Advanced Functional Materials

Cover image for Vol. 15 Issue 4

April, 2005

Volume 15, Issue 4

Pages 519–710

    1. Cover Picture: Fabrication of Stable Metallic Patterns Embedded in Poly(dimethylsiloxane) and Model Applications in Non-Planar Electronic and Lab-on-a-Chip Device Patterning (Adv. Funct. Mater. 4/2005)

      K. J. Lee, K. A. Fosser and R. G. Nuzzo

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200590013

      The fabrication of durable metallic patterns embedded in poly(dimethylsiloxane) (PDMS) is demonstrated using adhesion chemistries mediated by silane coupling agents. These metallization structures in PDMS are used as compliant contact photomasks for photolithographic processes (see Figure, right), for transistors (Figure, left) and are shown to be appropriate for electrochemical detection in polymer lab-on-a-chip devices.

    2. Contents: Adv. Funct. Mater. 4/2005 (pages 519–527)

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200590011

    3. Fabrication of Biofunctionalized Quasi-Three-Dimensional Microstructures of a Nonfouling Comb Polymer Using Soft Lithography (pages 529–540)

      H. Ma, J. Hyun, Z. Zhang, T. P. Beebe Jr. and A. Chilkoti

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400088

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      A simple set of methods for the fabrication of quasi-3D patterns that present topographical and biochemical cues to cells (see Figure) on a variety of substrates are presented. These methods are shown to successfully maintain cellular patterns for up to two months in serum-containing media.

    4. Write–Read–Erase Molecular-Switching System Trapped in a Polymer Hydrogel Matrix (pages 541–545)

      F. Galindo, J. C. Lima, S. V. Luis, A. J. Parola and F. Pina

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400274

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      An optical memory has come closer to realization with the encapsulation of 4′,7-dihydroxyflavylium in a water-permeable crosslinked polymer hydrogel matrix. The water permeability and transparency of the polymer allow the use of pH and light stimuli to attain differently colored states in the flavylium system which can act as a reusable photographic film (see Figure).

    5. Synthesis and Rate Performance of Monolithic Macroporous Carbon Electrodes for Lithium-Ion Secondary Batteries (pages 547–556)

      K. T. Lee, J. C. Lytle, N. S. Ergang, S. M. Oh and A. Stein

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400186

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      Inverse-opal carbon monoliths have been fabricated (see Figure) from colloidal-crystal templates infiltrated with resorcinol-formaldehyde precursor solutions. These nanoarchitectured carbon monoliths demonstrate relatively high electrochemical rate performance compared to similarly prepared, but non-templated, carbon electrodes.

    6. Fabrication of Stable Metallic Patterns Embedded in Poly(dimethylsiloxane) and Model Applications in Non-Planar Electronic and Lab-on-a-Chip Device Patterning (pages 557–566)

      K. J. Lee, K. A. Fosser and R. G. Nuzzo

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400189

      Thumbnail image of graphical abstract

      The fabrication of durable metallic patterns embedded in poly(dimethylsiloxane) (PDMS) is demonstrated using adhesion chemistries mediated by silane coupling agents. These metallization structures in PDMS are used as compliant contact photomasks for photolithographic processes (see Figure, right), for transistors (Figure, left) and are shown to be appropriate for electrochemical detection in polymer lab-on-a-chip devices.

    7. Rational Color Tuning and Luminescent Properties of Functionalized Boron-Containing 2-Pyridyl Pyrrolide Complexes (pages 567–574)

      H.-Y. Chen, Y. Chi, C.-S. Liu, J.-K. Yu, Y.-M. Cheng, K.-S. Chen, P.-T. Chou, S.-M. Peng, G.-H. Lee, A. J. Carty, S.-J. Yeh and C.-T. Chen

      Article first published online: 20 DEC 2004 | DOI: 10.1002/adfm.200400250

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      Three highly emissive BPh2 complexes with 2-pyridyl-, 2-quinolinyl-, and 2-quinoxalinyl-pyrrolide chelates have been synthesized. They exhibit distinctive variations of emission color spanning from greenish blue to red orange (see Figure). A rational explanation for these color changes is provided by time-dependent density functional theory calculations.

