Advanced Materials

Cover image for Vol. 22 Issue 33

September 1, 2010

Volume 22, Issue 33

Pages 3627–3748

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Progress Report
    6. Communications
    1. Antireflective Films: Nano-tailoring the Surface Structure for the Monolithic High-Performance Antireflection Polymer Film (Adv. Mater. 33/2010)

      Kiwoon Choi, Sung Ho Park, Young Min Song, Yong Tak Lee, Chang Kwon Hwangbo, Hoichang Yang and Han Sup Lee

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201090108

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      Nanotailoring of the shape and dimensions of high-density arrays of nanostructures can be carried out to fabricate monolithic high-performance antireflection polymer films, report Han Sup Lee and co-workers on p. 3713. The average total reflectivity from an artificial antireflection film fabricated using this technique is reduced to 0.64% in the visible wavelength range, a significantly improved antireflection performance for transparent polymer antireflection films.

  2. Inside Front Cover

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Progress Report
    6. Communications
    1. Organic Electronics: Tuning the Columnar Organization of Discotic Polycyclic Aromatic Hydrocarbons (Adv. Mater. 33/2010)

      Wojciech Pisula, Xinliang Feng and Klaus Müllen

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201090109

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      The packing of disk-shaped polycyclic aromatic hydrocarbons (PAHs) in columnar superstructures plays an essential role for charge-carrier transport along such 1D stacks in organic solar cells and field-effect transistors. On p. 3634, Wojciech Pisula, Xinliang Feng and Klaus M�llen review concepts applied to control of the intracolumnar interactions between building blocks. The broad toolbox of peripheral substitutions allows modification of the columnar arrangement, including alkyl side chains of different geometry, hydrogen bonds, dipole moments, and sterically demanding rigid groups.

  3. Contents

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Progress Report
    6. Communications
  4. Progress Report

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Progress Report
    6. Communications
    1. Tuning the Columnar Organization of Discotic Polycyclic Aromatic Hydrocarbons (pages 3634–3649)

      Wojciech Pisula, Xinliang Feng and Klaus Müllen

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000585

      Thumbnail image of graphical abstract

      The control of the intracolumnar organization of disc-shaped polycyclic aromatic hydrocarbons has essential influence on material’s properties including thermotropic behavior and charge carrier transport which are crucial for applications in organic electronics. The utilization of a broad toolbox of peripheral substitution allows well-defined modification of the molecular interactions and packing within helical columnar stacks (see figure).

  5. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Progress Report
    6. Communications
    1. Low-Temperature Ionic-Liquid-Based Synthesis of Nanostructured Iron-Based Fluoride Cathodes for Lithium Batteries (pages 3650–3654)

      Chilin Li, Lin Gu, Susumu Tsukimoto, Peter A. van Aken and Joachim Maier

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000535

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      A mesoporous iron-based fluoride cathode for lithium batteries is fabricated by a novel low-temperature non-aqueous synthesis based on ionic liquid medium. The hydration-water-induced microstructural optimization and morphological decoration are expected to contribute positively to both the large reversible Li-storage capacity and the high reactive voltage of carbon-free FeF3 · 0.33H2O at room temperature.

    2. The Application of Organic Electrochemical Transistors in Cell-Based Biosensors (pages 3655–3660)

      Peng Lin, Feng Yan, Jinjiang Yu, Helen L. W. Chan and Mo Yang

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000971

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      Cells are cultivated on top of an organic electrochemical transistor. The activities of the cells can be monitored by characterizing the transistor because the performance of the transistor is sensitive to the surface charge and the morphology of the attached cells due to the electrostatic interaction between the cells and the active layer of the transistor.

