Advanced Materials

Cover image for Vol. 20 Issue 20

October 17, 2008

Volume 20, Issue 20

Pages 3779–3966

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Research News
    8. Index
    1. Cover Picture: High-Speed Color-Switching Silicon LEDs (Adv. Mater. 20/2008)

      Sulan Kuai and Al Meldrum

      Article first published online: 17 OCT 2008 | DOI: 10.1002/adma.200890081

      Thumbnail image of graphical abstract

      The cover shows a time-sequence illustration of a color-switching silicon LED. The emission is switching from infrared (false color, purple) to visible (near real color, orange) on a vertically winding time axis. The upper left image represents a single micro-LED switching in time between the visible, infrared, and off states. Further details can be found in the article on p. 3844 by Al Meldrum and Sulan Kuai.

  2. Inside Front Cover

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Research News
    8. Index
    1. Inside Front Cover: Long-Living Light-Emitting Electrochemical Cells – Control through Supramolecular Interactions (Adv. Mater. 20/2008)

      Henk J. Bolink, Eugenio Coronado, Rubén D. Costa, Enrique Ortí, Michele Sessolo, Stefan Graber, Kevin Doyle, Markus Neuburger, Catherine E. Housecroft and Edwin C. Constable

      Article first published online: 17 OCT 2008 | DOI: 10.1002/adma.200890082

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      Light-emitting electrochemical cells (LECs) based on ionic transition-metal complexes are among the simplest electroluminescent devices as they use only one active component in a mono-or bi-layer architecture, operate with air-stable electrodes and are prepared using solution-based technologies. To date, the most important drawback of these molecular devices is their short lifetimes, limited to a few days. By using an ionic iridium(III) complex containing supramolecularly-interacting ligands able to form a caged structure, Henk Bolink and co-workers show on p. 3910 that the lifetime of LECs can be increased to more than 3 000 hours paving the way for low-cost and large-area lighting and signing applications.

  3. Contents

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Research News
    8. Index
  4. Review

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Research News
    8. Index
    1. Recent Applications of Conjugated Polyelectrolytes in Optoelectronic Devices (pages 3793–3810)

      Corey V. Hoven, Andres Garcia, Guillermo C. Bazan and Thuc-Quyen Nguyen

      Article first published online: 25 SEP 2008 | DOI: 10.1002/adma.200800533

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      Conjugated polyelectrolytes comprise an electronically delocalized backbone with pendant groups bearing ionic functionalities. Important new developments regarding their incorporation into emerging technologies have recently appeared. This article provides an overview of recent studies concerning the basic properties of conjugated polyelectrolytes as a function of molecular structure, and of optoelectronic devices containing conjugated polyelectrolytes as essential functional components.

  5. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Research News
    8. Index
    1. Morphological Control of Single-Crystalline Silicon Nanowire Arrays near Room Temperature (pages 3811–3815)

      Chia-Yun Chen, Chi-Sheng Wu, Chia-Jen Chou and Ta-Jen Yen

      Article first published online: 1 SEP 2008 | DOI: 10.1002/adma.200702788

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      Control of the orientation, diameter, and length of silicon nanowires (SiNWs) is achieved in large-scale single-crystalline SiNW arrays fabricated by a statistical electroless metal deposition technique. Taguchi methods are employed to optimize the diameter control and to understand the influence of all processing factors on the growth. The 〈100〉 directions are found to be the preferred crystallographic orientation of the growing SiNWs (see figure).

    2. Nitrogen-doped Lamellar Niobic Acid with Visible Light-responsive Photocatalytic Activity (pages 3816–3819)

      Xiukai Li, Naoki Kikugawa and Jinhua Ye

      Article first published online: 1 SEP 2008 | DOI: 10.1002/adma.200702975

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      By a facile solid-state reaction method with urea as a nitrogen source, HNb3O8 could be successfully doped with nitrogen without destroying its layered structure. It was found that the intercalation of urea not only helps to stabilize the layered structure of HNb3O8 during the heating process, but also facilitates an easier doping of nitrogen into the solid acid. The nitrogen-doped HNb3O8 photocatalyst so-obtained shows fairly good activity under visible light irradiation.

