Advanced Materials

Cover image for Vol. 18 Issue 14

July, 2006

Volume 18, Issue 14

Pages 1783–1926

    1. Cover Picture: Surfactant-Mediated Generation of Iso-Oriented Dense and Mesoporous Crystalline Metal-Oxide Layers (Adv. Mater. 14/2006)

      T. Brezesinski, M. Groenewolt, N. Pinna, H. Amenitsch, M. Antonietti and B. Smarsly

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200690057

      Ordered mesoporous and dense films of crystallographically oriented metal oxides (e.g. MoO3, see figure and also cover) are obtained by evaporation-induced self-assembly followed by heating. This surfactant-directed facile methodology works for oxides with anisotropic unit cells, based on the interaction with surfactants during nucleation (soft epitaxy).

    2. Inside Front Cover: Anisotropic Growth of PbSe Nanocrystals on Au–Fe3O4 Hybrid Nanoparticles (Adv. Mater. 14/2006)

      W. Shi, Y. Sahoo, H. Zeng, Y. Ding, M. T. Swihart and P. N. Prasad

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200690058

      PbSe nanorods and branched nanorods are grown using binary Au–Fe3O4 nanoparticles as seeds. PbSe nucleates on the gold portion of the seed particle and grows anisotropically as one or more straight or branched nanorods. Seeding with binary particles has significant advantages over seeding with pure-metal particles. The top TEM images show the different growth morphologies obtained by varying seed-to-precursor ratios and the bottom images show PbSe nanorods and branched nanocrystals (see also inside front cover).

  1. Reviews

    1. Top of page
    2. Reviews
    3. Communications
    4. Book Reviews
    1. Nanocasting: A Versatile Strategy for Creating Nanostructured Porous Materials (pages 1793–1805)

      A.-H. Lu and F. Schüth

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200600148

      Thumbnail image of graphical abstract

      The nanocasting pathway from hard templates, a versatile synthetic strategy, has successfully been applied for the creation of porous solids (see figure). The obtained structures can be precisely tailored by selecting a suitable template, precursor, and synthetic conditions, and the resulting materials lend themselves to further, spatially controlled modification.

  2. Communications

    1. Top of page
    2. Reviews
    3. Communications
    4. Book Reviews
    1. Room-Temperature Aqueous Synthesis of Highly Luminescent BaWO4–Polymer Nanohybrids and Their Spontaneous Conversion to Hexagonal WO3 Nanosheets (pages 1807–1811)

      Y. Oaki and H. Imai

      Version of Record online: 21 JUN 2006 | DOI: 10.1002/adma.200600531

      Thumbnail image of graphical abstract

      Enhanced green luminescence is seen in barium tungstate–poly(acrylic acid). This nanohybrid spontaneously forms into h-WO3 nanosheets through a bottom-up approach in aqueous solution around room temperature (see figure). The coordination of electrolytes to the inorganic species can lead to the morphological evolution of crystals and can control the modification of the chemical structure relevant to various optical and magnetic properties.

    2. High-Density Arrays of Germanium Nanowire Photoresistors (pages 1812–1816)

      B. Polyakov, B. Daly, J. Prikulis, V. Lisauskas, B. Vengalis, M. A. Morris, J. D. Holmes and D. Erts

      Version of Record online: 21 JUN 2006 | DOI: 10.1002/adma.200600213

      Thumbnail image of graphical abstract

      The photoresistive properties and dynamics of ordered high-density arrays of germanium nanowire photoresistors is presented. Individual nanowires demonstrate a sufficient photocurrent to be used in the detection of high illumination intensity. The figure illustrates the photoconductivity measurement assembly.

    3. Large-Scale Synthesis of Rings of Bundled Single-Walled Carbon Nanotubes by Floating Chemical Vapor Deposition (pages 1817–1821)

      L. Song, L. J. Ci, L. F. Sun, C. Jin, L. Liu, W. Ma, D. Liu, X. Zhao, S. Luo, Z. Zhang, Y. Xiang, J. Zhou, W. Zhou, Y. Ding, Z. L. Wang and S. Xie

      Version of Record online: 26 JUN 2006 | DOI: 10.1002/adma.200502372

      Thumbnail image of graphical abstract

      Rings of bundled single-walled carbon nanotubes with perfectly toroidal geometries (see figure), are fabricated in high yields by a floating chemical vapor deposition process involving the thermal decomposition of acetylene. The nanotube rings can be grown with varying densities on a wide variety of substrates at relatively low temperatures, which is a significant advantage for nanoelectronics applications.

