Advanced Materials

Cover image for Vol. 19 Issue 19

October, 2007

Volume 19, Issue 19

Pages 2719–3059

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Index
    1. Cover Picture: Novel Structure of AAO Film Fabricated by Constant Current Anodization (Adv. Mater. 19/2007)

      S. Zhao, K. Chan, A. Yelon and T. Veres

      Version of Record online: 1 OCT 2007 | DOI: 10.1002/adma.200790074

      Thumbnail image of graphical abstract

      AAO films with a novel six-membered ring structure were prepared by constant current anodization. The six-membered ring contains smaller pores, formed at the triple junction sites of the larger pores. The interpore distance was reduced from the usual 85 nm to 50 nm, doubling the usual pore density. These novel AAO film structures with high pore density may have applications in the preparation of mosaic nanowire arrays and photonic devices.

  2. Inside Front Cover

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Index
    1. Inside Front Cover: Combinatorial Modification of Degradable Polymers Enables Transfection of Human Cells Comparable to Adenovirus (Adv. Mater. 19/2007)

      J. J. Green, G. T. Zugates, N. C. Tedford, Y.-H. Huang, L. G. Griffith, D. A. Lauffenburger, J. A. Sawicki, R. Langer and D. G. Anderson

      Version of Record online: 1 OCT 2007 | DOI: 10.1002/adma.200790075

      Thumbnail image of graphical abstract

      End-modified poly(β-amino ester)s, easy-to-synthesize degradable polymers, are able to deliver DNA to primary human cells at levels comparable to adenovirus and two orders of magnitude better than the commonly used non-viral vector, polyethylenimine. Small structural changes are found to affect multiple steps of gene delivery including the DNA binding affinity, nanoparticle size, intracellular DNA uptake, and final protein expression. In vivo, these polymer modifications enhance DNA delivery to ovarian tumors.

  3. Contents

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Index
  4. Review

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Index
    1. Nonlinear Optical Properties of Porphyrins (pages 2737–2774)

      M. O. Senge, M. Fazekas, E. G. A. Notaras, W. J. Blau, M. Zawadzka, O. B. Locos and E. M. Ni Mhuircheartaigh

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/adma.200601850

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      The use of porphyrins for studies in nonlinear optics has advanced significantly in recent years. The review summarizes the progress in the synthesis of suitable material, their nonlinear optical characteristics and utility for applications.

  5. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Index
    1. Myogenic Induction of Aligned Mesenchymal Stem Cell Sheets by Culture on Thermally Responsive Electrospun Nanofibers (pages 2775–2779)

      J. M. Dang and K. W. Leong

      Version of Record online: 21 AUG 2007 | DOI: 10.1002/adma.200602159

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      A thermally reversible culture substrate with a topographically active surface of aligned nanofibers is able to induce cytoskeletal alignment and nucleus elongation. These morphological changes induce myogenic differentiation in stem cells. The differentiated cells can be recovered in sheet form by thermally induced dissolution of the substrate. A surface able to provide topographical cues to create an aligned stem cell sheet, activated to differentiate to a specific lineage, can have a significant impact on engineering of tissue constructs for regenerative medicine applications.

    2. Polymerization of an Organogel Formed by a Hetero-bifunctional Gelator in a Monomeric Solvent: Preparation of Nanofibers Embedded in a Polymer Matrix (pages 2780–2784)

      S. H. Kang, B. M. Jung and J. Y. Chang

      Version of Record online: 21 AUG 2007 | DOI: 10.1002/adma.200700117

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      A hetero-bifunctional gelator composed of two different polymerizable groups, acryl and diacetylene, and used to gelate an acrylic monomer has been prepared. The photopolymerization of the organogel formed in hexyl methacrylate produces a free-standing film, in which fluorescent polydiacetylene nanofibers are embedded in a poly(hexyl methacrylate) matrix (see figure).

    3. Dynamics of Threshold Voltage Shifts in Organic and Amorphous Silicon Field-Effect Transistors (pages 2785–2789)

      S. G. J. Mathijssen, M. Cölle, H. Gomes, E. C. P. Smits, B. de Boer, I. McCulloch, P. A. Bobbert and D. M. de Leeuw

      Version of Record online: 21 AUG 2007 | DOI: 10.1002/adma.200602798

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      The electrical instability of organic field-effect transistors is investigated. We observe that the threshold-voltage shift (see figure) shows a stretched- exponential time dependence under an applied gate bias. The activation energy of 0.6 eV is common for our and all other organic transistors reported so far. The constant activation energy supports charge trapping by residual water as the common origin.

    4. Bioavailability of Nickel in Single-Wall Carbon Nanotubes (pages 2790–2796)

      X. Liu, V. Gurel, D. Morris, D. W. Murray, A. Zhitkovich, A. B. Kane and R. H. Hurt

      Version of Record online: 23 AUG 2007 | DOI: 10.1002/adma.200602696

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      The biomolecular mechanism of nickel carcinogenicity is driven by intracellular Ni cation. The role of nickel catalyst in single-wall carbon nanotube toxicity will therefore depend on its bioavailability, which is highly uncertain due to encapsulation by carbon shells. This article measures the material-specific Ni release into extra- and intracellular physiological fluid phases and suggests practical techniques for managing the metals contribution to SWNT toxicity.

