Advanced Materials

Cover image for Vol. 17 Issue 18

September, 2005

Volume 17, Issue 18

Pages 2155–2266

    1. Cover Picture: Crosslinked Nanoparticle Stripes and Hexagonal Networks Obtained via Selective Patterning of Block Copolymer Thin Films (Adv. Mater. 18/2005)

      R. Shenhar, E. Jeoung, S. Srivastava, T. B. Norsten and V. M. Rotello

      Version of Record online: 6 SEP 2005 | DOI: 10.1002/adma.200590094

      Robust arrays of ordered nanoparticles (see Figure and cover) have been created by combining two self-assembly strategies: microphase separation of block copolymers and coordination chemistry. Thin films of a microphase-separated block copolymer serve as templates for patterning of terpyridine-functionalized gold nanoparticles. Subsequent treatment with iron salts crosslinks the patterned nanoparticles via the formation of iron–terpyridine complexes.

    2. Synthesis and Characterization of Fluorescent, Radio-Opaque, and Paramagnetic Silica Nanoparticles for Multimodal Bioimaging Applications (pages 2165–2169)

      S. Santra, R. P. Bagwe, D. Dutta, J. T. Stanley, G. A. Walter, W. Tan, B. M. Moudgil and R. A. Mericle

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200500018

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      Fluorescent, radio-opaque, and paramagnetic silica nanoparticles 100 ± 10 nm in size are developed by incorporating fluorescent tris(2,2′-bipyridyl) dichlororuthenium(II) hexahydrate and paramagnetic gadolinium ions. The nanoparticles are radio-opaque due to the presence of electron-dense Ru and Gd atoms. It is estimated that each nanoparticle carries about 16 000 Gd3+ ions. The multimodality of the silica nanoparticles is shown by fluorescence (Figure, left) and X-ray (right) imaging.

    3. Crystalline Thin Film of a Donor- Substituted Cyanoethynylethene for Nanoscale Data Recording Through Intermolecular Charge-Transfer Interactions (pages 2170–2173)

      G. Jiang, T. Michinobu, W. Yuan, M. Feng, Y. Wen, S. Du, H. Gao, L. Jiang, Y. Song, F. Diederich and D. Zhu

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200500559

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      Nanoscale data recording on high- quality crystalline thin films of N,N- dimethylanilino donor-substituted tricyanoethynylethene acceptors has been achieved by scanning tunneling microscopy with a storage density of about 1013 bits cm–2 (see Figure). The recording is based on an electric-field-induced intermolecular charge-transfer mechanism, which is strongly influenced by the ordered, antiparallel packing mode of the dipolar donor–acceptor molecules in the film.

    4. Alignment of Gold Nanorods in Polymer Composites and on Polymer Surfaces (pages 2173–2177)

      C. J. Murphy and C. J. Orendorff

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200501042

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      Alignment of gold nanorods incorporated into bulk polymers and imprinted at polymer surfaces by mechanical stretching is presented. Alignment of aspect-ratio-4.4 and -16 nanorods along the stretch direction is determined using polarized absorption spectroscopy, Rayleigh light scattering, and AFM (see Figure). Polymer film stretching is shown to be a simple approach to controlling nanorod orientation on surfaces and within bulk polymeric materials.

    5. Welded Electrochromic Conductive Polymer Nanofibers by Electrostatic Spinning (pages 2177–2180)

      S.-Y. Jang, V. Seshadri, M.-S. Khil, A. Kumar, M. Marquez, P. T. Mather and G. A. Sotzing

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200500577

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      Welded conducting polymer nanofibers (see Figure) with rapid electrochromic switching speeds have been prepared by electrospinning a soluble precursor polymer with pendant heterocycles into nanofibers which are subsequently crosslinked via solid-state oxidative crosslinking. The switching speeds between the oxidized and neutral states for these nanofiber mats is about twenty times faster than electrochemically prepared conducting polymer films.

    6. All-Solution-Processed n-Type Organic Transistors Using a Spinning Metal Process (pages 2180–2184)

      T.-W. Lee, Y. Byun, B.-W. Koo, I.-N. Kang, Y.-Y. Lyu, C. H. Lee, L. Pu and S. Y. Lee

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200401672

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      An all-solution-processed n-type transistor of soluble fullerene derivatives, based on a photosensitive organic silver precursor route to deposit source and drain metal electrodes, is reported (see Figure). The field-effect mobility of such devices is strongly dependent on the morphology of the spin-cast semiconducting thin film. The devices fabricated in this manner show a higher electron mobility than devices fabricated by vacuum-shadow deposition.

