Advanced Materials

Cover image for Vol. 18 Issue 3

February, 2006

Volume 18, Issue 3

Pages 255–378

    1. Cover Picture: A Two-Dimensional Porphyrin-Based Porous Network Featuring Communicating Cavities for the Templated Complexation of Fullerenes (Adv. Mater. 3/2006)

      H. Spillmann, A. Kiebele, M. Stöhr, T. A. Jung, D. Bonifazi, F. Cheng and F. Diederich

      Version of Record online: 26 JAN 2006 | DOI: 10.1002/adma.200690013

      An unprecedented two-dimensional porphyrin network featuring dynamic pores capable of hosting fullerenes is realized following a bottom-up approach at a single-crystal silver surface. Surface- and porphyrin-driven long-range interactions between the C60 guest molecules and porphyrin layer result in the formation of exceptionally large supramolecular hybrid chains and islands (see Figure and Cover).

    2. Inside Front Cover: Electronic Transport through Electron-Doped Metal Phthalocyanine Materials (Adv. Mater. 3/2006)

      M. F. Craciun, S. Rogge, M.-J. L. den Boer, S. Margadonna, K. Prassides, Y. Iwasa and A. F. Morpurgo

      Version of Record online: 26 JAN 2006 | DOI: 10.1002/adma.200690014

      Transport measurements for different electron-doped metal phthalocyanine materials demonstrate the possibility to control their electronic properties through alkali intercalation. In these materials, increasing the potassium concentration results in the formation of a doping-induced metallic state (see Figure and Inside Cover). Further doping brings the materials back into the insulating state.

    3. Contents: Adv. Mater. 3/2006 (pages 255–263)

      Version of Record online: 26 JAN 2006 | DOI: 10.1002/adma.200690011

    4. Direct Laser Writing of Three- Dimensional Photonic Crystals with a Complete Photonic Bandgap in Chalcogenide Glasses (pages 265–269)

      S. Wong, M. Deubel, F. Pérez-Willard, S. John, G. A. Ozin, M. Wegener and G. von Freymann

      Version of Record online: 10 JAN 2006 | DOI: 10.1002/adma.200501973

      Thumbnail image of graphical abstract

      Direct laser writing in chalcogenide glasses of three-dimensional (3D) photonic crystals (see Figure) with a complete photonic bandgap is reported. This novel approach allows for the direct fabrication of arbitrarily shaped 3D microstructures in high refractive index materials. Woodpile structures are fabricated in less than two hours, whose optical properties are compatible with a complete gap of 3.5%.

    5. Fabrication and Assembly Behavior of Square Microcapsules (pages 270–274)

      F. Li, X. Badel, J. Linnros, G. Wasserman, S. L. Whittenburg, L. Spinu and J. B. Wiley

      Version of Record online: 3 JAN 2006 | DOI: 10.1002/adma.200401411

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      Square microcapsules have been fabricated within porous silicon membranes. The capsules float in water when released from the membrane (see Figure). Dry capsules float with one of their edges pointing down, but after uptake of water, they float face down; the edge-down capsules assemble end-to-end while the face-down capsules assemble face-to-face.

    6. A Two-Dimensional Porphyrin-Based Porous Network Featuring Communicating Cavities for the Templated Complexation of Fullerenes (pages 275–279)

      H. Spillmann, A. Kiebele, M. Stöhr, T. A. Jung, D. Bonifazi, F. Cheng and F. Diederich

      Version of Record online: 3 JAN 2006 | DOI: 10.1002/adma.200501734

      Thumbnail image of graphical abstract

      An unprecedented two-dimensional porphyrin network featuring dynamic pores capable of hosting fullerenes is realized following a bottom-up approach at a single-crystal silver surface. Surface- and porphyrin-driven long-range interactions between the C60 guest molecules and porphyrin layer result in the formation of exceptionally large supramolecular hybrid chains and islands (see Figure and Cover).

    7. Efficient Near-Infrared Emission from Sodalite Derivatives (pages 280–283)

      M. Lezhnina, F. Laeri, L. Benmouhadi and U. Kynast

      Version of Record online: 10 JAN 2006 | DOI: 10.1002/adma.200501206

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      The use of nanoporous host materials for luminescent guests has been extended into the near-infrared (NIR) regime using sodalite derivatives containing rare earth ions and the tungstate group (see Figure). The emission intensities obtained for Nd3+ meet or even surpass commercial Nd glasses. While Nd3+-tungstate-modified zeolites do not yield significant luminescence, NIR emission occurs in the sodalites due to the low phonon frequencies involved and the exclusion of water in particular.

