Advanced Functional Materials

Cover image for Vol. 16 Issue 5

March, 2006

Volume 16, Issue 5

Pages 591–722

    1. Cover Picture: Thermotropic Liquid Crystals as Substrates for Imaging the Reorganization of Matrigel by Human Embryonic Stem Cells (Adv. Funct. Mater. 5/2006)

      N. A. Lockwood, J. C. Mohr, L. Ji, C. J. Murphy, S. P. Palecek, J. J. de Pablo and N. L. Abbott

      Version of Record online: 7 MAR 2006 | DOI: 10.1002/adfm.200690018

      A liquid crystal coated with a thin film of extracellular matrix (Matrigel) is used as a substrate for the culture of human embryonic stem cells. The orientation of the liquid crystal is coupled to the Matrigel film, which permits visualization of the reorganization of Matrigel by the cells (see Figure and cover). The results suggest new approaches to the culture of cells and measurement of cell–extracellular-matrix interactions.

    2. Towards General Guidelines for Aligned, Nanoscale Assemblies of Hairy-Rod Polyfluorene (pages 599–609)

      M. Knaapila, R. Stepanyan, B. P. Lyons, M. Torkkeli and A. P. Monkman

      Version of Record online: 31 JAN 2006 | DOI: 10.1002/adfm.200500419

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      The hierarchical levels of solid-state structure in a prototypical hairy-rod polyfluorene are reviewed. Self-organization, phase behavior (see Figure), alignment of polymers and crystallites, surface morphology, the effects of these on optical constants, and the influence of molecular weight are detailed.

    3. White-Light-Emitting Diodes Based on Iridium Complexes via Efficient Energy Transfer from a Conjugated Polymer (pages 611–617)

      T.-H. Kim, H. K. Lee, O O. Park, B. D. Chin, S.-H. Lee and J. K. Kim

      Version of Record online: 24 JAN 2006 | DOI: 10.1002/adfm.200500621

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      Efficient polymer-based electrophosphorescent devices for stable white-light emission (see Figure) take advantage of efficient energy transfer from a conjugated polymer to iridium complexes. Poly(N-vinylcarbazole) increases energy transfer from the conjugated polymer to the phosphorescent dyes by improving the chemical compatibility; hence, the microphase-separated morphology of the blend allows blue-light emission from the polymer, and green and red from the iridium complexes.

    4. Thermotropic Liquid Crystals as Substrates for Imaging the Reorganization of Matrigel by Human Embryonic Stem Cells (pages 618–624)

      N. A. Lockwood, J. C. Mohr, L. Ji, C. J. Murphy, S. P. Palecek, J. J. de Pablo and N. L. Abbott

      Version of Record online: 16 FEB 2006 | DOI: 10.1002/adfm.200500768

      Thumbnail image of graphical abstract

      A liquid crystal coated with a thin film of extracellular matrix (Matrigel) is used as a substrate for the culture of human embryonic stem cells. The orientation of the liquid crystal is coupled to the Matrigel film, which permits visualization of the reorganization of Matrigel by the cells (see Figure and cover). The results suggest new approaches to the culture of cells and measurement of cell–extracellular-matrix interactions.

    5. Ultrathin Luminescent Films of Rigid Dinuclear Ruthenium(II) Trisbipyridine Complexes (pages 625–632)

      F. W. Vergeer, X. Chen, F. Lafolet, L. De Cola, H. Fuchs and L. F. Chi

      Version of Record online: 9 FEB 2006 | DOI: 10.1002/adfm.200500446

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      Monolayer films of two luminescent bimetallic ruthenium complexes, bearing 4,4′-dialkyl-2,2′-bipyridine ligands (see Figure) on one of the metal centers, have been characterized at the air/water interface and subsequently transferred to solid substrates using the Langmuir–Blodgett (LB) technique. The compact LB films display a homogeneous red emission (see confocal laser scanning microscope image; 40 μm wide).