    8. Preparation of Self-Organized Mesoscale Polymer Patterns on a Solid Substrate: Continuous Pattern Formation from a Receding Meniscus (pages 575–581)

      H. Yabu and M. Shimomura

      Article first published online: 20 DEC 2004 | DOI: 10.1002/adfm.200400315

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      A thin liquid film of polymer solution with a receding meniscus is continuously supplied from a narrow gap between two plates, one sliding over the other. Three types of patterned polymer films are formed (the Figure shows parallel stripes) on the lower substrate from the evaporating solution edge.

    9. Three-Dimensional Porous Copper–Tin Alloy Electrodes for Rechargeable Lithium Batteries (pages 582–586)

      H.-C. Shin and M. Liu

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200305165

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      Cu6Sn5 negative electrodes with a unique 3D foam structure are fabricated using an electrochemical deposition process. The highly porous walls of the foam structure consist of numerous small grains. At an extremely high cycling rate of 20 C, the obtainable capacity was about 50 % of that at 1 C rate (see Figure).

    10. GaAs Oxide Desorption under Extreme Ultraviolet Photon Flux (pages 587–592)

      D. Ercolani, M. Lazzarino, G. Mori, B. Ressel, L. Sorba, A. Locatelli, S. Cherifi, A. Ballestrazzi and S. Heun

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400033

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      An unexpectedly strong desorption effect due to the irradiation by extreme UV (EUV) light of gallium arsenide oxide structures fabricated by local anodization with atomic force microscopy is reported (see Figure). The chemistry of the oxide structures is determined by laterally resolved photoelectron spectroscopy. The possible impact on the development of EUV lithography is discussed.

    11. A Silicon–Silica Nanocomposite Material (pages 593–602)

      Y. Cohen, K. Landskron, N. Tétreault, S. Fournier-Bidoz, B. Hatton and G. A. Ozin

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400069

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      A novel self-assembly method allows the encapsulation of luminescent silicon nanoclusters within the channels of an oriented periodic mesoporous silica thin film (see Figure). The high loading (up to 39% of the accessible pore space) and improved chemical stability to oxidation at ambient conditions is important for using the materials for silicon-based optoelectronics.

    12. Highly Luminescent CdSe/ZnS Nanocrystals Synthesized Using a Single-Molecular ZnS Source in a Microfluidic Reactor (pages 603–608)

      H. Wang, H. Nakamura, M. Uehara, Y. Yamaguchi, M. Miyazaki and H. Maeda

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400164

      Large-scale preparation of CdSe/ZnS core/shell nanoparticles is brought closer by the use of a microreactor. The fine control of reaction conditions allows the use of a single-molecular source for ZnS, [(C2H5)2NCSS]2Zn, which is air-stable and of low toxicity. The ZnS-capped CdSe particles prepared this way have a narrow size distribution, which is dependent on the stabilizer used for the uncapped CdSe particles, and are highly luminescent. The high photoluminescence (quantum yield ≥ 50 %) is maintained when the particle surface is made hydrophilic and suitable for biological applications.

    13. The Effect of Polymer Optoelectronic Properties on the Performance of Multilayer Hybrid Polymer/TiO2 Solar Cells (pages 609–618)

      P. Ravirajan, S. A. Haque, J. R. Durrant, D. D. C. Bradley and J. Nelson

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400165

      The effects of the exciton-transport, charge-transport, and light-harvesting properties of conjugated polymers on the performance of a polymer/TiO2 hybrid system is studied systematically. Devices made from three different poly(2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylenevinylene)-based polymers and a fluorene–bithiophene copolymer are compared; it is found that the short-circuit current density is limited by the photogeneration rate and the quality of the interfaces, rather than by the hole-transport properties of the polymer. For optimizing performance, dip-coating is found to lead to excellent polymer infiltration into the porous metal oxide, and the inclusion of a poly(ethylene dioxythiophene):poly(styrene sulfonic acid) layer beneath the top metal contact improves the short-circuit photocurrent. Devices optimized in such a way show a short-circuit current density of 1 mA cm–2, a fill factor of 0.50, an open-circuit voltage of 0.86 V, and an overall power conversion efficiency of ≥ 0.4 % under 1 sun.

