Advanced Materials

Cover image for Vol. 18 Issue 11

June, 2006

Volume 18, Issue 11

Pages 1335–1478

    1. Cover Picture: Using a Core–Sheath Distribution of Surface Chemistry through 3D Tissue Engineering Scaffolds to Control Cell Ingress (Adv. Mater. 11/2006)

      J. J. A. Barry, D. Howard, K. M. Shakesheff, S. M. Howdle and M. R. Alexander

      Version of Record online: 29 MAY 2006 | DOI: 10.1002/adma.200690045

      A core/sheath distribution of cell-adhesive and non-cell-adhesive surface coatings is produced in porous biodegradable poly(D,L-lactic acid) discs using sequential plasma polymerization. The figure and cover show an X-ray micro-computed tomography image of a section of a 10 mm diameter, 4 mm thick scaffold where fibroblast cells (shown in red) have been encouraged by the surface chemistry to penetrate to the scaffold core.

    2. Inside Front Cover: Rigid, Self-Assembled Hydrogel Composed of a Modified Aromatic Dipeptide (Adv. Mater. 11/2006)

      A. Mahler, M. Reches, M. Rechter, S. Cohen and E. Gazit

      Version of Record online: 29 MAY 2006 | DOI: 10.1002/adma.200690046

      A simple dipeptide self-assembles into a biocompatible hydrogel (see figure and inside cover). This novel biomaterial is extremely simple to prepare and has a remarkable rigidity. It is very stable under extreme conditions, can be injected, and can be shaped according to the vessel it has been assembled in. The hydrogel allows a wide variety of possible biomedical applications including tissue engineering, axonal regeneration, and controlled drug release.

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    4. Hydrogels in Biology and Medicine: From Molecular Principles to Bionanotechnology (pages 1345–1360)

      N. A. Peppas, J. Z. Hilt, A. Khademhosseini and R. Langer

      Version of Record online: 29 MAY 2006 | DOI: 10.1002/adma.200501612

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      The science and theory of hydrogels as well as their biomedical applications are reviewed. Their thermodynamic properties, theory, and types of hydrogels are discussed, and examples of their use for therapeutic and diagnostics applications are given. Future directions and challenges in the synthesis and use of hydrogels are also outlined. The figure shows the formation of a fluorescent hydrogel gradient using a microfluidic system (inlet channels diameter: 80 μm).

    5. Control over the Crystalline State of Sapphire (pages 1361–1364)

      S. Juodkazis, K. Nishimura, H. Misawa, T. Ebisui, R. Waki, S. Matsuo and T. Okada

      Version of Record online: 12 APR 2006 | DOI: 10.1002/adma.200501837

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      Amorphous regions in sapphire with sub-micrometer 3D resolution have been produced at the focus of a single femtosecond laser pulse. Crystalline- to-amorphous and amorphous-to-polycrystalline transitions (crystalline and amorphous regions are marked C and A in the HRTEM image) are induced by single- and multi-pulse irradiation, respectively. The wet-etching selectivity for the amorphous phase is significantly greater than that for the crystalline phase in aqueous HF.

    6. Rigid, Self-Assembled Hydrogel Composed of a Modified Aromatic Dipeptide (pages 1365–1370)

      A. Mahler, M. Reches, M. Rechter, S. Cohen and E. Gazit

      Version of Record online: 25 APR 2006 | DOI: 10.1002/adma.200501765

      Thumbnail image of graphical abstract

      A simple dipeptide self-assembles into a biocompatible hydrogel (see figure and inside cover). This novel biomaterial is extremely simple to prepare and has a remarkable rigidity. It is very stable under extreme conditions, can be injected, and can be shaped according to the vessel it has been assembled in. The hydrogel allows a wide variety of possible biomedical applications including tissue engineering, axonal regeneration, and controlled drug release.

