Advanced Functional Materials

Cover image for Vol. 16 Issue 7

May, 2006

Volume 16, Issue 7

Pages 857–988

    1. Cover Picture: White Electroluminescence from a Single-Polymer System with Simultaneous Two-Color Emission: Polyfluorene as the Blue Host and a 2,1,3-Benzothiadiazole Derivative as the Orange Dopant (Adv. Funct. Mater. 7/2006)

      J. Liu, Q. G. Zhou, Y. X. Cheng, Y. H. Geng, L. X. Wang, D. G. Ma, X. B. Jing and F. S. Wang

      Article first published online: 21 APR 2006 | DOI: 10.1002/adfm.200690024

      A highly efficient white electroluminescent polymer is developed by incorporating an orange-light-emitting unit into the main chain of a blue-light-emitting polymer (see figure and cover). The electroluminescence (EL) efficiency can be improved by enhancing the photoluminescence efficiency of either the orange or blue species. A single-layer device of the polymer achieves a luminance efficiency of 8.99 cd A–1 and a power efficiency of 5.75 lm W–1.

    2. Inside Front Cover: Three-Dimensionally Ordered Gold Nanocrystal/Silica Superlattice Thin Films Synthesized via Sol–Gel Self-Assembly (Adv. Funct. Mater. 7/2006)

      H. Fan, A. Wright, J. Gabaldon, A. Rodriguez, C. J. Brinker and Y.-B. Jiang

      Article first published online: 21 APR 2006 | DOI: 10.1002/adfm.200690025

      Ordered, 3D, transparent nanocrystal superlattices in inorganic silica and silsesquioxane frameworks can be synthesized via a simple and general method. The superlattice films are formed by self-assembly of nanocrystal micelles with silica or organosilsesquioxane under acidic sol–gel conditions by spin-coating (see figure and inside cover). The resulting films exhibit face-centered cubic mesostructures.

    3. Contents: Adv. Funct. Mater. 7/2006 (pages 857–863)

      Article first published online: 21 APR 2006 | DOI: 10.1002/adfm.200690022

    4. Recent Advances in the Design of Polymerizable Lyotropic Liquid-Crystal Assemblies for Heterogeneous Catalysis and Selective Separations (pages 865–878)

      D. L. Gin, X. Lu, P. R. Nemade, C. S. Pecinovsky, Y. Xu and M. Zhou

      Article first published online: 14 MAR 2006 | DOI: 10.1002/adfm.200500280

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      Organic lyotropic liquid-crystal (LLC) assemblies mimic molecular sieves in their nanoporous structures and their ability to incorporate catalytic functional groups. This article focuses on recent advances made by the research group of D. L. Gin in incorporating new catalytic properties into polymerizable LLC assemblies and studying the molecular-transport properties of the crosslinked networks.

    5. Structural and Electrostatic Complexity at a Pentacene/Insulator Interface (pages 879–884)

      K. Puntambekar, J. Dong, G. Haugstad and C. D. Frisbie

      Article first published online: 23 MAR 2006 | DOI: 10.1002/adfm.200500816

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      Line dislocations and correlated electrostatic-potential variations at the interface between the organic semiconductor pentacene and the insulator silicon dioxide—commonly used in thin-film transistors—are revealed by scanning probe microscopy combined with chemical etching (see figure).

    6. Double-Inverse-Opal Photonic Crystals: The Route to Photonic Bandgap Switching (pages 885–890)

      T. Ruhl, P. Spahn, C. Hermann, C. Jamois and O. Hess

      Article first published online: 21 MAR 2006 | DOI: 10.1002/adfm.200600068

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      Silica/polymer core/shell particles are used for preparing double-inverse-opal photonic crystals. This structure contains a movable silica sphere in each pore of an inverse opal backbone (see figure) that strongly modifies its optical properties: infiltration causes switching between a diffusive and a photonic behavior. Computational simulation shows that shifting the spheres enables photonic bandgap switching.

    7. Three-Dimensionally Ordered Gold Nanocrystal/Silica Superlattice Thin Films Synthesized via Sol–Gel Self-Assembly (pages 891–895)

      H. Fan, A. Wright, J. Gabaldon, A. Rodriguez, C. J. Brinker and Y.-B. Jiang

      Article first published online: 23 MAR 2006 | DOI: 10.1002/adfm.200500603

      Thumbnail image of graphical abstract

      Ordered, 3D, transparent nanocrystal superlattices in inorganic silica and silsesquioxane frameworks can be synthesized via a simple and general method. The superlattice films are formed by self-assembly of nanocrystal micelles with silica or organosilsesquioxane under acidic sol–gel conditions by spin-coating (see figure and inside cover). The resulting films exhibit face-centered cubic mesostructures.

