bluuebunny/crossref_metadata_2025 huggingface dataset:
NADPH Oxidase Inhibition Attenuates Oxidative Stress but Not Hypertension Produced by Chronic ET-1
Authors: Elmarakby Ahmed A. , Loomis E. Dabbs , Pollock Jennifer S. , Pollock David M.
Published: December 2004

Experiments were conducted to test the hypothesis that hypertension produced by chronic ET-1 infusion is mediated by NADPH oxidase-dependent superoxide production. Mean arterial pressure (MAP) was continuously monitored in male Sprague Dawley rats by telemetry. After baseline measurements, rats were placed on a high-salt diet (8% NaCl) and osmotic minipumps were implanted to infuse ET-1 (5 pmol/kg per minute intravenous) for 12 days. Control rats were maintained on the high-salt diet only. Separate groups of rats were also infused with ET-1 and given the superoxide dismutase mimetic, tempol (1 mmol/L), or the NADPH oxidase inhibitor, apocynin (1.5 mmol/L), in the drinking water. Infusion of ET-1 significantly increased MAP when compared with baseline values (132±3 versus 114±2 mm Hg,
P
<0.05). Neither tempol nor apocynin treatment had any effect on the increase in MAP produced by ET-1 when compared with baseline values (127±5 versus 113±2 and 130±3 versus 115±2 mm Hg, respectively). Plasma 8-isoprostane, an indicator of oxidative stress, was significantly increased in ET-1–infused rats compared with rats on a high-salt diet alone (128±33 versus 51±5 pg/mL;
P
<0.05). Both tempol and apocynin treatment significantly attenuated the ET-1–induced increase in plasma 8-isoprostane (72±10 and 61±6 pg/mL, respectively). Similarly, ET-1 infusion also significantly increased aortic superoxide production (chemiluminescence and dihydroethidium staining techniques), which was prevented by both tempol and apocynin. These data provide evidence that chronic ET-1 infusion increases vascular NADPH oxidase-dependent superoxide production but does not account for chronic ET-1–induced hypertension.
Structural characterization of non‐oxide Chalcogenide Glasses using solid state NMR
Authors: Eckert Hellmut
Published: December 2004

In spite of the long‐standing importance of non‐oxide chalcogenide glasses in infrared optics and semiconductor technology, concepts describing the structural principles governing glass formation in these systems are just emerging. Most recently, modern quantitative solid state NMR techniques have offered new unique insights into the structural organization of these systems. In this review, we discuss the basic principles of various experimental approaches and their application to boron‐silicon,‐ and phosphorus chalcogenide glasses.
15N CPMAS NMR study of the structure and reactions of phthalocyaninatopolysiloxane and its precursors in the solid state
Authors: Wehrle Bernd , Zipplies Tilman , Limbach Hans‐Heinrich , Hanack Michael
Published: December 2004

The high conductivities of the iodine‐doped title compound (see figure) and its germanium analogue have attracted considerable interest. Structural analysis by X‐ ray crystallography has not been possible, and solid state 13C NMR has yielded complex spectra which are often difficult to assign. I5N CPMAS NMR spectroscopy of I5N enriched samples provides a powerful ity of these species. tool for the study of the structure and reactivity of these species.

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Surface modification technology in Neuchâtel
Authors: Bachmann Peter K.
Published: December 2004

Rainhard Laag reports on the Powder Metallurgy '89 meeting, Hugh Byrne gives us a taste of macromolecular physics in Poland and Peter Bachmann describes a recent meeting on surface modification technology held in Switzerland.
Cooperative magnetic behavior of α‐ and β‐manganese(III) phthalocyanine tetracyanoethenide (1:1), [MnIIIPc]·⊕[TCNE]·⊖
Authors: Miller Joel S. , Vazquez Carlos , Calabrese Joseph C. , McLean R. Scott , Epstein Arthur J.
Published: December 2004

Cooperative magnetic interactions have been observed in α‐[MnPc][TCNE], which results from the reaction of manganese phthalocyanine with tetracyanoethylene. This is the latest in a series of molecule based materials found to exibit such unusual magnetic behaviour. The α polymorph displays very strong magnetic coupling, while the coupling in β‐[MnPc][TCNE] is much weeker. The IR data suggest that the behaviour of the α polymorph is unlikely to be unique among the metallomacrocyclic electron‐transfer complexes. It is proposed that uniformity of the one0‐dimensional chains in α‐[MnPc][TCNE] and the corresponding lack of uniformity of those in the β polymorph may give rise to the difference in behaviour.
Passivation of metals by coating with polyaniline: Corrosion potential shift and morphological changes
Authors: Wessling Berhard
Published: December 2004

Corrosion protection of metals can be obtained by coating them with polyaniline dispersions, resulting in a signifiecant and reproducible shift of the corrosion potential. Scanning electron micrograph indicate that the passivation is a multistep process, beginning with an etching stage in wh8ch grain boundaries become visible (see Figure). In the second step the metal surface is coated—non‐electrochemically—with an oxide layer. The exact mechanism of formation of this layer remains to be explored.

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Photochemical synthesis of polyacrylate–silica hybrid sol–gel materials catalyzed by photoacids
Authors: Wei Yen , Wang Wei , Yeh Jui‐Ming , Wang Bin , Yang Dachuan , Murray James K.
Published: December 2004

Photochemical synthesis of hybrid sol–gel materials is demonstrated for the first time. Photoacid‐catalyzed sol–gel reactions of tetraethyl orthosilicate with polymer precursors under ultraviolet radiation produce poly‐acrylate‐silica materials (shown schematically in the Figure). The effect of the concentrations of the photoacids and polymer precursors and the intensity of the radiation is discussed.

