Advanced Functional Materials

Cover image for Vol. 15 Issue 10

October, 2005

Volume 15, Issue 10

Pages 1559–1729

    1. Cover Picture: TiO2 Nanoparticle–Photopolymer Composites for Volume Holographic Recording (Adv. Funct. Mater. 10/2005)

      C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen, D. J. Broer, J. Loos and R. Nussbaumer

      Version of Record online: 28 SEP 2005 | DOI: 10.1002/adfm.200590034

      Mixtures of UV-sensitive acrylates and TiO2 nanoparticles are presented for volume holographic recording. Photoinduced segregation of the nanoparticles (see Figure and cover) leads to refractive-index modulation amplitudes of up to 15.5 × 10–3, an improvement of more than a factor of four over the base material without nanoparticles. The holographic recording of submicrometer gratings has been demonstrated.

    2. Inside Front Cover: Observation of a Chiral Smectic Phase in Azobenzene-Linked Bolaamphiphiles Containing Free Sugars (Adv. Funct. Mater. 10/2005)

      S. Abraham, S. Paul, G. Narayan, S. K. Prasad, D. S. S. Rao, N. Jayaraman and S. Das

      Version of Record online: 28 SEP 2005 | DOI: 10.1002/adfm.200590035

      Macroscopic chirality in sugar-based bolaamphiphiles containing free hydroxyl groups is reported for the first time. The manifestation of the chiral smectic C* phase in the azo-containing bolaamphiphiles (see Figure and inside cover) is critically dependent on the hydrophilic–hydrophobic balance within the molecule. These results imply that mesogenic bolaamphiphiles possessing macroscopic chirality can be designed by suitable selection of aromatic linker groups.

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      Keeping Up to Date with Advanced Functional Materials (pages 1569–1570)

      K. Grieve

      Version of Record online: 28 SEP 2005 | DOI: 10.1002/adfm.200500593

      Advanced Functional Materials is receiving manuscript submissions at an ever-increasing rate and evolving as a result. These changes and general trends are presented.

    4. The Cooperative Molecular Field Effect (pages 1571–1578)

      D. Cahen, R. Naaman and Z. Vager

      Version of Record online: 13 SEP 2005 | DOI: 10.1002/adfm.200500187

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      Two-dimensional arrangements of molecules can show remarkable cooperative electronic effects. Such effects can serve to achieve direct electronic sensing of chemical and physical processes via electrostatic effects, i.e., without transfer of charge or matter between the locus of sensing and that of detection (e.g., see resistor shown in Figure).

    5. Observation of a Chiral Smectic Phase in Azobenzene-Linked Bolaamphiphiles Containing Free Sugars (pages 1579–1584)

      S. Abraham, S. Paul, G. Narayan, S. K. Prasad, D. S. S. Rao, N. Jayaraman and S. Das

      Version of Record online: 1 SEP 2005 | DOI: 10.1002/adfm.200500089

      Thumbnail image of graphical abstract

      Macroscopic chirality in sugar-based bolaamphiphiles containing free hydroxyl groups is reported for the first time. The manifestation of the chiral smectic C* phase in the azo-containing bolaamphiphiles (see Figure and inside cover) is critically dependent on the hydrophilic–hydrophobic balance within the molecule. These results imply that mesogenic bolaamphiphiles possessing macroscopic chirality can be designed by suitable selection of aromatic linker groups.

    6. Influence of Hydrogen Bonds on the Supramolecular Order of Hexa-peri-hexabenzocoronenes (pages 1585–1594)

      D. Wasserfallen, I. Fischbach, N. Chebotareva, M. Kastler, W. Pisula, F. Jäckel, M. D. Watson, I. Schnell, J. P. Rabe, H. W. Spiess and K. Müllen

      Version of Record online: 22 AUG 2005 | DOI: 10.1002/adfm.200500124

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      Addition of hydrogen-bonding motifs to the periphery of hexa-peri-hexabenzocoronenes has been carried out in order to study the effect of hydrogen bonding on the already pronounced columnar π-stacking (see Figure). The thermal properties as well as the supramolecular order of the materials can be improved; such improvement is a prerequisite for successful implementation in electronic devices.

