Advanced Functional Materials

Cover image for Vol. 21 Issue 19

October 7, 2011

Volume 21, Issue 19

Pages 3597–3793

  1. Cover Picture

    1. Top of page
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    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Feature Article
    7. Full Papers
    8. Frontispiece
    9. Full Papers
    1. Tissue Engineering: Stereolithography-Based Hydrogel Microenvironments to Examine Cellular Interactions (Adv. Funct. Mater. 19/2011) (page 3597)

      Pinar Zorlutuna, Jae Hyun Jeong, Hyunjoon Kong and Rashid Bashir

      Version of Record online: 26 SEP 2011 | DOI: 10.1002/adfm.201190080

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      Unique multifunctional, biodegradable, and biocompatible hydrogels are used to encapsulate hippocampal neurons and myoblast cells using stereolithography to create complex 3D tissue structures. As reported on page 3642 by Rashid Bashir and coworkers, this system is able to accommodate both cell types, while a spatially patterned 3D co-culture of these cells results in enhanced cholinergic activity of the hippocampal neurons. (Image courtesy of Janet Hanlon-Sin at ITG Beckman Institute, UIUC).

  2. Inside Front Cover

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Feature Article
    7. Full Papers
    8. Frontispiece
    9. Full Papers
    1. Organic Field-Effect Transistors: Direct UV Patterning of Electronically Active Fullerene Films (Adv. Funct. Mater. 19/2011) (page 3598)

      Jia Wang, Christian Larsen, Thomas Wågberg and Ludvig Edman

      Version of Record online: 26 SEP 2011 | DOI: 10.1002/adfm.201190081

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      UV light is utilized for the attainment of high-resolution and electronically active patterns in [6,6]-phenyl C61-butyric acid methyl ester (PCBM) films with a novel, photoresist-free method. On page 3723, Ludvig Edman and co-workers present the fabrication of patterns by directly exposing selected parts of a solution-cast PCBM film to UV light. Complex, large-area PCBM structures with features of 1 μm are obtained, and the patterned material exhibits a high average electron mobility in transistor experiments.

  3. Back Cover

    1. Top of page
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    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Feature Article
    7. Full Papers
    8. Frontispiece
    9. Full Papers
    1. Electro-optical Materials: Solution-Processed Organic Light-Emitting Transistors Incorporating Conjugated Polyelectrolytes (Adv. Funct. Mater. 19/2011) (page 3794)

      Jung Hwa Seo, Ebinazar B. Namdas, Andrea Gutacker, Alan J. Heeger and Guillermo C. Bazan

      Version of Record online: 10 OCT 2011 | DOI: 10.1002/adfm.201190084

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      Improved performance of p-type organic lightemitting transistors (OLETs) is demonstrated by Alan J. Heeger, Guillermo C. Bazan, and coworkers on page 3667 by introducing a conjugated polyelectrolyte (CPE) layer and symmetric high-work-function source and drain electrodes. The thickness of the CPE layer is critical for achieving good performance and provides an important structural handle for consideration in future optimization studies. Multicolor OLETs are demonstrated via choice of emissive layer.

  4. Contents

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Feature Article
    7. Full Papers
    8. Frontispiece
    9. Full Papers
  5. Feature Article

    1. Top of page
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    5. Contents
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    1. Towards the Next Level of Bioinspired Dry Adhesives: New Designs and Applications (pages 3606–3616)

      Moon Kyu Kwak, Changhyun Pang, Hoon-Eui Jeong, Hong-Nam Kim, Hyunsik Yoon, Ho-Sup Jung and Kahp-Yang Suh

      Version of Record online: 12 SEP 2011 | DOI: 10.1002/adfm.201100982

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      This Feature Article highlights a series of recent achievements that overcome some of the limitations of gecko-inspired dry adhesive structures such as rough surface adaptation, durability, and controlled geometry, with particular emphasis on materials issues and detachment mechanism.

  6. Full Papers

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    1. Enhanced Performance Consistency in Nanoparticle/TIPS Pentacene-Based Organic Thin Film Transistors (pages 3617–3623)

      Zhengran He, Kai Xiao, William Durant, Dale K. Hensley, John E. Anthony, Kunlun Hong, S. Michael Kilbey II, Jihua Chen and Dawen Li

      Version of Record online: 7 JUL 2011 | DOI: 10.1002/adfm.201002656

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      Inorganic silica nanoparticles are used to manipulate the morphology of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS pentacene) thin films, which leads to a 3-fold increase in average mobility and a nearly 4 times reduction in the ratio of measured mobility standard deviation (μStdev) to average mobility (μAvg). Grazing-incidence X-ray diffraction, optical, and electron microscopy are used to investigate the nanoparticle-mediated TIPS pentacene crystallization.

