Advanced Materials

Cover image for Vol. 17 Issue 2

January, 2005

Volume 17, Issue 2

Pages 135–250

    1. Cover Picture: A Novel Method for Fixing the Anisotropic Orientation of Dispersed Organic Nanocrystals in a Magnetic Field (Adv. Mater. 2/2005)

      Y. Kaneko, S. Shimada, T. Fukuda, T. Kimura, H. Yokoi, H. Matsuda, T. Onodera, H. Kasai, S. Okada, H. Oikawa and H. Nakanishi

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200590008

      Fixing of the anisotropic orientation of DAST nanocrystals, trans-4-[4-(dimethylamino)]stilbazolium p-toluenesulfonate, a well-known organic second-order nonlinear optical material, is described. The DAST nanocrystals were oriented in an acrylate monomer by an applied magnetic field and then immobilized by UV-curing. The optical anisotropy of the absorption and refractive index of the obtained solid—which is odorless, transparent, heat resistant, insoluble, and soft, like rubber—is shown to be easily controlled by the magnetic field. See also front cover.

    2. Inside Front Cover: Multicolor Pattern Generation in Photonic Bandgap Composites (Adv. Mater. 2/2005)

      P. Jiang, D. W. Smith Jr., J. M. Ballato and S. H. Foulger

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200590009

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      The generation of complex, permanent, multicolor patterns in photonic bandgap films is demonstrated. The procedure allows for the overall spatial control of the reflected color on the surface of a photonic crystal, as well as the ability to define the visible or near-IR response of a patterned region through control of the stop-band wavelength. For example, the attached image presents a 10 mm wide, orange, “tiger paw” insignia templated on a green background. See also inside front cover.

    3. Contents: Adv. Mater. 2/2005 (pages 135–143)

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200590005

    4. Recovered Bandgap Absorption of Single-Walled Carbon Nanotubes in Acetone and Alcohols (pages 147–150)

      A. Cao, S. Talapatra, Y. Choi, R. Vajtai, P. M. Ajayan, A. Filin, P. Persans and A. Rubio

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400113

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      The bandgap optical absorption of single-walled carbon nanotubes (SWNTs) is significantly enhanced by acetone and alcohols. Based on their ability to strip off adsorbates from the nanotube surfaces, these solvents can almost fully recover the optical absorption (see Figure). The distinct absorption recovery can be used to characteristically distinguish a variety of organic solvents, and may find application in chemical sensors.

    5. Protein Micropatterning via Self-Assembly of Nanoparticles (pages 150–153)

      C. Wang and Y. Zhang

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400418

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      Micropatterning of proteins on non-planar surfaces is achieved by immobilization of proteins on silica nanoparticles and self-assembly of the nanoparticles in patterned microwells. The atomic force microscopy (Figure, left, 3 μm × 3 μm) and fluorescence (right) images of protein-coated silica nanoparticles in microwells confirm the viability of this process.

    6. Optically Transparent Composites Reinforced with Networks of Bacterial Nanofibers (pages 153–155)

      H. Yano, J. Sugiyama, A. N. Nakagaito, M. Nogi, T. Matsuura, M. Hikita and K. Handa

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400597

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      Bacterial-cellulose nanofibers obtained from Acetobacter xylinum can reinforce polymer resins while maintaining the transparency of the original resin, even at fiber contents as high as 70 wt.-%, because the nanofibers do not appreciably scatter visible light. The flexible plastic composites (see Figure) reinforced with this renewable resource have thermal expansion coefficients of 6 × 10–6 °C–1, Young's moduli of 20 GPa, and tensile strengths reaching 325 MPa.

    7. A Novel Thermally Stable Spironaphthoxazine and Its Application in Rewritable High Density Optical Data Storage (pages 156–160)

      W. Yuan, L. Sun, H. Tang, Y. Wen, G. Jiang, W. Huang, L. Jiang, Y. Song, H. Tian and D. Zhu

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400953

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      A novel spironaphthoxazine SOFC molecule with a stable ring-opened photomerocyanine form by incorporating a ferrocene moiety to the parent spironaphthoxazine has been synthesized. Two-dimensional luminescence images obtained by confocal microscope employing fluorescence as read-out method (see Figure) and three-dimensional high-density recording using two-photon technology of SOFC-poly(methyl methacrylate) films are demonstrated.

