Advanced Materials

Cover image for Vol. 23 Issue 11

March 18, 2011

Volume 23, Issue 11

Pages 1304–1413

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Progress Report
    5. Communications
    1. Microfabrication: Conformal Printing of Electrically Small Antennas on Three-Dimensional Surfaces (Adv. Mater. 11/2011) (page 1304)

      Jacob J. Adams, Eric B. Duoss, Thomas F. Malkowski, Michael J. Motala, Bok Yeop Ahn, Ralph G. Nuzzo, Jennifer T. Bernhard and Jennifer A. Lewis

      Article first published online: 14 MAR 2011 | DOI: 10.1002/adma.201190032

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      Jennifer A. Lewis, Jennifer T. Bernhard, and co-workers demonstrate on p. 1335 the conformal printing of electrically conductive meander lines onto hemispherical glass substrates. The bandwidth of these electrically small antennas approaches the fundamental limit for their size. This space-filling design offers nearly an order of magnitude improvement over rudimentary monopole antennas. Cover design by T. Malkowski and R. Durdle (Beckman Institute ITG), University of Illinois.

  2. Contents

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Progress Report
    5. Communications
    1. Contents: (Adv. Mater. 11/2011) (pages 1305–1310)

      Article first published online: 14 MAR 2011 | DOI: 10.1002/adma.201190033

  3. Progress Report

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Progress Report
    5. Communications
    1. Thermoforming of Film-Based Biomedical Microdevices (pages 1311–1329)

      Roman Truckenmüller, Stefan Giselbrecht, Nicolas Rivron, Eric Gottwald, Volker Saile, Albert van den Berg, Matthias Wessling and Clemens van Blitterswijk

      Article first published online: 31 JAN 2011 | DOI: 10.1002/adma.201003538

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      In microthermoforming, thin polymer films are heated to a softened, but still solid state and formed to thin-walled microdevices by three-dimensional stretching. This is in contrast to common polymer microreplication processes where the material is processed in a liquid state. In the present progress report, we review the still young state of the art of microthermoforming technology as well as its first applications.

  4. Communications

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Progress Report
    5. Communications
    1. Toward Hierarchical TiO2 Nanotube Arrays for Efficient Dye-Sensitized Solar Cells (pages 1330–1334)

      Fuwei Zhuge, Jijun Qiu, Xiaomin Li, Xiangdong Gao, Xiaoyan Gan and Weidong Yu

      Article first published online: 27 JAN 2011 | DOI: 10.1002/adma.201003902

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      A step-wise template process is developed for the fabrication of high-aspect-ratio, hierarchical TiO2 nanotube arrays directly on transparent conductive oxides. Significantly enhanced dye loading capability and photoelectrochemical performances are demonstrated in dye-sensitized solar cells with the adoption of a hierarchical nanocrystalline shell.

    2. Conformal Printing of Electrically Small Antennas on Three-Dimensional Surfaces (pages 1335–1340)

      Jacob J. Adams, Eric B. Duoss, Thomas F. Malkowski, Michael J. Motala, Bok Yeop Ahn, Ralph G. Nuzzo, Jennifer T. Bernhard and Jennifer A. Lewis

      Article first published online: 19 JAN 2011 | DOI: 10.1002/adma.201003734

      Thumbnail image of graphical abstract

      Conformal printing of electrically small antennas onto the convex and concave surfaces of hemispherical glass substrates is demonstrated. Their bandwidth approaches the fundamental limit for their size, offering nearly an order of magnitude improvement over rudimentary monopole designs.

    3. Two-Component Polymer Scaffolds for Controlled Three-Dimensional Cell Culture (pages 1341–1345)

      Franziska Klein, Benjamin Richter, Thomas Striebel, Clemens M. Franz, Georg von Freymann, Martin Wegener and Martin Bastmeyer

      Article first published online: 14 JAN 2011 | DOI: 10.1002/adma.201004060

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      Two-component 3D polymer scaffolds with distinct mechanical and protein-binding properties are fabricated using direct laser writing. With this method, full control over the formation of cell adhesion sites and, consequently, cell shape in three dimensions can be achieved.

    4. Local Doping of Silicon Using Nanoimprint Lithography and Molecular Monolayers (pages 1346–1350)

      W. Pim Voorthuijzen, M. Deniz Yilmaz, Wouter J. M. Naber, Jurriaan Huskens and Wilfred G. van der Wiel

      Article first published online: 9 FEB 2011 | DOI: 10.1002/adma.201003625

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      Micrometer-scale monolayer patterns of a phosphorus-containing molecular precursor are fabricated on nearly intrinsic Si(100) using nanoimprint lithography. The patterned sample is protected by a SiO2capping layer applied by electron beam evaporation and subjected to rapid thermal annealing (RTA) to diffuse the phosphorus dopant atoms into the bulk silicon locally.

