Advanced Materials

Cover image for Vol. 17 Issue 16

August, 2005

Volume 17, Issue 16

Pages 1927–2022

    1. Cover Picture: Ductile-to-Brittle Transition in Nanocrystalline Metals (Adv. Mater. 16/2005)

      H. Li and F. Ebrahimi

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200590082

      Fracture in nanocrystalline metals is shown to depend on grain size. If the grain size is large enough, nanocrystalline metals fracture with a similar mechanism to coarse-grained materials—with extensive reduction in area and a ductile mode. Grain sizes below a critical value result in brittle fracture, via the breaking of atomic bonds (see Figure and cover). On the nanoscale, the cracks follow a mainly intergranular path.

    2. Inside Front Cover: Self-Assembled Highly Faceted Wurtzite-Type ZnS Single-Crystalline Nanotubes with Hexagonal Cross-Sections (Adv. Mater. 16/2005)

      L.-W. Yin, Y. Bando, J.-H. Zhan, M.-S. Li and D. Golberg

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200590084

      Highly faceted wurtzite-type ZnS nanotubes with hexagonal cross-sections have been self-assembled via a thermochemistry process. The self-assembled growth along the c-axis is associated with the non-central and polar surfaces of the ZnS structure (see Figure and inside cover). Photoluminescence at room temperature shows a weak blue and a strong green emission band.

    3. Contents: Adv. Mater. 16/2005 (pages 1927–1934)

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200590079

    4. Laser-Induced Second Harmonic Generation Decay in a Langmuir– Blodgett Film: Arresting by Polyelectrolyte Templating (pages 1937–1941)

      M. S. Chandra, M. G. Krishna, H. Mimata, J. Kawamata, T. Nakamura and T. P. Radhakrishnan

      Article first published online: 23 JUN 2005 | DOI: 10.1002/adma.200401981

      Thumbnail image of graphical abstract

      Stabilizing Langmuir–Blodgett (LB) films: Laser irradiation accelerates π dimerization of hemicyanine nonlinear optical chromophores in monolayer LB films and causes degradation of their second harmonic generation capability. The metastability of the film is overcome effectively by polyelectrolyte templating. Nanoscopic characterization (see Figure) of the ultrathin films reveals the impact of the polyelectrolyte.

    5. On-Demand Control of Optoelectronic Coupling in Gold Nanoparticle Arrays (pages 1941–1945)

      F. Seker, P. R. L. Malenfant, M. Larsen, A. Alizadeh, K. Conway, A. M. Kulkarni, G. Goddard and R. Garaas

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200400734

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      Dynamic control of interparticle coupling within a single material comprising gold nanoparticles and poly(N-isopropylacrylamide) has been developed. Core/shell particles with defined shell thicknesses are the building blocks for preparing films of sufficiently high gold nanoparticle density necessary for achieving reversible switching of several optical properties simultaneously: color, transparency, and metallic luster. The polymer-shell architecture has a strong effect on particle and film stability.

    6. Encapsulated Cores: Host-Free Organic Light-Emitting Diodes Based on Solution-Processible Electrophosphorescent Dendrimers (pages 1945–1948)

      S.-C. Lo, T. D. Anthopoulos, E. B. Namdas, P. L. Burn and I. D. W. Samuel

      Article first published online: 30 JUN 2005 | DOI: 10.1002/adma.200500020

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      A solution-processible phosphorescent dendrimer, which has a fac-tris(2-phenylpyridyl)iridium(III) complex at its core and is encapsulated by six first-generation dendrons (see Figure), eliminates luminescence quenching in the solid state. The dendrimer can be used as a host-free light-emitting layer to give highly efficient bilayer dendrimer light-emitting diodes.