    8. Assembly of Nanoparticle Ring Structures Based on Protein Templates (pages 284–289)

      S. Behrens, W. Habicht, K. Wagner and E. Unger

      Version of Record online: 3 JAN 2006 | DOI: 10.1002/adma.200501096

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      Ring-like nanoparticle arrays, not accessible via any of the conventional synthetic methods, are synthesized by a rapid and straightforward method. Calcium ions direct the assembly of tubulin into spiral-shaped protein structures, which provide a tool to control the deposition of Ag nanoparticles into spiral-shaped arrays along the backbone of the biostructure (see Figure). This synthetic capability creates the potential of wet-chemical synthesis of nanosized metallic ring structures.

    9. Microstructure and Composition of Focused-Ion-Beam-Deposited Pt Contacts to GaN Nanowires (pages 290–294)

      D. Tham, C.-Y. Nam and J. E. Fischer

      Version of Record online: 14 DEC 2005 | DOI: 10.1002/adma.200501832

      Thumbnail image of graphical abstract

      Characterization of focused ion beam (FIB)-deposited Pt contacts to GaN nanowires (see Figure, green) shows that these contacts contain high densities of Pt nanocrystallites (red) embedded in an amorphous C + Ga matrix (purple). Regions with lower Pt nanocrystallite densities (light blue) have also been found. Sputter damage generally removes the top of the GaN layer, leaving a disordered region below. These observations suggest reasons for the unusually low resistance of FIB-deposited Pt contacts to GaN nanowires.

    10. Gigantic Magneto–Optical Effects in Multilayer Assemblies of Two-Dimensional Titania Nanosheets (pages 295–299)

      M. Osada, Y. Ebina, K. Takada and T. Sasaki

      Version of Record online: 26 JAN 2006 | DOI: 10.1002/adma.200501810

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      A two-dimensional titania nanosheet is proven to be useful as a host for spinelectronic materials. Magneto–optical measurements demonstrate that Co-substituted titania nanosheets (Ti0.8Co0.2O2) act as nanoscale ferromagnetic layers at room temperature, and their multilayer assemblies exhibit robust magnetic circular dichroism (MCD) in the ultraviolet–visible region. The availability of ferromagnetic nanostructures allows the rational design of high-efficiency magneto–optical devices.

    11. Dynamic Tuning of Organic Lasers with Colloidal Crystals (pages 300–303)

      J. R. Lawrence, Y. Ying, P. Jiang and S. H. Foulger

      Version of Record online: 10 JAN 2006 | DOI: 10.1002/adma.200501833

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      Thin-film organic lasers can be dynamically tuned by the introduction of photonic crystals. A dielectric stack medium is coated with a thin gain layer and then laminated with a photonic bandgap composite film. Applying a stress to the composite film modifies the supported resonator frequencies, and thus the corresponding lasing wavelengths (see Figure). The advantage of this design is its simplicity, which permits the design of the gain medium or the resonator cavity to be considered independently.

    12. Highly Bendable, Transparent Thin-Film Transistors That Use Carbon-Nanotube-Based Conductors and Semiconductors with Elastomeric Dielectrics (pages 304–309)

      Q. Cao, S.-H. Hur, Z.-T. Zhu, Y. G. Sun, C.-J. Wang, M. A. Meitl, M. Shim and J. A. Rogers

      Version of Record online: 3 JAN 2006 | DOI: 10.1002/adma.200501740

      Thumbnail image of graphical abstract

      Transparent flexible thin-film transistors (see Figure) have been made using single-walled carbon nanotube networks of high and moderate coverages as the conducting and semiconducting layers. Electrical (e.g., good performance on plastic), optical (e.g. transparency to visible wavelengths), and mechanical (e.g. extreme flexibility) characteristics that would be difficult, or impossible, to achieve with conventional materials are reported.

    13. Molecular Origin of the Temperature-Dependent Energy Migration in a Rigid-Rod Ladder-Phenylene Molecular Host (pages 310–314)

      H. Wiesenhofer, E. Zojer, E. J. W. List, U. Scherf, J.-L. Brédas and D. Beljonne

      Version of Record online: 3 JAN 2006 | DOI: 10.1002/adma.200501473

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      Excitation diffusion is studied in a molecular host doped with a luminescent guest. An atomistic model based on the coupling of the electronic excitations to low-frequency intramolecular vibrations reproduces remarkably well the measured temperature-dependent host-to-guest energy transfer efficiency (see Figure).

