Advanced Materials

Cover image for Vol. 15 Issue 10

May, 2003

Volume 15, Issue 10

Pages 755–842

    1. Contents: Adv. Mater. 10/2003 (pages 755–759)

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200390141

    2. Advances in Microporous and Mesoporous Solids—Highlights of Recent Progress (pages 763–775)

      A. Stein

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200300007

      Recent progress in research into micro- and mesoporous materials is presented. Selected examples are provided to illustrate new zeolite structures, porous coordination materials, mesoporous solids with new compositions, controlled morphologies (see Figure), and increased hydrothermal and thermal stabilities, as well as porous solids with structural features that can be dynamically modified. A number of applications are also discussed.

    3. From Water-Soluble CdTe Nanocrystals to Fluorescent Nanocrystal–Polymer Transparent Composites Using Polymerizable Surfactants (pages 777–780)

      H. Zhang, Z. Cui, Y. Wang, K. Zhang, X. Ji, C. Lü, B. Yang and M. Gao

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304521

      Fluorescent CdTe nanocrystal–polymer transparent composites have been fabricated by a combination of aqueous synthesis of nanocrystals, styrene extraction using polymerizable surfactants, and radical polymerization of monomer mixture containing composite nanocrystals. The Figure shows the photoluminescence of transparent CdTe–polymer composites excited by an ultraviolet lamp.

    4. Templated Surface Sol–Gel Synthesis of SiO2 Nanotubes and SiO2-Insulated Metal Nanowires (pages 780–785)

      N.I. Kovtyukhova, T.E. Mallouk and T.S. Mayer

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304701

      Free-standing SiO2 nanotubes have been synthesized by surface sol–gel replication of the pores of alumina membranes. The nanotubes are very flexible (as shown in the Figure) and their walls are smooth and uniformly thick along their length. SiO2-insulated nanowires were also grown, by electroplating gold inside the SiO2-coated pores of the membrane, and their IV characteristics were examined.

    5. A Novel Photochromic Film by Oxidation Polymerization of a Bisbenzothienylethene with Phenol Groups (pages 785–788)

      K. Uchida, A. Takata, M. Saito, A. Murakami, S. Nakamura and M. Irie

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304562

      A photochromic polymer film is prepared by the oxidation polymerization of a diarylethene. The photoreactive conformation is maintained. A pattern can be written on the film using visible light, and upon irradiation with IR light, a non-destructive read-out of the patterned image is carried out. The structural changes resulting from illumination are shown in the Scheme.

    6. Photonic Band Engineering in Opals by Growth of Si/Ge Multilayer Shells (pages 788–792)

      F. García-Santamaría, M. Ibisate, I. Rodríguez, F. Meseguer and C. López

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304866

      Engineering the shape of photonic bands is a desirable aim to study anomalous dispersion effects or gap formation. Accurate control of silicon and germanium growth by chemical vapor deposition within thin silica opals is reported here. Alternate layers of the two semiconductors—which can be selectively removed (see Figure)—allows new freedom in the fabrication of photonic crystals (see also cover).

    7. Large-Diameter Single-Walled Carbon Nanotubes Synthesized by Chemical Vapor Deposition (pages 792–795)

      Q.-H. Yang, S. Bai, J.-L. Sauvajol and J.-B. Bai

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304567

      The effect of diameter on the properties of nanotubes has come a step closer to experimental verification with the CVD synthesis described here of large-diameter single-walled carbon nanotubes (SWNTs). The SWNTs (see Figure) have a preferential orientation, good purity, and average diameter greater than 3 nm. They exist as macroscopic ropes and aggregate into small bundles.

    8. Preparation and Optical Properties of Highly Crystalline, Colloidal, and Size-Controlled Indium Oxide Nanoparticles (pages 795–797)

      W.S. Seo, H.H. Jo, K. Lee and J.T. Park

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304568

      Highly crystalline and monodisperse In2O3 nanoparticles have been prepared by thermal decomposition of In(acac)3 in oleylamine under inert atmosphere. The particle size of In2O3 can be easily manipulated by changing the experimental conditions. A weak size dependence of photoluminescence is also demonstrated. The Figure shows a 3D superlattice of 6 nm diameter nanoparticles.

