Advanced Functional Materials

Cover image for Vol. 15 Issue 2

February, 2005

Volume 15, Issue 2

Pages 179–342

    1. Cover Picture: Enhanced Electro-Optic Behavior for Shaped Polymer Cholesteric Liquid-Crystal Flakes Made Using Soft Lithography (Adv. Funct. Mater. 2/2005)

      A. Trajkovska-Petkoska, R. Varshneya, T. Z. Kosc, K. L. Marshall and S. D. Jacobs

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200590006

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      Soft lithography is used to make a variety of shaped flakes from polymer cholesteric liquid-crystal material (see Figure). In a fluid-filled electro- optic cell, the micrometer-sized flakes exhibit brilliant circularly polarized selective reflection colors without polarizers or color filters. With the application of a low-magnitude AC field, flakes reorient in hundreds of milliseconds and colors disappear.

    2. Contents: Adv. Funct. Mater. 2/2005 (pages 179–187)

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200590004

    3. Biomimetic Pattern Transfer (pages 189–195)

      L.-Q. Wu, R. Ghodssi, Y. A. Elabd and G. F. Payne

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400279

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      Patterns from a microfabricated silicon wafer are transferred to films of the aminopolysaccharide chitosan (as shown in the Figure) through an electrochemically initiated phenol reaction cascade. Pattern transfer can be controlled spatially and temporally, while the reactions modify the film's character, structure, and fluorescence.

    4. TiO2-Based Composite Nanotube Arrays Prepared via Layer-by-Layer Assembly (pages 196–202)

      Y.-G. Guo, J.-S. Hu, H.-P. Liang, L.-J. Wan and C.-L. Bai

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200305098

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      TiO2 and TiO2-based composite nanotube arrays have been prepared via the layer-by-layer assembly of polyelectrolytes, organic precursors, and nanoparticles on porous anodic alumina membranes. The nanotubes (see Figure) contain a large number of TiO2 nanocrystals, and other semiconductor quantum dots (CdS) or metallic nanoparticles (Au), and represent a new type of composite nanostructure.

    5. High-Conductivity Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonate) Film and Its Application in Polymer Optoelectronic Devices (pages 203–208)

      J. Ouyang, C.-W. Chu, F.-C. Chen, Q. Xu and Y. Yang

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400016

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      The conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films is enhanced by the addition of ethylene glycol, meso-erythritol, or 2-nitroethanol, which change the conformation of the PEDOT chains. High-performance polymer light-emitting diodes (see Figure) and solar cells using enhanced PEDOT:PSS films as the anode are demonstrated.

    6. Acrylate-Based Photopolymer for Two-Photon Microfabrication and Photonic Applications (pages 209–216)

      L. H. Nguyen, M. Straub and M. Gu

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400212

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      Two-photon-induced photopolymerization of a newly formulated acrylate resin LN1 demonstrates applicability to microstereolithography, surpassing current material limitations. Complex photonic-crystal woodpile structures are prepared (see Figure) which exhibit pronounced photonic stop gap effects in the near-infrared and telecommunication-wavelength regions.

    7. Enhanced Electro-Optic Behavior for Shaped Polymer Cholesteric Liquid-Crystal Flakes Made Using Soft Lithography (pages 217–222)

      A. Trajkovska-Petkoska, R. Varshneya, T. Z. Kosc, K. L. Marshall and S. D. Jacobs

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400286

      Thumbnail image of graphical abstract

      Soft lithography is used to make a variety of shaped flakes from polymer cholesteric liquid-crystal material (see Figure). In a fluid-filled electro- optic cell, the micrometer-sized flakes exhibit brilliant circularly polarized selective reflection colors without polarizers or color filters. With the application of a low-magnitude AC field, flakes reorient in hundreds of milliseconds and colors disappear.

    8. In Search of High-Performance Platinum(II) Phosphorescent Materials for the Fabrication of Red Electroluminescent Devices (pages 223–229)

      J. Kavitha, S.-Y. Chang, Y. Chi, J.-K. Yu, Y.-H. Hu, P.-T. Chou, S.-M. Peng, G.-H. Lee, Y.-T. Tao, C.-H. Chien and A. J. Carty

      Article first published online: 20 DEC 2004 | DOI: 10.1002/adfm.200400131

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      Transition-metal-based phosphorescent materials are of interest for organic light-emitting diodes (LEDs). The rational design and syntheses of Pt(iqdz)2 (1, see Figure) and Pt(pydz)2 (2), bearing isoquinolinyl and pyridyl indazole groups, respectively, are reported. Reasons for their unusually bright luminescence in both the solution and solid states are suggested and a red LED with 1 as a dopant emitter is fabricated.

