Advanced Materials

Cover image for Vol. 15 Issue 7‐8

April, 2003

Volume 15, Issue 7-8

Pages 551–658

    1. You have free access to this content
      In Profile: Andreas Hirsch (page 561)

      Version of Record online: 10 APR 2003 | DOI: 10.1002/adma.200390133

    2. Plasmonics—A Route to Nanoscale Optical Devices (Advanced Materials, 2001, 13, 1501) (page 562)

      S.A. Maier, M.L. Brongersma, P.G. Kik, S. Meltzer, A.A.G. Requicha, B.E. Koel and H.A. Atwater

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200390134

    3. Tunable Inverse Opal Hydrogel pH Sensors (pages 563–566)

      Y.-J. Lee and P.V. Braun

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304588

      The synthesis, swelling kinetics, and optical diffraction of inverse opal hydrogel sensors (see Figure) are demonstrated. Colloidal crystal templating is used to prepare methacrylate/acrylic acid (AA) copolymers that have an interconnected pore structure, allowing facile diffusion and a relatively rapid response. The system shows good mechanical stability and pH-dependent shifts in optical diffraction regulated by the AA concentration.

    4. Nanoscale Ultraviolet-Light-Emitting Diodes Using Wide-Bandgap Gallium Nitride Nanorods (pages 567–569)

      H.-M. Kim, T.W. Kang and K.S. Chung

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304554

      The fabrication of p–n junctions in individual GaN nanorods has been realized using hydride vapor phase epitaxy. Application of the resulting heterostructures as wide bandgap current rectifiers with a high breakdown voltage and for near UV light-emitting diodes is demonstrated. The Figure is a luminescence image of the light emitted from a forward-biased nanorod p–n junction at 3 V.

    5. Light-Driven Side-On Nematic Elastomer Actuators (pages 569–572)

      M.-H. Li, P. Keller, B. Li, X. Wang and M. Brunet

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304552

      A range of monodomain nematic azo side-on elastomers, containing different proportions of photoisomerizable azo mesogenic moieties, were prepared for the first time photochemically using a radical photoinitiator working at wavelengths above 600 nm. These elastomers exhibit a photomechanical contraction of up to 20 % upon irradiation with UV light. The Figure shows an elastomer film in its contracted form under UV irradiation.

    6. Spin-on Nanostructured Silicon–Silica Film Displaying Room-Temperature Nanosecond Lifetime Photoluminescence (pages 572–576)

      Y. Cohen, B. Hatton, H. Míguez, N. Coombs, S. Fournier-Bidoz, J.K. Grey, R. Beaulac, C. Reber and G.A. Ozin

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304491

      A yellow transparent mesoporous silica film has been achieved by the incorporation of silicon nanoclusters into its channels. The resulting nanocomposite—fabricated using a combination of evaporation induced self- assembly and chemical vapor deposition—emits light brightly at visible wavelengths and has nanosecond radiative lifetimes at room temperature when excited by ultraviolet light (see Figure).

    7. Universal Route to Cell Micropatterning Using an Amphiphilic Comb Polymer (pages 576–579)

      J. Hyun, H. Ma, Z. Zhang, T.P. Beebe Jr. and A. Chilkoti

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304496

      Long-term, spatially resolved attachment and growth of mammalian cells in a biologically relevant milieu on a variety of substrates is possible using the micropatterning techniques presented here (see cover). Two general methods, both involving microcontact printing of an amphiphilic comb polymer (see Figure) and incubation with a protein-containing solution are reported.

    8. Novel Synthesis of Pt6Si5 Nanowires and Pt6Si5–Si Nanowire Heterojunctions by Using Polycrystalline Pt Nanowires as Templates (pages 579–581)

      J. Luo, L. Zhang and J. Zhu

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304432

      Pt6Si5 nanowires and Pt6Si5–Si nanowire heterojunctions (see Figure) have been synthesized by electrodeposition using polycrystalline Pt nanowires as templates. In the synthesis, the polycrystalline nature of the Pt nanowires played an important role. A dependence between the diameters of the products and the Pt nanowires was detected. These junctions would find applications in future nano-electronics.

