Advanced Materials

Cover image for Vol. 17 Issue 4

February, 2005

Volume 17, Issue 4

Pages 383–498

    1. Cover Picture: Colloidal Crystal Capillary Columns—Towards Optical Chromatography (Adv. Mater. 4/2005)

      U. Kamp, V. Kitaev, G. von Freymann, G. A. Ozin and S. A. Mabury

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200590019

      Colloidal crystal capillary columns (C4s; see cover) produced by pressure-assisted colloidal-microsphere assembly in capillaries (PACMAC) display a high degree of optical uniformity in the visible and near-IR spectral ranges and are able to spectroscopically differentiate alkanes by diffraction. The Figure shows sections of 180 nm (blue) and 225 nm diameter (green) polystyrene microsphere C4s, and the 225 nm diameter polystyrene microsphere C4 after infiltration with ethanol (yellow).

    2. Contents: Adv. Mater. 4/2005 (pages 383–391)

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200590015

    3. Fugitive Inks for Direct-Write Assembly of Three-Dimensional Microvascular Networks (pages 395–399)

      D. Therriault, R. F. Shepherd, S. R. White and J. A. Lewis

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200400481

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      Direct-write assembly of three- dimensional (3D) scaffolds that retain their shape during fabrication and subsequent infiltration with an epoxy matrix are made possible by a new fugitive ink based on a binary mixture of a microcrystalline wax and a lower molecular weight organic compound. Removal of the ink creates a 3D network of interconnected microchannels within the matrix (see Figure).

    4. Bioactive Hydrogels with an Ordered Cellular Structure Combine Interconnected Macroporosity and Robust Mechanical Properties (pages 399–403)

      A. N. Stachowiak, A. Bershteyn, E. Tzatzalos and D. J. Irvine

      Article first published online: 22 NOV 2004 | DOI: 10.1002/adma.200400507

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      A method for preparing porous hydrogel scaffolds suitable for bioengineering applications based on colloidal-crystal templating is demonstrated. Templated scaffolds are shown to have highly interconnected porosities at moderate void fractions due to their ordered arrangement of voids, and thus combine abundant pathways for cell migration (see Figure) and mass transport with compressive moduli comparable to soft tissues.

    5. Preparation of Fluorescent Silica Nanotubes and Their Application in Gene Delivery (pages 404–407)

      C.-C. Chen, Y.-C. Liu, C.-H. Wu, C.-C. Yeh, M.-T. Su and Y.-C. Wu

      Article first published online: 13 JAN 2005 | DOI: 10.1002/adma.200400966

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      Fluorescent silica nanotubes are synthesized through a sol–gel reaction using an anodic aluminum oxide membrane template. The nanotubes are filled with plasmid DNA encoding green fluorescence protein (GFP), which are incorporated into mammalian cells that subsequently express GFP (see Figure). The results demonstrate a novel application of nanotubes in biomolecule delivery.

    6. Self-Assembly and Electronics of Dipolar Linear Acenes (pages 407–412)

      Q. Miao, M. Lefenfeld, T.-Q. Nguyen, T. Siegrist, C. Kloc and C. Nuckolls

      Article first published online: 18 JAN 2005 | DOI: 10.1002/adma.200401251

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      Linear acenes terminated with quinones demonstrate that electrostatic complementarity is a viable self-assembly motif for organic semiconductors. An organic field-effect transistor with co-facial, head-to-tail stacks with π-surfaces 0.1 Å closer together than the aromatic planes of graphite is fabricated. The field-effect mobilities and ON/OFF current ratios are high enough to be useful in flexible electronic applications.

    7. Rapid Thermal Synthesis of Silver Nanoprisms with Chemically Tailorable Thickness (pages 412–415)

      G. S. Métraux and C. A. Mirkin

      Article first published online: 13 JAN 2005 | DOI: 10.1002/adma.200401086

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      Silver nanoprisms with a unimodal size distribution are synthesized through a novel thermal route that permits some control over nanoprism-edge length (see Figure). The influences of citrate, poly(vinylpyrrolidone), H2O2, and NaBH4 on the nanostructures are described. This protocol allows control over nanoprism thickness, an architectural parameter not accessible via known preparative methods for such structures.

