bluuebunny/crossref_metadata_2025_split huggingface dataset:
Green Electroluminescence in Poly‐(3‐cyclohexylthiophene) light‐emitting diodes
Authors: Berggren Magnus , Gustafsson Göran , Inganäs Olle , Andersson Mats R. , Wennerström Olof , Hjertberg Thomas 
Published: December 2004

Electoluminescent devices based on polythiophene‐system this films have been demonstrated that together span the entire visible range, steric hindrance being used to vary the bandgap between compunds. Poly‐(3‐cyclohexylthiophene), see Figures, exhibits green electoluminescence. Possible interpretations of this observation are proposed. magnified image
Novel Ultrahard Materials
Authors: Riedel Ralf 
Published: December 2004

Superhard materials are needed to replace diamond in applications at high temperatures, where diamond is unstable. Novel carbon‐ and boron‐based materials are described whose discovery or postulation has greatly stimulated research in this area. The use of calculations to predict the properties of new materials is illustrated for B‐C3N4, which was synthesized only after its structure (see Figure) had been calculated. magnified image
Localized incorporation of lanthanum carbide crystals in carbon nanotubes
Authors: Ata Masafumi , Kijima Yasunori , Hudson Andrew J. , Imoto Hiroshi , Matsuzawa Nobuyuki , Takahashi Noboru 
Published: December 2004

Carbon nanotubes containing lanthanum carbide suggest that lanthanum may show catalytic activity for the formation of nanotubes. Images of the graphitic structures growing on the surface of silver‐colored deposits such as the SEM image of a straight carbon nanotube shown in the Figure, are presented. magnified image
Microfabrication by microcontact printing of self‐assembled monolayers
Authors: Wilbur James L. , Kumar Amit , Kim Enoch , Whitesides George M. 
Published: December 2004

Microcontact printing, is described. It offers extreme experimental simplicity and flexibility, relying on the ability of self‐assembled monolayers (SAMs) of longchain alkanethiolates on gold and other metals to act as nanometer resists. The Figure is an electron micrograph of a silicon microstructure resulting from chemical etching of a patterned SAM. magnified image
Opening and purification of carbon nanotubes in high yields
Authors: Hiura Hidefumi , Ebbesen Thomas W. , Tanigaki Katsumi 
Published: December 2004

Gram‐quantities of pure carbon nanotubes (see Figure) can be produced using a new method reported here. The nanotubes, which can be thought of as cylindrical graphitic microcrystals, are opened and purified by treating them with a mixtue of sulfuric acid and potassium permanganate. The opening of the nanotubes on a large scale is also of interest in terms of filling the tubes with interesting guest molecules. magnified image
Electrochemistry using plasma
Authors: Ogumi Zempachi , Uchimoto Yoshiharu , Takehara Zen‐ichiro 
Published: December 2004

A glow‐discharge plasma, because of the presence of ions and electrons and because of its potentially high conductivity, can be seen as a conductive fluid which could be used in an electrochemical system. Electrochemistry using such a plasma (see Figure) has bee demonstrated and here its basis and applications, for example in thin film deposition, are discussed. magnified image
Silicon wafer bonding via designed monolayers**
Authors: Gösele Ulrich , Steinnkirchner Johann , Martini Torsten , Reiche Manfred , Kästner Gerhard 
Published: December 2004

Silicon wafer bonding is a technology which allows two silicon wafers to stick together without any glue (e.g. see Fig.). The technique is used in the areas of microelectronics, micromechanics, and power electronics. Hydrolyzed tetramethoxysilane is used in he new bonding process presented here, providing a low‐temperature method of wafer bonding compatible with the presence of microelectronics aluminum metallization magnified image.
Rapid switching solid state electrochromic devices based on complementary conducting polymer films
Authors: Sapp Shawn A. , Sotzing Gregory A. , Reddinger Jerry L. , Reynolds John R. 
Published: December 2004

