Advanced Materials

Cover image for Advanced Materials

September, 2000

Volume 12, Issue 18

Pages 1313–1383

    1. Deep Impact (page 1313)

      A. Green

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1313::AID-ADMA1313>3.0.CO;2-W

      The latest Impact Factors have recently been released by the Institute for Scientific Information. Advanced Materials continues to lead in the ever-growing category of Materials Science, and has even strengthened its position compared to last year. This and other interesting results are discussed here.

    2. Sensor Functionalities in Self-Assembled Monolayers (pages 1315–1328)

      S. Flink, F. C. J. M. van Veggel and D. N. Reinhoudt

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1315::AID-ADMA1315>3.0.CO;2-K

      Sensors based on self-assembled monolayers (SAMs) are the topic of this article. First an overview of the analytical techniques used for the characterization of monolayers is given. This is followed by details of the use of functional SAMs to study interactions with analytes, for example, the binding of K+ by crown ether derivatives (see Figure).

    3. Fabrication and Characterization of Chirped 3D Photonic Crystals (pages 1329–1332)

      B. Gates and Y. Xia

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1329::AID-ADMA1329>3.0.CO;2-V

      Chirped 3D photonic crystals with stop bands that change continuously (see Figure) or in well-defined steps with position are fabricated here. Two simple methods, involving the assembly of either highly charged polystyrene beads (for continuous stop bands) or electrically neutral polystyrene beads of various sizes (for stepped stop bands), are employed to achieve this.

    4. Direct Conversion of Bulk Materials into MFI Zeolites by a Bulk-Material Dissolution Technique (pages 1332–1335)

      S. Shimizu and H. Hamada

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1332::AID-ADMA1332>3.0.CO;2-Y

      Shape control of zeolitic materials is an important issue because particular shapes would often allow more effective use of the zeolites' micropores and catalytic properties. A technique for the direct conversion of bulk raw materials into MFI zeolites is described in which, for example, if a quartz glass tube is used as the raw material, a tube-shaped zeolite is produced (see the Figure).

    5. A Thiophene Liquid Crystal as a Novel π-Conjugated Dye for Photo-Manipulation of Molecular Alignment (pages 1336–1339)

      H. Zhang, S. Shiino, A. Shishido, A. Kanazawa, O. Tsutsumi, T. Shiono and T. Ikeda

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1336::AID-ADMA1336>3.0.CO;2-A

      DIRE—the dye-induced reorientation effect—occurs when the optical-field-induced reorientation of liquid crystals (LCs) is enhanced by dyes such as the thiophene-based oligomer TR5 shown in the Figure. The synthesis of TR5 is described and its DIRE characterized. It is shown that TR5 provides a new way of controlling LC alignment using low-intensity light (see also cover).

    6. Synthesis and Magnetic Tuning in Superparamagnetic Cobaltocene–Mesoporous Niobium Oxide Composites (pages 1339–1342)

      S. Murray, M. Trudeau and D. M. Antonelli

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1339::AID-ADMA1339>3.0.CO;2-T

      Superparamagnetic behavior in a molecular aggregate is reported here for the first time. Mesoporous niobium oxide loaded with increasing levels of cobaltocene contains varying ratios of CoII to CoIII (see Figure). A subtle increase is seen to lead to a dramatic change in the magnetic properties—from paramagnetic to superparamagnetic, which makes the composites potentially useful in sensor technology.

    7. Synthesis of Large Areas of Highly Oriented, Very Long Silicon Nanowires (pages 1343–1345)

      W. S. Shi, H. Y. Peng, Y. F. Zheng, N. Wang, N. G. Shang, Z. W. Pan, C. S. Lee and S. T. Lee

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1343::AID-ADMA1343>3.0.CO;2-Q

      Nanoscale forms of silicon, a very important electronic material, have interesting properties, but the investigation of Si nanowires, for example, has been hampered by difficulties in producing oriented samples. The authors report here the successful synthesis of large areas of highly oriented, very long (1.5–2 mm) Si nanowires—as shown in the Figure—by thermal evaporation of silicon monoxide.

