; Seyed-Yazdi, Jamileh

    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, TiO2) 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.

  6. Composite carbon foam electrode

    Science.gov (United States)

    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.

  7. Ion-selective electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Mikhelson, Konstantin N. [St. Petersburg State Univ. (Russian Federation). Ion-Selective Electrode Laboratory

    2013-06-01

    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 ISEs are outlined, and the transfer of methods into routine analysis is considered.

  8. 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

  9. Single Electrode Heat Effects

    DEFF Research Database (Denmark)

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

    1977-01-01

    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......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...

  10. Development of nanoporous gold electrodes for electrochemical applications

    DEFF Research Database (Denmark)

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

    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 analysis......, X-ray photo-electron spectroscopy and profilometer. The electrochemical performance of the np-Au electrodes was measured by cyclic voltammetry and electrochemical impedance spectroscopy. We have fabricated np-Au electrodes with pore sizes between 10 nm and 60 nm, directly related to the Ag:Au ratio...

  11. Kinetic Studies on Ni-YSZ Composite Electrodes

    DEFF Research Database (Denmark)

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

    2015-01-01

    carefully chosen cell geometry, methodology and operation conditions. Experimental The investigated cells consist of porous Ni/8YSZ composite working-electrodes with an active area between 0.8 and 1 mm2 and ~100 mm2 counter electrodes of the same material screen-printed on a special shaped 8YSZ electrolyte......Introduction Polarization of the Solid Oxide Cell (SOC) causes current to flow. If the fuel electrode is anodically polarized, the cell operates in fuel cell mode, oxidizing a fuel like hydrogen, carbon monoxide or hydrocarbons. In cathodic polarization the cell operates in electrolysis mode......, reducing steam, carbon dioxide or both at the fuel electrode. Independent of polarization direction, the current flowing through the electrodes of an SOC is limited by processes such as adsorption and desorption of reactants or products, diffusion through the porous electrodes, activation or charge...

  12. Development of Hydrogen Electrodes for Alkaline Water Electrolysis

    DEFF Research Database (Denmark)

    Kjartansdóttir, Cecilía Kristín

    gas based infrastructure. Alkaline water electrolysis (AWE) is the current standard (stat of the art) for industrial large-scale water electrolysis systems. One of the main criteria for industrial AWE is efficient and durable electrodes. The aim of the present PhD study was to develop electrode...... nickel hydrides in electrode metal lattice. The material degradation was considerably more severe at the anode compared to the cathode. The durability single-cell measurements indicate no deactivation of electrodes after shut-downs. Microstructure investigations on the PVD Al-Ni diffusion couples at 610......Ni3 phase. The diffusion mechanism can be the key to good properties of the developed PVD Al/Ni electrodes. Electrodes produced with shorter time of diffusion, 10-30 minutes, are found to be more prone to alkaline aluminium leaching and only 4-5 wt.% of aluminium residue is found in the leached...

  13. Validity of the Bruggeman relation for porous electrodes

    International Nuclear Information System (INIS)

    The ability to engineer electrode microstructures to increase power and energy densities is critical to the development of high-energy density lithium-ion batteries. Because high tortuosities in porous electrodes are linked to lower delivered energy and power densities, in this paper, we experimentally and computationally study tortuosity and consider possible approaches to decrease it. We investigate the effect of electrode processing on the tortuosity of in-house fabricated porous electrodes, using three-dimensionally reconstructed microstructures obtained by synchrotron x-ray tomography. Computer-generated electrodes are used to understand the experimental findings and assess the impact of particle size distribution and particle packing on tortuosity and reactive area density. We highlight the limitations and tradeoffs of reducing tortuosity and develop a practical set of guidelines for active material manufacture and electrode preparation. (paper)

  14. Carbon additives for electrical double layer capacitor electrodes

    Science.gov (United States)

    Weingarth, D.; Cericola, D.; Mornaghini, F. C. F.; Hucke, T.; Kötz, R.

    2014-11-01

    Electrochemical double layer capacitors (EDLCs) are inherently high power devices when compared to rechargeable batteries. While capacitance and energy storage ability are mainly increased by optimizing the electrode active material or the electrolyte, the power capability could be improved by including conductive additives in the electrode formulations. This publication deals with the use of four different carbon additives - two carbon blacks and two graphites - in standard activated carbon based EDLC electrodes. The investigations include: (i) physical characterization of carbon powder mixtures such as surface area, press density, and electrical resistivity measurements, and (ii), electrochemical characterization via impedance spectroscopy and cyclic voltammetry of full cells made with electrodes containing 5 wt.% of carbon additive and compared to cells made with pure activated carbon electrodes in organic electrolyte. Improved cell performance was observed in both impedance and cyclic voltammetry responses. The results are discussed considering the main characteristics of the different carbon additives, and important considerations about electrode structure and processability are drawn.

  15. Ultrasound Assisted Electrochemical Degradation of Cyanides: Influence of Electrode Type

    OpenAIRE

    IORDACHE, Ioan; NECHITA, Mircea Teodor; Rosca, Ioan; AELENEI, Nicolae

    2004-01-01

    The sonoelectrochemical degradation of cyanide ions (CN-) in the presence of 6 types of electrodes (aluminium, titanium, nickel, copper, stainless steel (inox), and graphite) were investigated in order to emphasise the influence of the electrode type on the efficiency of the degradation process.

  16. 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.

  17. Kinetic Studies on Ni-YSZ Composite Electrodes

    DEFF Research Database (Denmark)

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

    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...

  18. Phenol determination on HDTMA-bentonite-based electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Mojovic, Z., E-mail: zoricam@nanosys.ihtm.bg.ac.rs [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoseva 12, 11000 Belgrade (Serbia); Jovic-Jovicic, N.; Milutinovic-Nikolic, A.; Bankovic, P.; Rabi-Stankovic, A. Abu; Jovanovic, D. [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoseva 12, 11000 Belgrade (Serbia)

    2011-10-30

    Highlights: {yields} HDTMA-modified bentonites were tested as electrode materials in the electro-oxidation of phenol. {yields} The influences of the surfactant loading and pH of the supporting electrolyte were investigated. {yields} Rapid deactivation of electrodes occurred in an acidic environment. {yields} Good stability of the investigated electrodes was obtained in alkaline medium. {yields} The sensitivity toward phenol and stability of the electrodes was markedly improved with increasing HDTMA loading. - Abstract: The partial and complete substitution of cations in the interlayer region of clay with different amounts of hexadecyl trimethylammonium bromide (HDTMABr) was performed. The aim was to synthesize organo-bentonites to be used as constituents of porous electrodes for the electrooxidation of phenol. Domestic clay from Bogovina was subjected to a common procedure of the production of organo-bentonites. It included the following steps: grinding, sieving, Na-exchange, cation exchange and drying. The samples were characterized by X-ray diffraction (XRD) analysis, while the textural properties were evaluated by nitrogen physisorption. The multisweep cyclic voltammetry was applied to analyze the behavior of the clay modified glassy carbon electrode. The influences of the surfactant loading and pH of the support electrolyte were investigated. Rapid deactivation of electrodes occurred in an acidic environment, while good stability of the investigated electrodes was obtained in alkaline medium.

  19. Current and potential distributions on a cylinder electrode

    Energy Technology Data Exchange (ETDEWEB)

    Grabowski, A.J.

    1990-07-01

    This work presents the numerical solution for the current and potential distributions of a cylindrical electrode. In particular, it investigates the primary current distribution, the secondary current distribution with linearized kinetics, and the potential distribution due to constant current density on the working electrode. 16 refs., 19 figs.

  20. Flexible electrode belt for EIT using nanofiber web dry electrodes

    International Nuclear Information System (INIS)

    Efficient connection of multiple electrodes to the body for impedance measurement and voltage monitoring applications is of critical importance to measurement quality and practicality. Electrical impedance tomography (EIT) experiments have generally required a cumbersome procedure to attach the multiple electrodes needed in EIT. Once placed, these electrodes must then maintain good contact with the skin during measurements that may last several hours. There is usually also the need to manage the wires that run between the electrodes and the EIT system. These problems become more severe as the number of electrodes increases, and may limit the practicality and portability of this imaging method. There have been several trials describing human–electrode interfaces using configurations such as electrode belts, helmets or rings. In this paper, we describe an electrode belt we developed for long-term EIT monitoring of human lung ventilation. The belt included 16 embossed electrodes that were designed to make good contact with the skin. The electrodes were fabricated using an Ag-plated PVDF nanofiber web and metallic threads. A large contact area and padding were used behind each electrode to improve subject comfort and reduce contact impedances. The electrodes were incorporated, equally spaced, into an elasticated fabric belt. We tested the electrode belt in conjunction with the KHU Mark1 multi-frequency EIT system, and demonstrate time-difference images of phantoms and human subjects during normal breathing and running. We found that the Ag-plated PVDF nanofiber web electrodes were suitable for long-term measurement because of their flexibility and durability. Moreover, the contact impedance and stability of the Ag-plated PVDF nanofiber web electrodes were found to be comparable to similarly tested Ag/AgCl electrodes. (paper)

  1. 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.

  2. Electrodes the electrochemical supercapacitors

    Czech Academy of Sciences Publication Activity Database

    Kocian, M.; Vondrák, Jiří; Sedlaříková, M.

    Brno : University of Technology Brno, 2003, s. 109-111. ISBN 80-214-2298-X. [Advanced Batteries and Accumulators /4./. Brno (CZ), 15.06.2003-19.06.2003] Institutional research plan: CEZ:AV0Z4032918 Keywords : Electrodes Subject RIV: CA - Inorganic Chemistry

  3. Modified electrodes based on lipidic cubic phases.

    Science.gov (United States)

    Bilewicz, Renata; Rowiński, Paweł; Rogalska, Ewa

    2005-04-01

    The lipidic cubic phase can be characterized as a curved bilayer forming a three-dimensional, crystallographical, well-ordered structure that is interwoven by aqueous channels. It provides a stable, well-organized environment in which diffusion of both water-soluble and lipid-soluble compounds can take place. Cubic phases based on monoacylglycerols form readily and attract our interest due to their ability to incorporate and stabilize proteins. Their lyotropic and thermotropic phase behaviour has been thoroughly investigated. At hydration over 20%, lipidic cubic phases Ia3d and Pn3m are formed. The latter is stable in the presence of excess water, which is important when the cubic phase is considered as an electrode-modifying material. Due to high viscosity, the cubic phases can be simply smeared over solid substrates such as electrodes and used to host enzymes and synthetic catalysts, leading to new types of catalytically active modified electrodes as shown for the determination of cholesterol, CO(2), or oxygen. The efficiency of transport of small hydrophilic molecules within the film can be determined by voltametry using two types of electrodes: a normal-size electrode working in the linear diffusion regime, and an ultramicroelectrode working under spherical diffusion conditions. This allows determining both the concentration and diffusion coefficient of the electrochemically active probe in the cubic phase. The monoolein-based cubic phase matrices are useful for immobilizing enzymes on the electrode surface (e.g., laccases from Trametes sp. and Rhus vernicifera were employed for monitoring dioxygen). The electronic contact between the electrode and the enzyme was maintained using suitable electroactive probes. PMID:15833697

  4. The progress of nanocrystalline hydride electrode materials

    International Nuclear Information System (INIS)

    This paper reviews research at the Institute of Materials Science and Engineering, Poznan University of Technology, on the synthesis of nanocrystalline hydride electrode materials. Nanocrystalline materials have been synthesized by mechanical alloying (MA) followed by annealing. Examples of the materials include TiFe-, ZrV2-, LaNi5 and Mg2Ni-type phases. Details on the process used and the enhancement of properties due to the nanoscale structures are presented. The synthesized alloys were used as negative electrode materials for Ni-MH battery. The properties of hydrogen host materials can be modified substantially by alloying to obtain the desired storage characteristics. For example, it was found that the respective replacement of Fe in TiFe by Ni and/or by Cr, Co, Mo improved not only the discharge capacity but also the cycle life of these electrodes. The hydrogen storage properties of nanocrystalline ZrV2- and LaNi5-type powders prepared by mechanical alloying and annealing show no big difference with those of melt casting (polycrystalline) alloys. On the other hand, a partial substitution of Mg by Mn or Al in Mg2Ni alloy leads to an increase in discharge capacity, at room temperature. Furthermore, the effect of the nickel and graphite coating on the structure of some nanocrystalline alloys and the electrodes characteristics were investigated. In the case of Mg2Ni-type alloy mechanical coating with graphite effectively reduced the degradation rate of the studied electrode materials. The combination of a nanocrystalline TiFe-, ZrV2- and LaNi5-type hydride electrodes and a nickel positive electrode to form a Ni-MH battery, has been successful. (authors)

  5. Electrochemical micromachining of passive electrodes

    International Nuclear Information System (INIS)

    The electronic model describing the electrochemical micromachining (ECMM) of passive electrodes utilizing the transpassive dissolution is discussed. Numerical simulations are performed on a machining model circuit using measured electrochemical properties of the model system which consisted of a tungsten tool electrode, a 1 M H2SO4 electrolyte and a stainless steel work piece electrode. The results of these simulations were verified by performing machining experiments applying the same model system. For a passive stainless steel electrode it is shown that it can be treated like an actively dissolving electrode with high reaction overpotential. The efficiency of the machining process can be enhanced by polarizing the steel work piece electrode close to the transpassive potential region. Three different ways of achieving this polarization are discussed: by polarizing the work piece electrode only, by polarizing both electrodes and by adding oxidizing species to the electrolyte solution

  6. 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.

