Advanced Materials

Cover image for Vol. 17 Issue 13

July, 2005

Volume 17, Issue 13

Pages 1571–1688

    1. Cover Picture: Polyaniline Nanofibers Prepared by Dilute Polymerization (Adv. Mater. 13/2005)

      N.-R. Chiou and A. J. Epstein

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200590066

      Polyaniline nanofibers (see Figure and cover) have been synthesized using dilute polymerization with reduced concentrations of both monomer and oxidant and a constant molar ratio. The diameters of the polyaniline nanofibers are tunable by appropriate selection of dopant acids. A dispersion of polyaniline nanofibers could be cast to form highly porous nanofibrous films without deformation of the nanofiber morphology.

    2. Inside Front Cover: Self-Assembly and Magnetism of Mn12 Nanomagnets on Native and Functionalized Gold Surfaces (Adv. Mater. 13/2005)

      A. Naitabdi, J.-P. Bucher, Ph. Gerbier, P. Rabu and M. Drillon

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200590067

      Mn12 single molecule magnets (SMMs) survive organized grafting on Au(111) surfaces as shown by a magnetic study in the monolayer range (see Figure and inside cover). Although the magnetic features are still reminiscent of ferromagnetic SMMs, effects due to the reduced dimensionality are clearly visible. Individual molecules are identified by scanning tunneling microscopy, opening new opportunities in the field of addressable, high-density, molecular devices for data storage and spin electronics.

    3. The Versatile Thiophene: An Overview of Recent Research on Thiophene-Based Materials (pages 1581–1593)

      G. Barbarella, M. Melucci and G. Sotgiu

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200402020

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      Thiophene-based oligomers and polymers are not only important materials for electronics and optoelectronics (see Figure) but they also have great potential as fluorimetric or colorimetric indicators for recognition events involving proteins or DNA. This progress report details recent research on synthesis, supramolecular organization, devices, applications in biodiagnostics, and theoretical calculations.

    4. Controlled Growth and Field-Emission Properties of Cobalt Oxide Nanowalls (pages 1595–1599)

      T. Yu, Y. W. Zhu, X. J. Xu, Z. X. Shen, P. Chen, C.-T. Lim, J. T.-L. Thong and C.-H. Sow

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200500322

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      Vertically oriented single-crystalline Co3O4 nanowalls (see Figure) have been successfully fabricated by directly heating Co foil in air using a hot plate. The morphologies of the Co3O4 nanowalls can be controlled by varying the growth temperature and time. The Co3O4 nanowalls show promising field-emission performance that is comparable to many other nanomaterials.

    5. Achieving High Strength and High Ductility in Precipitation-Hardened Alloys (pages 1599–1602)

      Z. Horita, K. Ohashi, T. Fujita, K. Kaneko and T. G. Langdon

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200500069

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      Ultrafine-grained materials may be produced by applying severe plastic deformation, but these materials generally exhibit high strength and limited ductility. This report describes a technique for producing high strength and high ductility (see Figure) in precipitation-hardened alloys at ambient temperatures based on introducing intermediate metastable phases into ultrafine-grained microstructures.

    6. Cadmium Nanowire Formation Induced by Ion Irradiation (pages 1602–1606)

      W. Jiang, W. J. Weber, C. M. Wang, J. S. Young, L. A. Boatner, J. Lian, L. M. Wang and R. C. Ewing

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200500118

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      Crystalline Cd nanowires (see Figure) are synthesized by extrusion/pulling of a decomposed Cd2Nb2O7 single crystal, in which decomposition and phase separation are induced by He+ irradiation. During the formation, soft metallic Cd is extruded/pulled out as nanowires through pores in the exfoliated layer and the underlying substrate. The nanowire has a crystalline Cd core with a thin shell of CdO that formed upon exposure to air.

    7. The Effect of Oxygen Vacancies in the Early Stages of BaTiO3 Nanopowder Sintering (pages 1606–1608)

      R. D. Levi and Y. Tsur

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200401859

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      The influence of process atmosphere during sintering is an aspect of nanopowder processing that has not been widely investigated. Reducing the chemical potential of oxygen promotes the beginning of sintering in nanopowder particles of a model oxide material. The importance of oxygen vacancies is shown by both sintering in low oxygen partial pressures and doping with acceptors (see Figure).

    8. Nanometer-Scale Patterning of DNA in Controlled Intervals on a Gold-Disk Array Fabricated Using Ideally Ordered Anodic Porous Alumina (pages 1609–1612)

      F. Matsumoto, M. Harada, K. Nishio and H. Masuda

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200401037

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      Ideally ordered DNA nanopatterns have been formed by selectively opening holes in a barrier layer covering gold-filled anodic porous alumina, and then adsorbing thiolated DNA onto the exposed gold nanodisks. Fluorescence microscopy of fluorescent-dye-labeled thiolated DNA fixed on the gold-disk array confirms the selectivity of the process (see Figure).

