Advanced Materials

Cover image for Vol. 17 Issue 5

March, 2005

Volume 17, Issue 5

Pages 503–642

    1. Cover Picture: Dendritic Nanowire Growth Mediated by a Self-Assembled Catalyst (Adv. Mater. 5/2005)

      S. J. May, J.-G. Zheng, B. W. Wessels and L. J. Lauhon

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200590026

      Dendritic growth of multiply branched InAs nanowires (see Figure and cover) is initiated by the controlled introduction of a Mn precursor in the context of vapor–liquid–solid nanowire growth by chemical vapor deposition. Self-assembly of Mn clusters leads to the nucleation and epitaxial growth of Mn-terminated InAs branches. The results provide a new route to the formation of hierarchical nanowire structures for nanoscale electronics and photonics.

    2. Inside Front Cover: Topological Transformation of Vesicular Mesostructured Silica (Adv. Mater. 5/2005)

      B. Wang, W. Shan, Y. Zhang, J. Xia, W. Yang, Z. Gao and Y. Tang

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200590027

      The micrometer-scale self-assembly behaviour of MCM-41-type mesostructured silica is revealed through the study of a family of vesicular mesostructured silica with topology genus from 1 to 0 (see Figure and inside cover). The topological transformation and assembly kinetics demonstrate that the formation of the vesicular structure is closely correlated with the properties of the cetyltrimethylammonium–silicate building block and the hydrophobic nature of the ester additive.

    3. Contents: Adv. Mater. 5/2005 (pages 503–513)

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200590022

    4. Infrared Quantum Dots (pages 515–522)

      E. H. Sargent

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401552

      Thumbnail image of graphical abstract

      Infrared-active quantum dots are the subject of growing interest due to their unique properties and breadth of potential applications. In this progress report, the optimization of application-oriented performance in infrared optoelectronic devices based on solution-processed colloidal quantum dots is reviewed, with a focus on electroluminescence, photoconduction, photovoltaics, photoluminescence, electro-optic modulation, and optical gain (see Figure).

    5. Effect of Nanoparticle Mobility on Toughness of Polymer Nanocomposites (pages 525–528)

      D. Shah, P. Maiti, D. D. Jiang, C. A. Batt and E. P. Giannelis

      Version of Record online: 24 JAN 2005 | DOI: 10.1002/adma.200400984

      Thumbnail image of graphical abstract

      Nanoparticle orientation and alignment under tensile stress results in enhanced toughness in nanocomposite materials. This energy-dissipation mechanism, which is not observed in conventional polymer composites, is applicable to both semicrystalline and amorphous polymer-composite systems. The mechanism depends on the mobility of the nanoparticles in the matrix, as shown in the Figure before (left) and after (right) stretching.

    6. A Nanostructured Porous Silicon Near Insulator Becomes Either a p- or an n-Type Semiconductor upon Gas Adsorption (pages 528–531)

      E. Garrone, F. Geobaldo, P. Rivolo, G. Amato, L. Boarino, M. Chiesa, E. Giamello, R. Gobetto, P. Ugliengo and A. Viale

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401200

      Thumbnail image of graphical abstract

      Mesoporous silicon exchanges electrons extensively and reversibly with adsorbed species, e.g., NO2 and NH3. Such an exchange has been reported for systems that maintain their original p or n character. In the present case, a solid, which is a p-type semiconductor in bulk, converts to a “near insulator” when nanostructured. The near insulator may adopt either a p or an n nature with electron exchange, depending on the type of adsorbed molecule (see Figure).

    7. Size Fractionation of Metal Nanoparticles by Membrane Filtration (pages 532–535)

      A. Akthakul, A. I. Hochbaum, F. Stellacci and A. M. Mayes

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200400636

      Thumbnail image of graphical abstract

      A novel thin film composite nanofiltration (NF) membrane is fabricated by coating a conventional ultrafiltration membrane with a self-assembling amphiphilic graft copolymer. The NF membranes are used in the fractionation of gold nanoparticles to achieve a well-defined particle cutoff diameter and reduced size dispersity (see Figure).

    8. Mechanically Strong Hydrogels with Ultra-Low Frictional Coefficients (pages 535–538)

      D. Kaneko, T. Tada, T. Kurokawa, J. P. Gong and Y. Osada

      Version of Record online: 24 JAN 2005 | DOI: 10.1002/adma.200400739

      Thumbnail image of graphical abstract

      High-strength, low-frictional-coefficient gels are produced by adding a third component to a double-network gel (DN gel), of either a weakly crosslinked network or non-crosslinked linear chains (to produce, respectively, a triple-network gel (TN gel) and a DN-L gel, see Figure). All the gels are highly transparent. The DN-L gel shows a fracture strength as high as 9 MPa and its frictional coefficient is as low as 10–5 under an extremely high pressure of the order of sub-MPa.

