Advanced Materials

Cover image for Vol. 14 Issue 10

May, 2002

Volume 14, Issue 10

Pages 691–762

    1. Contents: Adv. Mater. 10/2002 (pages 691–694)

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<691::AID-ADMA691>3.0.CO;2-9

    2. Contents: Adv. Funct. Mater. 5/2002 (pages 696–698)

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<696::AID-ADMA696>3.0.CO;2-Q

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    4. Fluorescence and Phosphorescence in Organic Materials (pages 701–707)

      A. Köhler, J.S. Wilson and R.H. Friend

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<701::AID-ADMA701>3.0.CO;2-4

      Control over organic luminescent and phosphorescent materials has advanced significantly over the last year, as highlighted in this progress report. The efficiencies of organic based devices have been shown to be competitive with those of their inorganic counterparts. Optimizing the out-coupling of light from the device structure is an important research topic that will be explored further in the future.

    5. Advanced Engineering Ceramics (pages 709–716)

      P. Greil

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<709::AID-ADMA709>3.0.CO;2-9

      Advanced engineering ceramics based on monolithic, composite, and cellular (see Figure) architectures offer a wide range of tailored microstructures. Novel manufacturing techniques, structure tailoring, and new materials are discussed. Selected fields of applications, such as transportation, energy technology, and environmental industries, are focused upon. Multi-scale processing covering the nano- to the macroscale has become a great challenge.

    6. Dual Cathodically and Anodically Coloring Electrochromic Polymer Based on a Spiro Bipropylenedioxythiophene [(Poly(spiroBiProDOT)] (pages 717–719)

      B.D. Reeves, B.C. Thompson, K.A. Abboud, B.E. Smart and J.R. Reynolds

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<717::AID-ADMA717>3.0.CO;2-D

      Three color states and a large luminance change at intermediate potentials are the key features of a new alkylenedioxypolythiophene, in which two polymeric strands are linked by a spiro(bis-dioxacycloheptene) unit (see Figure). The seven-membered rings are quite flexible and allow coplanarity of both strands. The polymer is both cathodically and anodically coloring, showing a dark red neutral state and a dark blue oxidized state.

    7. Synthesis of Mesoporous Silicates with Controllable Pore Size Using Surfactant Ruthenium(II) Complexes as Templates (pages 719–722)

      V.W.-W. Yam, B. Li and N. Zhu

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<719::AID-ADMA719>3.0.CO;2-5

      Surfactant–ruthenium(II) complexes that display lyotropic liquid-crystalline behavior have been prepared. Their utility as templates for the synthesis of mesoporous silicates that contain RuO2 particles in their channels is demonstrated (see Figure). It is found that by simply altering the surfactant chain length the pore size of the metal-containing silicates can be altered in a controllable manner.

    8. Functional Group Transfer from Gold Nanoparticles to Flat Gold Surfaces for the Creation of Molecular Anchoring Points on Surfaces (pages 722–726)

      V. Paraschiv, S. Zapotoczny, M.R. de Jong, G.J. Vancso, J. Huskens and D.N. Reinhoudt

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<722::AID-ADMA722>3.0.CO;2-T

      Localized functionalization of surfaces using the concept illustrated in the Figure is introduced. Densely packed, monofunctionalized nanoparticles are linked to the surface via covalent bonding and then removed to leave isolated functional groups on the surface, to which other, smaller entities can then be attached. This method should be easily adaptable to a variety of materials and particle sizes.

    9. Charge Transport in Discotic Liquid Crystals: A Molecular Scale Description (pages 726–729)

      J. Cornil, V. Lemaur, J.-P. Calbert and J.-L. Brédas

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<726::AID-ADMA726>3.0.CO;2-D

      Discotic liquid crystals have emerged as very attractive organic semiconductors due to their high degree of ordering and self-healing capacity. Quantum-chemical calculations that describe the main parameters governing the charge-transfer processes in these systems at the molecular level are reported. The concepts are illustrated by considering columns made of triphenylene molecules and derivatives (see Figure).

    10. Spontaneous Patterning of Hexagonal Structures in an Azo-Polymer Using Light-Controlled Mass Transport (pages 729–732)

      C. Hubert, C. Fiorini-Debuisschert, I. Maurin, J.-M. Nunzi and P. Raimond

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<729::AID-ADMA729>3.0.CO;2-1

      Spontaneous formation of hexagonal surface relief patterns (see Figure) occurs upon uniform, coherent laser irradiation of a poly-(methylmethacrylate) with 35 % of the methyl ester groups replaced by an azo dye. The structures grow at a rate linearly dependent on the light intensity, above a threshold value. Using linearly polarized light, the elongation axis of the structures orients along the polarization direction.

