Advanced Materials

Cover image for Vol. 19 Issue 15

August, 2007

Volume 19, Issue 15

Pages 1887–2028

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Review
    5. Communications
    6. Index
    1. Cover Picture: Preparation of Highly Luminescent Nanocrystals and Their Application to Light-Emitting Diodes (Adv. Mater. 15/2007)

      J. Lim, S. Jun, E. Jang, H. Baik, H. Kim and J. Cho

      Article first published online: 27 JUL 2007 | DOI: 10.1002/adma.200790056

      Thumbnail image of graphical abstract

      Core/multishell-structured semiconductor nanocrystals (NCs) are prepared in multigram amounts through a one-pot process without a core-separation step (see figure and cover). The NCs show a maximum quantum efficiency of 85 % at a controlled wavelength and strong photostability against UV-light bleaching. The NCs are applied as phosphors on UV-light-emitting diodes (390 nm source), which emit light at 620 nm with a 48 % power conversion efficiency.

  2. Contents

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Review
    5. Communications
    6. Index
    1. Contents: Adv. Mater. 15/2007 (pages 1887–1895)

      Article first published online: 27 JUL 2007 | DOI: 10.1002/adma.200790054

  3. Review

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Review
    5. Communications
    6. Index
    1. Inorganic Semiconductors for Flexible Electronics (pages 1897–1916)

      Y. Sun and J. A. Rogers

      Article first published online: 12 JUL 2007 | DOI: 10.1002/adma.200602223

      Thumbnail image of graphical abstract

      Various classes of inorganic semiconductors can be grown into high-quality thin films to serve as channels of high-performance thin-film transistors (TFTs) fabricated on flexible plastic substrates, which are referred to as macroelectronics. The image shows an example of an array of TFTs built with GaAs ribbons on a thin polyurethane sheet laminated on the surface of a glass rod with diameter of 7 mm (with electrical characterization). This Review describes progress in this emerging area.

  4. Communications

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Review
    5. Communications
    6. Index
    1. Ultrafine Multilayers of Complex Metal Oxide Films (pages 1917–1920)

      T. G. Holesinger, Q. Jia, B. Maiorov, L. Civale, P. C. Dowden and B. J. Gibbons

      Article first published online: 26 JUN 2007 | DOI: 10.1002/adma.200602743

      Thumbnail image of graphical abstract

      Thick films containing ultrafine multilayer structures of two complex metal oxides are grown with a single, sectored target in conjunction with pulsed laser deposition on stationary or moving templates. This process is demonstrated with the high-temperature superconductors YBa2Cu3Oy and EuBa2Cu3Oy. Multilayer periodicities (see figure) as low as 5.5 nm (approximately five unit cells) are obtained in thick films (1.84 μm ≈ 335 bilayer pairs) with improved superconducting properties.

    2. Two-Photon Excitation of Quantum-Dot-Based Fluorescence Resonance Energy Transfer and Its Applications (pages 1921–1926)

      A. R. Clapp, T. Pons, I. L. Medintz, J. B. Delehanty, J. S. Melinger, T. Tiefenbrunn, P. E. Dawson, B. R. Fisher, B. O'Rourke and H. Mattoussi

      Article first published online: 26 JUN 2007 | DOI: 10.1002/adma.200602036

      Thumbnail image of graphical abstract

      Nonradiative fluorescence resonance energy transfer (FRET) between a luminescent quantum dot (QD) donor and a proximal dye brought in close proximity of the QD surface via conjugation with a dye-labeled peptide (or a protein) is shown (see figure). The system is excited with near IR irradiation (well below the absorption band of the QD), via a fast two-photon process, which produces a FRET signal with very low background contribution due to a substantially reduced nonlinear direct excitation of the dye.

    3. Preparation of Highly Luminescent Nanocrystals and Their Application to Light-Emitting Diodes (pages 1927–1932)

      J. Lim, S. Jun, E. Jang, H. Baik, H. Kim and J. Cho

      Article first published online: 29 JUN 2007 | DOI: 10.1002/adma.200602642

      Thumbnail image of graphical abstract

      Core/multishell-structured semiconductor nanocrystals (NCs) are prepared in multigram amounts through a one-pot process without a core-separation step (see figure and cover). The NCs show a maximum quantum efficiency of 85 % at a controlled wavelength and strong photostability against UV-light bleaching. The NCs are applied as phosphors on UV-light-emitting diodes (390 nm source), which emit light at 620 nm with a 48 % power conversion efficiency.

