Advanced Materials

Cover image for Advanced Materials

April, 1999

Volume 11, Issue 6

Pages 435–505

    1. Bacteriorhodopsin Thin-Film Assemblies—Immobilization, Properties, and Applications (pages 435–446)

      Jin-An He, Lynne Samuelson, Lian Li, Jayant Kumar and Sukant K. Tripathy

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<435::AID-ADMA435>3.0.CO;2-U

      Supramolecular assembly of optically active materials into thin film architectures is a topic of significant practical importance. Improving the optical functionality and stability compared to the bulk state of typically fragile biological molecules is a driving force for work in this area. Here, the photocycle of Bacteriorhodopsin (bR, see Fig), and the immobilization methods used to generate thin film structures of bR are reviewed, potential applications are presented, and the controversial mechanism of the differential photoelectric response of bR is discussed.

    2. Assembly of Phenylacetylene-Bridged Gold Nanocluster Dimers and Trimers (pages 447–449)

      Louis C. Brousseau III, James P. Novak, Stella M. Marinakos and Daniel L. Feldheim

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<447::AID-ADMA447>3.0.CO;2-I

      2- and 3-Dimensional crystalline arrangements of metal nanoparticles are of interest because of their unique optical and electronic behavior. Discrete assemblies of nanoclusters (e.g. dimers, trimers) studied in this paper allow the effects of local symmetry on collective particle properties to be studied. The distance and the medium between clusters is known to influence the optical absorption and electron transport. The use of phenylacetylene oligomers as ‘molecular wire’ linkers between the nanoparticles is demonstrated to allow well-defined, rigid arrays with a variety of geometries to be produced.

    3. Directed Self-Assembly of Nanoparticles into Macroscopic Materials Using Antibody–Antigen Recognition (pages 449–452)

      Wayne Shenton, Sean A. Davis and Stephen Mann

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<449::AID-ADMA449>3.0.CO;2-A

      A biomolecular-derived route for the self-assembly of inorganic nanoparticles using the recognition properties of antibodies attached to the surface of the gold nanoparticles is reported. The high specificity of antibody–antigen coupling is exploited to generate extended three-dimensional networks of metal nanoparticles (see Fig.) which can exhibit higher-order structures such as wires and filaments.

    4. Synthesis and Characterization of Highly Efficient, Chemically and Thermally Stable Chromophores with Chromone-Containing Electron Acceptors for NLO Applications (pages 452–455)

      Alex K.-Y. Jen, Yunqi Liu, Lixin Zheng, Sen Liu, Kevin J. Drost, Yue Zhang and Larry R. Dalton

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<452::AID-ADMA452>3.0.CO;2-Y

      Donor–acceptor substituted nonlinear optical (NLO) chromophores possessing large molecular hyperpolarizabilities and chemical and thermal stabilities are of interest because of their potential applications in high-speed electro-optic devices. Here, a series of chromophores is presented with a diethylamino group as donor and a variety of strong electron withdrawing groups on the chromone moiety. Incorporation of these chromophores into a polyimide gives a material with high E-O coefficients, low optical loss, and good thermal stability.

    5. Yellow Light–Emitting Poly(phenylenevinylene) Incorporated with Pendant Ruthenium Bipyridine and Terpyridine Complexes (pages 455–459)

      Chi Tak Wong and Wai Kin Chan

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<455::AID-ADMA455>3.0.CO;2-M

      Simultaneous emission from PPV and ruthenium (II) complexes is demonstrated in the title materials (see Fig). The PPV backbone emits green light and the ruthenium polypyridine complexes emit red light resulting in overall yellow emission. At low metal complex content the hexamethylene spacer of the pendant ruthenium complexes prevents quenching of the backbone emission but at higher loading quenching becomes dominant, allowing the emission color of the materials to be tuned by adjusting the metal complex content.