New electrochromic materials (ECMs) must exhibit rapid response times, long‐term stability, and a large difference in percentage transmittance between the bleached and colored states. The design, fabrication, and characterization of fast, solid‐state, dual conducting polymer EC devices that utilize PEDOT (see Figure) as the cathodically coloring material are described, following background information on ECMs. magnified image
The mobility of charge carriers in all four phases of the columnar discotic material hexakis(hexylthio)triphenylene: Combined TOF and PR‐TRMC results
Authors: van de Craats Anick M. , Warman John M. , de Haas Matthijs P. , Adam Dieter , Simmerer Jürgen , Haarer Dietrich , Schuhmacher Peter 
Published: December 2004

Peripherally alkyl‐substituted aromatic molecules are of interest because they are predicted to promote the rapid vectorial conduction of electronic charge. It is shown—using the example of HHTT, see Figure—that the results obtained by flash‐photolysis time‐of‐flight conductivity and pulse‐radiolysis time‐resolved microwave conductivity measurements are complementary, allowing the charge‐carrier mobility to be determined in all four phases of HHTT. magnified image
Laser action in poly (m‐phenylenevinylene‐co‐2,5‐dioctoxy‐p‐phenylenevinylene)
Authors: Holzer Wolfgang , Penzkofer Alfons , Gong Sung‐Huan , Bleyer Andreas , Bradley Donal D. C. 
Published: December 2004

The lasing action of a new conjugated copolymer in tetrahydrofuran (THF), xylene, toluene, and chloroform is reported. The title copolymer differs from many of the other conjugated copolymers that have been studied in that it includes meta‐linked phenylene rings in its backbone (see Figure). The results presented—e.g., lasing threshold energy of 25 μJ, spectral halfwidth of 8 nm in THF, an expected wide tuning range—hold promise for the realization of solid state polymer lasers. magnified image
Gold particle generation by spray pyrolysis
Authors: Majumdar Diptarka , Kodas Toivo T. , Glicksman Howard D. 
Published: December 2004

Phase‐pure, micrometer‐sized, spherical gold particles(see Figure) have been generated for the first time by spray pyrolysis of gold nitrate at temperatures well below the melting point of gold. The effects of reaction atmosphere, temperature, and residence time on the morphology of the final product are described. The resulting gold powder is shown to be suitable for a variety of microelectronics applications.magnified image
Columnar discotics for light emitting diodes
Authors: Wendorff Joachim H. , Christ Thomas , Glüsen Birgit , Greiner Andreas , Kettner Andreas , Sander Roland , Stümpflen Volker , Tsukruk Vladimir V. 
Published: December 2004

The suitability fo columnar discotics for applications in light emitting diodes (LEDs) has been investigated following the demonstration of their unusually large charge carrier mobilities. Results of X‐ray diffraction, computer simulations, and electroluminescence measurements are presented and discussed for discotic systems such as that shown in the Figure. Their use in LEDs is expected to the advantageous. magnified image
Dipolar NLO‐phores with large off‐diagonal components of the second‐order polarizability tensor
Authors: Wolff J. Jens , Längle Daniela , Hillenbrand Daniela , Wortmann Rüdiger , Matschiner Ralf , Glania Christoph , Kramer Peter 
Published: December 2004

A new class of nonlinear optical chromophores (NLO‐phores) with large off‐diagonal components of the second‐order polarization and remarkable transparency properties have been investigated. The synthesis and NLO characterization of a series of C2n symmetry benzene derivatives, such as that shown in the Figure, are described. The results of UV‐vis, EFISH, hyper‐Rayleigh scattering, etc., measurements are compared. magnified image
Electrodeposited quantum dots: Coherent nanocrystalline cdse on oriented polycrystalline au films
Authors: Golan Yuva , Alperson Boaz , Hutchison John L. , Hodes Gary , Rubinstein Israel 
Published: December 2004

The formation of highly coherent nanocrystalline semiconductor films on polycrystalline metal substrates has important practical and theoretical implications. Electron diffraction patterns reveal that quantum dots (QDs) of CdSe grown on a gold film on a mica substrate are coherent over several micrometers in the lateral directions (see Figure), while in the case of a glass substrate there is a complete loss of epitaxy for QD layers not in direct contact with the gold. Fig.magnified image
Liquid crystalline macrocycles: Novel glass‐forming nematic materials that can undergo charge transfer induced phase transitions
Authors: Neumann Bernhard , Joachimi Detlev , Tschierske Carsten 
Published: December 2004

