Advanced Materials

Cover image for Vol. 21 Issue 48

December 28, 2009

Volume 21, Issue 48

Pages 4875–5026

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Frontispiece
    8. Communications
    1. Biocompatible Polymers: Structurally Controlled Bio-hybrid Materials Based on Unidirectional Association of Anisotropic Microparticles with Human Endothelial Cells (Adv. Mater. 48/2009)

      Mutsumi Yoshida, Kyung-Ho Roh, Suparna Mandal, Srijanani Bhaskar, Dongwoo Lim, Himabindu Nandivada, Xiaopei Deng and Joerg Lahann

      Article first published online: 21 DEC 2009 | DOI: 10.1002/adma.200990180

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      Biocompatible anisotropic polymer particles with bipolar affinity towards human endothelial cells are a novel type of building blocks for microstructured biohybrid materials, report Joerg Lahann and co-workers on p. 4920. Functional polarity due to two biologically distinct hemispheres has been achieved by synthesis of anisotropic particles via electro-hydrodynamic co-jetting of two different polymer solutions and subsequent selective surface modification.

  2. Inside Front Cover

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Frontispiece
    8. Communications
    1. Multifunctional Integrated Platforms: Fabrication of Advanced Functional Devices Combining Soft Chemistry with X-ray Lithography in One Step (Adv. Mater. 48/2009)

      Paolo Falcaro, Luca Malfatti, Lisa Vaccari, Heinz Amenitsch, Benedetta Marmiroli, Gianluca Grenci and Plinio Innocenzi

      Article first published online: 21 DEC 2009 | DOI: 10.1002/adma.200990181

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      Combining bottom-up sol–gel assembly with micro- and nanofabrication offers a simple and fast route to develop multifunctional integrated platforms, from microfluidics to microarrays, allowing the chemistry and geometry to be tailored to the application, as reported by Paolo Falcaro, Plinio Innocenzi, and co-workers on p. 4932. The inside cover illustrates different patterns of functionalized surfaces. The background is an example of highly controlled microfluidic interface fabricated combining deep X-rays lithography with sol–gel syntheses.

  3. Contents

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

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Frontispiece
    8. Communications
    1. Gold Nanorods: From Synthesis and Properties to Biological and Biomedical Applications (pages 4880–4910)

      Xiaohua Huang, Svetlana Neretina and Mostafa A. El-Sayed

      Article first published online: 24 JUL 2009 | DOI: 10.1002/adma.200802789

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      Intriguing optical properties suitable for a wide range of applications are exhibited by gold nanorods. In this review, the optical properties are discussed in terms of radiative and nonradiative properties. Various synthetic routes are then outlined, followed by a discussion on nanorod assembly. Current biological and biomedical applications are summarized, with an emphasis on cancer diagnosis and photothermal therapy.

  5. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Frontispiece
    8. Communications
    1. Settling the “Dead Layer” Debate in Nanoscale Capacitors (pages 4911–4914)

      Li-Wu Chang, Marin Alexe, James F. Scott and J. Marty Gregg

      Article first published online: 15 AUG 2009 | DOI: 10.1002/adma.200901756

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      Permittivity peaks in single crystal thin film capacitors are strongly suppressed compared to bulk in the case of Pt/SrTiO3/Pt, but are relatively unaffected in Pt/BaTiO3/Pt structures. This is consistent with the recent suggestion that subtle variations in interfacial bonding between the dielectric and electrode are critical in determining the presence or absence of inherent dielectric “dead layers”.

    2. Three-dimensional Electrical Property Mapping with Nanometer Resolution (pages 4915–4919)

      Alexander Alekseev, Anton Efimov, Kangbo Lu and Joachim Loos

      Article first published online: 3 SEP 2009 | DOI: 10.1002/adma.200901754

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      The conductivity behavior of MWCNT networks within the volume of polymer nanocomposite samples is analyzed with nanometer resolution in all three dimensions. It is demonstrated that close to but above the percolation threshold for electrical conduction most of the MWCNTs do not contribute to the conductive network within the nanocomposite.

    3. Structurally Controlled Bio-hybrid Materials Based on Unidirectional Association of Anisotropic Microparticles with Human Endothelial Cells (pages 4920–4925)

      Mutsumi Yoshida, Kyung-Ho Roh, Suparna Mandal, Srijanani Bhaskar, Dongwoo Lim, Himabindu Nandivada, Xiaopei Deng and Joerg Lahann

      Article first published online: 18 SEP 2009 | DOI: 10.1002/adma.200901971

      Thumbnail image of graphical abstract

      Biocompatible anisotropic polymer particles with bipolar affinity towards human endothelial cells are a novel type of building blocks for microstructured bio-hybrid materials. Functional polarity due to two biologically distinct hemispheres (see figure) has been achieved by synthesis of anisotropic particles via electro-hydrodynamic co-jetting of two different polymer solutions and subsequent selective surface modification.