    9. Hydrogen Physisorption in Metal–Organic Porous Crystals (pages 538–541)

      B. Panella and M. Hirscher

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200400946

      Thumbnail image of graphical abstract

      Hydrogen adsorption in microporous solid materials may enable H2 to be stored at lower pressures than in compressed-gas tanks, and at higher temperatures than for liquid H2. A new class of metal–organic frameworks (MOFs) with a high specific surface area appears promising for H2 storage. Here, the H2-uptake capacity of MOF-5 over a wide pressure range, at room temperature and at 77 K is investigated (see Figure). Adsorption of H2 exclusively in the micropores of these metal–organic frameworks is demonstrated.

    10. Three-Dimensional Spiral-Architecture Photonic Crystals Obtained By Direct Laser Writing (pages 541–545)

      K. K. Seet, V. Mizeikis, S. Matsuo, S. Juodkazis and H. Misawa

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401527

      Thumbnail image of graphical abstract

      A recently elaborated novel class of spiral-architecture photonic crystals, which has promising photonic bandgap properties, is realized by direct laser writing in SU-8 (see Figure). Such self-supporting structures show signatures of photonic stopgaps at infrared wavelengths, and can serve as accurate templates for infiltration of higher-refractive-index materials.

    11. Controllable Modification of SiC Nanowires Encapsulated in BN Nanotubes (pages 545–549)

      Y. Li, P. S. Dorozhkin, Y. Bando and D. Golberg

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401266

      Thumbnail image of graphical abstract

      Semiconducting β-SiC nanowires encapsulated in BN nanotubes are prepared using chemical vapor deposition (see Figure). An unusual feature—a gap of 10–15 nm in width between the inner wall of the BN tube and the SiC nanowire—allows various chemical and morphological modifications to be performed on the nanowires.

    12. Growth of Individual Vertical Germanium Nanowires (pages 549–553)

      P. Nguyen, H. T. Ng and M. Meyyappan

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200400908

      Thumbnail image of graphical abstract

      Vertical germanium nanowires (Figure, inset) can be synthesized on doped and undoped germanium substrates either as high-density arrays or as individual nanowires. The nanowires have smooth surfaces and uniform diameters, and possess (111) lattice fringes with an interplanar distance of 3.26 Å (Figure). Such vertical nanostructures are ideal for fabrication of vertical nanotransistors, such as surround-gate or top-gate transistors, and could be incorporated into other three- dimensional architectures.

    13. Templated Self-Assembly: Formation of Folded Structures by Relaxation of Pre-stressed, Planar Tapes (pages 553–557)

      M. Boncheva and G. M. Whitesides

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200400940

      Thumbnail image of graphical abstract

      A strategy for the formation of three-dimensional (3D) structures based on the spontaneous folding of elastomeric tapes is described. These tapes are fabricated in crimped, quasi-3D forms, and carry metal features supporting liquid solder. Self-assembly based on capillary interactions between drops of liquid solder results in folding of the tapes into structures that have quasi- and true 3D topology (see Figure).

    14. Incorporation of Highly Dispersed Gold Nanoparticles into the Pore Channels of Mesoporous Silica Thin Films and their Ultrafast Nonlinear Optical Response (pages 557–560)

      J.-L. Gu, J.-L. Shi, G.-J. You, L.-M. Xiong, S.-X. Qian, Z.-L. Hua and H.-R. Chen

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401085

      Thumbnail image of graphical abstract

      An ultrafast nonlinear optical Kerr response as fast as 190 fs is reported for mesoporous-silica-composite thin films loaded with highly dispersed gold nanoparticles. These are synthesized by a newly developed strategy, in which gold is introduced into the mesochannels of the silica by a surface-modification scheme coupled with a neutralization reaction route (see Figure).

    15. Observation of High-Aspect-Ratio Nanostructures Using Capillary Lithography (pages 560–564)

      K. Y. Suh, S.-J. Choi, S. J. Baek, T. W. Kim and R. Langer

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401089

      Thumbnail image of graphical abstract

      Several intriguing nanostructures, such as mushroom-like nanopillars, vertical nanopillars (see Figure), and nanospheres, are made using capillary lithography and a new, UV-curable mold consisting of polyurethane functionalized with an acrylate group. An aspect ratio as high as five is achieved for nanopillars 90 nm in diameter.

