Advanced Functional Materials

Cover image for Advanced Functional Materials

November, 2004

Volume 14, Issue 11

Pages 1031–1134

    1. A Biomimetic Artificial Disc with Improved Mechanical Properties Compared to Biological Intervertebral Discs (pages 1039–1046)

      Y. Shikinami, Y. Kotani, B. W. Cunningham, K. Abumi and K. Kaneda

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200305038

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      A novel stand-alone artificial intervertebral disc composed of three-dimensional fabrics with a triaxial fiber alignment that confers high biocompatibility and biomimetic stress–strain behavior is reported. The disc is shown to be capable of enduring more than sixty-three million repetitive loadings (equivalent to over thirty years in vivo; see Figure) and improves on biological intervertebral discs by reducing the risk of rupture and delamination.

    2. The Mobility and Decay Kinetics of Charge Carriers in Discotic Hexabenzocoronenes (pages 1047–1052)

      J. Piris, M. G. Debije, M. D. Watson, K. Müllen and J. M. Warman

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200400096

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      The intracolumnar mobility and decay kinetics of charge carriers in bulk samples of discotic hexa-peri-hexabenzocoronene derivatives (see Figure) are investigated as a function of temperature. The results are compared with those obtained on the optical and photoconductive properties of aligned thin films of the same materials in the paper that follows.

    3. Aligned Thin Films of Discotic Hexabenzocoronenes: Anisotropy in the Optical and Charge Transport Properties (pages 1053–1061)

      J. Piris, M. G. Debije, N. Stutzmann, B. W. Laursen, W. Pisula, M. D. Watson, T. Bjørnholm, K. Müllen and J. M. Warman

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200400182

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      Macroscopic columnar alignment of discotic materials is an essential prerequisite to their practical application in (opto)electronic devices. The anisotropy in the optical and charge transport properties of films prepared by different alignment techniques is compared (the Figure illustrates alignment by zone-casting).

    4. Single and Multiple-Step Dip-Coating of Colloidal Maghemite (γ-Fe2O3) Nanoparticles onto Si, Si3N4, and SiO2 Substrates (pages 1062–1068)

      T.-S. Yoon, J. Oh, S.-H. Park, V. Kim, B. G. Jung, S.-H. Min, J. Park, T. Hyeon and K.-B. Kim

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200305088

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      Ten-nanometer-sized colloidal maghemite (γ-Fe2O3) nanoparticles were adsorbed onto different substrates (Si, Si3N4, and SiO2) via single- and multiple-step dip-coating processes. Particle adsorption was found to depend on both the substrate and the particle concentration. In addition, particle monolayers were formed with coverages of about 0.76 on Si and about 0.61 on SiO2 using the multiple-step dip-coating process.

    5. Extracting Parameters from the Current–Voltage Characteristics of Organic Field-Effect Transistors (pages 1069–1074)

      G. Horowitz, P. Lang, M. Mottaghi and H. Aubin

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200305122

      Basic parameters of organic thin-film transistors, such as mobility and threshold voltage, are usually extracted form the current–voltage characteristics using simple formula developed for conventional inorganic field-effect transistors. However, organic devices present specific particularities, such as gate-voltage-dependent mobility and contact resistance, that require a deeper analysis of the data. In this study, various techniques for extracting mobility and threshold voltage are compared. The method is exemplified by measurements on pentacene-based devices built on alumina substrates, some of which have been modified by an eicosanoic acid self-assembled monolayer (SAM).

    6. Biogenic Calcium Carbonate: Calcite Crystals of Variable Morphology by the Reaction of Aqueous Ca2+ Ions with Fungi (pages 1075–1080)

      A. Ahmad, D. Rautaray and M. Sastry

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200400005

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      Biological synthesis of CaCO3 crystals of variable morphology using non-calcareous micro-organisms such as fungi is described. Significant differences in the morphology of the calcite crystals is observed (see Figure), indicating that the proteins secreted by the fungi play a crucial role in directing the crystal growth and hence the morphology.