    7. Enhancement of Surface-Relief Gratings Recorded on Amphiphilic Liquid-Crystalline Diblock Copolymer by Nanoscale Phase Separation (pages 2184–2188)

      H. Yu, K. Okano, A. Shishido, T. Ikeda, K. Kamata, M. Komura and T. Iyoda

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200500346

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      An amphiphilic liquid-crystalline diblock copolymer can be used to record both refractive-index and surface-relief holographic gratings upon irradiation by two coherent laser beams. The diffraction behavior of the gratings is controlled by nanoscale phase separation on annealing. Surface relief is enhanced by almost an order of magnitude due to the pressure gradient produced in the process. The Figure shows a schematic of a grating structure before and after annealing.

    8. Synthesis and Characterization of L10 FePt Nanoparticles from Pt(Au, Ag)/γ-Fe2O3 Core–Shell Nanoparticles (pages 2188–2192)

      V. Tzitzios, D. Niarchos, G. Hadjipanayis, E. Devlin and D. Petridis

      Version of Record online: 3 AUG 2005 | DOI: 10.1002/adma.200500365

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      L10 FePt nanoparticles have been prepared from Pt(Ag)/γ-Fe2O3 and Pt(Au)/γ-Fe2O3 core/shell nanoparticles (see Figure). Addition of Ag reduces the fcc-to-L10 transformation temperature by 100–150 °C, while addition of Au causes a reduction of more than 150 °C compared with pure FePt nanoparticles. Annealing at 400 °C reveals a coercivity of 2.9 kOe for the Ag and 6 kOe for the Au-doped FePt nanoparticles.

    9. Highly Efficient Direct Current Electrodeposition of Single-Walled Carbon Nanotubes in Anhydrous Solvents (pages 2192–2194)

      Y. Abe, R. Tomuro and M. Sano

      Version of Record online: 16 AUG 2005 | DOI: 10.1002/adma.200501148

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      Uniform single-walled carbon nanotube films are fabricated by a DC electrodeposition technique from a dispersion solution of the nanotubes in dry organic solvents. Thick and shiny or thin and see-through, tightly bound films are formed on various substrates (see Figure). Highly efficient deposition is made possible by eliminating water from the dispersion solvent.

    10. Composition and Shape Control of Crystalline Ca1–xSrxTiO3 Perovskite Nanoparticles (pages 2194–2199)

      Y. Mao and S. S. Wong

      Version of Record online: 3 AUG 2005 | DOI: 10.1002/adma.200500437

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      A series of crystalline perovskite nanoparticles (Ca1–xSrxTiO3, 0 ≤ x ≤ 1, see Figure) has been prepared using a simple, scaleable, molten-salt synthesis method. The generated nanoparticles change from cubes to quasispheres with decreasing x values. Typical nanoparticles have sizes between 70 and 110 nm, irrespective of the Sr or Ca content. The strategy is applicable to the nanoscale growth of other complex oxide materials that exhibit interesting electronic and optical phenomena.

    11. Hydrogel-Supported Optical-Microcavity Sensors (pages 2199–2203)

      L. A. DeLouise, P. M. Fauchet, B. L. Miller and A. A. Pentland

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200500261

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      A porous-silicon microcavity membrane sensor maintains good sensitivity (see Figure) and shows long-term stability when embedded in a hydrogel matrix. The microcavity is sensitive to a 104–10–3 change in refractive index and can detect the binding of small molecules, proteins, etc., when they cause a sufficient change in the matrix porosity. This work represents a significant step towards realizing a “smart bandage” concept for wound-care management.

    12. Three-Dimensional Imaging of Semicrystalline Polypropylene with 10 nm Resolution (pages 2203–2206)

      N. Rehse, S. Marr, S. Scherdel and R. Magerle

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200401473

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      The 3D microstructure of elastomeric polypropylene has been imaged in real-space using nanotomography (see Figure). The method is improved by image-registration techniques which allow high-resolution volume images of large areas to be obtained. These images reveal the complex spatial arrangement of individual crystallites with 10 nm resolution, and promise better understanding of the structure–property relationship in this class of materials.

    13. Crosslinked Nanoparticle Stripes and Hexagonal Networks Obtained via Selective Patterning of Block Copolymer Thin Films (pages 2206–2210)

      R. Shenhar, E. Jeoung, S. Srivastava, T. B. Norsten and V. M. Rotello

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adma.200500624

      Thumbnail image of graphical abstract

      Robust arrays of ordered nanoparticles (see Figure and cover) have been created by combining two self-assembly strategies: microphase separation of block copolymers and coordination chemistry. Thin films of a microphase-separated block copolymer serve as templates for patterning of terpyridine-functionalized gold nanoparticles. Subsequent treatment with iron salts crosslinks the patterned nanoparticles via the formation of iron–terpyridine complexes.

