Advanced Materials

Cover image for Advanced Materials

October, 2000

Volume 12, Issue 19

Pages 1401–1469

    1. Advanced Functional Materials: A Full-Paper Journal (page 1401)

      P. Gregory, E. Levy and A. Green

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1401::AID-ADMA1401>3.0.CO;2-8

      A full-paper sister journal toAdvanced Materialshas been established. Its name—Advanced Functional Materials—has been chosen to reflect both the spectrum of topics it will cover and its close association with Advanced Materials. Details on this new journal, which will be launched at the beginning of 2001, can be found in the Editorial on page 1401.

    2. Hybrid Inorganic–Organic Mesoporous Silicates—Nanoscopic Reactors Coming of Age (pages 1403–1419)

      A. Stein, B. J. Melde and R. C. Schroden

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1403::AID-ADMA1403>3.0.CO;2-X

      The architecture of porous inorganic solids can be controlled using organic molecules or molecular aggregates as structure directors, space fillers, or templates, as highlighted in this review article. Methods for preparing hybrid inorganic–organic mesoporous silicates are described as well as some of their applications, e.g., catalysis and heavy metal removal (see Figure).

    3. Patterned Microstructure of Sol–Gel Derived Complex Oxides Using Soft Lithography (pages 1421–1424)

      S. Seraji, Y. Wu, N. E. Jewell-Larson, M. J. Forbess, S. J. Limmer, T. P. Chou and G. Cao

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1421::AID-ADMA1421>3.0.CO;2-4

      Direct patterning of complex oxidesis reported here for the first time. Using a combination of soft lithography with sol-gel processing, patterned microstructures of the piezoelectric materials Pb(ZrTi)O3 (see Figure) and Sr2Nb2O7 on silicon substrates were created as model systems. It was found that dense complex oxides with the desired perovskite structures were formed after annealing at 700–800 °C.

    4. Novel Chromogenic Polymer Gel Networks for Hybrid Transparency and Color Control with Temperature (pages 1424–1426)

      A. Seeboth, J. Kriwanek and R. Vetter

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1424::AID-ADMA1424>3.0.CO;2-N

      Control over both color and transparency is reported for the thermochromic materials presented here. Dyes such as Bromothymol Blue (BB) can reversibly change color with temperature when embedded in aqueous polyether/LiCl gel networks. The Figure shows a gel containing BB at room temperature (green, transparent) and at 33 °C (yellow, transparent). At 36 °C the gel becomes milky.

    5. A Soft Lithography Approach to the Fabrication of Nanostructures of Single Crystalline Silicon with Well-Defined Dimensions and Shapes (pages 1426–1430)

      Y. Yin, B. Gates and Y. Xia

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1426::AID-ADMA1426>3.0.CO;2-B

      Silicon nanostructures with well defined shapes and tightly controlled dimensions can be fabricated in relatively large quantities using the soft lithography approach described here. The capability and feasibility of this method are demonstrated by the fabrication of silicon nanowires, nanorods, micrometer-sized rings (see Figure), and connected triangles (see also inside front cover).

    6. Carbon Nanotube Templated Self-Assembly and Thermal Processing of Gold Nanowires (pages 1430–1432)

      S. Fullam, D. Cottell, H. Rensmo and D. Fitzmaurice

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1430::AID-ADMA1430>3.0.CO;2-8

      Gold nanowires have been produced by the self-assembly of gold nanoparticles onto multi-walled carbon nanotubes. The nanotubes were mixed with a suspension of gold nanoparticles, resulting in a decrease in color intensity of the suspension, and indicating binding between the nanotubes and the gold (see Figure). Subsequent heating in air for 2 min gave rise to continuous nanowires up to 10 μm in length (see also cover).

    7. Straight and Smooth GaN Nanowires (pages 1432–1434)

      X. Chen, J. Li, Y. Cao, Y. Lan, H. Li, M. He, C. Wang, Z. Zhang and Z. Qiao

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1432::AID-ADMA1432>3.0.CO;2-X

      Long, straight gallium nitride nanowires, such as those shown in the Figure, are reported to have been grown directly on substrates, without templates, from the reaction of ammonium with metal gallium. Nanoparticle catalysts and directed flow of the carrier gas are shown to be the main factors leading to the quasi-1D growth. GaN nanowires can be used to improve the performance of certain optoelectronic devices.

    8. Novel Method for Solution Growth of Thin Silica Films from Tetraethoxysilane (pages 1434–1437)

      D. L. J. Vossen, M. J. A. de Dood, T. van Dillen, T. Zijlstra, E. van der Drift, A. Polman and A. van Blaaderen

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1434::AID-ADMA1434>3.0.CO;2-L

      The controlled growth of thin films of silica by a wet-chemical method is reported. Based on the same precursors as for the sol-gel process, but under conditions that lead to the growth of silica in solution with nanometer control, the technique is, unlike the sol-gel technique, also suitable for coating features with large aspect ratios (see Figure). Of particular interest for photonics: grown layers can be doped with optically active groups.

    9. Two-Photon Photographic Production of Three-Dimensional Metallic Structures within a Dielectric Matrix (pages 1438–1441)

      P.-W. Wu, W. Cheng, I. B. Martini, B. Dunn, B. J. Schwartz and E. Yablonovitch

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1438::AID-ADMA1438>3.0.CO;2-Y

      Two-photon lithography has been used to create a three-dimensional metallic structure for the first time. A porous gel filled with AgNO3 solution was laser irradiated in a multi-photon process that allowed silver nanocrystals to be written only on the interior of the gel, resulting in the macroscopic three- dimensional spiral shown in the Figure.