    9. Low Molecular Weight Gelators with Hexagonal Order in Their Liquid-Crystal Phases and Gel States: 5-Cyano-2-(3,4,5-trialkoxybenzoylamino)tropones (pages 797–800)

      M. Hashimoto, S. Ujiie and A. Mori

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200303996

      5-Cyano-2-(3,4,5-trialkoxybenzoylamino)tropones form hexagonal structures in both liquid-crystalline and gel states. The Figure shows an environmental scanning electron microscopy image of octanol gels. Hydrogen bonding between the tropone carbonyl group and the NH group of troponoid amides plays an important role in flattening the molecules, allowing tighter packing structures and more stable columnar mesophases and gel states.

    10. Organic Light-Emitting Devices Fabricated from Semiconducting Nanospheres (pages 800–804)

      T. Piok, S. Gamerith, C. Gadermaier, H. Plank, F.P. Wenzl, S. Patil, R. Montenegro, T. Kietzke, D. Neher, U. Scherf, K. Landfester and E.J.W. List

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304253

      The fabrication of organic light-emitting devices (OLEDs) from semiconducting polymer nanospheres (SPNs) deposited from aqueous dispersions is described. It is found that the active device layer consists of a homogeneous single layer of light-emitting SPNs. The OLEDs exhibit an electroluminescence onset at the SPN energy gap, which can be attributed to field-enhanced charge-carrier injection at the nanostructured Al cathode.

    11. Benchtop Fabrication of Submicrometer Metal Line and Island Arrays Using Passivative Microcontact Printing and Electroless Plating (pages 804–807)

      C.E. Moran, C. Radloff and N.J. Halas

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304507

      An entirely benchtop method of fabricating long-range, planar arrays of discrete metal structures on glass or SiO2/Si surfaces without the use of e-beam or photolithography, resist masks, or chemical etching is reported. This approach combines microcontact printing and directed electroless plating for the controlled deposition of islands or lines of gold or silver. The Figure shows gold lines ca. 50 nm in height deposited on a pre-patterned glass surface.

    12. High-Efficiency Polymer Light-Emitting Diodes with Stable Saturated Red Emission: Use of Carbazole-Based Copolymer Blends in a Poly(p-phenylenevinylene) Derivative (pages 807–811)

      Y.-H. Niu, J. Huang and Y. Cao

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304619

      High-efficiency red emission is a prerequisite for full-color display applications of light-emitting diodes. The devices reported here—with stable external quantum efficiency up to 3.8 (photons/electron)-%—have a light-emitting layer consisting of a blend of a novel carbazole-based copolymer (see Figure) in MEHPPV, a more conventional conjugated polymer, as host.

    13. On the Replication of Block Copolymer Templates by Poly(dimethylsiloxane) Elastomers (pages 811–814)

      D.H. Kim, Z. Lin, H.-C. Kim, U. Jeong and T.P. Russell

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304581

      Both positive and negative replicas of copolymer arrays are produced using crosslinked poly(dimethylsiloxane). Negative replicas of the nanoscopic features are manufactued by entrapping air within the microdomains. Positive replicas are produced with ∼ 1:1 aspect ratios by the PDMS filling the nanoscopic, cylincrical cavities. The Figure shows an AFM image of a negative replica (size: 2 μm × 2 μm, inset: Fourier transform of image).

    14. Low-Temperature Fabrication of Efficient Porous Titania Photoelectrodes by Hydrothermal Crystallization at the Solid/Gas Interface (pages 814–817)

      D. Zhang, T. Yoshida and H. Minoura

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304561

      Mechanically stable mesoporous nanocrystalline titania thick films can be prepared at low temperature (100 °C) by hydrothermal treatment of an aqueous mixed paste containing nanocrystalline TiO2 powder and Ti salts. The Ti monomers are converted into crystalline TiO2, which acts as a “glue” to chemically connect the TiO2 particles. Highly efficient flexible dye-sensitized solar cells prepared on a conductive plastic film substrate were realized using this method and a conversion efficiency of 2.3 % at AM1.5 was achieved.