    2. Self-Healing Fibre Reinforced Composites via a Bioinspired Vasculature (pages 3624–3633)

      Christopher J. Norris, Gregory J. Meadway, Michael J. O'Sullivan, Ian P. Bond and Richard S. Trask

      Version of Record online: 1 AUG 2011 | DOI: 10.1002/adfm.201101100

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      Bioinspired vasculatures embedded in fibre reinforced polymer laminates are tailored to minimise disruption to the hosts fibre architecture whilst maximising damage– vascule interactions to impart self-healing functionality. Delivery of healing agent to regions of internal damage via such vascules provides outstanding recovery of post impact compression strength ≥96%, thereby ameliorating the susceptibility of such materials to in-service damage.

    3. Bioinspired Design Criteria for Damage-Resistant Materials with Periodically Varying Microstructure (pages 3634–3641)

      Otmar Kolednik, Jozef Predan, Franz Dieter Fischer and Peter Fratzl

      Version of Record online: 3 AUG 2011 | DOI: 10.1002/adfm.201100443

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      Inspired by the analysis of natural composites made of bio-glass and protein, a criterion for the design of flaw-tolerant and damage-resistant multilayered materials is developed. The criterion proposes that the thickness of the layers should be chosen as a function of the stiffness and fracture properties of the two components in the multilayer. When the thickness of the stiff layer is small enough, cracks are arrested in the soft layer and cannot propagate further.

    4. Stereolithography-Based Hydrogel Microenvironments to Examine Cellular Interactions (pages 3642–3651)

      Pinar Zorlutuna, Jae Hyun Jeong, Hyunjoon Kong and Rashid Bashir

      Version of Record online: 17 AUG 2011 | DOI: 10.1002/adfm.201101023

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      Oxidized methacrylic alginate and poly(ethylene glycol)methacrylate is used to fabricate unique hydrogels that are multifunctional, biodegradable, and biocompatible. Stereolithography is used to encapsulate hippocampal neurons and myoblast cells to create complex 3D structures. This system is able to accommodate both cell types, while spatially patterned 3D co-culture of these cells results in enhanced cholinergic activity of the HNs.

    5. Optimized Colorimetric Photonic-Crystal Humidity Sensor Fabricated Using Glancing Angle Deposition (pages 3652–3658)

      Matthew M. Hawkeye and Michael J. Brett

      Version of Record online: 5 AUG 2011 | DOI: 10.1002/adfm.201100893

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      The structural color of mesoporous photo­nic crystals (PCs) is highly sensitive to environmental changes, making them ideally suited as optical sensors. Here, this effect is exploited in the nanofabrication and characterization of an optimized PC design for humidity sensing. The sensor performance is excellent and the new quantitative analysis methods developed will be useful for future color-based sensor design.

    6. Encapsulation of RNA Molecules in BSA Microspheres and Internalization into Trypanosoma Brucei Parasites and Human U2OS Cancer Cells (pages 3659–3666)

      Ulyana Shimanovich, Itai Dov Tkacz, Dror Eliaz, Artur Cavaco-Paulo, Shulamit Michaeli and Aharon Gedanken

      Version of Record online: 9 AUG 2011 | DOI: 10.1002/adfm.201100963

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      A novel environmentally friendly method for the synthesis of RNA-loadedproteinaceous microspheres involving the use of ultrasonic waves was developed. The RNA-loaded spheres were used as a drug (RNA) delivery agent and were successfully introduced into trypanosoma brucei parasites and human U2OS cancer cells without use of any additional mediators.

    7. Solution-Processed Organic Light-Emitting Transistors Incorporating Conjugated Polyelectrolytes (pages 3667–3672)

      Jung Hwa Seo, Ebinazar B. Namdas, Andrea Gutacker, Alan J. Heeger and Guillermo C. Bazan

      Version of Record online: 18 JUL 2011 | DOI: 10.1002/adfm.201100682

      Thumbnail image of graphical abstract

      Improved performance of p-type organic light-emitting transistors (OLETs) is demonstrated by introducing a conjugated polyelectrolyte (CPE) layer and symmetric high work function source and drain electrodes. The thickness of the CPE layer is critical for achieving good performance and provides an important structural handle for consideration in future optimization studies. Multicolor OLETs were demonstrated via choice of emissive layer.