    6. Synthesis, Structure and Properties of an Unsymmetrical Tetraselenafulvalene Donor Fused with a Pyrazino-Ring (PEDTTSeF) and its Cation Radical Salt (pages 459–462)

      Emiko Ojima, Hideki Fujiwara and Hayao Kobayashi

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<459::AID-ADMA459>3.0.CO;2-6

      An organic conductor with a stable metallic state derived from its quasi-2D Fermi surface is reported. Pyrazinoethylenedithio–TTF is known to form a 2D network which should but does not facilitate conduction through intermolecular N–S and S–S contacts. The exchange of selenium for sulfur in these systems, discussed here, results in the formation of the desired metallic state.

    7. A Three-Dimensional Photonic Crystal Operating in the Visible Region (pages 462–466)

      Sang Hyun Park, Byron Gates and Younan Xia

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<462::AID-ADMA462>3.0.CO;2-U

      Photonic bandgap materials have received considerable attention due to their ability to confine and control electromagnetic waves in all three spatial directions. The material reported here (see Fig.) is a cubic-close-packed (ccp) lattice assembled from 215 nm polystyrene beads whose surfaces have been doped with the organic dye Oil Blue N. The method gives large-area crystals and allows the tuning of the photonic bandgap through variation of dopant and bead size (see Cover).

    8. Assembly of Nanoparticles into Opaline Structures over Large Areas (pages 466–469)

      Byron Gates, Dong Qin and Younan Xia

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<466::AID-ADMA466>3.0.CO;2-E

      A simple technique for crystallizing spherical nanoparticles into 3D opaline structures, which can be of use as diffractive elements in the fabrication of optical or electro-optical devices, is presented. Both polystyrene beads and silica colloids within the size range 50–100 nm have been successfully ordered and it is thought that the technique can also be applied to monodisperse particles of other materials and to particles of even smaller size.

    9. Template-assisted Self-assembly and Cobalt Doping of Ordered Mesoporous Titania Nanostructures (pages 469–472)

      Jin Song Yin and Zhong L. Wang

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<469::AID-ADMA469>3.0.CO;2-2

      Template-assisted ordered self-assembly of porous titania nanocrystals is shown to generate a face centered cubic structure where the walls of the pores are made of anatase nanocrystals ca. 8 nm in diameter (see Fig.). The walls of the pores can be doped with cobalt by solution infiltration without blocking the interconnected pores, which suggests that the material is likely to be an excellent supporting material for catalysis.

    10. Effect of Doping Level and Morphology on the Transport Properties of Poly(4,4′-Dipentoxy-2,2′-Bithiophene) (pages 472–474)

      Nadia Camaioni, Giuseppe Casalbore-Miceli, Alessandro Geri and Sergio Nicoletti

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<472::AID-ADMA472>3.0.CO;2-Q

      The transport properties of the title conducting polymer (polyET2), synthesized using two different supporting electrolytes, have been studied over a wide range of electrochemical doping levels. The Hall mobility of the material is found to be sensitive to both the carrier concentration and the molecular order, decreasing as a function of the free carrier concentration, and becoming greater with increasing molecular order. The mobilities achieved with this method are the highest so far known for this kind of material. A conduction model based on overlapping cation states is proposed.

    11. Photoluminescent Silicon Clusters in Oriented Hexagonal Mesoporous Silica Film (pages 474–480)

      Ömer Dag, Geoffrey A. Ozin, Hong Yang, Christian Reber and Guillaume Bussière

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<474::AID-ADMA474>3.0.CO;2-I

      The synthesis of ca. 1 nm diameter photoluminescent silicon nanoclusters in the surfactant-containing channels of a free-standing, oriented hexagonal mesoporous silica film is reported. The preparation involves an exceptionally mild disilane CVD procedure (see Fig.), during which the surfactants are intentionally retained within the channels during CVD, thus restricting the space in which the silicon clusters nucleate and grow.