    4. Controlled Deposition of Highly Ordered Soluble Acene Thin Films: Effect of Morphology and Crystal Orientation on Transistor Performance (pages 4926–4931)

      Christoph W. Sele, B. K. Charlotte Kjellander, Bjoern Niesen, Martin J. Thornton, J. Bas P. H. van der Putten, Kris Myny, Harry J. Wondergem, Armin Moser, Roland Resel, Albert J. J. M. van Breemen, Nick van Aerle, Paul Heremans, John E. Anthony and Gerwin H. Gelinck

      Article first published online: 18 SEP 2009 | DOI: 10.1002/adma.200901548

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      Controlling the morphology of soluble small molecule organic semiconductors is crucial for the application of such materials in electronic devices. Using a simple dip-coating process we systematically vary the film drying speed to produce a range of morphologies, including oriented needle-like crystals. Structural characterization as well as electrical transistor measurements show that intermediate drying velocities produce the most uniformly aligned films.

    5. Fabrication of Advanced Functional Devices Combining Soft Chemistry with X-ray Lithography in One Step (pages 4932–4936)

      Paolo Falcaro, Luca Malfatti, Lisa Vaccari, Heinz Amenitsch, Benedetta Marmiroli, Gianluca Grenci and Plinio Innocenzi

      Article first published online: 18 SEP 2009 | DOI: 10.1002/adma.200901561

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      Deep X-ray lithography combined with sol–gel techniques offers facile fabrication of controlled patterned films. Using sol–gel, different functional properties can be induced; deep X-ray lithography alters the functionality in the exposed regions. Miniaturized devices based on local property changes are easily fabricated: this technique requires no resist, enabling direct patterning of films in a one-step lithographic process.

    6. Electronic and Mechanical Coupling in Bent ZnO Nanowires (pages 4937–4941)

      Xiaobing Han, Liangzhi Kou, Xiaoli Lang, Jianbai Xia, Ning Wang, Rui Qin, Jing Lu, Jun Xu, Zhimin Liao, Xinzheng Zhang, Xudong Shan, Xuefeng Song, Jingyun Gao, Wanlin Guo and Dapeng Yu

      Article first published online: 13 AUG 2009 | DOI: 10.1002/adma.200900956

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      A red shift of the exciton of ZnO nanowires is efficiently produced by bending strain, as demonstrated by a low-temperature (81 K) cathodoluminescence (CL) study of ZnO nanowires bent into L- or S-shapes. The figure shows a nanowire (Fig. a) with the positions of CL measurements marked. The corresponding CL spectra—revealing a peak shift and broadening in the region of the bend—are shown in Figure b.

    7. Exciton–Exciton Interaction and Optical Gain in Colloidal CdSe/CdS Dot/Rod Nanocrystals (pages 4942–4946)

      Michele Saba, Stefan Minniberger, Francesco Quochi, Juergen Roither, Marco Marceddu, Agnieszka Gocalinska, Maksym V. Kovalenko, Dmitri V. Talapin, Wolfgang Heiss, Andrea Mura and Giovanni Bongiovanni

      Article first published online: 31 AUG 2009 | DOI: 10.1002/adma.200901482

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      Exciton–exciton interaction in dot/rod CdSe/CdS nanocrystals has proved to be very sensitive to the shape of nanocrystals, due to the unique band alignment between CdSe and CdS. Repulsive exciton–exciton interaction is demonstrated, which makes CdSe/CdS dot/rods promising gain media for solution-processable lasers, with projected pump threshold densities below 1 kW cm−2 for continuous wave lasing.

    8. Small-Molecule End-Groups of Linear Polymer Determine Cell-type Gene-Delivery Efficacy (pages 4947–4951)

      Joel Sunshine, Jordan J. Green, Kerry P. Mahon, Fan Yang, Ahmed A. Eltoukhy, David N. Nguyen, Robert Langer and Daniel G. Anderson

      Article first published online: 15 AUG 2009 | DOI: 10.1002/adma.200901718

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      End-modified polymers are promising for the nonviral delivery of genes to cancer cells, immune cells, and human stem cells and point to polymer end-groups as regulators for cell-type specificity. A library of polymers has been synthesized and, although some polymers are strong transfection agents overall, for each cell type, a particular polymer is most effective (see image).

