Advanced Materials

Cover image for Vol. 18 Issue 2

January, 2006

Volume 18, Issue 2

Pages 135–250

    1. Cover Picture: Direction-Dependent Homoepitaxial Growth of GaN Nanowires (Adv. Mater. 2/2006)

      H. Li, A. H. Chin and M. K. Sunkara

      Article first published online: 11 JAN 2006 | DOI: 10.1002/adma.200690009

      GaN nanowires with vastly different morphologies depending upon the growth direction are produced by direct nitridation and vapor transport of Ga in disassociated ammonia. Nanowires grown homoepitaxially along the c-direction develop hexagonal-prism island morphologies (see Figure, left, and Cover), while wires grown along the a-direction form uniform, belt-shaped morphologies (Figure, right). A “ballistic” transport phenomenon for adatoms is proposed to explain the observed prismatic island morphologies.

    2. Inside Front Cover: Experimental Evidence for Superprism Effects in Three-Dimensional Polymer Photonic Crystals (Adv. Mater. 2/2006)

      J. Serbin and M. Gu

      Article first published online: 11 JAN 2006 | DOI: 10.1002/adma.200690010

      Evidence for highly dispersive light propagation inside three-dimensional photonic crystals is presented theoretically (see Figure and inside Cover) as well as experimentally. Polymer woodpile structures having a bandgap in the near-infrared wavelength range have been fabricated by means of two-photon polymerization, and the directions of the wavelength-dependent light propagation inside the structures has been measured.

    3. Contents: Adv. Mater. 2/2006 (pages 135–142)

      Article first published online: 11 JAN 2006 | DOI: 10.1002/adma.200690006

    4. Electronic Characterization of Organic Thin Films by Kelvin Probe Force Microscopy (pages 145–164)

      V. Palermo, M. Palma and P. Samorì

      Article first published online: 8 DEC 2005 | DOI: 10.1002/adma.200501394

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      Kelvin probe force microscopy (KPFM) allows the simultaneous study of the structural and electronic properties of functional surfaces with resolutions of a few nanometers and some millivolts, complementing the information provided by scanning force microscopy (SFM). By unraveling the electronic (and dynamic) properties of materials, it enables the optimization of the design and performance of new devices based on organic-semiconductor nanoarchitectures.

    5. Three-Dimensional Microfluidic Tissue-Engineering Scaffolds Using a Flexible Biodegradable Polymer (pages 165–169)

      C. J. Bettinger, E. J. Weinberg, K. M. Kulig, J. P. Vacanti, Y. Wang, J. T. Borenstein and R. Langer

      Article first published online: 8 DEC 2005 | DOI: 10.1002/adma.200500438

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      Three-dimensional microfluidic networks using a flexible biodegradable polymer have been fabricated using modified microfabrication processes tailored specifically for poly(glycerol-co-sebacate). A model hepatocyte cell line (HepG2) is seeded and perfused in the microfluidic networks to demonstrate cell viability and function, which is maintained in long-term perfusion culture (see Figure; scale bar is 50 μm). The seeded, fully degradable device can potentially be integrated into a patient's existing vasculature in order to restore organ function.

    6. Organic Light-Emitting Transistors Based on Solution-Cast and Vacuum-Sublimed Films of a Rigid Core Thiophene Oligomer (pages 169–174)

      F. Cicoira, C. Santato, M. Melucci, L. Favaretto, M. Gazzano, M. Muccini and G. Barbarella

      Article first published online: 8 DEC 2005 | DOI: 10.1002/adma.200501639

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      A new organic multifunctional material, a rigid core thiophene oligomer, has been designed and synthesized. In both solution-processed and vacuum-sublimed films, the delicate balance of forces needed to obtain a supramolecular organization that imparts good charge transport and electroluminescence has been achieved, with the films being successfully employed as active layers in organic light-emitting (field-effect) transistors (see Figure).

    7. Highly Periodic Fullerene Nanomesh (pages 174–177)

      N. Néel, J. Kröger and R. Berndt

      Article first published online: 5 DEC 2005 | DOI: 10.1002/adma.200500913

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      Fullerene nanomesh: Fullerene islands with rectangular shapes organize themselves on a vicinal gold surface in an extraordinarily well-ordered mesh with unprecedented periodicity and low defect density (see Figure). This adsorbate system is a promising candidate for guiding subsequent deposition of functional units.