    4. Covalent Enzyme Immobilization onto Photopolymerized Highly Porous Monoliths (pages 1822–1826)

      S. J. Pierre, J. C. Thies, A. Dureault, N. R. Cameron, J. C. M. van Hest, N. Carette, T. Michon and R. Weberskirch

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200600293

      Thumbnail image of graphical abstract

      Enzymes covalently immobilized on highly porous materials are demonstrated to have very high biocatalytic activity and good recyclability, exemplified by Candida antarctica Lipase B (CAL-B). Polymerized high internal phase emulsions (PolyHIPEs, see figure) are developed for covalent grafting of proteins (enzymes) via the reaction of the protein surface lysine residues with active ester moieties in the monolithic material.

    5. Surfactant-Mediated Generation of Iso-Oriented Dense and Mesoporous Crystalline Metal-Oxide Layers (pages 1827–1831)

      T. Brezesinski, M. Groenewolt, N. Pinna, H. Amenitsch, M. Antonietti and B. Smarsly

      Version of Record online: 26 JUN 2006 | DOI: 10.1002/adma.200600154

      Thumbnail image of graphical abstract

      Ordered mesoporous and dense films of crystallographically oriented metal oxides (e.g. MoO3, see figure and also cover) are obtained by evaporation-induced self-assembly followed by heating. This surfactant-directed facile methodology works for oxides with anisotropic unit cells, based on the interaction with surfactants during nucleation (soft epitaxy).

    6. Porous, Hollow, and Ball-in-Ball Metal Oxide Microspheres: Preparation, Endocytosis, and Cytotoxicity (pages 1832–1837)

      W. H. Suh, A. R. Jang, Y.-H. Suh and K. S. Suslick

      Version of Record online: 27 JUN 2006 | DOI: 10.1002/adma.200600222

      Thumbnail image of graphical abstract

      An inexpensive ultrasonic generator (household humidifier; ultrasonic spray pyrolysis) is used to synthesize porous, hollow, and ball-in-ball metal oxide microspheres (see figure). The morphology and pore size were controlled by the silica to TiIV ratio and silica particle size. With the introduction of transition-metal ions, core/shell-type microspheres can be synthesized in a single-pot synthesis. These nanomaterials are rapidly taken up into the cytoplasm (but not into the nucleus) of macrophages and show very little cell toxicity.

    7. Triple-Helix Scaffolds of Grafted Collagen Reinforced by Al2O3–ZrO2 Nanoparticles (pages 1838–1841)

      Y. Cao, Y. M. Zhou, Y. Shan, H. X. Ju and X. J. Xue

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200600334

      Thumbnail image of graphical abstract

      The triple-helix structure of grafted collagen is reinforced with bimetallic Al2O3–ZrO2 nanoparticles (see figure), thereby significantly improving the mechanical and thermal stability of the polymer matrix. The stability of this hybrid nanocomposite is thought to derive from the chemical bonding between the surface oxygen atoms on the nanoparticles and functional groups on the collagen matrix. The improved and robust collagen bioscaffolds may potentially be useful for bionic and biomedical applications.

    8. Isotropic “Islands” in a Cholesteric “Sea”: Patterned Thermal Expansion for Responsive Surface Topologies (pages 1842–1845)

      M. E. Sousa, D. J. Broer, C. W. M. Bastiaansen, L. B. Freund and G. P. Crawford

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200502733

      Thumbnail image of graphical abstract

      A method to capture ordered and disordered regions in reactive mesogen films to take advantage of the anisotropic thermal properties and fabricate a thermally responsive patterned film is presented. The image shows white-light interferometer images of isotropic cylinders in cholesteric material. The underlying principle phenomenon observed here is well described by a finite-element simulation.

    9. Acellular Synthesis of a Human Enamel-like Microstructure (pages 1846–1851)

      H. Chen, Z. Tang, J. Liu, K. Sun, S.-R. Chang, M. C. Peters, J. F. Mansfield, A. Czajka-Jakubowska and B. H. Clarkson

      Version of Record online: 26 JUN 2006 | DOI: 10.1002/adma.200502401

      Thumbnail image of graphical abstract

      A mild hydrothermal process is used as a direct method to produce synthetic human enamel prism-like structures that are biocompatible with dental pulp stem cells. The rod-like fluorapatite crystals are very similar in chemical composition and in structural dimensions to natural tooth enamel (see figure).

    10. Silica Fibers with Triangular Cross Sections (pages 1852–1856)

      J. Q. Hu, Y. Bando, J. H. Zhan, X. L. Yuan, T. Sekiguchi, C. Z. Li and D. Golberg

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200600082

      Thumbnail image of graphical abstract

      A new interesting growth phenomenon for amorphous materials has been discovered for silica fibers prepared by a Sn-assisted vapor–liquid–solid growth method. The fibers exhibit triangular cross sections (see figure) and are surface decorated with SnO2 nanoparticles, forming SiO2/SnO2 heterostructures. They have a typical length of several tens of micrometers (some may even reach a length of over 100 μm) and a mean diameter of ca. 0.5–2.5 μm.