    8. A Simple Route to Tunable Two-Dimensional Arrays of Quantum Dots (pages 415–418)

      J. Pacifico, D. Gómez and P. Mulvaney

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200400867

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      An innovative method of growing patterned, two-dimensional (2D) arrays of CdSe@ZnS quantum dots (QDs) is presented. Nanosphere lithography is used to generate hexagonally patterned metallic islands, followed by self-assembly of a monolayer of aminoethanethiol, which provides QD-anchoring groups. QD monolayers are then adsorbed onto the self-assembled monolayer. The simple method used for making the arrays permits scalable preparation of 2D-patterned QD arrays.

    9. Synthesis of Silicon Carbide Nanostructures via a Simplified Yajima Process—Reaction at the Vapor–Liquid Interface (pages 419–422)

      C.-H. Wang, Y.-H. Chang, M.-Y. Yen, C.-W. Peng, C.-Y. Lee and H.-T. Chiu

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200400939

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      A preceramic polymer route developed in 1975 has been simplified to efficiently generate β-SiC nanostructures, including cubic cages (see Figure), cubic shells, and nanoparticles. The nanostructures are generated by the reaction of liquid sodium with the vapors of methylchlorosilanes, with the morphology of the resulting nanostructures dependent upon the interactions between the phase-separated solid products generated at the interface of the vapor–liquid/solid reactions.

    10. Back-Side Electrical Contacts for Patterned Electrochromic Devices on Porous Substrates (pages 422–426)

      A. A. Argun, M. Berard, P.-H. Aubert and J. R. Reynolds

      Article first published online: 24 JAN 2005 | DOI: 10.1002/adma.200401353

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      Patterned electrodes on porous substrates, where the contacts to address these electrodes are hidden on the back of the substrates are described. To demonstrate the applicability of this method in fabricating organic electronic devices, a reflective-type polymer electrochromic device is constructed. A 7-pixel numerical-display device, showing the number “6” in the Figure, benefits from the color contrast between gold and a poly(3,4-propylenedioxythiophene) derivative.

    11. Controlled Growth of Se Nanoparticles on Ag Nanoparticles in Different Ratios (pages 426–429)

      X. Gao, L. Yu, R. MacCuspie and H. Matsui

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200400898

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      The integration of multiple nano- particles (NPs) with different physical properties into a multifunctional hybrid NP is a challenge. Here, a new wet chemical synthesis is used to generate hybrid NPs by the heterogeneous growth of one NP onto another equivalent-sized NP (see Figure). The hybrid NPs consist of Ag-NPs and Se-NPs in controlled nanoparticle ratios of 1:1, 1:2, and 1:3, respectively. The Se-NPs were grown on the Ag-NP, and the number of Se-NPs was controlled by the initial concentration of Se ions.

    12. Monodisperse Nanoparticles of Ni and NiO: Synthesis, Characterization, Self-Assembled Superlattices, and Catalytic Applications in the Suzuki Coupling Reaction (pages 429–434)

      J. Park, E. Kang, S. U. Son, H. M. Park, M. K. Lee, J. Kim, K. W. Kim, H.-J. Noh, J.-H. Park, C. J. Bae, J.-G. Park and T. Hyeon

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200400611

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      Monodisperse spherical Ni nanoparticles with diameters of 2 nm, 5 nm, and 7 nm were synthesized from the thermal decomposition of a Ni–oleylamine complex. Ni nanocrystal superlattices were generated via the controlled evaporation of solvent (see Figure). The nanoparticles were successfully used as catalysts for the Suzuki coupling reaction, and were readily oxidized to produce NiO nanoparticles.

    13. Functional Biomimetic Microlens Arrays with Integrated Pores (pages 435–438)

      S. Yang, G. Chen, M. Megens, C. K. Ullal, Y.-J. Han, R. Rapaport, E. L. Thomas and J. Aizenberg

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200401002

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      Synthetic, biomimetic microlens arrays with integrated pores are presented for the first time. Their appearance and function are strikingly similar to their biological prototype—a highly efficient optical element formed by brittlestars (see Figure; biological (left) and synthetic (right) lens arrays). The microlenses have a strong focusing ability, and light-absorbing liquids can be transported in and out of the pores between the lenses, allowing tunability of their optical properties over a wide range.