    8. Biomimetic Solid-Solution Precursors of Metal Carbonate for Nanostructured Metal Oxides: MnO/Co and MnO-CoO Nanostructures and Their Electrochemical Properties (pages 3673–3680)

      Takao Kokubu, Yuya Oaki, Eiji Hosono, Haoshen Zhou and Hiroaki Imai

      Version of Record online: 9 AUG 2011 | DOI: 10.1002/adfm.201101138

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      Biomimetic solid solutions of MnCO3–CoCO3 are used as the precursors for the synthesis of a variety of metal oxides with porous morphologies, such as MnO, MnO–CoO solid solution, and MnO/Co nanocomposite. The resultant MnO/Co nanocomposite shows the enhanced electrochemical performance as an anode material of lithium-ion battery.

    9. Nonstick, Modulus-Tunable and Gas-Permeable Replicas for Mold-Based, High-Resolution Nanolithography (pages 3681–3689)

      Bong Kuk Lee, Hyunmin Cho and Bong Hyun Chung

      Version of Record online: 8 AUG 2011 | DOI: 10.1002/adfm.201101278

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      SSQMA/acrylic/Si-DA blends with low-viscosity are proposed as a nonstick replica-mold material for mold-based, high-resolution nanolithography. Cured mold materials show high UV transparency, low swelling ratio, low shrinkage, low surface tension and wide-range modulus tunability. Sufficiently cured, nonstick replica molds have the potential to duplicate sub-25-nm features with a high pattern density and a high aspect ratio. A gas-permeable robust replica mold prevented bubble defects in the imprinting process.

  7. Frontispiece

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Feature Article
    7. Full Papers
    8. Frontispiece
    9. Full Papers
    1. Organic Semiconductors: Vibrationally Assisted Polariton-Relaxation Processes in Strongly Coupled Organic-Semiconductor Microcavities (Adv. Funct. Mater. 19/2011) (page 3690)

      David M. Coles, Paolo Michetti, Caspar Clark, Wing Chung Tsoi, Ali M. Adawi, Ji-Seon Kim and David G. Lidzey

      Version of Record online: 26 SEP 2011 | DOI: 10.1002/adfm.201190083

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      If a layer of cyanine dye J-aggregates is placed in an optical cavity, interactions between the confi ned optical fi eld and the molecular excitons leads to the formation of cavity polaritons. On page 3691, David G. Lidzey and co-workers present vibrationally assisted polariton relaxation in strongly coupled organic semiconductor microcavities. The population of polaritons from uncoupled excitons that are initially generated following non-resonant excitation is mediated by interactions with the Raman-active molecular vibrations of the cyanine dye.

  8. Full Papers

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Feature Article
    7. Full Papers
    8. Frontispiece
    9. Full Papers
    1. Vibrationally Assisted Polariton-Relaxation Processes in Strongly Coupled Organic-Semiconductor Microcavities (pages 3691–3696)

      David M. Coles, Paolo Michetti, Caspar Clark, Wing Chung Tsoi, Ali M. Adawi, Ji-Seon Kim and David G. Lidzey

      Version of Record online: 4 JUL 2011 | DOI: 10.1002/adfm.201100756

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      A fast relaxation path for populating lower-branch polariton states arises from the interactions between excitons and the molecular vibrations of the organic material in a strongly coupled microcavity containing an organic semiconductor. This process, followed by angle- and temperature- dependent spectroscopy, may allow efficient population of polariton states in the momentum trap from which nonlinear phenomena occur.

