Advanced Materials

Cover image for Advanced Materials

March 1997

Volume 9, Issue 3

Pages fmi–fmi, 190–280

  1. Masthead

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

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090301

  2. Materials Forums

    1. Top of page
    2. Masthead
    3. Materials Forums
    4. Articles
    5. Communications
    6. Research News
    7. Book Reviews
    8. Conference Calendars
    1. Materials Forum (pages 190–192)

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090302

  3. Articles

    1. Top of page
    2. Masthead
    3. Materials Forums
    4. Articles
    5. Communications
    6. Research News
    7. Book Reviews
    8. Conference Calendars
    1. 1995 Impact factors (page 193)

      Peter Gregory

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090303

    2. Microscopy of Structural Ceramics (pages 195–217)

      Prof. Manfred Rühle

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090304

      The development of advanced structural ceramics, which are used in specific components working under extreme conditions, require their microstructural analysis. The microscopy of structural ceramics is reviewed, beginning with various imaging techniques. The important microstructural features of three ceramics—alumina (the Figure shows an internal sensor AFM image), zirconia, and silicon nitride—and several composites are briefly outlined. FIG.

  4. Communications

    1. Top of page
    2. Masthead
    3. Materials Forums
    4. Articles
    5. Communications
    6. Research News
    7. Book Reviews
    8. Conference Calendars
    1. Multicoloured chromophore for white-light-emitting diodes (pages 219–222)

      Thomas Christ, Dr. Andreas Greiner, Roland Sander, Volker Stümpflen and Prof. Joachim H. Wendorff

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090305

      Light-emitting diodes that emit white light require active materials that are able to emit throughout the entire visible spectrum. A simple approach is reported here, based on hist-guest systems in which the guest is a single chromophore and the host a polymer blend. It is demonstrated that the emission of the chromophore may depend strongly on the choice of the matrix polymer. The absorption, photoluminescence, and electroluminescence spectra of the chromophore PSA in matrices of polynorbornene, Durel (a polyarylate), polyvinylpyridine, and blends are presented.

    2. Derivatized electrodes in the construction of organic light emitting diodes (pages 222–225)

      Dr. Frank Nüesch, Lynda Si-Ahmed, Dr. Bernard François and Prof. Libero Zuppiroli

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090306

      Overcoming the disadvantages of organic light-emitting diodes (LEDs) is important if full advantage is to be taken of their benefits. It is shown that a significant increase in durability and decrease of the turn-on operating field can be achieved by attaching the electroactive polymer to the metal-oxide electrode chemically. The Figure shows a single-layer LED device with an electrode derivatized with a functionalized oligophenylene layer.

    3. NLO-polymers containing tert-butyloxycarbonyl protecting groups: Modification after processing leading to thermally stable nonlinear optical materials (pages 225–230)

      Dr. Michael Dörr, Prof. Rudolf Zentel, Dr. Martin Sprave, Dr. Jan Vydra and Dr. Manfred Eich

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090307

      A new polymer for nonlinear optics (NLO) based on male-imide/methylvinyliscocyanate precursor polymers is introduced. This side-chain copolymer is cured after spin-coating and before poling, which, by a thermally activated fragmentation reaction, leads to increased glass transition temperature, increased density of NLO chromophores, and reduced solubility. NLO materials will play an important role in optical telecommunications, but the problem of the chromophores relaxing back into the isotropic state must first be solved.

    4. An improved experimental determination of external photoluminescence quantum efficiency (pages 230–232)

      Dr. John C. de Mello, Dr. H. Felix Wittmann and Prof. Richard H. Friend

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090308

      The external photoluminescence quantum yield of, for example, thin film semiconductors can be conveniently determined using the improved integrating-sphere method (see Figure) presented here. Spectrally resolved detection allows the excitation source and the emission to be distinguished. The method will be particularly useful for samples with small Stocks' shifts or low photoluminescence quantum yields or for highly scattering samples. Fig

    5. Chemical tuning of the electronic properties of differently substituted 1,4-bis(styryl)benzenes, 2,6-bis(styryl)naphthalenes, and bis(thienylvinylene)benzenes and -naphthalenes (pages 233–236)

      Stefanie E. Döttinger, Prof. Michael Hanack, Dr. José L. Segura, Elke Steinhuber, Michael Hohloch, Alfred Tompert and Prof. Dieter Oelkrug

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090309

      Tuning of the electrical and optical properties of a series of polyphenylenevinylene (PPV) derivatives has been demonstrated using photoluminescence spectroscopy. The synthesis of the title compounds is described and the effect of substituting electron-donating and electron-withdrawing groups in them is correlated with the photoluminescence spectra and electrochemical data. The compounds are shown to be suitable models leading to an understanding of the behavior of configurated polymers as active layers in light-emitting diodes.

