Advanced Materials

Cover image for Advanced Materials

November, 2003

Volume 15, Issue 22

Pages 1875–1954

    1. Advanced Materials Early View Articles (page 1879)

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200390191

    2. Comparison of Electronic Transport Measurements on Organic Molecules (pages 1881–1890)

      A. Salomon, D. Cahen, S. Lindsay, J. Tomfohr, V.B. Engelkes and C.D. Frisbie

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200306091

      A representative selection of room-temperature electronic transport measurements through monolayers or single molecules, saturated and conjugated ones, is reviewed. The currents, measured with a variety of experimental set-ups (see Figure), are also compared. While in several cases different measurements agree remarkably well, in others large differences exist, pointing to areas where more work is needed as this suggests possible novel phenomena.

    3. Fabrication of Crystalline, Highly Ordered Three-Dimensional Silica Monoliths (HOM-n) with Large, Morphological Mesopore Structures (pages 1893–1899)

      S.A. El-Safty and T. Hanaoka

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200305174

      Highly ordered silica monoliths (see Figure) with three-dimensional structures have been fabricated using microemulsion lyotropic liquid crystal phases of Brij 56 as templates under acidic conditions, without loss of the mesoscopic order. The results reveal that the synthetic methodology can effectively control the 3D mesopore morphology. Crystalline, millimeter-sized particles and various geometrical cubic phases have been synthesized.

    4. Production and State-of-the-Art Characterization of Aligned Nanotubes with Homogeneous BCxN (1 ≤ x ≤ 5) Compositions (pages 1899–1903)

      M. Terrones, D. Golberg, N. Grobert, T. Seeger, M. Reyes-Reyes, M. Mayne, R. Kamalakaran, P. Dorozhkin, Z.-C. Dong, H. Terrones, M. Rühle and Y. Bando

      Version of Record online: 16 OCT 2003 | DOI: 10.1002/adma.200305473

      Aligned and hollow BCxN nanotubes with uniformly distributed concentrations of B, C, and N are produced by reacting aligned CNx nanotubes with B2O3 and CuO in a N2 atmosphere at ∼ 1800 °C. It is found that the production of these homogeneous nanotubes is sensitive to the reaction temperature determining the growth kinetics, because segregation of BCN domains may occur at lower or higher temperatures than those used in this study. The Figure shows a molecular model of a coaxial nanocable composed of B, C, and N.

    5. Fabrication of Arrays of Organic Polymeric Thin-Film Transistors Using Self-Aligned Microfluidic Channels (pages 1903–1907)

      M.L. Chabinyc, W.S. Wong, K.E. Paul and R.A. Street

      Version of Record online: 16 OCT 2003 | DOI: 10.1002/adma.200305533

      Arrays of organic thin-film transistors (TFTs; see Figure) were fabricated using self-aligned microfluidic channels. The self-aligned fluidic channels defined the active area of the TFTs and provided pixel-to-pixel isolation. TFTs made with a regioregular poly(thiophene) had field effect mobilities of 0.05 cm2 V–1 s–1 and on/off current ratios of 108.

    6. ZnO Nanoribbon Microcavity Lasers (pages 1907–1911)

      H. Yan, J. Johnson, M. Law, R. He, K. Knutsen, J.R. McKinney, J. Pham, R. Saykally and P. Yang

      Version of Record online: 16 OCT 2003 | DOI: 10.1002/adma.200305490

      ZnO nanoribbons with pseudo-rectangular cross-sections (see Figure) are demonstarted to be excellent microcavities with a high quality factor (∼ 3000). The lasing threshold is shown to be inversely proportional to the length of the ribbon for pumping intensities lower than the saturation region. Analysis of the emission spectra points to the possibility of the existence of both pure axial modes and “bow-tie” cavity modes.