    5. Well-Aligned Nanocylinder Formation in Phase-Separated Metal-Silicide–Silicon and Metal-Germanide–Germanium Systems (pages 2797–2801)

      N. Yasui, R. Horie, Y. Ohashi, K. Tanji and T. Den

      Version of Record online: 23 AUG 2007 | DOI: 10.1002/adma.200700726

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      Well-aligned nanocylinder formation (see figure) is carried out by using conventional sputtering deposition. Various metal-silicide–silicon and metal-germanide–germanium systems exhibit uniform phase separation with ordered cylinder arrays in a matrix with periodic spacing from 1.9 to 20.2 nm. There is a correlation between the periodic spacing of the cylinders and the eutectic temperatures in these systems.

    6. Morphological Changes and Multicolor Photochromism of Ag Nanoparticles Deposited on Single-crystalline TiO2 Surfaces (pages 2802–2806)

      K. Matsubara and T. Tatsuma

      Version of Record online: 29 AUG 2007 | DOI: 10.1002/adma.200602823

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      Silver gets fat and thin: Ag nanoparticles photocatalytically deposited on rutile TiO2 single crystals exhibit multicolor photochromism. Under monochromatic visible light, particles resonant with the light are photoelectrochemically dissolved, and re-deposited on the TiO2 substrate or non-resonant particles. These size-selective dissolution and growth are responsible for the wavelength-dependent color changes.

    7. An Electro- and Thermochromic Hydrogel as a Full-Color Indicator (pages 2807–2812)

      K. Ueno, K. Matsubara, M. Watanabe and Y. Takeoka

      Version of Record online: 12 SEP 2007 | DOI: 10.1002/adma.200700159

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      Electric-field-triggered “two-state switching” between two arbitrary structural colors (see figure) in the entire visible region at certain temperatures is shown by a stimuli-responsive chromic hydrogel. The external rapid tuning in the structural color of this hydrogel is successfully achieved by introducing a periodically ordered interconnecting porous structure.

    8. Hydrogenography: An Optical Combinatorial Method To Find New Light-Weight Hydrogen-Storage Materials (pages 2813–2817)

      R. Gremaud, C. P. Broedersz, D. M. Borsa, A. Borgschulte, P. Mauron, H. Schreuders, J. H. Rector, B. Dam and R. Griessen

      Version of Record online: 29 AUG 2007 | DOI: 10.1002/adma.200602560

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      Hydrogenography optically monitors hydrogen ab- and desorption simultaneously on thousands of alloy compositions under exactly the same experimental conditions. In this way the hydride-formation enthalpy map of the Mg–Ni–Ti–H system is determined from a compositional gradient thin film. The figure shows that the region of interesting hydrogen-storage materials is in dark blue, with enthalpies of around –40 kJ (mol H2)–1.

    9. High-Performance, Flexible Hydrogen Sensors That Use Carbon Nanotubes Decorated with Palladium Nanoparticles (pages 2818–2823)

      Y. Sun and H. H. Wang

      Version of Record online: 29 AUG 2007 | DOI: 10.1002/adma.200602975

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      Single-walled carbon nanotubes decorated with Pd nanoparticles on thin poly(ethylene terephthalate) sheets serve as building blocks for the fabrication of mechanically flexible hydrogen sensors (left frame of the figure) with excellent sensing performance. The sensitivities (i.e., the change of resistance) of the as-fabricated sensors are comparable to (or even higher than) the sensors built on rigid substrates and the responses are reversible (right frame of the figure).

    10. Bright Light Emission of a Single Polythiophene Nanotube Strand with a Nanometer-scale Metal Coating (pages 2824–2829)

      J. Joo, D. H. Park, M.-Y. Jeong, Y. B. Lee, H. S. Kim, W. J. Choi, Q.-H. Park, H.-J. Kim, D.-C. Kim and J. Kim

      Version of Record online: 29 AUG 2007 | DOI: 10.1002/adma.200700479

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      Bi-layered hybrid nanostructures of polythiophene (PTh) and metal nanotubes are fabricated by a sequential electrochemical synthetic method. Huge enhancement of photoluminescence of PTh single nanotubes coated with nanometer-scale Cu, Ni, or Co metal is observed by using a laser confocal microscope, and can be explained by the effect of surface plasmon resonance. Bright light emission from a single strand of a PTh/Cu hybrid nanotube is observed (see figure).

