Advanced Materials

Cover image for Vol. 15 Issue 3

February, 2003

Volume 15, Issue 3

Pages 173–260

    1. Contents: Adv. Mater. 3/2003 (pages 173–176)

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390041

    2. Contents: Adv. Funct. Mater. 2/2003 (pages 179–181)

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390042

    3. Pores in III–V Semiconductors (pages 183–198)

      H. Föll, S. Langa, J. Carstensen, M. Christophersen and I.M. Tiginyanu

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390043

      Electrochemically etched pores in III–V semiconductors are dynamic systems which exhibit a remarkable degree of self-organized pattern formation and give rise to a wealth of new properties, in particular large nonlinear optical effects. This Review article emphasizes their nucleation, formation mechanisms, pore morphologies and self-organization. The Figure, a collage of individual SEM micrographs, shows a 3D-periodical self-arranged InP single-pore crystal.

    4. Template Synthesis and Optical Properties of Chameleonic Poly(N-isopropylacrylamide) Gels Using Closest-Packed Self-Assembled Colloidal Silica Crystals (pages 199–201)

      Y. Takeoka and M. Watanabe

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390044

      Smart macroporous hydrogels with a range of optical behavior have been prepared using colloidal crystals as templates. The structural color imprinted in the gel (see Figure and cover) varies with a change in the volume of the gel. It is now possible to build a soft material that displays the various structural colors available to living things.

    5. Anisotropic Bending and Unbending Behavior of Azobenzene Liquid-Crystalline Gels by Light Exposure (pages 201–205)

      T. Ikeda, M. Nakano, Y. Yu, O. Tsutsumi and A. Kanazawa

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390045

      Freestanding azobenzene-containing liquid-crystalline gel films that undergo a significant and anisotropic bending toward the irradiation direction when exposed to UV light have been prepared. When the bent films are exposed to visible light they unbend immediately, and the initial flat films are restored (see Figure and Inside front cover).

    6. Lithium Niobate Inverse Opals Prepared by Templating Colloidal Crystals of Polyelectrolyte-Coated Spheres (pages 205–210)

      D. Wang and F. Caruso

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390046

      Colloidal crystals of polyelectrolyte multilayer (PEM)-coated polystyrene spheres are used as templates for the preparation of lithium niobate inverse opal films (see Figure). The PEM coating facilitated the formation of the inverse opals and by controlling the layer thickness via layer-by-layer assembly, inverse opals with tailored structural properties (pore size, wall thickness, and channel diameter) are prepared.

    7. Porous Polymer and Cell Composites That Self-Assemble In Situ (pages 210–213)

      A.K. Salem, F.R.A.J. Rose, R.O.C. Oreffo, X. Yang, M.C. Davies, J.R. Mitchell, C.J. Roberts, S. Stolnik-Trenkic, S.J.B. Tendler, P.M. Williams and K.M. Shakesheff

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390047

      A cell-laden 3D network is formed upon the addition of avidin to biotinylated polymer particles in the presence of a suspension of cells (see Figure). Applications in tissue engineering and drug delivery are demonstrated; a shape-retaining biomaterial is formed within minutes of injecting the components into a cavity. The molecular interaction mechanism of self-assembly differentiates this polymer/cell composite from other injectable systems.

    8. Improved Crystal-Growth and Emission Gain-Narrowing of Thiophene/Phenylene Co-Oligomers (pages 213–217)

      M. Ichikawa, R. Hibino, M. Inoue, T. Haritani, S. Hotta, T. Koyama and Y. Taniguchi

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390048

      Large plate-like single crystals of several millimeters to ∼ 1 cm in size of organic semiconducting materials are prepared via an improved crystal-growth technique. The crystals (see Figure) exhibit self-waveguided amplified spontaneous emission with a relatively small threshold resulting from the excellent optical properties of the crystals, such as high transparency and low light scattering.

    9. Titania/Polypyrrole Hybrid Nanocomposites Built from In-Situ Generated Organically Functionalized Nanoanatase Building Blocks (pages 217–221)

      S. Roux, G.J. de A.A. Soler-Illia, S. Demoustier-Champagne, P. Audebert and C. Sanchez

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390049

      A bifunctional capping ligand is used to obtain pyrrol-functionalized monodispersed nanocrystalline TiO2 (anatase) particles in a single step. The pyrrole functionalities in the shell are then (electro)chemically polymerized to create a polypyrrole (PPy)/TiO2 hybrid nanocomposite film (see Figure). Further electronic modification of the conducting polymer is possible, leading to a great variety of potential applications.

    10. Directed Deposition of Nanoparticles Using Diblock Copolymer Templates (pages 221–224)

      M.J. Misner, H. Skaff, T. Emrick and T.P. Russell

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390050

      Nanoporous film generation from diblock copolymers has been used to direct the assembly of ligand-stabilized CdSe nanoparticles (see Figure). The number of particles forced into each pore is dependent on the concentration of the nanoparticles in solution. Further, the photoluminescence of the particles is maintained in the assembly process.

    11. New Iridium Complexes as Highly Efficient Orange–Red Emitters in Organic Light-Emitting Diodes (pages 224–228)

      J.P. Duan, P.P. Sun and C.H. Cheng

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390051

      Two new iridium complexes with pyrazine derivatives as ligands (see Figure) were synthesized. The electroluminescent devices based on these metal complexes emit orange–red light at ∼ 610 nm with exceedingly high brightness and external quantum, current, and power efficiencies.