    8. Template-Free Preparation of Hollow Sb2S3 Microspheres as Supports for Ag Nanoparticles and Photocatalytic Properties of the Constructed Metal–Semiconductor Nanostructures (pages 896–902)

      X. B. Cao, L. Gu, L. J. Zhuge, W. J. Gao, W. C. Wang and S. F. Wu

      Article first published online: 24 MAR 2006 | DOI: 10.1002/adfm.200500422

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      A simple Ostwald ripening route is developed to prepare hollow Sb2S3 spheres. Silver nanoparticles are incorporated into the spheres, thereby constructing functional metal–semiconductor nanostructures (see figure) that exhibit an intense absorption both in the UV and visible spectral regions and show high photocatalytic activity.

    9. Uniform Hexagonal Plates of Vaterite CaCO3 Mesocrystals Formed by Biomimetic Mineralization (pages 903–908)

      A.-W. Xu, M. Antonietti, H. Cölfen and Y.-P. Fang

      Article first published online: 14 MAR 2006 | DOI: 10.1002/adfm.200500716

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      Hexagonal plates of vaterite CaCO3mesocrystals (see figure) with a narrow size distribution are grown via aggregation-mediated pathways in the presence of an N-trimethylammonium derivative of hydroxyethyl cellulose. The mesoscale transformation involving cooperative reorganization of coupled inorganic and organic components could provide new insights into biomineralization mechanisms.

    10. Thiophenol-Modified CdS Nanoparticles Enhance the Luminescence of Benzoxyl Dendron- Substituted Polyfluorene Copolymers (pages 909–916)

      C.-H. Chou, H.-S. Wang, K.-H. Wei and J. Y. Huang

      Article first published online: 14 MAR 2006 | DOI: 10.1002/adfm.200500354

      Incorporating thiophenol-modified CdS nanoparticles in the benzoxyl-dendritic structure of a copolyfluorene substantially improves its light-emission efficiency. The enhanced photoluminescence and electroluminescence arise from the reduction of the degree of energy transfer from excited polymer chains to neighboring chains in the ground state, i.e., the interpolymer chain distance increases when CdS nanoparticles are present. Unlike conventional conjugated polymers investigated so far, device applications of these materials are not hampered by aggregation in the solid state.

    11. X-Shaped Electroactive Molecular Materials Based on Oligothiophene Architectures: Facile Synthesis and Photophysical and Electrochemical Properties (pages 917–925)

      X. B. Sun, Y. Q. Liu, S. Y. Chen, W. F. Qiu, G. Yu, Y. Q. Ma, T. Qi, H. J. Zhang, X. J. Xu and D. B. Zhu

      Article first published online: 14 MAR 2006 | DOI: 10.1002/adfm.200500463

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      Novel X-shaped conjugated oligothiophenes (see figure) with C4-substituted structures have been developed using a facile synthetic route. Their optoelectronic properties are electronically fine-tuned by manipulating segments of their branches. In addition, electroactive polymers have been obtained by electrochemical polymerization and their optical properties have been investigated.

    12. Electric-Field-Induced Pattern Morphologies in Thin Liquid Films (pages 926–934)

      N. E. Voicu, S. Harkema and U. Steiner

      Article first published online: 21 MAR 2006 | DOI: 10.1002/adfm.200500470

      Thumbnail image of graphical abstract

      Confined polymer films are destabilized by an electric field. The evolution of the resulting pattern (see figure) is studied as a function of the confinement. The final polymer pattern is a result of the interplay of the initial instability wavelength and the degree of lateral coarsening. This interplay also governs the replication of a laterally structured electric field.

    13. Efficient Luminescence from Rare-Earth Fluoride Nanoparticles with Optically Functional Shells (pages 935–942)

      M. M. Lezhnina, T. Jüstel, H. Kätker, D. U. Wiechert and U. H. Kynast

      Article first published online: 21 MAR 2006 | DOI: 10.1002/adfm.200500197

      Thumbnail image of graphical abstract

      In order to extend the high potential of rare-earth fluorides for vacuum-UV- and near-IR-excitation applications into the nanoscale regime, bifunctional shells are applied. These shells are protective on one hand, and actively participate in the luminescence process, as illustrated in the figure, on the other. Next to applications as vacuum-UV-driven phosphors and upconversion materials, nanofluorides can act as optically active components in hybrid materials.

