Advanced Functional Materials

Cover image for Vol. 21 Issue 14

July 22, 2011

Volume 21, Issue 14

Pages 2601–2794

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Frontispiece
    7. Feature Article
    8. Full Papers
    1. Biomimetic Structures: Biomimetic Structures: Biological Implications of Dipeptide-Substituted Polyphosphazene–Polyester Blend Nanofiber Matrices for Load-Bearing Bone Regeneration (Adv. Funct. Mater. 14/2011) (page 2601)

      Meng Deng, Sangamesh G. Kumbar, Lakshmi S. Nair, Arlin L. Weikel, Harry R. Allcock and Cato T. Laurencin

      Article first published online: 18 JUL 2011 | DOI: 10.1002/adfm.201190054

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      Successful bone regeneration benefits from 3D bioresorbable scaffolds that mimic the hierarchical architecture and mechanical characteristics of the native tissue extracellular matrix. On page 2641, Cato T. Laurencin and co-workers present a new biomimetic scaffold design composed of electrospun polymeric nanofibers that combines unique material chemistry, hierarchical architecture, and mechanics suitable for load-bearing bone regeneration. This study, for the first time, demonstrates the feasibility of developing a mechanically competent nanofiber matrix via a biomimetic strategy.

  2. Inside Front Cover

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Frontispiece
    7. Feature Article
    8. Full Papers
    1. Nanoelectrodes: Enhanced DNA Sequencing Performance Through Edge-Hydrogenation of Graphene Electrodes (Adv. Funct. Mater. 14/2011) (page 2602)

      Yuhui He, Ralph H. Scheicher, Anton Grigoriev, Rajeev Ahuja, Shibing Long, ZongLiang Huo and Ming Liu

      Article first published online: 18 JUL 2011 | DOI: 10.1002/adfm.201190055

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      Nanoelectrodes fabricated from graphene could potentially achieve the crucial single-nucleobase resolution required for novel nanopore-based approaches at DNA sequencing. The aspect of hydrogenated graphene edges has been explored by Ralph H. Scheicher, Ming Liu, and co-workers, on page 2674, through molecular-dynamics simulations and electronic-transport calculations. The temporary formation of hydrogen bonds with DNA is shown to entail higher conductivity and a reduced statistical signal distribution.

  3. Back Cover

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Frontispiece
    7. Feature Article
    8. Full Papers
    1. Gold Nanocrystals: Which Forces Control Supracrystal Nucleation in Organic Media? (Adv. Funct. Mater. 14/2011)

      Nicolas Goubet, Johannes Richardi, Pierre-Antoine Albouy and Marie-Paule Pileni

      Article first published online: 18 JUL 2011 | DOI: 10.1002/adfm.201190058

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      Gold nanocrystals can crystallize in supracrystals with a low size distribution. These mesostructures show different morphologies. Experiments and supporting simulations presented by Marie-Paule Pileni and co-workers, on page 2693, show that the solvent in which the Au nanocrystals are dispersed governs the final morphology of the nanocrystal assemblies in supracrystals. Either well-defined shapes are grown in solution, or a layer-by-layer growth on a substrate, with the formation of well defined films characterized by their plastic deformation, is observed.

  4. Contents

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Frontispiece
    7. Feature Article
    8. Full Papers
    1. Contents: (Adv. Funct. Mater. 14/2011) (pages 2603–2609)

      Article first published online: 18 JUL 2011 | DOI: 10.1002/adfm.201190056

  5. Frontispiece

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Frontispiece
    7. Feature Article
    8. Full Papers
    1. Hydrogen Photogeneration: Supported Metal Oxide Nanosystems for Hydrogen Photogeneration: Quo Vadis? (Adv. Funct. Mater. 14/2011) (page 2610)

      Davide Barreca, Giorgio Carraro, Valentina Gombac, Alberto Gasparotto, Chiara Maccato, Paolo Fornasiero and Eugenio Tondello

      Article first published online: 18 JUL 2011 | DOI: 10.1002/adfm.201190057

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      Among the various strategies for the production of hydrogen are, for example, a sustainable and eco-friendly energy vector, photoactivated routes that enable to store solar energy, or an intrinsically renewable source, directly starting from water or organic oxygenates/wastes. In their Feature Article, on page 2611, Davide Barreca, Paolo Fornasiero, and co-workers aim to address the most challenging issues, current trends, and future developments in this area. Selected representative examples on H2 generation over various kinds of oxide-based nanostructured photocatalysts are presented.