    11. Synthesis of Core-Crosslinked Nanoparticles with Controlled Cylindrical Shape and Narrowly-Dispersed Size via Core-Shell Brush Block Copolymer Templates (pages 2830–2835)

      C. Cheng, K. Qi, D. S. Germack, E. Khoshdel and K. L. Wooley

      Version of Record online: 5 SEP 2007 | DOI: 10.1002/adma.200602986

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      Core-crosslinked nanocylinders with well-defined shape and narrowly-dispersed size are prepared by using S2Cl2 to react with the alkenyl functionalities of the PNb-g-PIp-based core domain of cylindrical core-shell brush block copolymer, PNb-g-PIp-b-PtBA (see figure). This strategy potentially may be further extended by using brush copolymer templates having different compositional, structural and topological features for the synthesis of a broad variety of crosslinked nanostructures with diverse shapes and sizes.

    12. Combinatorial Modification of Degradable Polymers Enables Transfection of Human Cells Comparable to Adenovirus (pages 2836–2842)

      J. J. Green, G. T. Zugates, N. C. Tedford, Y.-H. Huang, L. G. Griffith, D. A. Lauffenburger, J. A. Sawicki, R. Langer and D. G. Anderson

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/adma.200700371

      Thumbnail image of graphical abstract

      End-modified poly(β-amino ester)s, easy-to-synthesize degradable polymers, are able to deliver DNA to primary human cells at levels comparable to adenovirus and two orders of magnitude better than the commonly used non-viral vector, polyethylenimine. Small structural changes are found to affect multiple steps of gene delivery including the DNA binding affinity, nanoparticle size, intracellular DNA uptake, and final protein expression. In vivo, these polymer modifications enhance DNA delivery to ovarian tumors.

    13. A Tetrazolate- and Cyano-Bridged Homometallic Mixed-Valence Copper(I,II) Molecular Ferrimagnet (pages 2843–2846)

      X.-M. Zhang, Y.-F. Zhao, X.-W. Zhang and X.-M. Chen

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/adma.200602410

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      A solvothermal reaction of a cupric salt and tetrazole in acetonitrile generates a tetrazolate (tta)- and cyano-bridged homometallic mixed- valence copper(I,II) molecular ferrimagnet, [Cu5(tta)6(CN)2] (see figure), that exhibits a field-induced transition from a 3D antiferromagnetic state to a ferrimagnetic state at 7.9 K.

    14. Silk Fibroin Microfluidic Devices (pages 2847–2850)

      C. J. Bettinger, K. M. Cyr, A. Matsumoto, R. Langer, J. T. Borenstein and D. L. Kaplan

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/adma.200602487

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      Microfluidic devices were fabricated from silk fibroin using an aqueous molding process adapted from soft lithography. The process results in mechanically robust, patent devices with macroscopic fluidic connections. Hepatocytes were seeded in the device and perfused for up to five days during which they exhibited liver-specific functions equivalent to that observed for standard tissue culture substrates.

    15. Shape-Memory Effects in Polymer Networks Containing Reversibly Associating Side-Groups (pages 2851–2855)

      J. Li, J. A. Viveros, M. H. Wrue and M. Anthamatten

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/adma.200602260

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      A new type of lightly crosslinked shape-memory polymer that contains reversibly associating side-groups is reported. H-bonding interactions stabilize mechanically strained states at low temperatures. The materials' shape recovery rate exhibits Arrhenius-like temperature dependence due to the dynamics of H-bond dissociation.

    16. A Facile Synthesis Route to Prepare Microtubes from Phosphate Glass Fibres (pages 2856–2862)

      E. A. Abou Neel, A. M. Young, S. N. Nazhat and J. C. Knowles

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/adma.200700039

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      Fabrication of calcium phosphate microtubes is performed utilizing a simple dissolution-reprecipitation mechanism, to form amorphous microtubes with sizes of the order of 10 to 20μm. Raman microspectroscopy gives more understanding of the degradation and formation mechanism.

    17. Grafted Conducting Polymer Films for Nano-patterning onto Various Organic and Inorganic Substrates by Oxidative Chemical Vapor Deposition (pages 2863–2867)

      S. G. Im, P. J. Yoo, P. T. Hammond and K. K. Gleason

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/adma.200701170

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      Conductive polymer chains were directly grafted on a variety of organic substrates containing aromatic functionalities. In this one-step mechanism, the covalent linkages between the substrates and the conducting polymers are created. The enhanced adhesion by grafting enables high-resolution patterning (down to 60 nm) of grafted PEDOT films using standard lithographic techniques without any modification of the patterning processes.

    18. Pentacene Nanostructures on Surface-Hydrophobicity-Controlled Polymer/SiO2 Bilayer Gate-Dielectrics (pages 2868–2872)

      H. Yang, S. H. Kim, L. Yang, S. Y. Yang and C. E. Park

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/adma.200700560

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      New evidence of a pentacene “bulk phase”, which shows a different layer orientation from the “thin-film phase”, was discovered. Thin films prepared on surface-hydrophobicity-controlled polymer/SiO2 dielectrics, were studied by using 2D grazing-incidence X-ray diffraction.