    6. Continuous, Atmospheric Process to Create Organic Clusters and Nanostructured, Functional Films (pages 633–639)

      R. Jagannathan and R. V. Mehta

      Version of Record online: 31 JAN 2006 | DOI: 10.1002/adfm.200500601

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      An atmospheric process is developed to create stable, organic molecular clusters and from these build nanostructured, functional films (see Figure). When used in organic light-emitting diodes, the cluster-derived films show physical and device characteristics that match those of vacuum-built systems.

    7. Surface-Initiated Atom Transfer Radical Polymerization of Oligo(ethylene glycol) Methyl Methacrylate from a Mixed Self-Assembled Monolayer on Gold (pages 640–648)

      H. Ma, M. Wells, T. P. Beebe Jr. and A. Chilkoti

      Version of Record online: 16 FEB 2006 | DOI: 10.1002/adfm.200500426

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      The in-situ synthesis of protein-resistant polymer films by surface-initiated ATRP of oligo(ethylene glycol) methyl methacrylate from mixed SAMs of initiator-functionalized alkanethiol/ diluent thiol is described (see Figure). Above a threshold solution molar ratio of the initiator thiol to diluent thiol of 0.2, and a dry-film thickness of ∼4 nm, fibronectin adsorption on the polymer coatings was below 1 ng cm–2.

    8. Understanding the Beneficial Role of Grain Boundaries in Polycrystalline Solar Cells from Single-Grain-Boundary Scanning Probe Microscopy (pages 649–660)

      I. Visoly-Fisher, S. R. Cohen, K. Gartsman, A. Ruzin and D. Cahen

      Version of Record online: 31 JAN 2006 | DOI: 10.1002/adfm.200500396

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      Polycrystallinity can be good for solar cells. Defects such as grain boundaries, which are thought to decrease performance of polycrystalline solar cells, can participate in, and help photovoltaic conversion, as we show for CdTe grain boundaries in polycrystalline thin film CdTe/CdS cells. The figure shows simultaneously collected topography and current maps of a CdTe surface.

    9. Manipulation of the Morphology of CdSe Nanostructures: The Effect of Si (pages 661–666)

      Z. Y. Wang, Q. F. Lu, X. S. Fang, X. K. Tian and L. D. Zhang

      Version of Record online: 2 FEB 2006 | DOI: 10.1002/adfm.200500646

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      Nanowires, nanorods, nanoparticles, and tetrapod crystals are grown on silicon substrates by simple, Si-assisted chemical vapor deposition. Each tetrapod is formed in two steps: first, twins form on the CdSe solid-state nuclei, then, the arms grow via twinning to form a tetrapod (see Figure) during the cooling process (from 1150 to 850 °C) in a furnace.

    10. Influence of Solvent Mixing on the Morphology and Performance of Solar Cells Based on Polyfluorene Copolymer/Fullerene Blends (pages 667–674)

      F. Zhang, K. G. Jespersen, C. Björström, M. Svensson, M. R. Andersson, V. Sundström, K. Magnusson, E. Moons, A. Yartsev and O. Inganäs

      Version of Record online: 9 FEB 2006 | DOI: 10.1002/adfm.200500339

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      The influence of the solvent on the performance of polymer solar cells based on blends of the polyfluorene copolymer poly(2,7-(9,9-dioctyl- fluorene)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)) (APFO-3), and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is investigated. The surfaces of the active layers are imaged (see Figure) and the excited-state dynamics are investigated using time-resolved spectroscopy.

    11. Design of the Magnetic Properties of Fe-Rich, Glass-Coated Microwires for Technical Applications (pages 675–680)

      A. Zhukov

      Version of Record online: 31 JAN 2006 | DOI: 10.1002/adfm.200500248

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      The magnetic anisotropy of Fe-rich, thin, amorphous wires (see Figure) is tailored by stress annealing, allowing the induction of transverse magnetic anisotropy and a considerable stress-sensitive giant magnetoimpedance effect in microwires with a positive magnetostriction constant. Such samples are suitable for magnetoelastic sensors and stress-sensitive, tunable composite materials.