    9. Self-Assembly and Magnetism of Mn12 Nanomagnets on Native and Functionalized Gold Surfaces (pages 1612–1616)

      A. Naitabdi, J.-P. Bucher, Ph. Gerbier, P. Rabu and M. Drillon

      Version of Record online: 18 APR 2005 | DOI: 10.1002/adma.200401623

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      Mn12 single molecule magnets (SMMs) survive organized grafting on Au(111) surfaces as shown by a magnetic study in the monolayer range (see Figure and inside cover). Although the magnetic features are still reminiscent of ferromagnetic SMMs, effects due to the reduced dimensionality are clearly visible. Individual molecules are identified by scanning tunneling microscopy, opening new opportunities in the field of addressable, high-density, molecular devices for data storage and spin electronics.

    10. Chemical Sensors Based on Highly Conductive Poly(3,4-ethylenedioxythiophene) Nanorods (pages 1616–1620)

      J. Jang, M. Chang and H. Yoon

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200401909

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      PEDOT nanorods have been fabricated using reverse cylindrical micelle-mediated interfacial polymerization without any templates and applied as chemical sensors for the detection of HCl and NH3 vapor. The PEDOT nanorods, shown in the Figure, display very stable conductivity. The chemical sensors can detect low vapor concentrations and exhibit a reversible and reproducible response.

    11. Robust, Non-Cytotoxic, Silica-Coated CdSe Quantum Dots with Efficient Photoluminescence (pages 1620–1625)

      S. T. Selvan, T. T. Tan and J. Y. Ying

      Version of Record online: 4 MAY 2005 | DOI: 10.1002/adma.200401960

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      Water-soluble quantum dots (QDs) have been prepared by encapsulation within silica via a reverse microemulsion (see Figure). The QDs display comparable quantum yields to ZnS-capped CdSe, but are much less toxic than organic-coated water-soluble QDs. This method could be used for QD applications such as in biological labeling and in photostable light-emitting devices.

    12. Microfabrication of Multilayer, Asymmetric, Polymeric Devices for Drug Delivery (pages 1625–1630)

      S. L. Tao and T. A. Desai

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200500017

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      Multilayered, asymmetric vehicles have been constructed with 3D features that may provide the capacity to target cells, promote unidirectional controlled release, and enhance permeation across the intestinal epithelial barrier. The Figure shows microfabricated PMMA devices and their specific interactions (postchemical surface modification) with a human colonic cell line expressing enterocytic differentiation.

    13. Wavelength-Programmable Organic Distributed-Feedback Laser Based on a Photoassisted Polymer-Migration System (pages 1630–1633)

      T. Ubukata, T. Isoshima and M. Hara

      Version of Record online: 18 APR 2005 | DOI: 10.1002/adma.200402080

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      A novel organic distributed-feedback laser with programmable lasing wavelengths is described. The laser is based on a double-layered structure composed of an azopolymer layer that forms a surface relief grating (SRG) and a dye-doped polymer layer that provides optical gain. The lasing wavelength is programmed by erasing and rewriting the azopolymer SRG with an interference pattern of a different period (see Figure).

    14. In-Situ Fabrication of Freestanding Single-Walled Carbon Nanotube–Silicate Composite Hex Nuts (pages 1634–1637)

      R. Colorado Jr., M. E. Diosomito and A. R. Barron

      Version of Record online: 4 MAY 2005 | DOI: 10.1002/adma.200400836

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      Freestanding “hex nuts” composed of a single-walled carbon nanotube (SWNT)–silicate composite (see Figure) have been fabricated from mats of silica-coated SWNTs using a novel dissolution/regrowth process. This approach simultaneously generates large numbers of composites with well-defined shapes and uniform dimensions. Discrete steps of this fabrication process are discussed.

    15. Freeze-Drying of Soft Nanoparticles with Projection Coronas Forms Three-Dimensional Microconstructs (pages 1638–1643)

      T. Kaneko, K. Hamada, M. Q. Chen and M. Akashi

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200401288

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      Freeze-drying of polymeric nanoparticles with projection coronas results in the successful formation of three-dimensional microconstructs with various morphologies, including hollow microspheres (see Figure), without a solid or colloidal template. The microconstructs have sufficient mechanical strength to redisperse successfully in water without collapsing, while they break into nanoparticles following successive freeze–thawing cycles.

    16. Self-Assembly of Crosslinked DNA–Gold Nanoparticle Layers Visualized by In-Situ Scanning Force Microscopy (pages 1643–1647)

      B. Zou, B. Ceyhan, U. Simon and C. M. Niemeyer

      Version of Record online: 11 MAY 2005 | DOI: 10.1002/adma.200402037

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      Two-dimensional streptavidin crystals are used as the substrate for DNA-directed assembly of crosslinked gold-nanoparticle aggregates (see Figure). As shown by in-situ scanning force microscopy, the interparticle distance can be controlled by the length of the DNA linker connecting individual particles. This system may lead to nanostructured materials with programmable functionalities for use in nanobiotechnology.

