Advanced Materials

Cover image for Vol. 14 Issue 15

August, 2002

Volume 14, Issue 15

Pages 1009–1092

    1. Contents: Adv. Mater. 15/2002 (pages 1009–1013)

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1009::AID-ADMA1009>3.0.CO;2-7

    2. Contents: Adv. Funct. Mater. 8/2002 (pages 1015–1017)

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1015::AID-ADMA1015>3.0.CO;2-T

    3. Advanced Materials—From Strength to Strength (pages 1019–1021)

      E. Levy

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1019::AID-ADMA1019>3.0.CO;2-5

      Advanced Materials has come a long way since its modest beginning in 1989 as a “piggy back” journal in Angewandte Chemie. Some of its more recent achievements as well as innovations to foster the further development of the journal are presented in this Editorial. The ways in which the success of a journal can be measured in terms of quality and popularity are also discussed.

    4. Observation of Multiple Stop Bands in Photonic Bandgap Structures Doped with Organic Dyes (pages 1023–1027)

      P. Nozar, D. DiDomenico, C. Dionigi, M. Losurdo, M. Muccini and C. Taliani

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1023::AID-ADMA1023>3.0.CO;2-2

      Intensity enhancement of the optical stop band of a periodic quasicrystalline structure is achieved by infiltrating this structure with a suitable dye, as demonstrated for monodisperse polystyrene beads doped with the organic dye Oil Red EGN. A detailed discussion of the optical properties of the system is given in terms of the Bragg and Snell laws, and constraints concerning the refractive index of the dye, LATEX bead diameter, and quasicrystal lattice are extracted. Following some simple geometrical constraints the opening of the photonic bandgap can thus be tuned.

    5. Multi-Colored Photochromic Crystals of Diarylethene Mixtures (pages 1027–1029)

      M. Morimoto, S. Kobatake and M. Irie

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1027::AID-ADMA1027>3.0.CO;2-F

      Multi-colored photochromic single crystals of diarylethene mixtures composed of two compounds have been prepared. Upon irradiation with different wavelengths of light, the colorless crystals turn red, blue, or purple (see Figure), as the two components selectively undergo photochromic reactions. Such multi-colored photochromic crystals have potential for applications in high-density memories and multi-color displays.

    6. Junctions and Networks of SnO Nanoribbons (pages 1029–1032)

      Z.L. Wang and Z.W. Pan

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1029::AID-ADMA1029>3.0.CO;2-3

      Junctions and networks of SnO nanoribbons could be very useful in the fabrication of semiconducting nanosensors and optoelectronic devices. How can these structures be obtained and what are their properties are two questions that are answered here. The role that the Sn particles at the end of each ribbon have in the formation of the networks is also discussed. The Figure shows a double T-junction, which is part of a 2D network of SnO nanoribbons.

    7. White Light Emission Using Triplet Excimers in Electrophosphorescent Organic Light-Emitting Devices (pages 1032–1036)

      B.W. D’Andrade, J. Brooks, V. Adamovich, M.E. Thompson and S.R. Forrest

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1032::AID-ADMA1032>3.0.CO;2-6

      Efficient white light emission from an OLED has been achieved by using only a single emissive dopant, which eliminates differential aging, a problem that occurs in multi-doped devices. The photostability of these phosphorescent dopants (see Figure for a chemical structure of one of the used dopants) is typically quite high, and device failure generally occurs through charged, rather than excitonic states (see also cover).

    8. Metal Nanoparticles, Nanowires, and Contact Electrodes Self-Assembled on Patterned Monolayer Templates—A Bottom-up Chemical Approach (pages 1036–1041)

      S. Hoeppener, R. Maoz, S.R. Cohen, L.F. Chi, H. Fuchs and J. Sagiv

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1036::AID-ADMA1036>3.0.CO;2-J

      Functional metallic nanostructures on silicon substrates are generated by an AFM lithography process: Si coated with alkylsilanes whose CH3 termini get oxidized to COOH groups under the AFM tip acts as a template for self-assembly of a vinyl-terminal alkylsilane layer. Conversion of vinyl to SH groups affords a patterned substrate for binding metals, as verified, e.g., in the gold nanoparticle array shown in the Figure.

    9. Ultralow-k Dielectrics Made by Supercritical Foaming of Thin Polymer Films (pages 1041–1046)

      B. Krause, G.-H. Koops, N.F.A. van der Vegt, M. Wessling, M. Wübbenhorst and J. van Turnhout

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1041::AID-ADMA1041>3.0.CO;2-A

      Ultralow dielectric constants have been achieved for thin porous films of high-Tg polymers. Rapid solid-state polymer expansion applying supercritical carbon dioxide was used to create nanosized cavities in thin films of aromatic polyimides (see Figure). Foamed films with spherical voids less than 10 nm in size as well as multilayered microstructures with interlayer distances of less than 20 nm were made with k values as low as 1.77.

