Advanced Materials

Cover image for Advanced Materials

August 1996

Volume 8, Issue 8

Pages fmi–fmi, 613–702

  1. Masthead

    1. Top of page
    2. Masthead
    3. Articles
    4. Review
    5. Communications
    6. Research News
    7. Materials Forum
    8. Book Reviews
    1. Masthead (page fmi)

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080801

  2. Articles

    1. Top of page
    2. Masthead
    3. Articles
    4. Review
    5. Communications
    6. Research News
    7. Materials Forum
    8. Book Reviews
    1. Quality polymer science (page 613)

      Peter Gregory

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080802

      Full Papers in Advanced Materials? No, but manuscripts of such articles are regularly received at the Editorial Offices of Advanced Materials and promptly returned to their authors with the suggestion that they are submitted elsewhere. A possible alternative journal for articles (including Full Papers) on polymer physics and chemistry is Acta Polymerica. The various types of contributions to this journal are presented and attention is drawn to the sample issue of Acta Polymerica that is included with Advanced Materials this month.

  3. Review

    1. Top of page
    2. Masthead
    3. Articles
    4. Review
    5. Communications
    6. Research News
    7. Materials Forum
    8. Book Reviews
    1. Langmuir monolayers and Langmuir–Blodgett multilayers containing macrocyclic ionophores (pages 615–630)

      Dr. Igor K. Lednev and Prof. Michael C. Petty

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080803

      Macrocyclic ionophores in thin films are of interest for sensors or novel ionophotoswitching devices. Continuing work on floating monolayers and Langmuir–Blodgett multilayers of macrocyclic ionophores—such as crown ether ionophores, cyclodextrins and valinomycin—is reviewed. The figure shows a schematic representation of the complex of valinomycin (a biopolymer based on a 36-membered ring) with potassium.

  4. Communications

    1. Top of page
    2. Masthead
    3. Articles
    4. Review
    5. Communications
    6. Research News
    7. Materials Forum
    8. Book Reviews
    1. Epitaxial size control by mismatch tuning in electrodeposited Cd(Se, Te) quantum dots on {111} gold (pages 631–633)

      Dr. Yuval Golan, Dr. John L. Hutchison, Dr. Israel Rubinstein and Dr. Gary Hodes

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080804

      Since the crystal size of semiconductor quantum dots (QDs) affects the optoelectronic properties of QDs, a method of controlling the size is important. It is demonstrated that CdSe QDs electrodeposited epitaxially on {111} Au can be tuned from <5 to ∼ 20 nm by introducing small amounts of Te into the electrodeposited CdSe, i.e., by decreasing the mismatch between the deposited layer and the substrate. A further advantage of this technique is the ability to vary the bandgap continuously and controllably.

    2. Polypyrrole towers grown with the scanning electrochemical microscope (pages 634–637)

      Christine Kranz, Prof. Hermann E. Gaub and Prof. Wolfgang Schuhmann

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080805

      Conducting-polymer towers have been fabricated by a template-less method from homogeneous monomer solution using the scanning electrochemical microscope (SECM). The features of the topography feedback mode of the SECM—in which the microelectrode is vibrated laterally (thin arrows in the Figure)—are described and the characterization of polypyrrole towers (illustrated on the front cover) detailed. Uses in biosensors are foreseen.

    3. Ultrathin graphite oxide–polyelectrolyte composites prepared by self-assembly: Transition between conductive and non-conductive states (pages 637–641)

      Dr. Nicholas A. Kotov, Prof. Imre Dékány and Prof. Janos H. Fendler

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080806

      Ultrathin films of graphite–polymer composites, which are required for sensors applications, are the target of the work reported here. The preparation and characterization of ultrathin films composed of self-assembled graphite oxide (GO) platelets and polyelectrolytes are described, followed by the in situ reduction of GO to a conductive graphite-like state (G) by chemical and electrochemical methods. Particular attention is paid to the non-conductive to conductive transition that occurs on reduction and the behavior of incorporated CdS particles.

    4. Template synthesis of a large, self-supporting graphite film in montmorillonite (pages 641–644)

      Munetoshi Isayama, Kazuko Nomiyama and Prof. Toyoki Kunitake

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080807

      Large, self-supporting graphite films (e.g., see Figure) have been prepared using phosphate-treated montmorillonite, a clay, as a template. The preparation—intercalation of the montmorillonite with a copolymer from an aqueous dispersion, conversion of the copolymer component to amorphous carbon, heat treatment to give a highly oriented graphite film—and characterization of the films are described.

