Advanced Materials

Cover image for Advanced Materials

April, 2004

Volume 16, Issue 7

Pages 571–658

    1. Contents: Adv. Mater. 7/2004 (pages 571–578)

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200490021

    2. Semiconductive Polymer Blends: Correlating Structure with Transport Properties at the Nanoscale (Adv. Mater. 2004, 16, 385.) (page 579)

      C. Ionescu-Zanetti, A. Mechler, S. A. Carter and R. Lal

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200490022

    3. Physical and Chemical Nanostructure Transfer in Polymer Spin-Transfer Printing (pages 581–584)

      Y. S. Kim, S. J. Baek and P. T. Hammond

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306231

      An alternative lithographic technique that creates complex nanostructures using an elastomer stamp, a spin-coating step, and a polyelectrolyte as the adhesion promotion layer is presented (see Figure). The method does not require high pressure or temperatures, and can take advantage of the elastomer stamp to reproducibly replicate chemical and physical patterns on the nanometer length scale.

    4. Soft Lithographic Patterning of Hyaluronic Acid on Hydrophilic Substrates Using Molding and Printing (pages 584–588)

      K. Y. Suh, A. Khademhosseini, J. M. Yang, G. Eng and R. Langer

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306180

      Hyaluronic acid (HA) was patterned using two soft lithographic methods on various substrates including glass, silicon dioxides, poly(hydroxyethyl methacrylate) [poly(HEMA)], polystyrene cell culture dishes, and biodegradable polylactic glycolic acid (PLGA), with no or minor chemical modification. Results indicate that HA could be used as a general platform on hydrophilic substrates for cell and protein patterning (see Figure).

    5. Anisotropic Properties of Conducting Polymers Prepared by Liquid Crystal Templating (pages 589–592)

      J. F. Hulvat and S. I. Stupp

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306263

      Anisotropic films of poly(3,4-ethyldioxythiophene) (PEDOT) have been prepared by polymerization in an aqueous, self-organized liquid crystalline template. The cylindrical, hydrophobic cores of the hexagonal template direct electropolymerization, producing films with anisotropic optical absorption and conductivity (see Figure).

    6. A Poly(vinyl alcohol)/Carbon-Black Composite Film: A Platform for Biological Macromolecule Incorporation (pages 592–596)

      L. L. Brott, S. M. Rozenzhak, R. R. Naik, S. R. Davidson, R. E. Perrin and M. O. Stone

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200305641

      A biomimetic infrared sensor has been fabricated that takes advantage of the unique thermosensing properties of the TlpA protein of Salmonella. By integrating this protein into a matrix of poly(vinyl alcohol) doped with conductive carbon black and plasticizer, a simple and reliable thermally sensitive array can be fabricated (see Figure). This array can track the heat from a flashlight over 6 m away or distinguish between three independent heat sources.

    7. Large-Area Electric-Field-Induced Colloidal Single Crystals for Photonic Applications (pages 596–600)

      A. Yethiraj, J. H. J. Thijssen, A. Wouterse and A. van Blaaderen

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306192

      A technique to grow millimeter-scale (3 mm × 0.5 mm) electric-field-induced colloidal single crystals and a polymerization process that immobilizes them, allowing drying and reversal of the refractive-index contrast, is presented. The Figure shows a 2D diffraction pattern under white-light illumination from a crystal; the hexagonal symmetry pattern is characteristic of a close-packed lattice.

    8. Submicrometer Scroll/Tubular Lamellar Crystals of Nylon 6,6 (pages 600–605)

      W. Cai, C. Y. Li, L. Li, B. Lotz, M. Keating and D. Marks

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200305634

      Nylon 6,6 single-crystal scrolls and tubes (see Figure) have been created through self-seeding solution crystallization. The tube diameter is ∼ 350 nm with a ∼ 10 nm thin wall. The tubular/scroll single crystal form is presumably due to the asymmetric folding of Nylon 6,6, which can be turned on and off by controlling the self-seeding temperature.