  6. Feature Article

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Frontispiece
    7. Feature Article
    8. Full Papers
    1. Supported Metal Oxide Nanosystems for Hydrogen Photogeneration: Quo Vadis? (pages 2611–2623)

      Davide Barreca, Giorgio Carraro, Valentina Gombac, Alberto Gasparotto, Chiara Maccato, Paolo Fornasiero and Eugenio Tondello

      Article first published online: 21 JUN 2011 | DOI: 10.1002/adfm.201100242

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      Supported metal oxides with tailored nano-organization represent the latest frontier for the conversion of radiant energy into hydrogen, one of the most promising energy vectors. This Feature Article provides an overview of the use of such systems for photoactivated hydrogen production. It highlights the potential of controlling nano-organization and achieving unique functional performances, with a focus on hot topics and open challenges in the field.

  7. Full Papers

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Back Cover
    5. Contents
    6. Frontispiece
    7. Feature Article
    8. Full Papers
    1. Biohybrid Carbon Nanotube/Agarose Fibers for Neural Tissue Engineering (pages 2624–2632)

      Dan Y. Lewitus, John Landers, Jonathan R. Branch, Karen L. Smith, Gerardo Callegari, Joachim Kohn and Alexander V. Neimark

      Article first published online: 5 MAY 2011 | DOI: 10.1002/adfm.201002429

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      A novel approach for producing carbon nanotube fibers (CNF) composed with the polysaccharide agarose is reported. The TOC image shows representative immunohistochemical images of rat brain slices after insertion of CNT/agarose fiber-electrodes. Cell types shown are microglia (blue), astrocytes (orange), and neurons (green). A is a control electrode and B is an electrode functionalized with laminin, a neural extracellular matrix protein. Close inspection and quantification of the cell response reveals favorable tissue reaction to the laminin tethered electrode.

    2. Functionalization and Patterning of Protein-Based Materials Using Active Ultrabithorax Chimeras (pages 2633–2640)

      Zhao Huang, Taha Salim, Autumn Brawley, Jan Patterson, Kathleen S. Matthews and Sarah E. Bondos

      Article first published online: 20 APR 2011 | DOI: 10.1002/adfm.201100067

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      Protein-based materials have the potential to directly incorporate novel functions by genetically fusing proteins capable of self-assembly and the desired activity. However, most protein assembly conditions will irreversibly damage many functional proteins. The recombinant protein Ultrabithorax rapidly self-assembles under mild, aqueous conditions, enabling production and patterning of materials functionalized with myoglobin, EGFP, mCherry, or luciferase.

    3. Biomimetic Structures: Biological Implications of Dipeptide-Substituted Polyphosphazene–Polyester Blend Nanofiber Matrices for Load-Bearing Bone Regeneration (pages 2641–2651)

      Meng Deng, Sangamesh G. Kumbar, Lakshmi S. Nair, Arlin L. Weikel, Harry R. Allcock and Cato T. Laurencin

      Article first published online: 12 MAY 2011 | DOI: 10.1002/adfm.201100275

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      A new biomimetic scaffold design comprised of electrospun polymeric nanofibers combines unique material chemistry, hierarchical architecture, and mechanics suitable for load-bearing bone regeneration. Furthermore, the biomimicry-enabled scaffolds promote osteoblast migration, proliferation, phenotype progression, maturation, and mineral­ization while maintaining a uniform cell and extracellular matrix distribution. This nanofiber scaffold platform can also be adopted for regeneration of tissue interfaces such as bone–tendon.

    4. Tunable Crystallinity in Regioregular Poly(3-Hexylthiophene) Thin Films and Its Impact on Field Effect Mobility (pages 2652–2659)

      Avishek R. Aiyar, Jung-Il Hong, Rakesh Nambiar, David M. Collard and Elsa Reichmanis

      Article first published online: 17 MAY 2011 | DOI: 10.1002/adfm.201002729

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      Ordered supramolecular precursors can be formed in regioregular poly(3-hexylthiophene) (P3HT) solutions through the application of low intensity ultrasound. This results in a dramatic increase in the degree of crystallinity of the thin films obtained by spin coating, with field effect mobilities as high as 0.03 cm2 V−1s−1. The films consist of a multiphase morphology that leads to a percolation type charge transport mechanism.