    8. A Supramolecular Chiroptical Switch Exclusively from an Achiral Amphiphile (pages 177–180)

      P. Guo, L. Zhang and M. Liu

      Article first published online: 8 DEC 2005 | DOI: 10.1002/adma.200501047

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      Although amphiphilic TARC18 is achiral (Figure, left), it can form chiral Langmuir–Schaefer (LS) films upon organization of the molecules at the air/water interface. Moreover, the chirality of the film can be switched off and recovered by alternatively exposing the film to HCl gas and air (Figure, right; CD: circular dichroism). The process can be repeated more than ten times in the film state.

    9. Carbon Nanotubes Coated with Alumina as Gate Dielectrics of Field-Effect Transistors (pages 181–185)

      L. Fu, Y. Q. Liu, Z. M. Liu, B. X. Han, L. C. Cao, D. C. Wei, G. Yu and D. B. Zhu

      Article first published online: 5 DEC 2005 | DOI: 10.1002/adma.200501324

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      Based on a simple low-temperature chemical-solution method, multiwalled carbon nanotubes (MWCNTs) are coated discontinuously with a alumina gate-dielectric shell (see Figure) and application as p-type field-effect transistors is demonstrated. With a coating thickness of 8 nm, the drain current exceeds the gate current by a factor of 104–105, confirming the excellent gate insulation provided by the alumina dielectric.

    10. Transparent Zeolite Films with Regular Surface Patterns (pages 185–189)

      G. Shu, J. Liu, A. S. T. Chiang and R. W. Thompson

      Article first published online: 14 DEC 2005 | DOI: 10.1002/adma.200401980

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      Surfactant/zeolite precursor hybrid layers coated on flat substrates are steamed under controlled humidity to produce transparent zeolite (silicalite) films with regular surface patterns (see Figure). The surface pattern changes depending on the type of non-ionic surfactant used. Zeolite films produced show a contact angle of approximately zero for n-octane, but the contact angle for water varies from zero to 140°.

    11. Luminescent Carbon Nanotubes by Surface Functionalization (pages 189–193)

      D. L. Shi, J. Lian, W. Wang, G. K. Liu, P. He, Z. Dong, L. M. Wang and R. C. Ewing

      Article first published online: 21 DEC 2005 | DOI: 10.1002/adma.200501680

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      Multiwalled carbon nanotubes functionalized with europium-doped Y2O3 nanophosphors gives rise to species that are luminescent in the visible-light range. The surface morphologies and microstructure have been characterized by high-resolution transmission electron microscopy and Z-contrast imaging (see Figure). Such species may find potential applications in cancer diagnosis and treatment.

    12. Defect-Mode Lasing with Lowered Threshold in a Three-Layered Hetero-Cholesteric Liquid-Crystal Structure (pages 193–197)

      M. H. Song, N. Y. Ha, K. Amemiya, B. Park, Y. Takanishi, K. Ishikawa, J. W. Wu, S. Nishimura, T. Toyooka and H. Takezoe

      Article first published online: 8 DEC 2005 | DOI: 10.1002/adma.200501438

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      A novel defect mode is realized in a three-layered structure: a left-handed cholesteric liquid crystal (CLC) layer sandwiched between right-handed CLC films (see Figure). The defect states emerge, and the photonic density of state is resonantly enhanced when the defect mode coincides with the edge mode. The lasing from this enhanced mode is found to show a lower threshold value.

    13. Tapered Carbon Nanotubes from Activated Carbon Powders (pages 197–200)

      J. Q. Hu, Y. Bando, J. H. Zhan, C. Y. Zhi, F. F. Xu and D. Golberg

      Article first published online: 21 DEC 2005 | DOI: 10.1002/adma.200501571

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      Tapered carbon nanotubes (TCNTs) are produced from activated carbon powders via simple thermal catalytic reactions in which the carbon nanotubes grow though a Sn-catalyzed vapor–liquid–solid growth process. The tapered nanotubes are well aligned and have a length of several tens of micrometers (see Figure).

