Advanced Materials

Cover image for Vol. 15 Issue 12

June, 2003

Volume 15, Issue 12

Pages 951–1030

    1. Contents: Adv. Mater. 12/2003 (pages 951–955)

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200390148

    2. Taking Advantage of Disorder: Amorphous Calcium Carbonate and Its Roles in Biomineralization (pages 959–970)

      L. Addadi, S. Raz and S. Weiner

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200300381

      Amorphous calcium carbonate is a metastable phase that is formed by organisms (e.g., the cystolith from Ficus microcarpa, Figure), and can be produced synthetically. In both cases it can be stabilized permanently or transformed into a more stable crystalline form. Differences in stability are reflected in variations of molecular structure. Here, structural variations and possible mechanisms of formation and stabilization of this unique form of calcium carbonate are reviewed.

    3. Single-Step Self-Organization of Ordered Macroporous Nanocrystal Thin Films (pages 971–974)

      P.S. Shah, M.B. Sigman Jr., C.A. Stowell, K.T. Lim, K.P. Johnston and B.A. Korgel

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304903

      Spatially organized macroporous thin films made of close-packed nanocrystals (see Figure) can be formed using a single-step dispersion evaporation technique. Water condensation is induced, in which droplet coalescence is prevented by interfacially active nanocrystals, allowing close-packed arrays of monodisperse water droplets to form. The hydrophobic nanocrystals then mold themselves around the water droplet template, leading to highly ordered porous nanocrystal films.

    4. Electro-Tunable Liquid-Crystal Laser (pages 974–977)

      M. Ozaki, M. Kasano, T. Kitasho, D. Ganzke, W. Haase and K. Yoshino

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304448

      Lasing that is color-tunable via application of an electric field has been demonstrated at the edge of the 1D photonic band of a dye-doped chiral smectic liquid crystal with a periodic spiral structure. The lasing wavelength, which can be shifted by 40 nm using a relatively low electric field, is tuned by the electric field adjusting the periodicity of the helical structure (see Figure).

    5. Facile Fabrication of Photochromic Dye–Conducting Polymer Core–Shell Nanomaterials and Their Photoluminescence (pages 977–980)

      J. Jang and J.H. Oh

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304819

      Photochromic dye (pyrene)–conducting polymer (polypyrrole) core–shell nanomaterials were fabricated using microemulsion micelles as nanoreactors. The adsorption state of pyrene was tunable over a wide range with a small pyrene loading because of the phase separation and the packing constraints of the pyrene crystal. This methodology provides a facile way to control the emission of organic dyes, and also presents a new concept of nanohybrids for electronic devices.

    6. Multifunctional Sodium Lanthanide Silicates: From Blue Emitters and Infrared S-Band Amplifiers to X-Ray Phosphors (pages 980–985)

      D. Ananias, A. Ferreira, L.D. Carlos and J. Rocha

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304474

      A judicious choice of the lanthanide cation and its content in the Na3(Y1–aMa)Si3O9 (M=Tm3+, Tb3+; a = 0–1) system allows the optical properties to be tuned over a very wide range. The materials have the same framework structure and encompass thulium-based blue- and infrared-emitters and terbium-based X-ray phosphors (see spectra in Figure). The emission can be controlled in some infrared regions by varying the Y3+/Tm3+ molar ratio.

    7. Patterned Alignment of Liquid Crystals on Selectively Thiol-Functionalized Photo-Orientation Layers (pages 985–988)

      H.T.A. Wilderbeek, J.-P. Teunissen, C.W.M. Bastiaansen and D.J. Broer

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304759

      The patterned alignment of liquid crystals is demonstrated on selectively thiol-functionalized photo-orientation layers (see cover). Deposited thiols are covalently bound to unsaturated linkages in linearly photo-polarizable materials, facilitating the simple and versatile combination of a bi-directionally planar and a homeotropic alignment of liquid crystals within a single substrate (e.g., in Figure). This opens new possibilities for the design, manufacture, and application of existing and novel display concepts.