    12. 2,5-Functionalized Spiro-Bisiloles as Highly Efficient Yellow-Light Emitters in Electroluminescent Devices (pages 681–686)

      J. H. Lee, Y.-Y. Yuan, Y. J. Kang, W.-L. Jia, Z.-H. Lu and S. N. Wang

      Version of Record online: 9 FEB 2006 | DOI: 10.1002/adfm.200500386

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      A highly efficient yellow-light-emitting electroluminescent device with a double-layer structure that uses a new 2,2′-dipyridylamino-functionalized spiro-bisilole molecule as the emitter and as an electron-transport layer that eliminates exciplex formation is presented. The luminance–current-density–voltage diagram for the double-layer device shown here demonstrates its high emissivity.

    13. Rapid Synthesis of Amino Acid Polyoxometalate Nanotubes by One-Step Solid-State Chemical Reaction at Room Temperature (pages 687–692)

      R.-Y. Wang, D.-Z. Jia, L. Zhang, L. Liu, Z.-P. Guo, B.-Q. Li and J.-X. Wang

      Version of Record online: 9 FEB 2006 | DOI: 10.1002/adfm.200500549

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      Tyrosine (Tyr) polyoxometalate nanotubes (see Figure), (HTyr)3PMo12O40· 3H2O, (HTyr)3PW12O40·3H2O, and (HTyr)4SiW12O40·5H2O, have been synthesized via a one-step solid-state chemical reaction at room temperature. The method is a convenient synthesis technique, which merely depends on a simple combination of common compounds and room-temperature grinding.

    14. Au–Pd Alloy Gradients Prepared by Laterally Controlled Template Synthesis (pages 693–698)

      T. Sehayek, T. Bendikov, A. Vaskevich and I. Rubinstein

      Version of Record online: 2 FEB 2006 | DOI: 10.1002/adfm.200500655

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      The synthesis of compositional gradients of Au–Pd alloys by electrodeposition in a porous insulating template under a lateral potential drop is presented (see Figure). The alloy gradients are characterized by electron microscopy, energy dispersive spectrometry, and X-ray diffraction. Graded materials made by this method may be designed to display gradients of mechanical, chemical, electrical, optical, magnetic, or catalytic properties, in various geometries.

    15. Charge Transport and Photocurrent Generation in Poly(3-hexylthiophene): Methanofullerene Bulk-Heterojunction Solar Cells (pages 699–708)

      V. D. Mihailetchi, H. X. Xie, B. de Boer, L. J. A. Koster and P. W. M. Blom

      Version of Record online: 16 FEB 2006 | DOI: 10.1002/adfm.200500420

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      The effect of controlled thermal annealing on charge transport and photogeneration in bulk-heterojunction solar cells made from blend films of poly(3-hexylthiophene) (P3HT) and methanofullerene is investigated. The hole mobility in the P3HT phase of the blend is dramatically affected by annealing (see Figure). An increase in this hole mobility is the most important factor leading to a strong enhancement of the efficiency.

    16. Starburst DCM-Type Red-Light-Emitting Materials for Electroluminescence Applications (pages 709–718)

      Y.-S. Yao, J. Xiao, X.-S. Wang, Z.-B. Deng and B.-W. Zhang

      Version of Record online: 24 JAN 2006 | DOI: 10.1002/adfm.200500558

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      A new red-light-emitting organic compound, MBIN (a DCM derivative; see Figure), has been synthesized and used in a light-emitting diode. The device exhibits a high brightness (6971 cd m–2) and a high current efficiency (6.14 cd A–1), with the CIE chromaticity coordinates of the emission being (0.66, 0.33). These results have been achieved at a relatively high doping concentration (10 wt.-%) because of the restriction of the concentration-quenching effect.

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