    4. Graded-Bandgap Quantum- Dot-Modified Nanotubes: A Sensitive Biosensor for Enhanced Detection of DNA Hybridization (pages 1933–1936)

      C.-L. Feng, X.   H. Zhong, M. Steinhart, A.-M. Caminade, J.-P. Majoral and W. Knoll

      Article first published online: 29 JUN 2007 | DOI: 10.1002/adma.200602311

      Thumbnail image of graphical abstract

      Highly sensitive detection of DNA hybridization is demonstrated for the functionalized nanotubes (NTs) described here. With a cascaded-energy-transfer architecture produced by depositing, layer-by-layer, three types of ZnxCd1–xSe alloy quantum dots (QDs)—that is, graded-bandgap QDs—into ordered porous alumina membranes (see figure), the NTs provide the ability to detect small but significant changes in the signal during biological detection.

    5. Copper-Filled Carbon Nanotubes: Rheostatlike Behavior and Femtogram Copper Mass Transport (pages 1937–1942)

      D. Golberg, P. M. F. J. Costa, M. Mitome, S. Hampel, D. Haase, C. Mueller, A. Leonhardt and Y. Bando

      Article first published online: 29 JUN 2007 | DOI: 10.1002/adma.200700126

      Thumbnail image of graphical abstract

      Copper-filled carbon nanotubes can electrically be probed and engineered (see figure) inside a high-resolution transmission electron microscope using a piezo-driven stage. Unique switchlike or rheostatlike electrical behavior and electrical-driven copper femtogram mass transport within nanotubes is shown.

    6. Generation of Sub-micrometer-scale Patterns by Successive Miniaturization Using Hydrogels (pages 1943–1946)

      A. Lal Das, R. Mukherjee, V. Katiyer, M. Kulkarni, A. Ghatak and A. Sharma

      Article first published online: 27 JUN 2007 | DOI: 10.1002/adma.200602681

      Thumbnail image of graphical abstract

      Macroscopic to sub-micrometer-scale patterns and objects are generated by successive miniaturization of an original pattern using the volume-shrinking characteristics of hydrogels. A pattern from a stamp is transferred onto a hydrogel block, which is then dried to shrink its size. The shrunk pattern is subsequently transferred to a polymer stamp, which can be used as master for the next cycle. The figure shows the shrinking of the patterns of a CD (left) and a DVD (right).

    7. Direct Nanopatterning of 3D Chemically Active Structures for Biological Applications (pages 1947–1950)

      F. Brétagnol, A. Valsesia, T. Sasaki, G. Ceccone, P. Colpo and F. Rossi

      Article first published online: 2 JUL 2007 | DOI: 10.1002/adma.200602523

      Thumbnail image of graphical abstract

      A direct-writing technique that allows the fabrication of 3D chemically active nanostructures by combining low- pressure plasma polymerization with an electron-beam process is reported. The figure shows functional nanopillars consisting of acrylic acid (carboxylic acid moieties) on a protein-repellent layer of poly(ethylene glycol). The versatility of the structuring process makes it a promising tool for probing biological systems at the nanoscale.

    8. DNA-Based Self-Sorting of Nanoparticles on Gold Surfaces (pages 1951–1956)

      U. Plutowski, S. S. Jester, S. Lenhert, M. M. Kappes and C. Richert

      Article first published online: 2 JUL 2007 | DOI: 10.1002/adma.200602169

      Thumbnail image of graphical abstract

      Site-selective deposition of nanoparticles onto surfaces is desirable for the fabrication of nanoscale devices. For nanoparticles with vastly different numbers of DNA chains on their surfaces, multivalent binding of short-sequence motifs and nonspecific adsorption complicate sequence-specific immobilization from mixtures. A new nanoparticle coating method that suppresses salt-induced aggregation and undesirable binding events is reported. Size-selective sorting of gold nanoparticles up to 60 nm diameter onto nanopatterned surfaces is shown (see figure).

    9. Yielding of Metallic Glass Foam by Percolation of an Elastic Buckling Instability (pages 1957–1962)

      M. D. Demetriou, J. C. Hanan, C. Veazey, M. Di Michiel, N. Lenoir, E. Üstündag and W. L. Johnson

      Article first published online: 12 JUL 2007 | DOI: 10.1002/adma.200602136

      Thumbnail image of graphical abstract

      Real-time X-ray microtomography is used to study the underlying mechanisms of the yielding and collapse of a closed-cell metallic glass foam (see figure). Intercellular and intracellular deformations upon compressive loading are examined in situ. A shear-stability analysis reveals that glassy foams obey the same universal yield criterion as zero-temperature glasses, suggesting a link between the floppy modes in a glass and the buckling instabilities in a stochastic cellular structure.

    10. Improved Electrode Performance of Porous LiFePO4 Using RuO2 as an Oxidic Nanoscale Interconnect (pages 1963–1966)

      Y.-S. Hu, Y.-G. Guo, R. Dominko, M. Gaberscek, J. Jamnik and J. Maier

      Article first published online: 11 JUL 2007 | DOI: 10.1002/adma.200700697

      Thumbnail image of graphical abstract

      By using nanometer-sized RuO2 to “metalize” tiny pores and even “repair” incomplete electronically conducting (carbon) networks in porous carbon-containing LiFePO4 (see figure), the kinetics and rate capability of the composite are significantly improved. The key lies in the bonding properties of RuO2, which enables good contact to both the oxidic storage material as well as the carbon structures used as current collector.