    14. Colloidal Crystal Capillary Columns—Towards Optical Chromatography (pages 438–443)

      U. Kamp, V. Kitaev, G. von Freymann, G. A. Ozin and S. A. Mabury

      Article first published online: 5 JAN 2005 | DOI: 10.1002/adma.200400020

      Thumbnail image of graphical abstract

      Colloidal crystal capillary columns (C4s; see cover) produced by pressure-assisted colloidal-microsphere assembly in capillaries (PACMAC) display a high degree of optical uniformity in the visible and near-IR spectral ranges and are able to spectroscopically differentiate alkanes by diffraction. The Figure shows sections of 180 nm (blue) and 225 nm diameter (green) polystyrene microsphere C4s, and the 225 nm diameter polystyrene microsphere C4 after infiltration with ethanol (yellow).

    15. Multiwalled Carbon Nanotube Actuators (pages 443–446)

      M. Hughes and G. M. Spinks

      Article first published online: 13 JAN 2005 | DOI: 10.1002/adma.200401076

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      Multiwalled carbon nanotube (MWNT) mats (see Figure) exhibit actuation strains of about 0.2 % without optimization, which compares favorably with those generally reported for single-walled carbon nanotube (SWNT) mats (0.06–0.2 %). Analysis of strain versus applied potential and strain versus nominal charge per carbon indicates that the mechanisms of actuation in the MWNT mats are similar to those in SWNT mats.

    16. Platinum Nanoclusters Studded in the Microporous Nanowalls of Ordered Mesoporous Carbon (pages 446–451)

      W. C. Choi, S. I. Woo, M. K. Jeon, J. M. Sohn, M. R. Kim and H. J. Jeon

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200400978

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      Methanol-tolerant cathode materials for use in direct-methanol fuel cells are composed of ordered mesoporous carbon with walls studded with ultrafine Pt nanoclusters. The material (see Figure), composed of PtC regularly interconnected nanocomposite arrays, is prepared by pyrolysis of carbon and platinum precursors in silica mesoporous templates such as SBA-15.

    17. Cap Closing of Thin Carbon Nanotubes (pages 451–455)

      N. de Jonge, M. Doytcheva, M. Allioux, M. Kaiser, S. A. M. Mentink, K. B. K. Teo, R. G. Lacerda and W. I. Milne

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200400266

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      Closing individual, thin, multiwalled carbon nanotubes is performed in situ in a transmission electron microscope (see Figure). The closure of the initially open end of the nanotube results from the presence of a strong electric field and the accompanied electron emission. The closed-cap nanotubes exhibit high current stability, which is of advantage for their use as electron sources.

    18. Non-Volatile Polymer Memory Device Based on a Novel Copolymer of N-Vinylcarbazole and Eu-Complexed Vinylbenzoate (pages 455–459)

      Q. Ling, Y. Song, S. J. Ding, C. Zhu, D. S. H. Chan, D.-L. Kwong, E.-T. Kang and K.-G. Neoh

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200401048

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      A polymer-memory device based on a copolymer containing carbazole (donor) and Eu-complex (acceptor) groups in a metal/insulator/metal architecture is described. The nonvolatile device has two distinctive bistable conductivity states, and exhibits a high ON/OFF current ratio, a fast response time, and acceptable retention under ambient conditions. Application of a potential sets the device to the high-conductivity ON state by generating holes (see Figure).

    19. Scanning-Tunneling-Microscopy Based Thermochemical Hole Burning on a New Charge-Transfer Complex and Its Potential for Data Storage (pages 459–464)

      H. L. Peng, C. B. Ran, X. C. Yu, R. Zhang and Z. F. Liu

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200401148

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      Ultrahigh-density data storage is realized using a thermochemical hole-burning technique based on scanning tunneling microscopy (STM). The heating effect induced by the STM current gives rise to localized thermochemical decomposition of an organic charge-transfer complex substrate and subsequent gasification of its low- boiling-point decomposition products. A large array of nanometer-sized holes is recorded on the substrate (see Figure).

    20. Photoconductivity of Single-Bilayer Nanotubes Consisting of Poly(p-phenylenevinylene) (PPV) and Carbonized-PPV Layers (pages 464–468)

      K. Kim, B. H. Kim, S.-H. Joo, J.-S. Park, J. Joo and J.-I. Jin

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200400977

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      Photoconducting nanotube devices consisting of a poly(p-phenylenevinylene) (PPV) layer and a carbonized-PPV layer (see Figure) show high photoconductivity efficiencies under illumination by a xenon lamp. This investigation demonstrates the first examples of photoconducting single-bilayer nanotube devices that can be operated over the UV-visible light wavelength range. The bilayer architecture could be useful in photoswitching applications and in nanometer-scale photovoltaic devices.