    7. Soft Solution Route to Directionally Grown ZnO Nanorod Arrays on Si Wafer; Room-Temperature Ultraviolet Laser (pages 1911–1914)

      J.-H. Choy, E.-S. Jang, J.-H. Won, J.-H. Chung, D.-J. Jang and Y.-W. Kim

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200305327

      A high-quality ZnO nanorod array (NRA) has been successfully grown on a Si wafer by a wet-chemical process, where the Si wafer was dip-coated with 4 nm sized ZnO nanoparticles as a buffer and seed layer prior to the crystal growth. It is found that the as-prepared ZnO NRA has a threshold power density of ∼ 70 kW cm–2, which is comparable to the lowest one determined for ZnO NRAs on Al2O3 substrates (40 kW cm–2). The ultraviolet lasing efficiency of the ZnO NRAs is thus similar for both substrates.

    8. Spontaneous Organization of Three-Dimensionally Packed Trigonal Selenium Microspheres into Large-Area Nanowire Networks (pages 1914–1918)

      X. Cao, Y. Xie and L. Li

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200305519

      Nanowire networks of trigonal selenium (see Figure) have been prepared over a large area through a spontaneous organization process. This has been realized via the vapor deposition of selenium and subsequent crystallization. The network of selenium nanowires is expected to find applications in nanoscale circuits as well as nanoscale electronic and photon devices.

    9. Polymer-Mediated Alignment of Carbon Nanotubes under High Magnetic Fields (pages 1918–1921)

      H. Garmestani, M.S. Al-Haik, K. Dahmen, R. Tannenbaum, D. Li, S.S. Sablin and M.Y. Hussaini

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200304932

      Alignment of single-walled carbon nanotubes in a bulk epoxy matrix (see Figure) has been achieved through the processing of the composite inside a high magnetic field (15–25 T). The self-organization of the epoxy chains inside the magnetic field mediated the reorientation process of the single-walled carbon nanotubes. The alignment becomes more pronounced as a function of the magnetic field strength.

    10. Simple Solid-Phase Synthesis of Hollow Graphitic Nanoparticles and their Application to Direct Methanol Fuel Cell Electrodes (pages 1922–1925)

      S. Han, Y. Yun, K.-W. Park, Y.-E. Sung and T. Hyeon

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200305697

      Hollow graphitic nanoparticles (see Figure) have been synthesized by the simple heat treatment of a mixture containing a polymeric carbon precursor and a transition metal salt, followed by oxidation. When these particles are used as a catalyst support for a direct methanol fuel cell (DMFC) electrode, the current density and maximum power density of the catalyst supported on these particles is higher than those of a commercial catalyst.

    11. Nanoscale Data Recording on an Organic Monolayer Film (pages 1925–1929)

      H.M. Wu, Y.L. Song, S.X. Du, H.W. Liu, H.J. Gao, L. Jiang and D.B. Zhu

      Version of Record online: 16 OCT 2003 | DOI: 10.1002/adma.200305144

      A “y” formed by nine nanoscale recording marks (see Figure) has been made successfully on an organic thin film by applying voltage pulses between a scanning tunneling microscopy (STM) tip and the highly ordered pyrolytic graphite substrate. The average size of the recorded marks is 1.1 nm in diameter, corresponding to a data storage density of ∼ 1013  bits cm–2. The recording mechanism is discussed according to experiment and calculation.

    12. Compound Core–Shell Polymer Nanofibers by Co-Electrospinning (pages 1929–1932)

      Z. Sun, E. Zussman, A.L. Yarin, J.H. Wendorff and A. Greiner

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200305136

      Co-electrospinning of core–shell polymer nanofibers (see Figure) is introduced. This process can be used for manufacturing of coaxial nanofibers made of pairs of different materials. Non-spinnable materials can be forced into 1D arrangements by co-electrospinning using a spinnable shell polymer. The method results in a novel two-stage approach for fabrication of nanotubes instead of the previously used three-stage process.