  7. 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

  8. 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.

  9. Beam profile shape of a parallel plane electrodes focusing system

    International Nuclear Information System (INIS)

    The present work investigates the potential distribution in a five electrodes lens to be used in an electrostatic ion source . The beam profile shape has been investigated using different gases The radii of the beam profile along the axial distance using nitrogen gas are calculated for different perveance, different initial beam radii, different ion charges and different ratios of the magnitude of voltage difference between the central electrode and the outer electrodes , Va , to the voltage corresponding to ion energy Vi . It has been found that a minimum beam radius of 0.22 mm can be obtained for initial beam radius equal 2.5 mm using nitrogen gas. The present lens constitutes a convergent lens. It gives a beam more focused than in case of two hemispherical electrodes and an intermediate flat electrode

  10. Effects of wall electrodes on Hall effect thruster plasma

    International Nuclear Information System (INIS)

    This paper investigates the physical mechanisms that cause beneficial and detrimental performance effect observed to date in Hall effect thrusters with wall electrodes. It is determined that the wall electrode sheath can reduce ion losses to the wall if positioned near the anode (outside the dense region of the plasma) such that an ion-repelling sheath is able to form. The ability of the wall electrode to form an ion-repelling sheath is inversely proportional to the current drawn—if the wall electrode becomes the dominant sink for the thruster discharge current, increases in wall electrode bias result in increased local plasma potential rather than an ion-repelling sheath. A single-fluid electron flow model gives results that mimic the observed potential structures and the current-sharing fractions between the anode and wall electrodes, showing that potential gradients in the presheath and bulk plasma come at the expense of current draw to the wall electrodes. Secondary electron emission from the wall electrodes (or lack thereof) is inferred to have a larger effect if the electrodes are positioned near the exit plane than if positioned near the anode, due to the difference in energy deposition from the plasma

  11. 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.

  12. Electromechanical properties of indium–tin–oxide/poly(3,4-ethylenedioxythiophene): Poly(styrenesulfonate) hybrid electrodes for flexible transparent electrodes

    International Nuclear Information System (INIS)

    We investigated an indium–tin–oxide (ITO)/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) hybrid electrode as a potential flexible and transparent electrode. In particular, the mechanical integrity of an ITO/PEDOT:PSS hybrid electrode deposited onto a polyethylene terephthalate (PET) substrate was investigated via outer/inner bending, twisting, stretching, and adhesion tests. A PEDOT:PSS layer was inserted between ITO and PET substrate as a buffer layer to improve the flexibility and electrical properties. When a PEDOT:PSS layer was inserted, the sheet resistance of the 20 nm-thick ITO film decreased from 270 Ω/square to 57 Ω/square. Notably, the ITO/PEDOT:PSS hybrid electrode had a constant resistance change (ΔR/R0) within an outer and inner bending radius of 3 mm. The bending fatigue test showed that the ITO/PEDOT:PSS hybrid electrode can withstand 10,000 bending cycles. Furthermore, the stretched ITO/PEDOT:PSS hybrid electrode showed a fairly constant resistance change up to 4%, which is more stable than the resistance change of the ITO electrode. The ITO/PEDOT:PSS electrode also shows good adhesion strength. The superior flexibility of the ITO/PEDOT:PSS hybrid electrode is attributed to the existence of a flexible PEDOT:PSS layer. This indicates that the hybridization of an ITO and PEDOT:PSS layer is a promising electrode scheme for next-generation flexible transparent electrodes. - Highlights: • We propose a hybrid electrode for flexible electronics. • Electrode made from In2O3:SnO2/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) • PEDOT:PSS as a buffer layer increases flexibility and electrical conductivity. • Hybrid electrode has a superior flexibility. • Hybrid electrode can be a promising flexible transparent electrode scheme

  13. Transparent Electrodes for Organic Solar Cells

    OpenAIRE

    Selzer, Franz

    2016-01-01

    The aim of this work was to investigate silver nanowire as well as carbon nanotube networks as transparent conducting electrodes for small molecule organic solar cells. In the framework of the nanowire investigations, a low-temperature method at less than 80 °C is developed to obtain highly conductive networks directly after the deposition and without post-processing. In detail, specific non-conductive organic materials act as a matrix where the nanowires are embedded in such that a mutua...

  14. Electrode array for neural stimulation

    Energy Technology Data Exchange (ETDEWEB)

    Wessendorf, Kurt O. (Albuquerque, NM); Okandan, Murat (Edgewood, NM); Stein, David J. (Albuquerque, NM); Yang, Pin (Albuquerque, NM); Cesarano, III, Joseph (Albuquerque, NM); Dellinger, Jennifer (Albuquerque, NM)

    2011-08-16

    An electrode array for neural stimulation is disclosed which has particular applications for use in a retinal prosthesis. The electrode array can be formed as a hermetically-sealed two-part ceramic package which includes an electronic circuit such as a demultiplexer circuit encapsulated therein. A relatively large number (up to 1000 or more) of individually-addressable electrodes are provided on a curved surface of a ceramic base portion the electrode array, while a much smaller number of electrical connections are provided on a ceramic lid of the electrode array. The base and lid can be attached using a metal-to-metal seal formed by laser brazing. Electrical connections to the electrode array can be provided by a flexible ribbon cable which can also be used to secure the electrode array in place.

  15. Flexible transparent electrode

    Science.gov (United States)

    Demiryont, Hulya; Shannon, Kenneth C., III; Moorehead, David; Bratcher, Matthew

    2011-06-01

    This paper presents the properties of the EclipseTECTM transparent conductor. EclipseTECTM is a room temperature deposited nanostructured thin film coating system comprised of metal-oxide semiconductor elements. The system possesses metal-like conductivity and glass-like transparency in the visible region. These highly conductive TEC films exhibit high shielding efficiency (35dB at 1 to 100GHz). EclipseTECTM can be deposited on rigid or flexible substrates. For example, EclipseTECTM deposited on polyethylene terephthalate (PET) is extremely flexible that can be rolled around a 9mm diameter cylinder with little or no reduction in electrical conductivity and that can assume pre-extension states after an applied stress is relieved. The TEC is colorless and has been tailored to have high visible transmittance which matches the eye sensitivity curve and allows the viewing of true background colors through the coating. EclipseTECTM is flexible, durable and can be tailored at the interface for applications such as electron- or hole-injecting OLED electrodes as well as electrodes in flexible displays. Tunable work function and optical design flexibility also make EclipseTECTM well-suited as a candidate for grid electrode replacement in next-generation photovoltaic cells.

  16. 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.

  17. Ambient pressure oxidation of Ag(111) surfaces : an in-situ X-ray study

    OpenAIRE

    Reicho, Alexander

    2008-01-01

    The oxidation of metals plays an outstanding role in everyday life. Typical phenomena are the formation of rust on steel or oxide scales on copper, showing up as a green patina. The formation of metal oxides is not always an unwanted process. The functionality of many materials is directly related to their controlled oxidation. The most prominent examples are passivating oxide layers on stainless steel. Relevant for this thesis are industrially applied heterogeneous catalytic reactions for th...

  18. 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

    interplay with molecule–substrate interactions is very subtle, making it difficult to single out the driving force for a nanoscale dislocation pattern. On the basis of a combined experimental and theoretical work, we here show that periodic dislocations in a molecular PFP film are mainly driven by the...... optimization of molecule–substrate interactions. Compared to inorganic networks however, it implies a much lower energy imbalance, allowing a thermally induced transition from a low-energy strain dislocation pattern to a high-energy incommensurate moiré....

  19. STM-imaging of nanostructure dynamics on Ag(111)-experimental challenges and solutions

    OpenAIRE

    Morgenstern, Karina; Rosenfeld, Georg; Poelsema, Bene; Comsa, George

    1996-01-01

    We describe experimental problems arising with the continuous observation of nanostructure dynamics by STM. We discuss the necessity to use a high-speed STM, possibilities to deal with the thermal drift, and tests to rule out the influence of the scanning process on the observation.

  20. 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...

  1. 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.

  2. Highly Stretchable and Flexible Graphene/ITO Hybrid Transparent Electrode.

    Science.gov (United States)

    Liu, Juhua; Yi, Yaohua; Zhou, Yihua; Cai, Huafei

    2016-12-01

    The flexible hybrid transparent electrode was prepared by a two-step process: graphene film was firstly grown on Cu foil by modified thermal chemical vapor deposition (CVD) and then transferred onto indium tin oxide (ITO) electrode on the polyethylene terephthalate (PET) substrate. The quality of the graphene is characterized by various analytic techniques, including the AFM, SEM, TEM, and Raman spectroscopy. The gradient flux was found to be beneficial to decrease defect. The thickness, morphology, light transmittance, and electromechanical properties of three conductive electrodes were investigated and compared. The outcomes show that the hybrid electrode could resist mechanical force and the results are better than original ITO electrode. It may be a potential trend to apply the graphene to other conducts in the flexible transparent conductive field. PMID:26920153

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

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard

    using 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....... 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. With...... a periodic model it is first shown that these tall electrodes introduce several new confined SAW modes with slow phase velocities because of mechanical energy storage in the electrodes. The periodic model is then extended to a finite model by using perfectly matched layers at the substrate borders...

  4. Analysis and Modelling of Electrode Wear in Resistance Spot Welding

    DEFF Research Database (Denmark)

    Madsen, Anders; Pedersen, Kim; Friis, Kasper Storgaard;

    2010-01-01

    -processing program written in MatLab. Very fine agreement between the present experimental results and previously published wear data is achieved. Finally the pitted areas on the electrode tip are analyzed using MatLab and an optical 3D surface measurement device. Two types of pitting are characterized. One where a...... central cavity is formed and one where smaller pits are formed randomly across the electrode face. The influence of these two types of surface pits on the nugget size are investigated using the FE code SORPAS, revealing ring welds and undersized weld nuggets.......A model describing electrode wear as a function of weld number, initial tip diameter, truncated cone angle, welding current and electrode force is proposed. Excellent agreement between the model and experimental results is achieved, showing that the model can describe the change in electrode tip...

  5. 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.

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

    International Nuclear Information System (INIS)

    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

  7. 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.

  8. Highly Stretchable and Flexible Graphene/ITO Hybrid Transparent Electrode

    Science.gov (United States)

    Liu, Juhua; Yi, Yaohua; Zhou, Yihua; Cai, Huafei

    2016-02-01

    The flexible hybrid transparent electrode was prepared by a two-step process: graphene film was firstly grown on Cu foil by modified thermal chemical vapor deposition (CVD) and then transferred onto indium tin oxide (ITO) electrode on the polyethylene terephthalate (PET) substrate. The quality of the graphene is characterized by various analytic techniques, including the AFM, SEM, TEM, and Raman spectroscopy. The gradient flux was found to be beneficial to decrease defect. The thickness, morphology, light transmittance, and electromechanical properties of three conductive electrodes were investigated and compared. The outcomes show that the hybrid electrode could resist mechanical force and the results are better than original ITO electrode. It may be a potential trend to apply the graphene to other conducts in the flexible transparent conductive field.

  9. Compliant composite electrodes and large strain bistable actuation

    Science.gov (United States)

    Yun, Sungryul; Yu, Zhibin; Niu, Xiaofan; Hu, Weili; Li, Lu; Brochu, Paul; Pei, Qibing

    2012-04-01

    Dielectric elastomer actuators (DEA) and bistable electroactive polymers (BSEP) both require compliant electrodes with rubbery elasticity and high conductivity at large strains. Stretchable opto-electronic devices additionally require the compliant electrodes to be optically transparent. Many candidate materials have been investigated. We report a new approach to mechanically robust, stretchable compliant electrodes. A facile in-situ composite synthesis and transfer technique is employed, and the resulting composite electrodes retain the high surface conductivity of the original conductive network formed by nanowires or nanotubes, while exhibiting the mechanical flexibility of the matrix polymer. The composite electrodes have high transparency and low surface roughness useful for the fabrication of polymer thinfilm electronic devices. The new electrodes are suitable for high-strain actuation, as a complaint resistive heating element to administer the temperature of shape memory polymers, and as the charge injection electrodes for flexible/stretchable polymer light emitting diodes. Bistable electroactive polymers employing the composite electrodes can be actuated to large strains via heating-actuation-cooling cycles.

  10. Arc Behaviours in Vacuum Interrupters with Axial Magnetic Field Electrodes

    Institute of Scientific and Technical Information of China (English)

    WANG Zhongyi; ZHENG Yuesheng; LIU Zhiyuan; CHENG Shaoyong

    2008-01-01

    To improve the limiting current interruption capability and minimizing vacuum interrupter with axial magnetic field (AMF) electrodes,it is significant to investigate the vacuum arc behaviours between the contacts.AMF distributions of the slot type electrodes were studied by both numerical analysis and experiments. Furthermore,the behaviours of vacuum arcs for different parameters of the slot type AMF electrodes were investigated by using high-speed CCD camera.The influences of gap distance,contact diameter and phase shift time between AMF and arc current on the vacuum arc were investigated.The results provide a reference for research and development of vacuum interrupters with slot type or other types of AMF electrode.

  11. 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.

  12. 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. PMID:27013949

  13. Boron-doped nanocrystalline diamond electrodes for neural interfaces: In vivo biocompatibility evaluation

    Directory of Open Access Journals (Sweden)

    María eAlcaide

    2016-03-01

    Full Text Available 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.