    8. A Novel Method for Fixing the Anisotropic Orientation of Dispersed Organic Nanocrystals in a Magnetic Field (pages 160–163)

      Y. Kaneko, S. Shimada, T. Fukuda, T. Kimura, H. Yokoi, H. Matsuda, T. Onodera, H. Kasai, S. Okada, H. Oikawa and H. Nakanishi

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400275

      Fixing of the anisotropic orientation of DAST nanocrystals, trans-4-[4-(dimethylamino)]stilbazolium p-toluenesulfonate, a well-known organic second-order nonlinear optical material, is described. The DAST nanocrystals were oriented in an acrylate monomer by an applied magnetic field and then immobilized by UV-curing. The optical anisotropy of the absorption and refractive index of the obtained solid—which is odorless, transparent, heat resistant, insoluble, and soft, like rubber—is shown to be easily controlled by the magnetic field. See also front cover.

    9. Highly Photoluminescent CdTe/Poly(N-isopropylacrylamide) Temperature-Sensitive Gels (pages 163–166)

      J. Li, X. Hong, Y. Liu, D. Li, Y.-W. Wang, J.-H. Li, Y.-B. Bai and T.-J. Li

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400448

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      CdTe quantum dots show increased quantum yields when incorporated into a temperature-sensitive poly(N-isopropylacrylamide) hydrogel (see Figure). The fluorescence intensities and maximum emission wavelengths are sensitive to external temperature stimuli and are completely reversible.

    10. Simple Detachment Patterning of Organic Layers and Its Application to Organic Light-Emitting Diodes (pages 166–171)

      J. Choi, D. Kim, P. J. Yoo and H. H. Lee

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400223

      A new detachment patterning technique is applied to the fabrication of a green organic light-emitting diode (OLED). The method (applicable to organic and inorganic substrates) involves simply placing a patterned PDMS mold in conformal contact with the organic layer to be patterned, annealing at a temperature below the glass transition temperature for a period of time, and then removing the mold after cooling to room temperature. The parts of the organic layer in contact with the mold become detached from the substrate upon removing the mold.

    11. Nanotube-Based Ultrafast Electrochromic Display (pages 171–175)

      S. I. Cho, W. J. Kwon, S.-J. Choi, P. Kim, S.-A. Park, J. Kim, S. J. Son, R. Xiao, S.-H. Kim and S. B. Lee

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400499

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      An ultrafast electrochromic display is fabricated based upon well defined nanotube arrays of poly(3,4-ethylenedioxythiophene), PEDOT (see Figure). The thin nature of the nanotube walls (10 – 20 nm) offers a short ion-diffusion distance, which results in an ultrafast switching rate (color-switching time < 10 ms). The arrayed long nanotube structure furnishes strong coloration.

    12. Synthesis of Extremely Small CdSe and Highly Luminescent CdSe/CdS Core–Shell Nanocrystals via a Novel Two-Phase Thermal Approach (pages 176–179)

      D. Pan, Q. Wang, S. Jiang, X. Ji and L. An

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200401425

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      An environmentally harmless method of synthesizing extremely small CdSe and highly luminescent CdSe/CdS core–shell quantum dots (see Figure) with CdSe cores of 1.2–1.5 nm diameter is reported. The CdSe/CdS core–shell quantum dots exhibit 60–80 % quantum yield at room temperature. The emission peak is tunable from 445 to 517 nm (purplish blue to green yellow) by increasing the diameter of the CdSe core and/or the thickness of the CdS shell.

    13. Multicolor Pattern Generation in Photonic Bandgap Composites (pages 179–184)

      P. Jiang, D. W. Smith Jr., J. M. Ballato and S. H. Foulger

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200306680

      Thumbnail image of graphical abstract

      The generation of complex, permanent, multicolor patterns in photonic bandgap films is demonstrated. The procedure allows for the overall spatial control of the reflected color on the surface of a photonic crystal, as well as the ability to define the visible or near-IR response of a patterned region through control of the stop-band wavelength. For example, the attached image presents a 10 mm wide, orange, “tiger paw” insignia templated on a green background. See also inside front cover.

    14. High-Performance Organic Thin-Film Transistors with Solution-Printed Gold Contacts (pages 184–187)

      Y. Wu, Y. Li, B. S. Ong, P. Liu, S. Gardner and B. Chiang

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400690

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      A printable gold precursor composed of functionalized gold nanoparticles in a suitable liquid was used for printing conductive features for organic thin-film transistors (see Figure). A thin-film conductivity of 105 S cm–1 is obtained after annealing at 140 °C under vacuum or 200 °C in ambient conditions. Transistors using source–drain electrodes of this type provide excellent performance, identical to that using vacuum-deposited gold contacts.