    12. A Soluble Pentacene Precursor: Synthesis, Solid-State Conversion into Pentacene and Application in a Field-Effect Transistor (pages 480–483)

      Peter T. Herwig and Klaus Müllen

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<480::AID-ADMA480>3.0.CO;2-U

      [n]Acenes are an interesting group of polycyclic aromatic hydrocarbons: The lower [n]acenes are insulators, higher [n]acenes exhibit semiconducting properties, and poly[n]acene is calculated to be a metallic conductor. Pentacene films have been shown to exhibit charge carrier mobilities comparable to that of a-Si. Efficient processing is, however, a requirement for applications. Here, a new synthetic route to a soluble pentacene precursor is presented that could also be used for higher [n]acenes. The precursor can be converted to pentacene after processing, and the materials exhibit a high charge-carrier mobility.

    13. Fabrication and Microstructuring of Hexagonally Ordered Two-Dimensional Nanopore Arrays in Anodic Alumina (pages 483–487)

      An-Ping Li, Frank Müller, Albert Birner, Kornelius Nielsch and Ulrich Gösele

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<483::AID-ADMA483>3.0.CO;2-I

      Hexagonally ordered nanopore arrays in anodic alumina with high aspect ratios (see Fig.) have been produced using a self-organization process. The pore arrays are straight and parallel, and of polycrystalline structure. The distance between pores can be controlled by adjusting the electrolyte and the applied voltage. The arrays could find application as photonic crystals.

    14. Synthesis and Mechanistic Studies of Sulfated Meso- and Microporous Zirconias with Chelating Carboxylate Surfactants (pages 487–492)

      David M. Antonelli

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<487::AID-ADMA487>3.0.CO;2-2

      Ligand-assisted templating with carboxylate surfactants is used to produce micro- and mesoporous zirconias in a method where the organic template can be removed with a simple acid treatment obviating the usual harsh calcination conditions required to remove templates from transition metal oxide molecular sieves. A new mechanism is proposed for the mesostructure formation, in which the self-assembly step and the condensation step occur simultaneously with polymer propagation. Applications in shape-selective catalysis are envisaged.

    15. Making Honeycomb Microcomposites by Soft Lithography (pages 492–495)

      Bing Xu, Francisco Arias and George M. Whitesides

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<492::AID-ADMA492>3.0.CO;2-I

      Small structures tuned in terms of moduli and vibrational damping for use, for example, in microelectromechanical systems (MEMS) can be fabricated by soft lithography as an alternative to complex and expensive processes such as LIGA. The honeycomb structures produced consist of a metal or polymer core of variable geometry (see Fig.) sandwiched between two sheets of high tensile material to give structures with high strength-to-weight ratios.

    16. Ultra-Thin Zeolite Films Through Simple Self-Assembled Processes (pages 497–499)

      Gyoujin Cho, Jae-Suk Lee, Daniel T. Glatzhofer, Bing M. Fung, Wie Lei Yuan and Edgar A. O'Rear

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<497::AID-ADMA497>3.0.CO;2-Z

      Zeolite thin films are very promising as highly selective separation membranes, sensors, conductors, and optoelectronic devices, and a wide variety of methods for their preparation have been reported. In this report, the authors describe their recent use of self-assembled monolayer techniques to prepare ultra-thin films of zeolites on silicon wafers. In an aqueous colloidal solution of zeolite particles, an array of the amphiphilic hexanoic acid could induced deposition of a zeolite film through hydrophobic interactions. The method was found to be simpler and less expensive than those previously reported.

    17. The Role of the Thermal Oxide in GaAs-Based Photonic Bandgap Waveguide Microcavities (pages 501–505)

      Kuo-Yi Lim, Daniel J. Ripin, Gale S. Petrich, Pierre R. Villeneuve, Shanhui Fan, J. D. Joannopoulos, Erich P. Ippen and Leslie A. Kolodziejski

      Version of Record online: 30 APR 1999 | DOI: 10.1002/(SICI)1521-4095(199904)11:6<501::AID-ADMA501>3.0.CO;2-H

      Optical microcavities can be fabricated in III–V semiconductors by introducing a large periodic refractive-index variation along the axis of GaAs waveguides. The critical role of thermal oxide materials in the design of the microcavities (see Fig.) is outlined, and the characterization of the properties of the oxide relevant to device construction described. Preliminary data demonstrating the realization of such a microcavity are presented.