Advanced Materials

Cover image for Vol. 17 Issue 17

September, 2005

Volume 17, Issue 17

Pages 2027–2150

    1. Cover Picture: Multilayer Polymer Light-Emitting Diodes: White-Light Emission with High Efficiency (Adv. Mater. 17/2005)

      X. Gong, S. Wang, D. Moses, G. C. Bazan and A. J. Heeger

      Article first published online: 29 AUG 2005 | DOI: 10.1002/adma.200590088

      White-light-emitting polymer diodes containing hole-injection/transport and electron-injection/transport layers have been fabricated by solution processing. Illumination-quality light is obtained from these multilayer, high-performance devices, with stable Commission Internationale d'Eclairage coordinates, stable color temperatures, and stable, high color-rendering indices, which are all close to those of “pure” white light indicated by the dotted oval in the Figure.

    2. Inside Front Cover: Fabrication of Ideally Ordered Nanoporous Alumina Films and Integrated Alumina Nanotubule Arrays by High-Field Anodization (Adv. Mater. 17/2005)

      S.-Z. Chu, K. Wada, S. Inoue, M. Isogai and A. Yasumori

      Article first published online: 29 AUG 2005 | DOI: 10.1002/adma.200590090

      A new and rapid approach to fabricating highly ordered nanoporous alumina films and integrated alumina nanotubule arrays with perfect hexagonal structures (see Figure and inside cover) is described. By using high-field anodization in a sulfuric acid solution, high-quality self-ordered alumina membranes are produced in hours rather than days. This cost-effective approach to large-area ordered nanoporous membranes may find applications in diverse areas of nanotechnology.

    3. Contents: Adv. Mater. 17/2005 (pages 2027–2035)

      Article first published online: 29 AUG 2005 | DOI: 10.1002/adma.200590085

    4. Peptide-Based Nanotubes and Their Applications in Bionanotechnology (pages 2037–2050)

      X. Gao and H. Matsui

      Article first published online: 29 AUG 2005 | DOI: 10.1002/adma.200401849

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      The current status of research into peptide nanotubes is discussed. The configurations of potential nanodevices are illustrated, for example, by means of biological recognition between functionalized protein nanotubes and complementary protein-patterned surfaces (see Figure). Extension of research efforts from pure structural aspects of bionanotubes to successful use in functional device applications is shown.

    5. Multilayer Polymer Light-Emitting Diodes: White-Light Emission with High Efficiency (pages 2053–2058)

      X. Gong, S. Wang, D. Moses, G. C. Bazan and A. J. Heeger

      Article first published online: 12 JUL 2005 | DOI: 10.1002/adma.200500727

      Thumbnail image of graphical abstract

      White-light-emitting polymer diodes containing hole-injection/transport and electron-injection/transport layers have been fabricated by solution processing. Illumination-quality light is obtained from these multilayer, high-performance devices, with stable Commission Internationale d'Eclairage coordinates, stable color temperatures, and stable, high color-rendering indices, which are all close to those of “pure” white light indicated by the dotted oval in the Figure.

    6. Nanoporous Polymer Thin Films via Polyelectrolyte Templating (pages 2058–2062)

      Q. Li, J. F. Quinn and F. Caruso

      Article first published online: 18 JUL 2005 | DOI: 10.1002/adma.200500666

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      Blended polyelectrolyte multilayer films that include a hydrogen-bonding constituent have been used as templates for the preparation of nanoporous polymer thin films. By crosslinking the electrostatic components following layer-by-layer (LbL) deposition and removing the hydrogen-bonding component by pH elevation (see Figure), nanopores in the range 10–50 nm are formed.

    7. Unique Phase-Separation Structures of Block-Copolymer Nanoparticles (pages 2062–2065)

      H. Yabu, T. Higuchi and M. Shimomura

      Article first published online: 29 AUG 2005 | DOI: 10.1002/adma.200500255

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      Block-copolymer nanoparticles with lamellar phase-separation structures (see Figure) have been prepared by a slow-precipitation process. Regular-sized polymer nanoparticles are formed after evaporation of a good solvent from a polymer solution containing a non-volatile poor solvent and a volatile good solvent.

    8. Sterically Mediated Two-Dimensional Architectures in Aggregates of Au Nanoparticles Directed by Phosphorothioate Oligonucleotide-DNA (pages 2066–2070)

      L. Jiang, H. Zhang, J. Zhuang, B. Yang, W. Yang, T. Li and C. Sun

      Article first published online: 26 JUL 2005 | DOI: 10.1002/adma.200402004

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      Sterically mediated aggregation of gold nanoparticles: 13 nm gold nanoparticles can be arranged in a hexagonal, square, trigonal, or linear manner (see Figure) in two-dimensional (2D) aggregates linked by phosphorothioate oligo-DNA (PS oligo-DNA) of different lengths. The steric effect induced by the parallel orientation of the PS oligo-DNA helix on the particle surface is identified to be of vital importance in controlling the 2D architecture of the particles in the aggregates.