    13. Ordered Mesoporous Niobium Oxide Film: A Novel Matrix for Assembling Functional Proteins for Bioelectrochemical Applications (pages 1932–1936)

      X. Xu, B.Z. Tian, J.L. Kong, S. Zhang, B.H. Liu and D.Y. Zhao

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200305424

      The immobilization of cytochrome c (Cyt-c) in ordered mesoporous niobium oxide thin films is investigated for the first time. The direct electrochemical behavior of Cyt-c assembled onto the inorganic matrix (see Figure) and the electrocatalytic properties of this assembly are studied. The results open a new doorway for the application of niobium oxides as bioanalytical devices.

    14. Permeable, Microporous Polymeric Membrane Materials Constructed from Discrete Molecular Squares (pages 1936–1939)

      M.H. Keefe, J.L. O'Donnell, R.C. Bailey, S.T. Nguyen and J.T. Hupp

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200305353

      Microporous polyester membranes (see Figure) have been formed via interfacial polymerization. The reactants were porphyrin-based square assemblies functionalized with phenol groups and bis(acid chloride) linkers. The membranes are free-standing and display size-selective porosity, allowing transport of molecules smaller than the intra-square cavity and displaying blocking behavior with respect to larger molecules.

    15. Planarized Star-Shaped Oligothiophenes as a New Class of Organic Semiconductors for Heterojunction Solar Cells (pages 1939–1943)

      R. de Bettignies, Y. Nicolas, P. Blanchard, E. Levillain, J.-M. Nunzi and J. Roncali

      Version of Record online: 29 SEP 2003 | DOI: 10.1002/adma.200305168

      Although compounds 1 and 2 (see Figure) have comparable conjugation lengths, the characterization of vacuum evaporated thin solid films shows that the star-shaped geometry of compound 1 favors a preferential horizontal orientation of the molecules onto the surface of the substrate, which results in a increase of the efficiency of the corresponding heterojunction solar cells under white-light illumination by a factor of 20.

    16. In-Situ Coating of SBA-15 with MgO: Direct Synthesis of Mesoporous Solid Bases from Strong Acidic Systems (pages 1943–1945)

      Y.L. Wei, Y.M. Wang, J.H. Zhu and Z.Y. Wu

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200305803

      Basic mesoporous materials (see Figure) are synthesized directly from a strong acidic solution for the first time. This is achieved by in-situ coating of SBA-15 with basic MgO by adding acetate salt into the initial mixture of raw materials for synthesis. The synthesis and modification is performed in a one-step procedure. The magnesium acetate not only acts as the precursor of MgO, but also leads to a better order in the mesostructure.

    17. Complex-Surfactant-Assisted Hydrothermal Route to Ferromagnetic Nickel Nanobelts (pages 1946–1948)

      Z. Liu, S. Li, Y. Yang, S. Peng, Z. Hu and Y. Qian

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200305663

      Ferromagnetic metal nanobelts are reported to have been synthesized for the first time in solution by a simple and mild hydrothermal method. The nickel nanobelts (see Figure), which typically had a thickness of ∼15 nm, width of 500–1000 nm, and length of up to 50 μm, showed remarkably enhanced ferromagnetic properties. The method is expected to be transferable to other transition metals.

    18. Tuning of Organic Reversible Switching via Self-Assembled Supramolecular Structures (pages 1949–1952)

      A. Bandyopadhyay and A.J. Pal

      Version of Record online: 20 NOV 2003 | DOI: 10.1002/adma.200305309

      Single-layer devices based on Rose Bengal show large conductance switching between the on and off states (on/off ratio = 104) in the pristine form. Rose Bengal molecules have been incorporated into different water soluble “host” polymer-based supramolecular matrices by layer-by-layer electrostatic self-assembly. Different ionic groups in the supramolecular structures tune the leakage current and the on/off ratio by several orders of magnitude. The switching devices may be used in random-access and read-only memory applications.