  14. 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. PMID:27013949

  15. Effect of electrode geometry on photovoltaic performance of polymer solar cells

    Science.gov (United States)

    Li, Meng; Ma, Heng; Liu, Hairui; Wu, Dongge; Niu, Heying; Cai, Wenjun

    2014-10-01

    This paper investigates the impact of electrode geometry on the performance of polymer solar cells (PSCs). The negative electrodes with equal area (0.09 cm2) but different shape (round, oval, square and triangular) are evaluated with respect to short-circuit current density, open-circuit voltage, fill factor and power conversion efficiency of PSCs. The results show that the device with round electrodes gives the best photovoltaic performance; in contrast, the device with triangular electrodes reveals the worst properties. A maximum of almost a 19% increase in power conversion efficiency with a round electrode is obtained in the devices compared with that of the triangular electrode. To conclude, the electrode boundary curvature has a significant impact on the performance of PSCs. The larger curvature, i.e. sharper electrodes edges, perhaps has a negative effect on exciton separation and carrier transport in photoelectric conversion processes.

  16. Effect of electrode geometry on photovoltaic performance of polymer solar cells

    International Nuclear Information System (INIS)

    This paper investigates the impact of electrode geometry on the performance of polymer solar cells (PSCs). The negative electrodes with equal area (0.09 cm2) but different shape (round, oval, square and triangular) are evaluated with respect to short-circuit current density, open-circuit voltage, fill factor and power conversion efficiency of PSCs. The results show that the device with round electrodes gives the best photovoltaic performance; in contrast, the device with triangular electrodes reveals the worst properties. A maximum of almost a 19% increase in power conversion efficiency with a round electrode is obtained in the devices compared with that of the triangular electrode. To conclude, the electrode boundary curvature has a significant impact on the performance of PSCs. The larger curvature, i.e. sharper electrodes edges, perhaps has a negative effect on exciton separation and carrier transport in photoelectric conversion processes. (paper)

  17. 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.

  18. 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 0.1mol/dm(3) phosphate buffer (PBS) solution of pH7.0. 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. PMID:26952453

  19. 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

  20. Field testing of sulphide electrodes

    International Nuclear Information System (INIS)

    Sulphide ion selective electrodes have been developed at BARC, for determination of Ag+ and S- ions directly and Cl- and CN- ions indirectly. The electrodes were tested for their use in sulphide environments in the EAD (Effluent After Dilution) stream at the Heavy Water Plant, Kota. The electrodes are suitable in the concentration range of 16000 ppm to 0.002 ppm, with a slope of 29-31 mV per decade change in the sulphide ion concentration. The response time is less than 10 seconds. These electrodes are reliable for continuous on-line use for a long period. (author). 7 refs., 11 figs., 1 tab

  1. Electro-oxidation treatment of Sn/PANI electrode and electrocatalytic activity of Pt/Sn hydroxide/PANI composite electrodes

    Institute of Scientific and Technical Information of China (English)

    ZHOU Hai-hui; PENG Zheng; JIAO Yong-gang; LIAO Jie; KUANG Ya-fei

    2008-01-01

    After being electro-oxidized by cyclic voltammetry(CV) method in 0.5 mol/L H2504 solution or in 0.2mol/L H2O2+0.5 mol/L H2SO4 solution, the Sn/polyaniline (PANI) electrodes were modified with Pt microparticles by pulse galvanostatic method, thus Pt/Sn hydroxide/PANI electrodes were prepared. The electrocatalytic activities of the Pt/Sn/PANI electrode and Pt/Sn hydroxide/PANI electrode for formaldehyde electro-oxidation were investigated by CV method. The effects of deposition charges (Qdep) of PANI, Sn and Pt, scan rate and formaldehyde concentration on the electrocatalytic activity of Pt/Sn hydroxide/PANI electrode were also studied. The results show that the electrocatalytic activities of the Pt/Sn hydroxide/PANI electrodes are much higher than those of the Pt/Sn/PANI electrode.

  2. DIFFUSION IN BIOFILMS RESPIRING ON ELECTRODES

    OpenAIRE

    Renslow, RS; Babauta, JT; Majors, PD; Beyenal, H

    2012-01-01

    The goal of this study was to measure spatially and temporally resolved effective diffusion coefficients (De) in biofilms respiring on electrodes. Two model electrochemically active biofilms, Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1, were investigated. A novel nuclear magnetic resonance microimaging perfusion probe capable of simultaneous electrochemical and pulsed-field gradient nuclear magnetic resonance (PFG-NMR) techniques was used. PFG-NMR allowed noninvasive, nondestr...

  3. Lithium Manganese Silicate Positive Electrode Material

    OpenAIRE

    Yang, Qiong

    2014-01-01

    As the fast development of the electronic portable devices and drastic fading of fossil energy sources. The need for portable secondary energy sources is increasingly urgent. As a result, lithium ion batteries are being investigated intensely to meet the performance requirements. Among various electrode materials, the most expensive and capacity limiting component is the positive materials. Based on this, researches have been mostly focused on the development of novel cathode materials with ...

  4. High density plasma productions by hydrogen storage electrode in the Tohoku University Heliac

    International Nuclear Information System (INIS)

    In the Tohoku University Heliac (TU-Heliac), the influence of a radial electric field on improved modes has been investigated by an electrode biasing. In both positive and negative biasing experiments by the stainless steel (SUS) electrode (cold-electron or ion collection), the improvement of plasma confinement was clearly observed. Furthermore, by negative biasing with a hot cathode (electron injection), the radial electric fields can be actively controlled as a consequence of the control of the electrode current IE. By using the electrode made of a hydrogen storage metal, for example Titanium (Ti) or Vanadium (V), the following possibility can be expected: (1) ions accelerated from the positive biased electrode allow the simulation for the orbit loss of high-energy particles, (2) the electrons/neutral- particles injected from the negative biased electrode provide the production of the high- density plasma, if hydrogen are successfully stored in the electrode. In this present work, several methods were tried as the treatment for hydrogen storage. In the case of the Ti electrode biased positively after the treatment, the improvement of plasma confinement was observed in He plasma, which were same as the experimental results of the SUS electrode. However, in the electron density profiles inside the electrode position there was difference between the biased plasma by the Ti electrode and that by the SUS electrode. In some of Ar discharges biased negatively with the Ti electrode after the treatment, the electron density and the line intensity of Hα increased about 10 times of those before biasing. This phenomenon has not been observed in the Ar plasma biased by the SUS electrode. This result suggested that the Ti electrode injected electrons/neutral-hydrogen into the plasma. This high-density plasma productions were observed only 1 ∼ 3 times in the one treatment for hydrogen storage. By using a Vanadium (V) electrode, productions of the high-density plasma, which

  5. 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.

  6. ORGANIC ELECTRODE COATINGS FOR NEXT-GENERATION NEURAL INTERFACES

    Directory of Open Access Journals (Sweden)

    Rylie A Green

    2014-05-01

    Full Text Available 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.

  7. 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. PMID:24904405

  8. 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

  9. 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.

  10. Foil electrode sper light source

    International Nuclear Information System (INIS)

    Numerous laser transitions in the visible and near-infrared in four metal vapors (Li, Al, Ca, and Cu) have been observed in the recombination phase of the expanding plasmas produced by a segmented plasma device employing foil electrodes. Also described is a segmented vapor plasma discharge in using Ni foil electrodes

  11. EDM Electrode for Internal Grooves

    Science.gov (United States)

    Ramani, V.; Werner, A.

    1985-01-01

    Electroerosive process inexpensive alternative to broaching. Hollow brass electrodes, soldered at one end to stainless-steel holding ring, held in grooves in mandrel. These electrodes used to machine grooves electrically in stainless-steel tube three-eights inch (9.5 millimeters) in diameter. Tool used on tubes already in place in equipment.

  12. 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.

  13. Electrohydrodynamically induced flow direction in a wire-non-parallel plate electrode corona discharge

    Energy Technology Data Exchange (ETDEWEB)

    Chang, J S [McIARS and Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Ueno, J [Department of Electrical Engineering, Osaka City University, Osaka 558-8585 (Japan); Tsubone, H [Department of Mechanical Engineering, Ariake National College of Technology, Omuta, Fukuoka 836-8585 (Japan); Harvel, G D [McIARS and Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Minami, S [Department of Electrical Engineering, Osaka City University, Osaka 558-8585 (Japan); Urashima, K [McIARS and Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)

    2007-09-07

    An experimental investigation has been conducted to study the net flow direction induced by electrohydrodynamic forces in a wire-non-parallel plate electrode corona discharge. The experiments were conducted at two different locations of corona wire electrode for negative and positive applied voltage from 0 to 14 kV at atmospheric pressure and room temperature, where air was used as the working fluid. It was experimentally revealed that the net flow direction of electrohydrodynamically induced gas flow in a wire-non-parallel plate electrode system was changed depending on the location of the corona wire electrode relative to the grounded electrode position.

  14. 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

  15. Tungsten oxide in polymer electrolyte fuel cell electrodes-A thin-film model electrode study

    Energy Technology Data Exchange (ETDEWEB)

    Wickman, Bjoern, E-mail: bjorn.wickman@chalmers.s [Competence Centre for Catalysis, Department of Applied Physics, Chalmers University of Technology, SE-412 96 Goeteborg (Sweden); Wesselmark, Maria; Lagergren, Carina; Lindbergh, Goeran [Applied Electrochemistry, School of Chemical Science and Engineering, KTH, SE-100 44 Stockholm (Sweden)

    2011-10-30

    Highlights: > Platinum and tungsten oxide thin-film electrocatalysts. > Single cell fuel cell evaluation. > Hydrogen-tungsten bronze formation. > CO oxidation on platinum on tungsten oxide. - Abstract: Thin films of WO{sub x} and Pt on WO{sub x} were evaporated onto the microporous layer of a gas diffusion layer (GDL) and served as model electrodes in the polymer electrolyte fuel cell (PEFC) as well as in liquid electrolyte measurements. In order to study the effects of introducing WO{sub x} in PEFC electrodes, precise amounts of WO{sub x} (films ranging from 0 to 40 nm) with or without a top layer of Pt (3 nm) were prepared. The structure of the thin-film model electrodes was characterized by scanning electron microscopy and X-ray photoelectron spectroscopy prior to the electrochemical investigations. The electrodes were analyzed by cyclic voltammetry and the electrocatalytic activity for hydrogen oxidation reaction (HOR) and CO oxidation was examined. The impact of Nafion in the electrode structure was examined by comparing samples with and without Nafion solution sprayed onto the electrode. Fuel cell measurements showed an increased amount of hydrogen tungsten bronzes formed for increasing WO{sub x} thicknesses and that Pt affected the intercalation/deintercalation process, but not the total amount of bronzes. The oxidation of pre-adsorbed CO was shifted to lower potentials for WO{sub x} containing electrodes, suggesting that Pt-WO{sub x} is a more CO-tolerant catalyst than Pt. For the HOR, Pt on thicker films of WO{sub x} showed an increased limiting current, most likely originating from the increased electrochemically active surface area due to proton conductivity and hydrogen permeability in the WO{sub x} film. From measurements in liquid electrolyte it was seen that the system behaved very differently compared to the fuel cell measurements. This exemplifies the large differences between the liquid electrolyte and fuel cell systems. The thin-film model

  16. 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.

  17. 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...

  18. Electrostatic actuation of nanomechanical optical fibres with integrated electrodes

    OpenAIRE

    Podoliak, N.; Lian, Zhenggang; Segura, Martha; Loh, W H; Horak, P.

    2014-01-01

    We investigate theoretically and experimentally the possibility of electrostatic actuation of nanomechanical optical fibers with integrated electrodes. The fiber has two optically guiding cores suspended in air by thin flexible membranes. This fiber structure allows for control of the optical properties via nanometer-range mechanical core movements. The electrostatic actuation of the fiber is generated by electrically charged electrodes embedded in the fiber cladding. Fiber designs with one t...

  19. Performance Analysis in Pacemaker Electrode and Study Effect Electric Resistance

    OpenAIRE

    S. Iman Zonoori , Elaheh Nikkhah Bahrami; Zahra Bahrami; Shahin Rezvani Abravani

    2014-01-01

    — In recent years, there has been an increasing use pacemaker electrode that is placed inside the heart and helps the patient’s heart to keep a normal rhythm. In this paper, performance of pacemaker electrode and electric resistance are investigated. These structures are modelled and numerically tested by using Finite Element Method (FEM) by using Comsol Multiphysics. The created virtual models using 3D simulation and computation software proved that used shiel...

  20. Separation of tryptophan enantiomers with molecularly imprinted polypyrrole electrode column

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In this study,we have fabricated molecularly imprinted polypyrrole(PPy) packed electrode columns and investigated their effects on separation of tryptophan(Trp) enantiomers by using potential control.The results indicate that the imprinted PPy electrode columns could efficiently enhance the L-Trp uptake and separate Trp enantiomers effectively,implying the great potential for the enantioselective recognition of other amino acids enantiomers.

  1. Nitrogen-doped reduced graphene oxide electrodes for electrochemical supercapacitors

    OpenAIRE

    NOLAN, HUGO; Mendoza-Sanchez, Beatriz; Ashok Kumar, Nanjundan; McEvoy, Niall; O'Brien, Sean; NICOLOSI, VALERIA; Duesberg, Georg S.