    9. Tunable Emission from Doped 1,3,5-Triphenyl-2-pyrazoline Organic Nanoparticles (pages 2070–2073)

      A.-D. Peng, D.-B. Xiao, Y. Ma, W.-S. Yang and J.-N. Yao

      Article first published online: 30 JUN 2005 | DOI: 10.1002/adma.200401989

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      Tunable fluorescence emission from blue to red (see Figure) is exhibited by nanoparticles of 1,3,5-triphenyl-2-pyrazoline (TPP) doped with 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl-aminostyryl)-4H-pyran (DCM); the emission is found to be dependent on the amount of DCM dopant used. Efficient energy transfer is also shown to occur between TPP and DCM molecules.

    10. Laser Oscillation in Monolithic Molecular Single Crystals (pages 2073–2077)

      M. Ichikawa, R. Hibino, M. Inoue, T. Haritani, S. Hotta, K. Araki, T. Koyama and Y. Taniguchi

      Article first published online: 26 JUL 2005 | DOI: 10.1002/adma.200500734

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      Evidence for oscillation in monolithic molecular single crystals of a thiophene/phenylene co-oligomer is reported. The laser oscillations (see Figure) are characterized by naturally formed crystal facet cavities with molecular-scale flatness. The multimode laser oscillation in a Fabry–Pérot resonator is characterized by sharply resolved spectroscopic lines with their full width at half maximum down to only 38 pm. The laser oscillation is characterized by the presence of a well-defined threshold.

    11. White Luminescence from Polymer Thin Films Containing Excited-State Intramolecular Proton-Transfer Dyes (pages 2077–2082)

      S. Kim, J. Seo, H. K. Jung, J.-J. Kim and S. Y. Park

      Article first published online: 29 AUG 2005 | DOI: 10.1002/adma.200401739

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      White-light-emitting electroluminescent devices comprising a simple mixture of green- and orange-light-emitting excited-state intramolecular proton-transfer (ESIPT) dyes in blue-light-emitting PVK films are demonstrated (see Figure). Dye emissions can be combined independently with limited energy transfer by virtue of the unique characteristics of the ESIPT system: UV absorption and differently Stokes' shifted visible emission.

    12. Crosslinked Capsules of Quantum Dots by Interfacial Assembly and Ligand Crosslinking (pages 2082–2086)

      H. Skaff, Y. Lin, R. Tangirala, K. Breitenkamp, A. Böker, T. P. Russell and T. Emrick

      Article first published online: 29 AUG 2005 | DOI: 10.1002/adma.200500587

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      Robust crosslinked capsules are produced from water droplets stabilized by oil/water interfacial assembly of norbornene-functionalized CdSe/ZnS core–shell quantum dots that can be crosslinked by ring-opening metathesis polymerization (see Figure). The mechanical integrity of the capsules is maintained after removal of the interface. An amphiphilic polyethylene glycol-substituted ruthenium benzylidene catalyst proved ideal for this interfacial polymerization.

    13. Dynamic Self-Assembly of the Liquid-Crystalline Smectic A Phase (pages 2086–2091)

      S. K. Prasad, G. G. Nair and G. Hegde

      Article first published online: 26 JUL 2005 | DOI: 10.1002/adma.200500161

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      A photoinduced transition in an azobenzene-containing liquid crystal leads to a phase that does not exist in the thermal cycle. The smectic A phase is induced and stabilized only in the presence of UV light, producing fan-shaped focal conic textures typical of the SmA phase, as observed by polarized-light microscopy (see Figure). This dynamic self-assembly is explained by photoinduced nanophase segregation and a frustrated spin-gas model.

    14. The Fabrication of an Upright-Standing Zinc Oxide Nanosheet for Use in Dye-Sensitized Solar Cells (pages 2091–2094)

      E. Hosono, S. Fujihara, I. Honma and H. Zhou

      Article first published online: 26 JUL 2005 | DOI: 10.1002/adma.200500275

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      Upright-standing nanocrystalline ZnO films, with the c-axis parallel to the substrate, are fabricated by the pyrolysis of films made of upright-standing sheets of layered hydroxide zinc carbonate (LHZC) (see Figure). Dye-sensitized solar cells (DSCs) prepared using the ZnO films possess the highest level of conversion efficiency for 1.5 AM illumination in ZnO DSCs due to the specific morphology of the ZnO electrode.