    11. Surfactant-Assisted Synthesis of Co- and Li-Doped ZnO Nanocrystalline Samples Showing Room-Temperature Ferromagnetism (pages 1857–1860)

      O. D. Jayakumar, I. K. Gopalakrishnan and S. K. Kulshreshtha

      Version of Record online: 21 JUN 2006 | DOI: 10.1002/adma.200502415

      Thumbnail image of graphical abstract

      Robust room-temperature ferromagnetism is shown in Zn0.85Co0.05Li0.10O nanocrystals. The studies show that the RT ferromagnetism observed in the Zn0.85Co0.05Li0.10O samples is intrinsic in nature. The figure illustrates (schematically) the effect of surfactant treatment in activating the ferromagnetism.

    12. Transfer Patterning of Pentacene for Organic Thin-Film Transistors (pages 1861–1864)

      S. Y. Park, T. Kwon and H. H. Lee

      Version of Record online: 14 JUN 2006 | DOI: 10.1002/adma.200600206

      Thumbnail image of graphical abstract

      A simple and economical way of patterning pentacene (see figure) for the fabrication of organic thin-film transistors (TFTs) is described. In this transfer patterning technique a pentacene film deposited on a patterned “rigiflex” mold is transferred to the surface of an insulating gate dielectric. The carrier mobility of such a TFT is shown to be similar to that of a reference device fabricated using a shadow-mask technique.

    13. A Simple Sol–Gel Synthesis of Superconducting MgB2 Nanowires (pages 1865–1868)

      M. Nath and B. A. Parkinson

      Version of Record online: 22 JUN 2006 | DOI: 10.1002/adma.200600122

      Thumbnail image of graphical abstract

      Superconducting MgB2 nanowires have been synthesized in a very high yield by a simple soft-chemical approach combining sol-gel chemistry and pyrolysis techniques (see main image in the figure; scale bar: 10 μm). The long thin nanowires show a superconducting transition temperature, Tc, of ca. 39 K, as shown in the magnetization curve in the inset of the figure.

      Corrected by:

      Correction: A Simple Sol–Gel Synthesis of Superconducting MgB2 Nanowires

      Vol. 18, Issue 19, 2504, Version of Record online: 26 SEP 2006

    14. Hybrid Biocomposites Based on Calcium Phosphate Mineralization of Self-Assembled Supramolecular Hydrogels (pages 1869–1872)

      Z. A. C. Schnepp, R. Gonzalez-McQuire and S. Mann

      Version of Record online: 26 JUN 2006 | DOI: 10.1002/adma.200502545

      Thumbnail image of graphical abstract

      Mineralization of small-molecule-based supramolecular hydrogels with calcium phosphate produces hybrid composites comprising interconnecting networks of calcified nanofilaments (see figure). Viscoelastic hybrid gels that exhibit enhanced thermal stability, stiffness, and critical strain are formed at low mineral contents, whereas extensive mineralization generates hard macroporous replicas of the supramolecular matrix.

    15. The Growth of Zn–Sb Nanowires by Heat Treatment of Zn–Sb Nanoparticles Obtained by Electrodeposition (pages 1873–1876)

      P. Liu, X. Guo, H. Huang, Q. Yang, Y. Tong and G. A. Hope

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200502450

      Thumbnail image of graphical abstract

      Zn–Sb nanowires are prepared by heat treatment of Zn–Sb nanoparticles at 640 °C under an Ar atmosphere. The precursor, Zn–Sb nanoparticles, was obtained by electrodeposition. The length of the nanowires is more than 30 μm and the typical diameter is about 90 nm (see figure). A spinodal decomposition liquid solid mechanism is proposed to explain the Zn–Sb nanowire growth.

    16. A High-Performance Carbon for Supercapacitors Obtained by Carbonization of a Seaweed Biopolymer (pages 1877–1882)

      E. Raymundo-Piñero, F. Leroux and F. Béguin

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200501905

      Thumbnail image of graphical abstract

      An oxygen-rich carbon for supercapacitors has been obtained by one-step carbonization of a natural biopolymer from seaweeds, e.g., sodium alginate. Although the specific surface area of this carbon is very low, it gives a capacitance comparable to the best activated carbons available. Due to its low porosity (see figure), this material has high density and good electrical conductivity, also advantageous for supercapacitor applications.

    17. Synthesis of Thin, Rectangular C60 Nanorods Using m-Xylene as a Shape Controller (pages 1883–1888)

      L. Wang, B. Liu, D. Liu, M. Yao, Y. Hou, S. Yu, T. Cui, D. Li, G. Zou, A. Iwasiewicz and B. Sundqvist

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200502738

      Thumbnail image of graphical abstract

      Thin, rectangular C60 nanorods in face-centered cubic structure are synthesized by using m-xylene as a shape controller. These unusual nanorods (see figure) can easily grow on various substrates. The smallest nanorods have widths smaller than 30 nm. The nanorods are highly crystalline in single phase. A significant expansion of the lattice constant is also found in the C60 nanorods when their widths decrease below about 80 nm.

