Advanced Materials

Cover image for Advanced Materials

January, 2000

Volume 12, Issue 2

Pages 85–150

    1. Mesostructured Non-Oxidic Solids with Adjustable Worm-hole Shaped Pores: M-Ge-Q (Q=S, Se) Frameworks Based on Tetrahedral [Ge4Q10]4– Clusters (pages 85–91)

      M. Wachhold, K. K. Rangan, S. J. L. Billinge, V. Petkov, J. Heising and M. G. Kanatzidis

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<85::AID-ADMA85>3.0.CO;2-P

      A new class of mesostructured semiconducting materials, M-Ge-Q (Q=S, Se), has been synthesized using aqueous electrostatic supramolecular self-assembly. The pores in these mesostructured materials are adjustable and are filled with surfactant molecules (see Figure) which can be removed by heating in an inert atmosphere without collapse of the framework.

    2. Principle of Low-Energy Electron Beam–Induced Current Imaging for Ferroelectric Thin Films (pages 91–94)

      I. Lubomirsky, T.-Y. Wang, K. Gartsman and O. M. Stafsudd

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<91::AID-ADMA91>3.0.CO;2-A

      Spontaneous polarization in ferroelectric thin films can be measured accurately and at very fine resolution using the new technique presented here—low-energy electron beam–induced current scanning electron microscopy. The Figure is an electron beam–induced current (EBIC) image of a 350 nm LiTaO3 film, revealing non-homogeneous spontaneous polarization across the sample.

    3. Rewritable Full-Color Recording in a Photon Mode (pages 94–97)

      N. Tamaoki, S. Song, M. Moriyama and H. Matsuda

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<94::AID-ADMA94>3.0.CO;2-T

      The recording of stable and reversible full-color images in the photon mode is reported here. The material is composed of the dicholesteryl ester shown in the Figure, which, when mixed with a small amount of an azobenzene derivative known to be photochemically isomerizable, is able to record full-color images (see also cover) in the liquid-crystalline phase (at increased temperature) but not in the solid phase (room temperature), where images are stable for at least a year.

    4. Nanostructured Thin Films of Organic–Organometallic Block Copolymers: One-Step Lithography with Poly(ferrocenylsilanes) by Reactive Ion Etching (pages 98–103)

      R. G. H. Lammertink, M. A. Hempenius, J. E. van den Enk, V. Z.-H. Chan, E. L. Thomas and G. J. Vancso

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<98::AID-ADMA98>3.0.CO;2-5

      The deposition of thin films of inorganic nanoclusters as a route to one-step lithography has been achieved using block copolymers with inherent inorganic (Fe and Si) components. Nanodomains of the organometallic part are resistant to removal during the subsequent O2 etch, which results in well-ordered and separate domains of iron and silicon oxides, as can be seen in the Figure.

    5. Formation of Mesoporous Silica Nanotubes (pages 103–106)

      H.-P. Lin, C.-Y. Mou and S.-B. Liu

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<103::AID-ADMA103>3.0.CO;2-P

      Mesoporous silica ropes and pillar-within-hollow gyroidal spheres with highly ordered nanostructure have been synthesized through acid and ammonia hydrothermal treatment. Along with hierarchical structures, mesoporous tubules and myelin fingers, such as that shown in the Figure, spontaneously form from the silica ropes or on the shell of the hollow gyroidal spheres.

    6. A Facile Nanoparticle Synthesis Within a Polar Polysulfone Active Matrix (pages 106–109)

      A. Weitz, J. Worrall and F. Wudl

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<106::AID-ADMA106>3.0.CO;2-D

      A novel and simple synthesis of semiconducting and metallic nanoparticles is described that involves the in-situ formation of particles in a high dielectric-constant polymeric matrix that stabilizes the nanoparticles and also enables easy processing into films and fibers at ambient conditions. The procedure is applied to an array of different metal and semiconducting particles such as the CuS particles shown in the Figure.

    7. Colloid Crystal Growth under Oscillatory Shear (pages 110–112)

      O. Vickreva, O. Kalinina and E. Kumacheva

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<110::AID-ADMA110>3.0.CO;2-X

      Large-scale, three-dimensionally ordered arrays of colloid particles (see Figure) have been produced by a new method based on vibratory compacting. The settling dispersions are exposed to controlled oscillatory shear while water is simultaneously removed from the system. This approach can be used for the fast preparation of 3D crystalline assemblies of nanoparticles from their concentrated dispersions.

    8. Controlled Precipitation of Dyes into Hollow Polyelectrolyte Capsules Based on Colloids and Biocolloids (pages 112–115)

      G. Sukhorukov, L. Dähne, J. Hartmann, E. Donath and H. Möhwald

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<112::AID-ADMA112>3.0.CO;2-P

      Hollow polyelectrolyte capsules have been recently introduced as a novel type of artificial smart material. Here is reported the successful filling of polyelectrolyte capsules based on human erythrocytes with various dye compounds using a novel method of selective precipitation. Control of surface properties and conditions leads to preferential crystallization in the interior of the capsules, as shown schematically in the Figure.

    9. A New Approach to Obtain Strip-Structured Biepitaxial YBa2Cu3O7–δ Films by Using Ca-Stabilized Zirconia–CaZrO3 Eutectic Substrates (pages 116–119)

      J. Santiso, V. Laukhin, M. Doudkowsky, G. Garcia, A. Figueras, L. A. Angurel, R. I. Merino, J. I. Peña, M. L. Sanjuán and V. M. Orera

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<116::AID-ADMA116>3.0.CO;2-9

      Biepitaxial thin films of the superconductor YBa2Cu3O7–δ (YBCO) have been prepared in a single deposition step using structured eutectic crystals as substrates. A regular alternating strip pattern of grain boundary junctions can be observed that reproduces the substrate pattern (see Figure). The films show an anisotropy of transport properties in the superconducting and normal states.

