Advanced Materials

Cover image for Advanced Materials

October, 2003

Volume 15, Issue 20

Pages 1665–1776

    1. The Deepening Impact of Materials Science (pages 1675–1676)

      E. Levy

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200302152

      The latest developments in the publication of materials science are examined from the point of view of the top journal in the field in this Editorial. Following the announcement of the 2002 ISI Impact factors, materials science publications are found to be competing capably with the more established research fields of chemistry and physics. Recent highpoints for Advanced Materials are reviewed and upcoming enhancements discussed.

    2. Materials Aspects of Photonic Crystals (pages 1679–1704)

      C. López

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200300386

      Approaches to photonic crystal fabrication with special emphasis on self-assembled structures are reviewed. Examples of current and prospective applications are provided along with, and based on, a general introduction to optical properties of photonic crystals. Certain aspects, such as the synthesis and self-assembly of monodisperse colloidal particles, are highlighted. The Figure shows the Brillouin zone superimposed on a manually assembled colloidal structure.

    3. Tiling Silicalite-1 Nanoslabs into 3D Mosaics (pages 1705–1707)

      S.P.B. Kremer, C.E.A. Kirschhock, A. Aerts, K. Villani, J.A. Martens, O.I. Lebedev and G. Van Tendeloo

      Version of Record online: 25 AUG 2003 | DOI: 10.1002/adma.200305266

      Three new zeotiles, materials combining the advantages of micro- and mesoporous silica materials and capable of withstanding 300 °C, have been designed by tiling Silicalite-1 nanoslabs. The Figure shows the projected silicate framework of one of the zeotiles in yellow, superimposed on a high resolution electron microscopy simulated image. Applications of the zeotiles as molecular sieves and carriers for catalytic functions may be expected.

    4. Barrier-Free Electron–Hole Capture in Polymer Blend Heterojunction Light-Emitting Diodes (pages 1708–1712)

      A.C. Morteani, A.S. Dhoot, J.-S. Kim, C. Silva, N.C. Greenham, C. Murphy, E. Moons, S. Ciná, J.H. Burroughes and R.H. Friend

      Version of Record online: 16 SEP 2003 | DOI: 10.1002/adma.200305618

      A novel barrier-free mechanism for electron–hole capture at heterojunctions between two semiconductor polymers is shown to occur in highly efficient light-emitting diodes (LEDs). Electron–hole capture across the heterojunction forms an exciplex—a localized heterojunction state—and subsequent endothermic energy transfer produces highly emissive excitons. This process only requires low charge densities at the interface, enabling excellent LED performance.

    5. Hydrothermal Synthesis for High-Quality CdTe Nanocrystals (pages 1712–1715)

      H. Zhang, L. Wang, H. Xiong, L. Hu, B. Yang and W. Li

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200305653

      Synthesis of water-soluble CdTe nanocrystals with high photoluminescence quantum yield and narrow fluorescence emission spectra (see Figure) is developed under the conditions of low precursor concentration and moderate temperature of hydrothermal growth. The relatively high temperature accelerates the particle growth rate and enhances the photoluminescence quantum yield.

    6. Monodispersed ZnS Dimers, Trimers, and Tetramers for Lower Symmetry Photonic Crystal Lattices (pages 1715–1719)

      C.M. Liddell and C.J. Summers

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200305283

      Monodispersed ZnS dimers, trimers, and tetramers (see Figure) have been prepared by the decomposition of thioacetamide in the presence of metal salts. The hierarchically structured aggregates expand the menu of complex colloid bases available as building blocks for photonic crystal structures. Such ordered assemblies of non-spherical colloids are predicted to promote large, stable photonic bandgaps.

    7. Ferromagnetic Spots in Graphite Produced by Proton Irradiation (pages 1719–1722)

      K.-h. Han, D. Spemann, P. Esquinazi, R. Höhne, V. Riede and T. Butz

      Version of Record online: 10 SEP 2003 | DOI: 10.1002/adma.200305194

      A proton microbeam produces ferromagnetic spots on a highly oriented graphite surface. The Figure shows the topography and the magnetic force microscopy (MFM) images obtained after irradiating the surface with a beam size of 1 μm × 1 μm and a dose of 0.098 nC μm–2. The strength of the magnetic signal is only a factor of ∼ 10 smaller than that obtained on Fe particles.