    8. Synthesis of Gallium Phosphide Nanorods (pages 1346–1348)

      C. Tang, S. Fan, M. Lamy de la Chapelle, H. Dang and P. Li

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1346::AID-ADMA1346>3.0.CO;2-8

      Gallium nitride nanorods have been synthesized, using carbon nanotubes (CNTs) as templates, from gallium oxide in a phosphorus atmosphere. The GaP rods initially produced have diameters similar to the CNT templates, and then epitaxial growth of GaP—shown to occur after template removal, see right-hand part of the Figure—increases the diameter. The nanorods were characterized using TEM, XRD, and SAED.

    9. Polymer-Controlled Growth of CdS Nanowires (pages 1348–1351)

      J. H. Zhan, X. G. Yang, D. W. Wang, S. D. Li, Y. Xie, Y. Xia and Y. Qian

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1348::AID-ADMA1348>3.0.CO;2-X

      Very long crystalline CdS nanowires (see Figure) are fabricated here via a polymer-controlled growth approach that involves distribution of Cd2+ ions in a polyacrylamide matrix followed by treatment with thiourea. It is shown that the polyacrylamide plays an important role in controlling the diameter and increasing the length of these nanowires.

    10. Epitaxial Electrodeposition of Fe3O4 on Single-Crystal Au(111) (pages 1351–1353)

      M. P. Nikiforov, A. A. Vertegel, M. G. Shumsky and J. A. Switzer

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1351::AID-ADMA1351>3.0.CO;2-#

      Magnetite (Fe3O4) is a very promising material for giant magnetoresistance devices.Here, the electrochemical deposition of epitaxial films of Fe3O4 on a Au(111) single crystal is reported (see Figure). No thermal annealing is required to effect crystallization. It is shown that the epitaxial film has a (111) out-of-plane orientation and two types of in-plane orientation.

    11. Photoinduced Cluster Formation of Coumarin-Labeled Organosilicon Micronetworks (pages 1353–1356)

      C. Graf, W. Schärtl and N. Hugenberg

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1353::AID-ADMA1353>3.0.CO;2-O

      UV-induced aggregate formation is reported here for organosilicon micronetworks containing coumarin labels at the particle surface. The nanoparticles become connected via cross-links between coumarin dimers upon UV irradiation—making this technique potentially useful for optical switching—to form individual clusters (see picture, bar indicates 150 nm) whose size can be controlled by irradiation time.

    12. Carbon Nanotubes as Nanoreactors for Boriding Iron Nanowires (pages 1356–1359)

      W. Han, P. Kohler-Redlich, C. Scheu, F. Ernst, M. Rühle, N. Grobert, M. Terrones, H. W. Kroto and D. R. M. Walton

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1356::AID-ADMA1356>3.0.CO;2-6

      Iron boride nanowires are synthesized here by reaction of Fe-filled carbon nanotubes with boron oxide vapor. The thus formed FexB nanowires are encapsulated within the nanotubes (see Figure) and their diameter is approximately that of the starting material, demonstrating that the reaction is confined within the nanotubes. Hence nanotubes can be used as nanoreactors for changing the existing filling from one kind of material to another.

    13. Combustion Synthesis of BaFe12O19 in an External Magnetic Field: Time-Resolved X-ray Diffraction (TRXRD) Studies (pages 1359–1362)

      L. Affleck, M. D. Aguas, Q. A. Pankhurst, I. P. Parkin and W. A. Steer

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1359::AID-ADMA1359>3.0.CO;2-P

      Barium ferrite has a greatly reduced coercivitywhen it is produced (by self-propagating high-temperature synthesis) in the presence of an external magnetic field rather than zero field. This and other significant magnetic field effects, for example, an increase in the speed of the propagation wave, an increased reaction temperature, and a change in the microstructure (see Figure) are reported.