    2014-01-01

    Herein we use Nitrogen-doped reduced Graphene Oxide (N-rGO) as the active material in supercapacitor electrodes. Building on a previous work detailing the synthesis of this material, electrodes were fabricated via spray-deposition of aqueous dispersions and the electrochemical charge storage mechanism was investigated. Results indicate that the functionalised graphene displays improved performance compared to non-functionalised graphene. The simplicity of fabrication suggests ease of up-scali...

  2. Cochlear Implant Rate Pitch and Melody Perception as a Function of Place and Number of Electrodes

    Science.gov (United States)

    Marimuthu, Vijay; Mannell, Robert

    2016-01-01

    Six Nucleus cochlear implant recipients participated in a study investigating the effect of place of stimulation on melody perception using rate-pitch cues. Each stimulus was a pulse train delivered on either a single electrode or multiple electrodes sequentially. Four spatial stimulation patterns were used: a single apical electrode, a single mid electrode, a pair of electrodes (apical and mid), and 11 electrodes (from apical to mid). Within one block of trials, all stimuli had the same spatial stimulation pattern, with pulse rate varying from 131 to 262 pps. An additional pulse rate range of 262 to 523 pps was tested with the single-electrode stimuli. Two experimental procedures were used: note ranking; and a modified melodies test with backwards and warp modification. In each trial of the modified melodies test, a familiar melody and a version with modified pitch were presented (in random order), and the subject’s task was to select the unmodified melody. There were no significant differences in performance for stimulation on 1, 2, or 11 electrodes, implying that recipients were unable to combine temporal information from different places in the cochlea to give a stronger pitch cue. No advantage of apical electrodes was found: at the lower pulse rates, there were no significant differences between electrodes; and at the higher pulse rates, scores on the apical electrode dropped more than those on the mid electrode. PMID:27094028

  3. 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. PMID:26764786

  4. 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.

  5. 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.

  6. Electrochemical degradation of chlorobenzene on boron-doped diamond and platinum electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Liu Lei [Department of Chemistry, Tongji University, Shanghai, 200092 (China); Zhao Guohua, E-mail: g.zhao@tongji.edu.cn [Department of Chemistry, Tongji University, Shanghai, 200092 (China); Wu Meifen; Lei Yanzhu; Geng Rong [Department of Chemistry, Tongji University, Shanghai, 200092 (China)

    2009-08-30

    In this paper the electrochemical degradation of chlorobenzene (CB) was investigated on boron-doped diamond (BDD) and platinum (Pt) anodes, and the degradation kinetics on these two electrodes was compared. Compared with the total mineralization with a total organic carbon (TOC) removal of 85.2% in 6 h on Pt electrode, the TOC removal reached 94.3% on BDD electrode under the same operate condition. Accordingly, the mineralization current efficiency (MCE) during the mineralization on BDD electrode was higher than that on the Pt electrode. Besides TOC, the conversion of CB, the productions and decay of intermediates were also monitored. Kinetic study indicated that the decay of CB on BDD and Pt electrodes were both pseudo-first-order reactions, and the reaction rate constant (k{sub s}) on BDD electrode was higher than that on Pt electrode. The different reaction mechanisms on the two electrodes were investigated by the variation of intermediates concentrations. Two different reaction pathways for the degradation of CB on BDD electrode and Pt electrode involving all these intermediates were proposed.

  7. Electrochemical degradation of chlorobenzene on boron-doped diamond and platinum electrodes.

    Science.gov (United States)

    Liu, Lei; Zhao, Guohua; Wu, Meifen; Lei, Yanzhu; Geng, Rong

    2009-08-30

    In this paper the electrochemical degradation of chlorobenzene (CB) was investigated on boron-doped diamond (BDD) and platinum (Pt) anodes, and the degradation kinetics on these two electrodes was compared. Compared with the total mineralization with a total organic carbon (TOC) removal of 85.2% in 6h on Pt electrode, the TOC removal reached 94.3% on BDD electrode under the same operate condition. Accordingly, the mineralization current efficiency (MCE) during the mineralization on BDD electrode was higher than that on the Pt electrode. Besides TOC, the conversion of CB, the productions and decay of intermediates were also monitored. Kinetic study indicated that the decay of CB on BDD and Pt electrodes were both pseudo-first-order reactions, and the reaction rate constant (k(s)) on BDD electrode was higher than that on Pt electrode. The different reaction mechanisms on the two electrodes were investigated by the variation of intermediates concentrations. Two different reaction pathways for the degradation of CB on BDD electrode and Pt electrode involving all these intermediates were proposed. PMID:19264395

  8. Influence on discharge uniformity of electrodes configuration

    CERN Document Server

    Zheng Jian; Sui Zhan; Lu Jing Ping; Zheng Kui Xing; Zhang Xiong Jun; Dong Yun; Feng Bin

    2002-01-01

    Large area glow discharge plasma that is transparent and highly conductive can be used as electrodes in Pockels cell to extend the switch aperture. To investigate this technology, a glow discharging chamber with a clear aperture of 5 cm x 5 cm was constructed, and hollow cathode, button cathode, pin cathode, bar cathode and bar anode were designed and produced. Using CCD imaging system, the discharging uniformity of different cathodes was tested with bar anode and under the different pressure pre-ionization voltage and main discharging voltage. A uniform plasma can be obtained with a hollow cathode when the pre-ionization voltage is about 700 V, the pressure is about 30 Pa, and the main discharging voltage is about 4 kV, which can be used for the plasma electrode of Pockels cell

  9. MHD Electrode and wall constructions

    Science.gov (United States)

    Way, Stewart; Lempert, Joseph

    1984-01-01

    Electrode and wall constructions for the walls of a channel transmitting the hot plasma in a magnetohydrodynamic generator. The electrodes and walls are made of a plurality of similar modules which are spaced from one another along the channel. The electrodes can be metallic or ceramic, and each module includes one or more electrodes which are exposed to the plasma and a metallic cooling bar which is spaced from the plasma and which has passages through which a cooling fluid flows to remove heat transmitted from the electrode to the cooling bar. Each electrode module is spaced from and electrically insulated from each adjacent module while interconnected by the cooling fluid which serially flows among selected modules. A wall module includes an electrically insulating ceramic body exposed to the plasma and affixed, preferably by mechanical clips or by brazing, to a metallic cooling bar spaced from the plasma and having cooling fluid passages. Each wall module is, similar to the electrode modules, electrically insulated from the adjacent modules and serially interconnected to other modules by the cooling fluid.

  10. Capacitance enhancement via electrode patterning.

    Science.gov (United States)

    Ho, Tuan A; Striolo, Alberto

    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. PMID:24289370

  11. Modified nickel electrodes: a review

    International Nuclear Information System (INIS)

    Catalysts in the form of electrode surfaces offer the added dimension of the electrode potential which can be used to manage the catalyst reactivity and in some cases selectivity. The catalytic effect of nickel oxyhydroxide for the electrochemical determination of organics in alkaline media is very common. This has also received substantial thought because of the application of Ni in rechargeable alkaline batteries. This subject matter has been reviewed from different views before. The present review depicts the role of additives and the modifiers towards the enhancement of electro catalytic properties of electrode surface. (author)

  12. 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.

  13. 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.

  14. Design and Manufacture of Silver-Selective Electrode Based on Single-Walled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Khoorshid Mehdizadeh

    2015-06-01

    Full Text Available The present research explores the design and manufacture of coated ion-selective membranes on graphite electrodes with selectivity towards silver cations.Single- walled carbon nanotube N-6- aminohexylamide ,was used as the ionophore.The electrode was manufactured in a concentration range of 1×10-6to1×10-2 , , resulting in a Nernst response with a gradient of 59.1±0.5 mv/decade . In this work, the effects of membrane composition, pH of the solution, temperature and non-aqueous environment were investigated on the performance of the electrodes Furthermore, the response time of the electrode and the electrode response reversibility were calculated using both static and dynamic methods. This electrode can be applied in ethanol environments of up to 25% and in dioxane environments of up to 25% volume-volume without hindrance. The electrode response time was less than 18 seconds.

  15. 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.

  16. 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.

  17. 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.

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

    DEFF Research Database (Denmark)

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

    2013-01-01

    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...... 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 is...... comparable to devices with evaporated back electrodes. We further confi rm that inkjet printing represent an effi cient alternative to screen printing....

  19. Flexible electrochromic films based on CVD-graphene electrodes

    Science.gov (United States)

    Choi, Dong Soo; Han, Seung Ho; Kim, Hyeongkeun; Kang, So Hee; Kim, Yena; Yang, Cheol-Min; Kim, Tae Young; Yoon, Dae Ho; Yang, Woo Seok

    2014-09-01

    Graphene synthesized via chemical vapor deposition is a notable candidate for flexible large-area transparent electrodes due to its great physical properties and its 2D activated surface area. Electrochromic devices in optical displays, smart windows, etc are suitable applications for graphene when used as a transparent conductive electrode. In this study, various-layer graphene was synthesized via chemical vapor deposition, and inorganic WOx was deposited on the layers, which have advantageous columnar structures and W6+ and W4+ oxidation states. The characteristics of graphene and WOx were verified using optical transmittance, Raman spectroscopy, x-ray photoelectron spectroscopy and scanning electron microscopy. The optimum transparent conductive electrode condition for controlling graphene layers was investigated based on the optical density and cyclic voltammetry. Electrochromic devices were fabricated using a three-layer graphene electrode, which had the best optical density. The graphene in the flexible electrochromic device demonstrated a potential for replacing ITO in flexible electronics.

  20. Flexible electrochromic films based on CVD-graphene electrodes

    International Nuclear Information System (INIS)

    Graphene synthesized via chemical vapor deposition is a notable candidate for flexible large-area transparent electrodes due to its great physical properties and its 2D activated surface area. Electrochromic devices in optical displays, smart windows, etc are suitable applications for graphene when used as a transparent conductive electrode. In this study, various-layer graphene was synthesized via chemical vapor deposition, and inorganic WOx was deposited on the layers, which have advantageous columnar structures and W6+ and W4+ oxidation states. The characteristics of graphene and WOx were verified using optical transmittance, Raman spectroscopy, x-ray photoelectron spectroscopy and scanning electron microscopy. The optimum transparent conductive electrode condition for controlling graphene layers was investigated based on the optical density and cyclic voltammetry. Electrochromic devices were fabricated using a three-layer graphene electrode, which had the best optical density. The graphene in the flexible electrochromic device demonstrated a potential for replacing ITO in flexible electronics. (paper)

  1. Study of molybdenum electrodes for hydrogen evolution reaction

    Energy Technology Data Exchange (ETDEWEB)

    Padilha, Janine Carvalho; Martini, Emilse Maria Agostini; Brum, Caua; de Souza, Michele Oberson; de Souza, Roberto Fernando [Institute of Chemistry, UFRGS, Av. Bento Goncalves, 9500, Porto Alegre, 91501-970, P.O. Box 15003 (Brazil)

    2009-10-20

    The molybdenum electrode, Mo, has been investigated for hydrogen production via water electrolysis in 10 vol.% aqueous solutions of 1-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF{sub 4}) using electrochemical impedance spectroscopy (EIS). The EIS measurements show that the Mo system has much higher interfacial capacitance, and correspondently the electrical double layer formed on this electrode is thicker than those formed on nickel or platinum. The positive displacement of potential of zero charge (PZC) values indicates the specific adsorption of the imidazolium cation on the Mo surface. This study provides an elegant explanation for the better performance of Mo electrodes in the hydrogen evolution reaction (HER): the BMI cation acts as an intermediate for the proton transfer from water to the electrode surface, thereby decreasing the overpotential of HER. This model explains the synergism between Mo and the BMI cation in the HER process. (author)

  2. The design of pig stunning tong electrodes-A review.

    Science.gov (United States)

    Sparrey, J M; Wotton, S B

    1997-09-01

    The effectiveness of current electrical stunning systems for pigs is discussed and the need for improvements in the design and construction of stunning tongs and electrodes are explored. A review of existing stunning tong electrodes for use with free standing or restrained pig is discussed. The potential problems with existing systems are highlighted as: (1) the profile of the pigs head precludes the application of existing electrodes in the correct position; (2) the small area of contact enhances carbon build-up which increases electrical impedance; (3) the electrodes are easily tarnished with few cleaning tools provided. Good tong positions that span the brain are described as between the eye and ear on each side of the head, below the ear on each side of the head or, diagonal application between the top and bottom of the head. The notional contact impedance is the major component of resistance to current flow within the stunning system. The proposed use of different electrode designs and constructional material is investigated. The effect of the introduction of the fail-safe device would be to heighten the interest in contact impedance within the plant and that could ensure that the investigation of different electrodes is explored at least at plant level. PMID:22062623

  3. Electronic structure and excited state dynamics in optically excited PTCDA films investigated with two-photon photoemission

    Science.gov (United States)

    Marks, M.; Sachs, S.; Schwalb, C. H.; Schöll, A.; Höfer, U.

    2013-09-01

    We present an investigation of the electronic structure and excited state dynamics of optically excited 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) thin films adsorbed on Ag(111) using two-photon photoemission spectroscopy (2PPE). 2PPE allows us to study both occupied and unoccupied electronic states, and we are able to identify signals from the highest occupied and the two lowest unoccupied electronic states of the PTCDA thin film in the 2PPE spectra. The energies for occupied states are identical to values from ultraviolet photoelectron spectroscopy. Compared to results from inverse photoelectron spectroscopy (IPES), the 2PPE signals from the two lowest unoccupied electronic states, LUMO and LUMO+1, are found at 0.8 eV and 1.0 eV lower energies, respectively. We attribute this deviation to the different final states probed in 2PPE and IPES and the attractive interaction of the photoexcited electron and the remaining hole. Furthermore, we present a time-resolved investigation of the excited state dynamics of the PTCDA film in the femtosecond time regime. We observe a significantly shorter inelastic excited state lifetime compared to findings from time-resolved photoluminescence spectroscopy of PTCDA single crystals which could originate from excitation quenching by the metal substrate.

