Advanced Materials

Cover image for Advanced Materials

September, 2003

Volume 15, Issue 17

Pages 1397–1482

    1. A p-Type Amorphous Oxide Semiconductor and Room Temperature Fabrication of Amorphous Oxide p–n Heterojunction Diodes (pages 1409–1413)

      S. Narushima, H. Mizoguchi, K. Shimizu, K. Ueda, H. Ohta, M. Hirano, T. Kamiya and H. Hosono

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200304947

      Oxide electronics, which together with amorphous semiconductors could become a rapid-growth field, have come a step closer with the first report of a p-type amorphous oxide semiconductor, ZnO·Rh2O3. The thin-film deposition of this material at room temperature and the fabrication of p–n heterojunction diodes on flexible plastic sheets (see Figure) are demonstrated.

    2. Versatile Nanopatterned Surfaces Generated via Three-Dimensional Colloidal Crystals (pages 1413–1417)

      X. Chen, Z. Chen, N. Fu, G. Lu and B. Yang

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305318

      Surfaces with two-dimensional nanoring or nanoporous arrays and nanopatterned SAMs have been fabricated via the “colloidal crystal-assisted capillary nanofabrication” (CCACN) method. The Figure shows the two-dimensional poly(vinyl alcohol) (PVA) nanoring arrays generated using a delicate template and the controllable capillary and dewetting actions in the CCACN process.

    3. Hydrophilic Interface-Directed Self-Assembly of Bola-Form Amide into Hollow Spheres (pages 1417–1420)

      Y. Matsuzawa, M. Kogiso, M. Matsumoto, T. Shimizu, K. Shimada, M. Itakura and S. Kinugasa

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305276

      Stable submicrometer-sized hollow spheres of bola-form amide (see Figure) are formed in aqueous solution via non-covalent interactions induced by the presence of a hydrophilic substrate. Rod-like micelles self-assemble to form spherical vesicles, which, in the presence of the substrate, gather to form spherical hollow particles. In contrast, when no substrate is present, the spherical vesicles to self-assemble into fibers.

    4. Stable Photopatterned Cholesteric Layers Made by Photoisomerization and Subsequent Photopolymerization for Use as Color Filters in Liquid-Crystal Displays (pages 1420–1425)

      J. Lub, P. van de Witte, C. Doornkamp, J.P.A. Vogels and R.T. Wegh

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305125

      Very stable cholesteric layers with patterned reflection colors are made by coating a monomeric cholesteric mixture on a substrate followed by photoisomerization in air to tune the reflection color and photopolymerization to stabilize the layer. The layers can be used as color filters in liquid-crystal displays (see Figure). The photopolymerization is performed in N2, resulting in rapid crosslinking, preventing unwanted additional color changes.

    5. Optically Amplified RNA–Protein Detection Methods Using Light-Harvesting Conjugated Polymers (pages 1425–1428)

      S. Wang and G.C. Bazan

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305099

      A sensor is described that takes advantage of highly specific RNA–protein interactions and the light-harvesting properties of conjugated polymers. Coordination between a cationic conjugated polymer (CP+) and a negatively charged protein–RNA complex results in efficient Förster resonance energy transfer (FRET) from CP+ to a protein-bound chromophore (see Figure and inside cover). This sensor was used to detect the transactivation responsive RNA sequence of HIV-1.

    6. KSb5S8: A Wide Bandgap Phase-Change Material for Ultra High Density Rewritable Information Storage (pages 1428–1431)

      T. Kyratsi, K. Chrissafis, J. Wachter, K.M. Paraskevopoulos and M.G. Kanatzidis

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200304994

      A well defined, congruently melting stoichiometric system, KSb5S8 (see Figure), with a wide optical energy gap that undergoes rapid reversible crystal–glass transformation is described. The activation energy of crystallization Ec was calculated to be ∼ 167 kJ mol–1. The kinetic parameters and energy bandgaps of KSb5S8 suggest a new inexpensive phase-change material for possible ultra high density data storage applications.