    14. Functional Porous Structures Based on the Pyrolysis of Cured Templates of Block Copolymer and Phenolic Resin (pages 201–205)

      H. Kosonen, S. Valkama, A. Nykänen, M. Toivanen, G. ten Brinke, J. Ruokolainen and O. Ikkala

      Article first published online: 8 DEC 2005 | DOI: 10.1002/adma.200401110

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      Porous materials with controlled pore size and large surface area (see Figure) have been prepared by crosslinking phenolic resin in the presence of a self-assembled block-copolymer template, followed by pyrolysis. Many phenolic hydroxyl groups remain at the matrix and pore walls, which can be used for selective and efficient absorption or further functionalization.

    15. Amphiphilic Diblock Copolymer Compatibilizers and Their Effect on the Morphology and Performance of Polythiophene:Fullerene Solar Cells (pages 206–210)

      K. Sivula, Z. T. Ball, N. Watanabe and J. M. J. Fréchet

      Article first published online: 8 DEC 2005 | DOI: 10.1002/adma.200501787

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      A diblock copolymer containing a fullerene(C60)-rich block and a poly(3-hexylthiophene) block functions as a compatibilizer in poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM) blends. The copolymer is used to probe the impact of morphology and phase-segregation kinetics on the performance of P3HT:PCBM-based solar cells.

    16. A Semiconductor-Nanowire Assembly of Ultrahigh Junction Density by the Langmuir–Blodgett Technique (pages 210–213)

      S. Acharya, A. B. Panda, N. Belman, S. Efrima and Y. Golan

      Article first published online: 5 DEC 2005 | DOI: 10.1002/adma.200501234

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      The assembly of ultrathin ZnSe nanowires over large areas (see Figure) is achieved by a Langmuir–Blodgett technique in a single step with uniform registry, and without any further secondary technique for alignment. Ultrahigh packing density of junctions, exceeding over 60 × 103 μm–2, is achieved by subsequent deposition of a second two-dimensional nanowire assembly with a controlled angle between the two layers. The resulting network notably surpasses the limit of conventional fabrication techniques.

    17. Lasing from Two-Dimensional Photonic Crystals Using Anodic Porous Alumina (pages 213–216)

      H. Masuda, M. Yamada, F. Matsumoto, S. Yokoyama, S. Mashiko, M. Nakao and K. Nishio

      Article first published online: 5 DEC 2005 | DOI: 10.1002/adma.200401940

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      Mirrorless laser emission from fluorescent dye-loaded anodic porous alumina with an ideally arranged hole array configuration is observed. The wavelength of the laser emission (see Figure) appears at the edge of the photonic bandgap in the two-dimensional photonic bandgap that originates from the anodic porous alumina, and can be tuned by changing the geometrical structure of the anodic porous alumina.

    18. Direction-Dependent Homoepitaxial Growth of GaN Nanowires (pages 216–220)

      H. Li, A. H. Chin and M. K. Sunkara

      Article first published online: 8 DEC 2005 | DOI: 10.1002/adma.200501716

      Thumbnail image of graphical abstract

      GaN nanowires with vastly different morphologies depending upon the growth direction are produced by direct nitridation and vapor transport of Ga in disassociated ammonia. Nanowires grown homoepitaxially along the c-direction develop hexagonal-prism island morphologies (see Figure, left, and Cover), while wires grown along the a-direction form uniform, belt-shaped morphologies (Figure, right). A “ballistic” transport phenomenon for adatoms is proposed to explain the observed prismatic island morphologies.

    19. Experimental Evidence for Superprism Effects in Three-Dimensional Polymer Photonic Crystals (pages 221–224)

      J. Serbin and M. Gu

      Article first published online: 11 JAN 2006 | DOI: 10.1002/adma.200501665

      Thumbnail image of graphical abstract

      Evidence for highly dispersive light propagation inside three-dimensional photonic crystals is presented theoretically (see Figure and inside Cover) as well as experimentally. Polymer woodpile structures having a bandgap in the near-infrared wavelength range have been fabricated by means of two-photon polymerization, and the directions of the wavelength-dependent light propagation inside the structures has been measured.