    8. High-Performance Polymer Solar Cells of an Alternating Polyfluorene Copolymer and a Fullerene Derivative (pages 988–991)

      M. Svensson, F. Zhang, S.C. Veenstra, W.J.H. Verhees, J.C. Hummelen, J.M. Kroon, O. Inganäs and M.R. Andersson

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304150

      Solar cells prepared using the alternating copolymer shown in the Figure blended with a C60 derivative (PCBM) are demonstrated to have a high performance, with a power conversion efficiency of 2.2 % under simulated solar light. The molecular weight of the polymer is low due to limited solubility, and films of the polymer exhibit red-shifted absorption.

    9. Formation of Polarization Gratings and Surface Relief Gratings in Photocrosslinkable Polymer Liquid Crystals by Polarization Holography (pages 991–994)

      N. Kawatsuki, T. Hasegawa, H. Ono and T. Tamoto

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304988

      Polarization holography in photocrosslinkable polymer liquid crystals films is described. By adjusting the polarization modes of the interference light beams, both “pure” polarization and surface relief gratings can be prepared. The Figure shows an optically polarized microscope image of a grating fabricated using orthogonal linear beams (arrows show direction of polarizers).

    10. Three-Dimensional Ceramic Microcomponents Made Using Microstereolithography (pages 994–997)

      C. Provin, S. Monneret, H. Le Gall and S. Corbel

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304916

      The combination of a microstereolithography process and a high-load ceramic suspension is used to produce complex three-dimensional alumina microparts. The object (see Figure) produced is designed for microfluidic applications, but the versatility of the microstereolithography technique is generally applicable to the preparation of microcomponents for numerous applications.

    11. Detection of CO and O2 Using Tin Oxide Nanowire Sensors (pages 997–1000)

      A. Kolmakov, Y. Zhang, G. Cheng and M. Moskovits

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304889

      Highly uniform SnO2 nanowires, with bulk electronic properties directed by their surface chemistry, have been produced by isolating and oxidizing tin nanowires selected from a template-synthesized array. The nanowires act as sensitive, fast, stable, and reproducible gas sensors that can be easily integrated into a multi-component array (see Figure).

    12. Synthesis of Gallium-Filled Gallium Oxide–Zinc Oxide Composite Coaxial Nanotubes (pages 1000–1003)

      J.Q. Hu, Y. Bando and Z.W. Liu

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304825

      Ga2O3–ZnO composite coaxial nanotubes have been fabricated via a simple process combining thermal reaction and physical evaporation. The resulting nanotubes are either empty or partially or completely filled with Ga (see Figure), forming Ga (core)–Ga2O3 (interlayer)–ZnO (outer shell) three-layer coaxial nanocables. The photoluminescence of the nanostructures is investigated and a mechanism for their formation is proposed.

    13. High-Density 40 nm Diameter Sb-Rich Bi2–xSbxTe3 Nanowire Arrays (pages 1003–1006)

      M. Martín-González, A.L. Prieto, R. Gronsky, T. Sands and A.M. Stacy

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304781

      Arrays of 40 nm Bi2–xSbxTe3 nanowires (x ∼ 0.7, density ∼ 5 × 1010 cm–2) have been synthesized. The individual wires are crystalline, relatively homogeneous, and highly textured in a 〈110〉 direction after thermal treatment. Wires containing Sb exhibit incomplete wetting of the alumina templates in which they are grown (see Figure). The composition, crystallinity, and morphology of the nanowires can also be manipulated.

    14. Formidable Increase in the Superplasticity of Ceramics in the Presence of an Electric Field (pages 1006–1009)

      Z. Shen, H. Peng and M. Nygren

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304863

      The ductility of silicon nitride-based ceramics is dramatically enhanced in the presence of a pulsed electric field/current that induces movement of the charged species present in the grain boundary glassy/liquid phase, and thereby promotes grain sliding along the grain boundaries. The Figure shows an α-sialon component before (right) and after (left) deformation.