    14. Dendrimer-Scaffold-Based Electron-Beam Patterning of Biomolecules (pages 315–319)

      P. Bhatnagar, S. S. Mark, I. Kim, H. Chen, B. Schmidt, M. Lipson and C. A. Batt

      Version of Record online: 10 JAN 2006 | DOI: 10.1002/adma.200501170

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      A layer-by-layer approach for patterning biomolecules on dendrimer scaffolds using electron-beam lithography has been developed (see Figure). A self-assembled poly(ethylene glycol) monolayer is patterned with aldehyde-terminated polyamidoamine dendrimers to allow the covalent immobilization of aminated oligonucleotide probes.

    15. Electronic Transport through Electron-Doped Metal Phthalocyanine Materials (pages 320–324)

      M. F. Craciun, S. Rogge, M.-J. L. den Boer, S. Margadonna, K. Prassides, Y. Iwasa and A. F. Morpurgo

      Version of Record online: 14 DEC 2005 | DOI: 10.1002/adma.200501268

      Thumbnail image of graphical abstract

      Transport measurements for different electron-doped metal phthalocyanine materials demonstrate the possibility to control their electronic properties through alkali intercalation. In these materials, increasing the potassium concentration results in the formation of a doping-induced metallic state (see Figure and Inside Cover). Further doping brings the materials back into the insulating state.

    16. Efficient Blue-Light-Emitting Electroluminescent Devices with a Robust Fluorophore: 7,8,10-Triphenylfluoranthene (pages 325–328)

      R. C. Chiechi, R. J. Tseng, F. Marchioni, Y. Yang and F. Wudl

      Version of Record online: 10 JAN 2006 | DOI: 10.1002/adma.200501682

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      The strong blue emission, resistance to quenching, and ease of synthesis of 7,8,10-triphenylfluoranthene (TPF) are exploited for applications in organic blue-light-emitting devices. The image shows the structure of TPF superimposed on a graph of the electroluminescence efficiency of a pristine device.

    17. Electron Transport Across Hexa-peri-hexabenzocoronene Units in a Metal–Self-Assembled Monolayer–Metal Junction (pages 329–333)

      M. Duati, C. Grave, N. Tcbeborateva, J. Wu, K. Müllen, A. Shaporenko, M. Zharnikov, J. K. Kriebel, G. M. Whitesides and M. A. Rampi

      Version of Record online: 10 JAN 2006 | DOI: 10.1002/adma.200501482

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      Self-assembled monolayers (SAMs) formed by hexabenzocoronene core (HBC) derivatives are incorporated in metal–SAM–metal junctions. Comparisons of the current–voltage curves measured across four junctions show that the HBC units are highly transparent to electrons. HBC SAMs can sustain high bias voltages (higher than 2 V) and are very robust to mechanical stress. These characteristics qualify this material as a promising building block for molecular electronics.

    18. Hybrid Inorganic/Organic Semiconductor Heterostructures with Efficient Non-Radiative Energy Transfer (pages 334–338)

      G. Heliotis, G. Itskos, R. Murray, M. D. Dawson, I. M. Watson and D. D. C. Bradley

      Version of Record online: 10 JAN 2006 | DOI: 10.1002/adma.200501949

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      An inorganic/organic hybrid semiconductor heterostructure is reported, in which an InGaN quantum well is non-radiatively coupled to a semiconducting polymer overlayer (see Figure). This architecture has the potential to take advantage of the complementary attributes of the two types of semiconductor that it contains, and may lead to devices with highly efficient emission across the entire visible spectrum.

    19. White Stacked Electrophosphorescent Organic Light-Emitting Devices Employing MoO3 as a Charge-Generation Layer (pages 339–342)

      H. Kanno, R. J. Holmes, Y. Sun, S. Kena-Cohen and S. R. Forrest

      Version of Record online: 10 JAN 2006 | DOI: 10.1002/adma.200501915

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      White stacked electrophosphorescent organic light-emitting devices employing three metallorganic phosphors in a compound emission layer (see Figure) are demonstrated. They show an external efficiency of 51 % and power efficiency of 20.7 lm W–1 at practical illumination intensities. A transparent MoO3 film between two adjacent electrophosphorescent elements efficiently injects charge into the stacked elements.

    20. Amplified Spontaneous Emission in Semiconductor-Nanocrystal/Synthetic-Opal Composites: Optical-Gain Enhancement via a Photonic Crystal Pseudogap (pages 343–347)

      G. R. Maskaly, M. A. Petruska, J. Nanda, I. V. Bezel, R. D. Schaller, H. Htoon, J. M. Pietryga and V. I. Klimov

      Version of Record online: 10 JAN 2006 | DOI: 10.1002/adma.200500875

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      Novel materials consisting of titania sol–gel/CdSe- or PbSe-nanocrystal (NC) nanocomposites infiltrated into polystyrene opal photonic crystals (PCs) are presented (see Figure). These composites exhibit efficient amplified spontaneous emission at decreased thresholds relative to the reference sol–gel/NC materials, despite the lower volume loading of NCs in the photonic structures. This work points toward tunable NC/PC lasers that can benefit from the easy manipulation of NC emission properties and PC band positions.

