Advanced Materials

Cover image for Vol. 14 Issue 6

March, 2002

Volume 14, Issue 6

Pages 393–463

    1. Contents (pages 393–396)

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<393::AID-ADMA393>3.0.CO;2-C

    2. AFM Contents (pages 398–400)

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<398::AID-ADMA398>3.0.CO;2-T

    3. Digital Processing and Communication with Molecular Switches (pages 401–414)

      F.M. Raymo

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<401::AID-ADMA401>3.0.CO;2-F

      Molecular switches based on chemical, electrical, or optical stimulations are a hot topic as they can provide the future for faster computers and internet applications. Basic logic operations of AND, NOT, and OR gates have been reproduced relying on simple molecular switches (see Figure). The fabrication of nanoelectronic circuits and all-optical networks from molecular components can be envisaged.

    4. Protein Engineering of a Viral Cage for Constrained Nanomaterials Synthesis (pages 415–418)

      T. Douglas, E. Strable, D. Willits, A. Aitouchen, M. Libera and M. Young

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<415::AID-ADMA415>3.0.CO;2-W

      Cage architectures based on the cowpea chlorotic mottle virus (see Figure) have been employed to achieve a synthetic mimic of the iron storage protein ferritin. The electrostatic nature of the inner protein surface could be changed by up to 3240 units of charge, while still maintaining a stable cage structure. The spatial isolation within the protein cage prevents bulk aggregation of the mineral particles and results in a stable, mono-disperse colloid.

    5. Low-Temperature Fabrication of Light-Emitting Zinc Oxide Micropatterns Using Self-Assembled Monolayers (pages 418–421)

      N. Saito, H. Haneda, T. Sekiguchi, N. Ohashi, I. Sakaguchi and K. Koumoto

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<418::AID-ADMA418>3.0.CO;2-K

      ZnO micropatterning under very mild conditions is presented. Photolysis (using a mask) of Si–C bonds in a self-assembled phenylsilane layer yields a patterned phenyl/hydroxy surface. ZnO is selectively deposited at 55 °C on the phenyl domains by electroless deposition using a Pd catalyst adhered to the surface. The viability of the ZnO pattern as a phosphor is illustrated by the visible light cathodoluminescence image shown in the Figure and on the cover.

    6. Mechanism of the Formation of Self-Organized Microstructures in Soft Functional Materials (pages 421–426)

      X.Y. Liu and P.D. Sawant

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<421::AID-ADMA421>3.0.CO;2-7

      The fractal nature of a nanofibrous network has been discovered by in-situ measurements on fibers of N-lauroyl-L-glutamic acid di-n-butylamide, which grow in isostearyl alcohol upon cooling; critical parameters are derived and discussed. Branching induced by crystallographic mismatch was identified as the nanofibers’ growth mechanism (see Figure for an SEM image; bifurcation positions are highlighted by dotted circles).

    7. Layered Silicates/Fluorinated Polyimide Nanocomposites for Advanced Dielectric Materials Applications (pages 426–429)

      L.-Y. Jiang, C.-M. Leu and K.-H. Wei

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<426::AID-ADMA426>3.0.CO;2-O

      Structured silicates/fluorinated polyimide nanocomposites display excellent water-absorption retardation behavior. This leads to lower leakage-current densities and lower dielectric constants under higher humidity conditions than those of the pristine fluorinated polyimides. Part of the chemical structure of the layered silicate used in this work is shown in the Figure.

    8. Novel, Bioclastic Route to Self-Assembled, 3D, Chemically Tailored Meso/Nanostructures: Shape-Preserving Reactive Conversion of Biosilica (Diatom) Microshells (pages 429–433)

      K.H. Sandhage, M.B. Dickerson, P.M. Huseman, M.A. Caranna, J.D. Clifton, T.A. Bull, T.J. Heibel, W.R. Overton and M.E.A. Schoenwaelder

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<429::AID-ADMA429>3.0.CO;2-C

      The reactive conversion of biosilica meso- and nanostrucures into new compositions with retention of shape and fine features is demonstrated. The shape-preserving nature of the chemical conversion process is illustrated for the reaction of silica-based diatom frustules with Mg gas to form MgO (see Figure). This technique is promising for the mass production of a variety of low-cost genetically engineered meso- and nanodevices.

    9. Efficient Electroluminescent Devices Based on a Chelated Osmium(II) Complex (pages 433–436)

      S. Bernhard, X. Gao, G.G. Malliaras and H.D. Abruña

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<433::AID-ADMA433>3.0.CO;2-W

      Red light from osmium complexes has been shown to occur with a peak radiance that exceeded 6000 cd m–2 at only 6 V. External quantum efficiencies that are of the order of 1 % have been achieved. The importance of ionic space charge effects in the mechanism of device operation is discussed here. The Figure shows the structure of the osmium complex.

