Advanced Materials

Cover image for Vol. 13 Issue 5

March, 2001

Volume 13, Issue 5

Pages 305–358

    1. Materials Research Society Fall Meeting in Bosten (pages 305–306)

      C. Barzen

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<305::AID-ADMA305>3.0.CO;2-X

      The Materials Research Society (MRS) Fall Meeting took place once again at the end of November 2000 in Boston. A wide variety of topics, ranging from nano- and microstructured materials, to semiconductors and metals, materials processing and characterization, and organic and hybrid materials, were addressed. Some of the highlights of this meeting, which was attended by around 4500 people, are described in this essay.

    2. Mesostructured Silica Fibers: Ring Structures in Reciprocal Space (pages 307–310)

      F. Marlow, I. Leike, C. Weidenthaler, C. W. Lehmann and U. Wilczok

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<307::AID-ADMA307>3.0.CO;2-P

      Mesostructured silica fibers constitute a class of highly ordered solidswhose reciprocal space consists of well-defined extended ring structures (see Figure). Their X-ray diffraction spots cannot be described by the Bragg equation: As described here, they exhibit unusual intensity differences between symmetry-related spots and local minima arising from the circular fiber architecture (see also cover).

    3. Force Modulation Atomic Force Microscopy as a Powerful Tool in Organic–Inorganic Hybrid Materials Analysis (pages 310–313)

      G. Schiavon, J. G. Kuchler, B. Corain and W. Hiller

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<310::AID-ADMA310>3.0.CO;2-C

      A combination of force modulation and atomic force microscopyhas been successfully applied to the structure analysis of hybrid materials for the first time (a typical image is shown in the Figure). This method allows the investigation of phase separation and surface distribution properties of organic–inorganic hybrid materials as a function of their composition.

    4. Epitaxial Growth of Thiophene/p-Phenylene Co-oligomers for Highly Polarized Light-Emitting Crystals (pages 313–317)

      H. Yanagi, T. Morikawa, S. Hotta and K. Yase

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<313::AID-ADMA313>3.0.CO;2-0

      Polarized photoluminescence in orientated thin films of π-conjugated oligomers is demonstrated here. Vapor-deposited thiophene/p-phenylene co-oligomers are described and it is shown that these molecules form epitaxial needle-like crystals (see Figure). Molecular modification of the co-oligomers enables the emission color to be tuned and the epitaxial crystallization to be controlled, thus leading to polarized emissions of light.

    5. Temperature Dependence of Si Nanowire Morphology (pages 317–320)

      H. Y. Peng, Z. W. Pan, L. Xu, X. H. Fan, N. Wang, C. S. Lee and S. T. Lee

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<317::AID-ADMA317>3.0.CO;2-L

      Si nanostructures, including plain, tadpole-like, and chain-like nanowires(see Figure) have been fabricated under well-defined conditions. The morphology of the nanowires and the growth mechanism are shown to be dependent on the growth/substrate temperature, and can be explained by the existence of a spheroidization process.

    6. Novel Cross-linked Organic Materials with Pronounced Spontaneous Polarization Based on Bis-Dipolar Molecules (pages 321–323)

      C.-D. Keum, A. Kanazawa and T. Ikeda

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<321::AID-ADMA321>3.0.CO;2-4

      Crosslinkable banana-shaped ferroelectric liquid crystals (LCs) are expected to show excellent thermal and mechanical stability upon polymerization as well as long-term stability. A new bis-dipolar crosslinkable monomer/conventional banana LC mixture is explored by these authors and the molecular alignment changes before and after polymerization are examined. A polymerization-induced phase structure is observed (see Figure).

    7. Lasing in a Microcavity with an Oriented Liquid-Crystalline Polyfluorene Copolymer as Active Layer (pages 323–327)

      M. Theander, T. Granlund, D. M. Johanson, A. Ruseckas, V. Sundström, M. R. Andersson and O. Inganäs

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<323::AID-ADMA323>3.0.CO;2-X

      The use of layers with anisotropic molecular orientation in microcavities provides a means for the fabrication of lasing devices based on polyfluorene copolymers. The Figure shows the structure of the polymer film formed by the spin-coating of two mirrors with chloroform solutions of the polymers and pressing them together. The photopumped laser thus achieved shows a low lasing threshold.

    8. Alcothermal Synthesis under Basic Conditions of an SBA-15 with Long-Range Order and Stability (pages 327–331)

      J.-H. Sun, J. A. Moulijn, J. C. Jansen, T. Maschmeyer and M.-O. Coppens

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<327::AID-ADMA327>3.0.CO;2-H

      High-quality large-pore molecular sieves can be synthesized via the practical two-step method introduced here. Based on alcothermal treatment, this approach allows expansion of the pores of the parent hexagonal mesoporous material in a tunable manner and in addition improves the stability and long-range order (see Figure) of the material.