    9. Single-Crystalline In2O3 Nanotubes Filled with In (pages 581–585)

      Y. Li, Y. Bando and D. Golberg

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304539

      Single-crystalline In2O3 nanotubes with cubic structure were synthesized via a physical vapor depostion process. The nanotubes grew along the 〈111〉 direction and were continuously filled with metallic In (see Figure). Photoluminescence measurement results displayed strong orange emission. Indium-filled In2O3 nanotubes represent an exciting system and offer great potential for application in electronic devices or “nanothermometers”.

    10. Multiple Ordering Transitions: Hierarchical Self-Assembly of Rod–Coil Block Copolymers (pages 585–588)

      J.-W. Park and E.L. Thomas

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304591

      Organized structures over length scales differing by 103 are reported, i.e., crystals of rod block (unit cell ∼ 1 nm), block copolymer microdomains (layer periodicity ∼ 50 nm), and Néel domain walls (wall periodicity ∼ 1000 nm)—see Figure and inside front cover. The result is an example of combined dynamic and static self- assembly, which creates an unconventional morphology with multiple length scales in a single-step process.

    11. Directed Growth of Polymethylene Films on Atomically Modified Gold Surface (pages 588–591)

      W. Guo and G.K. Jennings

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304859

      Gold surfaces patterned with underpotentially deposited copper and/or silver monolayers are used to direct the growth of highly insulating polymethylene films. Copper adatoms function as active catalytic sites to enhance polymer film growth over that of unmodified gold surfaces (see Figure). In contrast, a silver monolayer is inactive toward the polymerization and can be patterned to locally prevent film growth.

    12. Meso/Macroporous Inorganic Oxide Monoliths from Polymer Foams (pages 591–596)

      H. Maekawa, J. Esquena, S. Bishop, C. Solans and B.F. Chmelka

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304248

      Low-density bimodal inorganic oxide monoliths (see Figure) have been prepared via a two-step procedure using macroporous polystyrene foams and amphiphilic block copolymer structure-directing agents. The resulting meso/macroporous inorganic framework structures could be obtained with different 3D bulk shapes and for a range of inorganic oxides, as demonstrated here for silica, zirconia, and titania.

    13. A New Synthetic Approach to Silicon Colloidal Photonic Crystals with a Novel Topology and an Omni-Directional Photonic Bandgap: Micromolding in Inverse Silica Opal (MISO) (pages 597–600)

      H. Míguez, N. Tétreault, S.M. Yang, V. Kitaev and G.A. Ozin

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304043

      High refractive index contrast silicon colloidal photonic crystals having a different topology to those previously reported have been synthesized. A new process of colloidal-crystal templating based on micromolding in inverse silica opals (MISO) is used (see Figure), and photonic crystals so built present a full photonic bandgap, as indicated by band structure calculations.

    14. High Permittivity from Defective Multiwalled Carbon Nanotubes in the X-Band (pages 600–603)

      P.C.P. Watts, W.-K. Hsu, A. Barnes and B. Chambers

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304485

      Defective multiwalled carbon nanotubes display higher real permittivity than graphitic carbon nanotubes (CNTs). That is the conclusion of the study presented here in which the permittivity of Fe-filled and boron-doped CNTs in the X-band is compared with that of graphitic CNTs made by arc discharge. However, the imaginary parts of the permittivity are still very low in all three cases. This finding indicates that defective CNTs are excellent dielectric materials and can be used as supercapacitor components, i.e., high-energy storage systems.