    14. Organic Solvent Vapor Detection Using Holographic Photopolymer Reflection Gratings (pages 2211–2214)

      V. K. S. Hsiao, W. D. Kirkey, F. Chen, A. N. Cartwright, P. N. Prasad and T. J. Bunning

      Version of Record online: 16 AUG 2005 | DOI: 10.1002/adma.200401888

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      Porous polymer colorimetric vapor- sensing elements have been produced using a holographic interferometry technique. Acetone vapor is detected by the change in the peak reflective wavelength of the resulting photonic bandgap structures (see Figure). The transmission electron microscopy image (Figure, inset) shows the voids generated in the film by adding a non-reactive solvent to the prepolymer syrup.

    15. Silicate Glasses with Unprecedented High Nitrogen and Electropositive Metal Contents Obtained by Using Metals as Precursors (pages 2214–2216)

      A. S. Hakeem, R. Daucé, E. Leonova, M. Edén, Z. Shen, J. Grins and S. Esmaeilzadeh

      Version of Record online: 3 AUG 2005 | DOI: 10.1002/adma.200500715

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      Oxonitridosilicate glasses, with high contents of nitrogen and electropositive metals, have been prepared by a novel synthesis route using metals as precursors (see Figure). They demonstrate high refractive indices, up to 2.30, and Vickers hardness values, up to 13.3 GPa, which are the highest values reported for any silicate glass. They constitute a significant extension of silicate glass compositions and are chemically flexible.

    16. Stable Amorphous CaCO3 Microparticles with Hollow Spherical Superstructures Stabilized by Phytic Acid (pages 2217–2221)

      A.-W. Xu, Q. Yu, W.-F. Dong, M. Antonietti and H. Cölfen

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200500747

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      Amorphous CaCO3 (ACC) is stabilized by the presence of phytic acid, a natural inositol hexakisphosphate (IP6). Micrometer-sized hollow spheres of ACC have been obtained (see Figure). The spheres are stable for at least three months in solution, which is equivalent to that described for more complex special biopolymers in biomineralization processes, and by far exceeds the previously known stability of ACC prepared in the presence of synthetic molecules.

    17. Fabrication of Polyimide-Blend Thin Films Containing Uniformly Oriented Silver Nanorods and Their Use as Flexible, Linear Polarizers (pages 2221–2224)

      S. Matsuda, Y. Yasuda and S. Ando

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adma.200500655

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      Fully aromatic polyimide films containing uniformly oriented Ag nanorods (see Figure) have been prepared by a simple method consisting of thermal curing and uniaxial drawing of submicrometer-scale phase-separated polyimide-blend films containing dissolved AgNO3. The films exhibit outstanding optical dichroism, over 20 dB (see inset), in the near-IR region due to the high aspect ratio of the nanorods and the high transparency of the matrix.

    18. Magnetocapacitance and Magnetoresistance Near Room Temperature in a Ferromagnetic Semiconductor: La2NiMnO6 (pages 2225–2227)

      N. S. Rogado, J. Li, A. W. Sleight and M. A. Subramanian

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adma.200500737

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      Neutron diffraction studies confirm that La2NiMnO6 is ferromagnetic with moments on Ni and Mn indicating NiII and MnIV (small and large spheres, respectively, in Figure). Electrical resistivity measurements show semiconducting behavior with a room temperature conductivity of ∼102 Ω cm and very high resistivity at low temperature. On application of a magnetic field, significant changes in electrical resistivity and dielectric constant occur at temperatures as high as 280 K.

    19. Periodical Gratings in Mixed-Oxide Films by Laser-Interference Irradiation (pages 2228–2232)

      A. Lasagni, M. Seyler, C. Holzapfel, W. F. Maier and F. Mücklich

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200402074

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      Laser-interference structuring of sol–gel films without organic photopolymerization provides a single-step method for the production of periodic surface structures (see Figure) in titania–silica mixed-oxide films. The dependency of the structure depth and homogeneity, measured by white-light interferometry, on process parameters such as laser fluence and number of laser pulses has been evaluated. A mechanism for structure formation is proposed.