    20. Highly Ordered Organic Alq3 Chiral Luminescent Thin Films Fabricated by Glancing-Angle Deposition (pages 224–228)

      P. C. P. Hrudey, K. L. Westra and M. J. Brett

      Article first published online: 21 DEC 2005 | DOI: 10.1002/adma.200501714

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      Organic porous chiral thin films of tris(8-hydroxyquinoline) aluminum have been made (see Figure) using glancing-angle deposition (GLAD). The films emit circularly polarized light under photoexcitation and consist of highly uniform, self-organized arrays of submicrometer helices. These films combine the molecular diversity of organic chemicals with the complex submicrometer morphologies achievable by GLAD in a single-step process.

    21. Controllable Synthesis and Growth Model of Amorphous Silicon Nanotubes with Periodically Dome-Shaped Interiors (pages 228–234)

      C. Li, Z. T. Liu, C. Gu, X. Xu and Y. Yang

      Article first published online: 11 JAN 2006 | DOI: 10.1002/adma.200500202

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      Amorphous silicon nanotubes with periodically aligned dome-shaped interiors (see Figure) are fabricated by chemical vapor deposition using a gold catalyst. As-grown materials have a length of several tens of micrometers and diameters of 70–100 nm. The inner shape and size of the interiors in the products may be tuned by controlling the silane flow rate, producing structures ranging from nanowires to tubular structures. A growth model based on surface tension is proposed.

    22. Epitaxial Growth of Vertically Aligned and Branched Single-Crystalline Tin-Doped Indium Oxide Nanowire Arrays (pages 234–238)

      Q. Wan, M. Wei, D. Zhi, J. L. MacManus-Driscoll and M. G. Blamire

      Article first published online: 8 DEC 2005 | DOI: 10.1002/adma.200501673

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      Epitaxial growth of well-aligned tin-doped indium oxide (ITO) nanowire arrays on substrates of (100) yttrium-stabilized zirconia with vertical and inclined orientations is reported. Branched ITO nanowires are grown on (100) ITO nanowire backbones by a second step of Au-catalyzed vapor–liquid–solid growth. The Figure shows ITO nanowire branches grown parallel to one another on each side of an ITO nanowire backbone.

    23. Self-Positioning of Polymer Membranes Driven by Thermomechanically Induced Plastic Deformation (pages 238–241)

      D. Haefliger, O. Hansen and A. Boisen

      Article first published online: 14 DEC 2005 | DOI: 10.1002/adma.200501687

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      Stress in polymeric resins is tailored by a thermomechanical process. It allows for controlled self-positioning of membranes in microdevices (see Figure). The process makes specific use of plastic deformation that results from the low viscosity of the polymer. This demonstrates that polymers offer new approaches to microfabrication that cannot be realized for common semiconductor materials without severe difficulties.

    24. Synthesis of Mesoporous Organosilicate Films in Supercritical Carbon Dioxide (pages 241–245)

      R. A. Pai and J. J. Watkins

      Article first published online: 21 DEC 2005 | DOI: 10.1002/adma.200401928

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      Uniform, well-ordered, mesoporous organosilicate films (see Figure) have been synthesized by efficient direct and post-synthesis functionalization methods in supercritical carbon dioxide and characterized using spectroscopic, microscopy, and diffraction techniques. These materials have numerous potential applications, including in sensors, low-k dielectrics, separations, and catalysis.

    25. You have free access to this content
      Self-Assembled Electroluminescent Polymers Derived from Terpyridine-Based Moieties (page 246)

      S.-C. Yu, C.-C. Kwok, W.-K. Chan and C.-M. Che

      Article first published online: 11 JAN 2006 | DOI: 10.1002/adma.200690007

      This article corrects:

      Self-Assembled Electroluminescent Polymers Derived from Terpyridine-Based Moieties1

      Vol. 15, Issue 19, 1643–1647, Article first published online: 7 OCT 2003

    26. Book Review: Functional Fillers for Plastics. By Marino Xanthos (Ed.). (page 248)

      Ian Hamerton

      Article first published online: 11 JAN 2006 | DOI: 10.1002/adma.200500797

    27. Author Index and Subject Index Adv. Mater. 2/2006 (pages 249–250)

      Article first published online: 11 JAN 2006 | DOI: 10.1002/adma.200690008

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