    15. Metal Transfer Printing and Its Application in Organic Field-Effect Transistor Fabrication (pages 1009–1012)

      Z. Wang, J. Yuan, J. Zhang, R. Xing, D. Yan and Y. Han

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304846

      The fabrication of multilayer microstructures, for example for organic field-effect transistors, using metal transfer printing (MTP) is demonstrated. The Figure shows a two-layer gold structure produced by MTP. Since MTP is a purely additive technique, in which mechanical adhesion acts as the patterning driving force, it is considered an attractive approach to reel-to-reel processing.

    16. Improved Hydrogen Storage Properties of Ti-Doped Sodium Alanate Using Titanium Nanoparticles as Doping Agents (pages 1012–1015)

      B. Bogdanović, M. Felderhoff, S. Kaskel, A. Pommerin, K. Schlichte and F. Schüth

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304711

      By using nanosized doping agents, the properties of Ti-catalyzed NaAlH4 storage systems are considerably improved. Hydrogenation–dehydrogenation cyclic testing shows that with nanosized TiN dopants, storage capacities of 5 wt.-% H2 could be achieved. Doping with nanosized Ti brought hydrogenation times close to those required for practical applications, combined with high capacity (4.5 wt.-% H2, see Figure).

    17. Electrochemical Growth of Dendritic Conducting Polymer Networks (pages 1015–1019)

      A. Baba and W. Knoll

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304728

      A simple approach to fabricate dendritic conducting polymer networks has been developed by means of electropolymerization of pyrrole onto a micropatterned self-assembled monolayer. This polypyrrole network was obtained by a combination of microcontact printing (μCP) of an octadecanethiol self-assembled monolayer (ODT-SAM) pattern on gold and subsequent electropolymerization of pyrrole.

    18. Ruthenium Oxide Nanotube Arrays Fabricated by Atomic Layer Deposition Using a Carbon Nanotube Template (pages 1019–1022)

      Y.-S. Min, E.J. Bae, K.S. Jeong, Y.J. Cho, J.-H. Lee, W.B. Choi and G.-S. Park

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304452

      A chemical vapor deposition-related method (atomic layer deposition) is reported to have been successfully used to fabricate an inorganic nanotube array at low temperatures (below 400 °C) for the first time. The Figure shows a scanning electron microscopy image of a ruthenium oxide nanotube array on top of an anodic aluminum oxide (AAO) matrix on a silicon wafer after removal of the carbon nanotube template.

    19. Low-Temperature Fabrication of Highly Crystalline SnO2 Nanorods (pages 1022–1025)

      D.-F. Zhang, L.-D. Sun, J.-L. Yin and C.-H. Yan

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304899

      Uniform SnO2 nanorods with diameters of ∼ 8–15 nm and lengths of ∼ 150–200 nm have been successfully fabricated by a one-step reverse micro-mediated hydrothermal process. X-ray diffraction and transmission electron microscopy (TEM) indicate that the as-prepared SnO2 nanorods are of high crystallinity. The Figure shows a TEM image of SnO2 nanorods synthesized at 200 °C for 18 h.

    20. Site-Selective Growth of Colloidal Crystals with Photonic Properties on Chemically Patterned Surfaces (pages 1025–1028)

      C.-A. Fustin, G. Glasser, H.W. Spiess and U. Jonas

      Version of Record online: 16 JUN 2003 | DOI: 10.1002/adma.200304792

      Microscopically structured colloidal crystals have been self-assembled using capillary forces onto chemically patterned surfaces. It is shown that the wetting meniscus on substrates patterned with hydrophobic and hydrophilic regions acts in this process as self-removing crystallization template (see Figure). By this method, closed-packed structures with a well-defined and intense bandgap in the visible range are obtained.