    8. Preparation of Photosensitive Dye Aggregates and Fluorescent Nanocrystals in Microreaction Containers (pages 1722–1726)

      C.S. Peyratout, H. Möhwald and L. Dähne

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200304999

      Functionalization of the interior of hollow microcapsules with polyelectrolytes allows the preparation of supramolecular dye assemblies inside the capsules (see Figure). The dye J-aggregates can be transformed into dye nanocrystals by diffusion of hydrophobic counterions in the capsules, resulting in strong changes of the luminescence behavior.

    9. A Low Threshold Polymer Laser Based on Metallic Nanoparticle Gratings (pages 1726–1729)

      J. Stehr, J. Crewett, F. Schindler, R. Sperling, G. von Plessen, U. Lemmer, J.M. Lupton, T.A. Klar, J. Feldmann, A.W. Holleitner, M. Forster and U. Scherf

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200305221

      Optically pumped lasing is demonstrated in a device consisting of a conjugated polymer on top of a 2D distributed feedback template comprising gold nanodiscs on indium tin oxide (see Figure). Although the nanodiscs are potential dissipative energy absorbers only a marginal increase in lasing threshold is found when compared to conventional dielectric distributed feedback resonators. The inset shows a photograph of the far-field emission above threshold.

    10. A Novel Approach for Preparation of Thermoresponsive Polymer Magnetic Microspheres with Core–Shell Structure (pages 1729–1732)

      Y.H. Deng, W.L. Yang, C.C. Wang and S.K. Fu

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200305459

      Dual-responsive polymer microspheres with well-defined core–shell structure (see Figure) have been prepared via a template polymerization process. The resulting microspheres consist of a silica-coated magnetite core and a cross-linked poly(N-isopropylacrylamide) shell, which enable them to exhibit both magnetic response and thermoresponse.

    11. Aerosol-Assisted Formation of Mesostructured Thin Films (pages 1733–1736)

      Y. Lu, B.F. McCaughey, D. Wang, J.E. Hampsey, N. Doke, Z. Yang and C.J. Brinker

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200305331

      A new aerosol-assisted surfactant self-assembly approach has been developed for large-scale mesostructured silica thin film fabrication. The formation mechanism involves coalescence of semisolid surfactant–silica mesostructured particles on substrates (see Figure) and subsequent reassembly of the mesostructures to adapt the morphology transformation from spherical to planar shape.

    12. Anisotropy in the Mobility and Photogeneration of Charge Carriers in Thin Films of Discotic Hexabenzocoronenes, Columnarly Self-Assembled on Friction-Deposited Poly(tetrafluoroethylene) (pages 1736–1740)

      J. Piris, M.G. Debije, N. Stutzmann, A.M. van de Craats, M.D. Watson, K. Müllen and J.M. Warman

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200305358

      Discotic derivatives of hexabenzocoronene macroscopically self-align on friction-deposited poly(tetrafluoroethylene) (see Figure for polarization microscopy image of a partially coated sample). Such films display highly anisotropic photoconductivity with charge transport along the columnar director favored by a factor of at least 20. The anisotropy in the optical absorption depends on the tilt angle of the aromatic core in the columns.

    13. Direct Synthesis of Se@CdSe Nanocables and CdSe Nanotubes by Reacting Cadmium Salts with Se Nanowires (pages 1740–1743)

      X. Jiang, B. Mayers, T. Herricks and Y. Xia

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200305737

      Se@CdSe nanocables and CdSe nanotubes with diameters of around 50 nm (see Figure) can be directly synthesized via a template- engaged approach in aqueous solution. The walls of these nanotubes are composed of CdSe nanoparticles 5–10 nm in size. It is believed this approach can be potentially extended to process many other chalcogenides into tubular nanostructures.

