Advanced Materials

Cover image for Vol. 17 Issue 21

November, 2005

Volume 17, Issue 21

Pages 2521–2644

    1. Cover Picture: Combinatorial Material Mechanics: High-Throughput Polymer Synthesis and Nanomechanical Screening (Adv. Mater. 21/2005)

      C. A. Tweedie, D. G. Anderson, R. Langer and K. J. Van Vliet

      Article first published online: 25 OCT 2005 | DOI: 10.1002/adma.200590109

      Combinatorial materials science requires parallel advances in materials characterization. A high-throughput nanoscale synthesis/nanomechanical profiling approach capable of accurately screening the mechanical properties of 1,700 photopolymerizable materials (see Figure, scale bar: 100 μm) within a large, discrete polymer library is presented. This approach enables rapid correlation of polymer composition, processing, and structure with mechanical performance metrics.

    2. Inside Front Cover: One-Dimensional Plasmon Coupling by Facile Self-Assembly of Gold Nanoparticles into Branched Chain Networks (Adv. Mater. 21/2005)

      S. Lin, M. Li, E. Dujardin, C. Girard and S. Mann

      Article first published online: 25 OCT 2005 | DOI: 10.1002/adma.200590110

      Short chains and complex networks of interconnected Au nanoparticle chains (see Figure) are produced by a simple template-free approach. Optical spectroscopy and computer simulations show that surface plasmons from individual non-contacting nanoparticles are strongly coupled in the resulting 1D superstructures. These chains may provide a unique way to fabricate complex subwavelength optical waveguides.

    3. Contents: Adv. Mater. 21/2005 (pages 2521–2529)

      Article first published online: 25 OCT 2005 | DOI: 10.1002/adma.200590106

    4. Silicon Nanocrystals: Photosensitizers for Oxygen Molecules (pages 2531–2544)

      D. Kovalev and M. Fujii

      Article first published online: 29 SEP 2005 | DOI: 10.1002/adma.200500328

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      The features of nanoscale silicon that make it different from the bulk result in very efficient energy transfer from excitons confined in silicon nanocrystals to oxygen molecules following their activation to the highly reactive singlet state (see Figure). The mechanism for the photosensitization of oxygen molecules using silicon nanocrystals is reviewed. We discuss, in addition, the implications of these findings for physics, chemistry, biology, and medicine.

    5. Focused-Ion-Beam Nanofabrication of Near-Infrared Magnetic Metamaterials (pages 2547–2549)

      C. Enkrich, F. Pérez-Willard, D. Gerthsen, J. F. Zhou, T. Koschny, C. M. Soukoulis, M. Wegener and S. Linden

      Article first published online: 13 SEP 2005 | DOI: 10.1002/adma.200500804

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      Split-ring resonators with a magnetic resonance in the near-infrared have been fabricated using the rapid- prototyping capabilities of focused- ion-beam writing. By varying the design parameters, a continuous transition from a degenerate Mie resonance to a magnetic-dipole response is shown (see Figure). In particular, a negative magnetic permeability at a wavelength of 2.4 μm and a negative magnetic susceptibility at a wavelength of 1.7 μm are demonstrated.

    6. Characterization of Phase Purity in Organic Semiconductors by Lattice-Phonon Confocal Raman Mapping: Application to Pentacene (pages 2549–2553)

      A. Brillante, I. Bilotti, R. G. Della Valle, E. Venuti, M. Masino and A. Girlando

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200501350

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      Lattice-phonon confocal Raman mapping is a powerful technique to probe the crystal structure of polymorphs of organic semiconductors. This technique is fast, reliable, and capable of monitoring physical modifications and phase inhomogeneities in crystal domains at the micrometer scale. Applying the technique to pentacene crystals (see Figure) shows that phase inhomogeneities are not confined to the crystal surface, but penetrate into the crystal.

    7. One-Dimensional Plasmon Coupling by Facile Self-Assembly of Gold Nanoparticles into Branched Chain Networks (pages 2553–2559)

      S. Lin, M. Li, E. Dujardin, C. Girard and S. Mann

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200500828

      Thumbnail image of graphical abstract

      Short chains and complex networks of interconnected Au nanoparticle chains (see Figure) are produced by a simple template-free approach. Optical spectroscopy and computer simulations show that surface plasmons from individual non-contacting nanoparticles are strongly coupled in the resulting 1D superstructures. These chains may provide a unique way to fabricate complex subwavelength optical waveguides.