    11. Solid-Supported Multicomponent Patterned Monolayers (pages 1967–1972)

      D. Rhinow and N. A. Hampp

      Article first published online: 11 JUL 2007 | DOI: 10.1002/adma.200602387

      Thumbnail image of graphical abstract

      Submerged laser ablation is used to obtain multicomponent, patterned alkanethiol monolayers on template-stripped gold. In a decanethiol (DT) self-assembled monolayer first squares of mercaptoundecanoic acid (MUA) and then lines comprising of hexadecanethiol (HDT) were prepared. The patterned monolayers are imaged by scanning electron microscopy (see figure).

    12. Patterned Surfaces with Pillars with Controlled 3D Tip Geometry Mimicking Bioattachment Devices (pages 1973–1977)

      A. del Campo, C. Greiner, I. Álvarez and E. Arzt

      Article first published online: 12 JUL 2007 | DOI: 10.1002/adma.200602476

      Thumbnail image of graphical abstract

      Structured surfaces with 3D pillars with different geometries resembling those found in biological-attachment devices are microfabricated and their adhesion performance is tested (see figure). This work provides the first experimental evidence of the influence of the contact shape on the adhesion of structured surfaces and paves the road to a better understanding of biological-attachment systems and to optimum designs of artificial analogues.

    13. Revealing the Electron–Phonon Coupling in a Conjugated Polymer by Single-Molecule Spectroscopy (pages 1978–1982)

      R. Hildner, U. Lemmer, U. Scherf, M. van Heel and J. Köhler

      Article first published online: 26 JUN 2007 | DOI: 10.1002/adma.200602718

      Thumbnail image of graphical abstract

      Electron–phonon coupling in a π-conjugated polymer is revealed by single-molecule spectroscopy in combination with statistical pattern recognition techniques. The technique allows to reveal the phonon-side band in the spectra of methyl-substituted ladder-type poly(para-phenylene) (see figure). For this polymer a weak electron–phonon coupling strength is found at low temperatures. The distribution of the phonon frequencies provides strong evidence that the low-energy vibrational modes, which couple to the electronic transitions, stem from vibrations of the host matrix.

    14. A Novel, Luminescent, Silica-Sol–Gel Hybrid Based on Surfactant- Encapsulated Polyoxometalates (pages 1983–1987)

      W. Qi, H. Li and L. Wu

      Article first published online: 20 JUN 2007 | DOI: 10.1002/adma.200602430

      Thumbnail image of graphical abstract

      A modified sol–gel approach is used for the preparation of stable silica materials based on a surfactant-encapsulated polyoxometalate (see figure, top panel). In this hybrid material, the luminescence properties of the polyoxometalate and the processibility of the sol–gel matrix are synergistically combined (see figure, bottom panel). This method is, in principle, applicable to all varieties of polyoxometalates, and the resulting composites could be used for applications in optics and catalysis.

    15. Enhanced Two-Photon Excitation Fluorescence by Fluorescence Resonance Energy Transfer Using Conjugated Polymers (pages 1988–1991)

      N. Tian and Q.-H. Xu

      Article first published online: 2 JUL 2007 | DOI: 10.1002/adma.200700654

      Thumbnail image of graphical abstract

      A two-photon excitation fluorescence resonance energy transfer scheme, in a system consisting of a cationic conjugated polymer, dsDNA, and a DNA intercalator, is reported. The conjugated polymer acts as two-photon excitation light-harvesting complex (see figure). The two-photon excitation fluorescence of the intercalator is found to be enhanced by a factor of over 35 upon addition of conjugated polymers. The obtained results may have profound implications in two-photon imaging and phototherapy.

    16. Competitive Hydrogen Bonding in π-Stacked Oligomers (pages 1992–1995)

      A. Rochefort, É. Bayard and S. Hadj-Messaoud

      Article first published online: 26 JUN 2007 | DOI: 10.1002/adma.200602099

      Thumbnail image of graphical abstract

      A theoretical study showing the importance of intra- and intermolecular hydrogen bonding in the formation of self-assembled systems is reported. Arene-based species with appropriate functional groups to favor intermolecular hydrogen bonding are studied. It is found that molecular flexibility can create strong intermolecular hydrogen bonds within oligomers in which molecules are generally separated by large interplanar distances (see figure).