    7. Magnetite-Loaded Polymeric Micelles as Ultrasensitive Magnetic-Resonance Probes (pages 1949–1952)

      H. Ai, C. Flask, B. Weinberg, X.-T. Shuai, M. D. Pagel, D. Farrell, J. Duerk and J. Gao

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200401904

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      Increased contrast in magnetic resonance imaging (MRI) is accomplished using polymeric micelles loaded with superparamagnetic iron oxide (SPIO) nanoparticles encapsulated in biocompatible, biodegradable poly(ϵ-caprolactone)-b-poly(ethylene glycol) (PCL-b-PEG) copolymers (see Figure). The loaded micelles show significantly improved T2 relaxivities and remarkable MRI detection sensitivity.

    8. In-Plane Aligned Pb(ZrxTi1–x)O3 Microbelts Fabricated by Near Migration and Restricted Growth (pages 1952–1956)

      W. Gong, J.-F. Li, C.-E Peng, Z. L. Gui and L. T. Li

      Article first published online: 23 JUN 2005 | DOI: 10.1002/adma.200500340

      Thumbnail image of graphical abstract

      Pb(ZrxTi1–x)O3 (PZT) belt-type crystals, 50–150 μm long, 60–300 nm thick, and 1–2 μm wide, have been prepared on SrTiO3 monocrystal wafers using a novel method, where gold nanoparticles on a substrate confine the two-dimensional growth of the PZT. The microbelts formed have good prospects for application in micro/nanoelectromechanical systems and integrated optoelectronics.

    9. Polycrystalline Macro-Domains Formed by Self-Organization of Ferroelectric Grains (pages 1956–1960)

      V. Lyahovitskaya, Y. Feldman, I. Zon, E. Wachtel, I. Lubomirsky and A. L. Roytburd

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200402083

      Thumbnail image of graphical abstract

      Nanometer-sized grains may self-organize into macro-domains in a polycrystal undergoing a structural phase transition. Formation of such macro-domains is a very efficient strain-relieving mechanism, as demonstrated here. The Figure shows a tethered self-supported BaTiO3 film viewed with cross-polarized light, illustrating a large in-plane anisotropy due to the self-organization of ferroelectric grains in curved regions.

    10. Electron Beam Induced Light Emission and Charge Conduction Patterning in ZnO by Using an AlOx Layer (pages 1960–1964)

      K. C. Hui, J. An, X. Y. Zhang, J. B. Xu, J. Y. Dai and H. C. Ong

      Article first published online: 30 JUN 2005 | DOI: 10.1002/adma.200401461

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      The control of local light emission and conductivity in ZnO is reported. The method detailed here can be used to engineer the optical as well as electrical properties of ZnO two-dimensional thin films and one-dimensional nanostructures on the nanometer scale. The Figure shows an engineered nanoribbon with a pre-designed emission pattern.

    11. Fabrication of Silica-Shielded Ga–ZnS Metal–Semiconductor Nanowire Heterojunctions (pages 1964–1969)

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

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200500317

      Thumbnail image of graphical abstract

      Ga–ZnS nanowire heterojunctions, uniformly sheathed with very thin silica nanotubes, are prepared via thermal evaporation of SiO, Ga2O3, and ZnS powder precursors followed by thermochemical reaction. Some nanowires have a single junction (Figure, top), while others have multiple junctions (bottom). The Ga–ZnS interface is particularly sensitive to electron-beam irradiation (EBI), making possible an EBI-driven switch.

    12. Ductile-to-Brittle Transition in Nanocrystalline Metals (pages 1969–1972)

      H. Li and F. Ebrahimi

      Article first published online: 30 JUN 2005 | DOI: 10.1002/adma.200500436

      Thumbnail image of graphical abstract

      Fracture in nanocrystalline metals is shown to depend on grain size. If the grain size is large enough, nanocrystalline metals fracture with a similar mechanism to coarse-grained materials—with extensive reduction in area and a ductile mode. Grain sizes below a critical value result in brittle fracture, via the breaking of atomic bonds (see Figure and cover). On the nanoscale, the cracks follow a mainly intergranular path.

