Advanced Functional Materials

Cover image for Vol. 19 Issue 19

October 9, 2009

Volume 19, Issue 19

Pages 3021–3178

  1. Cover Picture

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    1. Nanofibers from Laser Spinning: Laser Spinning of Bioactive Glass Nanofibers (Adv. Funct. Mater. 19/2009)

      Félix Quintero, Juan Pou, Rafael Comesaña, Fernando Lusquiños, Antonio Riveiro, Adrian B. Mann, Robert G. Hill, Zoe Y. Wu and Julian R. Jones

      Article first published online: 5 OCT 2009 | DOI: 10.1002/adfm.200990085

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      This cover image is a graphical representation of the laser spinning process described by Félix Quintero et al. on page 3084. Laser spinning involves the use of a high power laser to melt a very small volume from a plate of the precursor material. A high speed supersonic gas jet causes the rapid elongation and cooling of the melt, yielding a glass nanofiber. The authors also describe the use of this technique in producing Bioglass nanofibers.

  2. Inside Front Cover

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    1. Flexible Organic Solar Cells: Nanoscale Phase Separation and High Photovoltaic Efficiency in Solution-Processed, Small-Molecule Bulk Heterojunction Solar Cells (Adv. Funct. Mater. 19/2009)

      Bright Walker, Arnold B. Tamayo, Xuan-Dung Dang, Peter Zalar, Jung Hwa Seo, Andres Garcia, Mananya Tantiwiwat and Thuc-Quyen Nguyen

      Article first published online: 5 OCT 2009 | DOI: 10.1002/adfm.200990086

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      The inside cover of this issue illustrates the fabrication of lightweight and flexible organic solar cells, developed by B. Walker et al. on page 3063, from a solution of fullerene and diketopyrrolopyrrole-based materials. The texture of the organic film on the substrate was taken from an atomic force microscope phase image of the high performance device (4.4% power conversion efficiency), showing the phase separation behavior of the two molecular semiconducting materials.

  3. Contents

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    1. Contents: (Adv. Funct. Mater. 19/2009) (pages 3021–3027)

      Article first published online: 5 OCT 2009 | DOI: 10.1002/adfm.200990087

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    1. Morphology Control in Solution-Processed Bulk-Heterojunction Solar Cell Mixtures (pages 3028–3036)

      Adam J. Moulé and Klaus Meerholz

      Article first published online: 26 AUG 2009 | DOI: 10.1002/adfm.200900775

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      The efficiency of bulk-heterojunction solar cells is very sensitive to the nanoscale structure of the active layer. This article presents a review of several new techniques that have been developed to control morphology in polymer/fullerene heterojunction mixtures. The figure shows an example of how porous nanostructures can be formed from conjugated polymers using non-solvent additives.

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    1. Hydrogel Patterning: (Swelling-Induced Surface Patterns in Hydrogels with Gradient Crosslinking Density) Adv. Funct. Mater. 19/2009

      Murat Guvendiren, Shu Yang and Jason A. Burdick

      Article first published online: 5 OCT 2009 | DOI: 10.1002/adfm.200990088

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      In this paper by M. Guvendiren et al, a simple and robust method is used to generate a range of osmotically-driven surface patterns in hydrogels, including random, lamellar, peanut, and hexagonal structures. The patterns are fabricated by exposing a photocurable formulation to light while open to air and then swelling, using oxygen inhibition of the radical polymerization at the surface to create a gradient of crosslinking with depth.

  6. Full Papers

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    1. Swelling-Induced Surface Patterns in Hydrogels with Gradient Crosslinking Density (pages 3038–3045)

      Murat Guvendiren, Shu Yang and Jason A. Burdick

      Article first published online: 19 AUG 2009 | DOI: 10.1002/adfm.200900622

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      The dynamic evolution of a wide range of surface patterns, including a highly ordered hexagonal pattern in transit to peanut shape, lamellar, and random worm-like structures, is reported in poly (hydroxyethyl methacrylate) hydrogel films with a modulus gradient through film depth. The order of the patterns is determined by the crosslinker concentration and the characteristic wavelength is proportional to the initial gel thickness.

    2. Affinity-Based Protein Surface Pattern Formation by Ligand Self-Selection from Mixed Protein Solutions (pages 3046–3055)

      Manish Dubey, Kazunori Emoto, Hironobu Takahashi, David G. Castner and David W. Grainger

      Article first published online: 10 AUG 2009 | DOI: 10.1002/adfm.200900809

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      Photolithographically prepared surface patterns of two affinity ligands (biotin and chloroalkane) specific for two proteins (streptavidin and HaloTag, respectively) are used to spontaneously form high-fidelity surface patterns of the two proteins from their mixed solution. High affinity protein-surface self-selection onto patterned ligands on surfaces exhibiting low non-specific adsorption rapidly yields the patterned protein surfaces.