    7. Light-Induced Reorganization in Self-Assembled Liquid Crystal Gels: Electrically Switchable Diffraction Gratings (pages 1431–1435)

      Y. Zhao and X. Tong

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305120

      Electrically switchable diffraction gratings can be formed in the self-assembled cholesteric liquid crystal gels prepared using an azobenzene-containing gelator. The grating formation (see Figure) results from a light-induced reorganization process in these materials, which leads to the removal of the nanometer-sized fibrous aggregates of the gelator from the irradiated area to the non-irradiated area.

    8. The Chiroptical Properties of a Thermally Annealed Film of Chiral Substituted Polyfluorene Depend on Film Thickness (pages 1435–1438)

      M.R. Craig, P. Jonkheijm, S.C.J. Meskers, A.P.H.J. Schenning and E.W. Meijer

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305243

      The degree of circular polarization in the absorption of light by a thermally annealed film of chirally substituted polyfluorene depends strongly on the film thickness. This indicates that the exceptionally high dissymmetry ratios observed for these films originate on a nanoscopic level and are related to the long-range correlation in the polymer chain orientation. Circular polarizations (see Figure) of up to 50 % can be reached.

    9. Lanthanum–Cerium Oxide as a Thermal Barrier-Coating Material for High-Temperature Applications (pages 1438–1442)

      X. Cao, R. Vassen, W. Fischer, F. Tietz, W. Jungen and D. Stöver

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200304132

      La2Ce2O7 is proposed as a new material for thermal barrier coating that has a higher thermal expansion coefficient and a lower thermal conductivity than traditional coating materials. After long-term annealing at 1400 °C, the crystal structure of La2Ce2O7 was maintained (see Figure). Below 300 °C, thermal contraction occurs, and the material has a comparable thermal cycling life to yttria-stabilized zirconia coatings.

    10. Rare Earth Compound Nanotubes (pages 1442–1445)

      X. Wang, X.-M. Sun, D. Yu, B.-S. Zou and Y. Li

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305164

      A series of rare earth compound nanotubes, including hydroxides, oxides, oxysulfides, and hydroxyfluorides, have been synthesized using a facile hydrothermal method. Owing to their excellent hydrophilicity, the nanotubes can be easily functionalized, and should offer new opportunities in areas such as optoelectronic and nanoscale devices, low dimensional physics and material science, molecular catalysts, and biological technology.

    11. Rectangular Single-Crystal Mullite Microtubes (pages 1445–1449)

      X.Y. Kong, Z.L. Wang and J. Wu

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305405

      A novel single-crystalline microtubular structure of Al-rich mullite has been synthesized via a simple solid–vapor process. The microtubes have perfect rectangularly framed cross-sections (see Figure and cover) as defined by the ± (110) and ± (1equation image0) facets. The microtubes have a [001] growth axis, a dislocation-free volume, a large, completely hollow interior channel 0.5–3 μm in width, and thin walls of 50–100 nm.

    12. Micropatterning of Metal Nanoparticles via UV Photolithography (pages 1449–1452)

      S. Horiuchi, T. Fujita, T. Hayakawa and Y. Nakao

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305270

      The patterning metal nanoparticles by a combination of conventional UV irradiation on PMMA and the reduction of PdII bis(acetylacetonato) is reported. PMMA does not reduce the metal complex as much as other polymers do, but exposure to UV enhances the reducing power against the metal complex and enables Pd particles to be patterned on PMMA films when irradiated through a photomask (see Figure).

    13. Preparation of Highly Ordered Monolithic Super-Microporous Lamellar Silica with a Room-Temperature Ionic Liquid as Template via the Nanocasting Technique (pages 1452–1455)

      Y. Zhou and M. Antonietti

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305265

      A special room-temperature ionic liquid, 1-hexadecyl-3-methyl-imidazolium chloride, is used as a template to prepare monolithic super-microporous silica with lamellar order (monolith in Figure) via a nanocasting technique. The silica walls of the synthesized product are arranged parallel to each other, displaying a regular structure with an interlayer distance, pore diameter, and wall system thickness of about 2.7 nm, 1.3 nm, and 1.4 nm, respectively.