    14. Polymer–Clay Nanocomposite Foams Prepared Using Carbon Dioxide (pages 1743–1747)

      C. Zeng, X. Han, L.J. Lee, K.W. Koelling and D.L. Tomasko

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200305065

      Poly(methylmethacrylate) and polystyrene–clay nanocomposites have been synthesized and exfoliated clay dispersion has been achieved (see Figure). Nanocomposite foams have been prepared using CO2 as the foaming agent. Orders of magnitude increase in nucleation efficiency was accomplished by manipulation of clay dispersion and polymer–clay–CO2 interaction.

    15. Surfactant-Assisted Growth of Novel PbS Dendritic Nanostructures via Facile Hydrothermal Process (pages 1747–1750)

      D. Kuang, A. Xu, Y. Fang, H. Liu, C. Frommen and D. Fenske

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200304623

      3D PbS dendritic nanostructures (see Figure) have been fabricated by a facile hydrothermal method in the presence of N-cetyl-N,N,N-trimethyl-ammonium bromide (CTAB). Both CTAB and thiourea play important roles in the formation of well-defined PbS dendrites. X-ray diffraction, electron diffraction, and high-resolution transmission electron microscopy results show that the PbS nanostructure is a 3D dendrite of a single crystal.

    16. A Novel Hierarchical Nanozeolite Composite as Sorbent for Protein Separation in Immobilized Metal-Ion Affinity Chromatography (pages 1751–1753)

      F. Xu, Y. Wang, X. Wang, Y. Zhang, Y. Tang and P. Yang

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200305287

      A new hierarchical porous zeolite–diatomite composite (see Figure inset) of excellent mechanical and chemical stability, after immobilization of Co2+ by an ion-exchange process, was utilized as a packing sorbent for the separation of peptides and proteins containing histidine clusters. The Figure shows the chromatographic profile for two peptides separated using immobilized metal-ion affinity chromatography.

    17. Laser Ablation Synthesis and Electron Transport Studies of Tin Oxide Nanowires (pages 1754–1757)

      Z. Liu, D. Zhang, S. Han, C. Li, T. Tang, W. Jin, X. Liu, B. Lei and C. Zhou

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200305439

      The synthesis of high-quality SnO2 nanowires by a laser ablation method is demonstrated. Single nanowire transistors have been fabricated, and their electronic transport and photoconduction properties have been studied. The Figure shows a schematic of the experimental setup for polarized UV detection.

    18. Exfoliation of Single-Walled Carbon Nanotubes by Electrochemical Treatment in a Nitric Acid (pages 1757–1760)

      H.J. Kim, K.K. Jeon, K.H. An, C. Kim, J.G. Heo, S.C. Lim, D.J. Bae and Y.H. Lee

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200304942

      Single-walled carbon nanotube (SWNT) bundles have been dispersed by an electrolysis method. Intercalation of bundles by NO3 widens locally the inter-tube spacing. Bundles are nanodispersed into individual nanotubes after deintercalation (see Figure). This method could be used to fabricate electrodes for high-capacity batteries and supercapacitors.

    19. Sol–Gel Mediated Synthesis of Fe2O3 Nanorods (pages 1761–1764)

      K. Woo, H.J. Lee, J.-P. Ahn and Y.S. Park

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200305561

      Fe2O3 nanorods with controlled phase depending on the conditions have been synthesized via a sol–gel-mediated route. The synthesis was performed using an easy and cheap method whereby, starting with an Fe3+ salt, a sol–gel reaction in reverse micelles is followed by crystallization by reflux (see Figure for a schematic of the synthesis). A mechanism is proposed for the nanorod growth.

    20. Can Carbon Nanotubes be Considered Useful Tools for Biological Applications? (pages 1765–1768)

      A. Bianco and M. Prato

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200301646

      Carbon nanotubes (CNTs) can be functionalized using the versatile 1,3-dipolar cycloaddition of azomethine ylides. This methods allows one to obtain a highly soluble material that can be further modified by covalently linking bioactive peptides. Immobilization of peptides to the external walls of CNTs (see Figure) paves the way for their potential application in medicinal chemistry.

    21. Author Index Adv. Mater. 20/2003 (page 1775)

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200390183

    22. Subject Index Adv. Mater. 20/2003 (page 1776)

      Version of Record online: 23 OCT 2003 | DOI: 10.1002/adma.200390184