    9. Red-Emitting Fluorenes as Efficient Emitting Hosts for Non-Doped, Organic Red-Light-Emitting Diodes (pages 231–238)

      C.-L. Chiang, M.-F. Wu, D.-C. Dai, Y.-S. Wen, J.-K. Wang and C.-T. Chen

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400102

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      Brilliant red-light-emitting fluorenes, diphenylamino- and dicyanovinyl- substituted spirobifluorenes are reported. These compounds perform far better than Nile Red and DCM in the solid state (see Figure); non-doped light-emitting diodes with a red-emitting fluorene as host-emitter show external quantum efficiencies as high as 3.6 % and electroluminescence of over 12 000 cd m–2.

    10. Titania and Mixed Titania/Aluminum, Gallium, or Indium Oxide Spheres: Sol–Gel/Template Synthesis and Photocatalytic Properties (pages 239–245)

      A. S. Deshpande, D. G. Shchukin, E. Ustinovich, M. Antonietti and R. A. Caruso

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400220

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      Porous spheres of mixed oxides (Ti/Al, Ti/Ga, or Ti/In) have been synthesized using porous polymer beads as templates (see Figure). The mixed oxides at 5 wt.-% of the second oxide were more active than Degussa P25 titania at pH 6 for the photodecomposition of 2-chlorophenol.

    11. Novel Conjugated Organic Dyes for Efficient Dye-Sensitized Solar Cells (pages 246–252)

      K. Hara, T. Sato, R. Katoh, A. Furube, T. Yoshihara, M. Murai, M. Kurashige, S. Ito, A. Shinpo, S. Suga and H. Arakawa

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400272

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      Dye-sensitized nanocrystalline TiO2 solar cells based on novel conjugated organic-dye photosensitizers produce solar-energy-to-electricity conversion efficiencies of up to 6.8 % under AM 1.5 irradiation (100 mW cm–2). The Figure shows the electron distribution of the lowest unoccupied molecular orbitals of a typical dye.

    12. Direct Synthesis of Highly Stable Mesoporous Molecular Sieves Containing Zeolite Building Units (pages 253–258)

      A. Sakthivel, S.-J. Huang, W.-H. Chen, Z.-H. Lan, K.-H. Chen, H.-P. Lin, C.-Y. Mou and S.-B. Liu

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400038

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      A highly stable mesoporous aluminosilicate material (MMS-H) with a structure analogous to an MCM-48 molecular sieve but containing zeolite secondary building units has been prepared via a one-step synthesis method without the assistance of sodium hydroxide. The Figure shows a spectrum by hyperpolarized 129Xe NMR, illustrating the unique porous nature of the MMS-H sample.

    13. Single-Source Precursors For Synthesizing Bifunctional Periodic Mesoporous Organosilicas (pages 259–266)

      W. J. Hunks and G. A. Ozin

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400294

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      Bifunctional periodic mesoporous organosilicas comprised of disilsesquioxane (T2), siloxane-disilsesquioxane (DT2), or siloxy-trisilsesquioxane (MT3) structural units, with corresponding R/Si ratios of 1, 1.3, and 1.5, have been prepared. The PMOs are synthesized by the co-assembly of organosilica precursors and the triblock copolymer Pluronic P123 to generate nanoporous organosilicates with large pore diameters (6–7 nm) and surface areas (700–800 m3 g–1) (see Figure).

    14. Phospholipid-Based Catalytic Nanocapsules (pages 267–272)

      G. E. Lawson, Y. Lee, F. M. Raushel and A. Singh

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400153

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      The encapsulation and catalytic efficiency of organophosphate hydrolyzing enzymes in polymer- stabilized nanocapsules are reported. The capsules are formed from crosslinked vesicles derived from a headgroup-polymerizable phospholipid and act to protect the enzyme, while allowing the enzyme to retain its activity.

    15. Synthesis and Assembly of Gold Nanoparticles in Quasi-Linear Lysine–Keggin-Ion Colloidal Particles (pages 273–280)

      A. Sanyal, S. Mandal and M. Sastry

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400107

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      Phosphotungstate Keggin ions complex with lysine amino acid to produce fiber-like colloidal particles (upper Figure). In the presence of Au3+ ions, the Keggin ions in the fibers can then act as UV-switchable reducing agents, producing gold nanoparticles at the surface of the colloids, as shown in the lower part of the Figure.

    16. Electrophosphorescent Devices Based on Cationic Complexes: Control of Switch-on Voltage and Efficiency Through Modification of Charge Injection and Charge Transport (pages 281–289)

      E. A. Plummer, A. van Dijken, J. W. Hofstraat, L. De Cola and K. Brunner

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400218

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      Devices based on charged and neutral iridium complexes doped into poly(vinylcarbazole) are presented (see Figure). The role of the ions and the charge-transport properties of the complexes are discussed. The charged complexes fulfil a double function as emitter and charge transporter.

