Advanced Materials

Cover image for Vol. 17 Issue 22

November, 2005

Volume 17, Issue 22

Pages 2649–2772

    1. Cover Picture: Acceleration of Calcite Kinetics by Abalone Nacre Proteins (Adv. Mater. 22/2005)

      G. Fu, S. R. Qiu, C. A. Orme, D. E. Morse and J. J. De Yoreo

      Version of Record online: 9 NOV 2005 | DOI: 10.1002/adma.200590115

      Abalone shell nacre proteins act as surfactants to promote ion attachment at calcite steps, causing acceleration of the molecular-scale kinetics of calcite crystal growth. The proteins modify the shape of growing calcite (see Figure) through step-specific interactions, even though the proteins are larger than the atomic-scale steps. Understanding of crystal-growth control by interactions with proteins may give better control of new crystalline materials.

    2. Inside Front Cover: Selective Construction of Supramolecular Nanotube Hosts with Cationic Inner Surfaces (Adv. Mater. 22/2005)

      N. Kameta, M. Masuda, H. Minamikawa, N. V. Goutev, J. A. Rim, J. H. Jung and T. Shimizu

      Version of Record online: 9 NOV 2005 | DOI: 10.1002/adma.200590116

      Self-assembly of an unsymmetrical bolaamphiphile produces either lipid nanotubes with cationic inner surfaces or nanotapes, depending on the initial molecular packing, which in turn depends on the solvent conditions. The nanotubes have different inner and outer surfaces, covered with amino and sugar functionalities, respectively, and effectively encapsulate anionic nanomaterials in the hollow cylinder without depending on capillary action (see Figure).

    3. Supramolecular Complexes of Conjugated Polyelectrolytes with Poly(ethylene oxide): Multifunctional Luminescent Semiconductors Exhibiting Electronic and Ionic Transport (pages 2659–2663)

      J. S. Wilson, M. J. Frampton, J. J. Michels, L. Sardone, G. Marletta, R. H. Friend, P. Samorì, H. L. Anderson and F. Cacialli

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200401662

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      Cyclodextrin-threaded molecular wires form supramolecular complexes with polymers featuring ion-coordination properties. The supramolecular interactions reduce the tendency of the different components to phase separate boosting the photo- and electroluminescence (EL) efficiencies. The Figure shows the EL enhancement of poly(4,4′-diphenylene vinylene) (PDV) blended with polyethylene oxide (PEO) as a funcion of PEO concentration.

    4. Single-Walled Carbon Nanotube Polyelectrolyte Multilayers and Freestanding Films as a Biocompatible Platform for Neuroprosthetic Implants (pages 2663–2670)

      M. K. Gheith, V. A. Sinani, J. P. Wicksted, R. L. Matts and N. A. Kotov

      Version of Record online: 11 OCT 2005 | DOI: 10.1002/adma.200500366

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      Layer-by-layer (LBL) assembly has been used to prepare single-walled carbon nanotube (SWNT) freestanding structures that can be used for implantable devices with unique mechanical and electrical properties (see Figure). The thin LBL membranes prepared are biocompatible and support extensive neurite outgrowth. The stretched fiber-like LBL freestanding films exhibit neuronal guiding. The SWNT structures described may potentially enable connectivity between neurons.

    5. Dielectrophoresis and Chemically Mediated Directed Self-Assembly of Micrometer-Scale Three-Terminal Metal Oxide Semiconductor Field-Effect Transistors (pages 2671–2677)

      S. W. Lee and R. Bashir

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200501048

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      Micrometer-scale metal oxide semiconductor field-effect transistors (MOSFETs) self-assemble from a fluid onto a substrate, and are held in place during drying by application of a dielectrophoretic force or by interactions with a self-assembled monolayer. The assembled devices (see Figure) are fully functional. This approach might be used to assemble devices on flexible plastic or other substrates, or for 3D integration of silicon devices on chips.

    6. Acceleration of Calcite Kinetics by Abalone Nacre Proteins (pages 2678–2683)

      G. Fu, S. R. Qiu, C. A. Orme, D. E. Morse and J. J. De Yoreo

      Version of Record online: 11 OCT 2005 | DOI: 10.1002/adma.200500633

      Thumbnail image of graphical abstract

      Abalone shell nacre proteins act as surfactants to promote ion attachment at calcite steps, causing acceleration of the molecular-scale kinetics of calcite crystal growth. The proteins modify the shape of growing calcite (see Figure) through step-specific interactions, even though the proteins are larger than the atomic-scale steps. Understanding of crystal-growth control by interactions with proteins may give better control of new crystalline materials.