    3. A Phosphorescent Ir(III) Complex for Selective Fluoride Ion Sensing with a High Signal-to-Noise Ratio (pages 3820–3826)

      Youngmin You and Soo Young Park

      Article first published online: 1 SEP 2008 | DOI: 10.1002/adma.200702667

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      A highly phosphorescent Ir(III) complex, containing a dimesitylboryl group in its coordinative phenylpyridine ligand, exhibited a phosphorescence colorimetric and ratiometric fluoride ion-selective sensing behavior and enabled facile signal purification through time-gated acquisition. Poly(methylmethacrylate) films doped with the Ir(III) complex were used to successfully detect fluoride ion in aqueous media.

    4. Pliant Epitaxial Ionic Oxides on Silicon (pages 3827–3831)

      Dmitry Kukuruznyak, Harald Reichert, Kenji Ohmori, Parhat Ahmet and Toyohiro Chikyow

      Article first published online: 9 SEP 2008 | DOI: 10.1002/adma.200702234

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      Pliant covalent-network SiO2 must be replaced by a high-dielectric constant (high-k) compound in silicon transistor gates. The known high-k dielectrics; however, are all rigid ionic crystals. We have discovered a new class of high-k oxides that emulates pliancy of the native SiO2 and self-constructs epitaxial films on silicon after annealing at ∼1030°C.

    5. Enhancing the Toxicity of Cancer Chemotherapeutics with Gold Nanorod Hyperthermia (pages 3832–3838)

      Tanya S. Hauck, Travis L. Jennings, Tetyana Yatsenko, J. Carl Kumaradas and Warren C. W. Chan

      Article first published online: 24 SEP 2008 | DOI: 10.1002/adma.200800921

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      The heat produced by optically excited gold nanorods is used to augment the chemotherapeutic agent cisplatin in killing tumor cells. This combined therapy kills 78% more cells than cisplatin alone, suggesting a synergistic interaction between these treatments.

    6. Transparent Inverted Organic Light-Emitting Diodes with a Tungsten Oxide Buffer Layer (pages 3839–3843)

      Jens Meyer, Thomas Winkler, Sami Hamwi, Stephan Schmale, Hans-Hermann Johannes, Thomas Weimann, Peter Hinze, Wolfgang Kowalsky and Thomas Riedl

      Article first published online: 16 SEP 2008 | DOI: 10.1002/adma.200800949

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      Highly efficient transparent OLEDs are demonstrated. A novel WO3 buffer layer protects the organics during the sputter deposition of the top ITO electrode. L–J–V and SIMS analysis yield optimized devices with a 60 nm thick WO3 layer. Very high efficiencies of 38 cdA−1 and 30 lm W−1 at 100 cd m−2 are obtained. At the same time the transmittance throughout the visible part of the spectrum exceeds 75%.

    7. High-Speed Color-Switching Silicon LEDs (pages 3844–3847)

      Sulan Kuai and Al Meldrum

      Article first published online: 22 SEP 2008 | DOI: 10.1002/adma.200801060

      Thumbnail image of graphical abstract

      Silicon-based light-emitting devices can be produced by patterning commercial silicon wafers into microscale metal–insulator–semiconductor diodes. In this image, a silicon LED switches from IR (false color – left) to off (middle) to visible (right).

    8. Physics of Nanomechanical Biosensing on Cantilever Arrays (pages 3848–3853)

      Maria L. Sushko, John H. Harding, Alexander L. Shluger, Rachel A. McKendry and Moyu Watari

      Article first published online: 22 SEP 2008 | DOI: 10.1002/adma.200801344

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      A quantitative model of nanomechanical biosensing, which links mesoscopic response of the BioMEMS device to specific chemical, elastic and entropic properties at the nanoscale, is reported (see figure). These concepts envision novel surface chemistries and device geometries ‘in silico’ with significantly improved detection sensitivities for nanomechanical biosensing.

    9. Hierarchical Self-Assembly of Edge-On Nanocolumnar Superstructures of Large Disc-Like Molecules (pages 3854–3858)

      Luc Piot, Camille Marie, Xinliang Feng, Klaus Müllen and Denis Fichou

      Article first published online: 24 SEP 2008 | DOI: 10.1002/adma.200801428

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      Long uniaxialedge-onnanocolumnar stacks of dodecyl-substituted hexa-peri-hexabenzocoronene grow spontaneously at the liquid/solid interface as a result of a hierarchical self-assembly process. Supramolecular multilayered architectures as complex as {HOPG/face-on/edge-on/edge-on} and {HOPG/face-on/edge-on/face-on} are produced, paving the way towards future applications in organic nanodevices.