    15. Absorption and Emission in Quaterthienyl Thin Films (pages 818–822)

      H. Sun, Z. Zhao, F.C. Spano, D. Beljonne, J. Cornil, Z. Shuai and J.-L. Brédas

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304770

      The salient features in the absorption and emission spectra of αT4 aggregates (see Figure) and films are fully accounted for using a model based on linear exciton–phonon coupling and structural defects. In particular, the Davydov splitting is calculated to be of the order of 1 eV, and the unusually small 0–0 emission intensity is attributed to the high sensitivity of the 0–0 intensity to basal plane structural defects.

    16. Single-Crystalline Scroll-Type Nanotube Arrays of Copper Hydroxide Synthesized at Room Temperature (pages 822–825)

      W. Zhang, X. Wen, S. Yang, Y. Berta and Z.L. Wang

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304840

      A novel nanolayer-rolled tubular structure of Cu(OH)2 has been grown in solution at ambient temperature and pressure. Significantly, the Cu(OH)2 nanotubes are phase-pure single crystallites and are arrayed uniformly on copper substrates (see Figure). The reaction conditions for the fabrication of the nanotube arrays are examined and possible growth mechanisms are discussed.

    17. Cyanide-Bridged CrIII–NiII Superparamagnetic Nanoparticles (pages 826–829)

      L. Catala, T. Gacoin, J.-P. Boilot, É. Rivière, C. Paulsen, E. Lhotel and T. Mallah

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304696

      Using reverse micelles as nanoreactors facilitates the preparation of bimetallic CrIII–NiII cyanide-bridged nanoparticles that behave as superparamagnets with a blocking temperature of 5.5 K. The Figure presents a plot of magnetization vs. field for various temperatures. Redispersion in an organic solution allows the particles to be diluted in a polymer matrix (inset of Figure) leading to a shift of the blocking temperature down to 2 K.

    18. Nanoporous Gold Films Created Using Templates Formed from Self-Assembled Structures of Inorganic–Block Copolymer Micelles (pages 829–831)

      M. Haupt, S. Miller, R. Glass, M. Arnold, R. Sauer, K. Thonke, M. Möller and J.P. Spatz

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304688

      A multistep procedure for creating nanohole-patterned gold films (see Figure) is presented. The steps include the self-assembly of metal-loaded polystyrene-block-poly(2-vinylpyridine) micelles on GaAs substrates, hydrogen gas plasma treatment, directional reactive ion etching, and gold sputtering. The size and separation of holes resemble that of the gold cluster pattern.

    19. Fabrication of Hollow Capsules Based on Hydrogen Bonding (pages 832–835)

      Y. Zhang, Y. Guan, S. Yang, J. Xu and C.C. Han

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304315

      Hydrogen-bonding layer-by-layer self-assembly has been successfully extended from two- to three-dimensional systems, i.e., to layers on spherical particles. Hollow capsules (see Figure) were prepared by subsequent removal of the sacrificial core. The core–shell particles and hollow capsules should find applications in medicine and biology.

    20. High-Brightness Blue Light-Emitting Polymer Diodes via Anode Modification Using a Self-Assembled Monolayer (pages 835–838)

      H. Yan, Q. Huang, J. Cui, J.G.C. Veinot, M.M. Kern and T.J. Marks

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304585

      Device perfomance of a blue-emitting polyfluorene-based single-layer light-emitting diode are considerably enhanced by the inclusion of a self-assembled monolayer (SAM) of a hole-transporting material (see Figure). The SAM of silyl-functionalized triarylamine (TPD-Si2) is inserted between the ITO anode and the active layer, offering improved hole injection, low visible absorption, and high stability.

    21. High-Density, Ordered Ultraviolet Light-Emitting ZnO Nanowire Arrays (pages 838–841)

      C.H. Liu, J.A. Zapien, Y. Yao, X.M. Meng, C.S. Lee, S.S. Fan, Y. Lifshitz and S.T. Lee

      Version of Record online: 16 MAY 2003 | DOI: 10.1002/adma.200304430

      Polycrystalline ZnO nanowires have been grown in anodic aluminum oxide templates using a dry vapor-deposition method. The nanowires have a high aspect ratio and a uniform density of 1010–1011 cm–2 over a large area (∼ 20 mm2). Room-temperature photoluminescence measurements show lasing modes between 381 and 389 nm above a threshold power density of 100 kW/cm2 (see Figure).