Advanced Functional Materials

Cover image for Advanced Functional Materials

September, 2004

Volume 14, Issue 9

Pages 827–930

    1. Alignment of a Perylene-Based Ionic Self-Assembly Complex in Thermotropic and Lyotropic Liquid-Crystalline Phases (pages 835–841)

      Y. Zakrevskyy, C. F. J. Faul, Y. Guan and J. Stumpe

      Version of Record online: 29 SEP 2004 | DOI: 10.1002/adfm.200305194

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      Thermotropic and lyotropic liquid-crystalline (LC) phases of the ionic self-assembled complex of perylene-based tectons and bis(2-ethylhexyl)sulfosuccinate have been prepared. Alignment by controlled domain formation at the phase-transition front (PTF) of the lyotropic LC–isotropic phase transition yielded a dichroic ratio of 18 and packing of columns of perylenediimide tectons perpendicular to the PTF (see Figure).

    2. Composites of Polyacrylonitrile and Multiwalled Carbon Nanotubes Prepared by Gelation/Crystallization from Solution (pages 842–850)

      A. Koganemaru, Y. Bin, Y. Agari and M. Matsuo

      Version of Record online: 29 SEP 2004 | DOI: 10.1002/adfm.200305034

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      Composite films of polyacrylonitrile (PAN) and multiwalled carbon nanotubes (MWNTs) have been prepared via gelation/crystallization from solution and their electrical and mechanical properties are studied. Stabilization and carbonization have additionally been carried out (using the drawn PAN–MWNT composite as a new precursor) in order to prepare carbon films with a cross-sectional area ∼3000 times larger than that of commercial carbon fibers (see Figure).

    3. Synthesis of Nanowalled Polymer Microtubes Using Glass Fiber Templates (pages 851–855)

      D. Tuncel, J. R. Matthews and H. L. Anderson

      Version of Record online: 29 SEP 2004 | DOI: 10.1002/adfm.200305201

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      Covalently crosslinked flexible polymer microtubes with wall thicknesses of 1–3 nm and diameters of 2–10 μm (see Figure) have been fabricated using glass wool as a template. Fluorescent polyamines were adsorbed onto the glass wool and crosslinked by reductive amination with glutaraldehyde and NaH3BCN, then the templates were dissolved using HF.

    4. Photoluminescence and Electron Paramagnetic Resonance of ZnO Tetrapod Structures (pages 856–864)

      A. B. Djurišić, W. C. H. Choy, V. A. L. Roy, Y. H. Leung, C. Y. Kwong, K. W. Cheah, T. K. Gundu Rao, W. K. Chan, H. Fei Lui and C. Surya

      Version of Record online: 29 SEP 2004 | DOI: 10.1002/adfm.200305082

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      ZnO nanostructures have been prepared via the evaporation of zinc under different atmospheres (see Figure). No relationship has been shown to exist between the g = 1.96 electron paramagnetic resonance (EPR) spectroscopy signal and green photoluminescence; this contradicts the commonly assumed transition which occurs between a singly charged oxygen vacancy and a photoexcited hole.

    5. Hole Transport in Poly(phenylene vinylene)/Methanofullerene Bulk-Heterojunction Solar Cells (pages 865–870)

      C. Melzer, E. J. Koop, V. D. Mihailetchi and P. W. M. Blom

      Version of Record online: 29 SEP 2004 | DOI: 10.1002/adfm.200305156

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      The charge-carrier transport in bulk-heterojunction solar cells based on a poly(phenylene vinylene) (MDMO) and a methanofullerene (PCBM) is shown to be much more balanced than previously assumed. (The Figure shows mobility versus the square root of the electric field.) Space-charge build-up is therefore not limiting the photoresponse of the solar cell and the typically observed high fill factors of 60 % are explained.

    6. Superparamagnetic Hybrid Nanocylinders (pages 871–882)

      M. Zhang, C. Estournès, W. Bietsch and A. H. E. Müller

      Version of Record online: 29 SEP 2004 | DOI: 10.1002/adfm.200400064

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      Unimolecular cylindrical micelles, amphiphilic cylindrical polymer brushes with poly(acrylic acid) cores and poly(n-butyl acrylate) shells, have been successfully used as single-molecular templates for the synthesis of magnetic nanoparticles (see Figure). The synthesized hybrid nanocylinders exhibit interesting superparamagnetic behavior.