    12. Nanobelts, Nanocombs, and Nanowindmills of Wurtzite ZnS (pages 228–231)

      C. Ma, D. Moore, J. Li and Z.L. Wang

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390052

      Nanostructures of wurtzite-structured zinc sulfide, which is unlikely to be stable at room temperature under conventional conditions, have been synthesized by a simple physical process. Morphologies with belt- (see Figure), saw-, comb-, and windmill-like nanostructures have been observed and characterized using a variety of imaging techniques.

    13. GaN Nanorods Doped by Hydride Vapor-Phase Epitaxy: Optical and Electrical Properties (pages 232–235)

      H.-M. Kim, Y.-H. Cho and T.W. Kang

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390053

      Exciting opportunities in nanoscale technology could be made available thanks to this first report of doping GaN nanorods to create p- and n-type materials. Controlled doping of the nanorods is achieved by hydride vapor-phase epitaxy, and they are characterized optically and electrically. The Figure shows a scanning electron microscopy image of a nanorod field-effect transistor (scale bar is 10 μm)

    14. Synthesis of Cable-Like Copper Nanowires (pages 235–237)

      M.-Y. Yen, C.-W. Chiu, C.-H. Hsia, F.-R. Chen, J.-J. Kai, C.-Y. Lee and H.-T. Chiu

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390054

      Cable-like copper nanowires (1–10 μm in length and 15–80 nm in diameter) with an insulating poly(dimethylsiloxane) (PDMS) sheath (5–10 nm in thickness, see Figure) have been successfully synthesized by a solvent-free reaction between CuCl and (Me3Si)4Si in the presence of PDMS in sealed tubes. The wire formation mechanism is proposed to be vapor–solid reaction growth.

    15. Metallic Sub-Nanometer MoS2–xIy Nanotubes (pages 237–240)

      M. Remskar, A. Mrzel, R. Sanjines, H. Cohen and F. Lévy

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390055

      MoS2–x nanotubes of sub-nanometer diameter show metallic behavior when studied using scanning tunnelling microscopy. Single nanotubes and those self-assembled into narrow MoS2–xIy bundles can be manipulated by voltage pulses to form nanotube associations. Spontaneous alignment, manipulation using an electrical field gradient, and easy cutting to size the tubes enables their use in advanced nano-device technology.

    16. Electrically Switchable, One-Dimensional Polymeric Resonators from Holographic Photopolymerization: A New Approach for Active Photonic Bandgap Materials (pages 241–244)

      R. Jakubiak, T.J. Bunning, R.A. Vaia, L.V. Natarajan and V.P. Tondiglia

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390056

      Stimulated emission is demonstrated by optically pumping chromophores within the liquid-crystal domains of 1D bandgap structures that are derived from holographic polymer-dispersed liquid-crystal (H-PDLC) gratings (see Figure). Electrically switchable laser resonance is also possible using the H-PDLC, since applying an electric field across the grating aligns the directors of the liquid crystal, diminishing the refractive index profile and, consequently, the lasing action.

    17. A Simple Method for the Attachment of Polymer Films on Solid Substrates (pages 244–248)

      M. Yan and B. Harnish

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390057

      The immobilization of polymer thin films on solid substrates has been achieved using a very simple method, involving spin coating the polymer, followed by UV irradiation. A robust film remains on the substrate surface after solvent extraction. The procedure could be employed to fabricate patterned polymer thin films via photolithography (see Figure).

    18. Dynamic Addressing of a Surface Pattern by a Stimuli-Responsive Fusion Protein (pages 248–251)

      W. Frey, D.E. Meyer and A. Chilkoti

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390058

      Thermodynamically reversible addressing of proteins (TRAP) is demonstrated. A stimuli-responsive elastin-like polypeptide fused to thioredoxin is used to reversibly address the fusion protein onto a chemically micropatterned surface template by switching the interaction between the surface and the stimuli- responsive polypeptide (see Figure).

    19. Enhanced Electrical Conductivity of Self-Assembled, Layered Molecular Composites of Metallo-Backbone Polymer and Polyaniline (pages 251–254)

      S.-H. Lee, Z. Yuan and C.-W. Lee

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390059

      Polymers with metallo backbones and pendant alkoxy groups (see Figure) are intercalated into a conducting polymer system of polyaniline–camphor sulfonic acid (PANI–CSA). The use of properly designed self-assembled, layered metallic backbones, which are compatible with anions and Lewis bases of the doped PANI, is shown to improve not only the electrical conductivity but also the solubility of PANI–CSA.

    20. Covalent and Non-covalent Attachment and Patterning of Polypyrrole at Silicon Surfaces (pages 254–257)

      A.R. Pike, S.N. Patole, N.C. Murray, T. Ilyas, B.A. Connolly, B.R. Horrocks and A. Houlton

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390060

      DNA and alkenyl pyrrole functionalized silicon surfaces allow for the formation of silicon/polypyrrole junctions. These junctions are spatially controlled by photolithography (see Figure) and selective photo-assisted electro-oxidation of pyrrole. This process shows promise for use in the development of molecular-based electronic devices, and could enable the deposition of polypyrrole analogously to metal ions in the formation of metallic wires.

    21. Electrophosphorescence from a Conjugated Copolymer Doped with an Iridium Complex: High Brightness and Improved Operational Stability (page 258)

      X. Gong, J.C. Ostrowski, G.C. Bazan, D. Moses, A.J. Heeger, M.S. Liu and A.K.-Y. Jen

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390063

    22. Author Index and Subject Index Adv. Mater. 3/2003 (page 260)

      Article first published online: 13 FEB 2003 | DOI: 10.1002/adma.200390062