    14. An Organic Thin-Film Transistor with a Photoinitiator-Free Photosensitive Polyimide as Gate Insulator (pages 619–626)

      S. H. Pyo, M. Y. Lee, J. J. Jeon, J. H. Lee, M. H. Yi and J. S. Kim

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400206

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      An organic thin-film transistor (OTFT) has been produced with a photoinitiator-free photosensitive polyimide thin film as the gate insulator. The resolution of pattern on the film is about 50 μm (see Figure). The field-effect mobility of pentacene OTFTs made using the photopatterned polyimide is 0.48 cm2 V–1 s–1.

    15. Exact Scaling Laws for Electrical Conductivity Properties of Nematic Polymer Nanocomposite Monodomains (pages 627–638)

      X. Zheng, M. G. Forest, R. Lipton, R. Zhou and Q. Wang

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400200

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      Two aspects of nematic polymer nanocomposites are connected to derive the effective electrical conductivity tensor: the orientational distribution of anisotropic macromolecules and homogenization theory of composites with spheroidal inclusions at low volume fractions. The Figure shows principal conductivity enhancement versus volume fraction of rods; quiescent phases (solid red) inherit hysteresis of the isotropic-nematic transition, while sheared phases (dotted blue) that show gains due to flow are most significant near the order transition.

    16. Gold-Cluster Sensors Formed Electrochemically at Boron-Doped-Diamond Electrodes: Detection of Dopamine in the Presence of Ascorbic Acid and Thiols (pages 639–647)

      J. Weng, J. Xue, J. Wang, J. Ye, H. Cui, F. Sheu and Q. Zhang

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400049

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      Au clusters are electrochemically deposited on boron-doped-diamond (BDD) electrodes to produce dopamine (DA) sensors. A layer of mercaptoacetic acid on the Au clusters (see Figure) increases sensitivity and selectivity to DA in the presence of ascorbate (AA), and provides an antifouling effect. After pre-absorption, 1.0 nM DA could be detected in the presence of 10–4 M AA.

    17. Short-Time Tuning of the Biological Activity of Functionalized Polyelectrolyte Multilayers (pages 648–654)

      N. Benkirane-Jessel, P. Lavalle, E. Hübsch, V. Holl, B. Senger, Y. Haïkel, J.-C. Voegel, J. Ogier and P. Schaaf

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400129

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      Layer-by-layer assembly is used to prepare films of degradable and non-degradable polyelectrolytes. By incorporating protein molecules at well-defined depths in the film and tuning the enantiomeric ratios within each polyelectrolyte layer, cells placed on the film surface react with the protein to a predefined schedule (see Figure).

    18. Phase-Separation-Induced Micropatterned Polymer Surfaces and Their Applications (pages 655–663)

      Y. Wang, Z. Liu, B. Han, Z. Sun, J. Zhang and D. Sun

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400201

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      Micropatterned polymer films with concavities on their surfaces (see Figure, upper left) are fabricated by spreading polymer solutions on a non-solvent surface. The hydrophobicity of these surfaces is enhanced in a controllable way and they can be used as templates to prepare convex-patterned polymer films (Figure, upper right), TiO2 microparticles (lower left), and NaCl nanocrystals (lower right).

    19. V-Shaped Thiophene-Based Oligomers with Improved Electroluminescence Properties (pages 664–670)

      G. Barbarella, L. Favaretto, A. Zanelli, G. Gigli, M. Mazzeo, M. Anni and A. Bongini

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400172

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      The synthesis via the Stille coupling of new branched oligothiophenes (e.g., see the calculated geometry and electron density of the highest occupied molecular orbital model in Figure) with excellent film-forming properties is reported. Light-emitting diodes with spin-coated films as the active layers display markedly improved performance with respect to similar devices based on linear oligothiophenes.

