Advanced Functional Materials

Cover image for Vol. 15 Issue 5

May, 2005

Volume 15, Issue 5

Pages 715–878

    1. Cover Picture: Fabrication of Multicomponent Microsystems by Directed Three-Dimensional Self-Assembly (Adv. Funct. Mater. 5/2005)

      W. Zheng and H. O. Jacobs

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200590016

      A directed self-assembly process for fabricating three-dimensional microsystems that contain non-identical parts is demonstrated. Three-component microsystems containing AlGaInP/GaAs light-emitting diodes have been self-assembled and self-packaged (see Figure and cover) in a two-step sequence to form a three-dimensional circuit path permitting operation of the final device.

    2. Inside Front Cover: Freely Suspended Layer-by-Layer Nanomembranes: Testing Micromechanical Properties (Adv. Funct. Mater. 5/2005)

      S. Markutsya, C. Jiang, Y. Pikus and V. V. Tsukruk

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200590017

      Exceptional micromechanical properties of free-standing, compliant nanomembranes, composed of gold nanoparticles sandwiched between polyelectrolyte multilayers, are reported. Resonance-frequency and bulging tests (Newton rings are shown in the Figure and inside cover) and point-load nanodeflection are used to study these nanocomposite membranes, which show extraordinary elastic properties and moduli of 5–10 GPa.

    3. Inverted-Colloidal-Crystal Hydrogel Matrices as Three-Dimensional Cell Scaffolds (pages 725–731)

      Y. Zhang, S. Wang, M. Eghtedari, M. Motamedi and N. A. Kotov

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400325

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      Successful engineering of functional tissues requires new three-dimensional (3D) scaffolds that can provide optimum microenvironment for cell development. A new class of 3D scaffolds, such as that shown in the Figure, with a high degree of organization and unique topography is fabricated from polyacrylamide hydrogel molded by colloidal crystals.

    4. Fabrication of Multicomponent Microsystems by Directed Three-Dimensional Self-Assembly (pages 732–738)

      W. Zheng and H. O. Jacobs

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400595

      Thumbnail image of graphical abstract

      A directed self-assembly process for fabricating three-dimensional microsystems that contain non-identical parts is demonstrated. Three-component microsystems containing AlGaInP/GaAs light-emitting diodes have been self-assembled and self-packaged (see Figure and cover) in a two-step sequence to form a three-dimensional circuit path permitting operation of the final device.

    5. Silicon Chip Interfaced with a Geometrically Defined Net of Snail Neurons (pages 739–744)

      M. Merz and P. Fromherz

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400316

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      Networks of snail neurons are grown in grooves of a polyester resist on a silicon chip as shown in the Figure. Their electrical activity is controlled by two-way contacts with capacitors and transistors. The bottom-up design of topologically defined neuronal nets with non-invasive supervision from the semiconductor chip reveals a fundamental problem of yield.

    6. Polymer Solar Cells Based on a Low-Bandgap Fluorene Copolymer and a Fullerene Derivative with Photocurrent Extended to 850 nm (pages 745–750)

      F. Zhang, E. Perzon, X. Wang, W. Mammo, M. R. Andersson and O. Inganäs

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400416

      Thumbnail image of graphical abstract

      A low-bandgap alternating fluorene copolymer (structure, see Figure) is synthesized and characterized in solar cells combined with a fullerene derivative. Photocurrent of 3.0 mA cm–2, photovoltage of 0.78 V, and power conversion efficiency of 0.9 % (see Figure) are achieved under illumination of air mass 1.5.

    7. Efficient Photosensitization and High Optical Gain in a Novel Quantum-Dot-Sensitized Hybrid Photorefractive Nanocomposite at a Telecommunications Wavelength (pages 751–756)

      K. Roy Choudhury, Y. Sahoo, S. Jang and P. N. Prasad

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400396

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      An organic–inorganic hybrid polymeric photorefractive nanocomposite operating at the telecommunications wavelength of 1.34 μm is developed. Highly monodisperse PbS nanocrystals synthesized via a hot colloidal route are used as the photosensitizer. The composite material exhibits greatly enhanced photocharge-generation quantum efficiency. A pronounced two-beam coupling effect (as seen in Figure) resulted in very high optical gain.

    8. Growth of Wurtzite ZnS Micrometer-Sized Diskettes and Nanoribbon Arrays with Improved Luminescence (pages 757–762)

      J. Hu, Y. Bando, J. Zhan and D. Golberg

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400084

      Thumbnail image of graphical abstract

      Wurtzite ZnS micrometer-sized diskettes and ZnS nanoribbon arrays are grown (see Figure) and a significant enhancement in luminescence is observed. The structures may serve as model systems for studying the optical and electronic properties of ZnS material, and may also be treated as building blocks for two- or three-dimensional arrays. They are promising candidates for fabricating novel electronic and optoelectronic devices.

