Advanced Materials

Cover image for Vol. 14 Issue 8

April, 2002

Volume 14, Issue 8

Pages 545–616

    1. Contents: Adv. Mater. 8/2002 (pages 545–548)

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<545::AID-ADMA545>3.0.CO;2-B

    2. Contents: Adv. Funct. Mater. 4/2002 (pages 550–552)

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<550::AID-ADMA550>3.0.CO;2-R

    3. Encapsulated Conducting Polymers (pages 553–563)

      D.J. Cardin

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<553::AID-ADMA553>3.0.CO;2-F

      Encapsulation of conjugated polymers minimizes interchain effects, improves the stability, and may allow individual molecular wires to be addressed. A survey of such systems composed of an inorganic or organic host, and organic or quasimetallic guests is presented. The Figure schematically shows the synthesis of a polyrotaxane, i.e., a polymer threaded into a tubular host and held in place by bulky end caps.

    4. Interfacial Microstructure Function in Organic Light-Emitting Diodes: Assembled Tetraaryldiamine and Copper Phthalocyanine Interlayers (pages 565–569)

      J. Cui, Q. Huang, J.G.C. Veinot, H. Yan and T.J. Marks

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<565::AID-ADMA565>3.0.CO;2-3

      Drastically increased OLED device luminance (up to 15 000 cd/m2) and enhanced quantum efficiency (6×) are achieved by spin-coating a siloxane-derivatized hole injector (TPD-Si2) onto an ITO surface. The silyl groups promote ITO–TPD interfacial cohesion, thus enabling more efficient hole injection. The Figure shows a polarized optical image of the TPD film morphology after annealing the bilayer structure (see also inside front cover).

    5. Two Component Particle Arrays on Patterned Polyelectrolyte Multilayer Templates (pages 569–572)

      H. Zheng, I. Lee, M.F. Rubner and P.T. Hammond

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<569::AID-ADMA569>3.0.CO;2-O

      The selective adsorption of two different types of particles to a patterned surface is shown for thiol-modified gold. The far end of the alkanethiols is chemically varied and binds polymer particles with different properties—as illustrated in the Figure for charged polymer particles of different composition and size. Tuning of hydrophobicity and hydrogen bonding in this manner provides a versatile route to composite colloidal structures.

    6. Controlled Cluster Size in Patterned Particle Arrays via Directed Adsorption on Confined Surfaces (pages 572–577)

      I. Lee, H. Zheng, M.F. Rubner and P.T. Hammond

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<572::AID-ADMA572>3.0.CO;2-B

      Regular arrays of single colloidal particles on confined regions of patterned polyelectrolyte templates are fabricated based on alternating charged docking sites and neutral deposition resists on the surface. The diameter ratio between surface patterns and the colloid controls the size and spatial arrangement of the clusters. The Figure shows an optical image of up to seven-membered clusters of colloidal beads 4.3 μm in diameter (see also cover).

    7. Fully Vapor-Deposited Thin-Layer Titanium Dioxide Solar Cells (pages 577–581)

      M. Thelakkat, C. Schmitz and H.-W. Schmidt

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<577::AID-ADMA577>3.0.CO;2-S

      Titanium dioxide solar cells on top of a wide range of substrates, even flexible plastics, are accessible by chemical vapor deposition (CVD) of TiO2 by resistive heating of Ti3O5 under partial oxygen pressure. Cells using TiO2 in combination with Cu phthalocyanine on ITO substrates (see Figure) are most effective if the TiO2 layer is thin (15 nm), and if a further perylene dye layer is used to tune the wavelength of light absorption.

    8. High-Efficiency Polymer-Based Electrophosphorescent Devices (pages 581–585)

      X. Gong, M.R. Robinson, J.C. Ostrowski, D. Moses, G.C. Bazan and A.J. Heeger

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<581::AID-ADMA581>3.0.CO;2-B

      High efficiency electrophosphorescence has been achieved by using [Ir(DPF)3]-doped polyvinylcarbazole/biphenyl-1,3,4-oxadiazole co-polymers (see Figure). Light-emitting devices with luminous efficiencies up to 36 cd/A can be realized with polymeric host/heavy metal complex guest systems, fabricated by processing the luminescent layer from solution.

    9. Gold Glyconanoparticles as Building Blocks for Nanomaterials Design (pages 585–588)

      T.C. Rojas, J.M. de la Fuente, A.G. Barrientos, S. Penadés, L. Ponsonnet and A. Fernández

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<585::AID-ADMA585>3.0.CO;2-W

      Glycofunctionalized gold nanoparticles can easily be manipulated as water-soluble macromolecules, highly stable in colloidal solutions. Different nanostructures (see Figure for an example) have been obtained by varying the particle concentration, the Ca2+ level in the solution, and type of oligosaccharide. A potential application of the particle arrays, whose properties resemble those of large biomolecules, is as nanoscale size-selection devices.