    20. Effect of Mesoscale Crystalline Structure on the Field-Effect Mobility of Regioregular Poly(3-hexyl thiophene) in Thin-Film Transistors (pages 671–676)

      H. Yang, T. J. Shin, L. Yang, K. Cho, C. Y. Ryu and Z. Bao

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400297

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      The connectivity of regioregular poly(3-hexylthiophene) nanofibrils are significantly affected by the solvent used for processing and leads to different thin-film transistor performance. Well-interconnected branched nanofibrils formed in CHCl3 (e.g., Figure, bottom) display greater field-effect mobility than the short rods formed in CH2Cl2 (e.g., Figure, top).

    21. Infiltration of Regioregular Poly[2,2′-(3-hexylthiopene)] into Random Nanocrystalline TiO2 Networks (pages 677–682)

      G. P. Bartholomew and A. J. Heeger

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400277

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      The infiltration of regioregular poly[2,2′-(3-hexylthiopene)] into random nanocrystalline TiO2 networks is explored with secondary-ion mass spectrometry. Initial inclusion of the polymer into a bare network is 0.5 %. A combination of several incorporation strategies (e.g., surface derivatization and post-coating heat treatments) increases the inclusion (see Figure) to as high as 22 %.

    22. Crystallization of Vaterite Nanowires by the Cooperative Interaction of Tailor-Made Nucleation Surfaces and Polyelectrolytes (pages 683–688)

      M. Balz, H. A. Therese, J. Li, J. S. Gutmann, M. Kappl, L. Nasdala, W. Hofmeister, H.-J. Butt and W. Tremel

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400333

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      The concept of template-induced crystallization on self-assembled monolayers is combined with the use of polymer additives to form a new strategy. Through the cooperative interaction of a matrix involved in the nucleation process, a dissolved polyelectrolyte, and dissolved ions, hierarchically ordered mineral structures are formed (see Figure). The presence of the polyelectrolyte has a critical effect on the morphology of the product.

    23. Influence of the Relative Humidity on the Performance of Polymer/TiO2 Photovoltaic Cells (pages 689–694)

      L. H. Slooff, J. M. Kroon, J. Loos, M. M. Koetse and J. Sweelssen

      Article first published online: 20 DEC 2004 | DOI: 10.1002/adfm.200400311

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      Titanium(IV) isopropoxide (TTIP) is used as a TiO2 precursor material for the manufacturing of flat-layer and bulk-heterojunction TiO2:MDMO-PPV photovoltaic cells. It is shown that the relative humidity (RH) during spin-coating of the TTIP has a pronounced effect on layer morphology and device performance. The Figure shows the maximum power as a function of RH for a flat-layer device.

    24. A Novel Route to Thermosensitive Polymeric Core–Shell Aggregates and Hollow Spheres in Aqueous Media (pages 695–699)

      Y. Zhang, M. Jiang, J. Zhao, X. Ren, D. Chen and G. Zhang

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400378

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      Poly(ε-caprolactone)/poly(N-isopropylacrylamide), (PCL/PNIPAM) core–shell particles are obtained by localizing polymerization of NIPAM and crosslinker around the surface of PCL nanoparticles. Hollow PNIPAM spheres, which display a reversible swelling and de-swelling at ∼ 32 °C, are obtained by core degradation of the resultant particles.

    25. Selective Ion Transport and Complexation in Layer-by-Layer Assemblies of p-Sulfonato- calix[n]arenes and Cationic Polyelectrolytes (pages 700–708)

      A. Toutianoush, J. Schnepf, A. El Hashani and B. Tieke

      Article first published online: 23 MAR 2005 | DOI: 10.1002/adfm.200400223

      Self-assembled films of p-sulfonato-calix[n]arenes with n = 4, 6, and 8 and poly(vinylamine) are prepared via alternating electrostatic layer-by-layer adsorption. First measurements of ion permeation indicate a highly selective transport with separation factor α(NaCl/LaCl3) as large as 143 or α(NaCl/MgCl2) as large as 72, for example. The selectivity originates from complex formation of distinct metal ions with the calix[n]arene units and from Donnan rejection of the permeating di- and trivalent ions from equally charged parts of the membrane.

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