    9. Down/Up Conversion in Ln3+-Doped YF3 Nanocrystals (pages 763–770)

      R. X. Yan and Y. D. Li

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200305044

      Thumbnail image of graphical abstract

      Highly functionalized Ln3+-doped YF3 nanoparticles, synthesized by doping different lanthanide ions, show both down- and up-conversion optical properties. In particular, an unusually strong blue up-conversion emission under 980 nm excitation has been observed and a three-photon up-conversion mechanism has been proposed.

    10. Freely Suspended Layer-by-Layer Nanomembranes: Testing Micromechanical Properties (pages 771–780)

      S. Markutsya, C. Jiang, Y. Pikus and V. V. Tsukruk

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400149

      Thumbnail image of graphical abstract

      Exceptional micromechanical properties of free-standing, compliant nanomembranes, composed of gold nanoparticles sandwiched between polyelectrolyte multilayers, are reported. Resonance-frequency and bulging tests (Newton rings are shown in the Figure and inside cover) and point-load nanodeflection are used to study these nanocomposite membranes, which show extraordinary elastic properties and moduli of 5–10 GPa.

    11. Growth of Single-Crystalline Wurtzite Aluminum Nitride Nanotips with a Self-Selective Apex Angle (pages 781–786)

      S. C. Shi, C. F. Chen, S. Chattopadhyay, Z. H. Lan, K. H. Chen and L. C. Chen

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400324

      Thumbnail image of graphical abstract

      Single-crystal, wurtzite aluminum nitride nanotips (see Figure, scanning electron microscope image (left) and computer-generated image (right)) with self-selected apex angles of 18° and apex diameters of ∼ 2 nm are produced by vaporizing pure aluminum powders in flowing ammonia at 950 °C by a process of vapor transport and condensation.

    12. Fluorescence Modulation in Polymer Bilayers Containing Fluorescent and Photochromic Dopants (pages 787–794)

      M. Tomasulo, S. Giordani and F. M. Raymo

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400381

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      The photoisomerization of a photochrome modulates the emission intensity of a fluorophore when the two compounds dope overlapping polymer films. Under these conditions, the state of the photochrome can be written with optical inputs and read with fluorescence outputs. Thus, light can be controlled with light relying on the emission and absorption properties of compatible organic molecules (see Figure).

    13. Compositional Dependence of the Performance of Poly(p-phenylene vinylene):Methanofullerene Bulk-Heterojunction Solar Cells (pages 795–801)

      V. D. Mihailetchi, L. J. A. Koster, P. W. M. Blom, C. Melzer, B. de Boer, J. K. J. van Duren and R. A. J. Janssen

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400345

      Thumbnail image of graphical abstract

      The performance of polymer–fullerene bulk-heterojunction solar cells has been investigated as a function of fullerene content. Electron and hole mobilities were measured separately in the blend (see Figure). The maximum power conversion efficiency is achieved at a high fullerene fraction, where light harvesting is less effective, which is explained using numerical simulations including the measured electron and hole mobilities.

    14. Highly Ordered Platinum-Nanotubule Arrays for Amperometric Glucose Sensing (pages 803–809)

      J. H. Yuan, K. Wang and X. H. Xia

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400321

      Thumbnail image of graphical abstract

      Taking advantage of the different electrochemical reaction mechanisms of glucose and interferents, highly ordered platinum-nanotubule array electrodes electrodeposited via a template technique have been successfully used to detect glucose with high sensitivity, selectivity, and stability (see Figure).

    15. Highly Efficient Hybrid Solar Cells Based on an Octithiophene–GaAs Heterojunction (pages 810–817)

      J. Ackermann, C. Videlot, A. El Kassmi, R. Guglielmetti and F. Fages

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200305142

      Thumbnail image of graphical abstract

      Hybrid solar cells based on a heterojunction of octithiophene (8T) and monocrystalline GaAs have been developed (see Figure), showing solar-energy conversion efficiencies of up to 4.2 %. Clear evidence for a strong influence of the film morphology on the photocurrent collection length in 8T is given.

    16. Oligothiophene-Functionalized Truxene: Star-Shaped Compounds for Organic Field-Effect Transistors (pages 818–822)

      Y. M. Sun, K. Xiao, Y. Q. Liu, J. L. Wang, J. Pei, G. Yu and D. B. Zhu

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400380

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      Organic field-effect transistors based on oligothiophene-functionalized truxene derivatives (13, see Figure) as novel star-shaped organic semiconductors have been fabricated. A high mobility, up to 1.03 ×10–3 cm2 V–1 s–1, and an on/off ratio of about 103 for compound 1 have been achieved.