    20. Enhanced Chemical Ordering and Coercivity in FePt Alloy Nanoparticles by Sb-Doping (pages 2233–2237)

      Q. Yan, T. Kim, A. Purkayastha, P. G. Ganesan, M. Shima and G. Ramanath

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200500949

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      Sb doping stabilizes the chemically ordered tetragonal L10 structure in FePt alloy nanoparticles, yielding higher coercivities (Hc) at lower annealing temperatures (see Figure) than previously reported. Upon annealing to ∼ 300 °C, nanoparticles yield coercivities more than ten times those previously reported for FePt nanoparticles of similar sizes annealed to the same temperature. These findings are of importance for ultrahigh-density memory device applications.

    21. Porous Nanoparticle Membranes: Synthesis and Application as Fuel-Cell Catalysts (pages 2237–2241)

      X. W. Teng, X. Y. Liang, S. Rahman and H. Yang

      Version of Record online: 3 AUG 2005 | DOI: 10.1002/adma.200500614

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      Nanoporous membranes of magnetic Fe2O3 and catalytic Pt nanoparticles are made using anodized aluminum oxide porous substrates as sacrificial templates. Langmuir–Blodgett (LB) deposition is used to make single-layered films (the Figure shows a Fe2O3 nanoparticle membrane after removal of the stabilizing surfactant).

    22. Fabrication of Metal Nanohole Arrays with High Aspect Ratios Using Two-Step Replication of Anodic Porous Alumina (pages 2241–2243)

      T. Yanagishita, K. Nishio and H. Masuda

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200500249

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      Metal nanohole arrays with straight holes of high aspect ratio have been fabricated using a new replication process based on the preparation of polymer pillars, both sides of which are supported and can therefore be maintained upright. These nanopillar arrays are demonstrated as negatives for the preparation of metal (Ni) nanohole arrays (see Figure).

    23. Spontaneous Formation of Macroporous Monoliths of Mesoporous Manganese Oxide Crystals (pages 2244–2246)

      E. S. Toberer and R. Seshadri

      Version of Record online: 3 AUG 2005 | DOI: 10.1002/adma.200500668

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      An unusual route to hierarchically porous MnO monoliths is demonstrated. The monoliths are obtained by successive stages of liquid- and vapor-phase leaching. The accompanying Figure shows 10–30 nm sized pores created by the conversion of zinc manganese oxide to manganese oxide. The leaching methodology is general and can be extended to the preparation of a number of porous inorganics.

    24. Long-Lived Photoinduced Charge Separation Inside Polarity Gradient Capsules (pages 2247–2249)

      L. Li, H. Möhwald, C. Spitz, D. von Seggern, M. Mucke and R. Menzel

      Version of Record online: 8 AUG 2005 | DOI: 10.1002/adma.200500576

      Hollow capsules with polarity gradients can be built up by a layer-by-layer technique. After laser excitation, long-lived charge separation was observed. Time-dependent measurements, observing the decay of pyrene cation and anion absorption, show that the sample configuration has an influence that can be ascribed to the polarity gradient The charge separation can therefore be predicted due to the establishment of the polarity gradient over nanometer dimensions.

    25. Interpenetrating-Lattice-Structured Magnets Exhibiting Anomalous Magnetic Properties (pages 2251–2254)

      J. S. Miller, T. E. Vos and W. W. Shum

      Version of Record online: 16 AUG 2005 | DOI: 10.1002/adma.200501219

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      3D [Ru2(O2CMe)4]3[Cr(CN)6] made from water has two interpenetrating lattices and exhibits anomalous magnetic behavior with respect to the material prepared from acetonitrile or 2D [Ru2(O2CBut)4]3-[Cr(CN)6]·2 H2O made from water (see Figure). These unexpected properties are attributed to the interpenetrating lattices and illustrate that, albeit rare, interpenetrating-lattice-structured materials can stabilize new cooperative magnetic behavior.

    26. Gold Nanocages: Engineering Their Structure for Biomedical Applications (pages 2255–2261)

      J. Chen, B. Wiley, Z.-Y. Li, D. Campbell, F. Saeki, H. Cang, L. Au, J. Lee, X. Li and Y. Xia

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adma.200500833

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      Hollow Au nanostructures (see Figure) have been synthesized by the galvanic replacement reaction between a Ag template and HAuCl4 so that their surface plasmon resonance peaks can be continuously tuned from 400 to 1200 nm. The Au nanostructures, with extraordinarily large cross-sections for both absorption and scattering, are expected to find uses as both contrast agents for optical imaging in early-stage tumor detection and as therapeutic agents for photothermal cancer treatment.

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