    7. Fractal and Non-Fractal Structure–Property Relationships of Polymer-Stabilized Liquid Crystals (pages 883–890)

      I. Dierking

      Version of Record online: 29 SEP 2004 | DOI: 10.1002/adfm.200305031

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      By characterizing polymer networks through their fractal dimensions, structure–property relationships are established to quantitatively predict the electro-optic response of polymer-stabilized liquid crystals (an example is shown in the Figure) as fundamental preparation conditions, leading to variations in network morphology, are changed. Some non-fractal scaling laws are also discussed.

    8. Ambipolar Charge Transport in Air-Stable Polymer Blend Thin-Film Transistors (pages 891–898)

      A. Babel, J. D. Wind and S. A. Jenekhe

      Version of Record online: 29 SEP 2004 | DOI: 10.1002/adfm.200305180

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      Ambipolar thin-film transistors based on air-stable blends of n-type poly(benzobisimidazobenzophenanthroline) and p-type copper phthalocyanine have been demonstrated (see Figure). The ambipolar charge transport and carrier mobilities are intricately related to the phase-separated domain sizes and crystalline morphology of the blends.

    9. Dielectric Properties of Pure (BaSr)TiO3 and Composites with Different Grain Sizes Ranging from the Nanometer to the Micrometer (pages 899–904)

      V. Hornebecq, C. Huber, M. Maglione, M. Antonietti and C. Elissalde

      Version of Record online: 29 SEP 2004 | DOI: 10.1002/adfm.200305052

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      The influence of grain size (see Figure) on the ferroelectric–paraelectric transition temperature (TC) is studied for Ba0.6Sr0.4TiO3 (BST) powders. A decrease of TC with grain size is observed for pressed powders. BST nanocomposites (core–shell materials and gels) are synthesized in order to study this effect on dense ceramics.

    10. Engineered Second Harmonic Generation in Photonic-Crystal Slabs Consisting of Centrosymmetric Materials (pages 905–912)

      X. Luo and T. Ishihara

      Version of Record online: 29 SEP 2004 | DOI: 10.1002/adfm.200305064

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      Centrosymmetric materials produce nonlinearity in photonic-crystal slabs (PCSs) (see Figure) as reported here. Based on the quadrupole effect, it is shown that second harmonic generation (SHG) occurs when the pump mode with an asymmetric electromagnetic field distribution couples into the eigenmode of the PCSs. The studies also show that phase matching can be achieved based on quasi eigenmodes.

    11. Controlled Growth and Properties of One-Dimensional ZnO Nanostructures with Ce as Activator/Dopant (pages 913–919)

      B. C. Cheng, Y. H. Xiao, G. S. Wu and L. D. Zhang

      Version of Record online: 29 SEP 2004 | DOI: 10.1002/adfm.200305097

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      Ce doping can be used to control the morphology of 1D ZnO nanostructures as demonstrated here. Variation of synthesis temperature is also shown to have an effect: bicrystalline nanobelts are obtained at a synthesis temperature lower than 900 °C, but nanowires with commensurately modulated superstructure (see Figure) grow above this temperature. The incorporation of the donor Ce leads to a change in the band-gap structure of ZnO and modulates the photoluminescence.

    12. A Ferroelectric Ferromagnetic Composite Material with Significant Permeability and Permittivity (pages 920–926)

      X. Qi, J. Zhou, Z. Yue, Z. Gui, L. Li and S. Buddhudu

      Version of Record online: 29 SEP 2004 | DOI: 10.1002/adfm.200305086

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      A novel composite with coexistent ferroelectric and ferromagnetic phases has been prepared using a standard ceramic method. Both high dielectric constant and high magnetic permeability (see Figure) are shown in the xBaTiO3-(1 – x)Ni0.2Cu0.2Zn0.6Fe1.96O4 material, which is significant for the integration of passive components.