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  • 1.
    Golczak, Sebastian
    et al.
    Adam Mickiewicz University Poznan.
    Kanciurzewska, Anna
    Adam Mickiewicz University Poznan.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Langer, Krzysztof
    Adam Mickiewicz University Poznan.
    Langer , Jerzy J
    Adam Mickiewicz University Poznan.
    Comparative XPS surface study of polyaniline thin films2008In: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 179, no 39, p. 2234-2239Article in journal (Refereed)
    Abstract [en]

    Polyaniline (PANI) films of different thickness have been deposited electrochemically at two different potentials of 0.8 and 1.2 V. Characterization of the surface composition of the material: oxidation states and structural changes have been performed using X-ray photoelectron spectroscopy (XPS). The main findings of this work show that the ratio of the imine to amine nitrogens for thicker films of PANI is close to unity, indicating that the surface layer of PANI is in the emeraldine form (base). On the other hand, the surface of thinner films of PANI contains similar to 14-20% imine nitrogen and similar to 60-70% amine nitrogen. This corresponds to an oxidation state close to that of protoemeraldine. Furthermore, XPS confirms a considerable amount of p-benzoquinone (BQ) as side product formed in all thin samples. The surface morphology examined by electron microscopy measurements shows that thin films have a uniform structure, whereas microporous structure with microchannels and microcaves inside, formed as a non-periodic network of microrods is characteristic for thicker PANI films.

  • 2.
    HERMANSSON, KERSTI
    et al.
    Uppsala universitet, Kemiska institutionen.
    OJAMAE, LARS
    ON THE ROLE OF ELECTRIC-FIELDS FOR PROTON-TRANSFER IN WATER1995In: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 77, p. 34-42Article in journal (Refereed)
    Abstract [en]

    The influence of uniform and non-uniform electric fields on one-dimensional proton transfer curves for (H2O)(2), H5O2+ and H3O2- has been examined using quantum-mechanical ab initio calculations. Both liquid-state and solid-state environments are discussed. For the charged complexes the transfer barrier is removed or greatly reduced by a field as small as 0.005 a.u. (2.5 X 10(7) V/cm). Local field fluctuations of this size are easily produced in condensed aqueous systems at room temperature. For the asymmetric single-well potential of an (H2O)(2) complex, a field ten times larger is needed to move the minimum from one side to the other across the O ... O bond. Such local fields can be achieved in ionic aqueous systems. The energy barrier for proton transfer in ice Ih has been computed using a periodic Hartree-Fock approach; the barrier for a fully concerted proton transfer is similar to 60 kJ/mol.

  • 3.
    Klarbring, Johan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Vekilova, Olga Yu.
    KTH Royal Institute Technology, Sweden; Uppsala University, Sweden.
    Nilsson, Johan O.
    KTH Royal Institute Technology, Sweden.
    Skorodumova, Natalia V.
    KTH Royal Institute Technology, Sweden; Uppsala University, Sweden.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Ionic conductivity in Sm-doped ceria from first-principles non-equilibrium molecular dynamics2016In: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 296, p. 47-53Article in journal (Refereed)
    Abstract [en]

    Sm-doped ceria is a prospective electrolyte material for intermediate-temperature solid-oxide fuel cells (IT-SOFC). Equilibrium ab initio molecular dynamics (AIMD) studies of oxygen ion diffusion in this material are currently impractical due to the rareness of diffusive events on the accessible timescale. To overcome this issue we have performed ab initio non-equilibrium molecular dynamics calculations of Sm-doped ceria using the color diffusion algorithm. Applying an external force field we have been able to increase the frequency of diffusive events over the simulation time, while keeping the physical mechanism of diffusion intact. We have investigated the temperature dependence of the maximum strength of the applied external field that could be used while maintaining the response of the system in a linear regime. This allows one to obtain the diffusivity at zero field. The bulk ionic conductivity has been calculated and found to match the experimental data well. We have also compared the description of the diffusion process by our method to previous findings and show that the migration mechanism and site preference of oxygen vacancies with respect to the Sm dopants is well reproduced. (C) 2016 Elsevier B.V. All rights reserved.

  • 4.
    Larsson, AL
    et al.
    The Ångström Laboratory, Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Sernelius, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Niklasson, Gunilla
    The Ångström Laboratory, Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Optical absorption of Li-intercalated polycrystalline tungsten oxide films: comparison to large polaron theory2003In: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 165, no 1-4, p. 35-41Article in journal (Refereed)
    Abstract [en]

    Thin films of polycrystalline tungsten trioxide were manufactured using DC magnetron sputtering. Films of different thickness were deposited onto glass substrates coated with indium tin oxide (ITO). The crystallinity was confirmed by X-ray diffraction, and the grain size was found to be 30 nm. Li ions and electrons were intercalated into the sample using a three-electrode setup. The samples were submitted to optical characterization by spectrophotometry, in the visible and infrared ranges. The optical spectra were recorded at different intercalation states, and the absorption of the films was obtained. At low intercalation levels, a pronounced absorption peak was observed to be centered at a wavelength of 1.8 mum. Upon intercalation, the inserted electrons enter the conduction band, but due to a strong electron-phonon interaction, they are believed to form localized polarons. Calculations of optical absorption by large polaron theory were carried out and the position of the observed peak was in good agreement with the theory. A crossover from dielectric (low reflectance and clear phonon absorption bands) to metallic (high infrared reflectance) occurred at a Li intercalation level of around 0.05-0.15 Li/W. This may be due to overlap of the polaron states. (C) 2003 Elsevier B.V All rights reserved.

  • 5.
    Tehrani, Payman
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Kanciurzewska, Anna
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Crispin, Xavier
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Robinson, Nathaniel D.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    The effect of pH on the elechtrochemical over-oxidation of PEDOT:PSS films2007In: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 177, no 39-40, p. 3521-3527Article in journal (Refereed)
    Abstract [en]

    Chemical degradation of conjugated polymers is one cause of material failures in polymer-based (opto)electronic devices, but can also be used as a technique for subtractive patterning of polymer films. When a large anodic potential is applied to the conducting polymer blend poly(3,4-ethylenedioxythiophene)-poly(4styrenesulfonate), PEDOT:PSS, an over-oxidation reaction occurs, altering its electrical conductivity. Here, we have studied the effect of pH on the electrochemical over-oxidation process of PEDOT in PEDOT:PSS. High pH is associated with a decrease of over-oxidation potential and an increase of resistivity in the resulting film. Vibrational spectroscopy and photoelectron spectroscopy measurements on over-oxidized PEDOT:PSS films indicate that the decrease in conductivity results from cleavage of the conjugation pathway accompanied by the formation of sulfone, carbonyl and carboxylic groups in the polymer chain.

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