    13. Self-Assembled Highly Faceted Wurtzite-Type ZnS Single-Crystalline Nanotubes with Hexagonal Cross-Sections (pages 1972–1977)

      L.-W. Yin, Y. Bando, J.-H. Zhan, M.-S. Li and D. Golberg

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200401839

      Thumbnail image of graphical abstract

      Highly faceted wurtzite-type ZnS nanotubes with hexagonal cross-sections have been self-assembled via a thermochemistry process. The self-assembled growth along the c-axis is associated with the non-central and polar surfaces of the ZnS structure (see Figure and inside cover). Photoluminescence at room temperature shows a weak blue and a strong green emission band.

    14. Superhydrophobic Aligned Polystyrene Nanotube Films with High Adhesive Force (pages 1977–1981)

      M. Jin, X. Feng, L. Feng, T. Sun, J. Zhai, T. Li and L. Jiang

      Article first published online: 30 JUN 2005 | DOI: 10.1002/adma.200401726

      Thumbnail image of graphical abstract

      The water contact angle of nanostructured polystyrene surfaces can reach as high as 162°, compared with 95° for native polystyrene surfaces, and they possess a high water adhesion force. Surfaces coated with polystyrene nanotubes (see Figure) created using an alumina membrane template mimic the keratinous hairs in a gecko's feet, providing a large surface area for adhesion through van der Waals' forces.

    15. Highly Efficient Blue Electroluminescence from Poly(phenylene ethynylene) via Energy Transfer from a Hole-Transport Matrix (pages 1981–1985)

      C. A. Breen, J. R. Tischler, V. Bulović and T. M. Swager

      Article first published online: 23 JUN 2005 | DOI: 10.1002/adma.200500185

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      Blue poly(phenylene ethynylene) (PPE) electroluminescence (EL, see Figure) is observed in a hybrid organic light-emitting diode (OLED) with Commission Internationale de l'Eclairage coordinates of (x = 0.17; y = 0.20). Energy transfer from a hole-transport host to polystyrene-grafted PPEs is utilized to improve the poor LED characteristics of traditional PPE-based systems.

    16. Single Crystals of ZSM-5/Silicalite Composites (pages 1985–1988)

      M. Miyamoto, T. Kamei, N. Nishiyama, Y. Egashira and K. Ueyama

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200500522

      Thumbnail image of graphical abstract

      Thin layers of silicalite-1 were grown on H-ZSM-5 crystals. Silicalite-1 crystals of < 100 nm formed on the ZSM-5 crystals and grew along the crystal surface (see Figure). The single-crystal-like composite catalyst showed excellent para-selectivity of 99 % in the alkylation of toluene with methanol, and is expected to develop as a new shape-selective catalyst.

    17. Tetrathiafulvalene [FeIII(C2O4)Cl2]: An Organic–Inorganic Hybrid Exhibiting Canted Antiferromagnetism (pages 1988–1991)

      B. Zhang, Z. Wang, H. Fujiwara, H. Kobayashi, M. Kurmoo, K. Inoue, T. Mori, S. Gao, Y. Zhang and D. Zhu

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200500766

      Thumbnail image of graphical abstract

      A new organic–inorganic hybrid, (TTF+)FeIII(C2O4)Cl2, displaying canted antiferromagnetism has been prepared and characterized, where the tetrathiafulvalene (TTF) molecules are face-to-face dimers and the anion is a one-dimensional coordination polymer (see Figure). Due to π–d interactions through short S…Cl and S…O contacts a three-dimensional Néel state is stabilized at the high temperature of 20 K.

    18. Facile Synthesis and Characterization of Luminescent TiO2 Nanocrystals (pages 1991–1995)

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

      Article first published online: 30 JUN 2005 | DOI: 10.1002/adma.200500479

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      A simple, two-phase approach using an autoclave is taken to synthesize high-quality anatase TiO2 nanocrystals with a narrow size distribution (see Figure). The size-tunable luminescence of the TiO2 nanocrystals is dominated by band-edge luminescence at room temperature. The nanocrystals could be readily dispersed in toluene after capping with stearic or oleic acid.