  6. Frontispiece

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Frontispiece
    8. Communications
    1. Electrocatalysts: Facile Construction of Pt–Co/CNx Nanotube Electrocatalysts and Their Application to the Oxygen Reduction Reaction (Adv. Mater. 48/2009)

      Shujuan Jiang, Yanwen Ma, Guoqiang Jian, Haisheng Tao, Xizhang Wang, Yining Fan, Yinong Lu, Zheng Hu and Yi Chen

      Article first published online: 21 DEC 2009 | DOI: 10.1002/adma.200990183

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      Pt–Co alloyed nanoparticles can be facilely immobilized onto CNx nanotubes due to the incorporated nitrogen, report Yanwen Ma, Zheng Hu, and co-workers on p. 4953. The as-prepared electrocatalysts exhibit good performance for oxygen reduction reactions in acidic media arising from the high dispersion and alloying effect of Pt–Co nanoparticles, as well as the intrinsic catalytic capacity of CNx nanotubes, which is significant for the development of fuel cells.

  7. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Frontispiece
    8. Communications
    1. Facile Construction of Pt–Co/CNx Nanotube Electrocatalysts and Their Application to the Oxygen Reduction Reaction (pages 4953–4956)

      Shujuan Jiang, Yanwen Ma, Guoqiang Jian, Haisheng Tao, Xizhang Wang, Yining Fan, Yinong Lu, Zheng Hu and Yi Chen

      Article first published online: 15 SEP 2009 | DOI: 10.1002/adma.200900677

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      A straight forward method for immobilizing Pt–Co alloyed nanoparticles onto nitrogen-doped CNx nanotubes is presented (see image). The as-prepared electrocatalysts exhibit good performance for oxygen reduction reaction in acidic medium arising from the high-dispersion and alloying effect of the Pt–Co nanoparticles and the intrinsic catalytic capacity of the CNx nanotubes.

    2. Phosphorescent Light-Emitting Transistors: Harvesting Triplet Excitons (pages 4957–4961)

      Ebinazar B. Namdas, Ben B. Y. Hsu, Zehua Liu, Shih-Chun Lo, Paul L. Burn and Ifor D. W. Samuel

      Article first published online: 24 AUG 2009 | DOI: 10.1002/adma.200900919

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      Phosphorescent light-emitting transistors, in which light emission from singlet and triplet energy levels is harvested using solution-processed materials (see figure), are presented. While a green phosphorescent dendrimer exhibits an external quantum efficiency of 0.45% at 480 cd m−2, a red polymer/phosphorescent small-molecule blend produces a brightness exceeding 30 cd m−2 with a relatively high hole mobility of 2.5 × 10−2 cm2 V−1 s−1.

    3. Gold(I)–Alkanethiolate Nanotubes (pages 4962–4965)

      Yu Xin Zhang and Hua Chun Zeng

      Article first published online: 8 OCT 2009 | DOI: 10.1002/adma.200901677

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      A solution approach to assembling Au(I)-alkanethiolates into nanotube structures at room temperature is presented, in which Au(I) cations and alkanethiolate ligands are coordinated into thin platelet forms that then evolve into an open tubular configuration (see figure). The organic–inorganic hybrid nature of the nanotubes, their ability to be modified, and their high stability make them of interest for practical applications.

    4. Interface Atomic-Scale Structure and its Impact on Quantum Electron Transport (pages 4966–4969)

      Zhongchang Wang, Mitsuhiro Saito, Susumu Tsukimoto and Yuichi Ikuhara

      Article first published online: 3 SEP 2009 | DOI: 10.1002/adma.200900877

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      Local structure, chemistry, and bonding at interfaces often radically affect the properties of materials. A combination of scanning transmission electron microscopy and density functional theory calculations reveals an atomic layer of carbon at a SiC/Ti3SiC2 interface in Ohmic contact to p-type SiC (see image), which results in stronger adhesion, a lowered Schottky barrier, and enhanced transport. This is a key factor to understanding the origin of the Ohmic nature.

    5. Nanometer-Thick Single-Crystal Hexagonal Gd2O3 on GaN for Advanced Complementary Metal-Oxide-Semiconductor Technology (pages 4970–4974)

      Wen Hsin Chang, Chih Hsun Lee, Yao Chung Chang, Pen Chang, Mao Lin Huang, Yi Jun Lee, Chia-Hung Hsu, J. Minghuang Hong, Chiung Chi Tsai, J. Raynien Kwo and Minghwei Hong

      Article first published online: 13 OCT 2009 | DOI: 10.1002/adma.200902101

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      Hexagonal-phase single-crystal Gd2O3 is deposited on GaN in a molecular beam epitaxy system (see image). The dielectric constant is about twice that of its cubic counterpart when deposited on InGaAs or Si. The capacitive effective thickness of 0.5 nm in hexagonal Gd2O3 is perhaps the lowest on GaN-metal-oxide-semiconductor devices. The heterostructure is thermo dynamically stable at high temperatures and exhibits low interfacial densities of states after high-temperature annealing.