    18. Anisotropic Growth of PbSe Nanocrystals on Au–Fe3O4 Hybrid Nanoparticles (pages 1889–1894)

      W. Shi, Y. Sahoo, H. Zeng, Y. Ding, M. T. Swihart and P. N. Prasad

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200600685

      Thumbnail image of graphical abstract

      PbSe nanorods and branched nanorods are grown using binary Au–Fe3O4 nanoparticles as seeds. PbSe nucleates on the gold portion of the seed particle and grows anisotropically as one or more straight or branched nanorods. Seeding with binary particles has significant advantages over seeding with pure-metal particles. The top TEM images show the different growth morphologies obtained by varying seed-to-precursor ratios and the bottom images show PbSe nanorods and branched nanocrystals (see also inside front cover).

    19. Ambient Template-Directed Synthesis of Single-Crystalline Alkaline-Earth Metal Fluoride Nanowires (pages 1895–1899)

      Y. Mao, F. Zhang and S. S. Wong

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200600358

      Thumbnail image of graphical abstract

      A facile and mild means of controllably preparing a series of single-crystalline alkaline-earth metal fluoride nanowires of reproducible shape and varying sizes (see figure) using a simple, room-temperature approach has been developed. This approach is based on the use of readily commercially available polycarbonate template membranes. The favorable luminescence properties of the doped nanowires imply their possible incorporation into functional nanoscale devices.

    20. Air-Stable Complementary-like Circuits Based on Organic Ambipolar Transistors (pages 1900–1904)

      T. D. Anthopoulos, S. Setayesh, E. Smits, M. Cölle, E. Cantatore, B. de Boer, P. W. M. Blom and D. M. de Leeuw

      Version of Record online: 27 JUN 2006 | DOI: 10.1002/adma.200502677

      Thumbnail image of graphical abstract

      Air stable complementary-like circuits, such as voltage inverters (see figure) and ring oscillators, are fabricated using ambipolar organic transistors based on a nickel dithiolene derivative. In addition to the complementary-like character of the circuits, the technology is very simple and fully compatible with the process flowchart for state-of-the-art unipolar organic circuits.

    21. Single-Step Fabrication of Nickel Films with Arrayed Macropores and Nanostructured Skeletons (pages 1905–1909)

      X. Zhang, K.-N. Tu, Y.-H. Xie, C.-H. Tung and S. Xu

      Version of Record online: 27 JUN 2006 | DOI: 10.1002/adma.200502155

      Thumbnail image of graphical abstract

      By simple immersion of high-aspect-ratio macroporous silicon in a prepared nickel bath, replication is achieved in a single step via whole nickel displacement over the silicon of pore sidewalls while maintaining the original macroporous structure. The resultant nickel sidewall skeletons are nanocrystalline and nanoporous. The as-formed featured nickel films are able to self-peel from underneath the nonporous silicon base. The figure shows the Ni wall between two pores.

    22. The Role of a “Schottky Barrier” at an Electron-Collection Electrode in Solid-State Dye-Sensitized Solar Cells (pages 1910–1914)

      H. J. Snaith and M. Grätzel

      Version of Record online: 27 JUN 2006 | DOI: 10.1002/adma.200502256

      Thumbnail image of graphical abstract

      Solid-state dye-sensitized solar cells perform in a strictly different manner when tested under monochromatic as opposed to white-light illumination. Without a UV component in the illumination source, a Schottky barrier is present at the anode interface. Data suggest (see figure) that the generation of surface states, under white-light illumination, results in a pinning of the Fermi level in the TiO2 at the anode interface. Improving this contact facilitates significant improvement in the device performance.

    23. Amplified Photochemistry with Slow Photons (pages 1915–1919)

      J. I. L. Chen, G. von Freymann, S. Y. Choi, V. Kitaev and G. A. Ozin

      Version of Record online: 14 JUL 2006 | DOI: 10.1002/adma.200600588

      Thumbnail image of graphical abstract

      Slow photons in photonic crystals are shown to optically amplify the photoactivity of anatase TiO2 in an inverse opal structure. An enhancement in TiO2 absorption as a result of slow photons leads to a larger population of electron–hole pairs and faster degradation of organic molecules. A remarkable twofold enhancement is achieved (see figure) when the energy of the slow photons is optimized with respect to the absorption edge of anatase.

  3. Book Reviews

    1. Top of page
    2. Reviews
    3. Communications
    4. Book Reviews

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