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Recrystallization of electrodeposited copper indium diselenide thin films in an atmosphere of elemental selenium
Authors: Guillemoles Jean François , Lusson Alain , Cowache Pierre , Massaccesi Sylvie , Vedel Jacques , Lincot Daniel
Published: December 2004

One use of copper indium dis‐ elenide (CIS) is in photovoltaic devices. Low‐cost films produced by one‐step electrodeposition could replace the co‐evaporated films used currently if their quality could be improved. It is shown that annealing such CIS films in a selenium atmosphere dramatically improves both their structural properties, as illustrated by the scanning electron micrograph. and electronic properties.

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Solar cells with improved efficiency based on electrodeposited copper indium diselenide thin films
Authors: Guillemoles Jean François , Cowache Pierre , Massaccesi Sylvie , Thouin Laurent , Sanchez Sylvie , Lincot Daniel , Vedel Jacques
Published: December 2004

Solar cells based on CuInSe2 (CIS) thin films prepared as described in the previous contribution have been prepared and characterized. The light and dark current–voltage curves and spectral responses are presented, showing that annealing in a selenium atmosphere makes it possible to fabricate ZnO/CdS/CIS solar cells with improved efficiencies. CIS is of particular interest because its optical properties are well matched to the solar spectrum.
The use of CVD diamond thin films in electrochemical systems
Authors: Swain Greg M.
Published: December 2004

The electrochemical characterization of diamond is just beginning. The study reported here deals with the growth by energy‐assisted CVD of impurity‐doped diamond electrodes (see Figure) sufficiently conductive for electrochemical measurements. The electrochemical activity of the electrodes towards various analytes, their capacitance and flat‐band potentials in several electrolytes, and their photocurrent response are discussed.

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Microfibrillar reinforced composites—new materials from polymer blends
Authors: Fakirov Stoyko , Evstatiev Michail
Published: December 2004

Microfibrillar‐reinforced composites (MFCs) are a fundamentally new type of polymer composites. MFCs are prepared by a novel technique comprising drawing a polymer blend, which leads to fibrillization (orientation of both components), followed by melting of one component while preserving the oriented structure of the higher melting point component (see Figure), This method is explained in detail by means of an example, and the mechanical parameters of an MFC are presented.

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Rocking‐chair or lithium‐ion rechargeable lithium batteries
Authors: Guyomard Dominique , Tarascon Jean‐Marie
Published: December 2004

Owing to the present exponential development of portable consumer electronics and to the increasing concern about the environment, new energy sources are required that provide more energy in the same volume and/or mass. Within a short period of time, less than three years, many changes in the area of rechargeable batteries for the consumer market have occurred, along with the emergence of several new technologies. The ubiquitous NiCd cells, which are environmentally unfriendly because of the toxicity of Cd, will be replaced by Ni‐metal hydride, rocking‐chair lithium (or Li‐ion), and lithium polymer electrolyte rechargeable cells. This paper reviews recent advances in the field of Li‐ion rechargeable batteries.
Chromophore–zeolite composites: The organizing role of molecular sieves
Authors: Caro JÜRgen , Marlow Frank , Wübbenhorst Michael
Published: December 2004

Dyes incorporated in molecular sieve crystals can reveal information about the orientation of guests in these crystals through polarization microscopy (see Figure), Raman scattering, and second‐harmonic generation measurements. Pyroelectric studies of the dye molecule para‐nitro‐aniline inserted in the molecular sieve A1P04‐5 are described that show which of two rival models explaining the ordering of guests in molecular sieves actually holds.

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Surface‐activated photopolymer microgels
Authors: Sasa Nobumasa , Yamaoka Tsuguo
Published: December 2004

Enhancement of the sensitivity of photopolymers is needed if photopolymers are to find more extensive applications in the printing and microlithography industries. A new concept is presented for sensitivity enhancement: the use of surface‐activated microgels as a heterogeneous polymer matrix. The preparation of the microgels and their effect on the polymerization rate and the sensitivity are described. Examples are given of applications of microgel‐based photopolymers as offset printing plates and photographic film.
New European Funding Opportunities for Materials Research
Authors: Hussla Ingo , Us Natasha
Published: December 2004

Funding oopportunities in Europe are changing as the Third Framework Progamme comes to an end and the preparation of the Forth Programme nears completion. Following a brief look back at how specific workprogrammes such as Brite‐Euram II and ESPRIT were organized under Framework III, details are given of how the 12.3 BECU availabel are expected to be allocated to the various activities of Framework IV. In particular, specific opportunities for materials research are listed in the areas of information technologies and industrial technologies.
Oligomeric Tetrathiafulvalenes: Extended donors for increasing the dimensionality of electrical conduction
Authors: Adam Martin , Müllen Klaus
Published: December 2004

Novel monomeric, oligomeric, and polymeric charge‐transfer complexes with interesting electrical conductivity properties and even exhibiting superconductivity are expected to be obtainable by the systematic chemical modification of extended tetrathiafulvalenes (see Figure for one example). The synthesis and cyclic voltammetric characterization of such extended donors are reviewed in detail.

