Advanced Materials

Cover image for Vol. 24 Issue 16

April 24, 2012

Volume 24, Issue 16

Pages 2061–2211

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Review
    7. Communications
    1. Photorefractive Materials: Innovative Sensitizer DiPBI Outperforms PCBM (Adv. Mater. 16/2012) (page 2061)

      Katharina Ditte, Wei Jiang, Thomas Schemme, Cornelia Denz and Zhaohui Wang

      Article first published online: 17 APR 2012 | DOI: 10.1002/adma.201290089

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      The cover illustrates a photorefractive composite-based, white light, multibeam coupler, wherein the novel broad-band sensitizer DiPBI displaces the widely used PCBM. As the absorption spectrum of DiPBI stretches over the whole range of visible light, operation at any desired wavelength is possible. This essential advantage over PCBM makes the new compound a promising candidate for optical computing and colored 3D displays. On page 2104, Z. Wang and co-workers present this significant step towards the realization of such devices.

  2. Inside Front Cover

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Review
    7. Communications
    1. Photofluidization: Directional Photofluidization Lithography: Micro/Nanostructural Evolution by Photofluidic Motions of Azobenzene Materials (Adv. Mater. 16/2012) (page 2062)

      Seungwoo Lee, Hong Suk Kang and Jung-Ki Park

      Article first published online: 17 APR 2012 | DOI: 10.1002/adma.201290090

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      On page 2069, S. Lee, J.-K. Park, and co-workers review progress in micro/nanostructural evolution by the directional photofluidization of azo-materials (collectively known as directional photofluidization lithography). These materials are nearly impossible to obtain with other existing lithographic methods. Azo-materials become fluidized when irradiated, in a manner such that structural defects such as line-edge roughness are greatly reduced. More importantly, the unique characteristics of the directionality of such photofluidization provide unprecedented ways for the deterministic and large-area shaping of micro/nanostructures.

  3. Masthead

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Review
    7. Communications
    1. Masthead: (Adv. Mater. 16/2012)

      Article first published online: 17 APR 2012 | DOI: 10.1002/adma.201290091

  4. Contents

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Review
    7. Communications
    1. Contents: (Adv. Mater. 16/2012) (pages 2063–2068)

      Article first published online: 17 APR 2012 | DOI: 10.1002/adma.201290088

  5. Review

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Review
    7. Communications
    1. Directional Photofluidization Lithography: Micro/Nanostructural Evolution by Photofluidic Motions of Azobenzene Materials (pages 2069–2103)

      Seungwoo Lee, Hong Suk Kang and Jung-Ki Park

      Article first published online: 27 MAR 2012 | DOI: 10.1002/adma.201104826

      Thumbnail image of graphical abstract

      Directional photofluidization enables structural evolution toward high resolution with various shapes, unprecedented complexity, and lower edge-roughness by virtue of the reversible and directional motions of azo-materials (a path-changing approach). This reversible and fluidic evolution of micro/nanostructures provides both micro/nanostructural designs beyond those that can be achieved using established lithographic approaches and excellent motivation for novel photonic properties.

  6. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Review
    7. Communications
    1. Innovative Sensitizer DiPBI Outperforms PCBM (pages 2104–2108)

      Katharina Ditte, Wei Jiang, Thomas Schemme, Cornelia Denz and Zhaohui Wang

      Article first published online: 26 MAR 2012 | DOI: 10.1002/adma.201104381

      Thumbnail image of graphical abstract

      A new photorefractive (PR) material sensitized with a novel functional unit DiPBI is prepared based on the guest/host approach. This unique mixture exhibits strong absorption in the whole range of visible light. Moreover, the photorefractive performance as well as PR speed is improved by far compared to the widely used sensitizer PCBM.

    2. High-Performance LiNi0.5Mn1.5O4 Spinel Controlled by Mn3+ Concentration and Site Disorder (pages 2109–2116)

      Jie Xiao, Xilin Chen, Peter V. Sushko, Maria L. Sushko, Libor Kovarik, Jijun Feng, Zhiqun Deng, Jianming Zheng, Gordon L. Graff, Zimin Nie, Daiwon Choi, Jun Liu, Ji-Guang Zhang and M. Stanley Whittingham

      Article first published online: 19 MAR 2012 | DOI: 10.1002/adma.201104767

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      The complex correlation between Mn3+ ions and the disordered phase in the lattice structure of high voltage spinel, and its effect on the charge transport properties, are revealed through a combination of experimental study and computer simulations. Superior cycling stability is achieved in LiNi0.45Cr0.05Mn1.5O4 with carefully controlled Mn3+ concentration. At 250th cycle, capacity retention is 99.6% along with excellent rate capabilities.