    7. Phase Separation of Polyfluorene-Based Blend Films and Its Influence on Device Operations (pages 1371–1376)

      Y. Xia and R. H. Friend

      Version of Record online: 26 APR 2006 | DOI: 10.1002/adma.200502338

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      Vertical phase separations have been found in blend films (TFB:F8BT) of polymer light-emitting diodes, giving rise to better device performances. A TFB wetting layer is present over most of the bottom interface with the substrate, as evidenced by the fluorescent microscopy images after top layers are etched away by oxygen plasma (see figure).

    8. Kinetics and Mechanism of Atomic Force Microscope Local Oxidation on Hydrogen-Passivated Silicon in Inert Organic Solvents (pages 1377–1380)

      C. R. Kinser, M. J. Schmitz and M. C. Hersam

      Version of Record online: 24 APR 2006 | DOI: 10.1002/adma.200501231

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      Conductive atomic force microscope (AFM) nanopatterning on hydrogen-terminated silicon in a hydrophobic organic solvent under ambient conditions produces features consistent with AFM field-induced oxidation. The growth rate of the oxide features (see figure) exhibits modulation consistent with a space-charge-limited growth mechanism.

    9. Using a Layer-by-Layer Assembly Technique to Fabricate Multicolored-Light-Emitting Films of CdSe@CdS and CdTe Quantum Dots (pages 1381–1386)

      Y.-W. Lin, W.-L. Tseng and H.-T. Chang

      Version of Record online: 24 APR 2006 | DOI: 10.1002/adma.200502515

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      The tunability of the colors and emissions of quantum-dot (QD) films—by controlling the deposition order and number of bilayers in (PDDA–CdSe@CdS)n and (PDDA–CdTe)n films (PDDA: poly(diallyldimethylammonium chloride))—is demonstrated. The photograph shows QD microstructures that exhibit different emission colors on a gold nanoparticle (AuNP)-treated indium tin oxide substrate, fabricated by combining layer-by-layer assembly with photolithography.

    10. Self-Assembly Process to Integrate and Connect Semiconductor Dies on Surfaces with Single-Angular Orientation and Contact-Pad Registration (pages 1387–1392)

      W. Zheng and H. O. Jacobs

      Version of Record online: 26 APR 2006 | DOI: 10.1002/adma.200502026

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      A directed self-assembly process to batch assemble differently sized components with single angular orientation on surfaces is demonstrated. This process employs “two-element docking sites” on the substrate that contain alignment pedestals and solder-coated areas that are designed according to the size and shape of the components. The directed assembly of one hundred silicon blocks (see figure), 900 and 500 μm in size, is demonstrated with 19 μm lateral and 0.3° angular contact-pad registration accuracy.

    11. Protein-Coated Porous-Silicon Photonic Crystals for Amplified Optical Detection of Protease Activity (pages 1393–1396)

      M. M. Orosco, C. Pacholski, G. M. Miskelly and M. J. Sailor

      Version of Record online: 28 APR 2006 | DOI: 10.1002/adma.200502420

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      An optical biosensor for protease activity, capable of detecting picomole quantities of protease, is constructed from a 1D photonic crystal of porous Si. The porous Si layer is coated with a thin film of zein, a natural hydrophobic protein. Proteolytic cleavage produces small fragments that infiltrate the pores of the photonic crystal, producing a distinct color change (see figure). The amount of protease pepsin used on each of the spots is indicated.

    12. Reversible Conductance Switching of Single Diarylethenes on a Gold Surface (pages 1397–1400)

      N. Katsonis, T. Kudernac, M. Walko, S. J. van der Molen, B. J. van Wees and B. L. Feringa

      Version of Record online: 5 MAY 2006 | DOI: 10.1002/adma.200600210

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      Light-controlled conductance switching of diarylethenes attached to Au(111) is reported (see figure). First, scanning tunneling microscopy is used to demonstrate reversible photoswitching for individual molecules. Second, reversible switching in self-assembled monolayers is established by means of optical spectroscopy.