    9. Electrospray-Assisted Fabrication of Uniform Photonic Balls (pages 605–609)

      J. H. Moon, G.-R. Yi, S.-M. Yang, D. J. Pine and S. B. Park

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200305446

      Photonic balls have been fabricated (see Figure) by field-enhanced electrospray of an aqueous colloidal suspension. The polystyrene (PS) beads inside the suspension droplets self-organize into opaline balls while the solvent evaporates. The opaline balls are used as templates for inverse opaline photonic balls, and both types exhibit varying reflection colors depending on the diameter of the beads and the reflective index contrast.

    10. Carbon Nanotubes with Graphitic Wings (pages 610–613)

      S. Trasobares, C. P. Ewels, J. Birrell, O. Stephan, B. Q. Wei, J. A. Carlisle, D. Miller, P. Keblinski and P. M. Ajayan

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306459

      Graphitic platelets (wings) on carbon nanotubes are produced using a new two-step chemical vapor deposition method (see Figure and inside cover). Chemical attack during the process, aided by curvature-induced strain, rips open the outer nanotube walls and produces an irregular and corrugated surface. The new morphology, which presents a highly modulated and active nanotube surface, could facilitate posterior functionalization or direct composite fabrication.

    11. Cooperativity in a Chemomechanical Polymer: A Chemically Induced Macroscopic Logic Gate (pages 613–615)

      H.-J. Schneider, L. Tianjun, N. Lomadze and B. Palm

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306249

      Incorporating supramolecular binding sites into flexible polymers allows the translation of selective molecular recognition into large macroscopic motions. The macroscopic dimension changes depend dramatically on the presence of two effector compounds in the surrounding medium, with either negative or with positive cooperativity. A macroscopic dimension change occurs if two different effectors are present within a narrow concentration range, thus providing, for the first time, chemically induced macroscopic XOR or AND logic gates.

    12. White Electrophosphorescence from Semiconducting Polymer Blends (pages 615–619)

      X. Gong, W. Ma, J. C. Ostrowski, G. C. Bazan, D. Moses and A. J. Heeger

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306230

      White emission from polymer light-emitting diodes (PLEDs) is demonstrated using semiconducting polymers blended with organometallic emitters and spin-cast from solution. Because a single semiconducting polymer was used as the common host for red, green, and blue emission, the color coordinates, color temperatures, and color rendering indices of the white emission are insensitive to the brightness, applied voltage, and applied current density. The PLEDs have luminous efficiency of 4.3 cd A–1 and luminance of 223 cd m–2 at current density of 5.2 mA cm–2 (V = 14 V); at 17 V, L = 1.2 × 104 cd m–2.

    13. Self-Organized Complex Patterning: Langmuir–Blodgett Lithography (pages 619–624)

      S. Lenhert, L. Zhang, J. Mueller, H. P. Wiesmann, G. Erker, H. Fuchs and L. Chi

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306203

      Self-patterning monolayer films prepared by the Langmuir–Blodgett technique have been used as resists for anisotropic chemical etching of Si 〈100〉. The resulting topographies are transferred onto polymer surfaces to guide the growth of biological cells. This method allows rapid and simple nanolithography of complex nanopatterns over large areas.

    14. Efficient Organic Electrophosphorescent White-Light-Emitting Device with a Triple Doped Emissive Layer (pages 624–628)

      B. W. D'Andrade, R. J. Holmes and S. R. Forrest

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306670

      An organic electrophosphorescent white-light-emitting device (see Figure) containing green, red, and blue emitters doped into a 9 nm thick wide-bandgap material is shown to attain a maximum forward viewing power efficiency of (26±3) lm W–1. The high power efficiency is attributed to the efficient confinement of excitons and charge within the emissive layer, a thin emissive layer, and highly efficient blue electrophosphorescent dopant.

    15. Nanoscale Surface Patterning of Enzyme-Catalyzed Polymeric Conducting Wires (pages 628–633)

      P. Xu and D. L. Kaplan

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306367

      Nanoscale surface patterning of 4-aminothiophenol was achieved by dip-pen nanolithography via horseradish-peroxidase-catalyzed polymerization (see Figure) at ambient conditions to form conducting wires.

