Advanced Materials

Cover image for Vol. 17 Issue 3

February, 2005

Volume 17, Issue 3

Pages 255–378

    1. Cover Picture: Spontaneous Transformation of Stabilizer-Depleted Binary Semiconductor Nanoparticles into Selenium and Tellurium Nanowires (Adv. Mater. 3/2005)

      Z. Tang, Y. Wang, K. Sun and N. A. Kotov

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200590014

      Se and Te nanowires (NWs) are spontaneously formed in solution through chemical decomposition of stabilizer-depleted nanoparticles (NPs) in the presence of a strong complexing agent. Highly crystalline Se and Te NWs with monodisperse lateral sizes, in the range 10–100 nm, are produced (see Figure and cover). This work provides a new approach to nanoscale synthesis, which takes advantage of the transformation of NPs to NWs induced by stabilizer shell depletion and ensuing chemical reactions.

    2. Contents: Adv. Mater. 3/2005 (pages 255–264)

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200590010

    3. Fabrication of Multicolor-Encoded Microspheres by Tagging Semiconductor Nanocrystals to Hydrogel Spheres (pages 267–270)

      M. Kuang, D. Wang, H. Bao, M. Gao, H. Möhwald and M. Jiang

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400818

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      Single- or multicolor-encoded microspheres are created by confining water-soluble CdTe nanocrystals with different sizes within hydrogel microspheres of N-isopropylacrylamide and 4-vinylpyridine copolymer based on the pH-responsive swelling behavior of the gel (see Figure). The emission intensity level and color of the resulting fluorescent spheres can be manipulated simply by changing the concentrations of the different-sized NCs and their molar ratios.

    4. Synthesis of Skeletal-Structured Biporous Silicate Powders through Microcolloidal Crystal Templating (pages 270–273)

      C.-G. Oh, Y. Baek and S.-K. Ihm

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400192

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      Biporous silicates with both a MCM-41 mesophase and a skeletal macrophase (see Figure) are synthesized using a new and simple method. Transmission electron microscopy confirms the existence of both mesopores and macropores, and a model of the formation of skeletal macroporosity is proposed. The synthetic method could lead to larger-scale production of powdered biporous silicates.

    5. Water/Methanol-Soluble Conjugated Copolymer as an Electron-Transport Layer in Polymer Light-Emitting Diodes (pages 274–277)

      W. Ma, P. K. Iyer, X. Gong, B. Liu, D. Moses, G. C. Bazan and A. J. Heeger

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400963

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      Multilayer polymer light-emitting diodes are made using semiconducting polymers. An emissive polymer layer is cast from solution in an organic solvent, and a water-soluble (or methanol- soluble) conjugated copolymer is used for the electron transport layer (ETL) in the following device configuration: (indium tin oxide)/poly(3,4-ethylenedioxythiophene)/emissive polymer/ETL/Ba/Al. Devices with an ETL have significantly lower turn-on voltages, higher brightness values, and improved luminous efficiencies.

    6. Soluble Self-Aligned Carbon Nanotube/Polyaniline Composites (pages 278–281)

      R. Sainz, A. M. Benito, M. T. Martínez, J. F. Galindo, J. Sotres, A. M. Baró, B. Corraze, O. Chauvet and W. K. Maser

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400921

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      Polymerization of polyaniline in the presence of carbon nanotubes results in a soluble carbon nanotube/polyaniline composite (Figure, left) displaying enhanced thermal and electrical properties. Polyaniline in the proximity of nanotubes grows in a more planar conformation due to strong π–π interactions simultaneously stabilized by self-organization of the nanotubes, thus forming aligned bundles of micrometer lengths (Figure, right).

    7. SrZrO3 Nanopatterning Using Self-Organized SrRuO3 as a Template (pages 281–284)

      E. Vasco, S. Karthäuser, R. Dittmann, J.-Q. He, C.-L. Jia, K. Szot and R. Waser

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400718

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      Nanopatterned rippled films (see Figure) are produced by epitaxial growth of pulsed-laser deposited SrRuO3 on phototreated surfaces of vicinal SrTiO3 by self-organization in a step-flow inhibited regime. The as-deposited SrRuO3 films are used as nanoscale templates to fabricate arrays of epitaxial SrZrO3 dielectric nanowires.

