Advanced Materials

Cover image for Advanced Materials

June, 2000

Volume 12, Issue 13

Pages 935–998

    1. True Blue Inorganic Optoelectronic Devices (pages 935–946)

      D. A. Gaul and W. S. Rees Jr.

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<935::AID-ADMA935>3.0.CO;2-J

      The realization of blue light-emitting optoelectronic devices has attracted much attention. Here the leading candidates (ZnSe, GaN, SiC, organic polymers) are examined, and research towards the improvement of zinc selenide in particular is reviewed. Deposition methods, precursors, and p-type dopants are all discussed. The Figure shows a p–n junction after equilibration.

    2. Direct Measurement of the Microscale Conductivity of Conjugated Polymer Monolayers (pages 947–950)

      P. Bøggild, F. Grey, T. Hassenkam, D. R. Greve and T. Bjørnholm

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<947::AID-ADMA947>3.0.CO;2-7

      The in-plane conductivity of conjugated polymer monolayers is mapped here for the first time on the microscale using a novel scanning micro four-point probe (see Figure). The probe allows the source, drain, and voltage electrodes to be positioned within the same domain and the mapping results demonstrate how microscopic ordering in the polymer domains controls the conductivity.

    3. Photocontrolled Orientation of Discotic Liquid Crystals (pages 950–953)

      K. Ichimura, S. Furumi, S. Morino, M. Kidowaki, M. Nakagawa, M. Ogawa and Y. Nishiura

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<950::AID-ADMA950>3.0.CO;2-V

      Surface-assisted orientational control of discotic liquid crystals (DLCs) induced by photoaligning thin films of an azobenzene-containing polymer is described. The photochemical technique developed can be used to photopattern DLC films (see Figure), which may have applications in novel molecular devices such as optical compensatory sheets, and provides an opportunity for understanding the orientation mechanism of DLCs.

    4. Core–Shell Microspheres of a Catalytically Active Rhodium Complex Bound to a Polyelectrolyte-Coated Latex (pages 953–956)

      S. Mecking and R. Thomann

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<953::AID-ADMA953>3.0.CO;2-J

      A strategy for the immobilization of catalytically active transition metal complexes is described in which the rhodium hydride complex [(H)Rh(CO)(NaTPPTS)3] is electrostatically bound to highly charged polystyrene microspheres coated with cationic polyelectrolyte (see Figure). The catalytic activity of this latex-bound catalyst in the hydroformylation of methyl acrylate is reported and compared with its unbound equivalent.

    5. Synthesis of Monodisperse Spherical Silicon Dicarbodiimide Particles (pages 956–961)

      Y.-L. Li, E. Kroke, A. Klonczynski and R. Riedel

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<956::AID-ADMA956>3.0.CO;2-7

      Spherical particles of silicon dicarbodiimide (SiC2N4, see Figure) are synthesized here via the reaction of tetrachlorosilane (T) and bis (trimethylsilyl)carbodiimide (B) using pyridine as a catalyst and toluene or tetrahydrofuran as solvent. It is shown that the morphology of the thus obtained monodisperse particles strongly depends on the molar ratio of the reagents and the type and amount of solvent used.

    6. The Internal Architecture of Mesoporous Silica Fibers (pages 961–965)

      F. Marlow, B. Spliethoff, B. Tesche and D. Zhao

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<961::AID-ADMA961>3.0.CO;2-N

      The mesopores in silica fibers run in a circular direction around the axis(see Figure), as demonstrated here by examining the optical properties and electron microscopy images of mesoporous silica fibers grown by slow acid synthesis. These fibers are a unique example of a material that is highly ordered on the nanometer scale, but where the ordering does not lead to translational invariance in all three dimensions.

    7. A New Method to Control Particle Size and Particle Size Distribution of SnO2 Nanoparticles for Gas Sensor Applications (pages 965–968)

      E. R. Leite, I. T. Weber, E. Longo and J. A. Varela

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<965::AID-ADMA965>3.0.CO;2-7

      The controlled growth of SnO2 nanoparticles for gas sensor applications is reported by these authors. Nb2O5 additive is used to control nucleation and growth of the SnO2 (see Figure), which is synthesized by the polymeric precursor method. Preliminary gas sensing measurements are performed and it is demonstrated that the response time of the Nb2O5-doped SnO2 is faster than that of the undoped material.

    8. Polymer–Salt Complexes Containing Silver Ions and Their Application to Facilitated Olefin Transport Membranes (pages 968–971)

      S. U. Hong, J. H. Jin, J. Won and Y. S. Kang

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<968::AID-ADMA968>3.0.CO;2-W

      The separation of olefin/paraffin mixtures using polymer–silver complexes is explored here. Composite membranes of 1:1 (C[DOUBLE BOND]O/Ag) poly(2-ethyl-2-oxazoline)/AgBF4 on microporous polysulfone support are shown to facilitate the transport of propylene, with its permeance and pure gas selectivity over propane increasing 450-fold when compared to pure polymer membranes.