    16. Self-Assembled Silicon Nanotubes Grown from Silicon Monoxide (pages 564–567)

      Y.-W. Chen, Y.-H. Tang, L.-Z. Pei and C. Guo

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401381

      Thumbnail image of graphical abstract

      Self-assembled silicon nanotubes (SiNTs) are synthesized by a hydrothermal method, with silicon monoxide powder as a starting material and de-ionized water as a reaction medium. No metallic catalysts are added during the process. Unlike the disordered, aggregated SiNTs grown by the template method, the SiNTs synthesized here are self-assembled. The SiNTs have hollow structures with crystal silicon wall layers surrounded by an amorphous silica shell, as observed by transmission electron microscopy (see Figure).

    17. Compatibilization of a Photochromic Dithienylethene Dopant and Ferroelectric Liquid-Crystal Host via Siloxane Nanosegregation (pages 567–571)

      P. Zhang, E. Buncel and R. P. Lemieux

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401311

      Thumbnail image of graphical abstract

      Compatibilization of a photochromic dibenzothienylperfluorocyclopentene dopant (Figure) and a ferroelectric SmC* liquid-crystal host is achieved if both host and dopant are terminated with trisiloxane oligomers, which results in nanosegregation. Photocyclization of the photochromic dopant causes a large modulation of the electric polarization via a photomechanical effect.

    18. Synthesis of Boron Nitride with Ordered Mesostructure (pages 571–574)

      P. Dibandjo, L. Bois, F. Chassagneux, D. Cornu, J.-M. Letoffe, B. Toury, F. Babonneau and P. Miele

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401501

      Thumbnail image of graphical abstract

      The preparation of ordered mesoporous boron nitride (BN) by using trimethylaminoborazine as a BN source and mesoporous carbon CMK-3 as a template is reported. X-ray diffraction, transmission electron microscopy, and pore size analysis show that the structure of the synthesized BN molecular sieves consists of a two-dimensional regular array of uniform mesopores approximately 4.4 nm in diameter (see Figure).

    19. Electronic and Magnetic Properties of Ligand-Free FePt Nanoparticles (pages 574–578)

      H.-G. Boyen, K. Fauth, B. Stahl, P. Ziemann, G. Kästle, F. Weigl, F. Banhart, M. Hessler, G. Schütz, N. S. Gajbhiye, J. Ellrich, H. Hahn, M. Büttner, M. G. Garnier and P. Oelhafen

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200400748

      Thumbnail image of graphical abstract

      Ligand-free FePt nanoparticles are prepared in densely packed arrays (see Figure) under ultrahigh vacuum conditions, in which oxygen and hydrogen plasmas are used to remove the organic shells that are present after particle synthesis. The electronic structure and magnetic properties of the “bare”, face-centered-cubic FePt particles are presented. Applications in high-density magnetic data recording are foreseen.

    20. Topological Transformation of Vesicular Mesostructured Silica (pages 578–582)

      B. Wang, W. Shan, Y. Zhang, J. Xia, W. Yang, Z. Gao and Y. Tang

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401574

      Thumbnail image of graphical abstract

      The micrometer-scale self-assembly behaviour of MCM-41-type mesostructured silica is revealed through the study of a family of vesicular mesostructured silica with topology genus from 1 to 0 (see Figure and inside cover). The topological transformation and assembly kinetics demonstrate that the formation of the vesicular structure is closely correlated with the properties of the cetyltrimethylammonium–silicate building block and the hydrophobic nature of the ester additive.

    21. α-Fe2O3 Nanotubes in Gas Sensor and Lithium-Ion Battery Applications (pages 582–586)

      J. Chen, L. Xu, W. Li and X. Gou

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401101

      Thumbnail image of graphical abstract

      Templated arrays of α-Fe2O3 nanotubes, produced using an alumina membrane, exhibit enhanced sensitivity to ethanol and hydrogen as well as enhanced electrochemical activity in lithium-ion batteries. The nanotubes, characterized by uniform size and shape (see Figure), possess a high specific surface area, leading to electrochemical activities much higher than that of bulk or nanoparticulate α-Fe2O3.