    9. General Route to Homogeneous, Mesoporous, Multicomponent Oxides Based on the Thermolytic Transformation of Molecular Precursors in Non-polar Media (pages 331–335)

      J. W. Kriesel, M. S. Sander and T. D. Tilley

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<331::AID-ADMA331>3.0.CO;2-0

      Mesoporous mixed-element oxides have proved difficult to synthesize via the surfactant template method that has been applied so successfully to silica. A synthetic strategy based on the use of molecular precursors in conjunction with block copolymer templates is revealed here for the production of homogeneous multi-component oxides (see Figure).

    10. Molecular Identification by Time-Resolved Interferometry in a Porous Silicon Film (pages 335–338)

      S. E. Létant and M. J. Sailor

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<335::AID-ADMA335>3.0.CO;2-L

      Porous silicon is becoming increasingly important for the sensitive detection of liquid and gaseous analytes due to its high surface area and tunable porosity and functionality. These authors report the first use of porous silicon for the analysis of mixtures of chemical compounds. Using time-resolved reflectivity measurements to analyze ethanol and acetone mixtures, they found that the components could be separated temporally in the porous Si film in a process that is analogous to gas chromatography, the porous Si film playing the dual role of separation column and detector.

    11. Novel Lithium-Ion Conducting Gels with a Tailor-Made Concentration Gradient and Their Use in Secondary Lithium Metal Batteries (pages 338–341)

      R. R. M. Hikmet and I. Michels

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<338::AID-ADMA338>3.0.CO;2-9

      Novel ion-conducting polymer gelswith a tailor-made composition gradient are presented. Such gels can be used in secondary lithium metal batteries to improve the cycling efficiency. The gradient is created by a UV absorber, which causes the polymerization to proceed at different rates across the sample. The morphology of a gel with such a gradient is shown in the Figure.

    12. Linear Superclusters of Colloidal Gold Particles by Electrostatic Assembly on DNA Templates (pages 341–344)

      A. Kumar, M. Pattarkine, M. Bhadbhade, A. B. Mandale, K. N. Ganesh, S. S. Datar, C. V. Dharmadhikari and M. Sastry

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<341::AID-ADMA341>3.0.CO;2-X

      The organization of nanoparticles into superstructures of predefined geometry is an important challenge in the area of nanoscale architecture. Attractive Coulombic interaction between positively charged amine groups on gold particle surfaces and negatively charged phosphate backbones of DNA molecules (see Figure) drives the self-assembly of gold nanoparticles into linear supercluster structures.

    13. Neuron-Silicon Self-Excitation: A Prototype of Iono-Electronics (pages 344–347)

      M. Ulbrich and P. Fromherz

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<344::AID-ADMA344>3.0.CO;2-L

      A first step towards neuronal microprosthetics has been taken by implementing a system of neuronal self-excitation on a silicon chip. This exercise demonstrates that integration of the microelectronics of semiconductors with the ionics of nerve cells can be achieved on a microscopic level. This may be the starting point for far reaching developments in biomedical and computational applications where non-invasive interaction of microelectronic devices and neuronal systems is essential.

    14. Axially Coordinated Porphyrinic Photochromes for Non-destructive Information Processing (pages 347–349)

      T. B. Norsten and N. R. Branda

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<347::AID-ADMA347>3.0.CO;2-9

      Photoinduced ring-opening/ring-closing reactionsmodulate the emission from axially coordinated ruthenium porphyrins in a 1,2-dithienylethene photochrome (see Figure). The changes in phosphorescence intensity can be measured in a non-invasive manner and this system is demonstrated to be non-destructive over several write/erase cycles, thus holding promise for optical data storage applications.

    15. Fabrication of Polyaniline Inverse Opals via Templating Ordered Colloidal Assemblies (pages 350–354)

      D. Wang and F. Caruso

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<350::AID-ADMA350>3.0.CO;2-X

      Attractive new materials for 3D photonic bandgap crystalsare synthesized by polymerizing aniline in the voids between polystyrene (PS) spheres (see Figure). When the PS is depolymerized, a 3D polyaniline (PANI) lattice and channel sizes with inverse opal properties remain. Distances between the pores can be tailored by the choice of the experimental conditions.

    16. Morphology Controlled Energy Transfer in Conjugated Molecular Thin Films (pages 355–358)

      M. Muccini, M. Murgia and F. Biscarini

      Article first published online: 7 MAR 2001 | DOI: 10.1002/1521-4095(200103)13:5<355::AID-ADMA355>3.0.CO;2-D

      In α-sexithienyl (T6) molecular thin filmsthe photoluminescence spectral features can be correlated to precise structural topologies and the nature of the photoluminescence can be controlled. As the thickness of T6 films increases, the topological features evolve progressively from 2D to 3D and coalescence between different domains results in aggregate emission. The Figure shows the photoluminescence spectra of submonolayer and lamellae architectures.