    9. Polarized Electroluminescence from an Anisotropic Nematic Network on a Non-contact Photoalignment Layer (pages 971–974)

      A. E. A. Contoret, S. R. Farrar, P. O. Jackson, S. M. Khan, L. May, M. O'Neill, J. E. Nicholls, S. M. Kelly and G. J. Richards

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<971::AID-ADMA971>3.0.CO;2-J

      Polarized electroluminescence from a uniformly aligned nematic network, formed by photopolymerization of a LC monofluorene with diene end-groups (see Figure), is reported. It is shown that macroscopic orientation of the chromophore is achieved with a photoalignment layer doped to allow hole transport. Thus standard photolithography can be used to make polarized, patterned, multilayer organic electroluminescent displays.

    10. Fully Functionalized Photorefractive Polymers Incorporating Transition Metal Phthalocyanine and Porphyrin Complexes as Photosensitizers (pages 974–978)

      Q. Wang, L. Wang, J. Yu and L. Yu

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<974::AID-ADMA974>3.0.CO;2-7

      Photorefractive polymers containing transition metal porphyrin or phthalocyanine complexes (see Figure) are prepared here by Heck polycondensation, and the structural effects of these macrocyclic complexes on the photorefractive performance are investigated. It is reported that the polymers containing Zn complexes exhibit much larger photogeneration quantum yields and optical gains than those containing Cu.

    11. Charge Transport versus Optical Properties in Semiconducting Crystalline Organic Thin Films (pages 978–983)

      J. Cornil, J. P. Calbert, D. Beljonne, R. Silbey and J.-L. Brédas

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<978::AID-ADMA978>3.0.CO;2-S

      A theoretical approach to the characterization of the transport and optical properties of organic oligomer and polymer thin films is proposed. The approach—based on a correlated treatment of interchain interactions—is applied to two prototypical oligomeric materials, α-sexithienyl and α-α′-bisdithieno- [3,2-b:2′,3′-d]thiophene (see Figure).

    12. TCNQ Complex with θ-Type Donor Arrangement: (TMET-TS-TTP)2(TCNQ) (pages 983–985)

      M. Aragaki, H. Hoshino, T. Mori, Y. Misaki, K. Tanaka, H. Mori and S. Tanaka

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<983::AID-ADMA983>3.0.CO;2-7

      The conduction behavior down to low temperatures is emphasized in the study reported here of the title TCNQ complex of TMET-TS-TTP (shown in the Figure: X=Se, Y=S) because radical cation salts of TTP are promising organic conductors. The preparation, crystal structure, and electron spin resonance investigation of the TCNQ complex are presented.

    13. Photocalcination of Mesoporous Silica Films Using Vacuum Ultraviolet Light (pages 985–987)

      A. Hozumi, Y. Yokogawa, T. Kameyama, K. Hiraku, H. Sugimura, O. Takai and M. Okido

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<985::AID-ADMA985>3.0.CO;2-#

      Supramolecular assemblies of surfactant moleculesare often used to synthesize mesoporous silica (MPS). However, elimination of the surfactant molecules by conventional thermocalcination after MPS film synthesis often leads to film distortion or breakage. Here the effective removal of surfactant molecules at room temperature is described in which the hexagonal mesostructure of the film is preserved. The technique used—photocalcination—is based on the photochemical decomposition of organic molecules under irradiation with vacuum ultraviolet light.

    14. Adjusting the Porosity of a Silica-Based Hybrid Material (pages 989–992)

      B. Boury and R. J. P. Corriu

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<989::AID-ADMA989>3.0.CO;2-K

      Precise control of the porosity of silica-based hybrid materials is the topic discussed here. One approach in particular—the copolycondensation of two precursors followed by selective removal of one of the organic spacers (see Figure)—is highlighted. Using this technique, microporous hybrid xerogels are produced that have a high specific surface area and a highly hydrophobic surface.

    15. Nanostructured Gold Colloid Electrodes (pages 993–998)

      A. N. Shipway, M. Lahav and I. Willner

      Version of Record online: 7 JUL 2000 | DOI: 10.1002/1521-4095(200006)12:13<993::AID-ADMA993>3.0.CO;2-3

      Recent advances in the assembly of nanoparticle superstructures on electrodes are addressed here. Methods for the assembly and characterization of these arrays are summarized and their electronic, photoelectrochemical, and sensor applications are discussed. The Figure shows a one-layer architecture of Au nanoparticles and tetracationic cyclophanes on an amine-functionalized ITO support.