    19. Photoinduced Self-Assembly of TiO2 and SiO2 Nanoparticles on Sidewalls of Single-Walled Carbon Nanotubes (pages 2873–2876)

      H. S. Shin, Y. S. Jang, Y. Lee, Y. Jung, S. B. Kim and H. C. Choi

      Version of Record online: 1 OCT 2007 | DOI: 10.1002/adma.200602660

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      Titanium oxide and silicon oxide nanoparticles (TiO2 and SiO2 NPs) are selectively self-assembled on the sidewalls of single-walled carbon nanotubes (SWNTs) grown on a p-type Si substrate by using a simple UV irradiation in an aqueous media.

    20. Facile Method of Controlling Monomer Sequence Distributions in Random Copolymers (pages 2877–2883)

      J. J. Semler, Y. K. Jhon, A. Tonelli, M. Beevers, R. Krishnamoorti and J. Genzer

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/adma.200602359

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      Copolymers of poly(styrene-co-4-bromostyrene) (PBrxS) with adjustable monomer sequence distribution of styrene (S) and 4-bromostyrene (4-BrS) and composition (x = content of 4-BrS) are prepared by brominating parent polystyrene (PS). While bromination reaction carried out above the theta temperature (Θ) leads to PBrxS with random monomer distribution, bromination of PS performed at temperatures below Θ produces PBrxS having a random-blocky character.

    21. Energetic Nitrogen Rich Salts of N,N-bis[1(2)H-Tetrazol-5-yl]amine (pages 2884–2888)

      Y. Guo, H. Gao, B. Twamley and J. M. Shreeve

      Version of Record online: 23 AUG 2007 | DOI: 10.1002/adma.200602647

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      Reactions of N,N-bis-[1(2)H-tetrazol-5-yl]amine (H2Bta) with several high nitrogen molecules result in new nitrogen rich energetic salts (see figure). Densities, melting points, decomposition temperatures and elemental analyses are reported. Based on their calculated heats of formation, detonation properties, and thermal and hydrolytic stabilities, these stable compounds hold promise for energetic applications.

    22. Visible-Light Photocatalytic Properties of Weak Magnetic BiFeO3 Nanoparticles (pages 2889–2892)

      F. Gao, X. Y. Chen, K. B. Yin, S. Dong, Z. F. Ren, F. Yuan, T. Yu, Z. G. Zou and J.-M. Liu

      Version of Record online: 28 AUG 2007 | DOI: 10.1002/adma.200602377

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      Polycrystalline BiFeO3nanoparticles (size 80–120 nm) are prepared by a simple sol–gel technique. Such nanoparticles are very efficient for photocatalytic decomposition of organic contaminants under irradiation from ultraviolet to visible frequencies. The BiFeO3 nanoparticles also demonstrate weak ferromagnetism of about 0.06 μB/Fe at room temperature, in good agreement with theoretical calculations.

    23. Electrode Grids for ITO Free Organic Photovoltaic Devices (pages 2893–2897)

      K. Tvingstedt and O. Inganäs

      Version of Record online: 23 AUG 2007 | DOI: 10.1002/adma.200602561

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      Silver grids are utilized to exclude the expensive use of indium tin oxide (ITO) in conjugated polymer photovoltaic devices. The grids are generated by electroless deposition from elastomeric microfluidic channels onto transparent substrates. The organic photovoltaic devices demonstrated here, with minimized series resistance, are confirmed to have characteristics comparable to devices exploiting ITO.

    24. Temperature Gating of the Ring-Opening Process in Diarylethene Molecular Switches (pages 2898–2902)

      D. Dulić, T. Kudernac, A. Pužys, B. L. Feringa and B. J. van Wees

      Version of Record online: 28 AUG 2007 | DOI: 10.1002/adma.200700161

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      The ring-opening process in diarylethene molecular switches is suppressed with decreasing temperature, leading to the complete absence of the photoreaction below a cutoff temperature. By contrast, the reverse ring-closure process shows no significant temperature dependence above 115 K. Reversibility of the photoprocesses can be thus controlled by temperature (see figure).

    25. Hydrogel-Encapsulated Microfabricated Haircells Mimicking Fish Cupula Neuromast (pages 2903–2909)

      S. Peleshanko, M. D. Julian, M. Ornatska, M. E. McConney, M. C. LeMieux, N. Chen, C. Tucker, Y. Yang, C. Liu, J. A. C. Humphrey and V. V. Tsukruk

      Version of Record online: 28 AUG 2007 | DOI: 10.1002/adma.200701141

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      A hydrogel-capped hair-cell flow microsensor, which closely mimics a superficial neuromast of a fish, is introduced. By encapsulating the hair sensor into the artificial hydrogel cupula a dramatic increase in hair-sensor sensitivity to the oscillating and the steady flow is achieved. It opens the way toward the remote monitoring of the underwater environment by autonomous, unmanned microvehicles with self-navigating capability.

    26. Observation of the Pressure Dependent Reversible Enhancement of Tc and Loss of the Anomalous Constricted Hysteresis for [Ru2(O2CMe)4]3[Cr(CN)6] (pages 2910–2913)

      W. W. Shum, J.-H. Her, P. W. Stephens, Y. Lee and J. S. Miller

      Version of Record online: 29 AUG 2007 | DOI: 10.1002/adma.200602751

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      The temperature and pressure dependencies of the magnetization, M(T,P), of cubic [Ru2(O2CMe)4]3[Cr(CN)6] reveals that Tc reversibly increases with increasing pressure up to 83 % to 59 K at 12.8 kbar (2.1 K kbar–1), and the pressure dependence of the hysteresis, M(H,P), shows that the anomalous constricted hysteresis observed at ambient pressure disappears at higher pressure (see figure).