    3. Biodegradable Polymer Crosslinker: Independent Control of Stiffness, Toughness, and Hydrogel Degradation Rate (pages 3056–3062)

      Chaenyung Cha, Richie H. Kohman and Hyunjoon Kong

      Article first published online: 19 AUG 2009 | DOI: 10.1002/adfm.200900865

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      Oxidized methacrylic alginate (OMA), which presents multiple methacrylates and biodegradable units, can crosslink a variety of polymers to form hydrogels which show significant increase in mechanical strength, and tune degradation rates. OMA-crosslinked hydrogels can control the release of vascular endothelial growth factor, leading to enhanced angiogenesis in vivo.

    4. Nanoscale Phase Separation and High Photovoltaic Efficiency in Solution-Processed, Small-Molecule Bulk Heterojunction Solar Cells (pages 3063–3069)

      Bright Walker, Arnold B. Tamayo, Xuan-Dung Dang, Peter Zalar, Jung Hwa Seo, Andres Garcia, Mananya Tantiwiwat and Thuc-Quyen Nguyen

      Article first published online: 28 JUL 2009 | DOI: 10.1002/adfm.200900832

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      Solution-processed, organic solar cells constitute a lightweight, flexible, and cheaply manufactured source of electricity, typically comprising a polymeric donor and a fullerene acceptor. The polymeric nature of the donor tends to complicate its synthesis, purification and reproducibility. Here, a non-polymeric donor material which yields desirable morphologies and high efficiencies (4.4 ± 0.4%) when solution-processed with a fullerene acceptor is reported.

    5. Au@pNIPAM Thermosensitive Nanostructures: Control over Shell Cross-linking, Overall Dimensions, and Core Growth (pages 3070–3076)

      Rafael Contreras-Cáceres, Jessica Pacifico, Isabel Pastoriza-Santos, Jorge Pérez-Juste, Antonio Fernández-Barbero and Luis M. Liz-Marzán

      Article first published online: 19 AUG 2009 | DOI: 10.1002/adfm.200900481

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      Thermoresponsive nanocomposites comprising a gold nanoparticle core and a poly(N-isopropylacrylamide) (pNIPAM) shell are successfully synthesized (see figure) by a two-step protocol. Through careful control of the experimental conditions, the pNIPAM shell cross-linking density can be varied, and in turn its porosity and stiffness, as well as shell thickness from a few to few hundred nanometers can be tuned. Additionally, the porous pNIPAM shells can be used to modulate the catalytic activity.

    6. Atomic-Layer Graphene as a Saturable Absorber for Ultrafast Pulsed Lasers (pages 3077–3083)

      Qiaoliang Bao, Han Zhang, Yu Wang, Zhenhua Ni, Yongli Yan, Ze Xiang Shen, Kian Ping Loh and Ding Yuan Tang

      Article first published online: 25 AUG 2009 | DOI: 10.1002/adfm.200901007

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      The use of atomic-layer graphene as a saturable absorber in a mode-locked fiber laser for the generation of ultrashort soliton pulses at telecommunication band is demonstrated. These results suggest that ultrathin graphene films are potentially useful as optical elements in fiber lasers.

    7. Laser Spinning of Bioactive Glass Nanofibers (pages 3084–3090)

      Félix Quintero, Juan Pou, Rafael Comesaña, Fernando Lusquiños, Antonio Riveiro, Adrian B. Mann, Robert G. Hill, Zoe Y. Wu and Julian R. Jones

      Article first published online: 19 AUG 2009 | DOI: 10.1002/adfm.200801922

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      The production of nanofibers of bioactive glass by laser spinning is reported. The technique involves melting and elongation of a precursor material with tailored composition using a high power laser and a supersonic gas jet. The morphology, composition and structure of the nanofibers are analyzed and their bioactivity is assessed by immersion in SBF.

    8. Synthesis of Hexagonal Yb3+,Er3+-Doped NaYF4 Nanocrystals at Low Temperature (pages 3091–3097)

      Helmut Schäfer, Pavel Ptacek, Henning Eickmeier and Markus Haase

      Article first published online: 31 AUG 2009 | DOI: 10.1002/adfm.200900642

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      Upon excitation in the NIR, transparent toluene solutions of hexagonal NaYF4 nanocrystals doped with Yb3+ and Er3+ exhibit an intense emission of green light. The crystals are produced by a new synthetic method based on the decomposition of metal carbonates and ammonium fluoride at low temperatures.