    11. Contiguous Silver Nanoparticle Coatings on Dielectric Spheres (pages 732–736)

      T. Cassagneau and F. Caruso

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<732::AID-ADMA732>3.0.CO;2-P

      Solid and hollow metallo-dielectric spheres are created by layer-by-layer self-assembly. The discrete metallic nanoparticles, which make up the shell, form a contiguous layer that exhibits a collective plasmon resonance with a splitting of the dipole mode into transverse and longitudinal modes. The splitting can be controlled by the number of self- assembled octa(3-aminopropyl)silsesquioxane (NSi8) capped Ag nanoparticle (see Figure) layers deposited.

    12. A Silicon Nanowire with a Coulomb Blockade Effect at Room Temperature (pages 736–739)

      S.F. Hu, W.Z. Wong, S.S. Liu, Y.C. Wu, C.L. Sung, T.Y. Huang and T.J. Yang

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<736::AID-ADMA736>3.0.CO;2-9

      An extremely narrow and thin silicon wire has been fabricated on a silicon-on-insulator wafer (see Figure). The room-temperature Coulomb blockade effects as well as the influence of a capacitively coupled gate on the transport properties of this conducting silicon quantum wire are studied. The results obtained are encouraging for the application of such wires in single-electron transistors.

    13. Room-Temperature, Tunable Gain Media from Novel II–VI Nanocrystal–Titania Composite Matrices (pages 739–743)

      V.C. Sundar, H.-J. Eisler and M.G. Bawendi

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<739::AID-ADMA739>3.0.CO;2-Y

      Semiconductor nanocrystals embedded in a titania matrix (see Figure for an AFM image) at volume fractions high enough to observe amplified spontaneous emission (ASE) have been prepared. ASE has been observed at room temperature for these structures and at multiple wavelengths, thus promising a wide range of tunable, room-temperature lasers and other nonlinear optics applications.

    14. A Chemically Synthesized Artificial Pancreas: Release of Insulin from Glucose-Responsive Hydrogels (pages 743–746)

      A. Guiseppi-Elie, S.I. Brahim and D. Narinesingh

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<743::AID-ADMA743>3.0.CO;2-H

      Contact-lens-like polymeric hydrogels that are glucose-responsive have been synthesized by entrapping the enzyme glucose oxidase (GOx) within the polymer network. The polymeric hydrogels are pH-sensitive and act as glucose-responsive membranes effecting the release of insulin (see Figure). The release profile from a multi-laminated hydrogel device displays a sustained release of insulin in response to glucose.

    15. Laser Emission in a Dye Doped Cholesteric Polymer Network (pages 746–749)

      J. Schmidtke, W. Stille, H. Finkelmann and S.T. Kim

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<746::AID-ADMA746>3.0.CO;2-5

      A crosslinked cholesteric network doped with a fluorescent dye exhibits lasing efficiencies that are more than one order of magnitude higher than those of a low molar mass cholesteric liquid crystal (CLC) with similar optical parameters. The emission from the samples has been found to be stable, whereby the lasing threshold is much lower than that of the CLC compound. Films of the crosslinked sample can easily be peeled off their glass substrates and can be microstructured or coated to change the polarization of the emitted laser light.

    16. Low Surface Energy Conducting Polypyrrole Doped with a Fluorinated Counterion (pages 749–752)

      D. Mecerreyes, V. Alvaro, I. Cantero, M. Bengoetxea, P.A. Calvo, H. Grande, J. Rodriguez and J.A. Pomposo

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<749::AID-ADMA749>3.0.CO;2-U

      Fluorine-doped polypyrroles, combining the electrical properties of conducting polymers and the unique surface properties of fluorinated molecules, have been obtained by an easy and straightforward method. Using the fluorine co-dopant, fabrics with hydrophobic, fluorinated surfaces have been created, and a selective deposition of polypyrroles into textiles (see Figure) has also been achieved.

    17. Can Carbon Be Ferromagnetic? (pages 753–756)

      R. Höhne and P. Esquinazi

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<753::AID-ADMA753>3.0.CO;2-D

      Ferromagnetism in rhombohedral fullerene polymers (Rh-C60, see Figure for structure) has recently been observed. This behavior—also observed in highly oriented pyrolytic graphite (HOPG)—is commented on. Although it is cautioned that the influence of magnetic impurities cannot be ruled out, there are arguments for intrinsic ferromagnetism in Rh-C60.

    18. Measurements of Solid-State Photoluminescence Quantum Yields of Films Using a Fluorimeter (pages 757–758)

      L.-O. Pålsson and A.P. Monkman

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<757::AID-ADMA757>3.0.CO;2-Y

      The photoluminescence quantum yield of thin films can be measured using a commercial spectrofluorimeter in combination with an integrating sphere. The advantages of this set-up compared to those that are generally implemented are highlighted—for example, the need for bulky and expensive equipment is reduced and the excitation wavelength can be freely chosen in the 300–600 nm range of the spectrum. The fact that there is still scope for improvement, especially by utilizing the high detection sensitivity of the spectrometer, is also remarked upon.

    19. Conference Calendar: Adv. Mater. 10/2002 (pages 760–762)

      Article first published online: 17 MAY 2002 | DOI: 10.1002/1521-4095(20020517)14:10<760::AID-ADMA760>3.0.CO;2-L