    8. New Dopant and Host Materials for Blue-Light-Emitting Phosphorescent Organic Electroluminescent Devices (pages 285–289)

      S.-J. Yeh, M.-F. Wu, C.-T. Chen, Y.-H. Song, Y. Chi, M.-H. Ho, S.-F. Hsu and C. H. Chen

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200401373

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      Efficient organic light-emitting diodes (OLEDs) incorporating IrIII bis(4,6-difluorophenylpyridinato)-3-(trifluoromethyl)-5- (pyridin-2-yl)-1,2,4-triazolate (FIrtaz) and IrIII  bis(4,6-difluorophenylpyridinato)-5-(pyridin-2-yl)-1H-tetrazolate (FIrN4) demonstrate higher-purity blue-light emission than the long-known IrIII bis(4,6-difluorophenylpyridinato)picolate (FIrpic) phosphorophore. New host materials with higher glass-transition temperatures were also found to enhance the OLED performance.

    9. Microfabricated Deposition Nozzles for Direct-Write Assembly of Three-Dimensional Periodic Structures (pages 289–293)

      R. B. Rao, K. L. Krafcik, A. M. Morales and J. A. Lewis

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400514

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      Direct-write assembly of a three- dimensional periodic structure comprised of hexagonal filaments is demonstated. The structure is created by robotically depositing a concentrated colloidal gel-based ink through a cylindrical deposition nozzle modified by attaching a UV-LIGA (lithography, electroplating, and molding)-fabricated hexagonal micro (μ)-tip that controls filament geometry.

    10. From ZnO Colloids to Nanocrystalline Colored ZnxTiyOwzNz Spinel Films (pages 294–297)

      F. Grasset, G. Starukh, L. Spanhel, S. Ababou-Girard, D.-S. Su and A. Klein

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400031

      A new class of colored heterometallic ZnxTiyOwzNz waveguides developed using a nanocolloidal sol–gel route combined with thermal treatment under ammonia atmosphere is reported. The resulting mesoporous layers are photostable and degrade the cationic pigment methylene blue under visible light irradiation. Semiconductor photocatalysis is currently being explored in environmental sciences, solar cell technologies, and preparative “green” technology.

    11. Polymer-Supported Anisotropic Submicrometer-Patterned Electrodes for Displays (pages 297–301)

      M. Misaki, M. Chikamatsu, N. Tanigaki, M. Yamashita, Y. Ueda and K. Yase

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200401045

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      An anisotropic electrode that exhibits one-dimensional conductivity is readily fabricated from self-organized metal deposition onto friction-transferred poly(tetrafluoroethylene) (PTFE) films. An organic electroluminescent device was constructed on the anisotropic electrode (see Figure), and the emitting area can be easily adjusted by varying the contact width of the silver paste applied subsequently on the electrode.

    12. Self-Assembled Nanofibers from Random Silicate Platelets (pages 301–304)

      J.-J. Lin, C.-C. Chu, C.-C. Chou and F.-S. Shieu

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400154

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      Fibrous materials of lengths up to 10 μm are obtained from the self-assembly of random silicate platelets. Under transmission electron microscopy electron-beam bombardment, a fiber of stacked platelets was further transformed into a tube-like arrangement (see Figure), conceptually shown in the inset.

    13. Patterning a Poly(3,4-ethylenedioxythiophene) Thin Film Using a Liquid Crystalline Network (pages 305–309)

      O. Catanescu and L.-C. Chien

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400332

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      Polymerization and patterning of a conductive polymer thin film via a new approach involving a well-ordered polymer matrix previously obtained using a liquid-crystalline template is reported here. The resulting conductive polymer (PEDOT, poly(3,4-ethylenedioxythiophene)) was shown by scanning electron microscopy (SEM) to be very well aligned at a submicrometer level (see Figure).

    14. A Novel Photoresponsive π-Conjugated Polymer Based on Diarylethene and its Photoswitching Effect in Electrical Conductivity (pages 309–314)

      T. Kawai, Y. Nakashima and M. Irie

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400191

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      Photochromic conductivity modulation of conjugated polymers containing a diarylethene unit with high photochromic conversion ratios is described. The electrical conductivity can be switched quasi-reversibly from the bleached low-conductivity state (Figure, left) and the blue high-conductivity state (right) by alternate irradiation with visible and UV light, and may lead to applications in photon-mode molecular memory devices.

    15. Enzymatic Synthesis and Nanostructural Control of Gallium Oxide at Low Temperature (pages 314–318)

      D. Kisailus, J. H. Choi, J. C. Weaver, W. Yang and D. E. Morse

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400815

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      Nanostructural control of gallium oxide formation is achieved at low temperatures by the enzyme-catalyzed hydrolysis and polycondensation of gallium oxide precursors. Filaments of silicatein, a hydrolase originally discovered in a marine sponge, catalyze the hydrolysis of gallium(III) nitrate, producing oriented nanocrystallites along the length of the filaments (see Figure) in the absence of acid or alkali.