    9. Wet and Dry Adhesion Properties of Self-Selective Nanowire Connectors (pages 3098–3102)

      Hyunhyub Ko, Zhenxing Zhang, Yu-Lun Chueh, Johnny C. Ho, Jongho Lee, Ronald S. Fearing and Ali Javey

      Article first published online: 25 AUG 2009 | DOI: 10.1002/adfm.200901178

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      Hybrid inorganic/organic core/shell nanowire forests show highly versatile and reusable connectors capabilities with strong adhesion strengths in both dry and wet environments, arising from the van der Waals interactions between the nanofibrillar structures. In addition, the superhydrophobic surface characteristic of the nanowire connectors enables the wet self-cleaning of contaminant particles from the surface.

    10. Photophysics and Photocurrent Generation in Polythiophene/Polyfluorene Copolymer Blends (pages 3103–3111)

      Christopher R. McNeill, Agnese Abrusci, Inchan Hwang, Matthias A. Ruderer, Peter Müller-Buschbaum and Neil C. Greenham

      Article first published online: 20 AUG 2009 | DOI: 10.1002/adfm.200900801

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      The interplay between polymer order, phase separation (see figure), and photovoltaic efficiency in blends of poly(3-hexylthiophene) (P3HT) with polyfluorene copolymers is investigated. The choice of polyfluorene copolymer is shown to influence the temperature at which P3HT orders in the blend and hence the device efficiency achievable. In addition to ordered P3HT phases, a degree of phase separation is also required to facilitate charge separation.

    11. Lipid-Like Nanoparticles for Small Interfering RNA Delivery to Endothelial Cells (pages 3112–3118)

      Seung-Woo Cho, Michael Goldberg, Sun Mi Son, Qiaobing Xu, Fan Yang, Ying Mei, Said Bogatyrev, Robert Langer and Daniel G. Anderson

      Article first published online: 25 AUG 2009 | DOI: 10.1002/adfm.200900519

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      Nanoparticles composed of lipid-like materials (lipidoids) are developed and screened to facilitate non-viral delivery of small interfering RNA (siRNA) to endothelial cells (ECs). Nanoparticles composed of siRNA and lipidoids with small size and positive charge are formed by self assembly of lipidoids and siRNA. Particles composed of leading lipidoids show significantly better delivery to ECs than a leading commercially-available transfection reagent. As a model of potential therapeutic application, nanoparticles composed of the top-performing lipidoid significantly silence anti-angiogenic factor expression, enhance EC proliferation, and decrease EC apoptosis under a simulated ischemic condition.

  7. Frontispiece

    1. Top of page
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    3. Inside Front Cover
    4. Contents
    5. Feature Article
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    1. Immunosensors: (Ionic-Liquid-Doped Polyaniline Inverse Opals: Preparation, Characterization, and Application for the Electrochemical Impedance Immunoassay of Hepatitis B Surface Antigen) Adv. Funct. Mater. 19/2009

      Xing-Hua Li, Lin Dai, Yan Liu, Xiao-Jun Chen, Wei Yan, Li-Ping Jiang and Jun-Jie Zhu

      Article first published online: 5 OCT 2009 | DOI: 10.1002/adfm.200990089

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      Xing-Hua Li et al. describe the preparation of ionic liquid-doped polyaniline (IL-PANI) inverse opaline film with surface assemblies of gold nanoparticles. The resulting AuNP/IL-PANI film is conjugated with Hepatitis B surface antibody molecules to fabricate a immunosensor with a low detection limit for Hepatitis B surface antigen.

  8. Full Papers

    1. Top of page
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    1. Ionic-Liquid-Doped Polyaniline Inverse Opals: Preparation, Characterization, and Application for the Electrochemical Impedance Immunoassay of Hepatitis B Surface Antigen (pages 3120–3128)

      Xing-Hua Li, Lin Dai, Yan Liu, Xiao-Jun Chen, Wei Yan, Li-Ping Jiang and Jun-Jie Zhu

      Article first published online: 26 AUG 2009 | DOI: 10.1002/adfm.200901003

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      An ionic-liquid-doped polyaniline (IL-PANI) inverse opal film is prepared and gold nanoparticles (AuNPs) are successfully assembled on the surface of the film. The resulting AuNP/IL-PANI film is conjugated with Hepatitis B surface antibody (HBsAb) molecules to fabricate a immunosensor, which could detect the concentration of Hepatitis B surface antigen (HBsAg) with a low detection limit.

    2. Fabrication of a Macroporous Microwell Array for Surface-Enhanced Raman Scattering (pages 3129–3135)

      Martina Zamuner, David Talaga, Frédérique Deiss, Valérie Guieu, Alexander Kuhn, Paolo Ugo and Neso Sojic

      Article first published online: 19 AUG 2009 | DOI: 10.1002/adfm.200900752

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      A colloidal templating procedure for generating high-density arrays of gold macroporous microwells, which act as discrete sites for surface-enhanced Raman scattering (SERS), is reported. Since the fabrication steps keep the initial architecture of the optical fiber bundle, such ordered SERS-active platforms fabricated onto an imaging waveguide open new applications in remote SERS imaging (see figure), new plasmonic devices, and integrated electro-optical sensor arrays.