    6. Electrodeposited quantum dots: Coherent nanocrystalline cdse on oriented polycrystalline au films (pages 236–238)

      Dr. Yuva Golan, Boaz Alperson, Dr. John L. Hutchison, Dr. Gary Hodes and Dr. Israel Rubinstein

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090310

      The formation of highly coherent nanocrystalline semiconductor films on polycrystalline metal substrates has important practical and theoretical implications. Electron diffraction patterns reveal that quantum dots (QDs) of CdSe grown on a gold film on a mica substrate are coherent over several micrometers in the lateral directions (see Figure), while in the case of a glass substrate there is a complete loss of epitaxy for QD layers not in direct contact with the gold. Fig.

    7. 5, 5″-Bis{4-[bis(4-methylphenyl)amino]phenyl}2, 2′:5′, 2″-terthiophene and 5, 5‴-bis{4-[Bis(4-methylphenyl)amino]phenyl}2, 2′:5′, 2″:5″, 2‴-quaterthiophene as a Novel Family of Amorphous Molecular Materials (pages 239–241)

      Tetsuya Noda, Ichiro Imae, Naoki Noma and Prof. Yasuhiko Shirota

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090311

      A novel family of photo-and electroactive amorphous molecular materials containing an oligothiophene moiety linked to two triphenylamine moieties has been designed and synthesized (see Figure). Their glass-forming properties, morphological changes, and molecualr and solid-state properties are described. They are reported to exhibit multiredox behavior on electrochemical oxidation.

    8. Liquid crystalline macrocycles: Novel glass-forming nematic materials that can undergo charge transfer induced phase transitions (pages 241–244)

      Bernhard Neumann, Dr. Detlev Joachimi and Prof. Carsten Tschierske

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090312

      Macrocyclic liquid crystals incorporating two different rigid cores are reported for the first time. The synthesis of polyethercyclophanes such as that shown in the Figure is described, together with their phase behavior as investigated by differential scanning calorimetry and polarizing microscopy. The synthesis of macrocycles that combine non-identical building blocks is describe in order to obtain materials with tailor-made properties.

    9. Structure and optical property changes of sol-gel derived VO2 thin films (pages 244–246)

      Songwei Lu, Prof. Lisong Hou and Prof. Fuxi Gan

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090313

      The semiconductor–metal phase change in VO2 at approximately 67°C, which results in great changes in its optical, electrical, and magnetic properties, is described in detail. The synthesis of VO2 thin films by the sol-gel method is outlined and the structure and optical properties are characterized, including hysteresis phenomena in the transmittance–temperature and reflectivity–temperature plots. A mechanism of the phase change—confirmed to be the monoclinic-to-tetragonal rutile transition—is proposed based on coordinative field theory.

    10. Nitrido-sodalite Zn6[P12N24] as a material for reversible hydrogen encapsulation (pages 247–248)

      Prof. Jens Weitkamp, Dr. Stefan Ernst, Fernando Cubero, Frank Wester and Prof. Wolfgang Schnick

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090314

      Host–guest behavior in a nitrido-sodalite is reported for the first time. The novel nitrido-sodalite Zn6[P12N24] has the usual nitrido-sodalite structure with PN4 corner-sharing units, as shown i the Figure, except that the central anion and one quarter of the Zn2⊕ ions are absent, producing only partial filling of the β-cages. Hydrogen encapsulation in the β-cages is discussed.

    11. Bulk synthesis of the 135 K superconductor HgBa2Ca2Cu3O8+δ (pages 248–251)

      Graeme B. Peacock, Dr. Ian Gameson and Prof. Peter P. Edwards

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090315

      Bulk synthesis of the high-temperature superconductor HgBa2Ca2O8+δ (Hg-1223)—an important step towards realizing its technological potential—is described. In the reaction discussed, the formation of bulk samples (up to 20 g) with excellent phase purity and transition temperatures above 130 K at ambient pressure proceeds from the binary oxides by a solid-state route. The significant advantages of this method compared to the high-pressure routes currently used are pointed out.