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The Development of Liquid Crystal Research
Authors: Vill Volkmar
Published: December 2004

Statistics and trends in liquid crystal (LC) research are presented, taken from the new “Liqcryst” database. Did you know that more than 50000 mesogenic compounds had been studied by 1990? Or that more than 2000 papers and 1500 patents are published in the field of liquid crystals each year? Some particular breakthroughs are highlighted and the current rate of development of chiral LCs, which exhibit ferroelectric, ferrielectric, and antiferroelectric phases, is compared with that of nematic displays some years ago.
Conformational chirality of oligothiophenes in the solid state. X‐Ray structure of 3,4′,4″‐trimethyl‐2,2′:5′,2″‐terthiophene
Authors: Barbarell Giovanna , Zambianchi Massimo , Bongini Alessandro , Antolini Luciano
Published: December 2004

Chiral crystals of organic compounds have many potential applications, particularly in laser technology. The first case among oligothiophenes of chirality in the solid state is reported, the crystal structure being given along with selected NMR data and force field MM2 calculations that provide information about the conformational properties of the compound in solution. Two structural features new for α‐conjugated oligothiophenes are exhibited: a chiral space group and a crystal packing that involves short van der Waals contacts.
Processing of high‐temperature superconducting tapes
Authors: Majewski Peter
Published: December 2004

Long high‐temperature superconductor tapes have progressed immensely recently. For example, the past two years have seen a factor of five improvement in the effective critical current of (Bi,Pb)2 + xSr2Ca2Cu3O10 + d cables. The various synthesis and processing techniques are briefly reviewed and areas pointed out where much work still remains to be done, for example, on improving the mechanical properties of the silver sheath by alloying.
Ferroelectric liquid‐crystalline elastomers
Authors: Zentel Rudolf , Brehmer Martin
Published: December 2004

Liquid‐crystalline (LC) elastomers, which combine the properties of LC phases and the rubber‐like elasticity of polymer networks, are of particular interest when the LC phases exhibit ferroelectric properties. Recent work is described on monodomains of chiral smectic C elastomers produced by photo‐crosslinking. These materials are being investigated for potential applications as self‐poling piezoelements and pyrodetectors.
Lateral deposition of polypyrrole lines by means of the scanning electrochemical microscope
Authors: Kranz Christine , Ludwig Markus , Gaub Herrmann E. , Schuhmann Wolfgang
Published: December 2004

Laterally deposited polypyrrole structures have been fabricated using a scanning electrochemical microscope on conducting substrates from aqueous solution. The dimensions of the polymer lines obtained are primarily determined by the size of the electrode, opening a number of opportunities in the design of organic electronic devices and selective sensors.
Incorporation of methylene blue in NaY zeolite at crystallographically defined positions
Authors: Hoppe Rainer , Schulz‐Ekloff Günter , Wöhrle Dieter , Kirschhock Christine , Fuess Hartmut , Uytterhoeven Lieve , Schoonheydt Robert
Published: December 2004

Nanoporous structures containing dye molecules have been found to have interesting nonlinear optical properties. The various methods used for the incorporation of the guests in the host lattice result in very different positioning of the guests relative to the host structure. Here, these methods are compared for the incorporation of Methylene Blue at crystallographically, non‐random, positions. The processes are examined using X‐ray diffraction and Rietveld analysis.
Polymer ligands that can regulate reaction temperature in “smart” catalysts
Authors: Bergbreiter David E. , Mariagnanam Vimala M. , Zhang L.
Published: December 2004

“Smart” homogeneous water‐soluble catalysts whose activity is inversely dependent on the temperature is presented. The behavior of the catalysts is based on the inverse temperature dependence o the solubility of some polymers which results in high activity at low temperatures and lower activity at elevated temperatures wher the catalyst is phase separated from the continuous phase containing the substrate. The synthesis and applications of the catalysts are presented.
Nanostructures: New forms of luminescent silicon
Authors: Dag Ömer , Kuperman Alex , Ozin Geoffrey A.
Published: December 2004

The cover picture represents a 60‐atom silicon nanocluster with a diamond‐like structure, within the supercage of zeolite Y. In this article, recent developments in the chemical synthesis of novel and well‐defined nanoscale forms of luminescent silicon are reviewed and the methods used to “trick” silicon (an indirect bandgap semiconductor with electric dipole forbidden luminescence) into emitting light discussed.

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Conjugated polymers and oligomers: Designing novel materials using a quantum‐chemical approach
Authors: Brédas Jean‐Luc
Published: December 2004

Quantum chemical calculations can provide reliable information on the geometric and electronic structures of a variety of advanced materials wich can be used to design or predict their electrical or optical properties. The success of the approach does not always depend on the use of the most sophisticated calculational methods, but rather on the infomed selection of the types of calculation applied to a particular problem. The power and potential, and the potential pitfalls, of these methods are reviewed especially as applied to conjugated polymers and oligomers.
Nested interfacial growth of carbon nanotubes catalyzed by hafnium
Authors: Ata Masafumi , Yamaura Kiyoshi , Hudson Andrew J.
Published: December 2004

Carbon nanotubes containing HfC crystals (see Figure) have been synthesized during the dc arc discharge of a Hf‐composite graphite electrode. Clear evidence is presented of the Hf‐catalyzed growth of the nanotubes based on transmission electron microscope images, and the growth mechanism, which is thought to be completely different to that active in the production of vapor‐grown carbon fibers or metal catalyzed nanotubes, is discussed.