    10. Supra-Aggregation: Microphase Formation in Complex Fluids (pages 119–123)

      P. André, A. Filankembo, I. Lisiecki, C. Petit, T. Gulik-Krzywicki, B. W. Ninham and M.-P. Pileni

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<119::AID-ADMA119>3.0.CO;2-Y

      Emulsions are not necessarily thermodynamically unstable. Here it is shown that thermodynamically stable states of self-assembled supra-aggregates exist, and that the component ratios and microstructures that form can be predicted quantitatively from elementary arguments. The Figure is a freeze fracture image of one of the phases that forms when copper(II) bis(2-ethylhexyl)sulfosuccinate is mixed with isooctane and water.

    11. Wet Chemical Synthesis of Highly Luminescent HgTe/CdS Core/Shell Nanocrystals (pages 123–125)

      M. T. Harrison, S. V. Kershaw, A. L. Rogach, A. Kornowski, A. Eychmüller and H. Weller

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<123::AID-ADMA123>3.0.CO;2-H

      Very strong, broad photoluminescence (PL) in the near infrared is displayed by colloidal HgTe nanocrystals. However, they are not stable over time—the PL moves to longer wavelengths, accompanied by an apparent drop in the quantum efficiency—which causes concern for the use of these materials in device applications. Here, capping of the HgTe nanocrystals with a layer of CdS, in order to produce a physically stable core/shell heterostructure, is reported. Optical absorption, PL, X-ray diffraction, and high-resolution TEM are used to characterize the resulting HgTe/CdS material.

    12. Large Coercivity and High Remanent Magnetization Organic-Based Magnets (pages 126–130)

      D. K. Rittenberg, K. Sugiura, Y. Sakata, S. Mikami, A. J. Epstein and J. S. Miller

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<126::AID-ADMA126>3.0.CO;2-5

      Anomalously high coercive field magnets with large remanence magnetizations have been prepared from electron-transfer salts of tetracyanoethylene and MnII(porphyrin). These magnets exhibit metamagnetic-like behavior at low temperature but, anomalously, show hysteresis with a large remanent magnetization. Metamagnets that display large coercivity and remanence magnetizations, especially when these values are large, may lead to new technologically important materials.

    13. White Light Emission from Organic LEDs Utilizing Spiro Compounds with High-Temperature Stability (pages 130–133)

      F. Steuber, J. Staudigel, M. Stössel, J. Simmerer, A. Winnacker, H. Spreitzer, F. Weissörtel and J. Salbeck

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<130::AID-ADMA130>3.0.CO;2-P

      Bright white light emission in rubrene-doped organic LEDs has been demonstrated using spiro compounds—such as spiro-TAD, shown in the Figure—with high glass transition temperatures. These materials show high morphological stability for hole transport and emission of blue light, and thus still operate at temperatures well above 100 °C. The devices give a maximum luminance of 11800 cd/m2.

    14. Thienyl(phenyl)iodonium Triflates—Structural, and Linear and Nonlinear Optical Behavior of Hypervalent Iodine Derivatives (pages 133–137)

      R. R. Tykwinski, K. Kamada, D. Bykowski, K. Ohta and R. McDonald

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<133::AID-ADMA133>3.0.CO;2-D

      The investigation of thienyl and bithienyl iodonium saltsas potential nonlinear optical materials is reported. Hypervalent iodine derivatives (see Figure) have been synthesized from the corresponding stannanes, and their structural, electronic, and preliminary nonlinear optical properties examined. UV analysis showed that the iodonium center mediates communication between the pendant aryl and heteroaryl functionalities.

    15. Stochastic Sensing with Protein Pores (pages 139–142)

      H. Bayley, O. Braha and L.-Q. Gu

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<139::AID-ADMA139>3.0.CO;2-Q

      The engineering of transmembrane protein pores is a novel approach to biosensors, especially stochastic sensors, which use currents from single pores. These authors have used the polypeptide staphylococcal α-hemolysin to detect not only metal ions but also organic molecules. The latter were detected with a cyclodextrin-modified protein pore (see Figure) that allowed a series of molecules to be identified and quantified.

    16. Photorefractive Mesogenic Composites (pages 143–146)

      H. Ono, T. Kawamura, N. M. Frias, K. Kitamura, N. Kawatsuki and H. Norisada

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<143::AID-ADMA143>3.0.CO;2-9

      Photorefractive materials are highly efficient nonlinear optical media and are important for holographic materials. These authors have combined photorefractive liquid crystals with a range of polymers, which not only improved the materials' resolution and introduced functional side groups, but also stabilized the alignment of the mesogenic groups after removal of the DC field (see Figure).

    17. Biologically Programmed Nanoparticle Assembly (pages 147–150)

      S. Mann, W. Shenton, M. Li, S. Connolly and D. Fitzmaurice

      Article first published online: 29 DEC 1999 | DOI: 10.1002/(SICI)1521-4095(200001)12:2<147::AID-ADMA147>3.0.CO;2-U

      The use of protein–substrate binding to program the self-assembly of nanoparticle-based structures from aqueous solution is highlighted here. The systems discussed include aqueous dispersions of metal nanoparticles with surface-attached antibodies and bivalent antigens in solution (see Figure), and ferritin-encapsulated metal oxide nanoparticles with surface biotin groups and streptavidin in solution.