    15. Focused Microwave-Assisted Synthesis of 2,5-Dihydrofuran Derivatives as Electron Acceptors for Highly Efficient Nonlinear Optical Chromophores (pages 603–607)

      S. Liu, M.A. Haller, H. Ma, L.R. Dalton, S.-H. Jang and A.K.-Y. Jen

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304813

      Highly efficient and tunable electron acceptors composed of a diverse family of 2,5-dihydrofuran derivatives have been synthesized using single-mode focused microwave irradiation. A very large electro-optic coefficient and long-term temporal stability (see Figure) have been demonstrated in a host/guest system composed of polyquinoline and the nonlinear optical chromophore shown in the Figure.

    16. Growth Direction and Cross-Sectional Study of Silicon Nanowires (pages 607–609)

      C.-P. Li, C.-S. Lee, X.-L. Ma, N. Wang, R.-Q. Zhang and S.-T. Lee

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304409

      Cross-sectional samples of silicon nanowires (SiNWs) are examined using transmission electron microscopy. The cross-sections are bounded by well-defined low-index crystallographic facets of various shapes (e.g., the square section in the Figure, 50 nm edge) and characterized by shape-dependent growth directions, with 〈112〉 and 〈110〉 predominating. Both shape and growth direction are consistent with surface energy considerations and growth mechanisms.

    17. High-Performance, Quantum Dot Nanocomposites for Nonlinear Optical and Optical Gain Applications (pages 610–613)

      M.A. Petruska, A.V. Malko, P.M. Voyles and V.I. Klimov

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304450

      The preparation of CdSe nanocrystal quantum dot (NQD)–titania nanocomposites (see Figure) exhibiting large NQD packing densities and high photoluminescence quantum efficiencies is described. These new materials show both large third-order nonlinear susceptibilities and optical gain. Furthermore, micro-ring lasing and efficient dynamic holographic gratings using these nanocomposites are demonstrated.

    18. Infrared Detectors with Poly(3,4-ethylenedioxy thiophene)/Poly(styrene sulfonic acid) (PEDOT/PSS) as the Active Material (pages 613–616)

      S.C.J. Meskers, J.K.J. van Duren, R.A.J. Janssen, F. Louwet and L. Groenendaal

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304592

      Fast-response large-area plastic infrared detectors (see Figure (Wheatstone bridge configuration)) made from a conducting PEDOT/PSS film achieve a detectivity close to 105 cm √Hz W–1 at 1.18 eV. The nanosecond response arises from the direct absorption of infrared light by the charge carriers on the polymer chain. The recovery of the device after illumination is much slower and is governed by heat transport from the polymer.

    19. Excellent Wave Absorption by Zirconium-Based Bulk Metallic Glass Composites Containing Carbon Nanotubes (pages 616–621)

      Z. Bian, R.J. Wang, M.X. Pan, D.Q. Zhao and W.H. Wang

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304565

      Bulk metallic glass composites containing carbon nanotubes (CNTs) are reported (see Figure). The composites are found to have strong ultrasonic wave-absorption abilities, which increase dramatically with increasing volume fraction of CNTs. This ability implies that such composites, besides their excellent mechanical properties, may also have a significant potential of application in shielding acoustic sound or environmental noise.

    20. Biomimetic Formation of Porous Single-Crystalline CaCO3 via Nanocrystal Aggregation (pages 621–623)

      J. Zhan, H.-P. Lin and C.-Y. Mou

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304600

      Hexagonal CaCO3 vaterite particles with intracrystalline gelatin were obtained from calcium nitrate and urea in the presence of gelatin. The particles have the crystallographic nature of vaterite (see Figure: an SEM image). Detailed analysis indicates that the crystals grow from vaterite nanocrystals by self-oriented aggregation growth, with gelatin playing a role in both the stabilization and the oriented attachment of the nanocrystals.

    21. Extreme Changes in the Electrical Resistance of Titania Nanotubes with Hydrogen Exposure (pages 624–627)

      O.K. Varghese, D. Gong, M. Paulose, K.G. Ong, E.C. Dickey and C.A. Grimes

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304586

      Extremely sensitive, drift-free, and robust hydrogen sensors based on titania nanotube arrays (see Figure) are reported. Very large changes in the electrical conductivity of the nanotubes upon exposure to hydrogen gas have been measured, over one order of magnitude greater than the previous record. Dependence of the electrical conductivity on both temperature and nanotube pore size is found.