Macrocyclic liquid crystals incorporating two different rigid cores are reported for the first time. The synthesis of polyethercyclophanes such as that shown in the Figure is described, together with their phase behavior as investigated by differential scanning calorimetry and polarizing microscopy. The synthesis of macrocycles that combine non‐identical building blocks is describe in order to obtain materials with tailor‐made properties. magnified image
Blue and green light emission from new soluble alternating copolymers
Authors: Cho Hyun Nam , Kim Dong Young , Kim Young Chul , Lee Jun Young , Kim Chung Yup 
Published: December 2004

Visible‐light‐emitting alternating copolymers consisting of two different repeat units have been investigated. The synthesis and optical characterization of PDHFPPV (top in Figure) and PDHEMPV (bottom in Figure) are described. It is shown that these soluble copolymers can be used as the active layer in light‐emitting diodes, just like the corresponding homopolymers. magnified image
Concerted transport of electrons and protons across conducting polymer membranes
Authors: Matsumura Michio , Ohno Teruhisa 
Published: December 2004

The efficient conversion of light energy into chemical energy is essential if solar energy is to be utilized successfully. The mechanisms of photosynthesis in green plants are used as guiding principles to propose different types of electron and proton transporting systems, for example, a chemical system based on polyaniline film, an electrochemical system using doped polypyrrole film, and the photochemical system shown in the Figure. Fig.magnified image
Phasmids and Polycatenar Mesogens
Authors: Nguyen Huu‐Tinh , Destrade Christian , Malthécte Jacques 
Published: December 2004

Polycatenar mesogens have a shape intermediate between classical rod‐like and disc‐like liquid crystals which allows practically all the mesomorphic symmetrics to be obtained with the same molecular core by varying the temperature or the number and position of grafted chains (see Figure: R = H(CH2)nO). The synthesis, mesomorphic properties, and structures of polycatenar mesogens are reviewed, with emphasis on the structure–properties relationship. magnified image
Synthesis of nanometer‐scale silver crystallites via a room‐temperature electrostatic spraying process
Authors: Hull Peter J. , Hutchison John L. , Salata Oleg V. , Dobson Peter J. 
Published: December 2004

Thin films of silver nanoparticles have been prepared by a room temperature electrospraying technique—the apparatus is shown schematically in the Figure. The characterization of the particles by optical absorption spectroscopy and high‐resolution transmission electron microscopy is described. The behavior is compared with theory and a tentative mechanism proposed for the reduction of the silver. magnified image
Three‐dimensional hexagonal close‐packed superlattice of passivated Ag nanocrystals
Authors: Harfenist Steven A. , Wang Zhong L. , Whetten Robert L. , Vezmar Igor , Alvarez Marcos M. 
Published: December 2004

Superlattices of self‐assembled Ag nanocrystals have been prepared and the structure analyzed using a combination of techniques. It is shown that the supercrystals are hexagonally close‐packed, attributed to a high proportion of icosahedral and decahedral particles. The Figure (a TEM image of the Ag supercrystals) illustrates that the crystals formed are predominantly triangular in morphology and can be as large as 3–5 μm. magnified image
Purification and size‐selection of carbon nanotubes
Authors: Bonard Jean‐Marc , Stora Thierry , Salvetat Jean‐Paul , Maier Frédéric , Stöckli Thömas , Duschl Claus , Forró László , de Heer Walt A. , Châtelain André 
Published: December 2004

A non‐destructive method for purifying carbon nanotubes produced by are discharge is described. The nanotubes, in the form of a kinetically stable colloidal dispersion in a water–surfactant solution, are separated from the nanoparticles by filtration. The Figure shows that purified nanotubes after two filtration steps. Through controlled flocculation, nanotube size election is also possible. magnified image
Solid‐state Carbon Nitrides
Authors: Badding John V. 
Published: December 2004