  4. Advances in Studies of Electrode Kinetics and Mass Transport in AMTEC Cells (abstract)

    Science.gov (United States)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; Kisor, A.; O'Connor, D.; Kikkert, S.

    1993-01-01

    Previous work reported from JPL has included characterization of electrode kinetics and alkali atom transport from electrodes including Mo, W, WRh(sub x), WPt(sub x)(Mn), in sodium AMTEC cells and vapor exposure cells, and Mo in potassium vapor exposure cells. These studies were generally performed in cells with small area electrodes (about 1 to 5 cm(sup 2)), and device geometry had little effect on transport. Alkali diffusion coefficients through these electrodes have been characterized, and approximate surface diffusion coefficients derived in cases of activated transport. A basic model of electrode kinetic at the alkali metal vapor/porous metal electrode/alkali beta'-alumina solid electrolyte three phase boundary has been proposed which accounts for electrochemical reaction rates with a collision frequency near the three phase boundary and tunneling from the porous electrode partially covered with adsorbed alkali metal atoms. The small electrode effect in AMTEC cells has been discussed in several papers, but quantitative investigations have described only the overall effect and the important contribution of electrolyte resistance. The quantitative characterization of transport losses in cells with large area electrodes has been limited to simulations of large area electrode effects, or characterization of transport losses from large area electrodes with significant longitudinal temperature gradients. This paper describes new investigations of electrochemical kinetics and transport, particularily with WPt(sub 3.5) electrodes, including the influence of electrode size on the mass transport loss in the AMTEC cell. These electrodes possess excellent sodium transport properties making verification of device limitations on transport much more readily attained.

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

    International Nuclear Information System (INIS)

    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/m2, 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/m2, 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.

  6. 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.

  7. A Hydrogen Ion-Selective Poly(Vinyl Chloride) Membrane Electrode Based on Calix[4]arene as a Perchlorate Ion-Selective Electrode

    OpenAIRE

    CANEL, Esin; ERDEN, Sevcan; ÖZEL, Ayça DEMİREL; MEMON, Sahahabuddin

    2008-01-01

    A hydrogen ion-selective electrode was prepared using 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetracyanometoxy-calix[4]arene and the possibility of its use as a perchlorate ion-selective electrode was investigated using its characteristic of becoming perchlorate sensitive in acidic regions. The electrode of the optimum characteristic had a composition of 1% ionophore, 66% o-NPOE, and 33% PVC. This electrode exhibited a linear response over the range 1.0 \\times 10-1-1.0 \\times 10-5 M o...

  8. Laser patterning of platinum electrodes for safe neurostimulation

    Science.gov (United States)

    Green, R. A.; Matteucci, P. B.; Dodds, C. W. D.; Palmer, J.; Dueck, W. F.; Hassarati, R. T.; Byrnes-Preston, P. J.; Lovell, N. H.; Suaning, G. J.

    2014-10-01

    Objective. Laser surface modification of platinum (Pt) electrodes was investigated for use in neuroprosthetics. Surface modification was applied to increase the surface area of the electrode and improve its ability to transfer charge within safe electrochemical stimulation limits. Approach. Electrode arrays were laser micromachined to produce Pt electrodes with smooth surfaces, which were then modified with four laser patterning techniques to produce surface structures which were nanosecond patterned, square profile, triangular profile and roughened on the micron scale through structured laser interference patterning (SLIP). Improvements in charge transfer were shown through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and biphasic stimulation at clinically relevant levels. A new method was investigated and validated which enabled the assessment of in vivo electrochemically safe charge injection limits. Main results. All of the modified surfaces provided electrical advantage over the smooth Pt. The SLIP surface provided the greatest benefit both in vitro and in vivo, and this surface was the only type which had injection limits above the threshold for neural stimulation, at a level shown to produce a response in the feline visual cortex when using an electrode array implanted in the suprachoroidal space of the eye. This surface was found to be stable when stimulated with more than 150 million clinically relevant pulses in physiological saline. Significance. Critical to the assessment of implant devices is accurate determination of safe usage limits in an in vivo environment. Laser patterning, in particular SLIP, is a superior technique for improving the performance of implant electrodes without altering the interfacial electrode chemistry through coating. Future work will require chronic in vivo assessment of these electrode patterns.

  9. 钴酸锰/泡沫镍复合电极材料的制备及其电化学性能研究%Fabrication of MnCo2O4/nickel foam electrodes and the investigation of their electrochemical properties

    Institute of Scientific and Technical Information of China (English)

    张杰; 许家胜; 王琳; 钱建华

    2016-01-01

    利用两步法成功制备出两种MnCo2O4纳米等级结构材料,研究了其电化学性能。结果证实得到的纳米片为 MnCo2O4纳米等级结构,并均匀生长在泡沫镍基底上,电化学性质测试表明,这种纳米片/泡沫镍复合电极表现出优异的电化学性质。这种优异的性质与介孔的MnCo2O4纳米片这一新颖的结构有密切的关系,5 A/g时的比电容值高达475 F/g。MnCo2O4/泡沫镍复合材料是一种非常有潜力的超级电容电极材料,MnCo2O4纳米材料结构和形貌对超级电容器电极材料的电化学性质有较大的影响。%Two kinds of MnCo2O4 hierarchical structures were uniformly grown on Ni foam via a facile two-step method. These electrode materials were directly used as the integrated electrode for supercapacitors. The electrochemical properties were investigated. These MnCo2O4/Ni foam electrodes exhibit ultrahigh capacitance because of these unique nanostructures. The specific capacitance value is 475 F/g at current density of 5 A/g. The structure and morphology of MnCo2O4 nanomaterials play an important role in the electrochemical performance of the supercapacitor materials and the MnCo2O4/Ni foam electrode could be a great potential material for the supercapacitor in industry.

  10. Composite Electrodes for Electrochemical Supercapacitors

    OpenAIRE

    Yang QuanMin; Li Jun; Zhitomirsky Igor

    2010-01-01

    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 to...

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

    OpenAIRE

    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...

  12. Expansion and shrinkage of the sulfur composite electrode in rechargeable lithium batteries

    Energy Technology Data Exchange (ETDEWEB)

    He, Xiangming; Ren, Jianguo; Wang, Li; Pu, Weihua; Jiang, Changyin; Wan, Chunrong [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China)

    2009-05-01

    The expansion and shrinkage characteristics of sulfur composite cathode electrode in rechargeable lithium batteries have been investigated. It was found that the sulfur composites electrodes expanded when discharging and shrank when charging again. The thickness change of the electrode was measured to be about 22%. The thickness of lithium metal anodes was also changed when lithium deposition and dissolution, while the sulfur composites electrodes expanded and shrank conversely. The investigation showed that the thickness changes of lithium anode and sulfur composite cathode could be compensated with each other to keep the total thickness of the cell not to change so much. (author)

  13. Diffusion in biofilms respiring on electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Renslow, Ryan S. [Washington State Univ., Pullman, WA (United States); Babauta, Jerome T. [Washington State Univ., Pullman, WA (United States); Majors, Paul D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Beyenal, Haluk [Washington State Univ., Pullman, WA (United States)

    2012-11-15

    The goal of this study was to measure spatially and temporally resolved effective diffusion coefficients (De) in biofilms respiring on electrodes. Two model electrochemically active biofilms, Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1, were investigated. A novel nuclear magnetic resonance microimaging perfusion probe capable of simultaneous electrochemical and pulsed-field gradient nuclear magnetic resonance (PFG-NMR) techniques was used. PFG-NMR allowed for noninvasive, nondestructive, high spatial resolution in situ De measurements in living biofilms respiring on electrodes. The electrodes were polarized so that they would act as the sole terminal electron acceptor for microbial metabolism. We present our results as both two-dimensional De heat maps and surface-averaged relative effective diffusion coefficient (Drs) depth profiles. We found that (1) Drs decreases with depth in G. sulfurreducens biofilms, following a sigmoid shape; (2) Drs at a given location decreases with G. sulfurreducens biofilm age; (3) average De and Drs profiles in G. sulfurreducens biofilms are lower than those in S. oneidensis biofilms—the G. sulfurreducens biofilms studied here were on average 10 times denser than the S. oneidensis biofilms; and (4) halting the respiration of a G. sulfurreducens biofilm decreases the De values. Density, reflected by De, plays a major role in the extracellular electron transfer strategies of electrochemically active biofilms.

  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. [Experience in developing and using capacitive electrodes].

    Science.gov (United States)

    Grishanovich, A P; Iarmolinskiĭ, V I

    1984-01-01

    A capacitive-type electrode using titanium or tantalum oxide obtained through anodizing is described. Incorporated in the electrode is a source for a buffer amplifier. A shielding cap is used as an indifferent electrode. High performance allows using the electrodes for ECG, EEG, and other signal recording in clinical practice and researches. PMID:6708763

  16. 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.

  17. Multiscale porous fuel cell electrodes

    Science.gov (United States)

    Wen, Hao

    Porous electrodes are widely used in fuel cells to enhance electrode performance due to their high surface area. Increasingly, such electrodes are designed with both micro-scale and nano-scale features. In the current work, carbon based porous materials have been synthesized and utilized as bioelectrode support for biofuel cells, analysis of such porous electrodes via rotating disk electrode has been enhanced by a numerical model that considers diffusion and convection within porous media. Finally, porous perovskite metal oxide cathodes for solid oxide fuel cell have been modeled to simulate impedance response data obtained from symmetric cells. Carbon fiber microelectrodes (CFME) were fabricated to mimic the microenvironment of carbon fiber paper based porous electrodes. They were also miniature electrodes for small-scale applications. As observed by scanning electron microscopy (SEM), carbon nanotubes (CNTs) formed a homogeneously intertwined matrix. Biocatalysts can fully infiltrate this matrix to form a composite, with a significantly enhanced glucose oxidation current---that is 6.4 fold higher than the bare carbon fiber electrodes. Based on the CNT based porous matrix, polystyrene beads of uniform diameter at 500 nm were used as template to tune the porous structure and enhance biomolecule transport. Focused ion beam (FIB) was used to observe the morphology both at the surface and the cross-section. It has been shown that the template macro-pores enhanced the fuel transport and the current density has been doubled due to the improvement. Like commonly used rotating disk electrode, the porous rotating disk electrode is a system with analytically solved flow field. Although models were proposed previously with first order kinetics and convection as the only mass transport at high rotations, some recent findings indicated that diffusion could play an important role at all disk rotation rates. In the current proposed model, enzymatic kinetics that follow a Ping

  18. A Biosensor Using Poly(4-Aminophenol)/acetylcholinesterase modified graphite electrode for the detection of dichlorvos

    OpenAIRE

    Edmar Isaías Melo; Diego Leoni Franco; André Santiago Afonso; Hélen Cristine Rezende; Ana Graci Brito-Madurro; João Marcos Madurro; Nívia Maria Melo Coelho

    2011-01-01

    The properties of poly(4-aminophenol) modified graphite electrode as material for the immobilization of acetylcholinesterase were investigated by the Cyclic Voltammetry, Electrochemical Impedance Spectroscopy and Atomic Force Microscopy. The polymer was deposited on graphite electrode surface by the oxidation of 4-aminophenol and then acetylcholinesterase was immobilized on the surface of the electrode. The biosensor coupled in the continuous flow system was employed for the detection of dich...

  19. Chargеs collection efficiency in gamma-ray detectors with different electrodes configuration

    Directory of Open Access Journals (Sweden)

    Kondrik A. I.

    2012-08-01

    Full Text Available The dependence of the charge collection efficiency n in gamma-ray detectors based on CdZnTe on the impurity composition of the material has been investigated. Plane-parallel, cylindrical and spherical electrodes have been considered. A comparative analysis of n for detectors with electrodes of different shape has been carried out and the optimum composition of the material CdxZn1–xTe placed in the electrode gap has been determined.

  20. Influence of electrode, buffer gas and control gear on metal halide lamp performance

    International Nuclear Information System (INIS)

    In this paper the influence of electrode composition, buffer gas fill pressure and control gear on the performance of metal halide lamps is investigated. It is shown that pure tungsten electrodes improve lumen maintenance and reduce voltage rise over lamp life. An optimum buffer gas fill pressure condition is discovered which allows for reduced electrode erosion during lamp starting as well as under normal operating conditions. Use of electronic control gear is shown to improve the performance of metal halide lamps

  1. Effects of Vestibular Prosthesis Electrode Implantation and Stimulation on Hearing in Rhesus Monkeys

    OpenAIRE

    Dai, Chenkai; Fridman, Gene Y.; Della Santina, Charles C.

    2010-01-01

    To investigate the effects of vestibular prosthesis electrode implantation and activation on hearing in rhesus monkeys, we measured auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE) in four rhesus monkeys before and after unilateral implantation of vestibular prosthesis electrodes in each of 3 left semicircular canals (SCC). Each of the 3 left SCCs were implanted with electrodes via a transmastoid approach. Right ears, which served as controls, were not s...