    22. Structural and Optical Properties of Uniform ZnO Nanosheets (pages 586–590)

      S. J. Chen, Y. C. Liu, C. L. Shao, R. Mu, Y. M. Lu, J. Y. Zhang, D. Z. Shen and X. W. Fan

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401263

      Thumbnail image of graphical abstract

      ZnO nanosheets (see Figure) are fabricated by a physical vapor-transport technique. Temperature-dependent microphotoluminescence spectroscopy is conducted from 80–857 K. A surprisingly strong high-temperature (857 K) photon emission is observed. A brief discussion is given in an attempt to understand the physical mechanisms. Technically, this finding demonstrates that the ZnO nanostructure has a potential for high-temperature optoelectronic applications.

    23. Fully Transparent ZnO Thin-Film Transistor Produced at Room Temperature (pages 590–594)

      E. M. C. Fortunato, P. M. C. Barquinha, A. C. M. B. G. Pimentel, A. M. F. Gonçalves, A. J. S. Marques, L. M. N. Pereira and R. F. P. Martins

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200400368

      Thumbnail image of graphical abstract

      Fully transparent thin-film transistors (TFTs) are produced at room temperature by radiofrequency magnetron sputtering. Measuring the drain current (IDS) as a function of drain voltage (VDS) at different gate voltages (VGS) shows the TFTs possess “hard saturation” with on-currents of about 0.2 mA (see Figure) and saturation mobilities of 20 cm2 V–1 s–1. The optical and electrical properties and the compatibility of the fabrication process with low-cost plastic substrates show promise for invisible and flexible electronic circuits.

    24. High Carrier Mobility up to 0.1 cm2 V–1 s–1 at Ambient Temperatures in Thiophene-Based Smectic Liquid Crystals (pages 594–598)

      M. Funahashi and J.-I. Hanna

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401274

      Thumbnail image of graphical abstract

      The synthesis and carrier-transport properties of oligothiophene liquid-crystalline semiconductors are reported. An asymmetrically substituted terthiophene and quaterthiophene give rise to a highly ordered smectic mesophase (see Figure) with an excellent carrier mobility of up to 0.1  cm2 V–1 s–1 over a wide mesophase temperature range, including ambient temperatures. This mobility is comparable to that of organic polycrystals.

    25. Dendritic Nanowire Growth Mediated by a Self-Assembled Catalyst (pages 598–602)

      S. J. May, J.-G. Zheng, B. W. Wessels and L. J. Lauhon

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401332

      Thumbnail image of graphical abstract

      Dendritic growth of multiply branched InAs nanowires (see Figure and cover) is initiated by the controlled introduction of a Mn precursor in the context of vapor–liquid–solid nanowire growth by chemical vapor deposition. Self-assembly of Mn clusters leads to the nucleation and epitaxial growth of Mn-terminated InAs branches. The results provide a new route to the formation of hierarchical nanowire structures for nanoscale electronics and photonics.

    26. Polymerizable Transition-Metal-Containing Liquid Crystals with Thermally Reactive 1,3-Diene Tails (pages 602–606)

      A. G. Martin, S. Harms, W. Weigand and D. L. Gin

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200400996

      Thumbnail image of graphical abstract

      Crosslinkable metallomesogens containing thermally reactive 1,3-diene tails are described (see Figure). These polymerizable PdII and NiII-containing liquid crystals (LCs) exhibit LC behavior more similar to their non-polymerizable n-alkoxy parent compounds than their corresponding acrylate derivatives. The diene monomers can be thermally crosslinked in their LC states without significant degradation of their redox-sensitive metal centers via non-radical [4 + 2] intermolecular cycloaddition.

    27. Fabrication of Mixed Zn/Cu-Bound Polyimine Microspheres with Fine-Tuned Diameter and Internal Gradation of Metal Composition (pages 606–610)

      H. Houjou, T. Sasaki, Y. Shimizu, N. Koshizaki and M. Kanesato

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401281

      Thumbnail image of graphical abstract

      Monodisperse colloidal microspheres containing zinc and copper atoms in various ratios are fabricated by polymerization of an imine chain and concomitant metal binding. The distribution of the metal atoms inside the microspheres exhibit a gradation from the center to the surface (see Figure), which is explained by a kinetic model of the particle growth process.

    28. Magnetic Field Alignment of Liquid Crystals for Fast Display Applications (pages 610–614)

      M. I. Boamfa, S. V. Lazarenko, E. C. M. Vermolen, A. Kirilyuk and T. Rasing

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200400954

      Thumbnail image of graphical abstract

      A clean, contact-free method for liquid-crystal alignment using magnetic fields is reported. The method is simple and very robust, with a significantly smaller number of processing steps required than other existing methods. The electro-optical response of these magnetically aligned cells is about ten times faster than that of traditional rubbed liquid-crystal cells, with on and off switching times τ of 0.3 ms and 2.3 ms, respectively (see Figure).

