Advanced Materials

Cover image for Vol. 17 Issue 14

July, 2005

Volume 17, Issue 14

Pages 1695–1806

    1. Cover Picture: Programmable Motion and Separation of Single Magnetic Particles on Patterned Magnetic Surfaces (Adv. Mater. 14/2005)

      K. Gunnarsson, P. E. Roy, S. Felton, J. Pihl, P. Svedlindh, S. Berner, H. Lidbaum and S. Oscarsson

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200590072

      Motion of single micrometer-sized magnetic particles on patterned magnetic surfaces is controlled by a rotating magnetic field (see Figure and cover). Patterns of thin-film magnetic elements are tailored to form transport lines. Individual particles are separated by adding junctions to the transport lines. The method can improve existing applications in biotechnology and generate new ones in life sciences.

    2. Inside Front Cover: From Coordination Polymer Macrocrystals to Nanometric Individual Chains (Adv. Mater. 14/2005)

      D. Olea, S. S. Alexandre, P. Amo-Ochoa, A. Guijarro, F. de Jesús, J. M. Soler, P. J. de Pablo, F. Zamora and J. Gómez-Herrero

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200590073

      Isolated single chains of the coordination polymer [Cd(6-MCP)2 · 2H2O]n (6-MCP = 6-mercaptopurinate) (see Figure and inside cover) have been prepared by ultrasonic dispersion, ultracentrifugation, and deposition on a treated mica surface, and their mechanical and electrical properties studied. The observed insulating behaviour of the chains has been confirmed using density functional theory calculations.

    3. Contents: Adv. Mater. 14/2005 (pages 1695–1702)

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200590068

    4. Electroactive Luminescent Self-Assembled Bio-organic Nanowires: Integration of Semiconducting Oligoelectrolytes within Amyloidogenic Proteins (Adv. Mater. 2005, 12, 1466) (page 1703)

      A. Herland, P. Björk, K. P. R. Nilsson, J. D. M. Olsson, P. Åsberg, P. Konradsson, P. Hammarström and O. Inganäs

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200590069

    5. Gate Dielectrics for Organic Field-Effect Transistors: New Opportunities for Organic Electronics (pages 1705–1725)

      A. Facchetti, M.-H. Yoon and T. J. Marks

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200500517

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      Recent design and fabrication advances in gate dielectric materials for organic TFTs (OTFTs, see Figure) are described in this review. After describing OTFT operating principles, materials, and processing requirements for optimizing low-cost organic electronics, three classes of OTFT-compatible dielectrics are reviewed: i) inorganic (high-k), ii) polymeric, and iii) self-assembled mono- and multilayer materials.

    6. Molecular Photoelectrochemical Devices: Supramolecular Incorporation of C60 Molecules into Tailored Holes on Porphyrin-Modified Gold Nanoclusters (pages 1727–1730)

      H. Imahori, A. Fujimoto, S. Kang, H. Hotta, K. Yoshida, T. Umeyama, Y. Matano and S. Isoda

      Article first published online: 12 MAY 2005 | DOI: 10.1002/adma.200401770

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      Organic photovoltaic devices based on supramolecular complexes of porphyrin-modified gold nanoclusters with fullerene molecules are described and their promising photoelectrochemical performance reported. The incorporation of C60 in surface holes on the porphyrin-modified gold nanoclusters (see Figure)—caused by the addition of a short-chain alkanethiol to the porphyrin modification mixture—plays a key role.

    7. Programmable Motion and Separation of Single Magnetic Particles on Patterned Magnetic Surfaces (pages 1730–1734)

      K. Gunnarsson, P. E. Roy, S. Felton, J. Pihl, P. Svedlindh, S. Berner, H. Lidbaum and S. Oscarsson

      Article first published online: 7 JUN 2005 | DOI: 10.1002/adma.200401880

      Thumbnail image of graphical abstract

      Motion of single micrometer-sized magnetic particles on patterned magnetic surfaces is controlled by a rotating magnetic field (see Figure and cover). Patterns of thin-film magnetic elements are tailored to form transport lines. Individual particles are separated by adding junctions to the transport lines. The method can improve existing applications in biotechnology and generate new ones in life sciences.

