Advanced Materials

Cover image for Vol. 15 Issue 2

January, 2003

Volume 15, Issue 2

Pages 89–168

    1. Contents: Adv. Mater. 2/2003 (pages 89–92)

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390038

    2. Preparation and Properties of Resorcinol–Formaldehyde Organic and Carbon Gels (pages 101–114)

      S.A. Al-Muhtaseb and J.A. Ritter

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390020

      The preparation and properties of resoncinol–formaldelhyde organic and carbon gels (see Figure) are reviewed, revealing the resulting nanostructure to be very sensitive to synthesis and processing conditions. This step-by-step comparison leads to interesting guidelines for tailoring these sol–gel materials for specific applications that require uniquely tuned structural and performance characteristsics.

    3. Materials Forum: Adv. Mater. 2/2003 (page 97)

      Version of Record online: 5 FEB 2003 | DOI: 10.1002/adma.200390040

    4. Electron-Beam-Induced Crosslinking of Electroluminescent Polymers for the Production of Multi-Color Patterned Devices (pages 115–117)

      R.A.M. Hikmet and R. Thomassen

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390021

      Electron-beam irradiation is used to crosslink an electroluminescent poly(phenylene vinylene). Increased irradiation leads to increased crosslinking and decreased hole mobility within the polymer, while the electroluminescence quantum efficiency remains constant. An electroluminescent device emitting various colours (see Figure) has been prepared by patterning the polymer through a shadow mask.

    5. Photoinduced Electron Transfer and Photovoltaic Response of a MDMO-PPV:TiO2 Bulk-Heterojunction (pages 118–121)

      P.A. van Hal, M.M. Wienk, J.M. Kroon, W.J.H. Verhees, L.H. Slooff, W.J.H. van Gennip, P. Jonkheijm and R.A.J. Janssen

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390022

      Combining conjugated poylmers and TiO2 in hybrid bulk-heterojunctions is a promising method for producing novel solar cells. Here TiO2 is introduced into a poly(p-phenylene vinylene) layer. Nanometer-scale phase separation allows efficient photoinduced charge transfer between the two components. The films can be used as the active layer in a photovoltaic cell and provide external quantum efficiencies of up to 11 % (see Figure).

    6. Non-Destructive Readout of the Photochromic Reactions of Diarylethene Derivatives Using Infrared Light (pages 121–125)

      K. Uchida, M. Saito, A. Murakami, S. Nakamura and M. Irie

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390023

      Non-destructive readout of an image using IR light on a polymer film containing a photochromic diarylethene was successively carried out. 1,2-Bis(2-methyl-6-phenyl-1-benzothiophen-3-yl)hexafluorocyclopentene was found to exhibit a remarkable IR spectral change around 1590 cm–1 upon photoirradiation, as demonstrated in the Figure.

    7. “(Hot-)Water-Proof”, Semiconducting, Platinum-Based Chain Structures: Processing, Products, and Properties (pages 125–129)

      W.R. Caseri, H.D. Chanzy, K. Feldman, M. Fontana, P. Smith, T.A. Tervoort, J.G.P. Goossens, E.W. Meijer, A.P.H.J. Schenning, I.P. Dolbnya, M.G. Debije, M.P. de Haas, J.M. Warman, A.M. van de Craats, R.H. Friend, H. Sirringhaus and N. Stutzmann

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390024

      A promising solution to the environmental instability of semiconducting organic materials is presented. Thin, highly ordered films (see Figure, a scanning probe microscopy image), fibers, and field-effect transistors (FETs), comprising chain-structures based on the so-called Magnus’ green salt, [Pt(NH3)4]-[PtCl4], were synthesized in aqueous media (see Cover). FETs were manufactured under ambient conditions from common organic solvents, and exposed—without significant loss of performance—to white light and air for periods of time in excess of 6 months, and to water of 90 °C for more than 12 h.

    8. Electrodeposition of Metallic Nanowire Thin Films Using Mesoporous Silica Templates (pages 130–133)

      D. Wang, W.L. Zhou, B.F. McCaughy, J.E. Hampsey, X. Ji, Y.-B. Jiang, H. Xu, J. Tang, R.H. Schmehl, C. O’Connor, C.J. Brinker and Y. Lu

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390025

      Metal nanowire thin films have been obtained by electrodeposition into mesoporous silica thin-film templates, resulting in nanowire arrays that reflect the pore structure of the template. Removal of silica is achieved via annealing followed by etching to leave mechanically strong freestanding metal nanowire films (see Figure). These metal films have many potential applications, such as electrodes, optical hosts, catalysts, magnetic materials, photovoltaic devices, and sensors.

    9. The Combination of Colloid-Controlled Heterogeneous Nucleation and Polymer-Controlled Crystallization: Facile Synthesis of Separated, Uniform High-Aspect-Ratio Single-Crystalline BaCrO4 Nanofibers (pages 133–136)

      S.-H. Yu, H. Cölfen and M. Antonietti

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390026

      Uniform, separated BaCrO4 single-crystalline nanofibers with high aspect ratio (> 5000, see Figure) can be fabricated at room temperature in aqueous solution using a double hydrophilic block copolymer as structure-directing agent and introducing colloidal nucleation agents. Such fibers represent a model case for advanced polymer fillers and the exploration of quasi-1D nanostructures with interesting electrical, optical, or catalytic properties.