    27. Metal–Insulator Transition in Solution-Processible Porphyrinic Field-Effect Transistors (pages 2914–2917)

      A. S. Dhoot, S. Aramaki, D. Moses and A. J. Heeger

      Version of Record online: 23 AUG 2007 | DOI: 10.1002/adma.200700168

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      The charge carrier transport in solution-processible copper tetrabenzoporphyrin field-effect transistors (FETs) (see figure) is studied and characterized between room temperature and 4.2 K. The insulator-to-metal transition is reached at a carrier density of 3 × 1012 cm–2, approximately independent of the source–drain voltage.

    28. The Direct Patterning of Nanoporous Interlayer Dielectric Insulator Films by Nanoimprint Lithography (pages 2919–2924)

      H. W. Ro, R. L. Jones, H. Peng, D. R. Hines, H.-J. Lee, E. K. Lin, A. Karim, D. Y. Yoon, D. W. Gidley and C. L. Soles

      Version of Record online: 29 AUG 2007 | DOI: 10.1002/adma.200602872

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      Nanoscale parallel line-space patterns are imprinted into a spin-on organosilicate thin film that contains a second phase pore generating material (porogen). Imprints are converted into nanoporous low-dielectric patterns by vitrification at 430 °C where the porogen is volatilized and creates nanoscale pores (2.2 nm) in the vitrified organosilicate network (see figure). The results are well-defined, high-modulus, nanoporous patterns with an estimated dielectric constant of k∼2.4.

    29. Structural Evidence for Zn Intersititials in Ferromagnetic Zn1–xCoxO Films (pages 2925–2929)

      J. L. MacManus-Driscoll, N. Khare, Y. Liu and M. E. Vickers

      Version of Record online: 29 AUG 2007 | DOI: 10.1002/adma.200602215

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      Post-annealing studies in different atmospheres combined with high resolution x-ray studies on epitaxial ZnO and Zn1–xCoxO films revealed that the c-axis lattice parameter decreases when interstitial zinc is removed from ZnO. The ‘c' parameter change reverses sign when samples are re-annealed in a Zn-rich atmosphere. Stronger ferromagnetism occurs in Zn1–xCoxO film for higher ‘c' parameters and hence higher Zn interstitial concentrations.

    30. Molecular Pressure Sensors (pages 2930–2934)

      H. Xu, F. C. Sun, D. G. Shirvanyants, M. Rubinstein, D. Shabratov, K. L. Beers, K. Matyjaszewski and S. S. Sheiko

      Version of Record online: 29 AUG 2007 | DOI: 10.1002/adma.200602376

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      Pressure-responsive macromolecules that change their conformation in response to variations in the film pressure can be used as model systems for studying the mechanism of the fluid transport on nanometer length scales. The ability to visualize pressure-sensitive macromolecules in motion enables quantitative measurements of the local film pressure and the friction coefficient with the substrate.

    31. Anchoring ZnO Particles on Functionalized Single Wall Carbon Nanotubes. Excited State Interactions and Charge Collection (pages 2935–2940)

      F. Vietmeyer, B. Seger and P. V. Kamat

      Version of Record online: 29 AUG 2007 | DOI: 10.1002/adma.200602773

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      A conducting scaffold of carbon nanotube architecture has been used to anchor ZnO nanoparticles. The interaction between functionalized carbon nanotubes (f-CNT) and photoexcited ZnO nanoparticles results in direct electron transfer between the two systems. The role of f-CNT in facilitating the charge collection and charge transport in the f-CNT-ZnO composite film is elucidated by photoelectrochemical measurements.

    32. A Carbon Nanomattress: A New Nanosystem with Intrinsic, Tunable, Damping Properties (pages 2941–2945)

      E. H. T. Teo, W. K. P. Yung, D. H. C. Chua and B. K. Tay

      Version of Record online: 31 AUG 2007 | DOI: 10.1002/adma.200700351

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      A new nanostructured material with tunable viscoelastic properties is fabricated using a 2D on 1D approach. The material differs from traditional carbon nanotube (CNT) re-enforced materials in that it has an integrated, hard, amorphous diamond (a-D) surface that can spread point stresses evenly to the underlying CNT supports (see figure). The film is unique in that it is both hard and wear-resistant but still maintains viscoelastic properties.

    33. Growth and Electrical Characteristics of Platinum-Nanoparticle-Catalyzed Silicon Nanowires (pages 2946–2950)

      E. C. Garnett, W. Liang and P. Yang

      Version of Record online: 31 AUG 2007 | DOI: 10.1002/adma.200700288

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      Pt nanoparticle catalysts are used to synthesize Si nanowires. The standard deviations of the starting colloid and the resulting wire diameters are essentially the same, whereas the wires were 22 % larger than the particles. The figure shows current–voltage plots of a silicon nanowire different gate voltages.

