Advanced Materials

Cover image for Vol. 14 Issue 11

June, 2002

Volume 14, Issue 11

Pages 767–854

    1. Contents: Adv. Mater. 11/2002 (pages 767–770)

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<767::AID-ADMA767>3.0.CO;2-X

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      In Profile: Stephen R. Forrest, Professor of Electrical Engineering, Princeton University (page 773)

      Version of Record online: 3 JUN 2002 | DOI: 10.1002/1521-4095(20020605)14:11<773::AID-ADMA773>3.0.CO;2-8

    3. Bio-inspired Materials Chemistry (pages 775–788)

      E. Dujardin and S. Mann

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<775::AID-ADMA775>3.0.CO;2-0

      Bio-inspired materials (see Figure for an example) have seen a surge in the last year in terms of both fabrication methods and applications. A wide range of soft, hard, or hybrid materials and interfaces are being explored with the promise of diverse applications in bioceramic implants, bionanotechnology, nanochemistry, and environmentally benign routes to functional materials.

    4. Molecules and Electronic Materials (pages 789–798)

      D. Cahen and G. Hodes

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<789::AID-ADMA789>3.0.CO;2-H

      Hybrid molecular/non-molecular structures (e.g., see Figure) are a useful intermediary to all-molecule circuits. In such structures, understanding the chemical nature of the electrical contact between molecules and metals or semiconductors is of vital importance. Cahen and Hodes report on the latest developments, including systems where molecules are the “glue” between two electronic materials.

    5. Micro-buckling as a Route Towards Surface Patterning (pages 799–802)

      J.S. Sharp and R.A.L. Jones

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<799::AID-ADMA799>3.0.CO;2-D

      Blister formation, growth, and collapse have been used to achieve patterning of polyester surfaces. The effect of the solvent volume fraction on the blistering length and the energetics of the surface interaction between the swollen polymer and the substrate have been studied. Patterning of the surface (see Figure) can easily be achieved by pretreatment of the surface through rubbing.

    6. Tuning Electronic Properties of Semiconductors by Adsorption of [60]Fullerene Carboxylic Acid Derivatives (pages 802–805)

      D. Bonifazi, A. Salomon, O. Enger, F. Diederich and D. Cahen

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<802::AID-ADMA802>3.0.CO;2-#

      Changing the electronic surface properties of GaAs and ZnO can be achieved by chemisorption of partial monolayers of C60 derivatives. This effect appears to depend on the way the C60 moiety is coupled to the semiconductor surface (see Figure), as shown by preliminary IV investigations of (n-GaAs C60 derivative)/Au solid-state diodes.

    7. Layer-by-Layer Self-Assembly of Reactive Polyelectrolytes for Robust Multilayer Patterning (pages 805–809)

      F. Shi, B. Dong, D. Qiu, J. Sun, T. Wu and X. Zhang

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<805::AID-ADMA805>3.0.CO;2-O

      Robust multilayer patterns have been created via layer-by-layer self-assembly using a photochemical linking process that involves aromatic azo group cleavage and coupling with carbonyl oxygens from an adjacent polymer strand. The patterning is based on the solubility difference of the photoreactive multilayer before and after UV irradiation. The Figure shows an AFM image of a stripe pattern obtained by selective irradiation.

    8. Triphenylamine-Substituted Polyfluorene—A Stable Blue-Emitter with Improved Charge Injection for Light-Emitting Diodes (pages 809–811)

      C. Ego, A.C. Grimsdale, F. Uckert, G. Yu, G. Srdanov and K. Müllen

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<809::AID-ADMA809>3.0.CO;2-8

      Efficient, stable blue light-emitting diodes (LEDs) might be achieved by using (poly[9,9-bis(triphenylamine)fluorene]) (see Figure) as a hole-transporting emissive layer. This polymer not only exhibits an initial pure blue emission with no aggregate/excimer emission, but also a much improved hole injection over standard poly(9,9-dialkylfluorene)s. The simple two-step synthesis from commercially available materials is also described.