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Extended hybrid tetrathiafulvalene π‐donors with oligothienylenevinylene conjugated spacer groups
Authors: Elandaloussi El Hadj , Frère Pierre , Roncali Jean , Jubault Michel , Gorgues Alain , Richomme Pascal
Published: December 2004

Hybrid tetrathiafulvalenes (HTTFs) where the TTF units are linked by thienylenevinylene spacers (see Figure) are reported. It is found that the π donor properties of the materials are improved over analogues with oligothiophene spacers, and that they exhibit a smaller band gap. The evolution of the properties as a function of spacer length and the materials syntheses are discussed.

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Room‐temperature electrosynthesis of carbonaceous fibers
Authors: Herrick Robert D. , Kaplan Audrey S. , Chinh Beatrice K. , Shane Michael J. , Sailor Michael J. , Kavanagh Karen L. , McCreeey Richard L. , Zhao Jun
Published: December 2004

Carbonaceous fibers are produced by the room‐temperature electrochemical reduction of CCl4. These fibers (see Figure) are structurally and morphologically similar to carbon fibers produced at high temperatures, and are formed sponaneously at an electrode without the need for a template, during cathodic decomposition of CCl4 in non‐aqueous electrolytes.

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Oligo(1‐methylpyrrole)s—A model system in the conducting polymer series
Authors: Rohde Nils , Eh Marcus , Geißler Uwe , Hallensleben Manfred L. , Voigt Beate , Voigt Michael
Published: December 2004

The decrease of conductivity in poly(pyrrole)M when a substituent is introduced into the polymer either at the nitrogen or in the β positions is investigated. The drop in conductivity is two orders of magnitude by sbstitution in the 3 (β) position and five orders of magnitude when the substitution is made a nitrogen, in the 1‐position. The various factors affecting te conductivity are analyzed for a series of oligomers with between one and six pyrrole units.
The liquid‐crystalline‐state polymerization of diacetylenes
Authors: Tsibouklis John
Published: December 2004

In‐situ polymerization of liquid‐crystalline diacetylene monomers provides can easily accessible route to conjugated polymeric materials with a controlled orientation. The reaction itself is explained and recent progress made by researchers aiming to produce interestng electroactive materials or fabricate novel device structures with anisotropic mechanical, thermal, and optical properties is reviewed.
Thin polymeric films in organic/inorganic diodes
Authors: Torsi Luisa , Sabbatini Luigia , Zambonin Pier G.
Published: December 2004

The coupling of biological and chemical systems with ast electronic transducers is expected to lead to compact chemo‐ or bio‐chips which will further improve analytical detection limits. The highly controlled electrochemical deposition of thin polymeric films is a reliable method used to produce the active layers in such chips. Progress made in the application of this method in the design of devices containing layers of organic polymers in contact with inorganic semiconductors is reviewed.
Novel metallic charge‐transfer complexes composed of a [3] radialene type acceptor: A 1,2‐Bis(p‐benzoquino)‐3‐12‐(dicyanomethylene)‐2,5‐selenoquinojcyclopropane Derivative**
Authors: Takahashi Kazuko , Tarutani Shinji
Published: December 2004

Molecular metals based on the [3]radialene structure (see Fig.) as the acceptor are reported. They represent the first radialene and also the first non‐benzenoid aromatic compounds to afford molecular metals. Compressed pellets of these acceptrs complexed with TTF and TTT exhibit remarkable metallic behavior. The synthesis and the characterisation of the materials are presented

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Lithographic molding: A convenient route to structures with sub‐micrometer dimensions**
Authors: Wilbur James L. , Kim Enoch , Xia Younan , Whitesides George M.
Published: December 2004

Elastomeric stamps with submicrometer features for use in the recently reported microcontact printing procedure are produced without the need for routine access to cleanrooms. The new technique is therefore an alternative to the use of photolithography for the fabrication of the stamps, simplifying the technology required to generate structures with sub‐micrometer dimensions (e.g. see Fig.)

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Cu2O quantum‐dot particles prepared from nanostructured copper**
Authors: Knözinger Erich , Kellersohn Antje , Langel Walter , Giersig Michael
Published: December 2004

Higly disperse copper oxides are widely used as catalysts for industrial processes, for example in methanol synthesis. The supports used for these catalysts hamper their characterization of the copper oxide species involved. Here, a procedure for the preparation of unsupported, nanostructured, and pure Cu2O samples is reported. The process involved the production of nanonstructured copper and the subsequent controlled oxidation of this material.
Molecular structure of sel‐organized layers of N‐Octyl‐D‐guconamide**
Authors: Crämer Konrad , Pfannemüller Beate , Magonov Sergei N. , Kreutz Werner , Tuzov Igor
Published: December 2004

AFM images reveal deaths of self‐organized amphiphile structures of the title compound (see Fig.). Information on the morphology and the molecular order is obtained indicating that the structures are stabilized by relatively strong intermolecular interactions. The results are compared with those from studies of the same materials in gel and crystal states

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Crystal designing organic ferrimagnets**
Authors: Izuoka Akira , Kumai Reiji , Sugawara Tadashi
Published: December 2004