    34. Biomimetic Silica Formation: Effect of Block Copolypeptide Chemistry and Solution Conditions on Silica Nanostructure (pages 2951–2956)

      J.-S. Jan and D. F. Shantz

      Version of Record online: 29 AUG 2007 | DOI: 10.1002/adma.200602813

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      Biomimetic syntheses of silicas using block copolypeptides containing a hydrophilic lysine block are reported. Porous silica platelets or spheres can be made using block copolypeptides as templates. The results show that biomimetic synthesis under benign conditions may be a potential route for assembling nanostructured materials.

    35. The Catalytic Synthesis of Three-Dimensional Hierarchical Carbon Nanotube Composites with High Electrical Conductivity Based on Electrochemical Iron Deposition (pages 2957–2960)

      N. Li, X. Chen, L. Stoica, W. Xia, J. Qian, J. Aßmann, W. Schuhmann and M. Muhler

      Version of Record online: 31 AUG 2007 | DOI: 10.1002/adma.200602625

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      The catalytic synthesis of three-dimensional hierarchical carbon nanotube composites was based on the electrodeposition of iron and the subsequent iron-catalyzed growth of carbon nanotubes from cyclohexane. Electrochemical studies provided evidence for the strong interaction between the graphite foil, the long primary CNTs, and the short secondary CNTs, which are essential for the application of the hierarchical nanocomposite in fuel cell catalysis and in sensor systems.

    36. Long-Range Resonant Energy Transfer for Enhanced Exciton Harvesting for Organic Solar Cells (pages 2961–2966)

      S. R. Scully, P. B. Armstrong, C. Edder, J. M. J. Fréchet and M. D. McGehee

      Version of Record online: 31 AUG 2007 | DOI: 10.1002/adma.200700917

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      We present theory and experiment demonstrating a scheme to harvest singlet excitons over 25 nm away from a donor-acceptor interface using resonant energy transfer. Improvement in materials choice could yield effective diffusion lengths as large as 40 nm using long-range transfer, while minimizing the energy loss to less than 0.1 eV making this a promising approach for developing highly efficient organic photovoltaics.

    37. Surfactant-Modified Hydrophilic Nanostructured Porous Silicon for the Photosensitized Formation of Singlet Oxygen in Water (pages 2967–2972)

      V. Chirvony, A. Chyrvonaya, J. Ovejero, E. Matveeva, B. Goller, D. Kovalev, A. Huygens and P. de Witte

      Version of Record online: 31 AUG 2007 | DOI: 10.1002/adma.200602891

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      The initially hydrophobic surface of as-prepared luminescent stain-etched porous Si powder is made hydrophilic by means of the physical adsorption of different nonionic surfactants. Unsaturated linear hydrocarbons (undecylenic acid and oleyl alcohol) are found to provide the best durability of aqueous suspensions of porous Si powder, maintaining the ability of excited Si nanocrystals to interact with molecular oxygen by means of electronic energy transfer.

    38. Magnetic, Thermosensitive Microgels as Stimuli-Responsive Emulsifiers Allowing for Remote Control of Separability and Stability of Oil in Water-Emulsions (pages 2973–2978)

      B. Brugger and W. Richtering

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/adma.200700487

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      Stimuli responsive magnetic emulsions are produced by using “smart” microgels as stabilizers. The oil droplets in the emulsions are magnetic, can be separated with a static magnetic field and are destabilized by an ac magnetic field. This allows for a remote control on separation and stability of the emulsion.

    39. Controllable Synthesis of Two- Dimensional Metal Nanoparticle Arrays with Oriented Size and Number Density Gradients (pages 2979–2983)

      M. Han, C. Xu, D. Zhu, L. Yang, J. Zhang, Y. Chen, K. Ding, F. Song and G. Wang

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/adma.200602947

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      Two dimensional metal nanoparticle arrays with a size gradient (see figure) are generated by shadow deposition of a finely-collimated low energy cluster beam under an oblique incident configuration. The length of the gradient region is tunable from hundreds of nanometers to several micrometers, by adjusting the incident angle of the cluster beam. The size of the nanoparticles changes by about one order of magnitude across the gradient region.

    40. Capillarity-Driven Assembly of Carbon Nanotubes on Substrates into Dense Vertically Aligned Arrays (pages 2984–2987)

      S. Kaur, S. Sahoo, P. Ajayan and R. S. Kane

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/adma.200602883

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      Carbon nanotubes are assembled into dense, vertically aligned arrays on substrates by using capillary forces. Modulating the interactions between the nanotubes and the underlying substrate provides control over the assembly of the nanotube array; capillary forces can either cause bending (left) or translation (right) of the nanotube array. The use of this densification strategy enables a four-fold increase in current density through nanotube arrays.

