Advanced Materials

Cover image for Vol. 17 Issue 15

August, 2005

Volume 17, Issue 15

Pages 1811–1922

    1. Cover Picture: Long, Monomolecular Guanine-Based Nanowires (Adv. Mater. 15/2005)

      A. B. Kotlyar, N. Borovok, T. Molotsky, H. Cohen, E. Shapir and D. Porath

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200590077

      Molecular nanowires for nanoelectronics may be built from guanine (G) tetrad building blocks. Spontaneous assembly of guanine-rich DNA sequences that form tetrads and further arrange into a tetrahelix structure produces long, continuous monomolecular G-wires (see Figure and cover), presumably G4-DNA, composed of single self-folded poly(G) strands of thousands of bases.

    2. Inside Front Cover: Line Defects Embedded in Three-Dimensional Photonic Crystals (Adv. Mater. 15/2005)

      Q. Yan, Z. Zhou, X. S. Zhao and S. J. Chua

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200590078

      Conventional optical photolithography is used to create photoresist patterns on a preformed silica colloidal crystal film. Upon regrowth of the same silica colloidal crystal followed by removal of the photoresist patterns, air–core line defects are successfully introduced into the self-assembled silica colloidal crystal (see Figure and inside cover).

    3. Achieving Individual-Nanotube Dispersion at High Loading in Single-Walled Carbon Nanotube Composites (Adv. Mater. 2005, 8, 980) (page 1820)

      R. A. Graff, J. P. Swanson, P. W. Barone, S. Baik, D. A. Heller and M. S. Strano

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200590075

    4. The Art of SPM: Scanning Probe Microscopy in Materials Science (pages 1821–1833)

      J. Loos

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500701

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      Outstanding examples of applications of scanning probe microscopy (SPM; see Figure) in materials science and the latest developments in techniques that show the full potential of SPM are introduced in this Progress Report. Starting with appealing visualization of matter, other focus points are the investigation of dynamics of processes, determination of properties and functionality, and manipulation of matter at the nanometer length scale.

    5. Enhanced Hole Mobility in Poly-(2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylenevinylene) by Elimination of Nanometer-Sized Domains (pages 1835–1838)

      A. R. Inigo, C. C. Chang, W. Fann, J. D. White, Y.-S. Huang, U.-S. Jeng, H. S. Sheu, K.-Y. Peng and S.-A. Chen

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500331

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      The application of an electric field (Ecast) during solvent vaporization is shown to inhibit the formation of ordered domains in thin films of a poly(phenylenevinylene) derivative, resulting in a homogeneous environment favorable for charge transfer. An order-of-magnitude increase in charge-carrier mobility (see Figure) is achieved by the elimination of these commonly found domains.

    6. A Stable and Highly Active Hybrid Mesoporous Solid Acid Catalyst (pages 1839–1842)

      K. Nakajima, I. Tomita, M. Hara, S. Hayashi, K. Domen and J. N. Kondo

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500426

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      Ethenylene groups within the silicate framework of hybrid mesoporous ethenylene-silica (HME) are successfully modified via a two-step chemical modification process (see Figure) to produce a sulfonic acid-functionalized hybrid mesoporous solid acid catalyst. The material exhibits high activity for various acid-catalyzed reactions and can be used repeatedly without deactivation. The Diels–Alder modification described can be extended to the creation of other functional materials.

    7. Nanostructured TiO2 Films with 2 eV Optical Gap (pages 1842–1846)

      E. Barborini, A. M. Conti, I. Kholmanov, P. Piseri, A. Podestà, P. Milani, C. Cepek, O. Sakho, R. Macovez and M. Sancrotti

      Version of Record online: 16 JUN 2005 | DOI: 10.1002/adma.200401169

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      Nanostructured TiO2 (ns-TiO2) films obtained by supersonic cluster beam deposition possess highly porous, defective structures, and allow efficient incorporation of carbon- containing molecules during thermal treatment. Carbothermal reduction modifies the electronic structure of the ns-TiO2, narrowing the optical gap to 2 eV. This is within the range of visible solar radiation (see Figure), allowing more efficient photoconversion.

