Advanced Materials

Cover image for Vol. 13 Issue 11

June, 2001

Volume 13, Issue 11

Pages 783–839

    1. Electrochromic Systems and the Prospects for Devices (pages 783–793)

      D. R. Rosseinsky and R. J. Mortimer

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<783::AID-ADMA783>3.0.CO;2-D

      Electrochromic materials are well sought after as they promise a variety of applications. The field of electrochromism is judiciously discussed in this review, where a focus is laid on basic principles, materials, and present and future applications, ranging from the currently available anti-dazzle car mirrors to displays (see Figure), windows, and food monitoring and ticket authentication devices.

    2. A Route to Nanoscopic SiO2 Posts via Block Copolymer Templates (pages 795–797)

      H.-C. Kim, X. Jia, C. M. Stafford, D. H. Kim, T. J. McCarthy, M. Tuominen, C. J. Hawker and T. P. Russell

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<795::AID-ADMA795>3.0.CO;2-1

      A surface covered with a nanopatterned, regularly spaced array of SiO2 blocksis obtained by coating silica with a block copolymer, selectively removing one polymer from the layer, depositing SiO2 in the voids, and finally degrading the second polymer. The Figure shows an AFM image of a finished sample. Rough surfaces of this type are very promising candidates for sensor and lab-on-a-chip applications.

    3. Intercalation and Solution Processing of Bismuth Telluride and Bismuth Selenide (pages 797–800)

      Z. Ding, L. Viculis, J. Nakawatase and R. B. Kaner

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<797::AID-ADMA797>3.0.CO;2-U

      A low-temperature method for the preparation of colloidal suspensions of bismuth telluride and selenide is presented. The method is based on Li intercalation, which can be followed by exfoliation and eventually restacking, thus leading to layered structures (see Figure and cover). The process and its parameters and characteristics are discussed in this work.

    4. Organic–Inorganic Nanocomposites with Completely Defined Interfacial Interactions (pages 800–803)

      R. M. Laine, J. Choi and I. Lee

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<800::AID-ADMA800>3.0.CO;2-G

      Access to structure–processing property relationships in nanocomposites is given through the work undertaken by these authors. Their approach relies on linking cubic silsesquioxane (see Figure) by organic tethers. The analytical data presented here form strong foundations for the formation of nanocomposites with well-defined interfaces and periodicity.

    5. Electrochemically Induced, Reversible Morphology Changes of Regioregular Oligo-3-alkylthiophene Film (pages 803–806)

      M. Lapkowski, M. Kolodziej-Sadlok, J. Zak, S. Guillerez and G. Bidan

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<803::AID-ADMA803>3.0.CO;2-4

      The solid-state electrochemical properties of sexi(3-octylthiophene), 6OT, see Figure, which is assumed to be an excellent model system for regioregular poly(alkylthiophenes), are reported. The electrochemically induced, reversible appearance of hills and valleys in the film is thought to confirm the formation of π dimers or π stacks as suggested previously.

    6. Chemical Nanolithography with Electron Beams (pages 803–806)

      A. Gölzhäuser, W. Eck, W. Geyer, V. Stadler, T. Weimann, P. Hinze and M. Grunze

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<803::AID-ADMA806>3.0.CO;2-W

      A highly focused electron beam as the agent for spatially selective reductionof nitro groups to amino groups in a self-assembled monolayer of aromatics is the key feature of a novel technique in chemical nanolithography presented here. Treatment of the reactive amino groups with different reactants after each e-beam writing step yields a surface with a defined array of chemically diverse structures; for example, see the line pattern in the Figure.

    7. De-mixing of Polyfluorene-Based Blends by Contact with Acetone: Electro- and Photo-luminescence Probes (pages 810–814)

      J. Morgado, E. Moons, R. H. Friend and F. Cacialli

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<810::AID-ADMA810>3.0.CO;2-C

      Phase separation of polyfluorene-based polymer blends is studied via photo- and electro-luminescence. By looking at Förster energy transfer, the authors prove that luminescence spectroscopy is a sensitive probe of the polymer environment, with a resolution of a few nanometers, which is advantageous over atomic force microscopy when the interpretation of the latter is complicated by a rich surface structure. De-mixing of the blends is found to occur upon exposure to a very poor solvent (acetone), and is attributed to enhanced segmental and chain dynamics of the macromolecular chains.

    8. Frequency Conversion in (NaPO3)x Polyphosphate Glass by Stimulated Raman Scattering (pages 814–816)

      R. Burkhalter, B. Trusch, A. A. Kaminskii, G. M. A. Gad, H. J. Eichler and J. Hulliger

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<814::AID-ADMA814>3.0.CO;2-X

      A promising new materialfor the investigation of near-infrared Raman-based laser shifters and amplifiers is found in polyphosphate glass (a typical Graham salt ingot is shown in the Figure). The presented studies on this material show Raman shifts larger than those obtained for many other crystalline materials and a gain coefficient that is larger than that of calcite.

