Advanced Materials

Cover image for Vol. 13 Issue 16

August, 2001

Volume 13, Issue 16

Pages 1217–1281

    1. Supramolecular Materials via Block Copolymer Self-Assembly (pages 1217–1229)

      H.-A. Klok and S. Lecommandoux

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1217::AID-ADMA1217>3.0.CO;2-D

      The potential of block copolymer type macromolecular building blocks for the preparation of self-assembled materials is discussed in this review. The basic principles that underlie the self-assembly of three different types of block copolymer architectures, i.e., coil–coil diblock copolymers, rod–coil diblock copolymers, and rod–coil oligomers, are revealed. The Figure shows part of the self-assembly process of a rod–coil oligomer.

    2. Dye-Doped Mesostructured Silica as a Distributed Feedback Laser Fabricated by Soft Lithography (pages 1231–1234)

      B. J. Scott, G. Wirnsberger, M. D. McGehee, B. F. Chmelka and G. D. Stucky

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1231::AID-ADMA1231>3.0.CO;2-8

      Distributed feedback (DFB) laserswere made on silicon substrates by using elastomeric stamps to pattern dye-doped mesostructured silica into ridge waveguides with a grating on top. The emission spectra of the lasers have several peaks with a full width at half maximum of 0.3 nm (see Figure). The lasers were photopumped and had a lasing threshold intensity of ∼55 kW/cm2.

    3. Modification of Indium Tin Oxide for Improved Hole Injection in Organic Light Emitting Diodes (pages 1234–1238)

      Y. Shen, D. B. Jacobs, G. G. Malliaras, G. Koley, M. G. Spencer and A. Ioannidis

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1234::AID-ADMA1234>3.0.CO;2-R

      The efficiency of multi-layer OLEDs using indium tin oxide (ITO) and triphenyldiamine is limited by the hole injection rate, or the quality of the contact between the two components, respectively. Coating the ITO with an ultra-thin Pt layer dramatically improves hole injection, and significantly lowers the devices' operating voltage. The Figure juxtaposes AFM images of an unmodified (left) and Pt-coated ITO electrode (right).

    4. Synthesis of Ordered Single Crystal Silicon Nanowire Arrays (pages 1238–1241)

      X.-Y. Zhang, L.-D. Zhang, G.-W. Meng, G.-H. Li, N.-Y. Jin-Phillipp and F. Phillipp

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1238::AID-ADMA1238>3.0.CO;2-3

      The fast and inexpensive production of single-crystal silicon nanowires, which circumvents the use of lithography, is achieved by pyrolysis of silane in nanochannel alumina with a gold catalyst. The nanowires (see Figure for an SEM image) are very straight, not intertwined, and uniform in diameter and length. They should be good candidates for silicon field emitter arrays with high tip density.

    5. Rare Earth Complex as a High-Efficiency Emitter in an Electroluminescent Device (pages 1241–1245)

      Z. R. Hong, C. J. Liang, R. G. Li, W. L. Li, D. Zhao, D. Fan, D. Y. Wang, B. Chu, F. X. Zang, L.-S. Hong and S.-T. Lee

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1241::AID-ADMA1241>3.0.CO;2-6

      A red-light emitting europium complex(see Figure) is investigated here as an alternative to traditional fluorescent materials, which have an inherent electroluminescence (EL) efficiency limited to 25 % of their photoluminescence (PL) efficiency. It is shown that by optimizing the structure of Eu complex–based devices significant improvements in the EL efficiency and stability can be obtained.

    6. Reduction of Self-Quenching Effect in Organic Electrophosphorescence Emitting Devices via the Use of Sterically Hindered Spacers in Phosphorescence Molecules (pages 1245–1248)

      H. Z. Xie, M. W. Liu, O. Y. Wang, X. H. Zhang, C. S. Lee, L. S. Hung, S. T. Lee, P. F. Teng, H. L. Kwong, H. Zheng and C. M. Che

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1245::AID-ADMA1245>3.0.CO;2-J

      The incorporation of a sterically demanding pinene moietyinto the ligand of a phosphorescent iridium complex prevents self-quenching by neighboring molecules, raising its photoluminescence quantum yield to 0.71 in solution. The compound is highly interesting as a dopant in electroluminescent devices, as shown for various concentrations of the complex in 4,4′-bis-(carbazolyl)-biphenyl (CBP) (see Figure).

    7. Rapid and Efficient Post-Polymerization Functionalization of Poly(3,4-ethylenedioxythiophene) (PEDOT) Derivatives on an Electrode Surface (pages 1249–1252)

      M. Besbes, G. Trippé, E. Leviallain, M. Mazari, F. Le Derf, I. F. Perepichka, A. Derdour, A. Gorgues, M. Sallé and J. Roncali

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1249::AID-ADMA1249>3.0.CO;2-W

      First examples of post-polymerization functionalization of poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives are reported using tetrathiafulvalene (TTF) as a redox sensitive probe. EDOT derivatives bearing ω-iodo-alkyl or ω-iodo-polyether chains attached at the ethylenedioxy bridge have been electropolymerized and the resulting polymers have been derivatized using a TTF bearing a thiolate anion liberated under mild conditions. Cyclic voltammetry confirms the rapidity and efficiency of the derivatization process. This facile post-polymerization functionalization coupled with the unique properties of PEDOT should lead to interesting developments in the field of modified electrodes, which includes selective electrochemical sensors.