    8. Multiscale Nanopatterns Templated from Two-Dimensional Assemblies of Photoresist Particles (pages 2559–2562)

      J. H. Moon, S. G. Jang, J.-M. Lim and S.-M. Yang

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200501167

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      Multiscale nanopatterns fabricated by colloidal lithography, using two-dimensional self-assemblies of photoresist particles as masks, are presented. The colloidal masks with features of multiple length scales are obtained by photolithography and used for constructing submicrometer-hole arrays over large areas (see Figure). By depositing functional materials through these masks, nanopatterned substrates useful in a wide range of applications can be produced.

    9. One-Pot Synthesis of Octahedral Cu2O Nanocages via a Catalytic Solution Route (pages 2562–2567)

      C. Lu, L. Qi, J. Yang, X. Wang, D. Zhang, J. Xie and J. Ma

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200501128

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      Unique single-crystalline octahedral Cu2O nanocages (see Figure) are synthesized in solution by the catalytic reduction of copper tartrate complex into octahedral Cu2O nanocrystals and a subsequent spontaneous hollowing process. A wealth of colorful nanostructures with widely tunable bandgaps in the range 2.6–2.2 eV are obtained. The obtained nanocages may find potential use in solar-energy conversion, catalysis, and as model systems for fundamental research.

    10. Photoembossing of Periodic Relief Structures Using Polymerization- Induced Diffusion: A Combinatorial Study (pages 2567–2571)

      C. Sánchez, B.-J. de Gans, D. Kozodaev, A. Alexeev, M. J. Escuti, C. van Heesch, T. Bel, U. S. Schubert, C. W. M. Bastiaansen and D. J. Broer

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200500777

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      Photoembossing is a solvent-free photolithographic technique for the production of polymeric relief microstructures (see Figure). A combinatorial methodology to explore the influence of different parameters (e.g., processing temperature, binder content, photoinitiator content) on the resultant relief structure is presented using an acrylate-based model system. Results are discussed in the framework of a diffusion-polymerization model.

    11. Bioassisted Room-Temperature Immobilization and Mineralization of Zinc Oxide—The Structural Ordering of ZnO Nanoparticles into a Flower-Type Morphology (pages 2571–2575)

      M. Umetsu, M. Mizuta, K. Tsumoto, S. Ohara, S. Takami, H. Watanabe, I. Kumagai and T. Adschiri

      Article first published online: 22 SEP 2005 | DOI: 10.1002/adma.200500863

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      A peptide with an affinity for ZnO, selected by a phage-display system, preferentially immobilizes ZnO particles on a gold-coated polypropylene plate and assists in the homogeneous assembly of 10 nm diameter ZnO nanoparticles into unique flower-like morphologies (see Figure). The peptide is selective in binding ZnO, but not ZnS or Eu2O3. This combinatorial library approach may yield new peptides used to create new structures via biomineralization.

    12. Multicomponent Patterning of Layer-by-Layer Assembled Polyelectrolyte/Nanoparticle Composite Thin Films with Controlled Alignment (pages 2575–2579)

      J. Park, L. D. Fouché and P. T. Hammond

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200501075

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      Composite thin films of polyelectrolytes and fluorescent nanoparticles can be directly transfer-printed onto various substrates including indium tin oxide coated poly(ethylene terephthalate). The sequential transfer printing of thin films with controlled alignment introduces multicomponent patterns onto substrates, demonstrating possible practical device fabrication using functional polyelectrolyte multilayer composite thin films (see Figure).

    13. High Electron Mobility in Room-Temperature Discotic Liquid-Crystalline Perylene Diimides (pages 2580–2583)

      Z. An, J. Yu, S. C. Jones, S. Barlow, S. Yoo, B. Domercq, P. Prins, L. D. A. Siebbeles, B. Kippelen and S. R. Marder

      Article first published online: 13 SEP 2005 | DOI: 10.1002/adma.200500027

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      Perylene diimide discotic columnar liquid-crystalline mesophases (see Figure) can show very high electron mobilities under ambient conditions. While the mobilities are strongly dependent on sample morphology and processing conditions, mobilities as high as 1.3 cm2 V–1 s–1 are measured, greater than that of amorphous silicon.

