Advanced Materials

Cover image for Advanced Materials

June, 2004

Volume 16, Issue 12

Pages 943–1030

    1. Contents: Adv. Mater. 12/2004 (pages 943–950)

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200490035

    2. Additive-Driven Phase-Selective Chemistry in Block Copolymer Thin Films: The Convergence of Top–Down and Bottom–Up Approaches (pages 953–957)

      P. Du, M. Li, K. Douki, X. Li, C. B. W. Garcia, A. Jain, D.-M. Smilgies, L. J. Fetters, S. M. Gruner, U. Wiesner and C. K. Ober

      Version of Record online: 3 JUN 2004 | DOI: 10.1002/adma.200306189

      Several strategies are demonstrated for the use of additive-driven chemistries that take place in only one type of the nanosized domains of all-organic and organic–inorganic hybrid block copolymer thin films. Such an approach is used to examine the convergence of “top–down” and “bottom–up” fabrication via light-driven processes. Characterization is carried out with microscopies and grazing-incidence small-angle X-ray scattering (see Figure and cover).

    3. Nanoseparated Polymeric Networks with Multiple Antimicrobial Properties (pages 957–961)

      C. H. Ho, J. Tobis, C. Sprich, R. Thomann and J. C. Tiller

      Version of Record online: 19 MAY 2004 | DOI: 10.1002/adma.200306253

      A multiply active antimicrobial network coating has been synthesized that contains nanophase-separated poly(ethylene imine) units and hydroxyl groups in the surrounding matrix. Silver nanoparticles can easily be loaded into the PEI phase and the hydroxyl groups of the matrix can be separately modified with polyethylene glycol. The resulting coating is an antimicrobial silver ion release system (Figure bottom—TEM image) with a contact-killing and microbe-repelling surface (Figure top—AFM image).

    4. Intracellular Delivery of Quantum Dots for Live Cell Labeling and Organelle Tracking (pages 961–966)

      A. M. Derfus, W. C. W. Chan and S. N. Bhatia

      Version of Record online: 19 MAY 2004 | DOI: 10.1002/adma.200306111

      Several strategies borrowed from the field of gene delivery are adapted to enhance delivery of semiconductor quantum dots (QDs) to the interior of live cells. To traffic QDs to subcellular organelles, QDs were then derivatized with known peptide localization sequences, demonstrating the ability to target QDs to the nucleus and mitochondria (see Figure).

    5. Free-Standing Gold Nanoparticle Membrane by the Spontaneous Reduction of Aqueous Chloroaurate Ions by Oxyethylene-Linkage-Bearing Diamine at a Liquid–Liquid Interface (pages 966–971)

      PR. Selvakannan, P. S. Kumar, A. S. More, R. D. Shingte, P. P. Wadgaonkar and M. Sastry

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200400116

      The one-step synthesis of a free-standing, robust gold nanoparticle membrane (see Figure) via the spontaneous reduction of aqueous chloroaurate ions by oxyethylene-bearing diamine molecules in chloroform at the liquid–liquid interface is described. Such simply assembled membranes may have important applications in separation methodologies and as surfaces for enzyme, DNA, and cell immobilization.

    6. Encapsulating a Superconducting Material, MgCNi3, in a Carbon Nanoflask (pages 972–975)

      R. K. Rana, V. G. Pol, I. Felner, E. Meridor, A. Frydman and A. Gedanken

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200306590

      MgCNi3 is a non-oxide perovskite which is both superconducting and ferromagnetic. Here MgCxNi3 is encapsulated in carbon nanoflasks via a chemical method. Magnetic susceptibility measurements indicate the occluded MgCNi3 exhibits a superconducting transition with a critical temperature of 7 K (see Figure).