    7. Martensitic Phase Transformation of Isolated HfO2, ZrO2, and HfxZr1 – xO2 (0 < x < 1) Nanocrystals (pages 1595–1602)

      J. Tang, F. Zhang, P. Zoogman, J. Fabbri, S.-W. Chan, Y. Zhu, L. E. Brus and M. L. Steigerwald

      Version of Record online: 24 AUG 2005 | DOI: 10.1002/adfm.200500050

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      Concomitant phase and shape changes observed in the synthesis of HfO2 and Hf-rich HfxZr1 – xO2 nanocrystals are determined to result from the martensitic transformation of isolated nanocrystals in a hot liquid (see Figure), where twinning plays a crucial role. Post-synthesis, heat-induced phase transformations of the HfxZr1 – xO2 (0 < x < 1) nanocrystals are also studied.

    8. A New Understanding of Au-Assisted Growth of III–V Semiconductor Nanowires (pages 1603–1610)

      K. A. Dick, K. Deppert, L. S. Karlsson, L. R. Wallenberg, L. Samuelson and W. Seifert

      Version of Record online: 22 AUG 2005 | DOI: 10.1002/adfm.200500157

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      The growth behavior of III–V semiconductor nanowires and nano- trees assisted by Au particles is considered (see Figure). The particle is not inert with respect to the semiconductor, as often assumed, but interacts with it. The growth and morphology of these structures are determined by the temperature-dependent solid-phase interaction between the Au particle and each of the III–V materials discussed, which include GaP, GaAs, InP, and InAs.

    9. Fabrication of Thermoresponsive Plasmonic Microspheres with Long-Term Stability from Hydrogel Spheres (pages 1611–1616)

      M. Kuang, D. Wang and H. Möhwald

      Version of Record online: 1 SEP 2005 | DOI: 10.1002/adfm.200500141

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      Thermoresponsive plasmonic microspheres have been constructed by embedding gold nanoparticles into thermoresponsive hydrogel spheres with high efficiency due to the size similarity between the gel pores and the gold nanoparticles (see Figure). The resultant composite spheres show both a thermoresponsive swelling behavior and an environmentally responsive plasmon resonance.

    10. Thermally Stable, Efficient Polymer Solar Cells with Nanoscale Control of the Interpenetrating Network Morphology (pages 1617–1622)

      W. Ma, C. Yang, X. Gong, K. Lee and A. J. Heeger

      Version of Record online: 1 SEP 2005 | DOI: 10.1002/adfm.200500211

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      Polymer solar cells with power-conversion efficiency approaching 5 % and remarkable thermal stability are demonstrated after postproduction thermal annealing at 150 °C. The higher efficiency results from thermally induced morphology modification and improved transport across the interface between the bulk heterojunction material and the Al electrode.

    11. TiO2 Nanoparticle–Photopolymer Composites for Volume Holographic Recording (pages 1623–1629)

      C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen, D. J. Broer, J. Loos and R. Nussbaumer

      Version of Record online: 5 SEP 2005 | DOI: 10.1002/adfm.200500095

      Thumbnail image of graphical abstract

      Mixtures of UV-sensitive acrylates and TiO2 nanoparticles are presented for volume holographic recording. Photoinduced segregation of the nanoparticles (see Figure and cover) leads to refractive-index modulation amplitudes of up to 15.5 × 10–3, an improvement of more than a factor of four over the base material without nanoparticles. The holographic recording of submicrometer gratings has been demonstrated.

    12. Generation of Compositional-Gradient Structures in Biodegradable, Immiscible, Polymer Blends by Intermolecular Hydrogen-Bonding Interactions (pages 1630–1634)

      B. Hexig, H. Alata, N. Asakawa and Y. Inoue

      Version of Record online: 1 SEP 2005 | DOI: 10.1002/adfm.200400550

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      Compositional-gradient structures have been created in a biodegradable, immiscible, polyester/polyether blend film by using a low-molecular-weight compound, 4,4′-thiodiphenal (TDP), to mediate hydrogen-bonding interactions (as schematically shown in the Figure).

    13. Amino-Functionalized Silica Membranes for Enhanced Carbon Dioxide Permeation (pages 1635–1640)

      B. A. McCool and W. J. DeSisto

      Version of Record online: 22 AUG 2005 | DOI: 10.1002/adfm.200400293

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      Functionalization of silica membranes is important for enhancing surface interactions with specific chemicals in order to enhance separations. The ability of amino functionalization to enhance CO2 transport in silica membranes using three different functionalization techniques is investigated (see Figure). It is found that high loadings of amino groups, in which interaction with the silica surface is minimized, results in the highest CO2 transport.