    7. Magnetic Nanocrescents as Controllable Surface-Enhanced Raman Scattering Nanoprobes for Biomolecular Imaging (pages 2683–2688)

      G. L. Liu, Y. Lu, J. Kim, J. C. Doll and L. P. Lee

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200501064

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      Magnetic nanocrescent Raman probes (see Figure) can not only serve as stand-alone surface-enhanced Raman scattering (SERS) substrates with high local electromagnetic-field enhancement factors, but can also be controlled by external magnetic fields to produce translational and rotational motion of the nanoprobes. Their near-IR optical activities may be useful for biomedical imaging, as near-IR radiation results in deeper tissue penetration and minimal photothermal damage.

    8. A Highly Transparent and Luminescent Hybrid Based on the Copolymerization of Surfactant-Encapsulated Polyoxometalate and Methyl Methacrylate (pages 2688–2692)

      H. Li, W. Qi, W. Li, H. Sun, W. Bu and L. Wu

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200500893

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      A polyoxometalate-based hybrid is produced by the copolymerization of a terminal-unsaturated surfactant- encapsulated polyoxometalate and methyl methacrylate. This hybrid exhibits flexible processability, high transparency of the polymer, and high fluorescence of the inorganic cluster (see Figure). The method presented in this paper provides general access to the fabrication of organic–inorganic electrostatic-complex-based materials in polymer matrices.

    9. An Organic Field-Effect Transistor with Programmable Polarity (pages 2692–2695)

      R. C. G. Naber, P. W. M. Blom, G. H. Gelinck, A. W. Marsman and D. M. de Leeuw

      Version of Record online: 22 SEP 2005 | DOI: 10.1002/adma.200500561

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      Selective ambipolar transport in solution-processed polymer ferroelectric field-effect transistors (FeFETs) is reported. Depending on the polarization state of the ferroelectric, either remanent hole or electron accumulation is achieved in the transistor, as illustrated by a butterfly-shaped current–voltage (I–V) transfer curve (see Figure). For memory purposes, the polarity of the channel can be easily read using the change in drain current in response to a small gate voltage.

    10. Anisotropic Polyion-Complex Gels from Template Polymerization (pages 2695–2699)

      Y. Shigekura, Y. M. Chen, H. Furukawa, T. Kaneko, D. Kaneko, Y. Osada and J. P. Gong

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200500707

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      Anisotropic gels containing a very small amount of liquid crystals have been prepared. The gels exhibit strong birefringence, even after swelling, under crossed polarizers, although the monomer solutions do not (see Figure). The swollen gels have a liquid-crystal concentration (CLC) of only 0.14 wt.-%.

    11. Self-Crimping Bicomponent Nanofibers Electrospun from Polyacrylonitrile and Elastomeric Polyurethane (pages 2699–2703)

      T. Lin, H. Wang and X. Wang

      Version of Record online: 5 OCT 2005 | DOI: 10.1002/adma.200500901

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      Nanofibers with side-by-side morphologies are electrospun from polyacrylonitrile and polyurethane using a microfluidic device. Laminar flow of the two polymer solutions through the device results in nanometer-diameter curly nanofibers with bicomponent cross-sections. The polyurethane half of the nanofibers can be dissolved in tetrahydrofuran, leaving a “U”-shaped cross-section as seen in the Figure.

    12. Achieving High Density of Adsorbed Hydrogen in Microporous Metal Organic Frameworks (pages 2703–2706)

      J. Y. Lee, L. Pan, S. P. Kelly, J. Jagiello, T. J. Emge and J. Li

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200500867

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      Two microporous metal organic framework structures are shown to possess hydrogen uptake capacities reaching 1.74 and 1.98 wt.-% at 77 K (1, 2, see Figure). These give the highest adsorbed H2 density reported thus far for metal-organic-based porous materials. The estimated pore volumes are 0.33 and 0.38 cm3 g–1 for 1 and 2.

    13. Polymerization of a Confined π-System: Chemical Synthesis of Tetrahedral Amorphous Carbon Nanoballs from Graphitic Carbon Nanocapsules (pages 2707–2710)

      C.-C. Chu, G.-L. Hwang, J.-W. Chiou, W.-F. Pong, C.-L. Lin, C.-Y. Tsai, H.-M. Lin, Y.-C. Chang, C.-S. Chang, A. H. Hsu, W.-L. Huang, J. Guo, P.-H. Chen and T.-Y. Luh

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200500757

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      Aziridination of graphitic carbon nanocapsules (CNCs) followed by pyrolysis at 700 °C at ambient pressure yields tetrahedral amorphous carbon nanoballs (CNBs, see Figure). Because of the pyramidal character of some of the double bonds in the derivatized CNCs, a radical chain mechanism is proposed to rationalize the transformation of C sp2 hybridization in the CNCs to C sp3 hybridization in the CNBs.