    22. Solid-State Rechargeable Magnesium Batteries (pages 627–630)

      O. Chusid, Y. Gofer, H. Gizbar, Y. Vestfrid, E. Levi, D. Aurbach and I. Riech

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304415

      The development of all solid-state rechargeable magnesium battery systems is reported, with components that are environmentally friendly and relatively simple in their structure and preparation. As anodes, magnesium alloys containing Zn and Al are used, and the cathode is the chevrel phase, Mo6S8, which can insert two magnesium atoms per unit (Mg2Mo6S8, 122 mA h g–1). The solid electrolyte is a gel comprising polyvinylidene difluoride, Mg(AlCl2EtBt)2 complex salt, and tetraglyme as a plasticizer. These batteries are found to function well in a temperature range of 0–80 °C with a voltage range of 1.3–0.8V.

    23. Field-Induced Formation of the Polar SmCP Phase above the SmCP–Isotropic Transition (pages 630–633)

      W. Weissflog, M.W. Schröder, S. Diele and G. Pelzl

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200304570

      The field-induced formation of an antiferroelectric “banana mesophase” (SmCPA), which can be observed at up to 9 K above the transition SmCP [RIGHTWARDS ARROW] isotropic, is reported. This behavior may be due to the existence of ferroelectric clusters already in the isotropic liquid that are aligned by means of the external electric field. The Figure displays the field-induced nucleation of the SmCP phase within the isotropic liquid.

    24. Oxide-Assisted Growth of Semiconducting Nanowires (pages 635–640)

      R.-Q. Zhang, Y. Lifshitz and S.-T. Lee

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200301641

      Large quantities of high-purity semiconducting nanowires with a preferential growth direction, uniform size, and long length can be produced without the need for a metal catalyst using the oxide-assisted growth (OAG) technique. Nanostructures from a variety of materials, including Si, Ge, C, SnO2, and Group III–V and II–VI semiconductors can be synthesized this way. The Figure shows ZnO whiskers synthesized using OAG.

    25. Metal Nanostructures with Hollow Interiors (pages 641–646)

      Y. Sun, B. Mayers and Y. Xia

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200301639

      A simple and versatile route has been developed for the large-scale synthesis of metal nanostructures with well-defined hollow interiors. The capability of the method has been demonstrated by preparing a range of hollow nanostructures of gold (e.g., triangular rings, prism-shaped or cubic boxes, spherical capsules, and tubes), and it also works well for other metals such as Pt and Pd (see Figure for an SEM image of Pd nanotubes).

    26. Ultra-Low Surface Energy Polymers: The Molecular Design Requirements (pages 647–650)

      J. Tsibouklis and T.G. Nevell

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200301638

      The molecular design requirements for the synthesis of polymeric materials that can be used for the fabrication of readily accessible film structures with ultra-low surface energy characteristics are described. These new ultra-low surface energy polymers contribute to developments in conventional low surface energy materials and have potential uses that are as diverse as lubrication, wear control, antifouling, and antisoiling, which will have weighty commercial implications.

    27. Fullerene-like WS2 Nanoparticles: Superior Lubricants for Harsh Conditions (pages 651–655)

      L. Rapoport, N. Fleischer and R. Tenne

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200301640

      Fullerene-like WS2 nanoparticles are shown to produce substantial improvements in the tribological behavior of various contact pairs under harsh conditions. Here, this area is briefly reviewed and the mechanisms leading to the observed superior behavior are elucidated. The Figure shows the improvements in seizure load gained by adding nanoparticles to lubricating oil.

    28. Author Index Adv. Mater. 7–8/2003 (page 657)

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200390135

    29. Subject Index Adv. Mater. 7–8/2003 (page 658)

      Version of Record online: 9 APR 2003 | DOI: 10.1002/adma.200390136