    9. Surface Photovoltage NO Gas Sensor with Properties Dependent on the Structure of the Self-Ordered Mesoporous Silicate Film (pages 812–815)

      T. Yamada, H.-S. Zhou, H. Uchida, M. Tomita, Y. Ueno, T. Ichino, I. Honma, K. Asai and T. Katsube

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<812::AID-ADMA812>3.0.CO;2-W

      NO gas sensors based on nanoporous silicate films have been synthesized and evaluated with respect to their quasicrystalline structure. Whereas in the hexagonal assembly the surface layer is impermeable, allowing gas transport only sideways, a cubic phase with 3D isotropically distributed pores is highly suitable for measuring NO concentrations in gas streams (see Figure).

    10. Microbial Synthesis of Semiconductor PbS Nanocrystallites (pages 815–818)

      M. Kowshik, W. Vogel, J. Urban, S.K. Kulkarni and K.M. Paknikar

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<815::AID-ADMA815>3.0.CO;2-K

      The use of microbes as producers of semiconductor nanocrystals is demonstrated. When torulopsis yeast is challenged with lead, it builds intracellular spherical crystallites of PbS, 2–5 nm in diameter (see Figure for an HR-TEM image) and pure by X-ray diffraction. The crystals, which can be isolated by freeze-thawing, show a sharp absorption maximum at 330 nm, corresponding to a bandgap of 3.75 eV.

    11. Ultrafast Response and Superior Optical Limiting Effects of Planar “Open” Heterothiometallic Clusters (pages 818–822)

      C. Zhang, Y. Song, F.E. Kühn, Y. Wang, X. Xin and W.A. Herrmann

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<818::AID-ADMA818>3.0.CO;2-8

      Heterothiometallic clusters with a planar open skeleton (see Figure) show a better optical limiting performance than C60 towards picosecond laser pulses and are promising optical-power limiting materials. The influence of the cluster skeletons and the constitutent elements in the clusters on the optical-power limiting properties as well as the influence of the optical nonlinearities upon irradiation with pico- and nanosecond pulsed lasers are discussed.

    12. Star-Shaped Thieno-[3,4-b]-Pyrazines: A New Class of Red-Emitting Electroluminescent Materials (pages 822–826)

      K.R.J. Thomas, J.T. Lin, Y.-T. Tao and C.-H. Chuen

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<822::AID-ADMA822>3.0.CO;2-S

      A new class of pure red fluorescent dyes, which are both emitting and hole-transporting, has been designed. Thieno-[3,4-b]-pyrazines, fully substituted with bulky aryl substituents (giving the molecules an overall star shape, see Figure), could be easily synthesized by condensation of 2,5-diaryl-3,4-diaminothiophenes with 1,2-diaryl-1,2-diketones. Their absorption bands are typically around 320–330 and 450–530 nm.

    13. Extraordinary Overoxidation Resistance Increase in Self-Doped Polypyrroles by Using Non-conventional Low Charge-Density Anions (pages 826–829)

      C. Masalles, J. Llop, C. Viñas and F. Teixidor

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<826::AID-ADMA826>3.0.CO;2-C

      A cation exchange membrane formed via the polymerization of a cobaltabisdicarbollide unit with pyrrole is presented. The cobalt doping agent is covalently bound directly to the pyrrole unit (see Figure); no supporting electrolyte is necessary. An improved overoxidation resistance over the non-covalently linked counterpart is reported. Thus this new material is an excellent candidate for selective ion exchange resins controlled by an electrochemical potential.

    14. Formation of Nanosized TiO2 in Mesoporous Silica Thin Films (pages 830–833)

      Z.-L. Hua, J.-L. Shi, L.-X. Zhang, M.-L. Ruan and J.-N. Yan

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<830::AID-ADMA830>3.0.CO;2-W

      Nanosized TiO2 particles are incorporated into pore channels of mesoporous silica thin films (MSTFs) by a simple constituent-template displacement process, consisting of depositing MSTF on quartz slides, treatment with Ti(OBu)4, and heating. Ti is present in two coordination states, an anatase-like nanosized TiO2 phase, and isolated [TiO4] units in the framework or on the surface of the film. The Figure shows an HREM image of TiO2/MSTF.