    7. Supramolecular Photovoltaic Cells Using Porphyrin Dendrimers and Fullerene (pages 975–979)

      T. Hasobe, Y. Kashiwagi, M. A. Absalom, J. Sly, K. Hosomizu, M. J. Crossley, H. Imahori, P. V. Kamat and S. Fukuzumi

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200306519

      Organic photovoltaic cells made using supramolecular complexes of porphyrin dendrimers with fullerenes demonstrate remarkable enhancement in the photoelectrochemical performance as well as broader photoresponse in the visible and near-infrared regions relative to the reference system. This demonstrates that molecular assemblies of C60 and porphyrins with dendritic structures are effective in photoenergy conversion systems (see Figure).

    8. Ferroelectric, Electroactive, and Dielectric-Relaxation Behavior of Fluoropolymers (pages 979–982)

      C. Ang and Z. Yu

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200306036

      The discovery of piezoelectricity in poly(vinylidene fluoride) polymers and related co- and terpolymers has led to much interest in the physics of these materials because of their great potential for many actuator applications. The electroactive strain, ferroelectric polarization, and dielectric behavior of an irradiated poly(vinylidene fluoride–trifluoroethylene) (P(VDF–TrFE)) copolymer and non-irradiated poly(vinylidene fluoride–trifluoroethylene–chlorotrifluoroethylene) (P(VDF–TrFE–CTFE)) terpolymer are reported here, with special attention given to the analysis of the complex permittivity.

    9. Controllable Synthesis of Highly Luminescent and Monodisperse CdS Nanocrystals by a Two-Phase Approach under Mild Conditions (pages 982–985)

      D. Pan, S. Jiang, L. An and B. Jiang

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200400010

      Highly luminescent and monodisperse CdS nanocrystals (see Figure) have been synthesized using a two-phase approach. The synthesis of CdS nanocrystals at the liquid–liquid interface was easy, safe, and highly reproducible, and the reaction conditions were mild and controllable.

    10. Engineering Nanospaces: Iterative Synthesis of Melamine-Based Dendrimers on Amine-Functionalized SBA-15 Leading to Complex Hybrids with Controllable Chemistry and Porosity (pages 985–989)

      E. J. Acosta, C. S. Carr, E. E. Simanek and D. F. Shantz

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200306323

      A series of melamine-based dendrimers of various generations are grown directly off the surface of amine-functionalized SBA-15 (see Figure), demonstrating the feasibility of using functionalized mesoporous silica as a solid-phase support for organic–inorganic hybrid materials.

    11. Low-Temperature, Surface-Mediated Foaming of Polymer Films (pages 989–994)

      S. Siripurapu, J. M. DeSimone, S. A. Khan and R. J. Spontak

      Version of Record online: 3 JUN 2004 | DOI: 10.1002/adma.200306068

      Ultraporous thin polymer films (see Figure) are generated using physical constraints imposed by external surfaces (hard plates) and internal surfaces (hard nanoparticles and soft micelles) via foaming with supercritical CO2. The constraints serve as diffusion barriers and/or heterogeneous nucleation sites. Use of CO2-philic copolymers further enables microcellular foaming at reduced pressures with liquid CO2.

    12. Mercury(II) N,N′-Methyl-Phenylethyl-Dithiocarbamate and Its Use as a Precursor for the Room-Temperature Solution Deposition of β-HgS Thin Films (pages 994–996)

      M. Green, P. Prince, M. Gardener and J. Steed

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200306407

      Mercury(II) N,N′-methyl-phenylethyl-dithiocarbamate (Figure shows crystal structure) has been prepared and used as a room-temperature single-source precursor to a traditionally unstable phase of mercury sulfide.

    13. Amorphous Calcium Carbonate: Synthesis and Potential Intermediate in Biomineralization (pages 996–1000)

      M. Faatz, F. Gröhn and G. Wegner

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200306565

      Amorphous calcium carbonate is produced as spherical particles (see Figure) via in-situ generation of CO2 by hydrolysis of dialkyl carbonates in aqueous solution of CaCl2 at room temperature. This method of synthesis (precipitation) allows detailed studies of the particle formation process. Temperature-dependent results are rationalized in terms of a phase diagram that assumes a liquid–liquid immiscibility gap with a lower critical separation temperature.