    14. Polyamidoamine Dendrimers Prepared Inside the Channels of Pore-Expanded Periodic Mesoporous Silica (pages 1641–1646)

      J. P. K. Reynhardt, Y. Yang, A. Sayari and H. Alper

      Version of Record online: 22 AUG 2005 | DOI: 10.1002/adfm.200400622

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      Polyamidoamine (PAMAM) dendrimers up to the fourth generation have been grown with unprecedentedly high loading within the channels of pore-expanded (10.6 nm) MCM-41 silica (see Figure). The dendrimers grow inside the channels with an average yield better than 99 %. The pore size and structure determine how much dendrimer growth can be achieved.

    15. The Fabrication and Characterization of Single-Component Polymeric White-Light-Emitting Diodes (pages 1647–1655)

      S. K. Lee, D.-H. Hwang, B.-J. Jung, N. S. Cho, J. Lee, J.-D. Lee and H.-K. Shim

      Version of Record online: 1 SEP 2005 | DOI: 10.1002/adfm.200500060

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      A white-light-emitting-diode, based on single-component polymer chains containing monomers that are red-, green-, and blue-light-emitting centers, has been fabricated (see Figure). It exhibits a pure white-light emission, with Commission Internationale de L'Eclairage coordinates of (0.33,0.35) that remain almost constant on changing the driving voltage.

    16. Morphology of Polymer/Liquid-Crystal Nanotubes: Influence of Confinement (pages 1656–1664)

      M. Steinhart, S. Murano, A. K. Schaper, T. Ogawa, M. Tsuji, U. Gösele, C. Weder and J. H. Wendorff

      Version of Record online: 1 SEP 2005 | DOI: 10.1002/adfm.200500139

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      Polymer/liquid-crystal nanotubes with an outer polymer and an inner discotic liquid-crystal layer (see Figure) can be fabricated by exploitation of phase separation and interfacial phenomena. The morphology and the texture depend on the thermal history and the properties of the employed templates. These structures are promising start for developing miniature device components.

    17. Enhanced Photocurrent Spectral Response in Low-Bandgap Polyfluorene and C70-Derivative-Based Solar Cells (pages 1665–1670)

      X. Wang, E. Perzon, F. Oswald, F. Langa, S. Admassie, M. R. Andersson and O. Inganäs

      Version of Record online: 16 AUG 2005 | DOI: 10.1002/adfm.200500114

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      Plastic solar cells fabricated by blending a C70-fullerene derivative, BTPF70 (see Figure), with low-bandgap polyfluorene show very promising results. BTPF70 absorbs light up to wavelengths λ ≈ 700 nm and the absorption spectrum for the composite films covers the visible and near-infrared solar spectrum, resulting in a broad photocurrent spectral-response window, 300 < λ < 1000 nm, being achieved.

    18. 2,7-Carbazolenevinylene-Based Oligomer Thin-Film Transistors: High Mobility Through Structural Ordering (pages 1671–1682)

      N. Drolet, J.-F. Morin, N. Leclerc, S. Wakim, Y. Tao and M. Leclerc

      Version of Record online: 5 SEP 2005 | DOI: 10.1002/adfm.200500168

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      Top-contact organic thin-film transistors (see Figure, inset) using 2,7-carbazolenevinylene-based oligomers as active semiconductors show hole mobilities of up to 0.3 cm2 V–1 s–1 with an excellent current modulation (Ion/Ioff) of 107. The high hole field-effect mobility in these materials is reached through molecular organization in the evaporated thin films (see Figure), making such oligomers attractive candidates for device applications.

    19. Pattern-Transfer Fidelity in Soft Lithography: The Role of Pattern Density and Aspect Ratio (pages 1683–1688)

      T.-W. Lee, O. Mitrofanov and J. W. P. Hsu

      Version of Record online: 1 SEP 2005 | DOI: 10.1002/adfm.200400295

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      High-aspect-ratio nanostructures fabricated via two-photon laser-scanning lithography are used to examine the deformation of elastomeric stamps used in soft nanolithography and the fidelity of patterns and replicas made using these stamps (see Figure). The pattern-transfer fidelity is found to be strongly affected by the pattern density, which is a more important parameter than aspect ratio to consider when discussing replicating nanostructures in soft lithography.