    14. Freestanding Nanosheets from Crosslinked Biphenyl Self-Assembled Monolayers (pages 2583–2587)

      W. Eck, A. Küller, M. Grunze, B. Völkel and A. Gölzhäuser

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200500900

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      Freestanding nanosheets (see Figure) with the thickness of a single molecule and lateral dimensions in the micrometer range have been obtained by the release of self-assembled monolayers from the underlying surface by dissolution of the substrate or by scission of the anchor group–substrate bonds. The self-assembled monolayers are composed of biphenyl units that are crosslinked by electron irradiation.

    15. Ordered Two- and Three-Dimensional Arrays Self-Assembled from Water-Soluble Nanocrystal–Micelles (pages 2587–2590)

      H. Fan, E. Leve, J. Gabaldon, A. Wright, R. E. Haddad and C. J. Brinker

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200501088

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      Two- and three-dimensional, ordered nanocrystal arrays are formed from the self-assembly of water-soluble nanocrystal–micelles that are prepared using surfactant encapsulation techniques. This new method is simple, widely applicable, and can be used to prepare water-soluble nanocrystals with different compositions and shapes, such as sphere, rod, and cube, as well as their ordered arrays (see Figure). Applications in fabrication of SERS-based sensor platforms are envisaged.

    16. Crosslinked Poly(styrene)-block-Poly(2-vinylpyridine) Thin Films as Swellable Templates for Mesostructured Silica and Titania (pages 2591–2595)

      R. C. Hayward, B. F. Chmelka and E. J. Kramer

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200500334

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      Mesostructured inorganic films are formed from pre-organized block-copolymer thin films. The diblock copolymer used, poly(d8-styrene)-block-poly(2-vinylpyridine), was first crosslinked, thus retaining its morphology. Silica and titania were incorporated into the structure and the polymer was subsequently removed, generating mesoporous inorganic films whose morphologies were directly related to those of the block-copolymer template films (see Figure).

    17. Synergistic Effect of Inorganic and Organic Components on Solid Acid/Base Properties of Organosiloxane-Based Inorganic–Organic Hybrid Materials (pages 2596–2599)

      S. Katayama, Y. Nonaka, K. Iwata, Y. Kubo and N. Yamada

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200401645

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      Solid acid/base properties of organosiloxane-based inorganic–organic hybrid materials are reported. The organic groups bonded to silicon in organosiloxane networks are found to synergistically affect the solid acid/base properties arising from inorganic components (see Figure). This synergistic effect may result in innovative materials with applications in fast proton conductors, selective catalysts, efficient membranes, high-sensitivity sensors, and selective absorbents.

    18. Combinatorial Material Mechanics: High-Throughput Polymer Synthesis and Nanomechanical Screening (pages 2599–2604)

      C. A. Tweedie, D. G. Anderson, R. Langer and K. J. Van Vliet

      Article first published online: 29 SEP 2005 | DOI: 10.1002/adma.200501142

      Thumbnail image of graphical abstract

      Combinatorial materials science requires parallel advances in materials characterization. A high-throughput nanoscale synthesis/nanomechanical profiling approach capable of accurately screening the mechanical properties of 1,700 photopolymerizable materials (see Figure, scale bar: 100 μm) within a large, discrete polymer library is presented. This approach enables rapid correlation of polymer composition, processing, and structure with mechanical performance metrics.

    19. Surface-Nucleated Assembly of Fibrillar Extracellular Matrices (pages 2604–2608)

      J. R. Capadona, T. A. Petrie, K. P. Fears, R. A. Latour, D. M. Collard and A. J. García

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200500959

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      Synthetic surfaces, presenting a covalently immobilized oligopeptide sequence (FN13) from the self-assembly domain of fibronectin (FN), nucleate and template the assembly of robust fibrillar extracellular matrices. These matrices contain fibronectin and type I collagen (COL), as shown in the Figure, and exhibit increased cell-proliferation rates.

