Advanced Materials

Cover image for Vol. 22 Issue 30

August 10, 2010

Volume 22, Issue 30

Pages 3219–3332

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Progress Report
    6. Communications
    7. Research News
    1. Graphene Synthesis: Controllable Synthesis of Graphene and Its Applications (Adv. Mater. 30/2010)

      Dacheng Wei and Yunqi Liu

      Article first published online: 3 AUG 2010 | DOI: 10.1002/adma.201090099

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      Controllable synthesis of graphene is of great importance for both fundamental research and practical applications. Recent advances in synthesizing graphene with controllable size, shapes, edges, layers, doping, and assembly is detailed in the Progress Report by Dacheng Wei and Yunqi Liu on p. 3225. The report also discusses applications, clarifies existing problems, and looks to the prospects for future development.

  2. Inside Front Cover

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Progress Report
    6. Communications
    7. Research News
    1. Induced Crystallization of Rubrene in Thin-Film Transistors (Adv. Mater. 30/2010)

      Zhefeng Li, Jun Du, Qin Tang, Feng Wang, Jian-Bin Xu, Jimmy C. Yu and Qian Miao

      Article first published online: 3 AUG 2010 | DOI: 10.1002/adma.201090100

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      The inside cover highlights a rubrene molecule with a polarized-light micrograph of a polycrystalline film of rubrene in the background. Polycrystalline thin-film transistors of rubrene can be fabricated by using 6,13-pentacenequinone (PQ) as a template layer and bilayer steps of octadecylphosphonic acid (ODPA) to tune the morphology of PQ. The details of this new strategy are reported by Qian Miao and co-workers on p. 3242.

  3. Contents

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

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Progress Report
    6. Communications
    7. Research News
    1. Controllable Synthesis of Graphene and Its Applications (pages 3225–3241)

      Dacheng Wei and Yunqi Liu

      Article first published online: 23 JUN 2010 | DOI: 10.1002/adma.200904144

      Thumbnail image of graphical abstract

      Controllable synthesis of graphene is of great importance for both foundational researches and practical applications. This Progress Report summarizes recent advances in synthesizing graphene with controlled sizes, shapes, edges, layers, doping, and assembly, discusses their applications, and clarifies the problems and prospects the future development. It will be valuable for the development of research in this field.

  5. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Progress Report
    6. Communications
    7. Research News
    1. Induced Crystallization of Rubrene in Thin-Film Transistors (pages 3242–3246)

      Zhefeng Li, Jun Du, Qin Tang, Feng Wang, Jian-Bin Xu, Jimmy C. Yu and Qian Miao

      Article first published online: 9 JUN 2010 | DOI: 10.1002/adma.201000786

      Thumbnail image of graphical abstract

      The poor crystallinity of rubrene in thin films is an obstacle limiting its practical applications in organic electronics. Here we report a strategy of using 6,13-pentacenequinone (PQ), an easily crystallized insulating molecule, as the template layer to induce the crystallization of rubrene in vacuum-deposited thin film transistors. This strategy relies on the bilayer steps of octadecylphosphonic acid, which play a unique role in modulating the morphology of PQ.

    2. Using Hydrogels to Accommodate Hydrophobic Nanoparticles in Aqueous Media via Solvent Exchange (pages 3247–3250)

      Shuo Bai, Tich-Lam Nguyen, Paul Mulvaney and Dayang Wang

      Article first published online: 1 JUN 2010 | DOI: 10.1002/adma.201000336

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      The solvent exchange of hydrogel particles allows direct loading of hydrophobic inorganic nanoparticles into the gel particles without modification of the particles surfaces and the hydrogel networks. The hydrophobic coating of the loaded nanoparticles is well retained, leading to an excellent chemical stability in water. Simultaneous or stepwise loading of different nanoparticles leads to multifunctional inorganic/organic composite particles.