    29. Spinning Solid and Hollow Polymer-Free Carbon Nanotube Fibers (pages 614–617)

      M. E. Kozlov, R. C. Capps, W. M. Sampson, V. H. Ebron, J. P. Ferraris and R. H. Baughman

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401130

      Thumbnail image of graphical abstract

      Polymer-free carbon nanotube fibers are spun from aqueous dispersions using a flocculation-based process that was developed. It produces hollow fibers, folded ribbon fibers, and solid fibers (see Figure). The fibers spun from single-walled nanotubes exhibit relatively high electrical conductivities (∼140 S cm–1 at room temperature) and electrochemical capacitances (∼100 F g–1) after annealing. Fiber supercapacitors are made from the spun fibers.

    30. Controlled Assembly of Protein–Nanoparticle Composites through Protein Surface Recognition (pages 617–621)

      S. Srivastava, A. Verma, B. L. Frankamp and V. M. Rotello

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200400776

      Thumbnail image of graphical abstract

      Controlled assembly of protein–nanoparticle composites through complementary protein surface recognition is demonstrated. Interaction of an unstable protein (chymotrypsin) with a gold nanoparticle results in close interparticle spacing, while a stable protein (cytochrome C) that retains its structure upon binding produces a hybrid material with a larger interparticle distance (see Figure).

    31. Tuning of Metal Work Functions with Self-Assembled Monolayers (pages 621–625)

      B. de Boer, A. Hadipour, M. M. Mandoc, T. van Woudenbergh and P. W. M. Blom

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401216

      Thumbnail image of graphical abstract

      Work functions of gold and silver are varied by over 1.4 and 1.7 eV, respectively, by using self-assembled monolayers. Using these modified electrodes, the hole current in a poly(2-methoxy-5-(2′-ethylhexyloxy)–1,4-phenylene vinylene) light-emitting diode is tuned by more than six orders of magnitude (see Figure). Suppression of the hole current enables measurement of the electron current in a polymer/polymer blend photovoltaic cell.

    32. A Novel Water-Free Proton-Conducting Solid Electrolyte based on an Organic/Inorganic Hybrid (pages 626–630)

      S.-Y. Lee, G. Scharfenberger, W. H. Meyer and G. Wegner

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200401198

      Thumbnail image of graphical abstract

      A novel water-free proton-conducting solid electrolyte based on an organic (CImSS)/inorganic (silicate) hybrid is presented (see Figure). In the absence of water, a remarkably high proton conductivity of around 10–4 S cm–1 at 160 °C is obtained for the CImSS/MTEOS-based silicate hybrid, which may be attributed to the well-developed percolation of the proton-conducting phase (CImSS) and its weaker interaction with the silicate.

    33. Nanostructured Assembly of Homopolymers for a Flexible Bragg Grating (pages 631–633)

      M. Kim, R. Nagarajan, J. H. Snook, L. A. Samuelson and J. Kumar

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200400693

      Thumbnail image of graphical abstract

      Fabrication of homogeneous, flexible, polymeric, dielectric Bragg gratings is demonstrated. The Bragg grating is assembled on a poly(ethylene terephthalate) film using polymeric colloidal microspheres of polystyrene (PS) and poly(methyl methacrylate) (PMMA) (see Figure). The microspheres are stacked successively with precise control at the nanometer scale and the gratings, free of metal and other inorganic materials, cover a relatively large area.

    34. Bicontinuous, Thermoresponsive, L3-Phase Silica Nanocomposites and Their Smart Drug-Delivery Applications (pages 634–637)

      J. H. Chang, C. H. Shim, B. J. Kim, Y. Shin, G. J. Exarhos and K. J. Kim

      Version of Record online: 3 MAR 2005 | DOI: 10.1002/adma.200400545

      Thumbnail image of graphical abstract

      Bicontinuous, thermosensitive, L3-phase silica nanocomposites are prepared by self-assembly of silicified L3-phase silicates and L3-phase silicates integrated with thermoresponsive poly(N-isopropylacryl amide) (PNIPAm; see Figure). In the L3-PNIPAm material, interpenetrating nanoscale networks of silica and polymer gel are formed, with which highly controlled drug delivery is successfully demonstrated.

SEARCH

SEARCH BY CITATION