    3. Polarized Emission and Optical Waveguide in Crystalline Perylene Diimide Microwires (pages 3661–3666)

      Qiaoliang Bao, Bee Min Goh, Bin Yan, Ting Yu, Zexiang Shen and Kian Ping Loh

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000731

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      We report the first optical waveguide based on perylene diimide (PDI) crystalline microwires. The birefringence, polarized photoluminescence emission, long distance light waveguide as well as electrical-optical modulation were studied. PDI is a good polymeric electro-optic material because of its low relative permittivity, low operating voltage, high thermal and photo-stability, and easy integration on flexible substrates.

    4. Local-Illuminated Ultrathin Silicon Nanomembranes with Photovoltaic Effect and Negative Transconductance (pages 3667–3671)

      Ping Feng, Ingolf Mönch, Gaoshan Huang, Stefan Harazim, Elliot J. Smith, Yongfeng Mei and Oliver G. Schmidt

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000583

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      Ultrathin silicon nanomembranes (SiNMs) on insulators under local illumination reveal a gate-controlled photovoltaic effect and negative transconductance in Schottky transistors applying both homo- and heterocontacts. Tiny variations of Schottky barriers between source and drain contacts are responsible for the photovoltaic effect in ultrathin SiNMs and can be enhanced by gate voltage and/or contact design.

    5. Direct Measurement of Electric Field-Assisted Charge Separation in Polymer:Fullerene Photovoltaic Diodes (pages 3672–3676)

      R. Alex Marsh, Justin M. Hodgkiss and Richard H. Friend

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201001010

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      The electric field dependence of transient optical absorption of photogenerated charge carriers in working organic photovoltaic cells is reported. Charge lifetimes are extended under reverse bias, revealing that the mechanism of photocurrent generation is the electric field-assisted separation of Coulombically bound charge pairs in kinetic competition with geminate charge recombination.

    6. Nanoscale Organic Hybrid Electrolytes (pages 3677–3680)

      Jennifer L. Nugent, Surya S. Moganty and Lynden A. Archer

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000898

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      Nanoscale organic hybrid electrolytes are composed of organic-inorganic hybrid nanostructures, each with a metal oxide or metallic nanoparticle core densely grafted with an ion-conducting polyethylene glycol corona - doped with lithium salt. These materials form novel solvent-free hybrid electrolytes that are particle-rich, soft glasses at room temperature ; yet manifest high ionic conductivity and good electrochemical stability above 5V.

    7. Dye Molecules Encapsulated in a Micelle Structure: Nano-Aggregates with Enhanced Optical Properties (pages 3681–3684)

      Gabriele Rainò, Thilo Stöferle, Chanhee Park, Ho-Cheol Kim, In-Joo Chin, Robert D. Miller and Rainer F. Mahrt

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000233

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      Nanocomposite materials are attracting increasing interest owing to their application potential in various fields, including light-emitting devices, photovoltaic devices, and lithographic tools. Here we focus on the optical properties of dye-doped micelle structure dispersed in polystyrene thin films. The intriguing optical properties of such supramolecular nanocomposites can be explained by considering the formation of J-nanoaggregates concomitant with superradiant behavior.

    8. Catalyst and Chirality Dependent Growth of Carbon Nanotubes Determined Through Nano-Test Tube Chemistry (pages 3685–3689)

      Hidetsugu Shiozawa, Christian Kramberger, Rudolf Pfeiffer, Hans Kuzmany, Thomas Pichler, Zheng Liu, Kazu Suenaga, Hiromichi Kataura and S. Ravi P. Silva

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201001211

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      The interior of carbon nanotubes, provide a homogeneous, contaminant-free environment in which to perform nanoreactions, hence the term nano-test tubes. Here, routes for the controlled growth of carbon nanotubes with defined chiral indices are presented within the interior of single-walled carbon nanotubes upon the encapsulation of Pt and Fe catalysts, plus the carbon source in controlled proportions. Factors affecting the growth (e.g. temperature) are examined experimentally.