    8. The First Example of a Polymer-Crystal–Organic-Dye Composite Material: The Clathrate Phase of Syndiotactic Polystyrene with Azulene (pages 1846–1850)

      Y. Uda, F. Kaneko, N. Tanigaki and T. Kawaguchi

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500396

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      Organic dye molecules have been included in the crystalline regions of syndiotactic polystyrene (sPS) by soaking clathrate or glass films of sPS in an azulene solution containing a plasticizer (see Figure). Highly oriented films, in which the dye molecules are oriented, are easily obtained by applying a similar procedure to an oriented glass sample.

    9. Supported Lyotropic Liquid-Crystal Polymer Membranes: Promising Materials for Molecular-Size-Selective Aqueous Nanofiltration (pages 1850–1853)

      M. Zhou, T. J. Kidd, R. D. Noble and D. L. Gin

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500444

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      The ordered monodisperse ionic channels existing in lyotropic liquid-crystal (LLC) polymer films allow only the passage of water-soluble molecules which are smaller than the ∼ 1.2 nm diameter of the channels. When formed on an ultraporous polysulfone (PSf) support, the films are used effectively as size-selective sieves for water-soluble molecules. These membranes are able to completely reject molecules larger than their pore sizes.

    10. Efficient Infrared-Emitting PbS Quantum Dots Grown on DNA and Stable in Aqueous Solution and Blood Plasma (pages 1854–1857)

      L. Levina, V. Sukhovatkin, S. Musikhin, S. Cauchi, R. Nisman, D. P. Bazett-Jones and E. H. Sargent

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200401197

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      The synthesis of efficient photoluminescent quantum dots via growth on a DNA template is reported for the first time. The nanoparticles emit in the second biological window of 1050–1200 nm with quantum efficiencies of 11.5 ± 1 % in aqueous solution, and are stable for over a week in blood plasma at 37 °C. The Figure shows an energy-filtered TEM image of PbS nanocrystals (Pb: orange; P in DNA: green).

    11. Fabrication of Three-Dimensional Nanostructures Using Reactive Polymer Nanosheets (pages 1857–1861)

      Y. Kado, M. Mitsuishi and T. Miyashita

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500884

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      Reactive “polymer nanosheets” consisting of N-dodecylacrylamide and a photocrosslinkable methacryloyl group in the polymer monolayer have been deposited onto solid substrates by the Langmuir–Blodgett technique. The polymer nanosheets have well-ordered molecular alignment and a controlled thickness on the nanoscale. Multiple photopatterning allows the formation of 3D nanostructures, such as pyramids, tracery patterns, etc. (see Figure), with nanometer thickness precision. The scale bar in the bottom figure represents 5.0 mm.

    12. Nanometer-Sized Gold-Loaded Gelatin/Silica Nanocapsules (pages 1862–1866)

      S. Liu, Z. Zhang and M.-Y. Han

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500124

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      Electrostatic-force-driven self-assembling behavior of gelatin polypeptides has been investigated through the predominantly seeded-aggregation growth of denatured gelatin molecules on citrate-stabilized gold nanoparticles (see Figure). The resulting self-assembled gelatin aggregates have been used as soft templates to prepare nanometer-sized gold-loaded silica/gelatin nanocapsules. This synthetic approach has been extended to various silica-coated biomolecules and provides further insight for creating novel smart bionanostructures.

    13. Active Patterning Using an Addressable Microfluidic Network (pages 1866–1869)

      J.-Y. Shiu and P. Chen

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200401941

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      A simple approach to actively manipulate fluids in two-dimensional microfluidic networks based on the electrocapillary effect is reported. It allows not only patterning of biological solutions and yeast cells in a programmable manner, but also the growth of self-assembled colloidal crystals in the addressable microfluidic networks. The Figure shows a photonic display made by using colloidal particles of different diameters. The inset (scalebar: 200 μm) shows a microchamber filled with 250 nm colloidal crystals.