    16. pH-Triggered Thermally Responsive Polymer Core–Shell Nanoparticles for Drug Delivery (pages 318–323)

      K. S. Soppimath, D. C.-W. Tan and Y.-Y. Yang

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200401057

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      Novel polymer core–shell nanoparticles that exhibited a pH-dependent lower critical solution temperature (LCST) have been synthesized. The nanoparticles displayed stable structure in a nominal physiological environment but deformed and precipitated in an acidic environment, thereby releasing the enclosed drug molecules (see Figure). The nanoparticles would make a promising carrier for targeting drugs to tumor tissues or cell interiors where the environment is characteristically acidic.

    17. Rapid Functionalization of Mesoporous Materials: Directly Dispersing Metal Oxides into As-Prepared SBA-15 Occluded with Template (pages 323–327)

      Y. M. Wang, Z. Y. Wu, L. Y. Shi and J. H. Zhu

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400860

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      Guest–host composites with improved dispersion of guest species can be fabricated using a new method that exploits the confined space between the silica walls and templated aggregates in as-prepared mesoporous materials. This produces mesoporous functional composites with high oxide dispersions with potential applications such as supported catalysts or solid-polymer electrolytes.

    18. Three-Dimensional Bioactive and Biodegradable Scaffolds Fabricated by Surface-Selective Laser Sintering (pages 327–330)

      E. N. Antonov, V. N. Bagratashvili, M. J. Whitaker, J. J. A. Barry, K. M. Shakesheff, A. N. Konovalov, V. K. Popov and S. M. Howdle

      Version of Record online: 20 DEC 2004 | DOI: 10.1002/adma.200400838

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      Surface-selective laser sintering (SSLS) has been developed for fabrication of three-dimensional polymer composite scaffolds with precise dimensions and intricate structure (see Figure), which are bioactive and biodegradable. SSLS allows sintering of polymer powders by melting only the surface layers of particles, which prevents overheating of internal domains, allowing incorporation of bioactive molecules into the structures.

    19. Work Function Independent Hole-Injection Barriers Between Pentacene and Conducting Polymers (pages 330–335)

      N. Koch, A. Elschner, J. P. Rabe and R. L. Johnson

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400697

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      The energy level alignment (see Figure) at interfaces between pentacene and thin films of conducting polymers (made from ethylenedioxythiophene and sulfonate moieties) is found to be independent of initial polymer work function or morphology. Interfacial chemical reactions control the energy level alignment, rather than just the pristine substrate work function.

    20. J-Aggregated Dye–MnPS3 Hybrid Nanoparticles with Giant Quadratic Optical Nonlinearity (pages 335–338)

      T. Yi, R. Clément, C. Haut, L. Catala, T. Gacoin, N. Tancrez, I. Ledoux and J. Zyss

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400583

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      Giant second-order hyperpolarizability (β) values are exhibited by dispersible, hybrid organic–inorganic nanoparticles comprising about one thousand push–pull molecules intercalated between layered MnPS3 nanoslabs. Enhancement of β is due to the parallel, ferroelectric-like arrangement of the chromophores within each nanoparticle. The chromophores spontaneously line up because they self-assemble as extended J-aggregates.

    21. CoNi Nanowires Synthesized by Heterogeneous Nucleation in Liquid Polyol (pages 338–344)

      D. Ung, G. Viau, C. Ricolleau, F. Warmont, P. Gredin and F. Fiévet

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400915

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      Magnetic cobalt/nickel nanowires with high coercivity at room temperature have been prepared by reduction in liquid polyol using heterogeneous nucleation. Anisotropic growth is controlled by a high number of ruthenium seeds and an appropriate sodium hydroxide concentration. Growth occurs preferentially along the c-axis for low sodium hydroxide concentrations, giving wires (see Figure), and platelets perpendicular to the c-axis at high concentrations.

    22. Biomorphic Cellular SiSiC/Zeolite Ceramic Composites: From Rattan Palm to Bioinspired Structured Monoliths for Catalysis and Sorption (pages 344–349)

      A. Zampieri, H. Sieber, T. Selvam, G. T. P. Mabande, W. Schwieger, F. Scheffler, M. Scheffler and P. Greil

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400672

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      The three-step manufacturing of bioinspired SiSiC/zeolite monoliths starting from native rattan stems is presented. Rattan-derived cellular SiSiC ceramics are prepared via a biotemplating liquid silicon infiltration process. MFI-type zeolite crystals are directly grown onto the ceramic substrate. SiSiC/zeolite composites (see Figure) possess hierarchical multimodal (micro-/macro-) porosity, biomorphous anatomy, unique architecture, and outstanding mechanical/thermal stability.