    13. Electromechanical Polymer Gels Combining Rubber Elasticity with Electronic Conduction (pages 1401–1405)

      B. Pépin-Donat, A. Viallat, J.-F. Blachot and C. Lombard

      Version of Record online: 5 MAY 2006 | DOI: 10.1002/adma.200501418

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      Well-controlled electrically conducting rubbers are ideal systems for addressing longstanding questions about intrachain electronic transport mechanisms, intractable for classical conducting polymers except at a very local scale. These doped gels permit observation of macroscopic electromechanical effects, such as changes in strain (τ) upon application of electric fields (see plot), resulting from molecular-scale coupling between transport and chain-conformational properties.

    14. Using a Core–Sheath Distribution of Surface Chemistry through 3D Tissue Engineering Scaffolds to Control Cell Ingress (pages 1406–1410)

      J. J. A. Barry, D. Howard, K. M. Shakesheff, S. M. Howdle and M. R. Alexander

      Version of Record online: 26 APR 2006 | DOI: 10.1002/adma.200502719

      Thumbnail image of graphical abstract

      A core/sheath distribution of cell-adhesive and non-cell-adhesive surface coatings is produced in porous biodegradable poly(D,L-lactic acid) discs using sequential plasma polymerization. The figure and cover show an X-ray micro-computed tomography image of a section of a 10 mm diameter, 4 mm thick scaffold where fibroblast cells (shown in red) have been encouraged by the surface chemistry to penetrate to the scaffold core.

    15. Porphyrin Molecular Nanodevices Wired Using Single-Walled Carbon Nanotubes (pages 1411–1415)

      H. Tanaka, T. Yajima, T. Matsumoto, Y. Otsuka and T. Ogawa

      Version of Record online: 26 APR 2006 | DOI: 10.1002/adma.200501249

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      The electronic properties of porphyrin zinc aggregates wired using single-walled carbon nanotubes (SWNTs) are described. A self-assembled structure is formed by casting a solution of SWNTs and 5,15-bispentylporphyrinato zinc(II) (BPP-Zn) onto a substrate (see figure). Rectifying behavior has been observed at SWNT/BPP-Zn junctions, although no rectification is seen for bare SWNTs. The results show that aggregates of even a few BPP-Zn molecules work as a rectifying device with SWNT wiring.

    16. High-Mobility Ambipolar Transport in Organic Light-Emitting Transistors (pages 1416–1420)

      F. Dinelli, R. Capelli, M. A. Loi, M. Murgia, M. Muccini, A. Facchetti and T. J. Marks

      Version of Record online: 24 APR 2006 | DOI: 10.1002/adma.200502164

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      Organic light-emitting transistors based on bilayered structures (see figure) exhibit balanced ambipolar transport and mobility values as large as 3 × 10–2 cm2 V–1 s–1. The best performances are realized by sequentially depositing α,ω-dihexyl-quaterthiophene (DH4T) as p-type and N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13) as n-type materials. Laser-scanning confocal microscopy allows selective imaging of the layers.

    17. High Lithium Electroactivity of Nanometer-Sized Rutile TiO2 (pages 1421–1426)

      Y.-S. Hu, L. Kienle, Y.-G. Guo and J. Maier

      Version of Record online: 10 APR 2006 | DOI: 10.1002/adma.200502723

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      Nanometer-sized rutile shows much higher electroactivity towards Li insertion than micrometer-sized rutile. Up to 0.8 mol of Li per mole of TiO2 can be inserted into nanometer-sized rutile at room temperature (see figure), which is able to reversibly accommodate Li up to Li0.5TiO2 with excellent capacity retention and high rate capability on cycling, rendering it a promising anode material for high-power lithium-ion batteries.