    9. Ultra-Broad Optical Amplification and Two-Colour Amplified Spontaneous Emission in Binary Blends of Insulated Molecular Wires (pages 3690–3694)

      Sergio Brovelli, Tersilla Virgili, Marta M. Mroz, Giuseppe Sforazzini, Alberto Paleari, Harry L. Anderson, Guglielmo Lanzani and Franco Cacialli

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000895

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      We demonstrate optical amplification over a band >850 meV, via simultaneous exploitation of stimulated emission from mixed polymer systems in which energy transfer from the higher to lower-gap material is inhibited thanks to a complex interplay between morphology and interchain decoupling, driven by chain encapsulation. Amplified spontaneous emission (ASE) is obtained both with ad-hoc pumping into the relevant bands or with a single excitation (400nm) able to sustain ASE at both wavelengths simultaneously (two-colour ASE).

    10. Two-Photon Lithography of Sub-Wavelength Metallic Structures in a Polymer Matrix (pages 3695–3699)

      Shobha Shukla, Edward P. Furlani, Xavier Vidal, Mark T. Swihart and Paras N. Prasad

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000059

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      A novel method for fabricating metallic nanostructures with sub-wavelength resolution in a polymer using simultaneous two-photon initiated reduction of a metal salt and polymerization of a negative photoresist is demonstrated. Gold nanoparticle-doped lines as narrow as 200 nm were fabricated. The dependence of line-width on laser intensity and scan speed are captured well by an analytical model. We created functional gratings and planar chiral elements, characterized their optical properties, and modeled their electromagnetic response.

    11. Shear-Mode Contact Splitting for a Microtextured Elastomer Film (pages 3700–3703)

      Rebecca K. Kramer, Carmel Majidi and Robert J. Wood

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000897

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      Texturing the surface of a PDMS film with microscale pillars allows shear load to be uniformly distributed through the interface that bonds the film to a rigid substrate. This mechanism is demonstrated with shear tests on micropatterned samples and explains the order-of-magnitude enhancement of shear adhesion compared to smooth, untextured PDMS films.

    12. Stability Assessment on a 3% Bilayer PbS/ZnO Quantum Dot Heterojunction Solar Cell (pages 3704–3707)

      Joseph M. Luther, Jianbo Gao, Matthew T. Lloyd, Octavi E. Semonin, Matthew C. Beard and Arthur J. Nozik

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201001148

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      We provide the first NREL-certified efficiency measurement on an all-inorganic, solution-processed, nanocrystal solar cell. The 3% efficient device is composed of ZnO nanocrystals and 1.3 eV PbS quantum dots with gold as the top contact. This configuration yields a stable device, retaining 95% of the starting efficiency after a 1000-hour light soak in air without encapsulation.

    13. Current-Injected Spectrally-Narrowed Emissions from an Organic Transistor (pages 3708–3712)

      Takeshi Yamao, Yoichi Sakurai, Kohei Terasaki, Yasuhiro Shimizu, Hiroshi Jinnai and Shu Hotta

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000171

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      A novel organic LEFET device with a simple device constitution is presented. The device is equipped with a diffraction grating that is formed on the gate insulator so that it is located outside the channel region. When the device is operated with square-wave alternating gate voltages, the spectrally-narrowed emissions are definitively observed with FWHM ∼2 nm.

    14. Nano-tailoring the Surface Structure for the Monolithic High-Performance Antireflection Polymer Film (pages 3713–3718)

      Kiwoon Choi, Sung Ho Park, Young Min Song, Yong Tak Lee, Chang Kwon Hwangbo, Hoichang Yang and Han Sup Lee

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201001678

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      Nano-tailoring the shape and dimensions of the parabolic antireflective structure predicted by simulation has been successfully carried out to fabricate monolithic high-performance antireflection (AR) polymer films. The average total reflectivity from an artificial antireflection film is lowered down to 0.64% at a wavelength range of 400 nm to 800 nm, which appears to be the best antireflection performance ever reported for transparent polymer antireflection films.