    6. Schottky-Gated Probe-Free ZnO Nanowire Biosensor (pages 4975–4978)

      Ping-Hung Yeh, Zhou Li and Zhong Lin Wang

      Article first published online: 17 SEP 2009 | DOI: 10.1002/adma.200902172

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      A nanowire-based nanosensor for detecting biologically and chemically charged molecules that is probe-free and highly sensitive is demonstrated. The device relies on the nonsymmetrical Schottky contact under reverse bias (see figure), and is much more sensitive than the device based on the symmetric ohmic contact. This approach serves as a guideline for designing more practical chemical and biochemical sensors.

    7. Vertical Epitaxial Co5Ge7 Nanowire and Nanobelt Arrays on a Thin Graphitic Layer for Flexible Field Emission Displays (pages 4979–4982)

      Hana Yoon, Kwanyong Seo, Nitin Bagkar, Juneho In, Jeunghee Park, Jaemyung Kim and Bongsoo Kim

      Article first published online: 2 NOV 2009 | DOI: 10.1002/adma.200901972

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      Vertically aligned single-crystalline Co5Ge7 nanowire (NW) and nanobelt arrays are grown on a very thin graphite layer as well as a curved graphite layer with a good epitaxial lattice match. Co5Ge7 NW arrays, thus grown, show very efficient field emission properties comparable to those of carbon nanotubes and may be used for flexible field emission displays in the future.

    8. Solution-Processable Carbazole-Based Conjugated Dendritic Hosts for Power-Efficient Blue-Electrophosphorescent Devices (pages 4983–4986)

      Junqiao Ding, Baohua Zhang, Jianhong Lü, Zhiyuan Xie, Lixiang Wang, Xiabin Jing and Fosong Wang

      Article first published online: 2 NOV 2009 | DOI: 10.1002/adma.200902328

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      A novel class of hosts suitable for solution processing has been developed based on a conjugated dendritic scaffold. By increasing the dendron generation, the highest occupied molecular orbital (HOMO) energy level can be tuned to facilitate hole injection, while the triplet energy remains at a high level, sufficient to host high-energy-triplet emitters. A power-efficient blue-electrophosphorescent device based on H2 (see figure) is presented.

    9. Encapsulated-Dye All-Organic Charged Colored Ink Nanoparticles for Electrophoretic Image Display (pages 4987–4991)

      Sun Wha Oh, Chang Woo Kim, Hwa Jin Cha, Umapada Pal and Young Soo Kang

      Article first published online: 15 OCT 2009 | DOI: 10.1002/adma.200901595

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      Electrophoretic ink nanoparticles with high mobility are successfully fabricated by dispersion polymerization. The color of test cells can be changed by applying a bias voltage, as shown in the figure: the lower row shows the same cells as the upper row but with an applied voltage. These all-organic, encapsulated-dye, electrophoretic ink particles are expected to reduce the fabrication cost of e-ink in electrophoretic image display cells.

    10. Atomic Imaging of Phase Transitions and Morphology Transformations in Nanocrystals (pages 4992–4995)

      Marijn A. van Huis, Neil P. Young, Grégory Pandraud, J. Fredrik Creemer, Daniël Vanmaekelbergh, Angus I. Kirkland and Henny W. Zandbergen

      Article first published online: 20 OCT 2009 | DOI: 10.1002/adma.200902561

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      A newly developed SiN microhotplate allows specimens to be studied at temperatures up to 1000 K at a resolution of 100 picometer (see image). Aberration-corrected transmission electron microscopy has become a commonplace tool to investigate stable crystals; however, imaging transient nanocrystals is much more demanding. Morphological transformations in gold nanoparticles and layer-by-layer sublimation of PbSe nanocrystals is imaged with atomic resolution.