    18. Solution and Surface Composition Gradients via Microfluidic Confinement: Fabrication of a Statistical-Copolymer-Brush Composition Gradient (pages 1427–1430)

      C. Xu, S. E. Barnes, T. Wu, D. A. Fischer, D. M. DeLongchamp, J. D. Batteas and K. L. Beers

      Version of Record online: 19 APR 2006 | DOI: 10.1002/adma.200502341

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      A stable solution composition gradient is generated inside a microchannel by varying the relative flow rates of two solutions that differ in composition. This solution gradient is used to synthesize a surface-grafted statistical-copolymer-brush composition gradient via surface-initiated atom transfer radical polymerization (ATRP; see schematic). Near-edge absorption fine structure spectroscopy confirms the continuous transition of surface composition from one end of the substrate to the other.

    19. Testing Carbon-Coated VOx Prepared via Reaction under Autogenic Pressure at Elevated Temperature as Li-Insertion Materials (pages 1431–1436)

      A. Odani, V. G. Pol, S. V. Pol, M. Koltypin, A. Gedanken and D. Aurbach

      Version of Record online: 24 APR 2006 | DOI: 10.1002/adma.200501611

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      V2O3 nanoparticles covered by a 15 nm thick uniform carbon coating are prepared by reaction under autogenic pressure at elevated temperature of VO(OC2H5)3 at 700 °C. Further oxidation of this material produces carbon-coated V2O5 nanoparticles. Both materials reversibly insert Li (see figure) electrochemically in nonaqueous Li-salt solutions.

    20. Vapor-Phase Synthesis and Characterization of ϵ-FeSi Nanowires (pages 1437–1440)

      L. Ouyang, E. S. Thrall, M. M. Deshmukh and H. Park

      Version of Record online: 26 APR 2006 | DOI: 10.1002/adma.200502721

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      Single-stem and branched ϵ-FeSi nanowires with diameters ranging from 5 to 100 nm (see figure) are synthesized using a chemical vapor deposition method. These nanowires, including branches, are single crystalline and exhibit a cubic structure with [111] growth direction. Electrical and magnetic measurements show that these nanowires exhibit properties consistent with those of the bulk material, with branch-induced charge-carrier introduction playing an important role.

    21. Fabrication of a Superhydrophobic Surface from the Amplified Exponential Growth of a Multilayer (pages 1441–1444)

      J. Ji, J. Fu and J. Shen

      Version of Record online: 26 APR 2006 | DOI: 10.1002/adma.200502453

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      Hierarchical micro- and nanostructures can be produced simultaneously by the novel layer-by-layer assembly described here. The multilayer films, grown by an exponential growth mechanism that can be amplified by adding silver ions, showed extreme hydrophobicity and a lotus-leaf-like amplification of the surface roughness. The figure clearly demonstrates the superhydrophobic nature of the multilayer film.

      Corrected by:

      Correction: Self-Assembled Electroluminescent Polymers Derived from Terpyridine-Based Moieties

      Vol. 19, Issue 13, 1662, Version of Record online: 26 JUN 2007

      Corrected by:

      Correction: Fabrication of a Superhydrophobic Surface from the Amplified Exponential Growth of a Multilayer

      Vol. 19, Issue 18, 2411, Version of Record online: 10 SEP 2007

    22. Large Electric Polarization and Exchange Bias in Multiferroic BiFeO3 (pages 1445–1448)

      J. Dho, X. Qi, H. Kim, J. L. MacManus-Driscoll and M. G. Blamire

      Version of Record online: 26 APR 2006 | DOI: 10.1002/adma.200502622

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      Low-leakage BiFeO3 films have been grown with saturated ferroelectric hysteresis loops (see figure) and a very large remanent polarization. The antiferromagnetic nature of BiFeO3 films is confirmed by the appearance of an exchange bias in BiFeO3-based spin-valve multilayers. The results imply that there is potential for room-temperature applications of BiFeO3 that combine ferroelectric and antiferromagnetic functionality.