    14. Self-Assembled Diode Junctions Prepared from a Ruthenium Tris(Bipyridyl) Polymer, n-Type TiO2 Nanoparticles, and Graphite Oxide Sheets (pages 1363–1366)

      T. Cassagneau, J. H. Fendler, S. A. Johnson and T. E. Mallouk

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1363::AID-ADMA1363>3.0.CO;2-M

      Thin-film diode structures made by the sequential adsorption of redox-active polymers and semiconductor nanoparticles are explored here. In this work, TiO2 nanoparticles and graphite oxide (GO) nanoplatelets are used as electron- and hole-conducting components, respectively, and a [Ru(bpy)3]2+-containing polymer (RuP, see Figure) is used as the redox-active component. The interconnection of the RuP layers via thin GO sheets allows electroactivity to be observed at positive bias.

    15. Polymer Photovoltaic Devices from Stratified Multilayers of Donor–Acceptor Blends (pages 1367–1370)

      L. C. Chen, D. Godovsky, O. Inganäs, J. C. Hummelen, R. A. J. Janssens, M. Svensson and M. R. Andersson

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1367::AID-ADMA1367>3.0.CO;2-Z

      The conversion efficiencies of organic photovoltaic devices have been improved by a factor of 4–5 by introducing a large surface-area interface between the donor and acceptor layers. Stratified films of a fullerene-based acceptor (see Figure) were spin-coated on top of a donor (MDMO-PPV), forming a diffuse interface with unusual morphology that displayed high energy-conversion efficiencies.

    16. A Sol–Gel-Derived Glass as a Fuel Cell Electrolyte (pages 1370–1372)

      M. Nogami, H. Matsushita, Y. Goto and T. Kasuga

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1370::AID-ADMA1370>3.0.CO;2-1

      A fuel cell electrolyte based on an inorganic glass membrane with a high proton conductivity is described by these authors. The binary glass used (P2O5–SiO2)—prepared by reacting PO(CH3)3 with hydrolyzed Si(OC2H5)4—is demonstrated to not only be useful as a proton conductor in hydrogen fuel cells but also as a hydrogen gas sensor. Because of its good chemical stability and promising performance in H2–O2 fuel cells it is believed that P2O5–SiO2 could replace perfluorinated ionomers as the electrolyte in these cells.

    17. Dendrimers with Attached Helical Peptides (pages 1373–1375)

      N. Higashi, T. Koga and M. Niwa

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1373::AID-ADMA1373>3.0.CO;2-K

      The attachment of peptides to the surface of spherical dendrimers via graft polymerization is described here (see Figure). It is shown that the resulting peptide dendrimers display greatly enhanced helicity compared to non-dendrimer-based analogues. This effect is attributed to aggregation of peptide segments on the dendrimer surface.

    18. A Combinatorial and Informatics Approach to CdS Nanoclusters (pages 1377–1380)

      J. M. Whitling, G. Spreitzer and D. W. Wright

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1377::AID-ADMA1377>3.0.CO;2-X

      The stabilization of size-specific monodisperse CdS nanoclusters has received much attention. However, the development of matrices, e.g., polymers, micelles, zeolites, for this purpose has remained largely empirical. Here a combinatorial and informatics approach to the discovery of ligands for CdS nanocluster stabilization is introduced. It is shown that combinatorially derived peptide and peptomimetic ligands based on phytochelatins can stabilize CdS nanoclusters and that an informatics analysis of the library used yields design parameters critical for obtaining second-generation ligands.

    19. Metal Nanoparticles with a Knack for Molecular Recognition (pages 1381–1383)

      J. Liu, J. Alvarez and A. E. Kaifer

      Version of Record online: 14 SEP 2000 | DOI: 10.1002/1521-4095(200009)12:18<1381::AID-ADMA1381>3.0.CO;2-U

      Cyclodextrin-modified metal nanoparticles (see Figure) illustrate the role that protective organic shells can play in the modulation of the properties of nanoparticles, endowing them with molecular recognition abilities, as highlighted here. These nanocomposite materials are of fundamental interest for the organized self-assembly of metal nanoparticles.

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