    14. Directed Motion and Cargo Transport Through Propagation of Polymer-Gel Volume Phase Transitions (pages 1869–1873)

      L. Yeghiazarian, S. Mahajan, C. Montemagno, C. Cohen and U. Wiesner

      Version of Record online: 25 MAY 2005 | DOI: 10.1002/adma.200401205

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      A thermosensitive polymer hydrogel can be used to transport cargo by propagating a volume-phase transition along its length (see Figure; red and blue arrows correspond to localized heating and cooling, respectively). Directional motion with velocities up to 15 μm s–1 for cylinder diameters of approximately 1 mm are recorded. Miniaturization of this device could lead to increased gel speeds and microfluidic and medical applications.

    15. Synthesis of ZnO Nanocrystals with Cone, Hexagonal Cone, and Rod Shapes via Non-Hydrolytic Ester Elimination Sol–Gel Reactions (pages 1873–1877)

      J. Joo, S. G. Kwon, J. H. Yu and T. Hyeon

      Version of Record online: 16 JUN 2005 | DOI: 10.1002/adma.200402109

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      ZnO nanocrystals with various shapes (see Figure) have been synthesized via non-hydrolytic ester elimination sol–gel reactions between zinc acetate and 1,12-dodecanediol. Uniform anisotropic cone-shaped, hexagonal cone-shaped, and rod-shaped ZnO nanocrystals have been synthesized using various surfactants.

    16. Shear-Induced Alignment in Thin Films of Spherical Nanodomains (pages 1878–1881)

      D. E. Angelescu, J. H. Waller, R. A. Register and P. M. Chaikin

      Version of Record online: 25 MAY 2005 | DOI: 10.1002/adma.200401994

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      Large-scale alignment of bilayer block copolymer films by applying in-plane shear is demonstrated. The method eliminates all disclinations and most dislocations from arbitrarily large samples, as evidenced by atomic force microscopy of the microdomain lattice (Figure, left) as well as its Fourier transform (Figure, right). The resulting films can act as ordered nanolithographic templates.

    17. Layer-by-Layer J-Aggregate Thin Films with a Peak Absorption Constant of 106 cm–1 (pages 1881–1886)

      M. S. Bradley, J. R. Tischler and V. Bulović

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500233

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      Layer-by-layer assembly is used to produce thin films of J-aggregates of cyanine dye molecules with an absorption constant of 106 cm–1. The films display high reflection and absorption at resonance (see Figure, ∼50 nm films) and nanoscale features that make them well suited for use in strong-coupling optoelectronic applications, enabling the creation of exciton–polariton optoelectronic devices that operate at room temperature.

    18. Control of Uniaxial Orientation and Fabrication of a Submicrometer-Sized, Oriented Structure in a Photocrosslinkable-Polymer Liquid-Crystalline Film (pages 1886–1890)

      N. Kawatsuki, T. Tachibana and K. Kamada

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200402115

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      Axis-selective two-photon excitation and polarization-preserved triplet energy transfer using a linearly polarized (LP) 800 nm femtosecond pulse laser generates an anisotropic photoreaction in photocrosslinkable-polymer liquid-crystalline films. The molecular orientation is controlled parallel to the polarization of the laser. The tightly focused laser beam generates a submicrometer-oriented structure, as shown in the Figure.

    19. Perylene Derivatives with Large Two-Photon-Absorption Cross-Sections for Application in Optical Limiting and Upconversion Lasing (pages 1890–1893)

      S. L. Oliveira, D. S. Corrêa, L. Misoguti, C. J. L. Constantino, R. F. Aroca, S. C. Zilio and C. R. Mendonça

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500533

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      Perylene tetracarboxylic derivatives (PTCDs) display exceptionally high two-photon absorption (2PA) cross- sections (δ, see Figure). In addition, the 2PA saturation behavior and strong two-photon-pumped fluorescence suggest that PTCD compounds may be attractive candidates for applications in optical limiting and two-photon-pumped upconversion lasing.