    15. Large-Scale Synthesis of Uniform Silver Nanowires Through a Soft, Self-Seeding, Polyol Process (pages 833–837)

      Y. Sun and Y. Xia

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<833::AID-ADMA833>3.0.CO;2-K

      A self-seeding process is used to generate bicrystalline silver nanowires by reducing AgNO3 with ethylene glycol at ∼160 °C. The key to the success of this solution-phase approach is the use of a polymeric “coordination reagent” capable of controlling the growth rates of different faces of silver. Uniform nanowires (see Figure) could be routinely synthesized with diameters of ∼60 nm and lengths up to ∼50 μm.

    16. Preparation of Smooth Single-Crystal Mn3O4 Nanowires (pages 837–840)

      W.Z. Wang, C.K. Xu, G.H. Wang, Y.K. Liu and C.L. Zheng

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<837::AID-ADMA837>3.0.CO;2-4

      A simple synthesis of Mn3O4 nanowires is presented. After thoroughly grinding the precursors together, simply heating the product to 850 °C in the presence of NaCl and the surfactant NP-9 produces single-crystal nanowires 40–80 nm in diameter and up to 150 μm in length (see Figure for a TEM image). From the morphology of the nanowires, Ostwald ripening is concluded to be the main formation mechanism.

    17. Molecular Azo Glasses as Grating Couplers and Resonators for Optical Devices (pages 841–843)

      A. Perschke and T. Fuhrmann

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<841::AID-ADMA841>3.0.CO;2-O

      Nanometer-sized corrugation gratings that act as light couplers and resonators are produced holographically by subjecting a glassy film of an azo dye to crossed circularly polarized argon laser beams (see Figure for an example with periodicity and depth in the upper nanometer range). The gratings are remarkably long-term stable even under electrical stress and can easily be integrated into multilayer organic optical devices.

    18. Nanomaterials-Based Electrochromics for Paper-Quality Displays (pages 845–848)

      U. Bach, D. Corr, D. Lupo, F. Pichot and M. Ryan

      Version of Record online: 29 MAY 2002 | DOI: 10.1002/1521-4095(20020605)14:11<845::AID-ADMA845>3.0.CO;2-8

      High-quality paper-like electrochromic displays are becoming a reality! Nanostructured films, composed of semiconductive nanoparticles modified with organic electrochromophores exhibit high coloration efficiency, and amplify the color change through their extremely high surface area. A schematic of a display device is shown in the Figure.

    19. Book Review: Handbook of Applied Surface and Colloidal Chemistry. By K. Holmberg (Ed.) (page 849)

      Y. Xia

      Version of Record online: 3 JUN 2002 | DOI: 10.1002/1521-4095(20020605)14:11<849::AID-ADMA849>3.0.CO;2-T

    20. Book Review: Molecular Switches. By Ben L. Feringa (Ed.) (pages 849–850)

      N. L. Branda

      Version of Record online: 3 JUN 2002 | DOI: 10.1002/1521-4095(20020605)14:11<849::AID-ADMA1111849>3.0.CO;2-L

    21. Book Review: Integrated Silicon Optoelectronics. By Horst Zimmermann (page 850)

      U. Gösele

      Version of Record online: 3 JUN 2002 | DOI: 10.1002/1521-4095(20020605)14:11<850::AID-ADMA850>3.0.CO;2-O

    22. Conference Calendar: Adv. Mater. 11/2002 (pages 851–854)

      Version of Record online: 3 JUN 2002 | DOI: 10.1002/1521-4095(20020605)14:11<851::AID-ADMA851>3.0.CO;2-K