    15. A General Preparation Strategy for Hybrid TiO2 Hierarchical Spheres and Their Enhanced Solar Energy Utilization Efficiency (pages 3719–3722)

      Xujie Lü, Fuqiang Huang, Xinliang Mou, Yaoming Wang and Fangfang Xu

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201001008

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      A new composite structure of TiO2|ZnO:Ti|ZnO effective for improving charge separation and electron transport is demonstrated for solar energy applications. A prototype material of hybrid TiO2/ZnO hollow spheres is prepared by a hydrated-salt assisted solvothermal (HAS) strategy. This material is applied as a photocatalyst and an anode material for dye-sensitized solar cells (DSSCs). Enhanced solar energy utilization efficiencies can be observed.

    16. A Three-Dimensional Carbon Nanotube/Graphene Sandwich and Its Application as Electrode in Supercapacitors (pages 3723–3728)

      Zhuangjun Fan, Jun Yan, Linjie Zhi, Qiang Zhang, Tong Wei, Jing Feng, Milin Zhang, Weizhong Qian and Fei Wei

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201001029

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      Three-dimensional carbon nanotube/graphene sandwich structures with CNT pillars grown in between the graphene layers have been developed by chemical vapor deposition. The special structure endows the high-rate transportation of electrolyte ions and electrons throughout the electrode matrix, resulting in excellent electrochemical performance of this hybrid material.

    17. Self-Assembled Organic–Inorganic Hybrid Elastic Crystal via Biomimetic Mineralization (pages 3729–3734)

      Halei Zhai, Wenge Jiang, Jinhui Tao, Siyi Lin, Xiaobin Chu, Xurong Xu and Ruikang Tang

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000941

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      Organic–inorganic hybrid rhombs with regular shape and a lamellar superstructure are biomimetically fabricated by the cooperative self-assembly of bovine serum albumin (BSA), sodium bis-2-ethylhexyl sulfosuccinate (AOT), and calcium phosphate (see figure). Although crystalline calcium phosphate is the main component, the hybrid crystals are elastic and they can be flexible under external stresses.

    18. Novel Design of La(Fe,Si)13 Alloys Towards High Magnetic Refrigeration Performance (pages 3735–3739)

      Julia Lyubina, Rudolf Schäfer, Norbert Martin, Ludwig Schultz and Oliver Gutfleisch

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201000177

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      LaFe13−xSix alloys with porous architecture do not degrade mechanically during cycling and maintain their excellent cooling performance, which was not accessible before. The ability to control the magnetocaloric effect and hysteresis by tuning of crystallite size promises applicability of these materials in magnetic refrigeration and porous materials exhibiting a first-order transition in general in diverse energy-related applications.

    19. Locally Resolved Core-hole Screening, Molecular Orientation, and Morphology in Thin Films of Diindenoperylene Deposited on Au(111) Single Crystals (pages 3740–3744)

      Maria Benedetta Casu, Britt-Elfriede Schuster, Indro Biswas, Christoph Raisch, Helder Marchetto, Thomas Schmidt and Thomas Chassé

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201001265

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      Highly resolved spectromicroscopy reveals that characteristics like electronic structure, core-hole screening, and molecular orientation depend on the local morphology of the thin films. These phenomena, like different screening of the core hole, or different FWHM of the XPS lines, have been previously shown comparing different samples consisting of monolayers and multilayers. On the contrary, in our work we show their occurrence comparing islands versus monolayers in the same film.

    20. Biocompatible Composite Actuator: A Supramolecular Structure Consisting of the Biopolymer Chitosan, Carbon Nanotubes, and an Ionic Liquid (pages 3745–3748)

      Luhua Lu and Wei Chen

      Version of Record online: 20 AUG 2010 | DOI: 10.1002/adma.201001134

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      A composite actuator constructed from a carbon nanotube/biopolymer supramolecular structure (see figure) that can be driven by electrical stimulation independently without solution environment support is presented. It is lightweight, constructed from biocompatible components, and exhibits considerable actuation performance at low voltage, making it of great value for biomedical applications.

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