    15. Chiral Teleinduction in the Formation of a Macromolecular Multistate Chiroptical Redox Switch (pages 2095–2098)

      E. Gomar-Nadal, J. Veciana, C. Rovira and D. B. Amabilino

      Article first published online: 26 JUL 2005 | DOI: 10.1002/adma.200500348

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      A multistate chiroptical macromolecular switch based on the redox behavior of tetrathiafulvalene (TTF) units has been prepared from a chiral TTF functionalized with an isocyanide group. Polymerization takes place diastereoselectively due to an unusually long-range chiral induction, yielding a helical backbone with organized electroactive side groups (see Figure). This organized redox system may lead to applications in molecular devices.

    16. Si Nanowire Bridges in Microtrenches: Integration of Growth into Device Fabrication (pages 2098–2102)

      R. He, D. Gao, R. Fan, A. I. Hochbaum, C. Carraro, R. Maboudian and P. Yang

      Article first published online: 20 APR 2005 | DOI: 10.1002/adma.200401959

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      Silicon nanowire bridges are grown in prefabricated microtrenches on (110) silicon-on-insulator wafers (see Figure). Silicon trenches are used as substrates during growth and probing electrodes after growth. This way, nanowire growth and device fabrication can be achieved simultaneously, providing a simple and rational way to realize nanowire-based integrated circuits.

    17. Photonic Crystals Fabricated Using Patterned Nanorod Arrays (pages 2103–2106)

      X. D. Wang, C. Neff, E. Graugnard, Y. Ding, J. S. King, L. A. Pranger, R. Tannenbaum, Z. L. Wang and C. J. Summers

      Article first published online: 26 JUL 2005 | DOI: 10.1002/adma.200500546

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      By coating patterned and aligned ZnO nanorod arrays with TiO2, a bottom–up process is used to fabricate a 2D photonic crystal (PC). The as-synthesized 2D PC slab shows a highly ordered air-hole array (see Figure) and exhibits a photonic bandgap that agrees reasonably well with the theoretically calculated value.

    18. Three-Dimensional Tungsten Oxide Nanowire Networks (pages 2107–2110)

      J. Zhou, Y. Ding, S. Z. Deng, L. Gong, N. S. Xu and Z. L. Wang

      Article first published online: 29 AUG 2005 | DOI: 10.1002/adma.200500885

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      Large-scale, single-crystalline, cubic-structured tungsten oxide (WO3–δ) nanowire networks (see Figure) have been synthesized by the thermal evaporation of tungsten metal powder in the presence of oxygen. The formation of ordered planar oxygen vacancies is suggested to be the driving mechanism for the formation of these interpenetrative nanowire networks.

    19. Synthesis of PbTe Nanoboxes Using a Solvothermal Technique (pages 2110–2114)

      W. Z. Wang, B. Poudel, D. Z. Wang and Z. F. Ren

      Article first published online: 29 AUG 2005 | DOI: 10.1002/adma.200500514

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      PbTe nanoboxes have been synthesized using a solvothermal route (see Figure). The experimental results show that both surfactant poly(ethylene glycol) and the volume ratio of ethanol to water play key roles in the formation of the nanoboxes. The contrast difference between the darker edges and lighter center indicate that the nanoboxes are hollow. The as-prepared PbTe nanoboxes are single crystals, and a possible formation mechanism is proposed.

    20. Fabrication of Ideally Ordered Nanoporous Alumina Films and Integrated Alumina Nanotubule Arrays by High-Field Anodization (pages 2115–2119)

      S.-Z. Chu, K. Wada, S. Inoue, M. Isogai and A. Yasumori

      Article first published online: 18 JUL 2005 | DOI: 10.1002/adma.200500401

      Thumbnail image of graphical abstract

      A new and rapid approach to fabricating highly ordered nanoporous alumina films and integrated alumina nanotubule arrays with perfect hexagonal structures (see Figure and inside cover) is described. By using high-field anodization in a sulfuric acid solution, high-quality self-ordered alumina membranes are produced in hours rather than days. This cost-effective approach to large-area ordered nanoporous membranes may find applications in diverse areas of nanotechnology.

    21. Synthesis and Upconversion Luminescence of Hexagonal-Phase NaYF4:Yb, Er3+ Phosphors of Controlled Size and Morphology (pages 2119–2123)

      J.-H. Zeng, J. Su, Z.-H. Li, R.-X. Yan and Y.-D. Li

      Article first published online: 30 JUN 2005 | DOI: 10.1002/adma.200402046

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      Green upconversion emission from hexagonal-phase NaYF4:Yb, Er3+ phosphors can be directly observed with the naked eye. Powders with controlled size and morphology can be synthesized in ethanol and show a minimal decrease in luminescence intensity after 24 h (see Figure). The intense upconversion emission suggests good crystallinity of the materials, which may be used in biological labeling.