Controlling the structure of a molecular assembly by using a molecule carrying both a functional site and an orientation controlling site has recently been achieved. The latter site plays the role of arranging the functional molecules by utilizing hydrogen bonding interactions or charge‐transfer interactions between the orientation controlling sites. The functional molecules then self‐assemble to create highly ordered molecular architectures. The technique is explained.
Synthesis and crystal structure of a new unsymmetrical oxygen containing TTF
Authors: Moge Mikael , Hellberg Jonas , Törnroos Karl Wilhelm , von Schütz Jost‐Ulrich
Published: December 2004

Many chalcogen‐substituted derivatives of tetrathiafulvalene (TTF) are able to form metallic or even superconducting cation radical salts. The particular properties of bis(ethylenedithio)TTF (ET) prompted the synthesis of new oxygen‐containing analogues of ET. One such new molecule, ETOX, is presented, which, besides being a new π‐donor, is the first mono‐oxa derivative of ET. It is shown to be a promising donor for molecular metals and superconductors that gives cation radical salts with a variety of stoichiometries.
Transient photoconductivity in a discotic hexagonal plastic crystal
Authors: Simmerer Jürgen , Glüsen Birgit , Paulus Wolfgang , Kettner Andreas , Schuhmacher Peter , Adam Dieter , Etzbach Karl‐Heinz , Siemensmeyer Karl , Wendorff Joachim H. , Ringsdorf Helmut , Haarer Dietrich
Published: December 2004

Charge‐carrier transport in organic materials is the fundamental physical process behind devices such as laser printers. Charge‐carrier mobility data are presented for hexabutyloxytriphenylene (H4T), which exhibits an unusually high charge‐carrier mobility, which can be traced to the formation of a plastic discotic phase. The Figure shows the normal discotic hexagonal texture with six‐fold symmetry observed for H4T at 144°C; this symmetry disappears at lower temperatures (see also the cover).

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Microemulsion polymerization: New surfactant systems by counterion variation
Authors: Antonietti Markus , Hentze Hans‐Peter
Published: December 2004

Novel surfactant systems that allow the formation of polymerizable microemulsions are required for the synthesis of ultrafine polymer latices. The work reported here extends the ability to formulate new microemulsion “recipes” by means of a new approach: the geometry and polarity of a given surfactant can be adjusted by electrostatic coupling with an appropriate organic counterion, e.g., the generation of a very bulky hydrophobic head group. It is demonstrated that counterion variation of classical surfactants leads to a significant improvement of classical microemulsions.
The first crystalline hexagonal Si3N4 microtubes
Authors: Huppertz Hubert , Stock Norbert , Schnick Wolfgang
Published: December 2004

Hollow, regularly shaped hexagonal Si3N4 microtubes (see Figure) have been synthesized by reaction of cobalt metal with silicon diimide. Some are partially and some completely filled with metallic inclusions, which were identified as Co2Si. The formation of crystalline transparent filaments with non‐transparent spherical or polyhedral particles at the tip is also reported.

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Bioactive polycrystalline silicon
Authors: Canham Leigh T. , Reeves Chris L. , King David O. , Branfield Paul J. , Crabb Jim G. , Ward Michael C. L.
Published: December 2004

The bioactivity of a range of microstructured silicon materials should be assessed since it has been demonstrated that low porosity microporous silicon is “bioactive”. Work reported here shows that certain types of polycrystalline silicon are also bioactive, being corroded and exhibiting surface deposits of calcium phosphate (see Figure) when kept in simulated body fluids (SBF).

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Increased publication frequency in 1997
Authors: Gregory Peter S.
Published: December 2004

Have you noticed any changes in Advanced Materials during the last two years? These include the introduction of different cover pictures, the availability of the contents lists on the World Wide Web, and the launch of CVD, which has appeared regularly every two months since July 1995. Some changes are also in store for 1997. Details are given in the essay, together with a quick review of recent developments, for example, changes in the pattern of submission of manuscripts.
A carbon nanotube/organic semiconducting polymer heterojunction
Authors: Romero Danilo B. , Carrard Michel , De Heer Walter , Zuppiroli Libero
Published: December 2004

An all‐organic device based on carbon nanotubes and semiconducting polymers is of great interest for opto‐electronic applications. A rectifying heterojunction formed by these novel materials is reported for the first time. The onset for nonlinear current injection is demonstrated to occur at an applied electric field more than on order of magnitude lower than for a semiconducting polymer/conducting oxide or metal heterojunction. The light sensitivity of the heterojunction was also investigated.
High order and submolecular imaging of end‐capped quinquethiophene on Ag(111)
Authors: Soukopp Andreas , Glöckler Kurt , Bäuerle Peter , Sokolowski Moritz , Umbach Eberhard
Published: December 2004

Ultrathin films of functionalized oligomers with well‐defined chain and conjugation lengths are of interest for organic electronic devices. Using the example of end‐capped quinquethiophene vapor‐deposited onto a Ag(111) surface, it is demonstrated that highly ordered monolayers of chemisorbed oligomers can be obtained in very large defect‐free domains. LEED and STM (see Figure) studies provide information about the geometric parameters, molecular structure, and quality of the layers.

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Deeply colored self‐assembled multilayers of anionic DPP bolaamphiphiles and cationic polyelectrolytes
Authors: Saremi Farnaz , Lange Gabriele , Tieke Bernd
Published: December 2004

Self‐assembled ultrathin multilayer films containing DPP or DTPP chromophores are reported. The preparation of the multilayers built up out of a DPP derivative and a cationic polyelectrolyte on a silanized glass slide is described (see Figure), followed by the characterization of their optical properties. The stability of the deep red (DPP) or yellow (DTPP) films makes them particularly suitable for technical applications.