    7. Spontaneous Formation of Ordered Lateral Patterns in Polymer Thin-Film Structures (pages 1081–1088)

      T. Okayasu, H.-L. Zhang, D. G. Bucknall and G. A. D. Briggs

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200305014

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      Surface topographic structures with well-defined periodicities have been observed after annealing of a metal-capped PS/Si model layered system (see Figure). Systems that contain prefabricated topographic patterns produce highly anisotropic surface topographies. The experimental data are in excellent agreement with a model based on stress relaxation of the metal capping layer.

    8. Facile Methods to Coat Polystyrene and Silica Colloids with Metal (pages 1089–1096)

      J. Zhang, J. Liu, S. Wang, P. Zhan, Z. Wang and N. Ming

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200400119

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      A complete metal shell with controlled thickness is reported to have been prepared on polystyrene and silica colloids by two methods: a solvent- assisted route and an electroless plating approach, respectively. The as-prepared complex core–shell colloids are shown to crystallize directly into long-range-ordered structures (see Figure, an image of an opal formed of silver-coated silica colloids) with photonic bandgaps.

    9. Suppression of the Keto-Emission in Polyfluorene Light-Emitting Diodes: Experiments and Models (pages 1097–1104)

      X. H. Yang, F. Jaiser, D. Neher, P. V. Lawson, J.-L. Brédas, E. Zojer, R. Güntner, P. Scanduicci de Freitas, M. Forster and U. Scherf

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200305012

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      The role of keto-defects on the charge carrier trapping and recombination in polyfluorene-based LEDs has been investigated (see Figure). The results strongly support the view that keto-defects function as weakly emissive electron traps. A simple model has been provided to explain the suppression of green emission upon addition of hole-trapping molecules.

    10. Efficient Isolation and Solubilization of Pristine Single-Walled Nanotubes in Bile Salt Micelles (pages 1105–1112)

      W. Wenseleers, I. I. Vlasov, E. Goovaerts, E. D. Obraztsova, A. S. Lobach and A. Bouwen

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200400130

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      A wide range of surfactants are investigated for solubilizing individual intact single-walled nanotubes –without chemical or ultrasonic treatment. Bile salts are found to be exceptionally effective, and their ordered micelles provide an unusually homogeneous environment for the tubes. This results in highly resolved optical absorption spectra, bright bandgap fluorescence, and unprecedented resolution (∼2.5 cm–1) of the radial breathing modes in Raman spectra (see Figure).

    11. The Synthesis of Novel Porous Functional Materials for use as Nitrosamine Traps (pages 1113–1123)

      Y. Xu, Q. Jiang, Y. Cao, Y. L. Wei, Z. Y. Yun, J. H. Xu, Y. Wang, C. F. Zhou, L. Y. Shi and J. H. Zhu

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200400009

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      The synthesis of two novel porous functional materials is reported: i) “in-situ coated” CuO/SBA-15 and ii) silica gel tailored via magnesia coating. They are proven to be effective nitrosamine trapper molecules and thus are classified as environmentally important due to their effective elimination of the carcinogenic substances contained in cigarette smoke. The Figure illustrates nitrosamine elimination from cigarette mainstream by CuO/SBA-15 and tailored silica samples.

    12. High Mechanical Strength Double-Network Hydrogel with Bacterial Cellulose (pages 1124–1128)

      A. Nakayama, A. Kakugo, J. P. Gong, Y. Osada, M. Takai, T. Erata and S. Kawano

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200305197

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      Double-network (DN) hydrogels combining the mechanical properties of bacterial cellulose (BC) with the water-retentive properties of gelatin are described. The hydrogels possess fracture strengths and elastic moduli on the order of megapascals, comparable to articular cartilage. The Figure compares the BC (left), gelatin (middle), and DN BC–gelatin (right) hydrogels before, during, and after compression.

    13. Poly(dithienylethene-alt-1,4-divinylenephenylene)s: Increasing the Molecular Weights in Diarylethene Photochromic Polymers (pages 1129–1133)

      C. Bertarelli, A. Bianco, V. Boffa, M. Mirenda, M. C. Gallazzi and G. Zerbi

      Version of Record online: 15 NOV 2004 | DOI: 10.1002/adfm.200304295

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      The photochromism of dithienylethene-alt-1,4-divinylenephenylene copolymers (see Figure) (obtained via the Horner and Wittig procedures) is investigated. The relatively high molecular weights of the furnished polymers allows the preparation of bulk amorphous films from solution processing.