    5. Dielectric relaxation processes in a brick-like metallomesogen ferroelectric liquid crystal (pages 644–647)

      Santos Merino, Dr. François de Daran, Prof. M. Rosario De La Fuente, Prof. Miguel Angel Pérez Jubindo, Raquel Iglesias and Dr. Mercedes Marcos

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080808

      A non-typical ferroelectric liquid crystal (LC), i.e., one that is brick shaped—rather than cylindrical—with an oxovanadium metallic center incorporated in its mesogenic core, is shown to exhibit an unusual dielectric response, owing to its highly biaxial molecular nature, with frequencies lower than those found in other ferroelectric LCs. This is the first time that both the Goldstone mode (related to azimuthal fluctuations) and the soft mode (related to fluctuations in the tilt angle) have been characterized for a ferroelectric metallomesogen.

    6. Three–dimensional helical supramolecules—elucidation of magnetic ordering for an antiferromagnetic phase (pages 647–651)

      Dr. Silvio Decurtins, Dr. Helmut W. Schmalle, René Pellaux, Reto Huber, Dr. Peter Fischer and Dr. Bachir Ouladdiaf

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080809

      A novel helical three-dimensional supramolecular system has been investigated by neutron diffraction to determine the magnetic ordering in the antiferromagnetic phase. The representative system investigated (see Figure) is a MnII-containing chiral network based on two types of preorganized transition-metal complexes as complementary molecular partners that form a highly organized three-dimensional supramolecular host–guest system.

    7. Polarized photoluminescence of oligothiophenes in nematic liquid crystalline matrices (pages 651–654)

      Dr. N. Serdar Sariciftci, Dr. Uli Lemmer, Dr. Dan Vacar, Prof. Alan J. Heeger and Dr. Rene A. J. Janssen

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080810

      The macroscopic alignment of an extended conjugated oligomer by the simple means of embedding it in a liquid crystalline matrix and utilizing the properties of the host is demonstrated. That the orientation of the oligothiophene, in this case α-sexithiophenyl, can be dynamically switched with the host nematic lattice upon application of an electric field is observed by the switching of the polarized photoluminescence. This simple procedure for orientation opens up new areas for detailed study of this class of materials.

    8. Scanning probe microscopy of polymeric methyltrioxorhenium (pages 654–657)

      Dr. Mike R. Mattner, Prof. Wolfgang A. Herrmann, Rüdiger Berger, Dr. Christoph Gerber and Dr. Jim K. Gimzewski

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080811

      The surface of polymeric methyltrioxorhenium (poly-MTO), which is an intercalation compound with water layers as the guest in a lamellar host lattice, is shown by scanning probe techniques to consist of randomly intersecting crystalline regions with small crystallite facets. The edges of these facets exhibit steps (see Figure), the size of which can be explained in terms of the layered structure.

    9. Temperature dependence of the electroluminescent characteristics of light-emitting diodes made from poly(methylphenylsilane) (pages 657–659)

      Dr. Hiroyuki Suzuki

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080812

      Polysilanes—Si-based σ-conjugated polymers—have electronic structures markedly different from those of π-conjugated polymers. The temperature dependence of the electroluminescent properties of single-layer LEDs made from poly(methylphenylsilane) is reported and it is demonstrated that these LEDs can be used as light sources in the near UV region. Observation of electroluminescence from one of the most typical polysilanes is encouraging as it indicates that there is potential for further improvements.

    10. Microstructure of block copolymer reinforced interfaces observed with frictional force microscopy (pages 660–662)

      Dr. Klaus D. Jandt, Dr. Chi-An Dai and Prof. Edward J. Krämer

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080813

      The microstructure of block copolymer-reinforced interfaces of homopolymers has been studied by frictional force microscopy (FFM). The FFM micrograph in the Figure shows details, e.g., lamellar branching, of a poly(styrene)/poly(2-vinylpyridine) (PS/PVP) homopolymer interface reinforced with a PVP–PS–PVP triblock copolymer. An explanation for the need to “develop” the FFM image is proposed and the advantages of FFM over TEM are discussed.

    11. New LEDs based on soluble poly(2,6-naphthylenevinylene) (pages 663–666)

      Prof. Michael Hanack, Dr. José L. Segura and Dr. Hubert Spreitzer

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080814

      A soluble polymer attractive for light emitting devices has been prepared and its performance in LED applications evaluated. The chemical synthesis of the monomers is described, followed by their polymerization to a highly soluble, readily processable, cyanosubstituted poly(2,6-naphthylenevinylene). Electroluminescence and photoluminescence spectra are presented and an electrochemical study reported. It is shown that the presence of the naphthalene units induces a strong blue-shift in the emission color.

    12. Ripening and formation of microcrystals of oligo(cyclohexylidene) oxime derivative produced by spin-coating: Atomic force microscopy study (pages 666–668)

      Dr. Erik ten Grotenhuis, Prof. Jan van der Eerden, Dr. Frank Hoogesteger and Prof. Leonardus Jenneskens

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080815

      Microcrystals are formed after a ripening period when an oligo(cyclohexylidene) oxime derivative is deposited on silicon wafers by spin-coating. Results are presented related to this behavior, including atomic force microscopy images such as that shown here of crystals that had developed 3 h after deposition of the initial soft layer. AFM and X-ray diffraction data are compared.