    3. Hard Macrocellular Silica Si(HIPE) Foams Templating Micro/Macroporous Carbonaceous Monoliths: Applications as Lithium Ion Battery Negative Electrodes and Electrochemical Capacitors (pages 3136–3145)

      Nicolas Brun, Savari R. S. Prabaharan, Mathieu Morcrette, Clément Sanchez, Gilles Pécastaings, Alain Derré, Alain Soum, Hervé Deleuze, Marc Birot and Rénal Backov

      Article first published online: 25 AUG 2009 | DOI: 10.1002/adfm.200900749

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      Macrocellular silica Si(HIPE) foams are used as hard templates for the generation of micro-/macroporous carbonaceous monoliths. The final materials are fully characterized, and their functionalities as lithium ion battery negative electrodes and electrochemical capacitors are examined.

    4. Synthesis and Characterization of Ferroferriborate (Fe3BO5) Nanorods (pages 3146–3150)

      Yi Liu, Sheng Peng, Yong Ding, Chuanbing Rong, Jaemin Kim, J. Ping Liu, Zhong Lin Wang and Shouheng Sun

      Article first published online: 24 AUG 2009 | DOI: 10.1002/adfm.200900900

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      Fe3BO5 nanorods are synthesized by a facile thermal decomposition of iron acetylacetonate and t-butylamine borane (TBAB). The aspect ratios of these nanorods are tuned by the amount of TBAB added to the reaction mixture. These Fe3BO5 nanorods are antiferromagnetic with TN = 174 K, which is higher than that of bulk Fe3BO5 (114 K), due to their nanometer sizes.

    5. Optimized La0.6Sr0.4CoO3–δ Thin-Film Electrodes with Extremely Fast Oxygen-Reduction Kinetics (pages 3151–3156)

      Judith Januschewsky, Martin Ahrens, Alexander Opitz, Frank Kubel and Jürgen Fleig

      Article first published online: 25 AUG 2009 | DOI: 10.1002/adfm.200900362

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      Mixed conducting La0.6Sr0.4CoO3–δ thin-film electrodes are prepared by pulsed laser deposition on yttria-stabilized zirconia. The polarization resistance of electrochemical oxygen exchange is particularly low for films of very low crystallinity and values of approximately 0.1 Ω cm2 can be achieved at 600 °C for 200 nm thin films (see figure).

    6. Study of Energy Transfer and Triplet Exciton Diffusion in Hole-Transporting Host Materials (pages 3157–3164)

      Chao Wu, Peter I. Djurovich and Mark E. Thompson

      Article first published online: 26 AUG 2009 | DOI: 10.1002/adfm.200900357

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      To study triplet exciton diffusion in OLEDs, a mismatch of HOMO levels between the host and dopant is deliberately created in a new device architecture. The advantage of this design is the exclusion of the direct recombination on dopant molecules. The study provides a means to evaluate differences in the triplet exciton diffusion length of various host matrices.

    7. Template Deformation-Tailored ZnO Nanorod/Nanowire Arrays: Full Growth Control and Optimization of Field-Emission (pages 3165–3172)

      Haibo Zeng, Xijin Xu, Yoshio Bando, Ujjal K. Gautam, Tianyou Zhai, Xiaosheng Fang, Baodan Liu and Dmitri Golberg

      Article first published online: 20 AUG 2009 | DOI: 10.1002/adfm.200900714

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      Deformation-tailored colloidal crystal templates and electrodeposition are combined to facilely growth and fully control ZnO nanorod/nanowire arrays at the centimeter scale; control is exerted over their density, uniformity, and tapering. A low turn-on electric field of 1.8 V µm−1, a high field-enhancement factor of 5 750, and an emitting current density of up to 2.5 mA cm−2 are obtained.

    8. Tunable Injection Barrier in Organic Resistive Switches Based on Phase-Separated Ferroelectric–Semiconductor Blends (pages 3173–3178)

      Kamal Asadi, Tom G. de Boer, Paul W. M. Blom and Dago M. de Leeuw

      Article first published online: 26 AUG 2009 | DOI: 10.1002/adfm.200900383

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      Organic, nonn-volatile resistive bistable diodes based on phase-separated blends of ferroelectric and semiconducting polymers are fabricated. The polarization field of the ferroelectric modulates the injection barrier at the semiconductor–electrode contact and, hence, the resistance of comprising diodes. Injection barrier of up to 1.6 eV can be surmounted yielding on/off current modulations of more than five orders of magnitude.

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