    23. New Iridium Complexes with Cyclometalated Alkenylquinoline Ligands as Highly Efficient Saturated Red-Light Emitters for Organic Light-Emitting Diodes (pages 349–353)

      D. K. Rayabarapu, B. M. J. S. Paulose, J.-P. Duan and C.-H. Cheng

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400813

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      Electroluminescent devices using new iridium complexes (see Figure) (PEQ)2Ir(acetylacetonate (acac)), (MPEQ)2Ir(acac), and (PEIQ)2Ir(acac), as dopant emitters give saturated red light with very high brightness and efficiencies. For example, a (PEQ)2- Ir(acac)-based device showed Commission Internationale de L'Eclairage (CIE) coordinates (0.66, 0.33), brightness, and external quantum efficiency of 26400 cd m–2 and 7.23 %, respectively.

    24. Electrochemical Logic Circuits (pages 353–358)

      D. Nilsson, N. Robinson, M. Berggren and R. Forchheimer

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200401273

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      Three-terminal electrochemical transistors are manufactured from thin films of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid), and form the basis of oscillatory and digital circuits, thus opening the door for logic systems based on \(electronic paper\). The transistors use ions and electrons as signal carriers, and operate at low voltages. Such low-cost digital circuitry may allow the use of electronics in systems and materials where it has been previously unused.

    25. Spontaneous Transformation of Stabilizer-Depleted Binary Semiconductor Nanoparticles into Selenium and Tellurium Nanowires (pages 358–363)

      Z. Tang, Y. Wang, K. Sun and N. A. Kotov

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400894

      Thumbnail image of graphical abstract

      Se and Te nanowires (NWs) are spontaneously formed in solution through chemical decomposition of stabilizer-depleted nanoparticles (NPs) in the presence of a strong complexing agent. Highly crystalline Se and Te NWs with monodisperse lateral sizes, in the range 10–100 nm, are produced (see Figure and cover). This work provides a new approach to nanoscale synthesis, which takes advantage of the transformation of NPs to NWs induced by stabilizer shell depletion and ensuing chemical reactions.

    26. Novel Nanostructured Polymeric Composites of Polycaprolactone and Ultra-High Molecular Weight Polyethylene via a Supercritical-Fluid Route (pages 364–367)

      A. J. Busby, J. Zhang, C. J. Roberts, E. Lester and S. M. Howdle

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400297

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      A supercritical-fluid process for creating blends of ultra-high-molecular-weight polyethylene and biodegradable polycaprolactone is described. These are unobtainable by conventional blending methods or solvents. Spherical crystallites of polycaprolactone (see Figure, light-colored circles) are observable in the blend embedded in the polyethylene matrix (darker background).

    27. Nanoscale Architecture of Metal-Oxide-Pillared Clays using Supercritical CO2 (pages 367–369)

      S. Yoda, Y. Nagashima, A. Endo, T. Miyata, H. Yanagishita, K. Otake and T. Tsuchiya

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400469

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      The fabrication of metal-oxide-pillared clay by a simple, environmentally friendly method is reported. The interlayer space within the clay (vermiculite, VMT) is first modified, followed by the intercalation of metal alkoxides dissolved in supercritical CO2 (see Figure), which are then hydrolyzed. Large electrostatic charges on VMT help resist delamination during intercalation and maintain ordered structures after calcination. Basal spacing and porosity are controllable by the intercalation time.

    28. Dual-Mode Switching of Diffraction Gratings Based on Azobenzene- Polymer-Stabilized Liquid Crystals (pages 370–374)

      X. Tong, G. Wang, A. Yavrian, T. Galstian and Y. Zhao

      Version of Record online: 4 FEB 2005 | DOI: 10.1002/adma.200400794

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      Dual-mode switching of diffraction efficiencies, using either light or an electric field, is possible with a diffraction grating prepared from an azobenzene-polymer-stabilized liquid crystal. Light-induced switching resulted from the cis–trans photoisomerization of the azobenzene unit, resulting in the nematic-to-isotropic phase transition of the liquid crystal (dark fringes in the Figure). This switching behavior is reversible and repeatable for many cycles.

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