    10. Uniform Boron Nitride Coatings on Silicon Carbide Nanowires (pages 1046–1049)

      C.C. Tang, Y. Bando, T. Sato and K. Kurashima

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1046::AID-ADMA1046>3.0.CO;2-H

      Uniform and smooth BN coatings on SiC nanowires have been obtained by a simple vapor–liquid–solid (VLS) process using Ni as catalyst. SiO and B2O2 gases, simultaneously generated by heating boron and silicon oxide at high temperature, are used as precursors for the VLS growth. The BN-coated semiconductor nanowires could be useful for a wide range of electronic applications.

    11. Fabricating Ordered Two-Dimensional Arrays of Polymer Rings with Submicrometer-Sized Features on Patterned Self-Assembled Monolayers by Dewetting (pages 1049–1053)

      G. Lu, W. Li, J. Yao, G. Zhang, B. Yang and J. Shen

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1049::AID-ADMA1049>3.0.CO;2-#

      Ordered 2D arrays of polystyrene rings on gold surfaces (see Figure) have been fabricated by a combination of microcontact printing, surface-induced condensation of water, and a surface-directed and concentration-controlled dewetting process. The ordered array of rings could be further transferred into the underlying gold substrate by ion etching, using the polymer rings as resists.

    12. Intraframework Metal Ion Adsorption in Ligand-Functionalized Mesoporous Silica (pages 1053–1056)

      K.Z. Hossain and L. Mercier

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1053::AID-ADMA1053>3.0.CO;2-X

      Selective ion adsorption can be carried out with mesostructured metal ion adsorbents in which the ligand groups are included inside the framework walls (see Figure), as is demonstrated here. Another important feature of these materials is that the pore channels are not obstructed by functional groups, thus making it possible to further functionalize the mesostructure or improve the adsorption properties of the adsorbents.

    13. Self-Assembled Nanowire Networks by Deposition of Copper onto Layered-Crystal Surfaces (pages 1056–1061)

      R. Adelung, F. Ernst, A. Scott, M. Tabib-Azar, L. Kipp, M. Skibowski, S. Hollensteiner, E. Spiecker, W. Jäger, S. Gunst, A. Klein, W. Jägermann, V. Zaporojtchenko and F. Faupel

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1056::AID-ADMA1056>3.0.CO;2-F

      Self-assembled copper nanowire networks on layered-crystal surfaces are reported. Obtained from a simple thermal evaporation process in ultra high vacuum, they possess high mechanical strength and a significant elevation over a usually step-edge free surface. These features render Cu-induced nanowire networks particularly accessible to various techniques of microcharacterization such as AFM (see Figure).

    14. Polyfluorenes with Dendron Side Chains as the Active Materials for Polymer Light-Emitting Devices (pages 1061–1064)

      A. Pogantsch, F.P. Wenzl, E.J.W. List, G. Leising, A.C. Grimsdale and K. Müllen

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1061::AID-ADMA1061>3.0.CO;2-6

      Stable blue electroluminescence from polyfluorene light-emitting devices with dendron side chains is demonstrated. A detailed photophysical characterization of the material including photoinduced absorption data is given. Color coordinates of (0.189,0.237) and luminances of more than 380 cd m–2 can be obtained with these devices. The Figure shows the chemical structure of the dendronic polyfluorene.

    15. Oxide Monoliths and Films with Unusual Long-Range Highly Ordered Lamellar Structures (pages 1064–1068)

      A.-W. Xu, Y.-P. Cai, L.-Z. Zhang and J.C. Yu

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1064::AID-ADMA1064>3.0.CO;2-P

      Highly ordered, long-range lamellar structures (see Figure) have been prepared by the sol–gel method using a novel silicone surfactant as a template. The lamellar structures have large lattice constants matching the wavelength of light. The results demonstrate that silicone surfactants with more flexible chains than conventional hydrocarbon surfactants are responsible for the formation of these unusual lamellar oxide mesophases.

    16. Reversible Charging of CdSe Nanocrystals in a Simple Solid-State Device (pages 1068–1071)

      W.-K. Woo, K.T. Shimizu, M.V. Jarosz, R.G. Neuhauser, C.A. Leatherdale, M.A. Rubner and M.G. Bawendi

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1068::AID-ADMA1068>3.0.CO;2-1

      The reversible charging of multiple layers of nanocrystals (NCs) at room temperature has been achieved by using a simple, solid-state device. This reversible charging leads to the possibility of using NCs in optical modulators and in tunable fluorescent or photochromic displays. These structures should also allow systematic studies of the photophysics of charged NCs. The Figure shows the schematic diagram of the NC charging device.