    16. All-Organic Permanent Memory Transistor Using an Amorphous, Spin-Cast Ferroelectric-like Gate Insulator (pages 633–636)

      R. Schroeder, L. A. Majewski and M. Grell

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306187

      An all-organic memory transistor (“FerrOFET”) with a solution- deposited ferroelectric-like nylon gate insulator is demonstrated. Cheaper and easier to build than inorganic ferroelectric transistors, yet with comparable performance and compatible with flexible substrates, this device is suitable for most information storage organic electronics applications. The Figure shows the memory function of the FerrOFET as hysteresis in the transfer characteristics.

    17. Reversible Photoregulation of the Electrical Conductivity of Spiropyran-Doped Polyaniline for Information Recording and Nondestructive Processing (pages 636–640)

      X. Guo, D. Zhang, G. Yu, M. Wan, J. Li, Y. Liu and D. Zhu

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200305792

      Reversibly photoswitchable proton transfer processes can occur between a three-state molecular switch based on spiropyran (SP) and the “salt form” of polyaniline (see Figure), both in solution and in the solid state. As a result, the electrical conductivity of the thin-film of SP-doped polyaniline can be photoregulated.

    18. Carbon Nanotube Film Sensors (pages 640–643)

      Z. Li, P. Dharap, S. Nagarajaiah, E. V. Barrera and J. D. Kim

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306310

      A carbon nanotube film (see Figure) can be used as a strain sensor at the macroscale, due to the dependence of the electrical properties of single-walled carbon nanotubes on mechanical deformation at the nanoscale.

    19. Reversible Diastereoselective Photocyclization of Diarylethenes in a Bulk Amorphous State (pages 643–645)

      T. Yamaguchi, K. Nomiyama, M. Isayama and M. Irie

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200305815

      Diarylethene derivatives with two chiral substituents (see Figure) undergo reversible diastereoselective photocyclization reactions in a bulk amorphous state. An enrichment of one of the diastereomers (25% d.e.) has been found to exist below the glass transition temperature. The diastereoselection clearly indicates that short distance regularity exists in the glassy state.

    20. Supercritical Fluid–Liquid–Solid Synthesis of Gallium Arsenide Nanowires Seeded by Alkanethiol-Stabilized Gold Nanocrystals (pages 646–649)

      F. M. Davidson III, A. D. Schricker, R. J. Wiacek and B. A. Korgel

      Article first published online: 18 FEB 2004 | DOI: 10.1002/adma.200306284

      A new GaAs nanowire synthesis method is employed to produce a high yield of single-crystalline wires. Reaction at 500 °C in supercritical hexane using gold seed particles results in wires that average 25 nm in diameter and tens of micrometers in length. The wires lend themselves to device fabrication (see Figure) allowing for electronic characterization.

    21. Ultra-Thin Trigonal Selenium Nanoribbons Developed from Series-Wound Beads (pages 649–653)

      X. B. Cao, Y. Xie, S. Y. Zhang and F. Q. Li

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306317

      Ultra-thin t-Se nanoribbons are produced simply and conveniently via a vapor–liquid–solid (VLS) mechanism. The nanoribbons are highly crystalline and grow preferentially along the c-axis, with an average thickness of 15 nm (see Figure) and lengths up to several hundreds of micrometers. The intermediates in the formation are series-wound beads, which develop into 1D nanostructures confined by the anisotropic crystal structure of t-Se during cooling.

    22. Controlled Fluorescence Bursts from Conjugated Polymers Induced by Triplet Quenching (pages 653–657)

      F. Schindler, J. M. Lupton, J. Feldmann and U. Scherf

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200306291

      Dramatic fluorescence bursts (see Figure and cover) from conjugated polymers are observed upon exposure to air. The burst occurs prior to photo-oxidation and is imaged in single molecules of a ladder-type polymer, but is also found in bulk films. Triplet shelving is identified as an important mechanism limiting the fluorescence yield of conjugated polymers due to both a reduction in photon cycling rates and singlet–triplet quenching in the multichromophoric system.

    23. Author Index and Subject Index Adv. Mater. 7/2004 (page 658)

      Article first published online: 20 APR 2004 | DOI: 10.1002/adma.200490023

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