Advanced Materials

Cover image for Advanced Materials

June, 2000

Volume 12, Issue 12

Pages 859–920

    1. Chemical and Biological Applications of Porous Silicon Technology (pages 859–869)

      M. P. Stewart and J. M. Buriak

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<859::AID-ADMA859>3.0.CO;2-0

      Bio- and chemical sensing, biomaterials, and in vivo electronics are some of the latest advances for porous silicon (p-Si) discussed in this review. p-Si is extremely versatile owing largely to its well-known luminescence properties (the Figure shows photoluminescence from patterned p-Si), high surface area, and facile synthesis, while recent techniques for “soft” chemical functionalization allow a high level of control over the interfacial characteristics.

    2. Offsetting the Tubule-Forming Tendency of Chiral Diacetylene-Containing Lipids: Planar Strips, Ribbons, and Liposomes from a Diacetylenic Lipid Analog of a Thermophilic Bacterium (pages 871–874)

      G. Wang and R. I. Hollingsworth

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<871::AID-ADMA871>3.0.CO;2-O

      A chiral self-assembled lamellar system based on the membrane lipid structureof thermophilic bacteria is reported. Unlike typical monopolar double chain chiral lipids, which generally form helices and tubules, sheets (see Figure), ribbons, and vesicles are observed. It is shown that the materials are readily polymerized and metallized and that the polymerized materials display an extremely large fluorescence excitation and emission range.

    3. Supramolecular Polymer Materials: Chain Extension of Telechelic Polymers Using a Reactive Hydrogen-Bonding Synthon (pages 874–878)

      B. J. B. Folmer, R. P. Sijbesma, R. M. Versteegen, J. A. J. van der Rijt and E. W. Meijer

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<874::AID-ADMA874>3.0.CO;2-C

      Functionalizing the termini of low-molecular-weight telechelic polymers with strongly associating hydrogen bonding units (see Figure) results in a new set of supramolecular materials, as reported here. These materials possess the unique combination of polymer-like properties at room temperature and monomer-like properties at elevated temperatures.

    4. Nanocrystalline Nickel Nanoparticles (pages 878–883)

      M. P. Zach and R. M. Penner

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<878::AID-ADMA878>3.0.CO;2-X

      A new technique for electrodepositing nanocrystalline nickel particles on graphite surfaces—the H2 coevolution method—is described. It is demonstrated that nickel nanoparticles that are narrowly dispersed in size (see Figure) can be obtained in a controlled manner over the size range 20–600 nm under specified conditions of the deposition time and deposition potential.

    5. Spinel-Si3N4: Multi-Anvil Press Synthesis and Structural Refinement (pages 883–887)

      M. Schwarz, G. Miehe, A. Zerr, E. Kroke, B. T. Poe, H. Fuess and R. Riedel

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<883::AID-ADMA883>3.0.CO;2-C

      The third known polymorph of silicon nitride, which is cubic and was only recently discovered, has been prepared from two further, different precursors—Si2N2(NH) and a-Si3N4—in a high-pressure, high-temperature synthesis using multi-anvil presses. The synthesis and characterization of the products is described, which included a structural determination by Rietveld refinement of powder X-ray diffraction data. Spinel-type c-Si3N4 is significantly harder than the α and β phases and may possibly find applications as an ultrahard material.

    6. Electrochemical Assembly of Ordered Macropores in Gold (pages 888–890)

      J. E. G. J. Wijnhoven, S. J. M. Zevenhuizen, M. A. Hendriks, D. Vanmaekelbergh, J. J. Kelly and W. L. Vos

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<888::AID-ADMA888>3.0.CO;2-T

      Macroporous gold has been prepared by impregnating artificial opals using electrodeposition. Both latex and silica spheres were used to prepare the opal templates. The silica spheres could be removed without damage to the patterned gold, which is subsequently an excellent reflection of the original template. The Figure shows a crystal of air spheres in gold prepared using silica spheres (see also inside front cover).

    7. An Enhanced CVD Approach to Extensive Nanotube Networks with Directionality (pages 890–894)

      N. R. Franklin and H. Dai

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<890::AID-ADMA890>3.0.CO;2-K

      Extensive networks of oriented single-walled carbon nanotubes (SWNTs) suspended on elevated tower structures can be synthesized by the enhanced chemical vapor deposition (CVD) process described in this article (the experimental setup is shown in the Figure). It is demonstrated that high yields of continuous SWNTs with lengths up to 150 μm can be obtained (see also cover).