    20. Novel Nanopyramid Arrays of Magnetite (pages 1893–1897)

      F. Liu, P. J. Cao, H. R. Zhang, J. F. Tian, C. W. Xiao, C. M. Shen, J. Q. Li and H. J. Gao

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500367

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      Pyramid-like Fe3O4 nanostructures (see Figure) are formed over large areas on α-Fe2O3(0001) substrates using a plasma-sputtering technique. No catalysts or templates are used in the reaction process. This nanostructure resembles Egyptian pyramids, possessing many layers and standing perpendicular to the substrate surface. These structures may have potential applications in constructing nanoscale magnetic and high-density storage devices.

    21. Microstructure and Electromechanical Properties of Carbon Nanotube/ Poly(vinylidene fluoride—trifluoroethylene—chlorofluoroethylene) Composites (pages 1897–1901)

      S. Zhang, N. Zhang, C. Huang, K. Ren and Q. M. Zhang

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500313

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      The ferroelectric relaxor terpolymer (P(VDF-TrFE-CFE) has a dielectric constant above 50 at room temperature and giant longitudinal strain. By adding only 0.5 wt.-% functionalized multiwalled carbon nanotubes, its crystallinity (light blue, see Figure), Young's modulus (green), dielectric constant (dark blue), and electromechanical response (maroon) can be simultaneously improved (see Figure).

    22. Long, Monomolecular Guanine-Based Nanowires (pages 1901–1905)

      A. B. Kotlyar, N. Borovok, T. Molotsky, H. Cohen, E. Shapir and D. Porath

      Version of Record online: 30 JUN 2005 | DOI: 10.1002/adma.200401997

      Thumbnail image of graphical abstract

      Molecular nanowires for nanoelectronics may be built from guanine (G) tetrad building blocks. Spontaneous assembly of guanine-rich DNA sequences that form tetrads and further arrange into a tetrahelix structure produces long, continuous monomolecular G-wires (see Figure and cover), presumably G4-DNA, composed of single self-folded poly(G) strands of thousands of bases.

    23. Synthesis of Metal–Teflon AF Nanocomposites by Solution-Phase Methods (pages 1905–1908)

      D. D. Evanoff Jr., P. Zimmerman and G. Chumanov

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500391

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      Embedding metal and metal-oxide nanoparticles into a Teflon AF matrix using two solution-phase synthesis techniques has been developed and exemplified using silver, gold, palladium, and nickel nanoparticles. The nanocomposite materials (see Figure) exhibit greatly improved chemical stability and can find applications in optoelectronics, catalysis, and as protective coatings.

    24. Tailoring Air Defects in Self-Assembled Photonic Bandgap Crystals (pages 1908–1911)

      Y. Jun, C. A. Leatherdale and D. J. Norris

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500026

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      Introducing structural defects into photonic crystals is a challenge that must be met for many photonic applications. Here, a method is demonstrated to tailor the local structure of silicon inverse opals, prepared from the self-assembly of colloidal microspheres, by combining multiphoton photopolymerization and silsesquioxanes (see Figure).

    25. Building Tunable Planar Defects into Photonic Crystals Using Polyelectrolyte Multilayers (pages 1912–1916)

      N. Tétreault, A. C. Arsenault, A. Mihi, S. Wong, V. Kitaev, I. Manners, H. Miguez and G. A. Ozin

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500029

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      Chemically active polyelectrolyte planar defects (see Figure) are embedded into colloidal photonic crystals using both direct-coating and transfer-printing techniques. These planar defects introduce a transmitting state within the photonic stop band, which is dynamically adjusted with nanometer precision by pressure-controlled selective vapor sorption.

    26. Line Defects Embedded in Three-Dimensional Photonic Crystals (pages 1917–1920)

      Q. Yan, Z. Zhou, X. S. Zhao and S. J. Chua

      Version of Record online: 21 JUL 2005 | DOI: 10.1002/adma.200500047

      Thumbnail image of graphical abstract

      Conventional optical photolithography is used to create photoresist patterns on a preformed silica colloidal crystal film. Upon regrowth of the same silica colloidal crystal followed by removal of the photoresist patterns, air–core line defects are successfully introduced into the self-assembled silica colloidal crystal (see Figure and inside cover).

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