    2. Anisotropic Structure and Charge Transport in Highly Strain-Aligned Regioregular Poly(3-hexylthiophene) (pages 3697–3705)

      Brendan O'Connor, R. Joseph Kline, Brad R. Conrad, Lee J. Richter, David Gundlach, Michael F. Toney and Dean M. DeLongchamp

      Version of Record online: 16 AUG 2011 | DOI: 10.1002/adfm.201100904

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      A novel method of strain-aligning polymer films is introduced and applied to the semiconducting polymer, regioregular poly(3-hexylthiophene) (P3HT). Detailed morphological and electronic characterization is performed on the aligned film, showing several important features of charge transport. The polymer backbone is shown to align in the direction of applied strain resulting in a mobility anisotropy as high as 9. Reported results indicate that charge transport parallel to the polymer backbone within a P3HT crystal is strongly favored over the other crystallographic directions. (OTFT = organic thin-film transistor)

    3. Modular Functionalization of Electrodes by Cross-Coupling Reactions at Their Surfaces (pages 3706–3714)

      Marcel Müri, Bernd Gotsmann, Yann Leroux, Marius Trouwborst, Emanuel Lörtscher, Heike Riel and Marcel Mayor

      Version of Record online: 25 AUG 2011 | DOI: 10.1002/adfm.201100642

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      A new modular technique to modify platinum electrodes is presented, which consists of the electroreduction of aryl diazonium salts combined with the Sonogashira cross-coupling reaction in the solid state. This combination allows the introduction of a wide range of functional groups onto surfaces, with high surface coverage by the functional subunit.

    4. Hierarchical Superhydrophobic Surfaces Fabricated by Dual-Scale Electron-Beam-Lithography with Well-Ordered Secondary Nanostructures (pages 3715–3722)

      Jiansheng Feng, Mark T. Tuominen and Jonathan P. Rothstein

      Version of Record online: 11 JUL 2011 | DOI: 10.1002/adfm.201100665

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      A novel, versatile, efficient technique for fabricating macroscopic hierarchical surfaces with both well-defined primary microstructures and well-ordered secondary nanostructures using electron-beam-lithography is reported. Size, shape, and distribution of the secondary-features are can be controlled. Superhydrophobic surfaces produced by this technique help to quantitatively understand how details of the hierarchical strucutres affect the surface properties.

    5. Direct UV Patterning of Electronically Active Fullerene Films (pages 3723–3728)

      Jia Wang, Christian Larsen, Thomas Wågberg and Ludvig Edman

      Version of Record online: 28 JUL 2011 | DOI: 10.1002/adfm.201100568

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      High-resolution, electronically active patterns have been created in a PCBM film by using UV light. The patterns are created by directly exposing selected parts of the solution-cast film to UV light, and thereafter developing the film by immersing it in a tuned developer solution. We demonstrate that it is possible to attain complex, large-area structures with a smallest-feature size of 1 μm by this scalable method, and that the patterned film exhibits high electron mobility in transistor experiments.

    6. Amplifying Charge-Transfer Characteristics of Graphene for Triiodide Reduction in Dye-Sensitized Solar Cells (pages 3729–3736)

      Santanu Das, P. Sudhagar, Ved Verma, Donghoon Song, Eisuke Ito, Sang Yun Lee, Yong Soo Kang and WonBong Choi

      Version of Record online: 3 AUG 2011 | DOI: 10.1002/adfm.201101191

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      Electrocatalytic activity of graphene for iodine reduction is improved with an increased number of edge-plane-like active carbon sites generated through CF4 reactive-ion plasma treatment. The catalytically induced in-plane charge-transfer charateristics of surface-modified graphene multilayers are explored in use as a counter-electrode in dye-sensitized solar cells.

    7. Ti-Doping to Reduce Conductivity in Bi0.85Nd0.15FeO3 Ceramics (pages 3737–3743)

      Kambiz Kalantari, Iasmi Sterianou, Sarah Karimi, Matthew C. Ferrarelli, Shu Miao, Derek C. Sinclair and Ian M. Reaney

      Version of Record online: 5 AUG 2011 | DOI: 10.1002/adfm.201100191

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      Bi0.85Nd0.15Fe1-yTiyO3 compositions have been fabricated. X-ray and electron diffraction established that Ti-doping promotes the PZ-like structure. The PZ-like structure is retained for samples with y ≤ 0.05. Ti-doping results in a considerable decrease in electrical conductivity and dielectric loss allowing the AFE/PE phase transition to be observed in dielectric as well as DSC measurements.