    23. Defect-Induced Ferromagnetism in Co-doped ZnO (pages 1449–1452)

      N. Khare, M. J. Kappers, M. Wei, M. G. Blamire and J. L. MacManus-Driscoll

      Version of Record online: 5 MAY 2006 | DOI: 10.1002/adma.200502200

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      A novel soft-solution technique is used to grow epitaxial Zn0.98Co0.02O films on the c-plane (0001) of a single-crystal sapphire substrate. Annealing the films in precisely controlled atmospheres shows that the ferromagnetism is not linked to the carrier-concentration density. Undertaking cyclic annealing studies in the presence or absence of Zn vapor (see figure) shows that Zn interstitials but not oxygen vacancies are the critical defects for inducing ferromagnetism.

    24. Fast and Spatially Resolved Environmental Probing Using Stimuli-Responsive Polymer Layers and Fluorescent Nanocrystals (pages 1453–1457)

      L. Ionov, S. Sapra, A. Synytska, A. L. Rogach, M. Stamm and S. Diez

      Version of Record online: 26 APR 2006 | DOI: 10.1002/adma.200502686

      Thumbnail image of graphical abstract

      Stimuli-responsive polymer brushes with adsorbed fluorescent semiconductor nanocrystals can be used in solvent-sensitive sensors based on the fluorescence-interference contrast (see figure) of semiconductor nanocrystals near a reflecting silicon surface. The reversible, solvent-depending swelling of a thin, surface-anchored film of poly(2-vinyl pyridine) using hydrophobic CdSeS nanocrystals leads to a high temporal and spatial resolution of the fluorescence images.

    25. Periodical Variation of Electronic Properties in Polyhydroxylated Metallofullerene Materials (pages 1458–1462)

      J. Tang, G. Xing, Y. Zhao, L. Jing, X. Gao, Y. Cheng, H. Yuan, F. Zhao, Z. Chen, H. Meng, H. Zhang, H. Qian, R. Su and K. Ibrahim

      Version of Record online: 26 APR 2006 | DOI: 10.1002/adma.200600049

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      Polyhydroxylation of metallofullerenes can control the direction and intensity of electron transfer between the innermost Gd and the outer carbon cage. The synergistic effect efficiently modulates the strong exchange interactions or coupling between the different electron levels of the innermost metallic atoms, leading to a periodical occurrence of energy level splitting and novel electronic properties in the 4f atom (see figure).

    26. Alginate-Based Nanofibrous Scaffolds: Structural, Mechanical, and Biological Properties (pages 1463–1467)

      N. Bhattarai, Z. Li, D. Edmondson and M. Zhang

      Version of Record online: 26 APR 2006 | DOI: 10.1002/adma.200502537

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      Alginate-based nanofibers with an average diameter of ca. 75 nm (see figure) have been fabricated by electrospinning. The nanofiber network has mechanical properties comparable to cartilage. The cellular compatibility is demonstrated with chondrocytes. This natural polymer-based nanofiber network may find application in tissue engineering and regenerative medicine.

    27. Thin Films of Metallic Carbon Nanotubes Prepared by Dielectrophoresis (pages 1468–1470)

      R. Krupke, S. Linden, M. Rapp and F. Hennrich

      Version of Record online: 24 APR 2006 | DOI: 10.1002/adma.200600134

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      Dielectrophoretic separation of metallic carbon nanotubes from semiconducting carbon nanotubes is developing towards a bulk-separation method, which allows, for the first time, the production of thin films of only metallic single-walled carbon nanotubes on a transparent quartz-glass substrate (see figure). Larger quantities of nanotubes are processed without sacrificing the intrinsic high quality of the process–a development that is promising for the development of nanotube-based electronic-device applications.

    28. Polymers Move in Response to Light (pages 1471–1475)

      H. Y. Jiang, S. Kelch and A. Lendlein

      Version of Record online: 5 MAY 2006 | DOI: 10.1002/adma.200502266

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      Polymers move in response to light when photosensitive molecules are incorporated into suitable polymer architectures in combination with tailored functionalization processes. Selected examples for polymer systems that contract, bend, or change in volume are highlighted. Special attention is focused on light-induced shape-memory polymers that are able to recover their original shape from a temporarily fixed new shape (see figure).

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