    10. Plasmonic Building Blocks for Magnetic Molecules in Three-Dimensional Optical Metamaterials (pages 3859–3865)

      Na Liu, Liwei Fu, Stefan Kaiser, Heinz Schweizer and Harald Giessen

      Article first published online: 9 SEP 2008 | DOI: 10.1002/adma.200702950

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      A five-layer fishnet magnetic metamaterial with the definition of artificial ‘magnetic atoms’ is highlighted. The solid black circle represents the circular current excited between a double-wire pair. The red arrows in the figure denote the magnetic moments associated with the ‘magnetic atoms’. The coupling between these ‘magnetic atoms’ leads to the concept of plasmonic building blocks for magnetic molecules in 3D optical metamaterials.

    11. Ultra-Low Energy Threshold for Cancer Photothermal Therapy Using Transferrin-Conjugated Gold Nanorods (pages 3866–3871)

      Jing Liang Li, Daniel Day and Min Gu

      Article first published online: 22 SEP 2008 | DOI: 10.1002/adma.200800941

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      Transferrin-conjugated gold nanorods are used for efficient targeting, two-photon imaging, and photothermal therapy of cancer cells under both linearly and circularly polarized femtosecond illuminations. The results show that the effective laser energy threshold for therapy can be reduced to around 10 mJ cm−2, which is one order of magnitude lower than the medical safety standard level.

    12. Influence of Binding-Site Density in Wet Bioadhesion (pages 3872–3876)

      Jijun Wang, Muhammad Nawaz Tahir, Michael Kappl, Wolfgang Tremel, Nadine Metz, Matthias Barz, Patrick Theato and Hans-Jürgen Butt

      Article first published online: 20 OCT 2008 | DOI: 10.1002/adma.200801140

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      The biomimetic adhesion polymer poly[(dopamine acrylamide)-co-(butylamine acrylamide)] shows strong adhesion even in aqueous environments. With single-molecule atomic force microscopy experiments, we show that the adhesion force does not depend on the density of the functional dopamine groups.

    13. Electrostatic Co-Assembly of Iron Oxide Nanoparticles and Polymers: Towards the Generation of Highly Persistent Superparamagnetic Nanorods (pages 3877–3881)

      J. Fresnais, J.-F. Berret, B. Frka-Petesic, O. Sandre and R. Perzynski

      Article first published online: 5 SEP 2008 | DOI: 10.1002/adma.200800846

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      We report a protocol that allowed us to fabricate nanoparticle aggregates from anionically coated 7 nm iron oxide nanocrystals and cationic-neutral block copolymers. The control of electrostatics resulted in the elaboration of spherical clusters or of highly persistent nanostructured rods, with lengths between 1 and 50 µm (see figure). The rods were shown to be superparamagnetic.

    14. Synthesis of Complex Au/Ag Nanorods by Controlled Overgrowth (pages 3882–3886)

      Kyoungweon Park and Richard A. Vaia

      Article first published online: 5 SEP 2008 | DOI: 10.1002/adma.200800613

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      Hybrid Au/Ag nanorods (NRs) are synthesized by initiating secondary growth on premade Au NRs stabilized with tightly binding binary surfactants. By utilizing long, thin Au NRs and carefully manipulating the reduction conditions, Au/Ag hybrid nanostructures are achieved either in the form of Ag-capped tips or as a uniform overgrowth of Ag.

    15. Vacuum-Processed Polyaniline–C60 Organic Field Effect Transistors (pages 3887–3892)

      Mihai Irimia-Vladu, Nenad Marjanovic, Angela Vlad, Alberto Montaigne Ramil, Gerardo Hernandez-Sosa, Reinhard Schwoödiauer, Siegfried Bauer and Niyazi Serdar Sariciftci

      Article first published online: 9 SEP 2008 | DOI: 10.1002/adma.200801024

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      Vacuum processed emeraldine base polyaniline is employed as gate insulating layer in organic field effect transistors. Both polyaniline and the small molecule semiconductor (i.e., C60) layers are successively evaporated without breaking the vacuum in the evaporation chamber, suggesting the applicability of evaporation processes as industrial route for the fabrication of OFETs.