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Supramolecular fibers from a liquid crystalline octa‐substituted copper phthalocyanine
Authors: Osburn Elizabeth J. , Schmidt Albert , Chau Lai‐Kwan , Chen Si‐Ying , Smolenyak Paul , Armstrong Neal R. , O'Brien David F.
Published: December 2004

Supramolecular fibers—bundles of individual strands—result from the self‐assembly of a novel octa‐substituted copper phthalocyanine with benzyloxyethoxy side chains. The synthesis and self‐assembly of the fibers are described and results from microscopy and X‐ray characterization presented. It is shown that incorporation of aromatic groups in the side chains of phthalocyanines favors discotic mesophases with extended thermal stability, in addition to promoting the formation of supramolecular fibers.
Blue superradiance from neat semiconducting alternating copolymer films
Authors: Brouwer Hendrik Jan , Krasnikov Victor V. , Hilberer Alain , Hadziioannou Georges
Published: December 2004

Blue superradiant emission in thin polymer films with a low energy threshold, as reported here, offers hope for the possible development of solid‐state electrically pumped polymer lasers. The absorbance, emission, and fluorescence spectra of the blue‐light emitting copolymer poly[dimethylsilylene‐p‐phenylene‐vinylene‐(2,5‐di‐n‐octyl‐p‐phenylene)‐vinylene‐p‐phenylene] are presented and discussed. It is suggested that lasing in the superradiant regime occurs as a result of the combination of optically induced net gain and waveguiding in the thin film.
The interaction of poly (p‐phenylenevinylene) with air
Authors: Xing Kezhao , Fahlman Mats , Lögdlund Michael , dos Santos Doni A. , Parenté Vincent , Lazzaroni Roberto , Brédas Jean‐Luc , Gymer Richard W. , Salaneck William R.
Published: December 2004

The exposure of poly(p‐phenylenevinylene), PPV, to air affects its performance in polymer‐based light‐emitting devices. An investigation is described in which exposure to air is demonstrated to give rise to reversible affects associated with the absorption of water vapor, leading to determinal changes in the outer electronic structure (see also the cover of this issue). In particular the resulting increase in torsion angle is shown to lead to a reduction in conjugation. A method of preparing clean PPV films is proposed.
Imaging the structure of the p‐n junction in polymer light‐emitting electrochemical cells
Authors: Dick David J. , Heeger Alan J. , Yang Yang , Pei Qibing
Published: December 2004

Light‐emitting electrochemical cells (LECs) offer a new approach to light‐emitting devices fabricated from semiconducting polymers. The p‐n junction formed in situ in an LEC through electrochemical doping has been imaged in the surface cell configuration by measuring the doping profile, the electric field profile within the junction, and the electroluminescence emission profile. The methods used are described and the results interpreted to provide a detailed picture of the structure of the p‐n junction.
Thiophene‐based conjugated oligomers and polymers with high electron affinity
Authors: Ho Hoang Anh , Brisset Hugues , Elandaloussi El Hadj , Frère Pierre , Roncali Jean
Published: December 2004

The control of the bandgap of thiophene‐based polymers and oligomers has become an important topic in recent years. One strategy is the introduction of electron‐withdrawing groups in particular positions in the conjugated chain. An extension of this strategy is reported here: the synthesis and electrochemical investigation (e.g., analysis of the electropolymerization behavior) of a new series of π‐conjugated oligomers containing 3, 4, and 5 heterocycles and two CN groups at various positions of the ethylene linkage.
Lamellar semiconductor–organic nanostructures from self‐assembled templates
Authors: Osenar Paul , Braun Paul V. , Stupp Samuel I.
Published: December 2004

A templating synthesis of nanocomposite materials with lamellar morphology is described in which the unique structure of the polyol amphiphiles—leading to a highly stabilized lamellar mesophase—is exploited. The use of these mesophases in the formation of semiconducting–organic nanocomposites that copy the symmetry and spacing of the mesophase is demonstrated. It is suggested that the regular arrangement of organic and semiconducting components on the molecular length scale could lead to novel optoelectronic materials.
Self‐assembled wires and channels
Authors: van Nostrum Cornelus F.
Published: December 2004

Supramolecular wires and channels are one‐dimensional molecular materials capable of transporting charge, etc. in a predefined direction. Examples are given of wires and channels that have been formed by self‐assembly in the liquid‐crystalline state or in solution, for example from alkoxy‐substituted triphenylenes (see Figure; R = aliphatic chain), using various approaches. The underlying principles are stressed.

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Polyelectrolyte–Surfactant Complexes in the Solid State: Facile building blocks for self‐organizing materials
Authors: Ober Christopher K. , Wegner Gerhard
Published: December 2004

Even though mixtures of polyelectrolytes and surfactants are used in a variety of technologies, little is known about the solid state properties of complexes formed by the two components. Recently reported methods for preparing polyelectrolytesurfactant complexes and their solid‐state structure will be described in the context of the self‐assembly behavior of the source surfactant molecules. This facile process offers the opportunity of producing a variety of new materials with applications that may range from switchable, permselective biological membranes to fluorinated materials with non‐wetting properties. In the form of a solid‐state complex, remarkably diverse mechanical properties ranging from elastomers to crystalline solids can easily be achieved. This review discusses the growing quantity of research in this new field, and in particular, the fabrication of such complexes in the form of processable self‐doped conducting polymers is described.
Electron field emitters based on carbon nanotube films
Authors: de Heer Walt A. , Bonard Jean‐Marc , Fauth Kai , Châtelain André , Ugarte Daniel , Forró László
Published: December 2004

The excellent field emission characteristics of carbon nanotube films, i.e., the property that the tips of the nanotubes emit electrons when placed in an electric field, are discussed in some detail. The experimental configurations used (see Figure) and the results obtained are reviewed. It is suggested that carbon nanotube films should be considered as good candidates for display applications.