    14. Electrophoretic Separation of Nanoparticles with a Discrete Number of Functional Groups (pages 943–948)

      R. A. Sperling, T. Pellegrino, J. K. Li, W. H. Chang and W. J. Parak

      Article first published online: 12 APR 2006 | DOI: 10.1002/adfm.200500589

      Thumbnail image of graphical abstract

      Bifunctional poly(ethylene glycol) (PEG) molecules can be covalently linked to polymer-coated inorganic nanocrystals. With an appropriate molecular weight, the exact number of attached molecules and thus the exact number of free functional groups per particle can be controlled by gel electrophoresis (see figure). Conjugates of nanoparticles with one, two, and three PEG molecules per nanoparticle have been separated.

    15. Polymer Light-Emitting Electrochemical Cells: The Formation and Effects of Doping-Induced Micro Shorts (pages 949–956)

      J.-H. Shin, S. Xiao and L. Edman

      Article first published online: 27 MAR 2006 | DOI: 10.1002/adfm.200500612

      Thumbnail image of graphical abstract

      Planar polymer light-emitting electrochemical cells with large interelectrode gaps of up to 1 mm have been investigated. Diffuse needlelike doping is shown to initiate at the electrodes (left and middle panels in figure), and an uneven discontinuous emission zone is subsequently formed next to the negative electrode (right panel). Doping-induced micro shorts strongly influence the device performance.

    16. White Electroluminescence from a Single-Polymer System with Simultaneous Two-Color Emission: Polyfluorene as the Blue Host and a 2,1,3-Benzothiadiazole Derivative as the Orange Dopant (pages 957–965)

      J. Liu, Q. G. Zhou, Y. X. Cheng, Y. H. Geng, L. X. Wang, D. G. Ma, X. B. Jing and F. S. Wang

      Article first published online: 24 MAR 2006 | DOI: 10.1002/adfm.200500761

      Thumbnail image of graphical abstract

      A highly efficient white electroluminescent polymer is developed by incorporating an orange-light-emitting unit into the main chain of a blue-light-emitting polymer (see figure and cover). The electroluminescence (EL) efficiency can be improved by enhancing the photoluminescence efficiency of either the orange or blue species. A single-layer device of the polymer achieves a luminance efficiency of 8.99 cd A–1 and a power efficiency of 5.75 lm W–1.

    17. Comparison of Charge-Carrier Transport in Thin Films of Spiro-Linked Compounds and Their Corresponding Parent Compounds (pages 966–974)

      T. P. I. Saragi, T. Fuhrmann-Lieker and J. Salbeck

      Article first published online: 12 APR 2006 | DOI: 10.1002/adfm.200500361

      Thumbnail image of graphical abstract

      Charge-carrier transport in thin films of spiro-linked compounds is compared to that of the corresponding parent compounds. The performance of films of spiro-linked compounds is maintained, in contrast to that of the parent compounds, which is reduced in a matter of hours, even if the sample is kept in a continuously evacuated chamber (see figure).

    18. A Vapor–Liquid–Solid Mechanism for Growing 3C-SiC Single-Domain Layers on 6H-SiC(0001) (pages 975–979)

      M. Soueidan and G. Ferro

      Article first published online: 27 MAR 2006 | DOI: 10.1002/adfm.200500597

      Thumbnail image of graphical abstract

      Single-domain 3C-SiC layers can be grown on a 6H-SiC(0001) substrate via a vapor–liquid–solid mechanism in a Ge–Si melt. The surprising occurrence of the cubic polytype, even on off-axis-oriented substrates, can be explained by step-edge enrichment, which hinders substrate polytype replication by step-controlled epitaxy. The figure (36 Normaski optical microscopy images) shows an example of such a layer over an area as large as 1 cm × 1 cm.

    19. Stable Blue Emission from a Polyfluorene/Layered-Compound Guest/Host Nanocomposite (pages 980–986)

      E. Aharon, A. Albo, M. Kalina and G. L. Frey

      Article first published online: 12 APR 2006 | DOI: 10.1002/adfm.200500458

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      Intercalation of a conjugated polymer, poly(9,9-dioctylfluorene), into the galleries of layered MoS2 and SnS2 (see figure) stabilizes its blue photoluminescence and electroluminescence by inhibiting π–π stacking while preserving the planar conformation of the conjugated polymer. Results show that the appearance of undesirable green emission, as observed in pristine polymer films, is suppressed by incorporating the polymer into the inorganic matrix.

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