    5. Two- and Three-Terminal Resistive Switches: Nanometer-Scale Memristors and Memistors (pages 2660–2665)

      Qiangfei Xia, Matthew D. Pickett, J. Joshua Yang, Xuema Li, Wei Wu, Gilberto Medeiros-Ribeiro and R. Stanley Williams

      Article first published online: 19 MAY 2011 | DOI: 10.1002/adfm.201100180

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      A single nanoscale device that can be operated as either a two-terminal lateral memristor or a three-terminal memistor inside a crossbar structure is fabricated using a technique based on nanoimprint lithography and angle evaporation.

    6. Quantifying Interfacial Electric Fields and Local Crystallinity in Polymer–Fullerene Bulk-Heterojunction Solar Cells (pages 2666–2673)

      Raluca I. Gearba, Travis Mills, Josh Morris, Ron Pindak, Charles T. Black and Xiaoyang Zhu

      Article first published online: 17 MAY 2011 | DOI: 10.1002/adfm.201100139

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      FTIR-absorption spectroscopy is used to determine the interfacial electric field in blended P3HT:PCBM thin films thermally annealed at different temperatures. The interfacial field is ≈0.2 V nm−1 for films annealed at 150 °C and almost vanishes when the blends are annealed at 170 °C. The decrease in the interfacial field is correlated with a decrease in the open-circuit voltage.

    7. Enhanced DNA Sequencing Performance Through Edge-Hydrogenation of Graphene Electrodes (pages 2674–2679)

      Yuhui He, Ralph H. Scheicher, Anton Grigoriev, Rajeev Ahuja, Shibing Long, ZongLiang Huo and Ming Liu

      Article first published online: 9 MAY 2011 | DOI: 10.1002/adfm.201002530

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      DNA sequencing with graphene nano-electrodes shows great promise because the atomically thin graphene could electrically couple to one nucleobase at a time. Through a combination of molecular dynamics simulations and electronic transport calculations, it is found that hydrogenation of the graphene edges can lead to the formation of H-bonds with DNA, resulting in higher conductivity and less statistical signal distribution.

    8. Low-Temperature Growth of SnO2 Nanorod Arrays and Tunable n–p–n Sensing Response of a ZnO/SnO2 Heterojunction for Exclusive Hydrogen Sensors (pages 2680–2686)

      Hui Huang, Hua Gong, Chee Lap Chow, Jun Guo, Timothy John White, Man Siu Tse and Ooi Kiang Tan

      Article first published online: 24 MAY 2011 | DOI: 10.1002/adfm.201002115

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      Uniform SnO2 nanorod arrays have been deposited by PECVD and highly selective H2 sensors are fabricated by ZnO surface modification of the SnO2 nanorod arrays. Concentration-dependent n–p–n transitions for the sensing response to H2 gas in the range of 10–3000 ppm are observed owing to the formation of n-ZnO/p-Zn-O-Sn/n-SnO2 heterojunction structures.

    9. Tuning of Charge Densities in Graphene by Molecule Doping (pages 2687–2692)

      Henry Medina, Yung-Chang Lin, Dirk Obergfell and Po-Wen Chiu

      Article first published online: 24 MAY 2011 | DOI: 10.1002/adfm.201100401

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      Doping graphene by molecule adsorption depends on the adsorbate orientation and different graphene geometries such as at the edges or defects. Lattice disorders induced by plasma exposure can be used as anchor groups which serve as centers of molecule adsorption and facilitate orbital overlap between graphene and adsorbates, allowing for selective and tunable doping.

    10. Which Forces Control Supracrystal Nucleation in Organic Media? (pages 2693–2704)

      Nicolas Goubet, Johannes Richardi, Pierre-Antoine Albouy and Marie-Paule Pileni

      Article first published online: 3 JUN 2011 | DOI: 10.1002/adfm.201100382

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      With a low size distribution, gold nano­crystals can crystallize in supracrystals. These mesostructures show different morphologies. Here we show the influence of the nanocrystals size and solvent on the supracrystal nucleation, which controls the supracrystalline shape. Brownian dynamics simulations supported by experiments demonstrate that supracrystal nucleation is mainly driven by solvent-mediated interactions and not solely by the van der Waals attraction between nanocrystal cores, as widely assumed in the literature. The plastic deformation of film made of these supracrystals is also discussed.