    3. A Potassium-Selective Quartz Crystal Microbalance Sensor Based on Crown-Ether Functionalized Polymer Brushes (pages 3251–3255)

      Nicolas Schüwer and Harm-Anton Klok

      Article first published online: 9 JUN 2010 | DOI: 10.1002/adma.201000377

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      Benzo-15-crown-5 functionalized polymer brushes prepared via surface-initiated atom transfer radical polymerization are used as the active layer in a potassium-selective quartz crystal microbalance sensor. The polymer brushes allow the selective detection of potassium ions, even in the presence of a large excess of sodium ions and the sensitivity of the sensor can be tuned by varying the brush thickness.

    4. High-Resolution Transmission X-ray Microscopy: A New Tool for Mesoscopic Materials (pages 3256–3259)

      Alexey Bosak, Irina Snigireva, Kirill S. Napolskii and Anatoly Snigirev

      Article first published online: 8 JUN 2010 | DOI: 10.1002/adma.201000173

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      High-resolution transmission X-ray microscopy (HRTXM), combined with X-ray diffraction, is a valuable tool for the volume-specific studies of periodic mesoscopic structures, such as photonic crystals. A case study performed on a prototypical photonic crystal - gem opal - sheds some light on the opals genesis processes.

    5. Interfacial Trap Density-of-States in Pentacene- and ZnO-Based Thin-Film Transistors Measured via Novel Photo-excited Charge-Collection Spectroscopy (pages 3260–3265)

      Kimoon Lee, Min Suk Oh, Sung-jin Mun, Kwang H. Lee, Tae Woo Ha, Jae Hoon Kim, Sang-Hee Ko Park, Chi-Sun Hwang, Byoung H. Lee, Myung M. Sung and Seongil Im

      Article first published online: 1 JUN 2010 | DOI: 10.1002/adma.201000722

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      Direct quantitative mapping of the density-of-states, named the photo-excited charge-collection technique, for the interface traps at the n-ZnO and/or p-pentacene thin-film transistor channel is implemented by using monochromatic photons which are carried by optical fibers and are probed onto thin-film transistors.

    6. A Strategy to Achieve Efficient Dual-Mode Luminescence of Eu3+ in Lanthanides Doped Multifunctional NaGdF4 Nanocrystals (pages 3266–3271)

      Yongsheng Liu, Datao Tu, Haomiao Zhu, Renfu Li, Wenqin Luo and Xueyuan Chen

      Article first published online: 8 JUN 2010 | DOI: 10.1002/adma.201000128

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      A strategy is proposed to fabricate dual-mode luminescent NaGdF4 nanocrystals that are composed of NaGdF4:Yb3+,Tm3+ core and NaGdF4:Eu3+ shell. Intense downconversion via the sensitization of Gd3+ and upconversion luminescence of Eu3+ that is one order of magnitude higher than the triply-doped core only counterparts have been achieved by employing the distinct core/shell nanostructures and double sensitizations of Yb3+ and Tm3+.

    7. Unexplored Thermal Transformation Behavior of Two-Dimensionally Bound Gadolinium Hydroxide Layers: Fabrication of Oriented Crystalline Films of Gadolinium Oxychloride Nanosheets Suitable for the Multicolor Luminescence with Color Tunability (pages 3272–3276)

      Young-su Yoon, Song-Ho Byeon and In Su Lee

      Article first published online: 23 JUN 2010 | DOI: 10.1002/adma.201000539

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      Annealing multilayers of gadolinium hydroxide lead to the growth of gadolinium oxychloride crystallites film through a two-dimensionally confined process. The employment of confined crystallization process create a multilayer film composed of mixed crystallites each doped with different activator ions, such as Eu3+ and Tb3+, which demonstrates a novel method of fabricating robust and semi-transparent inorganic thin films with multicolor emission capacity and color tunability.

    8. Flexible, Polymer-Supported, Si Wire Array Photoelectrodes (pages 3277–3281)

      Joshua M. Spurgeon, Shannon W. Boettcher, Michael D. Kelzenberg, Bruce S. Brunschwig, Harry A. Atwater and Nathan S. Lewis

      Article first published online: 29 JUN 2010 | DOI: 10.1002/adma.201000602

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      Arrays of oriented, crystalline Si wires are transferred into flexible, transparent polymer films. The polymer-supported Si wire arrays in liquid-junction photoelectrochemical cells yield current-potential behavior similar to the Si wires attached to the brittle growth substrate. These systems offer the potential for attaining high solar energy-conversion efficiencies using modest diffusion length, readily grown, crystalline Si in a flexible, processable form.