    14. Light Amplification by Optical Excitation of a Chemical Defect in a Conjugated Polymer (pages 1001–1004)

      M. Vehse, B. Liu, L. Edman, G. C. Bazan and A J. Heeger

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200400170

      A small fraction of narrow-bandgap benzothiadiazole (BT) ‘defects’ covalently integrated into the main chain of a wide-bandgap polyfluorene (PF) polymer minimizes self-absorption effects via efficient energy transfer from absorbing PF segments to emitting BT ‘defects’. A threshold for amplified spontaneous emission in a glass/polymer/air optical waveguide as low as 15 kW cm–2 is achieved.

    15. Enhanced Sensitivity of a Gas Sensor Incorporating Single-Walled Carbon Nanotube–Polypyrrole Nanocomposites (pages 1005–1009)

      K. H. An, S. Y. Jeong, H. R. Hwang and Y. H. Lee

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200306176

      A nanocomposite of polypyrrole/carbon nanotubes prepared by in situ chemical polymerization shows improved conductivity of the polypyrrole as compared with its pure form. Its application as a chemical sensor, made using a simple spin-casting technique, shows a drastically increased sensitivity. The Figure shows a field-emission scanning electron microscopy (FE-SEM) image of the SWNT/Ppy nanocomposite.

    16. Efficient Hybrid Solar Cells from Zinc Oxide Nanoparticles and a Conjugated Polymer (pages 1009–1013)

      W. J. E. Beek, M. M. Wienk and R. A. J. Janssen

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200306659

      ZnO nanoparticles dispersed in a semiconducting polymer form the active layer of a solar cell (see Figure) that is able to convert up to 40 % of the incident photons at 500 nm into electrical current and has a power conversion efficiency of about 1.5 % in sunlight. Manufactured at low temperature using environmentally friendly materials, it represents a new step to ‘green electricity'.

    17. Dip-Pen Nanolithography of Chemical Templates on Silicon Oxide (pages 1013–1016)

      S. E. Kooi, L. A. Baker, P. E. Sheehan and L. J. Whitman

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200306468

      A flexible template strategy for the generation of nanometer-scale templates via dip-pen nanolithography is described. Trichlorosilanes are patterned with a chemically modified cantilever, and subsequently oxidized. The reactive template formed can be further modified by covalent attachment (e.g., of poly(ethylene imine), see Figure) or via electrostatic immobilization (e.g., of CdSe).

    18. In-Situ End-Group Functionalization of Regioregular Poly(3-alkylthiophene) Using the Grignard Metathesis Polymerization Method (pages 1017–1019)

      M. Jeffries-EL, G. Sauvé and R. D. McCullough

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200400137

      A facile one-step synthetic method to functionalize regioregular polythiophene is described (see Figure). End-group functionalization leads to a number of new uses for these polymers including end-group-driven self-assembly onto surfaces and into conducting polymer networks, and their use as building blocks for the synthesis of block copolymers.

    19. Hierarchical Structure: Silicon Nanowires Standing on Silica Microwires (pages 1019–1023)

      C. Ye, L. Zhang, X. Fang, Y. Wang, P. Yan and J. Zhao

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200306509

      A novel hierarchical structure, namely, single-crystalline Si nanowires standing on silica microwires (see Figure), has been prepared by adopting the disproportionation reaction of SiO with metal tin as a liquid-forming agent. The intense near-IR photoluminescence displayed by the hierarchical structures suggests possible applications in nanoscale optoelectronic devices.

    20. Micelle-Mediated Synthesis of Single-Crystalline Selenium Nanotubes (pages 1023–1026)

      Y. Ma, L. Qi, J. Ma and H. Cheng

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200400071

      The large-scale synthesis of single-crystal Se nanotubes (e.g., see Figure) has been realized via a novel micelle-mediated process, the key to which may be the use of micelles to control the distribution of amorphous Se in solution.