    8. An Efficient Solid Oxide Fuel Cell Based upon Single-Phase Perovskites (pages 1734–1737)

      S. W. Tao, J. T. S. Irvine and J. A. Kilner

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200402007

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      An all-perovskite solid oxide fuel cell has been achieved using LSCM ((La0.75Sr0.25)0.95Cr0.5Mn0.5O3–δ) as the anode, LSGMCo (La0.8Sr0.2Ga0.8Mg0.15-Co0.05O3–δ) as the electrolyte, and GSC (Gd0.4Sr0.6CoO3–δ) as the cathode (see Figure). The all-perovskite design enhances structural integrity and minimizes interface polarization losses.

    9. Mesoporous Silica Particles as Templates for Preparing Enzyme-Loaded Biocompatible Microcapsules (pages 1737–1741)

      A. Yu, Y. Wang, E. Barlow and F. Caruso

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200402045

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      Following enzyme adsorption within the pores of mesoporous silica template spheres, polypeptide multilayers are assembled on the particles, and the template is dissolved. This yields a high concentration of enzyme in an active state within the microcapsules (microcapsules are shown in the Figure), which can be released upon changing the pH or salt concentration of the dispersion medium.

    10. Electrophoretic Route to Bi2Sr2CaCu2O8+y Films and Microfibers from Superconducting Colloids (pages 1742–1745)

      E.-S. Jang, J.-J. Chang, S.-H. Jeon, Z.-G. Khim and J.-H. Choy

      Article first published online: 12 MAY 2005 | DOI: 10.1002/adma.200401221

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      Superconducting colloids produced by exfoliation of Bi-based compounds with high superconducting transition temperatures (high-Tcs) can be used as precursors to synthesize superconducting films and nanowires by a simple electrophoretic-deposition technique. Organic-salt intercalates of Bi2Sr2CaCu2O8+y, exfoliated by ultrasonication in acetone, can easily be used to coat silver microfibers (see Figure). These results may be significant for high-Tc superconducting film/wire fabrication.

    11. Fabrication of Stable Metal Films on the Surface of Self-Assembled Monolayers (pages 1745–1749)

      Y. Tai, A. Shaporenko, H. Noda, M. Grunze and M. Zharnikov

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200500464

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      A method for the preparation of stable metal films on self-assembled monolayer (SAM) substrates is described. The approach combines the functionalization and two-dimensional polymerization of the monomolecular film (see Figure). It opens the way for fabrication of ultrathin SAM insulation layers, which could be engineered into existent and future electronic and spintronic devices to improve performance. The approach should also work for non-metal adsorbates, e.g., pentacene.

    12. Self-Assembly and Properties of Main-Chain Reversible Polymer Brushes (pages 1749–1753)

      J. Kim, Y. Liu, S. J. Ahn, S. Zauscher, J. M. Karty, Y. Yamanaka and S. L. Craig

      Article first published online: 19 MAY 2005 | DOI: 10.1002/adma.200401355

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      Supramolecular polymer films can be formed by DNA-based reversible polymers on a surface with grafted anchor points (see Figure). The adhesive mechanical properties of the self-assembled polymer brushes have been investigated by atomic force microscopy. Reversible polymer-mediated adhesion is found to be sensitive to surface anchor density and the thermodynamics and conformational flexibility of the monomer in this system.

    13. Peptide Nanotubes: Simple Separation Using Size-Exclusion Columns and Use as Templates for Fabricating One-Dimensional Single Chains of Au Nanoparticles (pages 1753–1757)

      X. Gao, R. Djalali, A. Haboosheh, J. Samson, N. Nuraje and H. Matsui

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200500357

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      Straight single chains of Au nanoparticles have been synthesized using 10 nm diameter peptide nanotubes as templates (see Figure). The 6 nm Au nanoparticles grow in the gaps between the synthetic peptide coating the nanotubes which regulates the size, dispersity, interparticle distance, and crystallinity of the nanoparticles. The use of longer nanotubes results in longer chains.