    10. Oriented Crystalline Films of Tris(8-hydroxyquinoline) Aluminum(III): Growth of the Alpha Polymorph onto an Ultra-Oriented Poly(tetrafluoroethylene) Substrate (pages 436–439)

      J.-F. Moulin, M. Brinkmann, A. Thierry and J.-C. Wittmann

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<436::AID-ADMA436>3.0.CO;2-K

      Crystalline films of tris(8-hydroxyquinoline) aluminum(III) (Alq) have been grown on poly(tetrafluoroethylene) (PTFE) substrates. The nucleating ability of the PTFE substrate, which relies on a specific molecular structure, is discussed. The Figure shows the film morphology of a 15 nm Alq film deposited onto an oriented PTFE substrate at 100 °C. The scale bar corresponds to 1 μm.

    11. Novel Organic–Inorganic Mesophases: Self-Templating Synthesis and Intratubular Swelling (pages 439–443)

      E. Ruiz-Hitzky, S. Letaïef and V. Prévot

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<439::AID-ADMA439>3.0.CO;2-8

      Flexible, swellable organosilica tubes are the most remarkable new mesophase generated by co-hydrolysis of tetraalkylammonium-substituted trimethoxysilanes and TEOS. The composites self-organize into lamellar layers or hexagonal tubules, whose elastic walls allow the uptake of anionic or lipophilic species. The hexagonal-tube structure is retained even upon calcination to mesoporous silica (see Figure for a TEM image).

    12. “Smart” Glasses: Molecular Programming of Rapid Dynamic Responses in Organosilica Sol–Gels (pages 443–447)

      M.S. Rao and B.C. Dave

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<443::AID-ADMA443>3.0.CO;2-S

      “Intelligent” organosilica sol–gels that show fast dynamic response to temperature, pH, and electric fields are presented. A bis-(propyl)ethylenediamine bridge is responsible for a change of water affinity under environmental stimuli, resulting in water expulsion or uptake by the polymeric network. The Figure shows the tips of a tweezer-like sol–gel device that opens and closes upon pH fluctuation.

    13. Reversal of Circular Bragg Phenomenon in Ferrocholesteric Materials with Negative Real Permittivities and Permeabilities (pages 447–449)

      A. Lakhtakia

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<447::AID-ADMA447>3.0.CO;2-C

      A reversal of the Bragg phenomenon is shown to exist theoretically in a right/left-handed ferrocholesteric slab with negative real permittivities and permeabilities. In addition to the promise of isotropic homogeneous materials with negative real permittivities and permeabilities for unexpected applications (e.g., distortion-free lenses), the presented results underscore the similar potential of anisotropic inhomogeneous materials with analogous characteristics.

    14. Surface Layer Formation on Polypyrrole Films (pages 449–452)

      C. Masalles, S. Borrós, C. Viñas and F. Teixidor

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<449::AID-ADMA449>3.0.CO;2-4

      Crystalline films on the surface of a polypyrrole (see Figure for SEM image) are obtained electrochemically from cobalt(bis-dicarbolide)-doped polypyrrole in aqueous Bu4N+Cl, or (less effectively) in Bu4P+Cl solution. The films, which are unidirectional (inwards) cation barriers, are highly stable in aqueous media, apparently due to the anion’s extremely low water solubility, but are easily dissolved in acetonitrile.

    15. Carbon Nanotubes Prepared by Spinning and Carbonizing Fine Core–Shell Polymer Microspheres (pages 452–455)

      D. Huličová, K. Hosoi, S.-I. Kuroda, H. Abe and A. Oya

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<452::AID-ADMA452>3.0.CO;2-S

      Carbon nanotubes prepared from core–shell polymer particles are reported. As depicted in the Figure, polymethylmethacrylate (PMMA) core/polyacrylonitrile (PAN) shell microspheres are blended with a PMMA matrix, spun, and elongated. Then the shell is stabilized and finally carbonized to produce contaminant-free carbon nanotubes.

    16. FTIR Imaging of Polymer Dissolution (pages 457–460)

      J. Koenig

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<457::AID-ADMA457>3.0.CO;2-8

      Fast FTIR imaging is a useful technique for the characterization of multicomponent systems undergoing dynamic changes, such as diffusion and dissolution. The characterization of polymer dissolution is important and a wide range of experimental techniques have been employed to observe and record the behavior of polymer dissolution. The detector systems for fast FTIR imaging are rapidly being improved so that images can be obtained on the order of seconds, making fast FTIR a powerful tool for a wide range of imaging applications.

    17. Peptides Bound to Silicone Membranes and 3D Microfabrication for Cardiac Cell Culture (pages 461–463)

      S. Boateng, S.S. Lateef, C. Crot, D. Motlagh, T. Desai, A.M. Samarel, B. Russell and L. Hanley

      Article first published online: 12 MAR 2002 | DOI: 10.1002/1521-4095(20020318)14:6<461::AID-ADMA461>3.0.CO;2-S

      Silicone membranes are frequently used as flexible cell culture substrates in studies of cardiac mechano-biology. Such physiologically relevant models of cells in vitro are required for fundamental studies of the basic mechanisms of mechanical transduction at the cellular level. Microfabrication and peptide binding, as well as other advances in surface modification and microfabrication that promise further development in flexible cell culture systems, are discussed.