    8. Oxygen Rich Titania: A Dopant Free, High Temperature Stable, and Visible-Light Active Anatase Photocatalyst (pages 3744–3752)

      Vinodkumar Etacheri, Michael K. Seery, Steven J. Hinder and Suresh C. Pillai

      Version of Record online: 5 AUG 2011 | DOI: 10.1002/adfm.201100301

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      High temperature stable and visible-light active oxygen-rich titania nanoparticles are successfully synthesized through a peroxo-titania route. Increased Ti–O–Ti bond strength, oxygen excess defects and band gap narrowing are identified in these samples. It is proposed that the presence of oxygen excess defects is responsible for the high temperature stability and enhanced visible light photocatalytic activities.

    9. Precisely Designed Gold Nanoparticles by Surface Polymerization – Artificial Molecules as Building Blocks for Novel Materials (pages 3753–3759)

      Stefan Bokern, Katharina Gries, Hans-Helmut Görtz, Volker Warzelhan, Seema Agarwal and Andreas Greiner

      Version of Record online: 8 AUG 2011 | DOI: 10.1002/adfm.201100590

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      A versatile route for the synthesis of a gold nanoparticle with a single functional group is described. The model functional group methylcoumarin is attached to the nanoparticle by a polystyrene chain, resulting in an artificial molecule. This is achieved by a surface polymerization approach and application of a novel telechelic macro-azo-initiator.

    10. A Series of Energy-Transfer Copolymers Derived from Fluorene and 4,7-Dithienylbenzotriazole for High Efficiency Yellow, Orange, and White Light-Emitting Diodes (pages 3760–3769)

      Lianjie Zhang, Sujun Hu, Junwu Chen, Zhenhui Chen, Hongbin Wu, Junbiao Peng and Yong Cao

      Version of Record online: 5 AUG 2011 | DOI: 10.1002/adfm.201100844

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      4,7-Dithienylbenzotriazole, a highly fluorescent chromophore with low concentration quenching effect, is used to construct conjugated polymers with a D-A binary chemical structure for high efficiency yellow, orange, and white light-emitting diodes.

    11. Cyano-Substituted Oligo(p-phenylene vinylene) Single Crystals: A Promising Laser Material (pages 3770–3777)

      Huan Wang, Feng Li, Israel Ravia, Bingrong Gao, Yupeng Li, Vlad Medvedev, Hongbo Sun, Nir Tessler and Yuguang Ma

      Version of Record online: 8 AUG 2011 | DOI: 10.1002/adfm.201100783

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      Organic crystals with excellent light- emission characteristics and high charge- carrier mobility are prepared. They have a high fluorescence quantum yield (up to 95%), an extremely low amplified-spontaneous- emission threshold (23 KW cm−2), and well-balanced bipolar carrier-transport chara­c­teristics (μhole≈ 2.5–5.5 × 10−2 cm2 V−1 s−1; μelectron≈ 0.9–1.3 × 10−2 cm2 V−1 s−1). This material is expected to be a promising candidate for organic laser diodes.

    12. Electromechanical Actuators Based on Graphene and Graphene/Fe3O4 Hybrid Paper (pages 3778–3784)

      Jiajie Liang, Yi Huang, Jiyoung Oh, Mikhail Kozlov, Dong Sui, Shaoli Fang, Ray H. Baughman, Yanfeng Ma and Yongsheng Chen

      Version of Record online: 15 AUG 2011 | DOI: 10.1002/adfm.201101072

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      Works well on paper: Electromechanical actuators are constructed utilizing flexible pristine graphene paper and magnetic graphene/Fe3O4 paper. The resulting magnetic graphene paper presents higher actuation strain than pristine graphene paper and the obtained maximum strain reaches up to 0.1%. The dominant mechanism of the electromechanical actuation for the graphene-based paper involves quantum-chemical and double-layer-electrostatic interactions.

    13. White Organic Light-Emitting Diodes with Evenly Separated Red, Green, and Blue Colors for Efficiency/Color-Rendition Trade-Off Optimization (pages 3785–3793)

      Shuming Chen, Guiping Tan, Wai-Yeung Wong and Hoi-Sing Kwok

      Version of Record online: 3 AUG 2011 | DOI: 10.1002/adfm.201100895

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      Efficient WOLEDs with three evenly separated red, green, and blue peaks are demonstrated in a three-emitter system. WOLEDs doped with a yellowish-green emitter, 1, show a remarkably high efficiency and color-rendering capability compared with Ir(ppy)3, due to the higher efficiency and red-shifted spectrum of 1 relative to that of Ir(ppy)3. These WOLEDs are ideal candidates for display and lighting applications.

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