    3. Elastomer Surfaces with Directionally Dependent Adhesion Strength and Their Use in Transfer Printing with Continuous Roll-to-Roll Applications (pages 2117–2122)

      Sang Yoon Yang, Andrew Carlson, Huanyu Cheng, Qingmin Yu, Numair Ahmed, Jian Wu, Seok Kim, Metin Sitti, Placid M. Ferreira, Yonggang Huang and John A. Rogers

      Article first published online: 19 MAR 2012 | DOI: 10.1002/adma.201104975

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      In this paper we present mechanics and materials aspects of elastomeric stamps that have angled features of relief on their surfaces, designed to enable control of adhesion strength by peeling direction, in a way that can be exploited in schemes for deterministic assembly by transfer printing. Detailed mechanics models capture the essential physics of interface adhesion in this system. Experiments with cylindrical stamps that have this design demonstrate their potential for use in a continuous, roller mode of operation.

    4. Synthesis and Characterization of Amphiphilic Reduced Graphene Oxide with Epoxidized Methyl Oleate (pages 2123–2129)

      B. Kollbe Ahn, Jonggeun Sung, Yonghui Li, Namhoon Kim, Myles Ikenberry, Keith Hohn, Nihar Mohanty, Phong Nguyen, T. S. Sreeprasad, Stefan Kraft, Vikas Berry and Xiuzhi Susan Sun

      Article first published online: 19 MAR 2012 | DOI: 10.1002/adma.201104080

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      Amphiphilic reduced graphene oxide is obtained by oleo-functionalization with epoxidized methyl oleate (renewable feedstock) using a green process. The excellent diverse solvent-dispersivity of the oleo-reduced amphiphilic graphene and its reduction chemistry are confirmed in this study. Oleo-reduction of amphiphilic graphene is amenable to industrially viable processes to produce future graphene-based polymer composites and systems.

    5. Solution Processed Polymer Tandem Solar Cell Using Efficient Small and Wide bandgap Polymer:Fullerene Blends (pages 2130–2134)

      Veronique S. Gevaerts, Alice Furlan, Martijn M. Wienk, Mathieu Turbiez and René A. J. Janssen

      Article first published online: 21 MAR 2012 | DOI: 10.1002/adma.201104939

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      Solution processed polymer tandem solar cells that combine wide and small bandgap absorber layers reach a power conversion efficiency of 7% in a series configuration. This represents a 20% increase compared to the best single junction cells made with the individual active layers and shows that the tandem configuration reduces transmission and thermalization losses in converting sunlight.

    6. Quantification of Geminate and Non-Geminate Recombination Losses within a Solution-Processed Small-Molecule Bulk Heterojunction Solar Cell (pages 2135–2141)

      Dan Credgington, Fiona C. Jamieson, Bright Walker, Thuc-Quyen Nguyen and James R. Durrant

      Article first published online: 19 MAR 2012 | DOI: 10.1002/adma.201104738

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      Direct measurements of the field-dependent efficiency with which electron-hole pairs are dissociated (1) can be combined with direct measurement of the carrier-density dependent rate at which they subsequently recombine (2) to determine the proportion of carriers which may be usefully extracted (3) for a class of solution-processed organic small-molecule bulk-heterojunction solar cells.

    7. UV-Cured, Flexible, and Transparent Nanocomposite Coating with Remarkable Oxygen Barrier (pages 2142–2147)

      Michael W. Möller, Daniel A. Kunz, Thomas Lunkenbein, Stefan Sommer, Arno Nennemann and Josef Breu

      Article first published online: 19 MAR 2012 | DOI: 10.1002/adma.201104781

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      A polymer-layered silicate nanocomposite coating is prepared by combining a novel synthetic lithium-hectorite and an UV-curable, cationic polyurethane. Oxygen transmission measurements clearly indicate the supremacy of the lithium-hectorite as compared to a standard montmorillonite. In addition, a very high degree of optical transparency of the nanocomposite coating is achieved, rendering this material highly interesting for flexible packaging and encapsulation applications.