    17. Red Organic Light-Emitting Diodes with a Non-doping Amorphous Red Emitter (pages 1072–1075)

      W.-C. Wu, H.-C. Yeh, L.-H. Chan and C.-T. Chen

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1072::AID-ADMA1072>3.0.CO;2-Z

      An OLED device containing a non-doped pure red light-emitting layer has been achieved. The red OLED is not only bright (∼ 8000 cd/m2) and efficient (2.4 % of external quantum efficiency) but it can also be fabricated easily without concentration-quenching problems. The Figure shows the structure of the non-doping red emitter, which is an amorphous glass molecular material with Tg ∼ 120 °C.

    18. Vapor–Liquid–Solid (VLS) Growth of NiCl2 Nanotubes via Reactive Gas Laser Ablation (pages 1075–1078)

      Y. Rosenfeld Hacohen, R. Popovitz-Biro, E. Grunbaum, Y. Prior and R. Tenne

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1075::AID-ADMA1075>3.0.CO;2-H

      Active laser ablation has been used for the synthesis of NiCl2 nanotubes and fullerene-like nanoparticles (see Figure). Spectroscopic measurements on the structures showed that the NiCl2 layers in the nanotubes were quite perfectly crystalline. The growth is thought to occur via a vapor–liquid–solid mechanism through which many different, surprising shapes have been obtained.

    19. Preparation of Continuous Mesoporous Silica Thin Film on a Porous Tube (pages 1078–1081)

      Y.-S. Kim and S.-M. Yang

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1078::AID-ADMA1078>3.0.CO;2-#

      A crack-free, mesoporous silica thin film (see Figure) has been formed on a macroporous support by prefilling the support pores with poly(vinyl alcohol). The ordered mesoporous silica thin film with narrow pore size distribution was synthesized via a sol–gel route. These thin films have a number of potential applications, including in membrane-based separation processes, as catalysts, and as chemical sensors.

    20. Long-Range Order in Non-porous Hybrid Organic–Inorganic Silicon-Based Materials by Sol–Gel Processing (pages 1081–1084)

      F. Ben, B. Boury and R.J.P. Corriu

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1081::AID-ADMA1081>3.0.CO;2-2

      Hybrid organic–inorganic materials with a long-range order organization (see Figure) have been prepared by a classical sol–gel process. Precursors such as (MeO)3Si–R–Si(OMe)3, R being a thermotropic mesogen-like organic group, have been studied and a self-association process in solution between the molecular units during the formation of the Si–O–Si network is found.

    21. Silver Nanodisks (pages 1084–1086)

      M. Maillard, S. Giorgio and M.-P. Pileni

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1084::AID-ADMA1084>3.0.CO;2-L

      Flat silver nanocrystals have been synthesized by using a soft chemical procedure that involves mixing two reverse micellar solutions. The resulting “nanodisks” display highly anisotropic optical properties attributed to their shape anisotropy. A dark-field TEM image of such a nanodisk, illustrating its single crystal nature, is shown in the Figure.

    22. New Soluble n-Type Conjugated Copolymer for Light-Emitting Diodes (pages 1086–1090)

      C.J. Tonzola, M.M. Alam and S.A. Jenekhe

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1086::AID-ADMA1086>3.0.CO;2-9

      A large improvement in performance of MEH-PPV-based light-emitting diodes has been demonstrated with a new n-type, regioregular, conjugated copolymer containing 3,3′-dialkylbithiophene and bis(phenylquinoline) moieties in the main chain (see Figure). The good solubility of the copolymer in both aprotic organic solvents and protonic acid solvents has enabled the ready fabrication of multilayer light-emitting devices.

    23. Monodisperse Temperature-Sensitive Microcontainers (pages 1090–1092)

      L.S. Zha, Y. Zhang, W.L. Yang and S.K. Fu

      Version of Record online: 29 JUL 2002 | DOI: 10.1002/1521-4095(20020805)14:15<1090::AID-ADMA1090>3.0.CO;2-6

      Thermoresponsive microcontainers (see Figure) based on crosslinked poly(N-isopropylacrylamide) shells undergo a reversible swelling transition upon changing the temperature of the system. This swelling has a considerable influence on the permeability of the shells of these microcontainers, which makes these systems highly attractive for encapsulation and release of biomolecules such as enzymes, proteins, or DNA.