  2. Effect of electrode geometry on photovoltaic performance of polymer solar cells

    OpenAIRE

    Li, Meng; Ma, Heng; Wang, Zhaokui; Wang, Chuankun; Jiang, Yurong; Liu, Ning

    2013-01-01

    This paper investigates the impact of electrode geometry on the performance of polymer solar cells (PSCs). Four types of negative electrodes with equal area (0.09 cm2) but different shape (round, oval, square, and triangular) are evaluated with respect to short-circuit current density, open-circuit voltage, fill factor, and power conversion efficiency of PSCs. The results show that the device with round electrodes gives the best photovoltaic performance; in contrast, the device with triangula...

  3. Inkjet printed ECG electrodes for long term biosignal monitoring in personalized and ubiquitous healthcare

    OpenAIRE

    John C. Batchelor and Alexander J. Casson

    2015-01-01

    This paper investigates the performance of inkjet printed electrodes for electrocardiogram (ECG) monitoring in personalized and ubiquitous healthcare. As a rapid prototyping, additive manufacturing approach, inkjet printing can allow personalization of electrode sizes and shapes and can be used with a range of substrates to achieve good long term connections to the skin. We compare the performance of two types of inkjet electrodes printed using different substrates. Results demonstrate that b...

  4. Influence of electrode site and size on variability of magnetic evoked potentials.

    Science.gov (United States)

    Dunnewold, R J; van der Kamp, W; van den Brink, A M; Stijl, M; van Dijk, J G

    1998-12-01

    Successive magnetic evoked potentials (MEPs) concern varying motor neurons. We investigated whether this MEP-specific source of variability depends on electrode site and size. Amplitude variability (standard deviation) was largest over the center of the hypothenar muscles. Latencies were longer at distal and proximal sites than at the center site. Large electrodes (10 cm2) did not decrease this source of amplitude variability compared with EEG electrodes, in contrast to other sources of variability. PMID:9843083

  5. Monolayers and multilayers of chlorophyll [correction of chlorophyl] a on a mercury electrode.

    Science.gov (United States)

    Moncelli, M R; Becucci, L; Dolfi, A; Tadini Buoninsegni, F; Agostiano, A

    2002-05-15

    A novel experimental technique used to investigate chlorophyll films on a hanging mercury drop electrode is described. Two different procedures are employed to prepare self-assembled chlorophyll monolayers and multilayers on the mercury electrode. Upon illuminating the chlorophyll a (Chl)-coated mercury electrode with an appropriate light source, the photocurrents generated by the Chl aggregates are measured under short-circuit conditions in the absence of photoartefacts. The preliminary results obtained by this novel technique are presented. PMID:12009465

  6. Polyaniline-graphite composite film glucose oxidase electrode

    Institute of Scientific and Technical Information of China (English)

    ZHOU Hai-hui; CHEN Hong; CHEN Jin-hua; KUANG Ya-fei

    2006-01-01

    A novel polyaniline-graphite composite film glucose oxidase (PGCF GOD) electrode was developed. The PGCF was synthesized by cyclic voltammetry method in 0.5 mol/L H2SO4 solution containing 1 g/L graphite powder and 0.2 mol/L aniline. The PGCF GOD electrode was prepared by doping GOD into the composite film. The morphology of the PGCF and the response property of the PGCF GOD electrode were investigated by scanning electron microscopy and electrochemical measurement,respectively. The results show that the PGCF has a porous and netty structure and the PGCF GOD electrode has excellent response property such as high sensitivity and short response time. Influences of pH value, temperature, glucose concentration and potential on the response current of the electrode were also discussed. The sensor has a maximum steady-state current density of 357.17 tA/cm2and an apparent Michaelis-Menten constant of 16.57 mmol/L. The maximum current response of the enzyme electrode occurs under the condition of pH 5.5, 0.8 V and 65 ℃.

  7. Supercapacitor Electrodes from Activated Carbon Monoliths and Carbon Nanotubes

    Science.gov (United States)

    Dolah, B. N. M.; Othman, M. A. R.; Deraman, M.; Basri, N. H.; Farma, R.; Talib, I. A.; Ishak, M. M.

    2013-04-01

    Binderless monoliths of supercapacitor electrodes were prepared by the carbonization (N2) and activation (CO2) of green monoliths (GMs). GMs were made from mixtures of self-adhesive carbon grains (SACG) of fibers from oil palm empty fruit bunches and a combination of 5 & 6% KOH and 0, 5 & 6% carbon nanotubes (CNTs) by weight. The electrodes from GMs containing CNTs were found to have lower specific BET surface area (SBET). The electrochemical behavior of the supercapacitor fabricated using the prepared electrodes were investigated by electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD). In general an addition of CNTs into the GMs reduces the equivalent series resistance (ESR) value of the cells. A cell fabricated using electrodes from GM with 5% CNT and 5% KOH was found to have the largest reduction of ESR value than that from the others GMs containing CNT. The cell has steeper Warburg's slope than that from its respective non-CNT GM, which reflect the smaller resistance for electrolyte ions to move into pores of electrodes despite these electrodes having largest reduction in specific BET surface area. The cell also has the smallest reduction of specific capacitance (Csp) and maintains the specific power range despite a reduction in the specific energy range due to the CNT addition.

  8. 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. PMID:26765041

  9. Effect of Electrode Configuration on Nitric Oxide Gas Sensor Behavior

    Directory of Open Access Journals (Sweden)

    Ling Cui

    2015-09-01

    Full Text Available The influence of electrode configuration on the impedancemetric response of nitric oxide (NO gas sensors was investigated for solid electrochemical cells [Au/yttria-stabilized zirconia (YSZ/Au]. Fabrication of the sensors was carried out at 1050 °C in order to establish a porous YSZ electrolyte that enabled gas diffusion. Two electrode configurations were studied where Au wire electrodes were either embedded within or wrapped around the YSZ electrolyte. The electrical response of the sensors was collected via impedance spectroscopy under various operating conditions where gas concentrations ranged from 0 to 100 ppm NO and 1%–18% O2 at temperatures varying from 600 to 700 °C. Gas diffusion appeared to be a rate-limiting mechanism in sensors where the electrode configuration resulted in longer diffusion pathways. The temperature dependence of the NO sensors studied was independent of the electrode configuration. Analysis of the impedance data, along with equivalent circuit modeling indicated the electrode configuration of the sensor effected gas and ionic transport pathways, capacitance behavior, and NO sensitivity.

  10. 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...

  11. 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

  12. 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

  13. Diffusional transport to and through thin-layer nanoparticle film modified electrodes: capped CdSe nanoparticle modified electrodes.

    Science.gov (United States)

    Hepburn, William G; Batchelor-McAuley, Christopher; Tschulik, Kristina; Barnes, Edward O; Kachoosangi, Roohollah Torabi; Compton, Richard G

    2014-09-01

    We present a simple and general theoretical model which accounts fully for the influence of an electrode modifying non-electroactive layer on the voltammetric response of a diffusional redox probe. The layer is solely considered to alter the solubilities and diffusion coefficients of the electroactive species within the thin layer on the electrode surface. On this basis it is demonstrated how, first, the apparent electrochemical rate constant can deviate significantly from that measured at an unmodified electrode. Second, depending on the conditions within the layer the modification of the electrode may lead to either apparent 'negative' or 'positive' electrocatalytic effects without the true standard electrochemical rate constant for the electron transfer at the electrode surface being altered. Having presented the theoretical model three experimental cases are investigated, specifically, the reductions of ruthenium(III) hexaamine, oxygen and boric acid on a gold macro electrode with and without a multi-layer organic capped nanoparticle film. In the latter case of the reduction of boric acid the voltammetric reduction is found to be enhanced by the presence of the organic layer. This result is interpreted as being due to an increase in the solubility of the analyte within the non-electroactive layer and not due to an alteration of the standard electrochemical rate constant. PMID:25050481

  14. 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...... materials as candidates for robust oxygen sensor electrodes. The present work focuses on characterising the electrochemical properties of a few electrode materials to understand which oxygen electrode processes are limiting for the response time of the sensor electrode. Three types of porous platinum......-Dansensor. The electrochemical properties of the electrodes were characterised by electrochemical impedance spectroscopy (EIS), and the structures were characterised by x-ray diffraction and electron microscopy. At an oxygen partial pressures of 0.2 bar, the response time of the sensor electrode was determined by oxygen...

  15. Impedance based automatic electrode positioning.

    Science.gov (United States)

    Miklody, Daniel; Hohne, Johannes

    2015-08-01

    The position of electrodes in electrical imaging and stimulation of the human brain is an important variable with vast influences on the precision in modeling approaches. Nevertheless, the exact position is obscured by many factors. 3-D Digitization devices can measure the distribution over the scalp surface but remain uncomfortable in application and often imprecise. We demonstrate a new approach that uses solely the impedance information between the electrodes to determine the geometric position. The algorithm involves multidimensional scaling to create a 3 dimensional space based on these impedances. The success is demonstrated in a simulation study. An average electrode position error of 1.67cm over all 6 subjects could be achieved. PMID:26736345

  16. 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...

  17. Composite Electrodes for Electrochemical Supercapacitors

    Science.gov (United States)

    Li, Jun; Yang, Quan Min; Zhitomirsky, Igor

    2010-03-01

    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.

  18. 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.

  19. Electrochemical cell and electrode designs for high-temperature/high-pressure kinetic measurements

    International Nuclear Information System (INIS)

    Many corrosion processes of interest to the nuclear power industry occur in high-temperature/high-pressure aqueous systems. The investigation of the kinetics of the appropriate electrode reactions is a serious experimental challenge, partially because of the high temperatures and pressures and partially because many of these reactions are very rapid, requiring fast relaxation measurements. An electrochemical measuring system is described which is suitable for measurements of the kinetics of fast electrode reactions at temperatures extending to at least 3000C and pressures to at least 10 MPa (100 atmospheres). The system includes solution preparation and handling equipment, the electrochemical cell, and several electrode designs. One of the new designs is a coaxial working electrode-counter electrode assembly; this electrode can be used with very fast-rising pulses, and it provides a well defined, repeatedly-polishable working surface. Low-impedance reference electrodes are also described, based on electrode concepts responding to the pH or the redox potential of the test solution. Additionally, a novel, long-life primary reference electrode design is reported, based on a modification of the external, pressure-balanced Ag/AgCl reference electrode

  20. Enhancing biocompatibility of some cation selective electrodes using heparin modified bacterial cellulose.

    Science.gov (United States)

    Badr, Ibrahim H A; Abdel-Sattar, R; Keshk, Sherif M A S

    2015-12-10

    Bacterial cellulose (BC) and heparin-modified bacterial cellulose (HBC) were utilized to enhance the biocompatibility of highly thrombogenic PVC-based potassium and calcium membrane electrodes. Three types of membrane electrodes were prepared: (1) conventional PVC electrode (control), (2) PVC-based electrode sandwiched with bacterial cellulose membrane (BC-PVC), and (3) PVC-based electrode sandwiched with heparin-modified bacterial cellulose membrane (HBC-PVC). The potentiometric response characteristics of the modified potassium and calcium membrane electrodes (BC-PVC and HBC-PVC) were compared with those of the control PVC-based potassium and calcium selective electrode, respectively. Response characteristics of the modified membrane electrodes were comparable to the control PVC membrane electrode. The platelet adhesion investigations indicated that (BC) and (HBC) layers are less thrombogenic compared to PVC. Therefore, use of BC or HBC would enable the enhancement of the biocompatibility of PVC-based membrane electrodes for potassium and calcium while practically maintaining the overall electrochemical performance of the PVC sensing film. PMID:26428173

  1. A study of the electrochemical behaviour of electrodes in operating solid-state supercapacitors

    International Nuclear Information System (INIS)

    The electrochemical behaviour of electrodes and of complete solid-state supercapacitors has been studied by cyclic voltammetry (CV) and galvanostatic charge/discharge (CD) measurements using two independent electrochemical equipments. The first one controlled the execution of the test and recorded the voltage and current values of the complete supercapacitor while the other one recorded the potential changes of the single electrodes. In this work, two different types of capacitors were studied: (a) a symmetric supercapacitor using carbon electrodes, and (b) a hybrid (asymmetric) supercapacitor with ruthenium oxide/carbon in the positive electrode and carbon in the negative electrode. The studies evidenced that in the symmetric capacitors the positive electrode controlled the capacitive performance and an optimal mass ratio from 1.2:1 to 1.3:1 between the positive and the negative electrodes was found in the investigated conditions. For the hybrid supercapacitor it was observed that the ruthenium-based positive electrode influenced the capacitive performance of carbon-based negative electrode and that an accurate balance of carbon loading in the negative electrode was necessary

  2. A study of the electrochemical behaviour of electrodes in operating solid-state supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Staiti, P.; Lufrano, F. [CNR-ITAE, Istituto di Tecnologie Avanzate per l' Energia ' ' Nicola Giordano' ' , Messina (Italy)

    2007-12-01

    The electrochemical behaviour of electrodes and of complete solid-state supercapacitors has been studied by cyclic voltammetry (CV) and galvanostatic charge/discharge (CD) measurements using two independent electrochemical equipments. The first one controlled the execution of the test and recorded the voltage and current values of the complete supercapacitor while the other one recorded the potential changes of the single electrodes. In this work, two different types of capacitors were studied: (a) a symmetric supercapacitor using carbon electrodes, and (b) a hybrid (asymmetric) supercapacitor with ruthenium oxide/carbon in the positive electrode and carbon in the negative electrode. The studies evidenced that in the symmetric capacitors the positive electrode controlled the capacitive performance and an optimal mass ratio from 1.2:1 to 1.3:1 between the positive and the negative electrodes was found in the investigated conditions. For the hybrid supercapacitor it was observed that the ruthenium-based positive electrode influenced the capacitive performance of carbon-based negative electrode and that an accurate balance of carbon loading in the negative electrode was necessary. (author)