    10. A Novel Route for the Preparation of Nanocomposite Magnets (pages 1441–1444)

      X. Zhang, J. Zhang and W. Wang

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1441::AID-ADMA1441>3.0.CO;2-0

      Nanocomposite magnets are of importance because they are expected to provide a very high maximum-energy product. Here is presented a route to α-Fe/Sm2(Fe,Si)17Cx nanocomposite magnets with fine grain size below 10 nm. Annealing amorphous Sm8Fe85-Si2C5 alloy under high pressure gives nanocomposite magnets (see Figure) with significantly increased coercivity and remnant magnetization.

    11. Carbon Nanotube RLC Circuits (pages 1444–1447)

      N. A. Prokudina, E. R. Shishchenko, O.-S. Joo, D. Y. Kim and S. H. Han

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1444::AID-ADMA1444>3.0.CO;2-J

      A new vision of carbon electronics is provided by the discovery reported here of carbon nanotube RLC (resistance–inductance–capacitance) circuits on nickel-sensitized alumina. When carbon nanotubes are deposited on an alumina surface by chemical vapor deposition from hydrocarbons, the electronic character of the nanotube/substrate combination depends on the preparation conditions. With development, this should allow RLC carbon nanotube microcircuits to be designed and deposited on substrates, perhaps even overcoming the difficulty of producing inductors in integrated circuits.

    12. Polymethacrylate–Silica Hybrid Nanoporous Materials: A Bridge Between Inorganic and Polymeric Molecular Sieves (pages 1448–1450)

      Y. Wei, Q. Feng, J. Xu, H. Dong, K.-Y. Qiu, S. A. Jansen, R. Yin and K. K. Ong

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1448::AID-ADMA1448>3.0.CO;2-W

      Mesoporosity combined with organic polymer functionality and hydrophobicity could give rise to promising new materials with applications in host–guest chemistry and biosensor devices. The synthesis of polymer–silica hybrid mesoporous materials with pore sizes of 3–6 nm is described, in which materials with large specific surface areas (∼800 m2 g–1) and pore volumes (∼0.7 cm3 g–1) as well as relatively narrow pore size distributions are produced by a sol-gel reaction in the presence of a non-surfactant template or pore-forming agent, which is subsequently removed by solvent extraction.

    13. Fast Response Photochromic Mesostructures (pages 1450–1454)

      G. Wirnsberger, B. J. Scott, B. F. Chmelka and G. D. Stucky

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1450::AID-ADMA1450>3.0.CO;2-4

      Direct photochromism is observed for the mesostructured host–photochromic guest system reported here. Block-copolymer/silica mesostructures were used as hosts for two photochromic dyes, a spirooxazine and a spiropyran. It is shown that the dyes are incorporated predominantly within the hydrophobic occlusions of the mesostructures (see Figure) and exhibit direct photochromism, with very fast response times.

    14. Molecular Batteries: Harnessing Fe(CN)63– Electroactivity in Hybrid Polyaniline–Hexacyanoferrate Electrodes (pages 1454–1456)

      P. Gómez-Romero and G. Torres-Gómez

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1454::AID-ADMA1454>3.0.CO;2-H

      Hybrid materials useful as electrodes in plastic batteries are investigated by these authors. The electroactive species hexacyanoferrate (HCF) and the conducting organic polymer polyaniline (PAni) are combined to create hybrid materials that show promise as cathode materials in rechargeable lithium batteries. The chemical and electrochemical synthesis of PAni/HCF as well as the material's electrochemical properties are reported. It is demonstrated that this material has not only a high specific charge and efficiency but also good cyclability.

    15. High-Quality Alkyl Monolayers on Silicon Surfaces (pages 1457–1460)

      A. B. Sieval, R. Linke, H. Zuilhof and E. J. R. Sudhölter

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1457::AID-ADMA1457>3.0.CO;2-#

      Covalent attachment of functionalized monolayers onto silicon surfaces (see Figure) is presented here as a strategy for surface modification. The preparation and structure of both unfunctionalized and functionalized alkyl-based monolayers are described, as are potential applications, for example, in the surface passivation of Si solar cells and for photopatterning of silicon surfaces.

    16. Towards Self-Assembling Inorganic Molecular Wires (pages 1461–1463)

      N. Kimizuka

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1461::AID-ADMA1461>3.0.CO;2-X

      Supramolecular assembly of 1D platinum complexes and synthetic amphiphiles (see Figure) is described here as a strategy for producing inorganic nanowires in solution. It is demonstrated that the electronic states of the complex can be tuned either by the use of suitably designed amphiphiles or by varying the metal species incorporated.

    17. Anodes for Direct Oxidation of Dry Hydrocarbons in a Solid-Oxide Fuel Cell (pages 1465–1469)

      R. J. Gorte, S. Park, J. M. Vohs and C. Wang

      Version of Record online: 4 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:19<1465::AID-ADMA1465>3.0.CO;2-9

      Direct oxidation fuel cells are possible using Cu-based anodes.Recent research in this area is highlighted, and a new method for synthesizing thin-electrolyte, anode-supported cells—based on tape casting with graphite pore formers followed by impregnation with aqueous solutions of Cu(NO3)2 and Ce(NO3)3 (see Figure)—is described.

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