    15. Nanowire p–n Heterojunction Diodes Made by Templated Assembly of Multilayer Carbon-Nanotube/Polymer/Semiconductor-Particle Shells around Metal Nanowires (pages 187–192)

      N. I. Kovtyukhova and T. E. Mallouk

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400874

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      Metal nanowires coated with multilayer films of (TiO2/W12O41)3(PAN/SWNT)3PAN (12 nm thick; PAN: Polyaniline; SWNT: single-walled carbon nanotube) are synthesized using different, templated, layer-by-layer assembly techniques. Their I–V characteristics indicate a built-in p–n junction at the TiO2/PAN interface (rectification ratio >120 at 3 V). Films grown on planar substrates have similar thickness, morphology, and electrical properties.

    16. One Volt Organic Transistor (pages 192–196)

      L. A. Majewski, R. Schroeder and M. Grell

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400809

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      Solution-based anodization of titanium can deliver high-capacitance, pinhole-free TiO2 films where the film thickness is controlled by the anodization voltage. In conjunction with the organic semiconductor pentacene, such films can be used to manufacture transistors that operate at less than 1 V (see Figure). Low-cost, disposable devices with low available voltages could take advantage of these flexible organic transistors.

    17. High Efficiency and Quadratic Nonlinear Optical Properties of a Fully Optimized 2D Octupolar Crystal Characterized by Nonlinear Microscopy (pages 196–200)

      V. Le Floc'h, S. Brasselet, J. Zyss, B. R. Cho, S. H. Lee, S.-J. Jeon, M. Cho, K. S. Min and M. P. Suh

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400451

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      An octupolar crystal is produced from octupolar molecules of 1,3,5-tricyano-2,4,6-tris(p-diethylaminostyryl)benzene and its structure is elucidated experimentally using the combined polarization analysis of two-photon fluorescence and second-harmonic generation (SHG). The optimal crystalline packing of the molecules in the crystal (which originates from intermolecular π–π stacking interactions)—see Figure—results in a large SHG efficiency.

    18. Tubular and Twisted Ni–P Fibers Molded from Morphology-Tunable and Recyclable Organic Templates of Hydrogen-Bonded Supramolecular Assemblages (pages 200–205)

      M. Nakagawa, D. Ishii, K. Aoki, T. Seki and T. Iyoda

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400520

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      Morphology-controlled nickel– phosphorus hollow microfibers (see Figure) have been fabricated by electroless plating using hydrogen-bonded fibrous molecular aggregates as novel morphology-tunable and recyclable templates. The inner diameter and the tubular morphology are tunable by simply varying the amphoteric azopyridine carboxylic acids forming the fibrous molecular aggregates.

    19. Wax-Protected Catalyst Microspheres for Efficient Self-Healing Materials (pages 205–208)

      J. D. Rule, E. N. Brown, N. R. Sottos, S. R. White and J. S. Moore

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400607

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      Microspheres of wax containing embedded Grubbs' catalyst are generated by congealing a molten aqueous suspension. Even with a ten-fold reduction in catalyst concentration from previous systems, these microspheres produce unprecedented levels of toughness recovery in a polymeric self-healing material (see Figure). Unlike the previously reported systems, samples healed with the wax microspheres show nonlinear fracture behavior. A protocol that addresses this nonlinearity is employed to measure healing efficiency.

    20. Monoclinic Polymorphs of Bechgaard and Fabre Salts (pages 209–212)

      S. Perruchas, J. Fraxedas, E. Canadell, P. Auban-Senzier and P. Batail

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400852

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      Electrocrystallization where the reactants are confined in two dimensions yields a whole class of unexpected monoclinic polymorphs of the triclinic, prototypical tetramethyltetraselenafulvalene and tetramethyltetrathiafulvalene salts (see Figure). The crystal and electronic structures, as well as the conductivity, of these new and previously known polymorphs of Bechgaard and Fabre salts are described.

    21. Single-Crystalline AlN Nanotubes with Carbon-Layer Coatings on the Outer and Inner Surfaces via a Multiwalled-Carbon-Nanotube-Template-Induced Route (pages 213–217)

      L.-W. Yin, Y. Bando, Y.-C. Zhu, M.-S. Li, C. C. Tang and D. Golberg

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400105

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      Wurtzite-type single-crystalline AlN nanotubes with carbon coatings on the outer and inner surfaces (see Figure) were synthesized in bulk quantities through a substitution carbonitridation chemical process using multiwalled carbon nanotubes as templates. The AlN nanotubes are approximately several micrometers in length, with 45–50 nm diameters and 13 nm-thick walls, and have potential as high-temperature electronic or optoelectronic devices and as field emitters.