    20. Ambipolar Field-Effect Transistors Based on Solution-Processable Blends of Thieno[2,3-b]thiophene Terthiophene Polymer and Methanofullerenes (pages 2608–2612)

      M. Shkunov, R. Simms, M. Heeney, S. Tierney and I. McCulloch

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200500890

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      Thin-film field-effect transistors showing n- and p-type conduction under different bias conditions are produced from solution-processable ambipolar blends of thieno[2,3-b]thiophene terthiophene polymer and phenyl C61 butyric acid methyl ester (see Figure). Balanced charge transport in this blend is achieved by treating the insulator interface with alkyl-chain silanes. Complementary-like inverters have been fabricated on a single substrate, showing a maximum gain of 65.

    21. Enzyme-Mediated Degradation of Peptide-Amphiphile Nanofiber Networks (pages 2612–2617)

      H.-W. Jun, V. Yuwono, S. E. Paramonov and J. D. Hartgerink

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200500855

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      Peptide-amphiphile nanofibers are prepared that incorporate a peptide sequence permitting enzyme-mediated degradation (see Figure). Cleavage of the peptide sequence results in breakdown of the nanostructure and, consequently, the mechanical properties. This novel elastic nanofiber network is able to encapsulate dental pulp cells, supporting their proliferation and migration, and mimics several key properties of natural extracellular matrix.

    22. Nanoparticle-Induced Phase Transitions in Diblock-Copolymer Films (pages 2618–2622)

      B. J. Kim, J. J. Chiu, G.-R. Yi, D. J. Pine and E. J. Kramer

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200500502

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      Films of a symmetric A–B diblock copolymer and A-coated Au nanoparticles cast from a selective solvent for A develop a lamellar surface layer. The surface layers have a low volume fraction of nanoparticles in the A lamellae atop a substrate layer of B cylinders/spheres in an A matrix containing a larger volume fraction of nanoparticles (see Figure). This arrangement thus induces an order–order transition between block-copolymer phases as their concentration is increased.

    23. Nanoporous, Ultralow-Dielectric- Constant Fluoropolymer Films from Agglomerated and Crosslinked Hollow Nanospheres of Poly(pentafluorostyrene)-block-Poly(divinylbenzene) (pages 2622–2626)

      G.-D. Fu, Z. Shang, L. Hong, E.-T. Kang and K.-G. Neoh

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200500762

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      Nanoporous fluoropolymer films with dielectric constants below 2 are prepared via consecutive surface-initiated atom transfer radical polymerizations of pentafluorostyrene (PFS) and divinylbenzene (DVB) on silica nanospheres. After agglomeration of the nanospheres, crosslinking of the nanospheres by UV, and removal of the silica cores (see Figure), a nanoporous fluoropolymer film with a dielectric constant as low as 1.7 is formed.

    24. Cylindrical Silver Nanowires: Preparation, Structure, and Optical Properties (pages 2626–2630)

      X. M. Sun and Y. D. Li

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200500957

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      Cylindrical and pentagonal Ag nanowires (see Figure) are selectively prepared in amorphous carbonaceous sheaths via a controlled hydrothermal reaction. Results indicate that the amorphous coating layer is responsible for the cross-section symmetry selected synthesis. The distinctive optical properties measured fit well with the theoretical predictions, and applications in electronic nanodevices are envisaged.

    25. Local Conductivity Effects in Polymer Electrolytes (pages 2630–2634)

      A. J. Bhattacharyya, J. Fleig, Y.-G. Guo and J. Maier

      Article first published online: 15 SEP 2005 | DOI: 10.1002/adma.200500926

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      Room-temperature area mapping of polymer electrolyte films at the nanoscale reveals considerable heterogeneity, with the positional ionic conductivity varying up to four orders of magnitude. Measurements indicate the presence of a bimodal conductivity distribution (see Figure), with highly conducting regions being amorphous but non-percolating at room temperature.

    26. Road Map for the Controlled Synthesis of CdSe Nanowires, Nanobelts, and Nanosaws—A Step Towards Nanomanufacturing (pages 2635–2639)

      C. Ma and Z. L. Wang

      Article first published online: 29 SEP 2005 | DOI: 10.1002/adma.200500805

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      The first systematic study on the growth of one-dimensional CdSe nanostructures (see Figure) using a vapor–liquid–solid process by varying a wide range of experimental conditions is reported. The results yield a road map for the controlled growth of CdSe nanowires, nanobelts, and nanosaws, and it gives the guidance and “menu” for scaling up the synthesis of CdSe nanostructures.

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