    9. Alloy Formation in Nanostructured Silicon (pages 816–819)

      B. Gao, S. Sinha, L. Fleming and O. Zhou

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<816::AID-ADMA816>3.0.CO;2-P

      The first systematic study on alloy formation on well-defined nanostructured materialshas been conducted by these authors. Nanostructured silicon and germanium materials were reacted with lithium metal by solid-state chemistry and electrochemical methods, in which nanocrystalline Si (unlike bulk material) forms Li–Si alloys already at room temperature. The Li–Si(Ge) alloys have interesting electrochemical properties, which make them attractive as anode material in lithium batteries.

    10. Fluorescent Beads Coated with Polyaniline: A Novel Nanomaterial for Optical Sensing of pH (pages 819–822)

      E. Pringsheim, D. Zimin and O. S. Wolfbeis

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<819::AID-ADMA819>3.0.CO;2-D

      A novel optical pH sensor for the physiological rangehas been developed by these authors. The fluorescence emitted (in a pH-independent manner) by dye-doped polymer nanobeads is modulated by a thin conductive polymer coating (see Figure), whose visible-light absorption strongly varies with pH at values around seven.

    11. Ordered Mesoporous Silica Coatings That Induce Apatite Formation In Vitro (pages 822–825)

      J. M. Gomez-Vega, A. Hozumi, H. Sugimura and O. Takai

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<822::AID-ADMA822>3.0.CO;2-0

      Alternative coatings for load-bearing medical implants are required. Those prepared in the biomimetic approach reported here have three important features: the mesostructure is aligned even on amorphous substrates, they can be photocalcined, and they precipitate apatite in simulated body fluid (SBF). The Figure shows the surface of such a mesoporous silica coating on Ti6Al4V after immersion in SBF for 15 days.

    12. Dye-Sensitized Nanocrystalline Solar Cells Employing a Polymer Electrolyte (pages 826–830)

      A. F. Nogueira, J. R. Durrant and M. A. De Paoli

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<826::AID-ADMA826>3.0.CO;2-L

      Effective cationic dye-sensitized nanocrystalline titania solar cells employing an elastomeric copolymer of ethylene glycol and epichlorohydrin as electrolyte and I/I3 as mobile redox carrier system have been developed by these authors. The key feature of the copolymer is its ability to penetrate the pores of the TiO2 film in spite of its high molecular weight. Unsealed prototype cells show 1.6–2.6 % energy conversion efficiency, thus demonstrating that polymer electrolytes are an attractive alternative to previously reported hole-transporting materials.

    13. Production and in-situ Metal Filling of Carbon Nanotubes in Water (pages 830–833)

      Y. L. Hsin, K. C. Hwang, F.-R. Chen and J.-J. Kai

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<830::AID-ADMA830>3.0.CO;2-4

      Growing carbon nanotubes (CNTs) by arcing from graphite electrodes does not demand a noble gas atmosphere: water will do! CO and H2 bubbles generated by reaction of C vapor with water provide a quasi-inert atmosphere in which multiwalled carbon nanotubes grow from the cathode. Using cobalt salt solutions instead of plain water, the authors obtained CNTs filled with metallic cobalt and elemental sulfur (see Figure), potentially useful as nanoprobes for magnetic force microscopy.

    14. A New Luminescent Organic–Inorganic Hybrid Compound with Large Optical Nonlinearity (pages 833–837)

      A. M. Guloy, Z. Tang, P. B. Miranda and V. I. Srdanov

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<833::AID-ADMA833>3.0.CO;2-T

      The successful incorporation of an organic chromophore with highly polarizable lead iodide chains in an organic–inorganic hybrid is revealed in this communication. The synthesis, structure, and preliminary studies of the linear and nonlinear optical (NLO) properties of the compound are divulged. The synergism exhibited between polarizable inorganic polymers and hyperpolarizable organic molecules provides a route to new multi-functional NLO materials.

    15. Controlled Drug Delivery from Polymers by Mechanical Signals (pages 837–839)

      K. Y. Lee, M. C. Peters and D. J. Mooney

      Version of Record online: 31 MAY 2001 | DOI: 10.1002/1521-4095(200106)13:11<837::AID-ADMA837>3.0.CO;2-D

      Using mechanical signals to control the release of drugs from polymers is an attractive option for drug administration. Two types of model systems (see Figure), one where the drug molecules do not interact with the polymer matrix and the other where both free and bound drug molecules are present, are considered in this work and the results with three different model drugs incorporated into hydrogels are reported.