    41. Thermo and pH Dual-Responsive Nanoparticles for Anti-Cancer Drug Delivery (pages 2988–2992)

      L. Zhang, R. Guo, M. Yang, X. Jiang and B. Liu

      Version of Record online: 5 SEP 2007 | DOI: 10.1002/adma.200601817

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      Thermo and pH dual-responsive nanoparticles encapsulating an anti-cancer drug (paclitaxel) were assembled from a diblock copolymer comprised of a hydrophilic poly(N-isopropylacrylamide-co-acrylic acid) block and a hydrophobic polycaprolactone block. These nanoparticles aggregated at body temperature under a slightly acidic pH of 6.9 (see figure), and a faster drug release was found to be associated with higher temperature and lower pH, both of which are advantageous for tumor-targeted anti-caner drug delivery.

    42. Nanostructure-Based Leaf-like Polyaniline in the Presence of an Amphiphilic Triblock Copolymer (pages 2993–2999)

      J. Han, G. Song and R. Guo

      Version of Record online: 5 SEP 2007 | DOI: 10.1002/adma.200602635

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      Nanostructure-based leaf-like polyaniline (PANI) (see figure) has been fabricated successfully in the presence of surfactant F127. It is found that the building blocks of leaf-like PANI can be tuned from nanofibers (ca. 25 nm in diameter) to nanotubes (ca. 100 nm in diameter) with increasing monomer concentration. The proposed synthetic method will provide insight into the synthesis of oriented nanostructures of polymer materials by the soft-template strategy.

    43. Effect of Generation and Soft Lithography on Semiconducting Dendrimer Lasers (pages 3000–3003)

      J. R. Lawrence, E. B. Namdas, G. J. Richards, P. L. Burn and I. D. W. Samuel

      Version of Record online: 5 SEP 2007 | DOI: 10.1002/adma.200602392

      Thumbnail image of graphical abstract

      Conjugated dendrimers are promising optoelectronic materials as their modular architecture enables independent tuning of the optical, electronic, and processing properties. Dendrimer distributed feedback lasers are demonstrated, and an improvement in slope efficiency from 0.3 % to 1.6 % is seen as the dendrimer generation is increased. Simple fabrication of the lasers by soft lithography is also shown, giving a high slope efficiency of 14 %. The combination of high efficiency dendrimer gain media and soft lithographic fabrication techniques makes conjugated dendrimers attractive materials for organic semiconductor lasers.

    44. Novel Structure of AAO Film Fabricated by Constant Current Anodization (pages 3004–3007)

      S. Zhao, K. Chan, A. Yelon and T. Veres

      Version of Record online: 5 SEP 2007 | DOI: 10.1002/adma.200701284

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      AAO films with a novel six-membered ring structure were prepared by constant current anodization. The six-membered ring contains smaller pores, formed at the triple junction sites of the larger pores. The interpore distance was reduced from the usual 85 nm to 50 nm, doubling the usual pore density. These novel AAO film structures with high pore density may have applications in the preparation of mosaic nanowire arrays and photonic devices.

    45. High-Performance Field-Effect Transistor Based on Dibenzo[d,d′]thieno[3,2-b;4,5-b′]dithiophene, an Easily Synthesized Semiconductor with High Ionization Potential (pages 3008–3011)

      J. H. Gao, R. J. Li, L. Q. Li, Q. Meng, H. Jiang, H. X. Li and W. P. Hu

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/adma.200701167

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      Three simple, controlled steps are all it takes to synthesize the title pentacene analogue DBTDT (see figure). The material's high ionization potential, high thermal and photostability, high mobilities, and an on/off ratio larger than 106 at a substrate temperature of ca. 36 °C, as reported here, suggest that DBTDT will be extremely valuable for applications in plastic organic electronics.

    46. Low-Temperature Epitaxial Growth of Vertical In2O3 Nanowires on A-Plane Sapphire with Hexagonal Cross-Section (pages 3012–3015)

      C.-J. Chen, W.-L. Xu and M.-Y. Chern

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/adma.200602764

      Thumbnail image of graphical abstract

      Epitaxial growth of vertical In2O3 (111) nanowires with hexagonal cross-section on a-plane sapphire is reported. The figure showing the vertical wires is viewed at 45° from the substrate normal. These wires taper gradually towards the tops and they start to bend near the tips. Because of the low-temperature growth, the wires possess a new hexagonal symmetry and a shortest photoluminescence wavelength among those that have been reported for In2O3 nanowires.

    47. Mesoporous Titania Nanotubes: Their Preparation and Application as Electrode Materials for Rechargeable Lithium Batteries (pages 3016–3020)

      K. Wang, M. Wei, M. A. Morris, H. Zhou and J. D. Holmes

      Version of Record online: 6 SEP 2007 | DOI: 10.1002/adma.200602189

      Thumbnail image of graphical abstract

      Mesoporous titania nanotubes with tunable dimension have been fabricated within the pores of alumina membranes by a simple sol-gel templating method. The 3D network structures of these mesoporous nanotubes (see figure) can provide both electron pathway and lithium ion pathway which benefit their applications in a high rate rechargeable lithium battery.