    16. Highly Stable Localized Plasmon Transducers Obtained by Thermal Embedding of Gold Island Films on Glass (pages 3893–3899)

      Tanya Karakouz, Alexander B. Tesler, Tatyana A. Bendikov, Alexander Vaskevich and Israel Rubinstein

      Article first published online: 1 SEP 2008 | DOI: 10.1002/adma.200703092

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      Strongly bound and highly stable gold island films on glass are obtained by a simple, one-step preparation procedure (see figure) based on high-temperature annealing and partial embedding of gold nanostructures evaporated on glass, providing stable and effective localized plasmon transducers.

    17. Controlled Growth of Pt Nanowires on Carbon Nanospheres and Their Enhanced Performance as Electrocatalysts in PEM Fuel Cells (pages 3900–3904)

      Shuhui Sun, Frédéric Jaouen and Jean-Pol Dodelet

      Article first published online: 22 SEP 2008 | DOI: 10.1002/adma.200800491

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      Single-crystal Pt nanowires are directly grown on carbon nanospheres via a simple chemical route, at room temperature in aqueous solution. The growth density and length of Pt nanowires on the carbon support can be easily modulated. Of interest for PEM fuel cell application, such Pt nanowire/C composites show enhanced catalytic activity for the oxygen reduction reaction compared with a state-of-the-art Pt/C catalyst made of Pt nanoparticles.

    18. A Gecko-Inspired Reversible Adhesive (pages 3905–3909)

      Michael T. Northen, Christian Greiner, Eduard Arzt and Kimberly L. Turner

      Article first published online: 5 SEP 2008 | DOI: 10.1002/adma.200801340

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      A synthetic, fully reversible, switchable, gecko-inspired adhesive is presented. The biomimetic system is composed of flexible nickel paddles coated with aligned vertical polymeric nanorods. When subjected to a magnetic field, adhesion decreases by a factor of 40. The ability of the adhesive to controllably stick and release from a surface could enable technologies from ubiquitous latching systems to climbing microrobotics.

    19. Long-Living Light-Emitting Electrochemical Cells – Control through Supramolecular Interactions (pages 3910–3913)

      Henk J. Bolink, Eugenio Coronado, Rubén D. Costa, Enrique Ortí, Michele Sessolo, Stefan Graber, Kevin Doyle, Markus Neuburger, Catherine E. Housecroft and Edwin C. Constable

      Article first published online: 1 SEP 2008 | DOI: 10.1002/adma.200801322

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      Light-emitting electrochemical cells with lifetimes surpassing 3000 hours at an average luminance of 200 cd m−2 are obtained with an ionic iridium(III) complex conveniently designed to form a supramolecularly caged structure.

    20. Bioinspired Self-Cleaning Antireflection Coatings (pages 3914–3918)

      Wei-Lun Min, Bin Jiang and Peng Jiang

      Article first published online: 27 AUG 2008 | DOI: 10.1002/adma.200800791

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      Subwavelength-structured silicon and glass pillar arrays that mimic both the unique functionalities of antireflective moth eyes and superhydrophobic cicada wings have been fabricated by a simple and scalable colloidal templating technique. The resulting biomimetic multifunctional coatings have important technological applications ranging from solar cells to flat panel displays.

    21. Elastic Properties and Buckling of Silicon Nanowires (pages 3919–3923)

      Cheng-Lun Hsin, Wenjie Mai, Yudong Gu, Yifan Gao, Chi-Te Huang, Yuzi Liu, Lih-Juann Chen and Zhong-Lin Wang

      Article first published online: 3 SEP 2008 | DOI: 10.1002/adma.200800485

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      The ultrahigh flexibility and strong mechanical toughness of silicon nanowires (SiNWs) is demonstrated using manipulation and measurements on buckled SiNWs in a scanning electron microscope (see figure). The experimental data and calculated results show that the nanowire can bear a large strain (1.5%), much more than the bulk material, while the elastic constant of the NW is similar to that of the bulk.

    22. Organic Photovoltaic Devices Based on a Novel Acceptor Material: Graphene (pages 3924–3930)

      Zunfeng Liu, Qian Liu, Yi Huang, Yanfeng Ma, Shougen Yin, Xiaoyan Zhang, Wei Sun and Yongsheng Chen

      Article first published online: 20 OCT 2008 | DOI: 10.1002/adma.200800366

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      Solution-processable functionalized graphene (SPFGraphene, see figure) is used as the electron-accepting material in organic photovoltaic (OPV) devices for the first time, showing that it is a competitive alternative. The fabrication and performance of bulk heterojunction OPV devices with SPFGraphene and different donor materials is presented, together with the impact of post-fabrication annealing.