    14. Oligomeric Phenylenevinylene with Cross Dipole Arrangement and Amorphous Morphology: Enhanced Solid-State Luminescence Efficiency and Electroluminescence Performance (pages 2710–2714)

      F. He, H. Xu, B. Yang, Y. Duan, L. L. Tian, K. K. Huang, Y. G. Ma, S. Y. Liu, S. H. Feng and J. C. Shen

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200501239

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      A new oligo(phenylenevinylene) linking three distyrylbenzene (DSB) molecules through a central terphenyl group is reported (see Figure). The resultant DSB trimer with an amorphous structure in the solid state exhibits excellent thermal stability and intense blue photoluminescence. The maximum luminance approaching 4000 cd m–2 and efficiency up to 3.5 cd A–1 can be obtained in the corresponding light-emitting devices with a low turn-on voltage (∼4 V).

    15. Organic Double-Heterostructure Photovoltaic Cells Employing Thick Tris(acetylacetonato)ruthenium(III) Exciton-Blocking Layers (pages 2714–2718)

      B. P. Rand, J. Li, J. Xue, R. J. Holmes, M. E. Thompson and S. R. Forrest

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200500816

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      Bathocuproine (BCP) or tris(acetylacetonato)ruthenium(III) (Ru(acac)3) is used as the exciton-blocking layer (EBL) in photovoltaic cells. The difference in thickness-dependent efficiency characteristics between the blockers (see Figure) is that the Ru(acac)3 energy-level alignment allows for the transport of holes from the cathode to the C60 acceptor level, whereas BCP relies on metal-deposition-induced damage for charge transport.

    16. Directed Assembly of Nanoparticles onto Polymer-Imprinted or Chemically Patterned Templates Fabricated by Nanoimprint Lithography (pages 2718–2723)

      P. Maury, M. Escalante, D. N. Reinhoudt and J. Huskens

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200501072

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      Patterning of nanoparticles on surfaces (see Figure) is accomplished by a combination of nanoimprint lithography, self-assembly, and vertical deposition. Substrates patterned by a combination of topographical and chemical templates produce lines with a maximum resolution of 60 nm, compared with 300 nm for substrates patterned only chemically. Hexagonally close-packed 50 nm clusters are obtained by using substrates patterned with circles rather than lines.

    17. Microfluidic Valves Comprising Nanolayered Thermoresponsive Polymer-Grafted Capillaries (pages 2723–2727)

      N. Idota, A. Kikuchi, J. Kobayashi, K. Sakai and T. Okano

      Version of Record online: 22 SEP 2005 | DOI: 10.1002/adma.200402068

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      Thermally regulated flow control using a thermoresponsive polymer grafted onto surfaces of capillary lumen facilitates rapid, reliable, and repeatable open–close cycles (see Figure). Hydration of the grafted polymer chains on the internal surfaces may increase the microviscosity of the hydration layers at the wall interfaces without physically occluding the lumen, producing complete and reversible on/off flow valving in microchannels under hydrostatic pressures relevant for microfluidics approaches.

    18. Synthesis and Electronic Properties of Individual Single-Walled Carbon Nanotube/Polypyrrole Composite Nanocables (pages 2727–2732)

      X. Liu, J. Ly, S. Han, D. Zhang, A. Requicha, M. E. Thompson and C. Zhou

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200501211

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      Nanocable devices (see Figure) of individual single-walled carbon nanotube/polypyrrole (PPy) and their synthesis, transport studies, and chemical-sensing applications are investigated. They exhibit suppressed conductance, in contrast to the anticipated combined conductance from the nanotubes and PPy. Further deposition of PPy leads to a recovery in conductance. These devices are demonstrated to work as chemical sensors.

    19. Selective Construction of Supramolecular Nanotube Hosts with Cationic Inner Surfaces (pages 2732–2736)

      N. Kameta, M. Masuda, H. Minamikawa, N. V. Goutev, J. A. Rim, J. H. Jung and T. Shimizu

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200501092

      Thumbnail image of graphical abstract

      Self-assembly of an unsymmetrical bolaamphiphile produces either lipid nanotubes with cationic inner surfaces or nanotapes, depending on the initial molecular packing, which in turn depends on the solvent conditions. The nanotubes have different inner and outer surfaces, covered with amino and sugar functionalities, respectively, and effectively encapsulate anionic nanomaterials in the hollow cylinder without depending on capillary action (see Figure).