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Template‐directed synthesis of aragonite under supramolecular hydrogen‐bonded langmuir monolayers
Authors: Litvin Arkadi L. , Valiyaveettil Suresh , Kaplan David L. , Mann Stephen
Published: December 2004

The design of supramolecular templates to direct the synthesis of organized inorganic materials is illustrated for aragonite (CaCo3), which is metastable under ambient conditions but found in gallstones, fish otoliths, etc. Spreading of the template 5‐hexadecyloxyisophthalic acid at the air/water interface is shown to result in the specific nucleation of aragonitc (see Figure) from supersaturated calcium bicarbonate solution without additives.

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Replica molding using polymeric materials: A practical step toward nanomanufacturing
Authors: Xia Younan , McClelland Jabez J. , Gupta Rajeev , Qin Dong , Zhao Xiao‐Mei , Sohn Lydia L. , Celotta Robert J. , Whitesides George M.
Published: December 2004

The reliable fabrication of nanostructures is polymer materials, i.e. structures with feature sizes below 100 nm, is an important goal if progress in the application of such materials in electronic, magnetic, and optical devices is to be maintained. Replica molding has been used extensively to produce micrometer sized features. Here, the technique is extended to the nanometer regime such as that shown in the figure. fig.

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Solid opalescent films originating from urethanes of cellulose
Authors: Zentel Rudolf , Müiller Manfred , Keller Harald
Published: December 2004

Opalescent films of ca. 100 cm2 (see Figure and this month's cover picture) based on a renewable resource, cellulose, have been prepared. The films are based on cholesteric, semi‐interpenetrating networks which result from the crosslinking of lyotropic liquid crystalline phases of cellulose carbanilates in commercial acrylates. Photocrosslinking of the films at different temperatures allowing patterning.

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Derivatized electrodes in the construction of organic light emitting diodes
Authors: Nüesch Frank , Si‐Ahmed Lynda , François Bernard , Zuppiroli Libero
Published: December 2004

Overcoming the disadvantages of organic light‐emitting diodes (LEDs) is important if full advantage is to be taken of their benefits. It is shown that a significant increase in durability and decrease of the turn‐on operating field can be achieved by attaching the electroactive polymer to the metal‐oxide electrode chemically. The Figure shows a single‐layer LED device with an electrode derivatized with a functionalized oligophenylene layer.

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3D Long‐range ordering in ein SiO2 submicrometer‐sphere sintered superstructure
Authors: Mayoral Raul , Requena Joaquin , Moya José S. , López Cefe , Cintas Adelaida , Miguez Hernán , Meseguer Francisco , Vázquez Luis , Holgado Miguel , Blanco Álvaro
Published: December 2004

Three‐dimensional arrays of SiO2 nanometer particles lead to Bragg diffraction effects of visible light—as seen for natural opals, see also this issue's cover—and applications such as photonic bandgap materials. Teh fabrication of the opalline structures is described and details are given of how to obtain ordered compacts. The Figure shows a fracture surface of a sintered sample comprising 390 nm‐diameter silica spheres.

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Polypeptide Materials: New synthetic methods and applications
Authors: Deming Timothy J.
Published: December 2004

A review of recent developments in polypeptide synthesis is provided. This article is focused on development of new materials based on polypeptides rather than on reproduction or applications of natural protein‐based materials. Synthetic methods fall into two major categories: biological and chemical. The most successful biological approaches utilize cellular protein synthesis machinery to perform the task of assembling the polymeric molecules. Adaptation of this machinery for production of new, artificial polypeptide sequences and use of this machinery for incorporation of artificial amino acids into polypeptides have been the key recent contributions in this area. Advances in chemical polypeptide syntheses include new applications in solid and solution phase peptide coupling reactions as well as advances in the polymerization of a‐amino acid‐N‐carboxyan‐ hydride (NCA) monomers. The use of transition metal initiators in NCA polymerizations has allowed the preparation of very well defined homopolypeptides and may lead to facile routes into peptide block copolymer materials. The presence of stable, chiral structural elements in polypeptides results in self‐assembly into ordered films, composites, and liquid crystals. If their sequences are designed and constructed properly, artificial polypeptides have considerable potential for use in construction of artificial tissues and implants, ordered inorganic/organic composites, and in medical diagnostics and biosensors.
Molecular optoelectronic systems
Authors: Willner Itamar , Willner Bilha
Published: December 2004

Molecular optoelectronic devices require, first, the design of a molecular entity whose chemical functions are reversibly triggered by external light signals and, second, integration with a solid support capable of electronic transduction of the photostimulated chemical processes at the molecular level. Two ways of functionalizing electrode surfaces are reviewed that fulfill these requirements, including a chemical system that mimics the function of a logic “AND”, i.c., an amplified amperometric signal is obtained only when two conditions are mct simultaneously.
Improved field‐effect mobility in short oligothiophenes: Quaterthiophene and quinquethiophene
Authors: Hajlaoui Riadh , Horowitz Gilles , Garnier Francis , Arce‐Brouchet Alexandre , Laigre Laurent , Kassmi Ahmed El , Demanze Frédéric , Kouki Fayçal
Published: December 2004