    9. Photoactive Gate Dielectrics (pages 3282–3287)

      Qian Shen, Linjun Wang, Song Liu, Yang Cao, Lin Gan, Xuefeng Guo, Michael L. Steigerwald, Zhigang Shuai, Zhongfan Liu and Colin Nuckolls

      Article first published online: 15 JUN 2010 | DOI: 10.1002/adma.201000471

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      Ageneral methodology towards stable high-performance photocontrollable organic thin-film transistors (OTFTs) by using photochromic spiropyrans (SP) combined with polymethyl methacrylate (PMMA) as a photoactive gate dielectric is reported. Capacitance and mobility transitions are demonstrated theoretically and experimentally when the SP molecules undergo their documented reversible photoisomerization. This universal strategy of incorporating molecular functionalities into OTFTs offers attractive new prospects for the development of molecular devices with tailored electronic and other properties.

    10. Surface Functionalization of Epoxy-Resist- Based Microcantilevers with Iron Oxide Nanocrystals (pages 3288–3292)

      C. Ingrosso, E. Sardella, S. Keller, S. Dohn, M. Striccoli, A. Agostiano, A. Boisen and M. L. Curri

      Article first published online: 1 JUN 2010 | DOI: 10.1002/adma.200904013

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      A functionalization procedure is integrated in the fabrication of micromechanical SU-8 cantilevers in order to chemically bind organic-capped Fe2O3 NCs at the photoresist surface, under visible light, ambient atmosphere and room temperature. The achieved highly interconnected NC multilayer network is demonstrated an active layer for real-time detection of acetone vapor molecules.

    11. Accounting for Interference, Scattering, and Electrode Absorption to Make Accurate Internal Quantum Efficiency Measurements in Organic and Other Thin Solar Cells (pages 3293–3297)

      George F. Burkhard, Eric T. Hoke and Michael D. McGehee

      Article first published online: 31 MAY 2010 | DOI: 10.1002/adma.201000883

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      Accurately measuring internal quantum efficiency requires knowledge of absorption in the active layer of a solar cell. The experimentally accessible total absorption includes significant contributions from the electrodes and other non-active layers. We suggest a straightforward method for calculating the active layer contribution that minimizes error by subtracting optically-modeled electrode absorption from experimentally measured total absorption.

    12. Low-Voltage UV-Electroluminescence from ZnO-Nanowire Array/p-GaN Light-Emitting Diodes (pages 3298–3302)

      Oleg Lupan, Thierry Pauporté and Bruno Viana

      Article first published online: 1 JUN 2010 | DOI: 10.1002/adma.201000611

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      UV LEDs: The fabrication of an ITO/ZnO-nanowires/p-GaN/In-Ga LED structure is reported with an active emitting layer made of high-quality epitaxial ZnO grown electrochemically from a solution at low temperature (85 °C). A narrow ultra-violet electroluminescence centered at 397 nm is obtained at room temperature starting at an applied forward bias of 4.4 V (see figure). The emission is of high brightness and stable at low applied voltages beyond 6 V.

    13. Photo-Fabrication of Titania Hybrid Films with Tunable Hierarchical Structures and Stimuli-Responsive Properties (pages 3303–3306)

      Masahide Takahashi, Masafumi Inoue, Rie Ihara, Toshinobu Yoko, Takashi Nemoto, Seiji Isoda, Luca Malfatti, Stefano Costacurta and Plinio Innocenzi

      Article first published online: 17 MAY 2010 | DOI: 10.1002/adma.201000619

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      Photo‒fabrication of surface‒wrinkled hybrid organic‒inorganic composite films containing TiO2 nanoparticles stabilized with CTA+ and PVP allows the preparation of tunable hierarchical structures with environmentally responsive properties. With changes in relative humidity, the film swells by absorbing water and smooths out the wrinkles at the micrometer scale; this response is reversible and wet‒dry cycles can be run.