    21. Electrospun Polyaniline/Poly(methyl methacrylate)-Derived Turbostratic Carbon Micro-/Nanotubes (pages 348–353)

      E. Zussman, A. L. Yarin, A. V. Bazilevsky, R. Avrahami and M. Feldman

      Version of Record online: 10 JAN 2006 | DOI: 10.1002/adma.200501153

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      A simple two-stage technique for producing turbostratic carbon nanotubes via the co-electrospinning of two polymer solutions is described. These strong carbon nanotubes (see Figure) can be produced in lengths of the order of 10 cm while still maintaining submicrometer inner and outer diameters. They can be used in numerous applications, such as in drug delivery, hydrogen storage, and microfluidics.

    22. Selective Fabrication of Poly(3,4-ethylenedioxythiophene) Nanocapsules and Mesocellular Foams Using Surfactant-Mediated Interfacial Polymerization (pages 354–358)

      J. Jang, J. Bae and E. Park

      Version of Record online: 26 JAN 2006 | DOI: 10.1002/adma.200502060

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      Poly(3,4-ethylenedioxythiophene) (PEDOT) nanocapsules and mesocellular foams have been selectively fabricated by surfactant-mediated interfacial polymerization (see Figure). The morphology of the PEDOT nanomaterials significantly depends on the surfactant concentration, and the PEDOT nanocapsules and mesocellular foams show good performance as supercapacitors.

    23. Low-Temperature Synthesis of Star-Shaped PbS Nanocrystals in Aqueous Solutions of Mixed Cationic/Anionic Surfactants (pages 359–362)

      N. Zhao and L. Qi

      Version of Record online: 10 JAN 2006 | DOI: 10.1002/adma.200501756

      Thumbnail image of graphical abstract

      Uniform, well-defined star-shaped PbS nanocrystals with tunable sizes (40–100 nm, see Figure), as well as octahedral PbS nanocrystals, have been readily synthesized in aqueous solutions containing a mixture of the surfactants cetyltrimethylammonium bromide/ sodium dodecyl sulfate (CTAB/SDS) at low temperature (80 °C). The size of the PbS nanostars can be accurately controlled by adjusting the reaction time. This result may open new avenues for the green chemical synthesis of shape-controlled semiconductor nanocrystals.

    24. Integration of Erbium-Doped Lithium Niobate Microtubes into Ordered Macroporous Silicon (pages 363–366)

      L. Zhao, T. Lu, M. Zacharias, J. Yu, J. Shen, H. Hofmeister, M. Steinhart and U. Gösele

      Version of Record online: 10 JAN 2006 | DOI: 10.1002/adma.200501974

      Thumbnail image of graphical abstract

      Er3+-doped LiNbO3 microtubes have been prepared by the infiltration of ordered macroporous silicon with Er:LiNbO3 melts (see Figure). The microtubes consist of single-crystalline segments and exhibit the characteristic photoluminescence of Er3+, which coincides with the transmittance maximum of silica-based optical components.

    25. Pyramid-Shaped Si/Ge Superlattice Quantum Dots with Enhanced Photoluminescence Properties (pages 367–370)

      H.-C. Chen, C.-W. Wang, S.-W. Lee and L.-J. Chen

      Version of Record online: 26 JAN 2006 | DOI: 10.1002/adma.200501691

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      Pyramid-shaped Si/Ge superlattice quantum dots (QDs, see Figure) have been fabricated using self-assembled Ge QDs as a “virtual nanomask” for selective wet etching of the Si/Ge superlattice. The nanodots exhibit an approximately tenfold increase in photoluminescence over conventional Si/Ge superlattice heterostructures.

    26. Nanoporous Anatase Thin Films as Fast Proton-Conducting Materials (pages 371–374)

      M. T. Colomer

      Version of Record online: 26 JAN 2006 | DOI: 10.1002/adma.200500689

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      Nanoporous anatase thin films (see Figure) have been prepared via particulate sol–gel processes. The proton conductivity shows a sigmoidal dependence on relative humidity (RH). The highest value of proton conductivity was 3.78 × 10–2 S cm–1 at 80 °C and 81% RH. The comparable proton conductivity, lower cost, and higher hydrophilicity of these thin films make them potential substitutes for Nafion membranes in proton-exchange membrane fuel cells.

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