    14. Color Tunable Organic Light-Emitting Diodes Using Pentafluorophenyl-Substituted Iridium Complexes (pages 1455–1458)

      T. Tsuzuki, N. Shirasawa, T. Suzuki and S. Tokito

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305034

      Novel iridium complexes with perfluorophenyl-substituted phenylpyridine ligands have been developed. The Figure shows the photoluminescence (PL) spectra of four complexes in the doped films. By changing the position of substitution, the peaks in the PL spectra are tuned in the wavelength region 513–578 nm. Light-emitting diodes using these complexes as the emitting material show an external quantum efficiency of 10–17 %.

    15. A Novel Macromolecular Complex: Fabrication of Monodisperse Colloidal Microspheres by Precipitation Polymerization of Imine Chains and Concomitant Transition Metal Binding (pages 1458–1461)

      H. Houjou, Y. Shimizu, N. Koshizaki and M. Kanesato

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305181

      A series of monodisperse colloidal microspheres has been fabricated by precipitation polymerization of imine chains and concomitant transition metal binding. The resulting metal-bound polyimine microspheres (M-PIMSs, M = Co, Ni, Cu, or Zn, see Figure, which shows Zn-PIMSs) have characteristic diameters in the range from 0.5 to 1.4 μm, depending on the metal used, and are of interest for applications in photonic devices.

    16. Hierarchically Mesostructured Titania Materials with an Unusual Interior Macroporous Structure (pages 1462–1465)

      Z.-Y. Yuan, T.-Z. Ren and B.-L. Su

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200305075

      Outside mesoporous, inside macroporous. Mesoporous titania samples with an internal macroporous structure (see Figure) are reported to have been synthesized by a one-step templating process. The materials have a thick shell and a sponge-like macrostructured core with a uniform pore gradient. The synthesis conditions, particularly water content, are demonstrated to affect the pore structure crucially.

    17. Submicrometer Functionalization of Porous Silicon by Electron Beam Lithography (pages 1465–1469)

      M. Rocchia, S. Borini, A.M. Rossi, L. Boarino and G. Amato

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200304919

      Functionalization of porous silicon (PS) by an innovative method based on electron beam (EB) irradiation is reported. It is shown that EB irradiation induces hydrogen desorption from PS, leaving a very reactive surface, and that this PS surface undergoes local modification when treated with unsaturated hydrocarbons immediately after EB exposure. Finally, the authors demonstrate that different molecules can be attached to the same chip in different regions with the resolution typical of EB lithography, i.e., submicrometer patterning is possible.

    18. Organic Microcavity Photodiodes (pages 1471–1474)

      J.M. Lupton, R. Koeppe, J.G. Müller, J. Feldmann, U. Scherf and U. Lemmer

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200301644

      Organic microcavity photodiodes are constructed by placing the optically active layer inside an optical resonator. Besides enhancing both linear and nonlinear absorption in the material, optical confinement also improves the spectral selectivity by limiting the photocurrent enhancement to a narrow spectral region. The Figure shows colors resulting from different microcavities on a single substrate, which could be used in color-sensitive detector arrays.

    19. Electron Holography of Organic and Biological Materials (pages 1475–1481)

      P. Simon, H. Lichte, J. Drechsel, P. Formanek, A. Graff, R. Wahl, M. Mertig, R. Adhikari and G.H. Michler

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/adma.200301645

      Off-axis electron holography was used to characterize the morphology of nanostructured organic semiconductor devices, biological samples, and multicomponent polymers. For example, the surrounding magnetic phase distribution of a carbon nanotube filled with nickel particles (see Figure) could be successfully imaged. This technique can be used to resolve the fine-structures of heterophase systems without sample modification, thus preventing preparation-induced artifacts.