    14. Imaging Buried Molecules: Fullerenes Under Graphene (pages 3307–3310)

      Andrei Varykhalov, Wolfgang Gudat and Oliver Rader

      Article first published online: 9 JUN 2010 | DOI: 10.1002/adma.201000695

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      The capability of scanning tunneling microscopy to image individual molecules intercalated under graphene is demonstrated for fullerenes. The C60 molecules become visible through the graphene carpet grown on Ni(111) due to an extremely strong bias-dependent spectroscopic contrast. Its origin is a blocking of the chemical interaction between graphene and its substrate by the fullerenes.

    15. Tuning Energy Levels of Electron-Transport Materials by Nitrogen Orientation for Electrophosphorescent Devices with an ‘Ideal’ Operating Voltage (pages 3311–3316)

      Shi-Jian Su, Hisahiro Sasabe, Yong-Jin Pu, Ken-ichi Nakayama and Junji Kido

      Article first published online: 15 JUN 2010 | DOI: 10.1002/adma.200904249

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      A series of 1,3,5-triazine-core-containing electron-transport materials (ETMs) are reported as an undoped electron-transport layer (ETL), whose energy levels can be tuned by introducing pyridine rings on the periphery of the molecule and also orientation of nitrogen. An unprecedented low operating voltage of 2.42 V, corresponding to the emitting photon energy (hv), was achieved for the fac-tris(2-phenylpyridine) iridium (Ir(PPy)3) based green phosphorescent OLEDs at 100 cd m−2 without consumption of their efficiency. Moreover, the threshold voltage for electroluminescence can be even 0.1 ∼ 0.2 V lower than the minimum value of hv/e.

    16. One-Step Solvothermal Synthesis of a Carbon@TiO2 Dyade Structure Effectively Promoting Visible-Light Photocatalysis (pages 3317–3321)

      Li Zhao, Xiufang Chen, Xinchen Wang, Yuanjian Zhang, Wei Wei, Yuhan Sun, Markus Antonietti and Maria-Magdalena Titirici

      Article first published online: 23 JUN 2010 | DOI: 10.1002/adma.201000660

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      A C@TiO2 visible-light “dyade”-like structure, catalytically active over the whole visible-light spectrum, has been produced in a one-step low-temperature solvothermal process.

    17. Controllable Synthesis of Metal–Organic Frameworks: From MOF Nanorods to Oriented MOF Membranes (pages 3322–3326)

      Yan-Shuo Li, Helge Bux, Armin Feldhoff, Guo-Ling Li, Wei-Shen Yang and Jürgen Caro

      Article first published online: 8 JUN 2010 | DOI: 10.1002/adma.201000857

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      Tailoring of the crystal size and morphology of metal–organic framework (MOF) materials and manipulation of MOF films is possible by the solvothermal synthesis route introduced here. A c-out-of-plane ZIF-7 membrane (see figure) is obtained through evolutionary selection in a van der Drift–type growth originating from randomly oriented seed layers. Highly oriented MOF thin films are important as molecular sieve membranes.

  6. Research News

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Progress Report
    6. Communications
    7. Research News
    1. Supersensitive, Fast-Response Nanowire Sensors by Using Schottky Contacts (pages 3327–3332)

      Youfan Hu, Jun Zhou, Ping-Hung Yeh, Zhou Li, Te-Yu Wei and Zhong Lin Wang

      Article first published online: 31 MAY 2010 | DOI: 10.1002/adma.201000278

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      Schottky contacts can be used to achieve supersensitive and fast-response nanowire-based nanosensors. The idea is illustrated for several platforms: UV sensors, biosensors, and gas sensors. The enormous improvement in sensitivity of up to 5 orders of magnitude shows that an effective usage of the Schottky contact can be very beneficial to the sensitivity of nanosensors.

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