    5. High-Performance Programmable Memory Devices Based on Co-Doped BaTiO3 (pages 1351–1355)

      Zhibo Yan, Yanyan Guo, Guoquan Zhang and J.-M. Liu

      Article first published online: 15 FEB 2011 | DOI: 10.1002/adma.201004306

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      Non-volatile memory cells using Co-doped BaTiO3 as an active layer exhibit high-performance unipolar resistive switching characteristics, with a resistance ratio over 104, retention time longer than 7 × 104 s, endurance over 105 cycles, and switching speed less than 10 ns/70 ns for SET/RESET. Under high electric field and large Joule heating, the easily varied valence of Co ions, the pre-existing oxygen vacancies with sufficiently high density, and the local itinerant electrons introduced by the Co-doping all favor the local metal-insulator phase transition and therein the formation/rupture of conductive filaments, contributing to the stable resistive switching.

    6. Super Deformability and Young’s Modulus of GaAs Nanowires (pages 1356–1360)

      Yan-Bo Wang, Li-Feng Wang, Hannah J. Joyce, Qiang Gao, Xiao-Zhou Liao, Yiu-Wing Mai, Hoe H. Tan, Jin Zou, Simon P. Ringer, Hua-Jian Gao and Chennupati Jagadish

      Article first published online: 15 FEB 2011 | DOI: 10.1002/adma.201004122

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      A significant size effect on the mechanical properties of GaAs nanowires (NWs) is reported. A remarkable elastic strain of ≈11% for NWs with diameters of 50–150 nm and obvious plastic deformation in NWs with diameters ≤25 nm are revealed. The Young’s modulus of the NWs can be more than double that of bulk GaAs.

    7. Hybrid Polyester Coating Incorporating Functionalized Mesoporous Carriers for the Holistic Protection of Steel Surfaces (pages 1361–1365)

      Martin J. Hollamby, Dmitri Fix, Ingo Dönch, Dimitriya Borisova, Helmuth Möhwald and Dmitry Shchukin

      Article first published online: 2 FEB 2011 | DOI: 10.1002/adma.201003035

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      Hybrid coatings are formed by dispersing inhibitor (benzotriazole) containing functionalized mesoporous silica nanoparticles throughout a polyester primer. They outperform the primer in corrosion tests both when intact and scratched. Adding the inhibitor directly (without encapsulation into nanoparticles) is found to be less effective. Given the afforded holistic protection, these hybrid coatings represent an excellent model for future coating design.

    8. Heavily Doped p-Type PbSe with High Thermoelectric Performance: An Alternative for PbTe (pages 1366–1370)

      Heng Wang, Yanzhong Pei, Aaron D. LaLonde and G. Jeffrey Snyder

      Article first published online: 10 FEB 2011 | DOI: 10.1002/adma.201004200

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      PbSe was expected to have a smaller bandgap and higher thermalconductivity than PbTe. Instead, these values are about the same at high temperature leading to comparable thermoelectric figure of merit, with zT> 1 achieved in heavily doped p-type PbSe.

    9. Electrically Programmable Magnetoresistance in Multifunctional Organic-Based Spin Valve Devices (pages 1371–1375)

      Mirko Prezioso, Alberto Riminucci, Ilaria Bergenti, Patrizio Graziosi, David Brunel and Valentin A. Dediu

      Article first published online: 7 FEB 2011 | DOI: 10.1002/adma.201003974

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      A multifunctional organic spintronic device is demonstrated using tris(8-hydroxyquinolinato)aluminium (Alq3)-based vertical spin valves with manganite and cobalt electrodes. The device shows a non-volatile electrical switching with dramatic effects on the spin transport behavior. The interplay of electrical and magnetic bistabilities enables the electrical control of the spin valve magnetoresistance. This multifunctionality is illustrated together with a phenomenological model that establishes a connection between the electrical and magnetic bistabilities.

    10. Template-Assisted Polyelectrolyte Encapsulation of Nanoparticles into Dispersible, Hierarchically Nanostructured Microfibers (pages 1376–1379)

      Dorothee Kohler, Marc Schneider, Michael Krüger, Claus-Michael Lehr, Helmuth Möhwald and Dayang Wang

      Article first published online: 15 FEB 2011 | DOI: 10.1002/adma.201004048

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      Nanoporous membranes are used as templates for polyelectrolyte encapsu­lation of colloidal nanoparticles, leading to colloidally dispersible, multifunctional, and multicompartment microfibers. The protocol is simple and independent of the chemical nature of the nanoparticles and polyelectrolytes. Furthermore, the surface polyelectrolyte coating allows free transfer of the resulting microfibers into various aqueous and organic media.

    11. Self-Modulated White Light Outcoupling in Doped Organic Nanowire Waveguides via the Fluctuations of Singlet and Triplet Excitons During Propagation (pages 1380–1384)

      Chuang Zhang, Jian Yao Zheng, Yong Sheng Zhao and Jiannian Yao

      Article first published online: 4 FEB 2011 | DOI: 10.1002/adma.201003829

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      A kind of optical modulators based on doped organic nanowire waveguides that output constant white light from the wire terminus has been demonstrated. When the waveguides are locally excited with a focused laser, bidirectional singlet and triplet energy transfers between the two compounds result in the fluctuations of the singlet and triplet excitons, which induce self-modulated white light outcoupling from each waveguide despite the doping contents.