    20. Generation of Palladium Nanoparticles within Macrocellular Polymeric Supports: Application to Heterogeneous Catalysis of the Suzuki–Miyaura Coupling Reaction (pages 1689–1695)

      A. Desforges, R. Backov, H. Deleuze and O. Mondain-Monval

      Version of Record online: 16 AUG 2005 | DOI: 10.1002/adfm.200500146

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      Palladium nanoparticles have been heterogeneously nucleated within polymeric macrocellular supports (see Figure). Upon surface modification of both open-cell matrices and nanoparticles, the new hybrid monolith-type material allows high yields when used as a catalyst in carbon-carbon coupling reactions, compared to the well-known Pd@C catalyst, and even homogeneous catalysts.

    21. Hybrid Periodic Mesoporous Organosilicas (pages 1696–1702)

      W. Whitnall, T. Asefa and G. A. Ozin

      Version of Record online: 5 SEP 2005 | DOI: 10.1002/adfm.200500151

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      Hybrid periodic mesoporous organosilicas are presented. By adding a bridging silsesquioxane to the pore surfaces of mesoporous silicas or mesoporous organosilicas (see Figure), the pore size of the final organic–inorganic nanocomposite material can be controlled to near-angstrom-level precision, while ensuring that the added organic functional groups are chemically accessible.

    22. Hybrid Solar Cells Using a Zinc Oxide Precursor and a Conjugated Polymer (pages 1703–1707)

      W. J. E. Beek, L. H. Slooff, M. M. Wienk, J. M. Kroon and R. A. J. Janssen

      Version of Record online: 22 AUG 2005 | DOI: 10.1002/adfm.200500201

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      Spin-coating of a conjugated polymer mixed with diethylzinc from a common solution, followed by thermal annealing, results in a crystalline network of ZnO embedded in a thin polymer film that exhibits a photovoltaic effect with maximum external quantum efficiency (IPCE) of more than 25 % (see Figure). This new method produces cells with fivefold improved performance over similar hybrid cells based on amorphous TiO2.

    23. Microwave-Assisted Synthesis of Nanocrystalline MgO and Its Use as a Bacteriocide (pages 1708–1715)

      S. Makhluf, R. Dror, Y. Nitzan, Y. Abramovich, R. Jelinek and A. Gedanken

      Version of Record online: 1 SEP 2005 | DOI: 10.1002/adfm.200500029

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      Nanocrystalline particles of MgO show positive antibacterial properties for E. coli (Gram negative) and Staph. aureus (Gram positive) cultures. A clear size dependence of the nanoparticles is observed for the bactericidal studies, where the amount of eradicated bacteria is strongly dependent on the particle size. Small, electron-dense black dots have been observed in the cytoplasm of the MgO-nanoparticle-treated E. coli bacteria (see Figure).

    24. Highly Efficient Non-Doped Blue Organic Light-Emitting Diodes Based on Fluorene Derivatives with High Thermal Stability (pages 1716–1721)

      S. L. Tao, Z. K. Peng, X. H. Zhang, P. F. Wang, C.-S. Lee and S.-T. Lee

      Version of Record online: 24 AUG 2005 | DOI: 10.1002/adfm.200500067

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      The fluorene derivatives 1–3 (see Figure) are used as host-emitter layers in the fabrication of organic light-emitting diodes. The devices exhibit high efficiency (5.3 cd A–1; 3.0 lm W–1) and pure blue Commission Internationale de L'Eclairage (CIE) coordinates (x = 0.16, y = 0.22). These values are among the best ever reported for fluorescent blue-light-emitting devices.

    25. Holographic Gratings in Diblock Copolymers with Azobenzene and Mesogenic Side Groups in the Photoaddressable Dispersed Phase (pages 1722–1727)

      M. Häckel, L. Kador, D. Kropp, C. Frenz and H.-W. Schmidt

      Version of Record online: 1 SEP 2005 | DOI: 10.1002/adfm.200500158

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      Photoaddressable diblock copolymers, consisting of three-ring mesogenic groups in combination with azobenzene side groups, are promising materials for holographic data storage. A remarkable improvement in the stability of holographic gratings has been achieved. The Figure shows several holographic gratings inscribed under different angles.

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