    48. Space-Confined Formation of FePt Nanoparticles in Ordered Mesoporous Silica SBA-15 (pages 3021–3026)

      E. Kockrick, P. Krawiec, W. Schnelle, D. Geiger, F. M. Schappacher, R. Pöttgen and S. Kaskel

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/adma.200601367

      Thumbnail image of graphical abstract

      FePt nanoparticles inside ordered mesoporous silica SBA-15 were synthesized via incipient wetness impregnation and subsequent thermal treatments in reductive atmosphere. The porous matrix is used to prevent sintering and agglomeration during the fcc–FePt to fct–FePt phase transition. According to magnetic measurements and Mössbauer spectroscopic studies, the resulting FePt@SBA-15 composites are ferromagnetic.

    49. Filling of TiO2 Nanotubes by Self-Doping and Electrodeposition (pages 3027–3031)

      J. M. Macak, B. G. Gong, M. Hueppe and P. Schmuki

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/adma.200602549

      Thumbnail image of graphical abstract

      A highly efficient approach for metal filling of TiO2nanotube layers is demonstrated. Electrochemical self-doping is used to switch selectively the bottom of TiO2 nanotubes into a conductive state. Subsequent metal electrodeposition therefore starts at the tube bottom and continues in a homogenous and controllable manner up the tubes. The approach essentially allows to deposit all material classes into TiO2 nanotubes and therefore provides the basis for a large variety of functional TiO2 nanotubes – composite materials.

    50. A Controllable Nanometer-Sized Valve (pages 3032–3036)

      M. Yu, J. L. Falconer, T. J. Amundsen, M. Hong and R. D. Noble

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/adma.200602774

      Thumbnail image of graphical abstract

      The effect of a MFI membrane nanostructure change on n-hexane/ 2,2-dimethylbutane (DMB) permeation is described. The figure shows a) DMB transporting through the defects in an empty membrane, b) DMB permeation is blocked due to the initial defects closing by crystal expansion by n-hexane, c) both n-hexane and DMB permeation are blocked when the membrane is exposed to DMB first. The pores shrink and trap DMB so that almost all transport is blocked.

    51. Dibenzotetrathiafulvalene Bisimides: New Building Blocks for Organic Electronic Materials** (pages 3037–3042)

      X. K. Gao, Y. Wang, X. D. Yang, Y. Q. Liu, W. F. Qiu, W. P. Wu, H. J. Zhang, T. Qi, Y. Liu, K. Lu, C. Y. Du, Z. G. Shuai, G. Yu and D. B. Zhu

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/adma.200700007

      Thumbnail image of graphical abstract

      A new class of organic species, dibenzotetrathiafulvalene bisimides (see figure), were designed and synthesized by using a facile and general synthetic strategy. The new bisimides possess a diverse library of derivatives with various functionalities at the imide rings, and they show promise for use in a range of organic electronic applications.

    52. A Supercritical-Fluid Method for Growing Carbon Nanotubes (pages 3043–3046)

      Z. Li, J. Andzane, D. Erts, J. M. Tobin, K. Wang, M. A. Morris, G. Attard and J. D. Holmes

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/adma.200602483

      Thumbnail image of graphical abstract

      Large-scale generation of multiwalled carbon nanotubes (MCNTs) is efficiently achieved through a supercritical fluid technique employing carbon dioxide as the carbon source. Nanotubes with diameters ranging from 10 to 20 nm and lengths of several tens of micrometers are synthesized (see figure). The supercritical-fluid-grown nanotubes also exhibit field-emission characteristics similar to MCNTs grown by chemical-vapor deposition.

    53. Synthesis and Thermoelectrical Characterization of Lead Chalcogenide Nanowires (pages 3047–3051)

      M. Fardy, A. I. Hochbaum, J. Goldberger, M. M. Zhang and P. Yang

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/adma.200602674

      Thumbnail image of graphical abstract

      Single-crystalline arrays of PbS, PbSe, and PbTe nanowires (Figure: PbS) with diameters ranging from 40-200 nm and lengths up to 100 μm have been synthesized by a chemical vapor transport approach. Electrical and thermal characterization was performed to investigate their potential as thermoelectric materials. Compared to bulk, the nanowires exhibit reduced thermal conductivity below 100 K by up to 3 orders of magnitude, suggesting that they may be promising thermoelectric materials.

    54. Polymer-Based Photonic Crystals Fabricated with Single-Step Electron-Beam Lithography (pages 3052–3056)

      C.-S. Wu, C.-F. Lin, H.-Y. Lin, C.-L. Lee and C.-D. Chen

      Version of Record online: 31 AUG 2007 | DOI: 10.1002/adma.200602471

      Thumbnail image of graphical abstract

      A suspended PMMA quasi-3D PC slab with a hexagonal array of air holes fabricated by using a single-step electron-beam lithography process is shown in the figure (PMMA = polymethylmethacrylate). The extension of the single-step lithography technique to the fabrication of 3D multilayer nanostructures with photonic band gaps in the visible-light region is demonstrated.

  6. Index

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Contents
    5. Review
    6. Communications
    7. Index

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