  3. Synthesis and characterization of tin oxide/carbon aerogel composite electrodes for electrochemical supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Sung-Woo; Hyun, Sang-Hoon [School of Advanced Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-749 (Korea)

    2007-10-11

    Two types of carbon aerogel-based functional electrodes for supercapacitor applications are developed. To improve the electrochemical performance of the electrodes, carbon aerogels are doped with pseudocapacitive tin oxide either by impregnating tin oxide sol into resorcinol-formaldehyde (RF) wet gels (Method I), or by impregnating tin tetrachloride solution into carbon aerogel electrodes (Method II). The electrodes are heat-treated to 450 C in air to activate the electrode surface and complete the oxidation of tin-precursors in the network structure of the aerogel. The effects of different impregnation methods on the physical/electrochemical properties of the composite electrodes are investigated. Microstructural and compositional variations of the electrodes with tin oxide doping are also examined by scanning electron microscopy and energy dispersive X-ray analysis. The tin oxide/carbon aerogel composite electrodes synthesized by both methods have similar specific capacitances (66-70 F g{sup -1}). Composite electrodes synthesized via Method II showed better cyclic stability compared with electrodes synthesized via Method I. (author)

  4. Dye-sensitized solar cells based on low cost carbon-coated tungsten disulphide counter electrodes

    International Nuclear Information System (INIS)

    Highlights: •Carbon-coated WS2 films are used as the counter electrode in dye-sensitized solar cells. •The plastic carbon-coated WS2 counter electrodes are prepared at room temperature. •The device with carbon-coated WS2 electrode exhibits comparable performance to that of the cell with Pt electrode. -- Abstract: Carbon-coated tungsten disulphide (WS2) is synthesized using a simple method and characterized with X-ray diffraction, field emission scanning electron microscopy and laser Raman spectrum. The WS2-based counter electrodes for dye-sensitized solar cells (DSSCs) are prepared at low temperature. The electrochemical catalytic activity of the WS2 counter electrodes is investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The DSSCs assembled with carbon-coated WS2 counter electrodes show a photovoltaic conversion efficiency of 5.5%, which is comparable to that of the DSSCs based on Pt electrode (5.6%). Plastic WS2 counter electrodes are also prepared which give a photovoltaic conversion efficiency of 5.0%. Our study indicates that carbon-coated WS2 is a good candidate to replace the Pt counter electrodes in DSSCs

  5. Preparation of carbonaceous electrodes and evaluation of their performance by electrochemical techniques

    International Nuclear Information System (INIS)

    Carbonaceous electrodes, from glassy carbon (GC), graphite rod or graphite powder, have been prepared for coulometric and voltammetric investigation. Beaker type graphite electrode of larger surface area was used as working electrode for the analysis of uranium and plutonium in solution by coulometry. Results have shown usefulness of the electrode for both uranium and plutonium analysis. Thus the graphite electrode can be used in place of mercury for uranium analysis and in place of platinum gauze for plutonium analysis. GC electrode ( from French and Indian material ), graphite or carbon paste electrode of smaller surface area prepared here have also been found to give satisfactory performance as could be observed from cyclic voltammetric (cv) patterns for standard K9Fe(CN)6/K4Fe(CN)6 redox system. Especially the GC electrode, (French) polished to 1μ finish with diamond paste gave very low values (1μ amp.) of background current in 1M KCl and the difference in cathodic and anodic peak potentials (δE values) was close to 60 mV from one electron transfer. Therefore the electrode can be used for various types of electrochemical studies relating to redox potentials, reaction mechanism, kinetic parameters etc. of different electrode processes. (author). 20 refs., 3 tabs., 10 figs., 8 photographs

  6. Nanofiber membrane-electrode-assembly and method of fabricating same

    Science.gov (United States)

    Pintauro, Peter N.; Ballengee, Jason; Brodt, Matthew

    2016-02-02

    In one aspect of the present invention, a fuel cell membrane-electrode-assembly (MEA) has an anode electrode, a cathode electrode, and a membrane disposed between the anode electrode and the cathode electrode. At least one of the anode electrode, the cathode electrode and the membrane is formed of electrospun nanofibers.

  7. 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.

  8. Ceramic components for MHD electrode

    Science.gov (United States)

    Marchant, D.D.

    A ceramic component which exhibits electrical conductivity down to near room temperatures has the formula: Hf/sub x/In/sub y/A/sub z/O/sub 2/ where x = 0.1 to 0.4, y = 0.3 to 0.6, z = 0.1 to 0.4 and A is a lanthanide rare earth or yttrium. The component is suitable for use in the fabrication of MHD electrodes or as the current leadout portion of a composite electrode with other ceramic components.

  9. Properties of Ag/AgCl electrodes fabricated with IC-compatible technologies

    OpenAIRE

    Bousse, L.J.; Bergveld, P.; Geeraedts, H.J.M.

    1986-01-01

    The purpose of this work is to fabricate and characterize Ag/AgCl electrodes made on a silicon chip at the wafer level with integrated circuit-compatible fabrication techniques. Such electrodes are useful as reference electrodes in several kinds of chemical sensors. Two types of electrode were investigated. The first type uses an evaporated AgCl layer that is patterned with lift-off photolithography. The second type is formed by exposing a selected part of the silver substrate to a KCrO3Cl so...

  10. Electrochemical Epitaxial Growth of a Pt(111) Phase on an Au(111) Electrode

    OpenAIRE

    Uosaki, Kohei; Ye, Shen; Naohara, Hideo; Oda, Yasuhiro; Haba, Toshio; KONDO, Toshihiro

    1997-01-01

    The electrochemical deposition of platinum on an Au(111) single-crystal electrode in acidic solutions containing H2PtCl6 was studied using an electrochemical scanning tunneling microscope (STM) and electrochemical quartz crystal microbalance (EQCM). The STM investigation showed an ordered adlayer of PtCl6^[2-] on the electrode surface during the electrochemical deposition of platinum and a Pt(111)-(1x1) structure on the electrode surface after the electrode was rinsed with a Pt complex-free s...

  11. Graphene oxide-modified electrodes for sensitive determination of diethylstilbestrol

    Science.gov (United States)

    Yu, Chunmei; Ji, Wanyu; Wang, Yidan; Bao, Ning; Gu, Haiying

    2013-03-01

    This paper reports an electrochemical sensor fabricated with graphene oxide (GO) modified on a chitosan-coated glassy carbon electrode (GO-CS/GCE) and its application for the detection of diethylstilbestrol (DES). It was observed that the effective electrochemical surface area of the GO modified electrode was nearly 10 times that of the bare GCE. This could be used to explain the results that the oxidation peak current of DES on the GO-CS/GCE was much larger than on the bare GCE. Under optimized conditions, the prepared electrode could be used to electrochemically detect DES according to the oxidation of the DES. Based on the technique of differential pulse voltammetry and the accumulation of DES on GO modified electrodes, the calibration curve for DES determination could be obtained with a linear range of 1.5 × 10-8-3.0 × 10-5 M and an estimated detection limit of 3.0 × 10-9 M (S/N = 3). The feasibility of the developed electrode for tablet sample analysis was investigated. Our investigation revealed that GO could significantly improve the analytical performance of electrochemical sensors.

  12. Graphene oxide-modified electrodes for sensitive determination of diethylstilbestrol

    International Nuclear Information System (INIS)

    This paper reports an electrochemical sensor fabricated with graphene oxide (GO) modified on a chitosan-coated glassy carbon electrode (GO-CS/GCE) and its application for the detection of diethylstilbestrol (DES). It was observed that the effective electrochemical surface area of the GO modified electrode was nearly 10 times that of the bare GCE. This could be used to explain the results that the oxidation peak current of DES on the GO-CS/GCE was much larger than on the bare GCE. Under optimized conditions, the prepared electrode could be used to electrochemically detect DES according to the oxidation of the DES. Based on the technique of differential pulse voltammetry and the accumulation of DES on GO modified electrodes, the calibration curve for DES determination could be obtained with a linear range of 1.5 × 10−8–3.0 × 10−5 M and an estimated detection limit of 3.0 × 10−9 M (S/N = 3). The feasibility of the developed electrode for tablet sample analysis was investigated. Our investigation revealed that GO could significantly improve the analytical performance of electrochemical sensors. (paper)

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

    DEFF Research Database (Denmark)

    Jacobsen, Torben

    $mm diameter) platinum electrodes mounted in a thin alumina tube resting on a polished 8 mol\\% yttria stabilized zirconia electrolyte at $1000^\\circ$C in air. The results where analysed in terms of the equivalent circuit $R_{YSZ}(R_r Q)$ in the frequency range 0.5MHz--1kHz. Fig.\\,1 shows...

  14. The activity of nanocrystalline Fe-based alloys as electrode materials for the hydrogen evolution reaction

    Science.gov (United States)

    Müller, Christian Immanuel; Sellschopp, Kai; Tegel, Marcus; Rauscher, Thomas; Kieback, Bernd; Röntzsch, Lars

    2016-02-01

    In view of alkaline water electrolysis, the activities for the hydrogen evolution reaction of nanocrystalline Fe-based electrode materials were investigated and compared with the activities of polycrystalline Fe and Ni. Electrochemical methods were used to elucidate the overpotential value, the charge transfer resistance and the double layer capacity. Structural properties of the electrode surface were determined with SEM, XRD and XPS analyses. Thus, a correlation between electrochemical and structural parameters was found. In this context, we report on a cyclic voltammetric activation procedure which causes a significant increase of the surface area of Fe-based electrodes leading to a boost in effective activity of the activated electrodes. It was found that the intrinsic activity of activated Fe-based electrodes is very high due to the formation of a nanocrystalline surface layer. In contrast, the activation procedure influences only the intrinsic activity of the Ni electrodes without the formation of a porous surface layer.

  15. 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.

  16. Graphene electrodes for stimulation of neuronal cells

    Science.gov (United States)

    Koerbitzer, Berit; Krauss, Peter; Nick, Christoph; Yadav, Sandeep; Schneider, Joerg J.; Thielemann, Christiane

    2016-06-01

    Graphene has the ability to improve the electrical interface between neuronal cells and electrodes used for recording and stimulation purposes. It provides a biocompatible coating for common electrode materials such as gold and improves the electrode properties. Graphene electrodes are also prepared on SiO2 substrate to benefit from its optical properties like transparency. We perform electrochemical and Raman characterization of gold electrodes with graphene coating and compare them with graphene on SiO2 substrate. It was found that the substrate plays an important role in the performance of graphene and show that graphene on SiO2 substrate is a very promising material combination for stimulation electrodes.

  17. 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 foilelectrodes. 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.

  18. Compressed multiwall carbon nanotube composite electrodes provide enhanced electroanalytical performance for determination of serotonin

    International Nuclear Information System (INIS)

    Serotonin (5-HT) is an important neurochemical that is present in high concentrations within the intestinal tract. Carbon fibre and boron-doped diamond based electrodes have been widely used to date for monitoring 5-HT, however these electrodes are prone to fouling and are difficult to fabricate in certain sizes and geometries. Carbon nanotubes have shown potential as a suitable material for electroanalytical monitoring of 5-HT but can be difficult to manipulate into a suitable form. The fabrication of composite electrodes is an approach that can shape conductive materials into practical electrode geometries suitable for biological environments. This work investigated how compression of multiwall carbon nanotubes (MWCNTs) epoxy composite electrodes can influence their electroanalytical performance. Highly compressed composite electrodes displayed significant improvements in their electrochemical properties along with decreased internal and charge transfer resistance, reproducible behaviour and improved batch to batch variability when compared to non-compressed composite electrodes. Compression of MWCNT epoxy composite electrodes resulted in an increased current response for potassium ferricyanide, ruthenium hexaammine and dopamine, by preferentially removing the epoxy during compression and increasing the electrochemical active surface of the final electrode. For the detection of serotonin, compressed electrodes have a lower limit of detection and improved sensitivity compared to non-compressed electrodes. Fouling studies were carried out in 10 μM serotonin where the MWCNT compressed electrodes were shown to be less prone to fouling than non-compressed electrodes. This work indicates that the compression of MWCNT carbon-epoxy can result in a highly conductive material that can be moulded to various geometries, thus providing scope for electroanalytical measurements and the production of a wide range of analytical devices for a variety of systems

  19. Development of high temperature reference electrodes for in-pile application: Part I. Feasibility study of the external pressure balanced Ag/AgCl reference electrode (EPBRE) and the cathodically charged Palladium hydrogen electrode

    Energy Technology Data Exchange (ETDEWEB)

    Bosch, R.W.; Van Nieuwenhove, R

    1998-10-01

    The main problems connected with corrosion potential measurements at elevated temperatures and pressures are related to the stability and lifetime of the reference electrode and the correct estimation of the potential related to the Standard Hydrogen Scale (SHE). Under Pressurised Water Reactor (PWR) conditions of 300 degrees Celsius and 150 bar, the choice of materials is also a limiting factor due to the influence of radiation. Investigations on two reference electrodes that can be used under PWR conditions are reported: the cathodically charged palladium hydrogen electrode, and the external pressure balanced silver/silver chloride electrode. Preliminary investigations with the Pd-electrode were focused on the calculation of the required charging time and the influence of dissolved oxygen. High temperature applications are discussed on the basis of results reported in the literature. Investigations with the silver/silver chloride reference electrode mainly dealt with the salt bridge which is necessary to connect the reference electrode with the testing solution. It is shown that the thermal junction potential is independent of the length of the salt bridge. In addition, the high temperature contributes to an increase of the conductivity of the solution, which is beneficial for the salt bridge connection.