    23. Electronic Current Transport through Molecular Monolayers: Comparison between Hg/Alkoxy and Alkyl Monolayer/Si(100) Junctions (pages 3931–3936)

      Florent Thieblemont, Oliver Seitz, Ayelet Vilan, Hagai Cohen, Eric Salomon, Antoine Kahn and David Cahen

      Article first published online: 22 SEP 2008 | DOI: 10.1002/adma.200800659

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      Electronic current transport through alkoxy and alkyl monolayer-based junctions is presented. Monolayers are prepared on n-Si(100) with sufficiently high quality to reliably investigate the actual molecular effect of each monolayer on their current–voltage characteristics. The results show that extending the Si-binding chemistry from alkene to alcohol is feasible, which should significantly facilitate preparation of monolayers with modified molecules.

    24. High-Performance, Nondiffusive Crosslinked Polymers for Holographic Data Storage (pages 3937–3941)

      Anzar Khan, Galen D. Stucky and Craig J. Hawker

      Article first published online: 20 OCT 2008 | DOI: 10.1002/adma.200800776

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      High-performance crosslinked polymeric materials for 3D data storage are described. Their performance is based on photoisomerization of Dewar benzene derivatives, and they exhibit remarkable information storage properties including excellent photosensitivity, high data-storage capacity, good dimensional stability, and significant shelf- and archival-lifetimes.

    25. A General Method for the Anodic Formation of Crystalline Metal Oxide Nanotube Arrays without the Use of Thermal Annealing (pages 3942–3946)

      Nageh K. Allam, Karthik Shankar and Craig A. Grimes

      Article first published online: 22 SEP 2008 | DOI: 10.1002/adma.200800815

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      Crystalline TiO2 nanotube arrays are synthesized using a two-step process. The Ti foil sample is first treated with an oxidizing agent-containing electrolyte, either H2O2 or (NH4)2S2O8, then anodized at constant voltage in a fluoride-containing electrolyte. The resulting films are directly used for water photoelectrolysis and in dye-sensitized solar cells, see figure.

    26. Highly Efficient Carbazole-π-Dimesitylborane Bipolar Fluorophores for Nondoped Blue Organic Light-Emitting Diodes (pages 3947–3952)

      Shin-Lei Lin, Li-Hsin Chan, Rong-Ho Lee, Ming-Yu Yen, Wen-Jang Kuo, Chin-Ti Chen and Ru-Jong Jeng

      Article first published online: 22 SEP 2008 | DOI: 10.1002/adma.200801023

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      Highly efficient blue emitters based on the Lewis acid–base carbazole-π-dimesitylborane framework are synthesized and characterized. Among four bipolar blue fluorophores, the nondoped OLED fabricated with CzThB exhibits the best performance blue electroluminescence with CIEx, y (0.13,0.21), maximum electroluminance of 28 300 cd m−2 and external quantum efficiency of 6.9%.

  6. Research News

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Research News
    8. Index
    1. Protein–Polymer Hybrid Amphiphiles (pages 3953–3957)

      A. (Ton) J. Dirks, Roeland J. M. Nolte and Jeroen J. L. M. Cornelissen

      Article first published online: 22 SEP 2008 | DOI: 10.1002/adma.200801383

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      Protein–polymer hybrid amphiphiles self-assemble in a similar way as low molecular weight surfactants (see figure). These assemblies are equipped with built-in (bio)functionality because of the protein head groups, and therefore, applications as functional nanometer-sized materials can be foreseen. In this Research News article we provide an overview of the recent advances in the relatively young field of protein–polymer hybrid amphiphiles.

    2. Solar Cells, Photodetectors, and Optical Sources from Infrared Colloidal Quantum Dots (pages 3958–3964)

      Edward H. Sargent

      Article first published online: 20 OCT 2008 | DOI: 10.1002/adma.200801153

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      Solution-processed optoelectronic devices can be fabricated based on infrared colloidal quantum dots. Ultrasensitive photodetectors, infrared-collecting solar cells, and communications-wavelength light sources based on solution-processed, size-effect-tuned nanoparticles are reviewed in this article.

  7. Index

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Research News
    8. Index

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