Organic field effect transistors (OFETs) made from quaterthiophene (4T) and quinquethiophene (5T) have been fabricated with greatly enhanced field‐effect mobilities. It is shown that the problem seems to lie in achieving efficient charge injection rather than in poor charge transport within the material. Dopping of the drain and source contacts with a thin layer of the electron acceptor TCNQ is demonstrated to improve charge injection in 4T devices. Other factors affecting performance are considered briefly.
Poly(propyleneimine) dendromesogens with hexagonal columnar mesophase
Authors: Cameron James H. , Facher Andreas , Lattermann Günter , Diele Siegmar
Published: December 2004

Dendritic mesogens—dendrimers that form mesophases—are the third group of liquid crystalline polymers (LCPs), following main‐chain and side‐chain LCPs. The synthesis of a series of different generations of dendromesogens (see Figure) is reported and their thermal behavior, molecular shape, and the textures observed by polarizing microscopy described. The role of hydrogen bonds in the formation of such mesophases is discussed.

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Mesoporous materials by templating of liquid crystalline phases
Authors: Goltner Christine G. , Antonietti Markus
Published: December 2004

The first mesoporous materials (pore diameter between 20 and 100 Å) were discovered just five eyars ago. A new approach to mesoporous materials by direct templating of lyotropic liquid crystals is reviewed and compared with strategies reported previously. The direct templating method is shown to be very verstile. It is suggested that the resulting materials can almost be termed “second generation” mesoporous materials, mesoporous materials, owing to the broad variety of mesoporous structure and size, high degree of ordering, and low incidence of defects.
Nanofibers
Authors: Liu Guojun
Published: December 2004

The preparation of nanofibers—fibers with nanometer diameters—is briefly reviewed. Particular attention is paid to the synthesis based on locking‐in the mesophasic structures formed by diblock copolymers. Examples of the resulting nanofibers with a core‐shell structure (prepared for transmission electron microscopy by a freeze‐drying method) are shown in the Figure.

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Poly(3,4‐ethylenedioxythiophene) (PEDOT) prepared via electrochemical polymerization of EDOT, 2,2′‐Bis(3,4‐ethylenedioxythiophene) (BiEDOT), and their TMS derivatives
Authors: Sotzing Gregory A. , Reynolds John R. , Steel Peter J.
Published: December 2004

The low potential, redox‐active, highly stable conducting polymer PEDOT (poly(3,4‐ethylenedioxythiophene)) has received much attention recently because of these properties, which are likely to lead to many applications. Here the synthesis of EDOT‐TMS2 is reported (where TMS stands for trimethylsilyl and Bi indicates bis), together with the investigation of the electrochemical polymerization of these monomers using voltammetry and the electrochemical quartz crystal microbalance. The optical switching rates of the films on indium tin oxide are compared, showing that derivatization with TMS leads to improved characteristics.
Dopant Electromigration in Semiconductors
Authors: Cahen David , Chernyak Leonid
Published: December 2004

A doped semiconductor can be viewed as a mixed electronic‐ionic conductor, with the dopants as mobile ions. Normally the temperature range where this becomes true is not even close to that where the (opto)electronic properties of the material are of interest. However, notable exceptions exist and these are reviewed here, with special emphasis on those cases where semiconductivity is preserved when the (mobile) dopant concentration changes and ambipolar behavior can be obtained by dopant mobility. Dopant diffusion and drift are of interest not only in materials such as Si:Li, known from its use in radiation detectors, but also in other semiconductors, ranging from II‐VIs and related compounds, such as (Hg,Cd)Te and CuInSe2 to III‐Vs and potential high temperature semiconductors, such as diamond. Better understanding of the phenomena is important also because of the implications that it has for device miniaturization, as dopant diffusion and drift put chemical limits to device stability. Such understanding can also make dopant electromigration useful for low‐temperature doping. Some basic theory for electric‐field‐induced dopant migration is given and compared to experiments.
Entrapment of biocatalysts in hydrophobic sol‐gel materials for use in organic chemistry
Authors: Reetz Manfred T.
Published: December 2004

Lipases trapped in hydrophobic organic/inorganic materials result in chemically and thermally stable heterogeneous catalysts that display unusually high catalytic activities. The entrapment of lipases and other biocatalysts by sol‐gel encapsulation is an interesting approach to enzyme immobilization, which has the aim of increasing enzyme activity in organic solvents. Investigations that have been carried out to optimize encapsulation and to characterize the lipase‐containing gels are reviewed. Possible applications in organic synthesis are indicated.
Direct determination of the emission zone in a polymer light‐emitting diode
Authors: Grüner Johannes , Remmers Marcus , Neher Dieter
Published: December 2004

Many operating mechanisms of polymer light‐emitting diodes (LEDs) are still not fully understood, among them the crucial step of recombination of oppositely charged carriers to form excitons. Questions related to this step are: What is the shape of the recombination zone and what is the quenching loss at the metal electrode layers? An investigation is reported in which the emission zone is directly determined by analyzing the polarization of teh electroluminescence. It is shown that exciton quenching near the electrodes is a crucial parameter for the overall device efficiency.