    17. Preparation and Characterization of Well-Ordered Hexagonal Mesoporous Carbon Nitride (pages 1648–1652)

      A. Vinu, K. Ariga, T. Mori, T. Nakanishi, S. Hishita, D. Golberg and Y. Bando

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200401643

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      A well-ordered mesoporous carbon nitride material has been prepared by the polymerization reaction between ethylenediamine and carbon tetrachloride. This material has a highly ordered hexagonal pore system (see Figure), a high surface area, a large pore volume, and a uniform mesopore size distribution. Potential applications include use in catalytic supports, gas storage, lubricants, and drug delivery.

    18. Aligned Carbon Nanotube Composite Films for Thermal Management (pages 1652–1656)

      H. Huang, C. H. Liu, Y. Wu and S. Fan

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200500467

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      An ideal composite film based on a carbon nanotube (CNT) array for thermal management applications is prepared using “in-situ injection molding”. The aligned CNTs with their tips protruding out of both surfaces form ideal thermal conducting paths between surfaces. Much better thermal conductivity improvements can be achieved at low CNT loadings compared with dispersed CNT composites.

    19. Gold Nanocrystal Formation on Viologen-Functionalized Polymeric Nanospheres (pages 1656–1661)

      L. Cen, K. G. Neoh and E. T. Kang

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200500100

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      Poly(vinylbenzyl chloride) (PVBC) nanospheres synthesized via emulsion polymerization are used as the substrate for subsequent attachment of viologen moieties. The viologen-functionalized nanospheres can undergo photoinduced reaction with gold ions resulting in the formation of well-dispersed gold nanocrystals with diameters ranging from a few nanometers (see Figure, left) to 15 nm (Figure, right).

    20. Twinning-Mediated Growth of Al2O3 Nanobelts and Their Enhanced Dielectric Responses (pages 1661–1665)

      X.-S. Fang, C.-H. Ye, L.-D. Zhang and T. Xie

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200401921

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      The twinning-mediated growth of Al2O3 nanobelts (see Figure) is successfully achieved by simple thermal evaporation. The as-synthesized Al2O3 nanobelts are composed of deformation twins along their entire length. The particular structures of these Al2O3 nanobelts apparently mimic those of plants such as bamboo, and their excellent dielectric properties may be significant for microstructural design of nanostructured materials and devices.

    21. Filled Microcavity Arrays Produced by Polyelectrolyte Multilayer Membrane Transfer (pages 1665–1669)

      M. Nolte, B. Schoeler, C. S. Peyratout, D. G. Kurth and A. Fery

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200402019

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      Arrays of microcavities sealed by a semipermeable ultrathin polyelectrolyte multilayer membrane (see Figure) are prepared using a novel method. The cavities can be loaded with high-molecular-weight species. If the entrapped molecules have stimuli-responsive properties, such structures can be potentially used as sensor arrays to probe, e.g., solution properties, as demonstrated in model experiments.

    22. Freely Suspended Gold Nanoparticle Arrays (pages 1669–1673)

      C. Jiang, S. Markutsya, H. Shulha and V. V. Tsukruk

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200500016

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      Freely suspended gold nanoparticle arrays have been fabricated by encapsulation into layer-by-layer nanomembranes. Such nanomembranes (see Figure) retain outstanding micromechanical properties and have an anisotropic mechanical response due to the uniformly oriented nanoparticle-containing stripes. Periodic variation of the Raman scattering across the microarrays is displayed (inset).

    23. Liquid Crystals of DNA-Stabilized Carbon Nanotubes (pages 1673–1676)

      S. Badaire, C. Zakri, M. Maugey, A. Derré, J. N. Barisci, G. Wallace and P. Poulin

      Version of Record online: 4 MAY 2005 | DOI: 10.1002/adma.200401741

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      Water-based liquid crystals of unfunctionalized carbon nanotubes are reported for the first time (see Figure, scale bar: 50 μm). Denatured DNA is used to stabilize the nanotube suspensions. The average length and diameter of the nanotubes are measured using dynamic light scattering. The phase diagram of the system is discussed on the basis of these dimensional characterizations.

    24. Conical Carbon Filaments with Axial Cylindrical Channels and Open Tips (pages 1677–1679)

      W. Xia, D. Su, R. Schlögl, A. Birkner and M. Muhler

      Version of Record online: 1 JUL 2005 | DOI: 10.1002/adma.200500241

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      Conical carbon filaments with axial cylindrical channels and open tips (see Figure) supported on vapor-grown carbon microfibers can be prepared by iron-catalyzed pyrolysis of methane. The filament tips are single-walled and the cylindrical channels are open at the tip, opening the possibility of transporting fluids in nanochannels. The dimension of the base was on the micrometer scale, allowing handling or assembly of the filaments.

    25. Polyaniline Nanofibers Prepared by Dilute Polymerization (pages 1679–1683)

      N.-R. Chiou and A. J. Epstein

      Version of Record online: 4 MAY 2005 | DOI: 10.1002/adma.200401000

      Thumbnail image of graphical abstract

      Polyaniline nanofibers (see Figure and cover) have been synthesized using dilute polymerization with reduced concentrations of both monomer and oxidant and a constant molar ratio. The diameters of the polyaniline nanofibers are tunable by appropriate selection of dopant acids. A dispersion of polyaniline nanofibers could be cast to form highly porous nanofibrous films without deformation of the nanofiber morphology.

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