    20. Patterning of Conducting Polymers Based on a Random Copolymer Strategy: Toward the Facile Fabrication of Nanosensors Exclusively Based on Polymers (pages 2736–2741)

      B. Dong, D. Y. Zhong, L. F. Chi and H. Fuchs

      Version of Record online: 22 SEP 2005 | DOI: 10.1002/adma.200500938

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      Fabrication of a nanosensor consisting exclusively of polymers with sensing performance superior to a microscale sensor is reported. The device is fabricated by a copolymer strategy combined with a lift-off process, which is capable of patterning a variety of conducting polymer species down to the nanometer scale (see Figure).

    21. Synthesis, Characterization, and Spectroscopy of Type-II Core/Shell Semiconductor Nanocrystals with ZnTe Cores (pages 2741–2745)

      R. Xie, X. Zhong and T. Basché

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200501029

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      Type-II core/shell quantum dots are characterized by a staggered alignment of conduction and valence bands (see Figure), giving rise to a broad tunability of absorption and emission wavelengths. Colloidal ZnTe/CdE (E = S, Se, Te) core/shell quantum dots have been prepared with emission quantum yields of up to 30 %. The synthesis route presented should be applicable to other type-II core/shell quantum dots.

    22. Fabrication of Vertically Well-Aligned (Zn,Mn)O Nanorods with Room Temperature Ferromagnetism (pages 2745–2748)

      J. M. Baik and J.-L. Lee

      Version of Record online: 22 SEP 2005 | DOI: 10.1002/adma.200500776

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      Vertically well-aligned (Zn,Mn)O nanorods (see Figure) that show ferromagnetic behavior at room temperature have been grown on sapphire substrates by chemical vapor deposition. The high optical quality of the nanorods has been demonstrated by photoluminescence spectroscopy. These nanowires may find use in future nanoscale magneto-optic and magneto-electronic applications.

    23. Nanostructured Polyelectrolyte Multilayer Organic Thin Films Generated via Parallel Dip-Pen Nanolithography (pages 2749–2753)

      S. W. Lee, R. G. Sanedrin, B.-K. Oh and C. A. Mirkin

      Version of Record online: 5 OCT 2005 | DOI: 10.1002/adma.200501120

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      Polyelectrolyte multilayer (PEM) organic thin films with diameters ranging from 80 to 200 nm can be generated from dip-pen nanolithography (DPN) fabricated templates. Through the use of multi-pen AFM cantilever probes, parallel fabrication of PEM features with nanoscale resolution can be achieved. This demonstrates the versatility of the parallel DPN approach and its applicability to building nano-/microscale structures in conjunction with a layer-by-layer method.

    24. High-Power Alkaline Zn–MnO2 Batteries Using γ-MnO2 Nanowires/Nanotubes and Electrolytic Zinc Powder (pages 2753–2756)

      F. Y. Cheng, J. Chen, X. L. Gou and P. W. Shen

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200500663

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      High-power alkaline Zn–MnO2 batteries with superior discharge performance have been constructed using γ-MnO2 nanowires/nanotubes (see Figure) and electrolytic zinc powder as the cathode and anode active materials, respectively. The improvement in discharge performance over commercial batteries is believed to be derived from the lower inner resistance of the batteries and the high utilization efficiency of the active materials.

    25. Chemically Bonded Ceramic Oxide Coatings on Carbon Nanotubes and Inorganic Nanowires (pages 2757–2761)

      A. Gomathi, S. R. C. Vivekchand, A. Govindaraj and C. N. R. Rao

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200500539

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      Acid-treated carbon nanotubes are reacted with metal halides and water and are then calcined to produce a chemically bonded oxide layer of controllable thickness on the nanotubes (see Figure). Similar coatings are prepared on aluminum oxide and silicon nanowires by the reaction of the metal halides with the surface hydroxyl groups present on the nanowire surfaces. Potential applications include in sensors, insulation, and high-toughness composites.

    26. ZnO Inverse Opals by Chemical Vapor Deposition (pages 2761–2765)

      B. H. Juárez, P. D. García, D. Golmayo, A. Blanco and C. López

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200500569

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      Inverted opals are of great interest as photonic materials. Here, an inexpensive chemical vapor deposition method of synthesis of ZnO and ZnS inverse opals (see Figure) is described, based on infiltration and calcination of ZnO in synthetic polystyrene opals. Excellent control of the degree of infiltration, i.e., the layer thickness of ZnO, and thus the properties of the material, is reported.

    27. The Dynamics of Nanowire Self-Assembly (pages 2765–2768)

      M. Chen and P. C. Searson

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/adma.200501292

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      Multisegment Au/Ni/Au nanowires have been used as a model system to explore the dynamics of receptor-mediated self-assembly. Light microscopy (top) and fluorescence (bottom) images of a 300 nm diameter and 4.5 μm long Au/Ni/Au nanowire are shown in the Figure, where the gold end segments have been functionalized with fluorescently labeled avidin to direct end-to-end assembly.

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