  20. Development of high temperature reference electrodes for in-pile application: Part I. Feasibility study of the external pressure balanced Ag/AgCl reference electrode (EPBRE) and the cathodically charged Palladium hydrogen electrode

    International Nuclear Information System (INIS)

    The main problems connected with corrosion potential measurements at elevated temperatures and pressures are related to the stability and lifetime of the reference electrode and the correct estimation of the potential related to the Standard Hydrogen Scale (SHE). Under Pressurised Water Reactor (PWR) conditions of 300 degrees Celsius and 150 bar, the choice of materials is also a limiting factor due to the influence of radiation. Investigations on two reference electrodes that can be used under PWR conditions are reported: the cathodically charged palladium hydrogen electrode, and the external pressure balanced silver/silver chloride electrode. Preliminary investigations with the Pd-electrode were focused on the calculation of the required charging time and the influence of dissolved oxygen. High temperature applications are discussed on the basis of results reported in the literature. Investigations with the silver/silver chloride reference electrode mainly dealt with the salt bridge which is necessary to connect the reference electrode with the testing solution. It is shown that the thermal junction potential is independent of the length of the salt bridge. In addition, the high temperature contributes to an increase of the conductivity of the solution, which is beneficial for the salt bridge connection

  1. Micromachined dense palladium electrodes for thin-film solid acid fuel cells

    NARCIS (Netherlands)

    Unnikrishnan, Sandeep

    2009-01-01

    This thesis paves the way towards the microfabrication of a solid acid electrolyte based fuel cell (µSAFC), which has a membrane electrode assembly (MEA) consisting of a thin-film of water soluble electrolyte encapsulated between two dense palladium electrode membranes. This project work investigate

  2. An improved configuration for the reduction of EMG in electrode cuff recordings: a theoretical approach.

    Science.gov (United States)

    Rahal, M; Winter, J; Taylor, J; Donaldson, N

    2000-09-01

    A theoretical investigation of different electroneurogram recording techniques using electrode cuffs is presented. A new screened tripole arrangement is proposed with a higher inherent signal to interference ratio than the true tripole, which also allows the nulling of the residual electromyogram signal. The reduction in interference is small because the electrode impedance is large compared to the source resistance. PMID:11008430

  3. 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

  4. Electrochemical reduction of Tm on Mg electrodes and co-reduction of Mg, Li and Tm on W electrodes

    International Nuclear Information System (INIS)

    The reduction process of Tm(III) ions was investigated in LiCl–KCl–MgCl2 melt on a W electrode and in LiCl–KCl melt on a Mg electrode at 753 K, respectively. On the W electrode, in LiCl–KCl–MgCl2 melt the reduction of Tm(III) ions was a two-step process: Tm(III) + e−1 → Tm(II) and yTm(II) + 2ye−1 + xMg → MgxTmy. The reduction process of Tm(III)/Tm(II) was not observed on the Mg electrode, and only two signals, related to Mg–Tm intermetallic compounds were observed, in the cyclic voltammogram and chronopotentiogram. Galvanostatic electrolysis was employed to prepare Mg–Li–Tm alloys on both W and Mg electrodes. The deposits were characterized by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). Mg24Tm5 and Mg2Tm phases were detected in the deposits. The effect of Tm addition on Mg–Li alloy was investigated via potentiodynamic polarization and OM at room temperature. The grain size of Mg–Li alloy becomes much smaller after addition of Tm element. The corrosion potentials of Mg–Li–Tm alloys shift toward a more positive direction than that of Mg–Li alloy

  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. Unraveling the Degradation Process of LiNi0.8Co0.15Al0.05O2 Electrodes in Commercial Lithium Ion Batteries by Electronic Structure Investigations.

    Science.gov (United States)

    Kleiner, Karin; Melke, Julia; Merz, Michael; Jakes, Peter; Nagel, Peter; Schuppler, Stefan; Liebau, Verena; Ehrenberg, Helmut

    2015-09-01

    The degradation of LiNi0.8Co0.15Al0.05O2 (LNCAO) is reflected by the electrochemical performance in the fatigued state and correlated with the redox behavior of these cathodes. The detailed electrochemical performance of these samples is investigated by galvanostatic and voltammetric cycling as well as with the galvanostatic intermittent titration technique (GITT). Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy was used to investigate the oxidation state of all three materials at the Ni L2,3, O K, and Co L2,3 edges at five different states of charge. Surface and more bulklike properties are distinguished by total electron yield (TEY) and fluorescence yield (FY) measurements. The electrochemical investigations revealed that the changes in the cell performance of the differently aged materials can be explained by considering the reaction kinetics of the intercalation/deintercalation process. The failure of the redox process of oxygen and nickel at low voltages leads to a significant decrease of the reaction rates in the fatigued cathodes. The accompanied cyclic voltammogram (CV) peaks appear as two peaks because of the local minimum of the reaction rate, although it is one peak in the CV of the calendarically aged LNCAO. The absence of the oxidation/reduction process at low voltages can be traced back to changes in the surface morphology (formation of a NiO-like structure). Further consequences of these material changes are overpotentials, which lead to capacity losses of up to 30% (cycled with a C/3 rate). PMID:26281920

  7. Lithium electronic environments in rechargeable battery electrodes

    Science.gov (United States)

    Hightower, Adrian

    This work investigates the electronic environments of lithium in the electrodes of rechargeable batteries. The use of electron energy-loss spectroscopy (EELS) in conjunction with transmission electron microscopy (TEM) is a novel approach, which when coupled with conventional electrochemical experiments, yield a thorough picture of the electrode interior. Relatively few EELS experiments have been preformed on lithium compounds owing to their reactivity. Experimental techniques were established to minimize sample contamination and control electron beam damage to studied compounds. Lithium hydroxide was found to be the most common product of beam damaged lithium alloys. Under an intense electron beam, halogen atoms desorbed by radiolysis in lithium halides. EELS spectra from a number of standard lithium compounds were obtained in order to identify the variety of spectra encountered in lithium rechargeable battery electrodes. Lithium alloys all displayed characteristically broad Li K-edge spectra, consistent with transitions to continuum states. Transitions to bound states were observed in the Li K and oxygen K-edge spectra of lithium oxides. Lithium halides were distinguished by their systematic chemical shift proportional to the anion electronegativity. Good agreement was found with measured lithium halide spectra and electron structure calculations using a self-consistant multiscattering code. The specific electrode environments of LiC6, LiCoO2, and Li-SnO were investigated. Contrary to published XPS predictions, lithium in intercalated graphite was determined to be in more metallic than ionic. We present the first experimental evidence of charge compensation by oxygen ions in deintercalated LiCoO2. Mossbauer studies on cycled Li-SnO reveal severely defective structures on an atomic scale. Metal hydride systems are presented in the appendices of this thesis. The mechanical alloying of immiscible Fe and Mg powders resulted in single-phase bcc alloys of less than 20

  8. Anodized Steel Electrodes for Supercapacitors.

    Science.gov (United States)

    Sagu, Jagdeep S; Wijayantha, K G Upul; Bohm, Mallika; Bohm, Siva; Kumar Rout, Tapan

    2016-03-01

    Steel was anodized in 10 M NaOH to enhance its surface texture and internal surface area for application as an electrode in supercapacitors. A mechanism was proposed for the anodization process. Field-emission gun scanning electron microscopy (FEGSEM) studies of anodized steel revealed that it contains a highly porous sponge like structure ideal for supercapacitor electrodes. X-ray photoelectron spectroscopy (XPS) measurements showed that the surface of the anodized steel was Fe2O3, whereas X-ray diffraction (XRD) measurements indicated that the bulk remained as metallic Fe. The supercapacitor performance of the anodized steel was tested in 1 M NaOH and a capacitance of 18 mF cm(-2) was obtained. Cyclic voltammetry measurements showed that there was a large psueudocapacitive contribution which was due to oxidation of Fe to Fe(OH)2 and then further oxidation to FeOOH, and the respective reduction of these species back to metallic Fe. These redox processes were found to be remarkably reversible as the electrode showed no loss in capacitance after 10000 cycles. The results demonstrate that anodization of steel is a suitable method to produce high-surface-area electrodes for supercapacitors with excellent cycling lifetime. PMID:26891093

  9. 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

  10. Potential electrode/electrolyte interactions in solid oxide fuel cells

    International Nuclear Information System (INIS)

    Yttria-stabilized zirconia and strontium-doped lanthanum manganite are the prime candidates for the electrolyte and the air electrode material, respectively, for the solid oxide fuel cell. In this study, the potential high temperature interactions, including intrinsic reactivity and interdiffusion, between these two fuel cell components have been investigated

  11. The field enhancement factor of sand-blasted electrodes

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Vibholm (fratrådt), Svend

    1992-01-01

    A sample of six sand-blasted electrodes has been subjected to both mechanical and electrical investigations. When the surfaces of a series of conductors are mechanically treated, the resultant microscopic surface geometries will be similar, but not identical. As a consequence of this spread in the...

  12. Gelatin coated electrodes allow prolonged bioelectronic measurements

    Science.gov (United States)

    1966-01-01

    Silver electrodes treated with an anodizing electrolyte containing gelatin are used for long term monitoring of bioelectronic potentials in humans. The electrodes do not interact with perspiration, cause skin irritation, or promote the growth of bacteria.

  13. Current collector geometry and mixing in liquid metal electrodes

    Science.gov (United States)

    Ashour, Rakan; Kelley, Douglas

    2015-11-01

    Liquid metal batteries are emerging as an efficient and cost effective technology for large-scale energy storage on electrical grids. In these batteries, critical performance related factors such as the limiting current density and life cycle are strongly influenced by fluid mixing and transport of electrochemical species to and from the electrode-electrolyte interface. In this work, ultrasound velocimetry is used to investigate the role of negative current collector location on the induced velocity, flow pattern, and mixing time in liquid metal electrodes. Ultrasound velocity measurements are obtained at a range of operating current densities. Furthermore, a comparison between velocity profiles produced by current collectors with different sizes is also presented.

  14. 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.

  15. 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

    The electroenzymatic reactions of Trametes hirsuta laccase in the pure organic solvent dimethyl sulfoxide (DMSO) have been investigated within the framework for potential use as a catalytic reaction scheme for oxygen reduction. The bioelectrochemical characteristics of laccase were investigated in...... 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...

  16. Electrochemical behaviour of benzene on platinum electrodes

    OpenAIRE

    Montilla Jiménez, Francisco; Huerta Arráez, Francisco; Morallón Núñez, Emilia; Vázquez Picó, José Luis

    1999-01-01

    The adsorption and oxidation of benzene in acidic media on platinum electrodes (polycrystalline and single-crystal electrodes) have been studied by cyclic voltammetry and in-situ Fourier transform infrared spectroscopy. The oxidation characteristics of benzene depend on the surface structure of the platinum electrode used. In all platinum electrodes studied, the main reduction product of benzene is cyclohexane, and the oxidation products detected by infrared spectroscopy have been CO2 and ben...

  17. 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...... that both the ionic and electronic pathways in the electrode were negatively affected by the cycling. Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) tomography of both electrodes shows that cycling causes agglomerations of Carbon black (CB). In addition to this, Low-voltage FIB/SEM revealed...... non-conductive CB in the aged electrode....

  18. Voltammetry at porous electrodes: A theoretical study

    OpenAIRE

    Barnes, Edward O; Chena, Xiaojun; 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.

  19. Inexpensive and Disposable pH Electrodes

    Science.gov (United States)

    Goldcamp, Michael J.; Conklin, Alfred; Nelson, Kimberly; Marchetti, Jessica; Brashear, Ryan; Epure, Emily

    2010-01-01

    Inexpensive electrodes for the measurement of pH have been constructed using the ionophore tribenzylamine for sensing H[superscript +] concentrations. Both traditional liquid-membrane electrodes and coated-wire electrodes have been constructed and studied, and both exhibit linear, nearly Nernstian responses to changes in pH. Measurements of pH…

  20. Enhanced stress durability of nano resonators with scandium doped electrodes

    International Nuclear Information System (INIS)

    To explore mechanical stress durability of thin aluminum-scandium (AlSc) films, 0.86 GHz nano resonators with AlSc electrodes have been manufactured. Four different samples have been prepared altering the Sc content in the alloy between 0.0% and 2.5%. A final lift-off step accomplished manufacture procedure of the devices. The resonators have been operated with heavy load to determine power durability. The resonators with AlSc electrodes show increased power durability compared to conventional Al metallized devices. Texture and grain structure of all films have been investigated by means of electron backscatter diffraction (EBSD) and atomic force microscopy (AFM). Material fatigue of electrodes has been visualized by scanning electron microscopy (SEM). The refined grain structure of these alloys can explain the enhanced mechanical stress durability of AlSc electrodes. - Research Highlights: →Enhanced power durability of SAW devices with Sc doped electrodes. →Refined grain structure of Sc doped Al films. →Sudden device breakdown of highly Sc doped devices.