    12. Fabrication of polymeric microstructures with high aspect ratios using shrinkable polystyrene films (pages 251–254)

      Xiao-Mei Zhao, Dr. Younan Xia, Dong Qin and George M. Whitesides

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090316

      High-aspect-ratio polymeric structures have been fabricated using a process that combines reactive ion etching (RIE) and stress-oriented, shrinkable polystyrene films. It is reported how, after pattering of the surface of the polystyrene film by RIE, heating of the film caused it to shrink by a factor of 4–5 in the lateral dimensions while the thickness of the film and the features on it increased by a factor of ∼20 (see Figure). Fig.

    13. The synthesis of micrometer- and submicrometer-size spheres of ordered mesoporous oxide MCM-41 (pages 254–257)

      Michael Grün, Iris Lauer and Prof. Klaus K. Unger

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090317

      Spherical particles of the mesoporous material MCM-41 have been synthesized and are reported for the first time. The results of characterization of the samples by X-ray diffraction, scanning electron microscopy, and nitrogen sorption at 77 K (which provides information about the pore system) is described. It is shown that all the properties of the spherical MCM-41 particles are essentially the same as those of the MCM-41 materials synthesized by well-established methods. Finally, possibilities for future research are outlined.

    14. 3D Long-range ordering in ein SiO2 submicrometer-sphere sintered superstructure (pages 257–260)

      Raul Mayoral, Dr. Joaquin Requena, Prof. José S. Moya, Dr. Cefe López, Adelaida Cintas, Hernán Miguez, Dr. Francisco Meseguer, Dr. Luis Vázquez, Miguel Holgado and Álvaro Blanco

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090318

      Three-dimensional arrays of SiO2 nanometer particles lead to Bragg diffraction effects of visible light—as seen for natural opals, see also this issue's cover—and applications such as photonic bandgap materials. Teh fabrication of the opalline structures is described and details are given of how to obtain ordered compacts. The Figure shows a fracture surface of a sintered sample comprising 390 nm-diameter silica spheres.

  5. Research News

    1. Top of page
    2. Masthead
    3. Materials Forums
    4. Articles
    5. Communications
    6. Research News
    7. Book Reviews
    8. Conference Calendars
    1. Self-compression and diamond formation in carbon onions (pages 261–263)

      Dr. Florian Banhart and Dr. Pulickel M. Ajayan

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090319

      Carbon onions—concentric spherical graphite layers stacked one inside the other—are stable only during electron irradiation. If the irradiation is continued at high temperature, self-compression is shown to occur, in which the individual layers are compressed until the onion cores finally transform into diamond crystals, which then grow under further radiation. Two scenarios are sketched for the mechanism of pressureless transformation of graphitic materials into diamond and the consequences of these observations for future work are highlighted.

    2. The phthalocyanine approach to second harmonic generation (pages 265–269)

      Germa de la Torre, Prof. Tomás Torres and Prof. Fernando Agulló-López

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090320

      Phthalocyanine-based nonlinear optical (NLO) materials are reviewed, with particular emphasis on second-order effects. The requirements on materials and molecules for NLO activity are outlined before three recently studied families are briefly considered: asymmetrically substituted phthalocyanines (Pcs), subphthalocyanines.

    3. Persistent photoinduced effects in high-Te superconductors (pages 271–273)

      Axel Hoffmann, Dr. Dmitry Reznik and Prof. Ivan K. Schuller

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090321

      The reaction of high-temperature cuprate superconductors to illumination differs from the reaction produced in conventional superconductors. Two such effects, reviewed here, are persistent photoconductivity and persistent photoinduced superconductivity. For example, REBa2Cu3Ox thin films show a decrease in the normal state resistance and an increase of Tc which persist for a long time at low temperatures (< 100 K). The experimental investigations and results are briefly presented, before two alternative theoretical models are considered.

  6. Book Reviews

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

    1. Top of page
    2. Masthead
    3. Materials Forums
    4. Articles
    5. Communications
    6. Research News
    7. Book Reviews
    8. Conference Calendars
    1. Conference Calendar (pages 278–280)

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090328

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