    19. Nanometer-Sized Nickel Hollow Spheres (pages 1995–1999)

      Q. Liu, H. Liu, M. Han, J. Zhu, Y. Liang, Z. Xu and Y. Song

      Article first published online: 30 JUN 2005 | DOI: 10.1002/adma.200500174

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      Hollow nickel spheres of 50–60 nm diameter have different properties from bulk nickel. For example, the authors demonstrate that the spheres exhibit a long-range magnetic-ordering transition at 575 K and enhanced coercivity. The facile synthesis of such spheres by mild hydrothermal redox reaction of nickel dodecylsulfate with NaH2PO2 (see Figure) is described.

    20. Conductive Carbon Nanofiber–Polymer Foam Structures (pages 1999–2003)

      Y. Yang, M. C. Gupta, K. L. Dudley and R. W. Lawrence

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200500615

      Thumbnail image of graphical abstract

      A novel foam structure of carbon nanofiber–polymer composite (see Figure) with improved electrical conductivity and percolation behavior is reported. This foam structure is very promising for use as an effective electromagnetic-interference shielding material owing to its light weight, electrical conduction, and easy processability.

    21. Catalysts from Self-Assembled Organometallic Block Copolymers (pages 2003–2006)

      D. A. Durkee, H. B. Eitouni, E. D. Gomez, M. W. Ellsworth, A. T. Bell and N. P. Balsara

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200500352

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      Heterogeneous catalysts have been prepared by crosslinking the polyisoprene block of a microphase-separated poly(vinylferrocenium triflate-block-isoprene) copolymer. The poly(vinylferrocenium triflate) moieties provide catalytic activity while the polyisoprene block provides the support structure. Reaction rates obtained with the self-assembled heterogeneous catalyst are within experimental error of those obtained with (monomeric) ferrocenium triflate as a homogeneous catalyst.

    22. Stainless-Steel-Net-Supported Zeolite NaA Membrane with High Permeance and High Permselectivity of Oxygen over Nitrogen (pages 2006–2010)

      X. Yin, G. S. Zhu, W. Yang, Y. Li, G. Q. Zhu, R. Xu, J. Sun, S. Qiu and R. R. Xu

      Article first published online: 30 JUN 2005 | DOI: 10.1002/adma.200500270

      Thumbnail image of graphical abstract

      A stainless-steel net is used to support a zeolite NaA membrane synthesized using a ‘seeded-growth' method. The zeolite and stainless-steel net are tightly integrated (see Figure), showing large-scale order and high mechanical stability. High oxygen permeance and high permselectivity for O2 over N2 (about 7) is demonstrated.

    23. A Composite Surfactant Route for the Synthesis of Thermally Stable and Hierarchically Porous Zirconia with a Nanocrystallized Framework (pages 2010–2014)

      H. Chen, J. Gu, J. Shi, Z. Liu, J. Gao, M. Ruan and D. Yan

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200500221

      Thumbnail image of graphical abstract

      A thermally stable, hierarchically porous zirconia material is synthesized using a composite template of block copolymer and surfactant. The zirconia has a high surface area, a nanocrystallized framework, a well-defined one- dimensional macroporous structure, and a very uniform mesopore distribution (see Figure).

    24. Asymmetric Functional Colloids Through Selective Hemisphere Modification (pages 2014–2018)

      M. A. Correa-Duarte, V. Salgueiriño-Maceira, B. Rodríguez-González, L. M. Liz-Marzán, A. Kosiorek, W. Kandulski and M. Giersig

      Article first published online: 30 JUN 2005 | DOI: 10.1002/adma.200500534

      Thumbnail image of graphical abstract

      Core–shell colloids with two well-differentiated sides (see Figure) have been produced by a combination of electron beam evaporation (EBE) and polyelectrolyte-driven layer-by-layer (LbL) assembly. The colloids are patterned with different optical and magnetic functionalities through deposition of silica-coated gold nanoparticles and evaporation of gold and nickel, forming different thin films on opposite hemispheres.

    25. Book Review: Principles of Polymerization. By George Odian. (page 2019)

      Neil R. Cameron

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200590080

    26. Author Index and Subject Index Adv. Mater. 16/2005 (pages 2021–2022)

      Article first published online: 4 AUG 2005 | DOI: 10.1002/adma.200590081

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