    8. A General Strategy to Layered Transition-Metal Hydroxide Nanocones: Tuning the Composition for High Electrochemical Performance (pages 2148–2153)

      Xiaohe Liu, Renzhi Ma, Yoshio Bando and Takayoshi Sasaki

      Article first published online: 22 MAR 2012 | DOI: 10.1002/adma.201104753

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      A general and facile strategy for the synthesis of a large family of monometallic (Co, Ni) and bimetallic (Co-Ni, Co-Cu and Co-Zn) hydroxide nanocones (NCs) intercalated with DS ions is demonstrated. The basal spacing of the NCs can be varied by adjusting the intercalated DS amount. Especially, electrochemical characterizations reveal that bimetallic Co-Ni hydroxide NCs have a higher specific capacitance than their monometallic counterpart. These results suggest the importance of rational designing layered hydroxide NCs with tuned transition-metal composition for high-performance energy storage devices.

    9. Controlling Bulk Conductivity in Topological Insulators: Key Role of Anti-Site Defects (pages 2154–2158)

      D. O. Scanlon, P. D. C. King, R. P. Singh, A. de la Torre, S. McKeown Walker, G. Balakrishnan, F. Baumberger and C. R. A. Catlow

      Article first published online: 19 MAR 2012 | DOI: 10.1002/adma.201200187

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      Intrinsic topological insulators are realized by alloying Bi2Te3 with Bi2Se3. Angle-resolved photoemission and bulk transport measurements reveal that the Fermi level is readily tuned into the bulk bandgap. First-principles calculations of the native defect landscape highlight the key role of anti-site defects for achieving this, and predict optimal growth conditions to realize maximally resistive topological insulators.

    10. High-Performance and Stable Organic Transistors and Circuits with Patterned Polypyrrole Electrodes (pages 2159–2164)

      Liqiang Li, Lin Jiang, Wenchong Wang, Chuan Du, Harald Fuchs, Wenping Hu and Lifeng Chi

      Article first published online: 19 MAR 2012 | DOI: 10.1002/adma.201104343

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      High performance p-/n-type transistors and complementary inverter circuits are demonstrated using patterned polypyrrole (PPY) as pure electrodes. Strikingly, these devices show good stability under continuous operation and long-term storage conditions. Furthermore, PPY electrodes also exhibit good applicability in solution-processed and flexible devices. All these results indicate the great potential of PPY electrodes in solution-processed, all-organic, flexible, transparent, and low-power electronics.

    11. High-Performance Non-Volatile Organic Ferroelectric Memory on Banknotes (pages 2165–2170)

      M.A. Khan, Unnat S. Bhansali and H. N. Alshareef

      Article first published online: 21 MAR 2012 | DOI: 10.1002/adma.201200626

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      High-performance non-volatile polymer ferroelectric memory are fabricated on banknotes using poly(vinylidene fluoride trifluoroethylene). The devices show excellent performance with high remnant polarization, low operating voltages, low leakage, high mobility, and long retention times.

    12. Three-Dimensional Charge Transport in Organic Semiconductor Single Crystals (pages 2171–2175)

      Tao He, Xiying Zhang, Jiong Jia, Yexin Li and Xutang Tao

      Article first published online: 17 APR 2012 | DOI: 10.1002/adma.201200525

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      Three-dimensional charge transport anisotropy in organic semiconductor single crystals — both plates and rods (above and below, respectively, in the figure) — is measured in well-performing organic field-effect transistors for the first time. The results provide an excellent model for molecular design and device preparation that leads to good performance.

    13. Carbon Nanotubes Induce Bone Calcification by Bidirectional Interaction with Osteoblasts (pages 2176–2185)

      Masayuki Shimizu, Yasuhiro Kobayashi, Toshihide Mizoguchi, Hiroaki Nakamura, Ichiro Kawahara, Nobuyo Narita, Yuki Usui, Kaoru Aoki, Kazuo Hara, Hisao Haniu, Nobuhide Ogihara, Norio Ishigaki, Koichi Nakamura, Hiroyuki Kato, Masatomo Kawakubo, Yoshiko Dohi, Seiichi Taruta, Yoong Ahm Kim, Morinobu Endo, Hidehiro Ozawa, Nobuyuki Udagawa, Naoyuki Takahashi and Naoto Saito

      Article first published online: 22 MAR 2012 | DOI: 10.1002/adma.201103832

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      Multi-walled carbon nanotubes (MWCNTs) promote calcification during hydroxyapatite (HA) formation by osteoblasts. Primary cultured osteoblasts are incubated with MWCNTs or carbon black. After culture for 3 weeks, the degree of calcification is very high in the 50 μg mL−1 MWCNT group. Transmission electron microscopy shows needle-like crystals around the MWCNTs, and diffraction patterns reveal that the peak of the crystals almost coincides with the known peak of HA.