    17. Investigation of the Effects of Doping and Post-Deposition Treatments on the Conductivity, Morphology, and Work Function of Poly(3,4-ethylenedioxythiophene)/Poly(styrene sulfonate) Films (pages 290–296)

      J. Huang, P. F. Miller, J. S. Wilson, A. J. de Mello, J. C. de Mello and D. D. C. Bradley

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400073

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      The influence of annealing conditions on the physical properties of thin films of PEDOT/PSS is investigated. In particular, how the ambient gas (see Figure) and choice of dopant affect the conductivity, morphology, and work function of the films is explored.

    18. Formation of Highly Crystallized β-PbO Thin Films by Cathodic Electrodeposition of Pb and Its Rapid Oxidation in Air (pages 297–301)

      S. Sawatani, S. Ogawa, T. Yoshida and H. Minoura

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400086

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      Electrodeposition of β-PbO thin films from aqueous solutions of PbII salts (Pb(NO3)2, Pb(ClO4)2, and Pb(CH3COO)2) has been investigated. Evidence is presented that the previously assumed reaction pathway is not active. Instead, the authors demonstrate that the films are initially metallic Pb, which is then quickly oxidized to highly crystallized β-PbO (see Figure) with highly ordered internal nanostructure.

    19. Halide-Transport Chemical Vapor Deposition of Luminescent ZnS:Mn2+ One-Dimensional Nanostructures (pages 303–308)

      J.-P. Ge, J. Wang, H.-X. Zhang, X. Wang, Q. Peng and Y.-D. Li

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400078

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      ZnS:M2+ (M = Mn, Co, Cu) one-dimensional (1D) nanostructures (see Figure) are prepared via a simple halide-transport chemical vapor deposition process at a relatively low temperature. By selecting suitable amounts of doping source (MCl2) and controlling proper synthetic parameters, 1D nanostructures with tunable photoluminescence emission can be prepared.

    20. Novel Europium-Complex/Nitrile- Butadiene Rubber Composites (pages 309–314)

      L. Liu, Y.-L. Lu, L. He, W. Zhang, C. Yang, Y.-D. Liu, L.-Q. Zhang and R.-G. Jin

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400141

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      The fluorescent emission intensity at 612 nm of cured Eu-AAPhen/nitrile-butadiene rubber finely dispersed composites prepared via an in-situ reaction method is much stronger than that of their uncured counterparts. However, the dependence of emission on Eu3+ content departs from linearity at a considerably lower filling level (see Figure).

    21. Nanoporous Ultra-Low-Dielectric-Constant Fluoropolymer Films via Selective UV Decomposition of Poly(pentafluorostyrene)-block-Poly(methyl methacrylate) Copolymers Prepared Using Atom Transfer Radical Polymerization (pages 315–322)

      G.-D. Fu, Z. Yuan, E.-T. Kang, K.-G. Neoh, D. M. Lai and A. C. H. Huan

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400138

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      Nanoporous fluoropolymer films with dielectric constants < 2.0 are prepared via selective UV decomposition of poly(pentafluorostyrene)-block- poly(methyl methacrylate) (PFS-b-PMMA). The block copolymers are first synthesized using atom transfer radical polymerization and almost all the PMMA is found to be removed on exposure to UV light.

    22. Doping-Induced Charge Trapping in Organic Light-Emitting Devices (pages 323–330)

      F. Nüesch, D. Berner, E. Tutiš, M. Schaer, C. Ma, X. Wang, B. Zhang and L. Zuppiroli

      Article first published online: 20 DEC 2004 | DOI: 10.1002/adfm.200305022

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      The effect of charge trapping induced by pyran-containing donor–acceptor dyes is investigated in standard light-emitting devices. Experimental results and numerical device simulations reveal that doping with DCM-TPA gives rise to a split recombination zone (see Figure) that is responsible for light emission from both the doped and undoped layer.

    23. Growth of Bulk ZnO Single Crystals via a Novel Hydrothermal Oxidative Pressure-Relief Route (pages 331–335)

      W. Zheng, F. Guo and Y. Qian

      Article first published online: 20 DEC 2004 | DOI: 10.1002/adfm.200400080

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      A novel hydrothermal oxidative pressure-relief process is used to prepare bulk hexagonal pyramidal ZnO single crystals. Metallic Zn and H2O2 are used as the raw materials in alkali solvent, producing crystals such as that shown in the Figure, which is 0.65 mm long and has a diameter of 0.16 mm.

    24. Hydrophilic and Antimicrobial Zeolite Coatings for Gravity-Independent Water Separation (pages 336–340)

      A. M. P. McDonnell, D. Beving, A. Wang, W. Chen and Y. Yan

      Article first published online: 14 FEB 2005 | DOI: 10.1002/adfm.200400183

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      Zeolite thin films (see Figure) have been synthesized for application as a coating on the surfaces of condensers on board manned spacecraft. This paper demonstrates that zeolite is very capable of providing the biocidal and hydrophilic functionality required for gravity-independent water separation from cabin air.

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