    21. Metallized Polyelectrolyte Microcapsules (pages 468–472)

      D. G. Shchukin, E. A. Ustinovich, G. B. Sukhorukov, H. Möhwald and D. V. Sviridov

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200401031

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      Hollow and filled Ni microspheres are fabricated by a photocatalytic approach using polyelectrolyte capsules as templates. Because of the different crystallization conditions existing in the capsule shell and the interior volume, Ni nanorods are formed inside the capsule, whereas only small, spherical Ni nanoparticles are obtained in the capsule shell (see Figure). The metallized polyelectrolyte shell is sensitive to the pH and possesses pH-controlled permeability.

    22. Monodisperse Spherical Colloids of Pb and Their Use as Chemical Templates to Produce Hollow Particles (pages 473–477)

      Y. Wang, L. Cai and Y. Xia

      Article first published online: 13 JAN 2005 | DOI: 10.1002/adma.200401416

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      Monodisperse Pb spherical colloids are synthesized by thermally decomposing lead acetate in boiling tetra(ethylene glycol), followed by quenching with cold ethanol. These colloids are then used as chemical templates to produce core–shell or hollow Pb@PbS (see Figure) and Pb@Ag particles by reacting with sulfur vapor and an aqueous AgNO3 solution, respectively.

    23. Fabrication and Characterization of Nanoporous Carbon/Silica Membranes (pages 477–483)

      H. B. Park and Y. M. Lee

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200400944

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      Nanoporous carbon/silica (C/SiO2) membranes (see Figure) with high permeabilities and high gas selectivities are prepared by the controlled pyrolysis of polyimide/silica (PI/SiO2) composites obtained from polymerization of alkoxysilanes in situ via a sol–gel reaction. The silica content and the nature of the silica network incorporated in the carbon matrix can be used to tune the gas permeation and separation properties of the final C/SiO2 membranes.

    24. Ductile Bulk Metallic Glass Foams (pages 484–486)

      A. H. Brothers and D. C. Dunand

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200400897

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      An open-cell fully amorphous metal foam (see Figure) with a bulk density ca. 1.5 g cm–3 (porosity ca. 78 %) is fabricated from the commercial glass-forming alloy Vit106 (Zr-5%Nb-15%Cu-13%Ni-10%Al, in at.-%), using the salt-replication technique. Despite the absence of significant plasticity in the monolithic alloy, the foamed alloy is ductile in compression and achieves engineering strains of 50 % without failure, giving it potential as a lightweight structural material or bone-replacement implant.

    25. Dual-Scale Porous Electrodes for Solid Oxide Fuel Cells from Polymer Foams (pages 487–491)

      Y. Zhang, S. Zha and M. Liu

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200400466

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      Porous nanostructured mixed-conducting materials with dual-scale porosities are fabricated using foam-like templates. The porous structures, as shown in the Figure, contain large pores (0.8–1.5 μm) for rapid gas transport and small pores (≈ 2.5 and 35 nm) for fast electrochemical reactions that require large surface areas. Thus, these electrode materials are ideally suited for electrochemical and catalytic applications, such as for solid oxide fuel cells.

    26. Enhanced Ferroelectric Properties of Nitrogen-Doped Bi4Ti3O12 Thin Films (pages 491–494)

      H. Irie, H. Saito, S. Ohkoshi and K. Hashimoto

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200400957

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      Ferroelectric nitrogen-doped Bi4Ti3O12 (BIT) and nitrogen-substituted BIT (N-BIT) thin films are prepared by an radiofrequency-magnetron-sputtering method such that nitrogen atoms are incorporated into oxygen sites. The remnant polarization Pr and the coercive field Ec of the nitrogen-doped BIT are enhanced relative to those of the undoped BIT (Figure). The leakage current of the nitrogen-doped BIT decreases and the fatigue properties improves compared to the undoped BIT.

    27. Book Review: Nanoparticles. By Günter Schmid (Ed.). (pages 495–496)

      Nicholas A. Kotov

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200590021

    28. Author Index and Subject Index Adv. Mater. 4/2005 (pages 497–498)

      Article first published online: 18 FEB 2005 | DOI: 10.1002/adma.200590018

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