    22. Smectic Liquid-Crystalline Colloids by Miniemulsion Techniques (pages 2123–2127)

      M. Vennes, R. Zentel, M. Rössle, M. Stepputat and U. Kolb

      Article first published online: 18 JUL 2005 | DOI: 10.1002/adma.200500310

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      The preparation of liquid-crystalline colloids with diameters in the range of about 100 to 300 nm is reported. Different preformed smectic polysiloxanes have been transferred into colloids by a miniemulsion process with ionic surfactants. Microscopy of unstained colloids clearly show the smectic layer structure within them (see Figure) and are prove the model of a microphase separation between mesogens and polysiloxane chains in liquid-crystalline polysiloxanes.

    23. Strain-Sensitive Raman Modes of Carbon Nanotubes in Deflecting Freely Suspended Nanomembranes (pages 2127–2131)

      C. Jiang, H. Ko and V. V. Tsukruk

      Article first published online: 29 AUG 2005 | DOI: 10.1002/adma.200500579

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      Deformational behavior in freely suspended polymer nanomembranes with embedded carbon nanotubes has been investigated by in-situ monitoring of resonance Raman scattering (see Figure). A two-stage deformational process, with bending and buckling of the nanotubes at low deflections followed by along-axis stretching at high deflections, is observed, indicating a very efficient load transfer between the layer-by-layer deposited matrix and the embedded nanotubes.

    24. Fabrication of Crescent-Shaped Optical Antennas (pages 2131–2134)

      J. S. Shumaker-Parry, H. Rochholz and M. Kreiter

      Article first published online: 18 JUL 2005 | DOI: 10.1002/adma.200500063

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      Metal crescent-shaped nanoparticles (see Figure) that are expected to be efficient optical antennas with highly enhanced and localized near-fields are described. The particle-fabrication process combines colloidal templating, metal-film deposition, and ion-beam milling. The crescents exhibit multiple plasmon resonances in the visible and near-infrared that are of the same type as have been proposed for the development of an effective left-handed material.

    25. A Photoswitchable Donor–π-Linker–Acceptor System Based on a Modified Hexatriene Backbone (pages 2134–2138)

      B. Wüstenberg and N. R. Branda

      Article first published online: 18 JUL 2005 | DOI: 10.1002/adma.200500441

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      Photoresponsive hexatrienes, in which a donor–π-linker–acceptor motif can be reversibly created and broken (see Figure), are synthesized using a versatile approach. Photoinduced ring closing forces a reversible change in hybridization of one of the carbons connecting the donor to the acceptor group, resulting in the breaking of the linear π-conjugation. One particular derivative has interesting electronic properties of potential use in optoelectronics.

    26. A Method for the Rapid Synthesis of Large Quantities of Metal Oxide Nanowires at Low Temperatures (pages 2138–2142)

      M. Mozetič, U. Cvelbar, M. K. Sunkara and S. Vaddiraju

      Article first published online: 26 JUL 2005 | DOI: 10.1002/adma.200500728

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      Metal foils convert to metal oxide nanowires at ∼50–300 °C when oxidized using weakly ionized, highly dissociated oxygen plasmas in an inductively coupled RF system (see Figure). The mechanism is believed to involve spontaneous nucleation of metal oxide nanocrystals (due to supersaturation of the subsurface layers of the foil with O2) followed by basal attachment (due to limited mobility of the metal at low temperatures), leading to rapid nanowire growth.

    27. Energetic Ionic Liquids from Azido Derivatives of 1,2,4-Triazole (pages 2142–2146)

      H. Xue and J. M. Shreeve

      Article first published online: 29 AUG 2005 | DOI: 10.1002/adma.200500789

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      Energetic ionic liquids with good thermal stabilities, relatively high densities, and high, positive heats of formation are described. Quaternization of azidoalkyl-substituted 1,2,4-triazoles with 4,5-dinitroimidazole or 5-nitrotetrazole (see Figure) result in room-temperature liquids that may be useful in energetic materials/propellant applications.

    28. Enhanced Hole Mobility in Poly- (2-methoxy-5-(2′-ethylhexoxy)-1,4- phenylenevinylene) by Elimination of Nanometer-Sized Domains (Adv. Mater. 2005, 15, 1835) (page 2147)

      A. R. Inigo, C. C. Chang, W. Fann, J. D. White, Y.-S. Huang, U.-S. Jeng, H. S. Sheu, K.-Y. Peng and S.-A. Chen

      Article first published online: 29 AUG 2005 | DOI: 10.1002/adma.200590086

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