    8. Preparation, Characterization, and Application of Au-Shell/Polystyrene Beads and Au-Shell/Magnetic Beads (pages 1253–1256)

      T. Ji, V. G. Lirtsman, Y. Avny and D. Davidov

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1253::AID-ADMA1253>3.0.CO;2-T

      Multifunctional core–shell particles composed of magnetic particles covered with a gold nanoshell can be induced to align into conducting lines upon application of a magnetic field (see Figure). The formation of Au clusters and “streaky” gold nanoparticles on the surface of the PS beads is demonstrated and the preparation, characterization, and applications of magnetic and polystyrene beads featuring a gold shell are addressed.

    9. Controlled Surface-Initiated Polymerizations in Aqueous Media (pages 1256–1259)

      D. M. Jones and W. T. S. Huck

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1256::AID-ADMA1256>3.0.CO;2-B

      The rapid, controlled formation of thick brushes (up to 125 nm thick) from self- assembled monolayer-bound initiators under mild conditions using aqueous solutions is demonstrated. Atom transfer radical polymerization (ATRP) has been employed to create polymers and copolymers from surfaces (see Figure). This technology may lead to molecular “ultra-glues” for adhesion to suitable substrates.

    10. Synthesis of Large Monolithic Zeolite Foams with Variable Macropore Architectures (pages 1259–1263)

      Y.-J. Lee, J. S. Lee, Y. S. Park and K. B. Yoon

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1259::AID-ADMA1259>3.0.CO;2-U

      Very large monolithic three-dimensional structures have been prepared using polyurethane foams. These cheap, readily available, and highly versatile foams are excellent templates for the fabrication of macro- and microporous silica and zeolite materials as is unveiled in this communication. The Figure displays an SEM image showing the morphology and connectivity of a zeolite foam.

    11. Direct Synthesis of Alkoxide-Intercalated Derivatives of Hydrocalcite-like Layered Double Hydroxides: Precursors for the Formation of Colloidal Layered Double Hydroxide Suspensions and Transparent Thin Films (pages 1263–1266)

      E. Gardner, K. M. Huntoon and T. J. Pinnavaia

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1263::AID-ADMA1263>3.0.CO;2-R

      Layered double hydroxide alkoxides obtained by precipitation of MII and MIII salts with NaOH in alcoholic solution have unique properties. They exhibit very large BET surfaces, indicating a pillared structure, and their slow hydrolysis yields very smooth, almost transparent films of the corresponding hydroxides (see Figure for comparison of alkoxide-based, left, and conventionally produced films, right), with high internal order as verified by the XRD pattern.

    12. Tobacco Mosaic Virus Liquid Crystals as Templates for the Interior Design of Silica Mesophases and Nanoparticles (pages 1266–1269)

      C. E. Fowler, W. Shenton, G. Stubbs and S. Mann

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1266::AID-ADMA1266>3.0.CO;2-9

      Nematic liquid crystals of tobacco mosaic virus (TMV) can be used to prepare silica mesostructures or nanoparticles with linear or radial arrays of linear channels (see Figure and also cover). While the mesostructures form slightly compressed inverse replicas of the nematic phase with a 20 nm period, the nanoparticles are unusual radial arrays of mineralized TMV fragments around silica core.

    13. Electrophoretic Growth of Lead Zirconate Titanate Nanorods (pages 1269–1272)

      S. J. Limmer, S. Seraji, M. J. Forbess, Y. Wu, T. P. Chou, C. Nguyen and G. Z. Cao

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1269::AID-ADMA1269>3.0.CO;2-S

      Nanorods of lead zirconate titanate (PZT)—a ferro- and piezoelectric material—up to 10 μm in length and 70 to 150 nm in diameter are produced by sol-gel electrophoresis of PZT in a track-etched polycarbonate membrane, which is used as a template. The Figure gives a close-up view of a PZT film with nanowires attached, as obtained after pyrolytic removal of the organic template.

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      Gate-Induced Superconductivity in Oligophenylenevinylene Single Crystals (pages 1273–1274)

      J. H. Schön, C. Kloc, J. Wildeman and G. Hadziioannou

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1273::AID-ADMA1273>3.0.CO;2-P

      A variation in transition temperature for the superconductivity of oligo(phenylenevinylene) (OPV) single crystals from the pentamer to the trimer has been found to exist (see Figure). The reason for this is given in this communication, which unveils the electrical properties of these materials. The results presented here clearly suggest the possibility of superconductivity in well-ordered poly(phenylenevinylene) (PPV) films.

    15. Polymer Light-Emitting Energy-Well Devices Using Single-Ion Conductors (pages 1274–1278)

      T.-W. Lee and O. O. Park

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1274::AID-ADMA1274>3.0.CO;2-J

      Dramatically improved luminance and quantum efficiency of electroluminescent devices is achieved by packing the emissive conjugated polymer between thin layers of a single-cation and a single-anion conductor. These layers, both consisting of charged polyurethanes, exhibit high ionic space charges near the electrodes, and afford excellent charge-injection as well as a charge-blocking properties. This results in balanced injection and confinement of electron–hole pairs, and, hence, superior quantum efficiency.

    16. Synthesis of Novel Nickel Sulfide Layer-Rolled Structures (pages 1278–1281)

      X. Jiang, Y. Xie, J. Lu, L. Zhu, W. He and Y. Qian

      Version of Record online: 17 AUG 2001 | DOI: 10.1002/1521-4095(200108)13:16<1278::AID-ADMA1278>3.0.CO;2-W

      Microtubes composed of rolled up layers of nickel sulfide can be prepared under mild conditions. The mechanism is proposed to involve self-assembly of Ni(NH3)2+6 into ordered arrays via hydrogen bonding interactions with water, followed by conversion to NiS layers upon addition of CS2. The layers then roll up when heated (see Scheme).