    14. High-Performance Ambipolar Transistors and Inverters from an Ultralow Bandgap Polymer (pages 2186–2190)

      Jian Fan, Jonathan D. Yuen, Mingfeng Wang, Jason Seifter, Jung-Hwa Seo, Ali Reza Mohebbi, Dante Zakhidov, Alan Heeger and Fred Wudl

      Article first published online: 26 MAR 2012 | DOI: 10.1002/adma.201103836

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      High mobility ambipolor organic thin-film transistors based on an ultralow bandgap polymer are presented together with their morphological and optical properties. Hole and electron mobilities of this polymer are of 1.0 cm2 V−1 s−1 and 0.7 cm2 V−1 s−1, respectively. The inverter based on two identical ambipolar transistors exhibits a gain around 35.

    15. Simple Localization of Nanofiber Scaffolds via SU-8 Photoresist and Their Use for Parallel 3D Cellular Assays (pages 2191–2195)

      Lei Jiang, Min Zhang, Jiaxing Li, Weijia Wen and Jianhua Qin

      Article first published online: 19 MAR 2012 | DOI: 10.1002/adma.201103843

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      A simple, new approach to localizing electrospun nanofiber scaffolds simply by direct writing of SU-8 photoresist followed by UV polymerization is presented. This method allows 3D cell culture arrays to be produced (see figure) and it can be integrated with microfluidic devices easily to enable low-cost high-throughput cellular assays within an addressable 3D environment, which is attractive for use in drug screening, stem cell research, tissue engineering, and regenerative medicine.

    16. Block Copolymer as a Nanostructuring Agent for High-Efficiency and Annealing-Free Bulk Heterojunction Organic Solar Cells (pages 2196–2201)

      Cédric Renaud, Sébastien-Jun Mougnier, Eleni Pavlopoulou, Cyril Brochon, Guillaume Fleury, Dargie Deribew, Giuseppe Portale, Eric Cloutet, Sylvain Chambon, Laurence Vignau and Georges Hadziioannou

      Article first published online: 22 MAR 2012 | DOI: 10.1002/adma.201104461

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      The addition of a block copolymer to the polymer/fullerene blend is a novel approach to the fabrication of organic solar cells. The block copolymer (P3HT-b-P4VP) is used as nanostructuring agent in the active layer. A significant enhancement of the cell efficiency is observed, in correlation with morphology control, both before (as-cast) and after the annealing process.

    17. High Efficiency Quantum Dot Heterojunction Solar Cell Using Anatase (001) TiO2 Nanosheets (pages 2202–2206)

      Lioz Etgar, Wei Zhang, Stefanie Gabriel, Stephen G. Hickey, Md K. Nazeeruddin, Alexander Eychmüller, Bin Liu and Michael Grätzel

      Article first published online: 17 APR 2012 | DOI: 10.1002/adma.201104497

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      This is the first report of using anatase TiO2 nanosheets with exposed (001) facets in a high-efficiency PbS quantum dot/TiO2 heterojunction solar cell. The TiO2 nanosheets have higher conduction band, and surface energy compared to normal anatase (101) TiO2 nanoparticles. This PbS QD/TiO2 heterojunction solar cell produces power conversion efficiency of 4.7% which is one of the highest reported in literature.

    18. Quantum Dot Nanoarrays: Self-Assembly With Single-Particle Control and Resolution (pages 2207–2211)

      J. Abramson, M. Palma, S. J. Wind and J. Hone

      Article first published online: 19 MAR 2012 | DOI: 10.1002/adma.201104216

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      The develpoment of a highly selective immobilization strategy for the self-assembly of quantum dots (QDs) from solution on lithographically defined, biochemically functionalized metal nanopatterns is presented. Nanosale control is achieved for the formation of predominantly single-particle structures consisting of a QD coupled to a metal nanoparticle, and assembled into an ordered nanoarray.

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