    14. Sub-10 nm High-Aspect-Ratio Patterning of ZnO Using an Electron Beam (pages 1757–1761)

      M. S. M. Saifullah, K. R. V. Subramanian, D.-J. Kang, D. Anderson, W. T. S. Huck, G. A. C. Jones and M. E. Welland

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200500484

      Thumbnail image of graphical abstract

      An electron-beam-sensitive zinc naphthenate resist is used to pattern ZnO. Features as small as 7 nm and with an aspect ratio of ∼ 9 can be patterned. Size reduction to ∼ 5 nm is observed when these patterns are heat treated to give crystalline ZnO (see Figure). The functionality of ZnO is confirmed via photoluminescence studies.

    15. From Coordination Polymer Macrocrystals to Nanometric Individual Chains (pages 1761–1765)

      D. Olea, S. S. Alexandre, P. Amo-Ochoa, A. Guijarro, F. de Jesús, J. M. Soler, P. J. de Pablo, F. Zamora and J. Gómez-Herrero

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200401687

      Thumbnail image of graphical abstract

      Isolated single chains of the coordination polymer [Cd(6-MCP)2 · 2H2O]n (6-MCP = 6-mercaptopurinate) (see Figure and inside cover) have been prepared by ultrasonic dispersion, ultracentrifugation, and deposition on a treated mica surface, and their mechanical and electrical properties studied. The observed insulating behaviour of the chains has been confirmed using density functional theory calculations.

    16. Controlled Nanoscale Morphology of Hematite (0001) Surfaces Grown by Chemical Vapor Transport (pages 1765–1768)

      M. E. Greene, A. N. Chiaramonti, S. T. Christensen, L. X. Cao, M. J. Bedzyk and M. C. Hersam

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200401459

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      Stable α-Fe2O3 surfaces: A 3D rendering of the controlled nanoscale morphology observed on a hematite (0001) surface is shown in the Figure. This atomically flat surface is characterized by circular depressions with diameters on the order of hundreds of nanometers and depths of 2.2 ± 0.2 Å. At room temperature, the surface is exceptionally stable, with no measured change following storage in air over several months.

    17. Preparation of Exfoliated Polyester/Clay Nanocomposites (pages 1769–1773)

      T.-Y. Tsai, C.-H. Li, C.-H. Chang, W.-H. Cheng, C.-L. Hwang and R.-J. Wu

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200401260

      Thumbnail image of graphical abstract

      Poly(ethylene terephthalate) (PET)/clay nanocomposites are prepared by intercalation of a catalyst precursor and an organic modifier, followed by the polymerization of monomers between the adjacent clay layers. The mechanical properties, thermal deformation temperature, anti-UV-radiation properties, CO2 gas-barrier properties, and clarity of bottles blown from the PET/clay nanocomposites (see Figure) are improved.

    18. Catalyst Metal Selection for Synthesis of Inorganic Nanowires (pages 1773–1777)

      P. Nguyen, H. T. Ng and M. Meyyappan

      Article first published online: 19 MAY 2005 | DOI: 10.1002/adma.200401717

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      Growth of inorganic nanowires mediated by alternatives to gold using a vapor–liquid–solid mechanism is reported. Fifteen metals have been studied as catalysts, with several of them yielding nanowires (see Figure). The nanowire growth density is a function of melting temperature of the catalyst metals, as the catalyst material serves as the soft template for incorporation of the vapor species into the nanowire.

    19. High-Dielectric-Constant Silver–Epoxy Composites as Embedded Dielectrics (pages 1777–1781)

      L. Qi, B. I. Lee, S. Chen, W. D. Samuels and G. J. Exarhos

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200401816

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      The incorporation of organic-coated silver nanoparticles into an epoxy matrix (see Figure, a–f represent increasing Ag content) results in a flexible 0-3 type nanocomposite with a strikingly high dielectric constant (greater than 300). The composite retains the flexibility and other mechanical properties of the polymer matrix, and may be useful in applications where capacitors are embedded into printed circuit boards.