    11. Real-Time Observation and Control of Pentacene Film Growth on an Artificially Structured Substrate (pages 4996–5000)

      Yuki Tsuruma, Abdullah Al-Mahboob, Susumu Ikeda, Jerzy T. Sadowski, Genki Yoshikawa, Yasunori Fujikawa, Toshio Sakurai and Koichiro Saiki

      Article first published online: 2 OCT 2009 | DOI: 10.1002/adma.200901436

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      Suppression of nucleation around a gold electrode during pentacene growth on a SiO2 channel is found by photoemission electron microscopy. Mass flow is driven by the difference between the molecular orientations on SiO2 and gold. The poor connectivity at the channel/electrode boundary causes degradation in the performance of a field-effect transistor, which is found to be improved by self-assembled monolayer treatment on the electrode (see figure; thickness in monolayers (ML)).

    12. High Plasticity and Substantial Deformation in Nanocrystalline NiFe Alloys Under Dynamic Loading (pages 5001–5004)

      Sheng Cheng, Yonghao Zhao, Yazhou Guo, Ying Li, Qiuming Wei, Xun-Li Wang, Yang Ren, Peter K. Liaw, Hahn Choo and Enrique J. Lavernia

      Article first published online: 2 OCT 2009 | DOI: 10.1002/adma.200901991

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      A nanocrystalline (NC) NiFe alloy is presented, in which both highly improved plasticity and strength are achieved by the dynamic-loading-induced deformation mechanisms of de-twinning (that is, reduction of twin density) and significant grain coarsening (see figure). This work highlights potential ingenious avenues to exploit the superior behavior of NC materials under extreme conditions.

    13. A Versatile Synthetic Extracellular Matrix Mimic via Thiol-Norbornene Photopolymerization (pages 5005–5010)

      Benjamin D. Fairbanks, Michael P. Schwartz, Alexandra E. Halevi, Charles R. Nuttelman, Christopher N. Bowman and Kristi S. Anseth

      Article first published online: 7 OCT 2009 | DOI: 10.1002/adma.200901808

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      Step-growth, radically mediated thiol-norbornene photopolymerization is used to create versatile, stimuli-responsive poly(ethylene glycol)-co-peptide hydrogels (see image) The reaction is cytocompatible and allows for the encapsulation of human mesenchymal stem cells with a viability greater than 95%. Cellular spreading is dictated via three-dimensional biochemical photopatterning.

    14. Repairing Polymers Using Oscillating Magnetic Field (pages 5011–5015)

      Cathrin C. Corten and Marek W. Urban

      Article first published online: 1 OCT 2009 | DOI: 10.1002/adma.200901940

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      Repair of physically separated thermoplastic polymers containing γ-Fe2O3 nanoparticles without sacrificing their mechanical properties is achieved by applying an oscillating magnetic field. As γ-Fe2O3 nanoparticles oscillate at the frequency of the magnetic field, localized amorphous flow occur, and a permanent repair of physically separated polymeric films is achieved.

    15. High-Performance Blue/Ultraviolet-Light-Sensitive ZnSe-Nanobelt Photodetectors (pages 5016–5021)

      Xiaosheng Fang, Shenglin Xiong, Tianyou Zhai, Yoshio Bando, Meiyong Liao, Ujjal K. Gautam, Yasuo Koide, Xiaogang Zhang, Yitai Qian and Dmitri Golberg

      Article first published online: 7 OCT 2009 | DOI: 10.1002/adma.200902126

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      Single-crystalline zinc selenide (ZnSe) nanobelts were fabricated via the ethylenediamine (en)-assisted ternary solution technique and subsequent thermal treatment. Individual ZnSe nanobelts were assembled into nanoscale devices (see figure), showing a high spectral selectivity and photocurrent/immediate-decay ratio and a fast time response, justifying effective utilization of the ZnSe nanobelts as blue/UV-light-sensitive photodetectors.

    16. Characterization of Quantum Dot/Conducting Polymer Hybrid Films and Their Application to Light-Emitting Diodes (pages 5022–5026)

      Jeonghun Kwak, Wan Ki Bae, Matthias Zorn, Heeje Woo, Hyunsik Yoon, Jaehoon Lim, Sang Wook Kang, Stefan Weber, Hans-Jürgen Butt, Rudolf Zentel, Seonghoon Lee, Kookheon Char and Changhee Lee

      Article first published online: 1 OCT 2009 | DOI: 10.1002/adma.200902072

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      Quantum dot/conducting polymer hybrid films are used to prepare light-emitting diodes (LEDs). The hybrid films (CdSe@ZnS quantum dots excellently dispersed in a conducting polymer matrix, see figure) are readily prepared by various solution-based processes and are also easily micropatterned. The LEDs exhibit a turn-on voltage of 4 V, an external quantum efficiency greater than 1.5%, and almost pure-green quantum-dot electroluminescence.

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