    8. Novel Bioactive Functionally Graded Coatings on Ti6Al4V (pages 894–898)

      J. M. Gomez-Vega, E. Saiz, A. P. Tomsia, T. Oku, K. Suganuma, G. W. Marshall and S. J. Marshall

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<894::AID-ADMA894>3.0.CO;2-4

      Bioactive glass coatings are very promising for implant materials due to their good adhesion, mechanical stability, and bioactivity. A new family of silicate-based glasses has been prepared and applied to metallic implants using a simple enameling technique. The graded approach used here reduces stress between layers, and preliminary indentation tests (see Figure) indicate a strong glass–metal adhesion.

    9. A CO2 Sensor Based on a Trivalent Ion Conducting Sc1/3Zr2(PO4)3 Solid Electrolyte (pages 898–901)

      S. Tamura, N. Imanaka, M. Kamikawa and G. Adachi

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<898::AID-ADMA898>3.0.CO;2-P

      On-site monitoring and control of CO2 emissions are required in order to effectively combat global warming. For this, mechanically and chemically stable compact sensors that are highly sensitive to CO2 but insensitive to other gas species are desirable. In this article, a compact CO2 sensor based on Sc1/3Zr2(PO4)3 and yttria-stabilized zirconia solid electrolytes is reported that not only shows a high sensitivity but also a high selectivity for CO2, with a rapid and reproducible response. Coupled with its high mechanical strength and chemical stability, this sensor promises to be useful under a wide variety of conditions.

    10. Influence of Aromatic Groups Incorporated in Long-Chain Alkanethiol Self-Assembled Monolayers on Gold (pages 901–905)

      F. Buckel, F. Effenberger, C. Yan, A. Gölzhäuser and M. Grunze

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<901::AID-ADMA901>3.0.CO;2-B

      The effect of aromatic rings on the orientation and packing of SAMs (self-assembled monolayers) on gold is investigated in this paper. Terminally aryl-substituted eicosanethiols and eicosylthiophenols as well as the oligo(arylalkyl) thiol shown in the Figure are examined. It is shown that the tilt angle may be influenced by the incorporation of aryl groups and densely packed, highly ordered SAMs are obtained.

    11. 2,7-Poly(9-fluorenone): A Trap-Free Electron-Injection Material with a High Charge Carrier Mobility for Use in Light-Emitting Diodes (pages 905–908)

      F. Uckert, Y.-H. Tak, K. Müllen and H. Bässler

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<905::AID-ADMA905>3.0.CO;2-W

      Electron-transporting materials are necessary for organic light-emitting diodes (OLEDs) if their efficiency is going to be increased sufficiently for commercial application. Evidence is presented that the novel, electron-deficient polymer 2,7-poly(9-fluorenone), see Figure, has the qualities required of an electron-injection material in multilayer LEDs.

    12. Unexpected Dimerization of Oxidized Fullerene–Oligothiophene–Fullerene Triads (pages 908–911)

      J. J. Apperloo, B. M. W. Langeveld-Voss, J. Knol, J. C. Hummelen and R. A. J. Janssen

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<908::AID-ADMA908>3.0.CO;2-K

      Can bulky fullerene substituents reduce the dimerization tendency of oligothiophene radical cations? These authors prepared the dumbbell-shaped bis-C60-substituted oligothiophene shown in the Figure in order to address this question. Contrary to expectation, the molecules display extensive dimerization, even at room temperature, in remarkable contrast to the corresponding unsubstituted oligothiophenes.

    13. Chemical Fluid Deposition: A Hybrid Technique for Low-Temperature Metallization (pages 913–915)

      D. P. Long, J. M. Blackburn and J. J. Watkins

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<913::AID-ADMA913>3.0.CO;2-#

      Metal deposition from supercritical CO2 combines the advantages of chemical vapor deposition and aqueous plating without the drawbacks of high temperatures and toxic by-products. This general technique exploits the near-liquid densities and gas-like transport properties of the fluid, and has successfully been used to deposit bright, reflective films of Pt, Pd, Au (see Figure), and Rh.

    14. Optical Trapping for the Manipulation of Colloidal Particles (pages 917–920)

      C. Mio and D. W. M. Marr

      Article first published online: 14 JUN 2000 | DOI: 10.1002/1521-4095(200006)12:12<917::AID-ADMA917>3.0.CO;2-K

      The simultaneous positioning of multiple colloidal particles using optical tweezers is described here. It is illustrated that novel structures of very specific design can be constructed on a microscopic scale (see Figure) and that the structure can be locked in by photopolymerization of the surrounding solvent. Such artificially created surfaces may find applications as lithographic masks or diffraction gratings.