    10. Towards Plastic Electronics: Patterning Semiconducting Polymers by Nanoimprint Lithography (pages 588–591)

      M. Behl, J. Seekamp, S. Zankovych, C.M. Sotomayor Torres, R. Zentel and J. Ahopelto

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<588::AID-ADMA588>3.0.CO;2-K

      The direct patterning of functional semiconducting polymers (see Figure) has been achieved with a nanoimprint lithography technique. The room-temperature process described is time-saving as repeated temperature cycling is not required. In addition, due to the direct patterning approach the need for further processing steps (plasma treatment) to pattern the underlying semiconducting material is eliminated.

    11. Huge, Millicoulomb Charge Storage in Ceramic Hydroxyapatite by Bimodal Electric Polarization (pages 591–595)

      M. Ueshima, S. Nakamura and K. Yamashita

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<591::AID-ADMA591>3.0.CO;2-7

      Ceramic hydroxyapatite stores up to 1.2 mC/cm2 of charge if the electret is poled at high temperature and cooled down in the presence of a field. This extraordinary storage capacity, determined by thermally stimulated depolarization measurements, was obtained at 5 kV and 873 K. The Figure illustrates some of the mechanisms, apart from H+ transport, that are involved in charge dislocation: dehydration and O2– migration at high temperature.

    12. 3D Hybrid Nanonetworks from Gold-Functionalized Nanoparticles (pages 595–597)

      C.R. Mayer, S. Neveu and V. Cabuil

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<595::AID-ADMA595>3.0.CO;2-S

      Highly ordered 3D hybrid networks of gold nanoparticles assemble after in-situ generation of linkers between particles, achieved by amide-bond formation. Unlike their counterparts obtained by linking Au nanoparticles with 1,ω-dithiols, which are amorphous, these networks show a regular hexagonal array (see Figure).

    13. Assessment of Theoretical Approaches to the Evaluation of Dipole Moments of Chromophores for Nonlinear Optics (pages 597–600)

      O.V. Prezhdo

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<597::AID-ADMA597>3.0.CO;2-K

      The calculation of dipole moments of nonlinear optical (NLO) chromophores can be carried out with a variety of theoretical approaches. A systematic study of the available calculation methods is presented. The study focuses on a series of NLO chromophores with varying electron-donor and electron-acceptor fragments and differing length of the π-conjugated system (see Figure for an example of the chromophores studied).

    14. Dipolar Response of Metallic Copper Nanocrystal Islands, Studied by Two-Step Near-Field Microscopy (pages 601–604)

      P. André, F. Charra, P.-A. Chollet and M.-P. Pileni

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<601::AID-ADMA601>3.0.CO;2-2

      How does light modify the surface of a photosensitive polymer? Upon polarized laser light irradiation of an azo-dye-substituted polymethacrylate film with copper nanocrystal islands periodic surface structures arise. Their morphology (see Figure for an AFM image, with ripple structures marked by arrows) suggests that these structures are interference patterns of incoming laser light with radiation emitted by the copper platelets, which act as dipoles.

    15. Growth of Large Colloidal Crystals with Their (100) Planes Orientated Parallel to the Surfaces of Supporting Substrates (pages 605–608)

      Y. Yin and Y. Xia

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<605::AID-ADMA605>3.0.CO;2-N

      Large colloidal crystals with substrate-parallel (100) planes have been fabricated by crystallizing polystyrene beads into 3D opaline lattices on regular arrays of square pyramidal pits etched in Si(100) wafers; the Figure shows an SEM micrograph of a quasicrystal edge. The long-range ordered spherical colloids, covering areas up to several square centimeters, are promising candidates for photonics and porous materials.

    16. Superstructures of Self-Organizing Thiophenes (pages 609–616)

      E. Mena-Osteritz

      Article first published online: 18 APR 2002 | DOI: 10.1002/1521-4095(20020418)14:8<609::AID-ADMA609>3.0.CO;2-7

      Self-assembly of π-conjugated oligomers (see Figure for an example) has been studied with different techniques. STM has successfully been applied and sub-molecular resolution in the images has been achieved. Supported by X-ray structure analyses of the 3D bulk material and by theoretical calculations, molecular conformations, and molecule–molecule and molecule–substrate interactions of the oligomers have been analyzed and identified.