    12. Porous Li4Ti5O12 Coated with N-Doped Carbon from Ionic Liquids for Li-Ion Batteries (pages 1385–1388)

      Liang Zhao, Yong-Sheng Hu, Hong Li, Zhaoxiang Wang and Liquan Chen

      Article first published online: 2 FEB 2011 | DOI: 10.1002/adma.201003294

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      A uniform nitrogen-doped carbon coating layer is formed on Li4Ti5O12 particles by mixing porous Li4Ti5O12 powder with an ionic liquid and then treating the mixture at moderate temperature. Uniformly coated Li4Ti5O12 is shown to have significantly improved rate capability and cycling performance for Li-ion batteries. This relatively simple approach is versatile and can be extended to modify other electrode materials for electrochemical devices.

    13. Widely Tunable, Photoinvertible Cholesteric Liquid Crystals (pages 1389–1392)

      Timothy J. White, Seth A. Cazzell, Alexander S. Freer, Deng-Ke Yang, Ludmila Sukhomlinova, Linli Su, Tamas Kosa, Bahman Taheri and Timothy J. Bunning

      Article first published online: 4 FEB 2011 | DOI: 10.1002/adma.201003577

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      A photoinvertible chiral molecule allows for wide-range tuning encompassing the entirety of the optical range. UV light inverts the handedness of the cholesteric liquid-crystal (CLC) helix, which yields color tuning of the reflection notch. After the light is removed, the material quickly relaxes back to the original conformation. The optical properties of the CLC during tuning/inversion are correlated to the mesomorphic behavior of the mixture.

    14. Memory Effect in Magnetic Nanowire Arrays (pages 1393–1397)

      Xiaoming Kou, Xin Fan, Randy K. Dumas, Qi Lu, Yaping Zhang, Hao Zhu, Xiaokai Zhang, Kai Liu and John Q. Xiao

      Article first published online: 7 FEB 2011 | DOI: 10.1002/adma.201003749

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      A memory effect has been demonstrated in magnetic nanowire arrays. The magnetic nanowire array has the ability to record the maximum magnetic field that the array has been exposed to after the field has been turned off. The origin of the memory effect is the strong magnetic dipole interaction among the nanowires. Switching field distributions among nanowires has been studied with a first-order reversal curve technique to elucidate the discrepancy between the experimental result and the theoretical explanation. Based on the memory effect, a novel and extremely low cost EMP detection scheme is proposed.

    15. Three-Dimensional Morphology of Iron Phosphide Phases in a Polycrystalline LiFePO4 Matrix (pages 1398–1403)

      Sung-Yoon Chung, Jin-Gyu Kim, Young-Min Kim and Young-Bu Lee

      Article first published online: 8 FEB 2011 | DOI: 10.1002/adma.201003856

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      The three-dimensionally isolated morp­hology of secondary iron phosphide phases in a polycrystalline LiFePO4 matrix is determined using a combination of electron tomography in high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDS), and electron energy-loss spectroscopy (EELS). The present evidence shows that the enhanced bulk electronic conductivity in LiFePO4 has no relation to secondary metallic phases at the grain boundaries.

    16. Excitonic Properties and Near-Infrared Coherent Random Lasing in Vertically Aligned CdSe Nanowires (pages 1404–1408)

      Rui Chen, Muhammad Iqbal Bakti Utama, Zeping Peng, Bo Peng, Qihua Xiong and Handong Sun

      Article first published online: 15 FEB 2011 | DOI: 10.1002/adma.201003820

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      High-quality, vertically aligned CdSe nanowires (figure, top left) are prepared by the vapor transport growth technique. Strong free-exciton absorption and emission are observed (top right) and, under optical excitation, near-infrared coherent random lasing is demonstrated for the first time from CdSe nanowires at room temperature (bottom). The results show that this material system holds promise for optoelectronic applications.

    17. A Versatile Low Bandgap Polymer for Air-Stable, High-Mobility Field-Effect Transistors and Efficient Polymer Solar Cells (pages 1409–1413)

      Kok-Haw Ong, Siew-Lay Lim, Huei-Shuan Tan, Hoi-Ka Wong, Jun Li, Zhun Ma, Lionel C. H. Moh, Suo-Hon Lim, John C. de Mello and Zhi-Kuan Chen

      Article first published online: 21 JAN 2011 | DOI: 10.1002/adma.201003903

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      A new low bandgap polymer POD2T-DTBT has been synthesized and found to give excellent performances in organic thin-film transistor (OTFT) and organic photovoltaic (OPV) applications. OTFTs based on POD2T-DTBT have achieved good hole carrier mobilities of 0.2 cm2V−1s−1 and OPVs based on blends of POD2T-DTBT and PC71BM have demonstrated promising power conversion efficiencies of 6.26%.

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