    20. Synthesis and Photoluminescence of SnO2/SiO2 Microrings (pages 1781–1784)

      X. An, G. W. Meng, Q. Wei, X. Zhang, Y. Hao and L. D. Zhang

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200500207

      Thumbnail image of graphical abstract

      A simple two-step heat-treatment process is used to create SnO2/SiO2 microrings. SnO2/SiO2 nanoparticles obtained in the first step are transformed into microrings (see Figure) in the second step owing to their low melting point and a decrease in the surface energy of the system. The SnO2/SiO2 microrings show favorable UV photoluminescence and may be used as UV laser emitters.

    21. A Cobalt-Free Oxygen-Permeable Membrane Based on the Perovskite-Type Oxide Ba0.5Sr0.5Zn0.2Fe0.8O3–δ (pages 1785–1788)

      H. Wang, C. Tablet, A. Feldhoff and J. Caro

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200401608

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      A Zn-containing perovskite structure of composition Ba0.5Sr0.5Zn0.2Fe0.8O3–δ is proposed as an oxygen-transport material with good phase stability at low oxygen partial pressures at temperatures up to 950 °C. The material has been successfully tested in a membrane reactor in the partial oxidation of methane to synthesis gas (see Figure).

    22. Synthesis of g-C3N4 Nanoparticles in Mesoporous Silica Host Matrices (pages 1789–1792)

      M. Groenewolt and M. Antonietti

      Article first published online: 12 MAY 2005 | DOI: 10.1002/adma.200401756

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      Highly crystalline g-C3N4 nanoparticles have been synthesized from molecular precursors via polycondensation, using mesoporous silica with different pore sizes as host matrices. The particles isolated after removal of the host matrix (see Figure) are characterized using electron microscopy and various spectroscopic techniques. Structural and electronic size effects are identified by comparing nanoparticles that are 5, 13, and 60 nm in diameter.

    23. Ring-Sulfonated Poly(thienothiophene) (pages 1792–1795)

      B. Lee, V. Seshadri, H. Palko and G. A. Sotzing

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200500210

      Ring sulfonation of a poly(thienothiophene) produces a stable, low-bandgap (< 1.2 eV), water-processable, intrinsically conductive polymer. The optical properties of the polymer can be easily modified by varying the sulfonation level and optical-bandgap tuning can also be achieved through the use of a polycation. When used as the polyanion in layer-by-layer-assembled films with polyethyleneimine, the optical absorption properties and intensity remain unchanged for seventeen months. Stability combined with an absorption maximum located within the range for peak solar flux could render these polymers as potential dyes for solar-energy conversion applications.

    24. Thickness Dependence of Mobility in Pentacene Thin-Film Transistors (pages 1795–1798)

      R. Ruiz, A. Papadimitratos, A. C. Mayer and G. G. Malliaras

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200402077

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      The field-effect mobility of pentacene transistors saturates when six monolayers of pentacene are deposited on the gate dielectric. This saturation is not caused by the formation of islands, as the early stages of growth have been found to take place in a layer-by-layer fashion, and layer completion continues well past six monolayers (see Figure).

    25. Switchable Charge Traps in Polymer Diodes (pages 1798–1803)

      P. Andersson, N. D. Robinson and M. Berggren

      Article first published online: 12 MAY 2005 | DOI: 10.1002/adma.200400842

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      By matching the electronic energy levels of a photochromic molecule with those of a semiconducting polymer in a solid-state blend, charge traps in the polymer bulk can selectively be controlled through the state of the molecule. The resulting device exhibits traditional diode characteristics and allows for reversible modulation of the current through the device via in-situ charge-trap switching (see Figure).

    26. Book Review: Springer Handbook of Nanotechnology. By Bharat Bhushan (Ed.). (page 1804)

      Mark A. Reed

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200590070

    27. Author Index and Subject Index Adv. Mater. 14/2005 (pages 1805–1806)

      Article first published online: 8 JUL 2005 | DOI: 10.1002/adma.200590071

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