    17. A Pyrolytic, Carbon-Stabilized, Nanoporous Pd Film for Wide-Range H2 Sensing (pages 1996–1999)

      D. Ding and Z. Chen

      Article first published online: 12 JUL 2007 | DOI: 10.1002/adma.200601572

      Thumbnail image of graphical abstract

      High-performance H2sensors are becoming increasingly important in detecting and monitoring H2. By using pyrolytic carbon as a transition layer between a Pd film and an anodic aluminum oxide substrate, a nanoporous Pd film sensor is fabricated (see figure) that has a remarkable sensing performance with the ability to detect both dilute and high concentrations of H2 gas quickly and at room temperature.

    18. Prediction of the Absolute Charge Mobility of Molecular Semiconductors: the Case of Rubrene (pages 2000–2004)

      A. Troisi

      Article first published online: 12 JUL 2007 | DOI: 10.1002/adma.200700550

      Thumbnail image of graphical abstract

      The absolute value of the hole mobility, computed for the case of rubrene without adjustable parameters (see figure), is in excellent agreement with experiments. The diffusion of the hole is limited by thermal fluctuations of the intermolecular coupling. The system parameters are computed using a combination of classical molecular-dynamics simulations and quantum chemical methods. The effect of intramolecular reorganization energy is included in the model.

    19. Uniform Nonspherical Colloidal Particles with Tunable Shapes (pages 2005–2009)

      J.-W. Kim, R. J. Larsen and D. A. Weitz

      Article first published online: 12 JUL 2007 | DOI: 10.1002/adma.200602345

      Thumbnail image of graphical abstract

      A framework for large-scale synthesis of a variety of uniform nonspherical particle types (see figure) is introduced. The technique involves controlling the directionality of phase separations in the seeded-polymerization technique by manipulating the crosslinking density gradients of the dimer seed particles, thus allowing the obtainment of novel nonspherical particle shapes and the production of sufficient quantities to characterize their bulk properties.

    20. A Conjugated, Neutral Surfactant as Electron-Injection Material for High-Efficiency Polymer Light-Emitting Diodes (pages 2010–2014)

      F. Huang, Y.-H. Niu, Y. Zhang, J.-W. Ka, M. S. Liu and A. K.-Y. Jen

      Article first published online: 29 JUN 2007 | DOI: 10.1002/adma.200602967

      Thumbnail image of graphical abstract

      A novel conjugated neutral surfactant poly[9,9-bis(6′-(diethanolamino)hexyl)fluorene] (PFN-OH; see figure) has been developed as an efficient electron-injection material for fabricating highly efficient multilayer polymer light-emitting diodes. Compared to the traditional neutral surfactants used, PFN-OH possesses the combined advantages of good conductivity and excellent electron-injection ability from high-work-function metals (e.g., Al, Ag, or Au).

    21. Fabrication and Impedance Analysis of n-ZnO Nanorod/p-Si Heterojunctions to Investigate Carrier Concentrations in Zn/O Source- Ratio-Tuned ZnO Nanorod Arrays (pages 2015–2019)

      J.-J. Wu and D. K.-P. Wong

      Article first published online: 26 JUN 2007 | DOI: 10.1002/adma.200602052

      Thumbnail image of graphical abstract

      Charge-carrier concentrations of well-aligned ZnO nanorods grown on p++-Si substrates are determined by means of ac impedance analysis of devices fabricated directly on as-deposited samples. This approach also demonstrates that the carrier concentration can be controlled by varying the Zn/O source molar ratio (MR) during metal–organic chemical vapor deposition (see figure).

    22. Micropatterning by Non-Densely Packed Interfacial Colloidal Crystals (pages 2020–2022)

      M. A. Ray and L. Jia

      Article first published online: 11 JUL 2007 | DOI: 10.1002/adma.200602521

      Thumbnail image of graphical abstract

      A new surface-patterning method that involves the intact transferring of interfacial non-densely packed hexagonal colloidal crystals onto silicon wafer substrates has been developed. The arrays have long-range order on the square millimeter scale. The laser diffraction pattern of a micropatterned surface is shown in the figure.

    23. Photoresponsive Slide-Ring Gel (pages 2023–2025)

      T. Sakai, H. Murayama, S. Nagano, Y. Takeoka, M. Kidowaki, K. Ito and T. Seki

      Article first published online: 11 JUL 2007 | DOI: 10.1002/adma.200700457

      Thumbnail image of graphical abstract

      Slide-ring topological gels with mobile cross-linking units are a new class of soft materials that exhibit distinct features differing from those of conventional chemically or physically cross-linked gels. Photoresponsive behavior arising from the dynamic nature of the cross-linkers is demonstrated for a slide-ring gel prepared by adding azobenzene units to the mobile α-cyclodextrin units of a poly(ethylene oxide)-based polyrotaxane (see figure).

  5. Index

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Review
    5. Communications
    6. Index
    1. Author Index and Subject Index Adv. Mater. 15/2007 (pages 2027–2028)

      Article first published online: 27 JUL 2007 | DOI: 10.1002/adma.200790055

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