    11. Degradation Effects Related to the Hole Transport Layer in Organic Solar Cells (pages 2705–2711)

      Bernhard Ecker, Jairo Cesar Nolasco, Josep Pallarés, Lluis Francesc Marsal, Jörg Posdorfer, Jürgen Parisi and Elizabeth von Hauff

      Article first published online: 24 MAY 2011 | DOI: 10.1002/adfm.201100429

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      The density of states in organic solar cells prepared with different hole transport layers (HTLs) is derived from impedance spectroscopy measurements. It is shown that polyaniline:poly(styrene sulfonate) (PANI:PSS) HTLs result in higher stability than poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) HTL. Trap states at the interface of the HTL and the active layer were identified for the water-based HTLs.

    12. Three-Dimensional Polymer Constructs Exhibiting a Tunable Negative Poisson's Ratio (pages 2712–2720)

      David Y. Fozdar, Pranav Soman, Jin Woo Lee, Li-Hsin Han and Shaochen Chen

      Article first published online: 11 MAY 2011 | DOI: 10.1002/adfm.201002022

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      Poisson's ratio describes the degree to which a material contracts (expands) transversally when axially strained. Here, three-dimensional constructs (scaffolds) in polyethylene glycol (PEG) that exhibit tunable negative Poisson's ratios are fabricated. A negative Poisson's ratio is achieved by patterning individual layers of PEG with specially arranged unit-cellular (pore) structures that tune the Poisson's ratio by their geometry and deformation mechanisms.

    13. Cross-Stacked Superaligned Carbon Nanotube Films for Transparent and Stretchable Conductors (pages 2721–2728)

      Kai Liu, Yinghui Sun, Peng Liu, Xiaoyang Lin, Shoushan Fan and Kaili Jiang

      Article first published online: 19 MAY 2011 | DOI: 10.1002/adfm.201100306

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      The utilization of cross-stacked superaligned carbon nanotube (SACNT) films for transparent and stretchable conductors is reported. The cross-stacked SACNT films are isotropic in electrical conductivity, but anisotropic in mechanical properties. Along some oblique directions, the films possess high tensile strains of more than 35%. Embedding these films into polydimethylsiloxane (PDMS) produces transparent conductors that are highly stretchable and exhibit reversible electrical characteristics.

    14. Induced Chain Alignment of Conjugated Polymers Within Nanoporous Template (pages 2729–2736)

      Kuan-Hsin Lo, Rong-Ming Ho, Yung-Ming Liao, Chain-Shu Hsu, Florian Massuyeau, Yuan-Chun Zhao, Serge Lefrant and Jean-Luc Duvail

      Article first published online: 30 MAY 2011 | DOI: 10.1002/adfm.201002573

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      This work presents a simple method to generate ordered conjugated polymer nanoarrays through a pore-filling process for nanoporous polystyrene polymer templates to enhance the efficiency of photo­luminescence (PL). The enhanced PL reaches the maximum intensity for completely pore-filled conjugated polymer nanoarrays due to the nanoscale spatial effect which induces chain alignment, alleviating the self-quenching problem.

    15. Amorphous and Crystalline GeTe Nanocrystals (pages 2737–2743)

      Indika U. Arachchige, Ronald Soriano, Christos D. Malliakas, Sergei A. Ivanov and Mercouri G. Kanatzidis

      Article first published online: 24 MAY 2011 | DOI: 10.1002/adfm.201100633

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      A facile method for the synthesis of crystalline and amorphous GeTe nanoparticles (NPs) is reported. As formed crystalline NPs show rhombohedral symmetry and narrow dispersity at smaller size regimes while amorphous NPs display nearly spherical morphology and amorphous-to-crystalline phase transition at 209–237 °C. Detailed investigation of the local structure of the amorphous GeTe reveals that its local structure is equivalent to the pressure- and temperature-stabilized orthorhombic GeTe.