    17. Spin-Coated Periodic Mesoporous Organosilica Thin Films—Towards a New Generation of Low-Dielectric-Constant Materials (pages 823–829)

      B. D. Hatton, K. Landskron, W. Whitnall, D. D. Perovic and G. A. Ozin

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400221

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      Periodic mesoporous organosilica (PMO) thin films have been produced from bridged silsesquioxane precursors (see Figure) using evaporation-induced self-assembly (EISA). The authors report the structural characterization, and mechanical and dielectric properties of some PMO thin films, which show that they have a promising combination of properties for low- dielectric-constant applications.

    18. Transparent Nanocomposites of Radiopaque, Flame-Made Ta2O5/SiO2 Particles in an Acrylic Matrix (pages 830–837)

      H. Schulz, L. Mädler, S. E. Pratsinis, P. Burtscher and N. Moszner

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400234

      Thumbnail image of graphical abstract

      Highly transparent composites containing flame-made, radiopaque, ceramic fillers have been made. The performance of the composite is controlled by selecting the crystallinity (see Figure), dispersion of elements, refractive index, particle size, and composition of the mixed oxides.

    19. Praseodymium Silicate as a High-k Dielectric Candidate: An Insight into the Pr2O3-Film/Si-Substrate Interface Fabricated Through a Metal–Organic Chemical Vapor Deposition Process (pages 838–845)

      R. Lo Nigro, R. G. Toro, G. Malandrino, G. G. Condorelli, V. Raineri and I. L. Fragalà

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200300346

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      Detailed studies of the metal–organic chemical vapor deposition (MOCVD) fabrication of praseodynmium oxide-containing films indicate that the process occurs under a kinetic regime and that a silicate phase (Pr–O–Si in the Figure) is formed because of interactions at the film/substrate interface.

    20. Dynamic Catalysis in Aerobic Oxidation by Sol–Gel Living Materials (pages 846–850)

      R. Ciriminna, S. Campestrini, M. Carraro and M. Pagliaro

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400409

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      Hybrid organic–inorganic silica glasses doped with perruthenate are living materials: upon months of aging at room temperature they become the most active and selective ruthenium-based aerobic catalysts for alcohol dehydrogenations in organic solvent or in compressed CO2 (e.g., see aerobic oxidation of benzyl alcohol to benzaldehyde in the Figure) thus far reported.

    21. Co3O4 Nanomaterials in Lithium-Ion Batteries and Gas Sensors (pages 851–857)

      W. Y. Li, L. N. Xu and J. Chen

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400429

      Thumbnail image of graphical abstract

      Co3O4 nanotubes (see Figure), nanorods, and nanoparticles are used as the anode materials of lithium-ion batteries. The results show that the Co3O4 nanotubes prepared via a porous alumina-template method display high discharge capacity and superior cycling reversibility. Furthermore, Co3O4 nanotubes exhibit excellent sensitivity to hydrogen and alcohol owing to their hollow nanostructured character.

    22. Bifunctional Carbon Nanotubes by Sidewall Protection (pages 858–864)

      N. Chopra, M. Majumder and B. J. Hinds

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400399

      Thumbnail image of graphical abstract

      A vertically aligned array of multiwalled carbon nanotubes (MWCNTs) is impregnated with a polystyrene matrix, allowing independent functionalization of each end of the CNTs, as shown in the Figure. The polystyrene matrix prevents sidewall oxidation and bifunctionality is achieved by simply floating alternate sides of the CNT membrane on different reaction solutions.

    23. Combined Surface and Volume Templating of Highly Porous Nanocast Carbon Monoliths (pages 865–871)

      A.-H. Lu, J.-H. Smått and M. Lindén

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200305183

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      Nanocast carbon monoliths with a controlled bi- or trimodal pore-size distribution and a fully interconnected pore system have been prepared and characterized (see Figure). A combined surface and volume templating approach is shown to be a versatile means for nanocasting macroscopic objects with multimodal porosity.

    24. High-Performance Solution-Processable Poly(p-phenylene vinylene)s for Air-Stable Organic Field-Effect Transistors (pages 872–876)

      A. J. J. M. van Breemen, P. T. Herwig, C. H. T. Chlon, J. Sweelssen, H. F. M. Schoo, E. M. Benito, D. M. de Leeuw, C. Tanase, J. Wildeman and P. W. M. Blom

      Version of Record online: 26 APR 2005 | DOI: 10.1002/adfm.200400445

      Thumbnail image of graphical abstract

      Symmetrically substituted poly(p-phenylene vinylene)s (PPVs) with linear alkyl chains (e.g., R1, R2 = n-C11H23, R3 = n-C18H37 in Figure) are found to provide the highest charge-carrier mobilitites when used in organic field-effect transistors (as compared with unsymmetrical substitution or branched side chains). Annealing at 110 °C further improves mobility to ∼10-2 cm2V-1s-1 (see Figure) and provides transistors which are stable in air and in the dark.

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