    10. Polyaniline Nanotubes Doped with Sulfonated Carbon Nanotubes Made Via a Self-Assembly Process (pages 136–139)

      Z. Wei, M. Wan, T. Lin and L. Dai

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390027

      Sulfonated multiwalled carbon nanotubes (MWNT-(OSO3H)n) can act simultaneously as a dopant and template for the formation of conducting polyaniline(PANI) nanostructures. By controlling the aniline/MWNT-(OSO3H)n ratio, two kinds of nanotubes—PANI-coated MWNT-(OSO3H)n nanotubes and PANI nanotubes doped with MWNT-(OSO3H)n (see Figure)—can be obtained.

    11. Controlling Dielectric and Optical Properties of Ordered Mesoporous Organosilicate Films (pages 139–143)

      A.R. Balkenende, F.K. de Theije and J.C.K. Kriege

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390028

      Mesoporous hybrid inorganic–organic silicate films with pendant methyl groups are prepared. With a high organic fraction, these films are hydrophobic, which is important in the fabrication of low-k dielectrics. The refractive index of layers with smaller organic fraction can be switched reversibly over a large refractive index interval by varying the relative humidity (see Figure).

    12. Diameter-Controlled Growth of Single-Crystalline In2O3 Nanowires and Their Electronic Properties (pages 143–146)

      C. Li, D. Zhang, S. Han, X. Liu, T. Tang and C. Zhou

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390029

      Single-crystalline In2O3 nanowires have been synthesized using a laser ablation approach. Precise control over the nanowire diameter was achieved by using monodispersed gold clusters as the catalyst. Extensive material characterization has been carried out to determine the lattice structure (see Figure) and dimensions of these nanowires. Individual In2O3 nanowires have been utilized to construct field-effect transistors with on/off ratios up to 1000.

    13. An Unusual Electrochromic Device Based on a New Low-Bandgap Conjugated Polymer (pages 146–149)

      H. Meng, D. Tucker, S. Chaffins, Y. Chen, R. Helgeson, B. Dunn and F. Wudl

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390030

      A new low-bandgap conjugated polymer is synthesized (see Figure for structure). It is transparent, easily processed, and exhibits electrochromic behavior specific to the near-infrared region of the spectrum. The absence of electrochromic behavior in the visible range may permit this polymer to be used in near-infrared device applications.

    14. Patterned Microstructures of Porous Silicon by Dry-Removal Soft Lithography (pages 149–152)

      D.J. Sirbuly, G.M. Lowman, B. Scott, G.D. Stucky and S.K. Buratto

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390031

      A new procedure to directly pattern a luminescent porous silicon substrate by dry-removal soft lithography is outlined. The ability to transfer a removed microstructure of porous silicon to a free-standing flexible polymer film is also demonstrated, and by removing strips in orthogonal directions, an array of PSi pillars is produced (see Figure).

    15. Relationship Between the Electro-Optic Performance of Polymer-Stabilized Liquid-Crystal Devices and the Fractal Dimension of Their Network Morphology (pages 152–156)

      I. Dierking

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390032

      A quantitative relationship is established between the electro-optic performance (reflectivity, transmittance, threshold field, response time) of a polymer-stabilized liquid-crystal and the network morphology of the cholesteric textures (see Figure). By analysis of independent preparation series, varying curing temperature, UV intensity, and irradiation time, respective scaling relations are proposed.

    16. Sonochemical Synthesis of CdSe Hollow Spherical Assemblies Via an In-Situ Template Route (pages 156–159)

      J.J. Zhu, S. Xu, H. Wang, J.M. Zhu and H.-Y. Chen

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390033

      CdSe hollow spherical assemblies composed of 5 nm nanoparticles have been synthesized sonochemically. During the process, amorphous Cd(OH)2, which acts as the in-situ template, directs the growth of primary CdSe nanoparticles on its surface and their assembly into hollow spherical structures. The Figure is a schematic of the proposed mechanism for the formation of the hollow chalcogenide spheres.

    17. Ordered Arrays of Nanopillars Formed by Photoelectrochemical Etching on Directly Imprinted TiO2 Single Crystals (pages 159–161)

      H. Masuda, K. Kanezawa, M. Nakao, A. Yokoo, T. Tamamura, T. Sugiura, H. Minoura and K. Nishio

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390034

      Arrays of TiO2 nanopillars have been prepared by photochemically etching a TiO2 single crystal that had been previously imprinted with a corresponding array of dimples using SiC molds. The pillars have a high aspect ratio (see scanning electron microscopy (SEM) image in Figure) and the method is simple and suitable for high-throughput production.

    18. Ordered Mosaic Nanocomposites in Anodic Porous Alumina (pages 161–164)

      H. Masuda, A. Abe, M. Nakao, A. Yokoo, T. Tamamura and K. Nishio

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390035

      A mosaic consisting of pillars of two kinds of metal, gold and nickel, has been deposited on porous alumina substrates. A sequence of barrier layer application, selective penetration of the barrier, and metal deposition can be manipulated to control the arrangement and density of the composites. An array of Au (brighter) and Ni cylinders is shown in the Figure.

    19. Orthogonal Carbon Nanofibers by Template-Mediated Assembly of Discotic Mesophase Pitch (pages 164–167)

      K.Q. Jian, H.-S. Shim, A. Schwartzman, G.P. Crawford and R.H. Hurt

      Version of Record online: 27 JAN 2003 | DOI: 10.1002/adma.200390036

      Novel carbon nanofibers (see Figure) are synthesized by capillary impregnation of discotic mesophase pitch into nanochannel alumina. Heating and chemical etching produces nanofibers with a unique “orthogonal” arrangement of graphene layers. Unlike conventional nanofibers and -tubes, the graphene planes lie transverse to the fiber axis, which reflects the equilibrium state for the discotic precursor confined to nanocylindrical geometry.