    16. Non-Geminate Recombination as the Primary Determinant of Open-Circuit Voltage in Polythiophene:Fullerene Blend Solar Cells: an Analysis of the Influence of Device Processing Conditions (pages 2744–2753)

      Dan Credgington, Rick Hamilton, Pedro Atienzar, Jenny Nelson and James R. Durrant

      Article first published online: 1 JUN 2011 | DOI: 10.1002/adfm.201100225

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      The role of non-geminate recombination in determining the open-circuit voltage of P3HT/PCBM solar cells fabricated using different fabrication procedures is analyzed. Variations in open-circuit voltage between 0.4 and 0.65 V are shown to arise from variations in the rate coefficient for non-geminate recombination, as well as variations in charge carrier density in the photoactive layer of the devices. Quantification of these variations enables us to calculate the open-circuit voltage of each device to within ±5 mV.

    17. Water-Soluble Poly(N-isopropylacrylamide)–Graphene Sheets Synthesized via Click Chemistry for Drug Delivery (pages 2754–2763)

      Yongzheng Pan, Hongqian Bao, Nanda Gopal Sahoo, Tongfei Wu and Lin Li

      Article first published online: 19 MAY 2011 | DOI: 10.1002/adfm.201100078

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      Covalently functionalized graphene sheets are prepared by grafting a well-defined thermo-responsive poly(N- isopropylacrylamide) (PNIPAM) via click chemistry. The PNIPAM-grafted graphene sheets (PNIPAM-GS) exhibit a superior loading capacity of loading a water-insoluble anticancer drug, camptothecin (CPT). More importantly, PNIPAM-GSs are proven to be practically non-toxic and the PNIPAM-GS-CPT complex affords a strong potency of in vitro cancer cell killing.

    18. Tailoring of LaxSr1-xCoyFe1-yO3-δ Nanostructure by Pulsed Laser Deposition (pages 2764–2775)

      Pawel Plonczak, Anja Bieberle-Hütter, Martin Søgaard, Thomas Ryll, Julia Martynczuk, Peter Vang Hendriksen and Ludwig J. Gauckler

      Article first published online: 26 MAY 2011 | DOI: 10.1002/adfm.201100251

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      A detailed study of the nano- and microstructure of La0.58Sr0.4Co0.2Fe0.8O3-δ thin films prepared using pulsed laser deposition is presented, as a function of deposition conditions. The resulting structure–deposition map allows for a tailoring of the thin film structure, ranging from highly porous to dense and crystalline to amorphous films. Highly porous crystalline films can be deposited even though the film thickness is small.

    19. Labeling and Tracking P2 Purinergic Receptors in Living Cells Using ATP-Conjugated Quantum Dots (pages 2776–2780)

      Shan Jiang, Aiping Liu, Hongwei Duan, Jianchow Soo and Peng Chen

      Article first published online: 24 MAY 2011 | DOI: 10.1002/adfm.201100472

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      Specifically and readily labeled by ATP-conjugated quantum dots (QDs), the endocytosis, vesicular trafficking and recycling of P2 purinergic receptors was studied in live cells, demonstrating their involvement in neuronal differentiation and apoptosis.

    20. N-Doped Polypyrrole-Based Porous Carbons for CO2 Capture (pages 2781–2787)

      Marta Sevilla, Patricia Valle-Vigón and Antonio B. Fuertes

      Article first published online: 24 MAY 2011 | DOI: 10.1002/adfm.201100291

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      N-doped porous carbons exhibiting high surface areas, large pore volumes and a porosity in the micro-/mesopore range are prepared by using a one-step synthesis strategy based on the chemical activation of polypyrrole. The prepared activated carbons exhibit a large CO2 uptake (up to 3.9 mmol CO2 g−1 at 25 °C), a good selectivity for CO2-N2 separation, and they can be easily regenerated.

    21. Luminescent Sensing and Catalytic Performances of a Multifunctional Lanthanide-Organic Framework Comprising a Triphenylamine Moiety (pages 2788–2794)

      Pengyan Wu, Jian Wang, Yaming Li, Cheng He, Zhong Xie and Chunying Duan

      Article first published online: 31 MAY 2011 | DOI: 10.1002/adfm.201100115

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      A multifunctional lanthanide-organic framework material comprising a triphenylamine moiety is synthesized to function as a luminescent chemosensor towards salicylaldehyde. A high concentration of Lewis acid Tb3+ sites and Lewis base triphenylamine sites on its internal surfaces enable it to prompt both Knoevenagel and cyanosilylation reactions in a size-selective fashion. The ratiometric fluorescent response towards aldehydes (I540/I435) demonstrates the possibility of directly validating the absorption sites and the catalytic mechanism of the multi­functional Ln metal–organic framework material.

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