    22. Beaded Cobalt Oxide Nanoparticles along Carbon Nanotubes: Towards More Highly Integrated Electronic Devices (pages 217–221)

      L. Fu, Z. Liu, Y. Liu, B. Han, P. Hu, L. Cao and D. Zhu

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400833

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      Nanoparticles strung on nanotubes, like a beaded necklace (see Figure), have been synthesized by a simple low temperature supercritical solution method. That the crystalline spherical Co3O4 nanoparticles on multiwalled carbon nanotubes are a step towards high-density integrated nanometer-scale functional devices is demonstrated by the fabrication of Schottky junction diodes from individual “beaded” nanotubes.

    23. Fabrication of Anodic-Alumina Films with Custom-Designed Arrays of Nanochannels (pages 222–225)

      N.-W. Liu, A. Datta, C.-Y. Liu, C.-Y. Peng, H.-H. Wang and Y.-L. Wang

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400380

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      Focused ion beam (FIB) lithography can be used to selectively close nanochannels in an ordered array on an anodic-alumina film, producing templates with the nanochannels arranged in custom-designed geometries (see Figure). Nanochannel closing can be monitored by in-situ FIB imaging. Nanodevices such as photonic-crystal waveguides could be fabricated using this technique.

    24. Single-Catalyst Confined Growth of ZnS/Si Composite Nanowires (pages 225–230)

      J. Zhan, Y. Bando, J. Hu, T. Sekiguchi and D. Golberg

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400585

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      Side-by-side ZnS/Si composite nanowires have been prepared by tin-catalyst confined growth. Simultaneous thermal evaporation of ZnS and Si powders provides precursor vapors that condense on metallic Sn droplets, resulting in the nucleation and anisotropic growth of composite nanowires made of adjacent ZnS and Si domains (see Figure). The diameters of composite nanowires can reach as low as 15 nm.

    25. Preparation of Functional Nanoporous Silica for Encapsulation of CdSe Nanoparticles (pages 230–233)

      C. D. Ki, T. Emrick and J. Y. Chang

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400184

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      Nanoporous silica–quantum dot composites are produced using an amphiphilic organotrialkoxysilane containing a thermally reversible urethane moiety. Nanoporous silica is formed by co-condensation of the amphiphile and a silicate precursor (see Figure). After heating, the urethane dissociates to form an isocyanate group tethered to the silica. This can be used to make thiol-functionalized nanoporous silica that can encapsulate cadmium selenide nanoparticles.

    26. Surface-Functionalized Nanoparticles with Liquid-Like Behavior (pages 234–237)

      A. B. Bourlinos, R. Herrera, N. Chalkias, D. D. Jiang, Q. Zhang, L. A. Archer and E. P. Giannelis

      Version of Record online: 22 NOV 2004 | DOI: 10.1002/adma.200401060

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      Surface functionalization of silica or maghemite (γ-Fe2O3) nanoparticles with a quaternary ammonium organosilane leads to ionically modified nanoparticles that, depending on the nature of the counterion, exhibit liquid-like behavior in the absence of solvents. Solvent-free nanosalts composed of modified silica nanoparticles (Figure, left) can be used to dissolve and polymerize pyrrole, while nanosalts composed of maghemite nanoparticles (right) can form solvent-free ferrofluids.

    27. Symmetry Control of Polymer Colloidal Monolayers and Crystals by Electrophoretic Deposition on Patterned Surfaces (pages 237–240)

      N. V. Dziomkina, M. A. Hempenius and G. J. Vancso

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400830

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      Colloidal crystals with body-centered cubic packing (see Figure) can be fabricated by electrophoretic deposition of charged latex particles onto patterned surfaces. Laser-interference lithography produces SiO2 layers patterned with controlled symmetry that can then be used to control the orientation and symmetry of colloidal monolayers and crystals deposited onto the electrodes.

    28. Formation of β-Ga2O3–TiO2 ‘Nanobarcodes’ from Core–Shell Nanowires (pages 241–245)

      K.-W. Chang and J.-J. Wu

      Version of Record online: 25 JAN 2005 | DOI: 10.1002/adma.200400708

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      Well-aligned core–shell Ga2O3/TiO2 nanowires of high quality are synthesized using a two-stage metal-organic chemical vapor deposition technique. Annealing of the nanowires at high temperatures results in either the formation of Ga2O3–TiO2 ‘nanobarcodes’ (in which the wires have alternating segments of Ga2O3 and TiO2) or Ga2O3 nanowires inlaid with TiO2 nanocrystals, depending on the annealing temperature.

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