    13. Ba2ErCl7—a new near IR to near UV upconversion material (pages 668–672)

      Philipp Egger, Peter Rogin, Toni Riedener, Prof. Hans Ulrich Güdel, Dr. Mathias Siegfried Wickleder and Prof. Jürg Hulliger

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080816

      New near IR to near UV upconversion (UC) materials are required for the development of solid state lasers pumped by laser diodes. Two materials are reported: an air-stable and efficient UC material emitting mostly in the yellowish-green and a very promising UC compound, Ba2ErCl7, which is being further characterized spectroscopically. THe general requirements for UC materials are briefly discussed, and the preparation of Ba2ErCl7 detailed. The intensity of individual emission bands is compared for known and new UC materials.

    14. Guanidyl and phosphoraniminyl substituents: New electron donors in second-order nonlinear optical chromophores (pages 672–675)

      Prof. Peter Boldt, Thomas Eisenträger, Christoph Glania, Jörg Göldenitz, Dr. Peter Krämer, Ralf Matschiner, Jens Rase, Dr. Reinhard Schwesinger, Jürgen Wichern and Dr. Rüdiger Wortmann

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080817

      Improved donor groups for chromophores play a major role in the development of organic materials for nonlinear optics. Guanidyl and phosphoraniminyl residues are examined as donors in one-dimensional organic nonlinear optical chromophores such as that shown in the Figure. The results of electrooptical absorption (EOAM) and electric field induced second harmonic generation (EFISH) measurements are presented and discussed.

  5. Research News

    1. Top of page
    2. Masthead
    3. Articles
    4. Review
    5. Communications
    6. Research News
    7. Materials Forum
    8. Book Reviews
    1. Non-classical donor–acceptor chromophores for second order nonlinear optics (pages 677–680)

      Prof. Man Shing Wong, Dr. Christian Bosshard, Dr. Feng Pan and Prof. Peter Günter

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080818

      Optoelectronic components require materials with large second-order nonlinearities. Recently, various types of non-classical chromophores have been developed, in the hope that they have improved physical properties for materials formation. The main research directions and latest developments reviewed here include multi-dipolar chromophoric assemblies, multiple donor and acceptor chromophores, non-rod-shaped dipolar chromophores, and non-conjugated donor-acceptor chromophores, in which the charge transfer process is through space instead of the π-conjugated bridge.

    2. Chiroptical molecular switches (pages 681–684)

      Prof. Ben L. Feringa, Dr. Nina P. M. Huck and Dr. Anne Marie Schoevaars

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080819

      The control of chirality by optical molecular switches offers intriguing prospects in the design of new materials. For example, photochemically induced stilbene-type cis-trans isomerization of 1 (see Figure) results simultaneously in reversal of the helicity. The molecular design of switching units, the possibility of highly stereoselective optical molecular switching, and an approach to a gated response are described.

    3. Turning down the heat on semiconductor growth: Solution-chemical syntheses and the solution-liquid-solid mechanism (pages 685–688)

      Prof. William E. Buhro, Kathleen M. Hickman and Timothy J. Trentler

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080820

      Semiconductor crystal growth at low temperatures and under mild reaction conditions would usher in a technological revolution. Following a brief discussion of the processes that occur during crystal growth, several growth techniques are described, including electrodeposition and surfactant-interface growth. Particular attention is paid to solution–liquid–solid growth, a technique discovered by the authors that resembles a living polymerization and a phase transfer reaction, by which crystalline III—V materials are produced at the lowest known growth temperatures.

    4. InGaN-based blue/green LEDs and laser diodes (pages 689–692)

      Dr. Shuji Nakamura

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080821

      High-brightness blue LEDs and laser diodes for use in full color displays etc. have recently become available. Recent developments such as blue/green single-quantum-well (SQW) LEDs and a violet InGaN multiquantum-well (MQW) laser diode—shown working on the inside front cover of the issue—are reviewed, including the electroluminescent and optical spectra of the devices. The results indicate the possibility that short wavelength laser diodes, from green to UV, will be realized in the near future using III–V nitride materials.

  6. Materials Forum

    1. Top of page
    2. Masthead
    3. Articles
    4. Review
    5. Communications
    6. Research News
    7. Materials Forum
    8. Book Reviews
    1. Materials Forum (pages 696–697)

      Paul Mulvaney

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19960080822

  7. Book Reviews

    1. Top of page
    2. Masthead
    3. Articles
    4. Review
    5. Communications
    6. Research News
    7. Materials Forum
    8. Book Reviews

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