AbstractWhether crystalline or amorphous sp3‐bonded carbon nitrides containing substantial amounts of nitrogen can be synthesized remains an open question. Various deposition techniques and high pressure syntheses to 40 GPa have not been successful thus far. The use of appropriately designed molecular or solid‐state precursors and low enough synthesis temperatures to insure kinetic control of reaction products appears to be a promising direction for future efforts. In addition, synthesis at higher pressures, which can effect larger shifts in free energies of reaction should be pursued. The importance of careful characterization to obtain structural (by means of electron or X‐ray diffraction), compositional (by means of EELS, EDX, or RBS), and, especially, bonding (by means of EELS) information on single‐phase material cannot be overemphasized. Because few examples are known of covalently bonded networks containing carbon, synthesis of a sp3‐bonded carbon nitride would be a spectacular achievement.
Photorefractive materials for holographic interferometry
Authors: Schloter Stefan , Haarer Dietrich 
Published: December 2004

The photorefractive properties of polymersfor holographic interferometry are currently often better than those of their inorganic counterparts. The theory of the photorefractive effect is briefly outlined before the relevant experimental techniques and chemical approaches are reviewed. Applications are mentioned, for example the possibility of visualizing vibrations as a fringe pattern (see Figure).magnified image
Imaging polymers with supercritical carbon dioxide
Authors: Ober Christopher K. , Gabor Allen H. , Gallagher‐Wetmore Paula , Allen Robert D. 
Published: December 2004

In lithographic techniques for forming nanostructures in surface and polymer thin films, the selectivity of the solvent becomes increasingly important as the target dimensions decrease. Polymer‐based developers. The Figure shows the SC CO2–developed image of a copolymer of pentafluoroproyl methacrylate and tert‐butyl methacrylate.magnified image
Impurity survey analysis of CdxHgi−xTe by laser scan mass spectrometry
Authors: Grainger F. , Gale I. G. , Capper P. , Maxey C. D. , Mackett P. , O'Keefe E. , Gosney J. 
Published: December 2004

AbstractA laser scan mass spectrometry (LSMS) technique has been applied to the analysis of epitaxial layers and bulk CdxHg1−xTe (CMT) materials. The samples are raster scanned under a focused Q‐switched Nd–YAG laser beam which ionises all elements with approximately unit sensitivity. The ions are extracted into a high‐resolution mass spectrometer and interpretation of the mass spectra gives a complete impurity survey of the material with detection limits down to 1 part in 109 (3 × 1013 cm−1) in bulk materials and 5 parts in 109 in epitaxial layers. Surface impurities are effectively removed in the first scan and subsequent scans over the same area give a true measurement of the impurities present in the material. Successive erosion of the sample surface gives impurity depth profiles with the thickness of material eroded in each scan variable between 1 and 4 μm. Results are given for impurities found in bulk CMT grown by standard Bridgman and ACRT (accelerated crucible rotation technique) processes and in epitaxial CMT produced by liquid phase epitaxy (LPE), metal organic vapour phase epitaxy (MOVPE) and molecular beam epitaxy (MBE). Bulk material is shown to be purer in general than epitaxial material. Semiquentitative depth profiles of dopants in CMT, such as iodine, arsenic and phosphorus, can also be obtained and comparative LSMS and secondary ion mass spectrometry (SIMS) depth profiles showing good agreement are given for arsenic in an MOVPE layer.
Deposition, annealing and characterisation of high‐dielectric‐constant metal oxide films
Authors: Treichel H. , Mitwalsky A. , Tempel G. , Zorn G. , Bohling D. A. , Coyle K. R. , Felker B. S. , George M. , Kern W. , Lane A. P. , Sandler N. P. 
Published: December 2004

AbstractFlims of metal oxides, such as Ta2O5, Nb2O5, Al2O3, HfO2, ZrO2 and TiO2 have been fabricated by use of different precursor materials, deposition techniques and annealing techniques. Several analytical methods were applied to study the layers. New data of fundamental properties of these metal oxides are reported and related to practical features that are of importance in device design and manufacturing of advanced, highly integrated devices. This overview may facilitate the choice of an optimal combination of precursor material, deposition technique and corresponding annealing procedure for a specific application of these metal oxide films in microelectronics.
Capillary physiology and drug delivery in central nervous system lymphomas
Authors: Warnke Peter C. , Timmer Jens , Ostertag Christoph B. , Kopitzki Klaus 
Published: December 2004

AbstractTo evaluate whether the chemosensitivity of primary central nervous system lymphomas to water‐soluble drugs could result from improved drug delivery, we quantitatively assessed pharmacokinetic factors in seven patients. The capillary permeability surface product was found to be significantly increased in central nervous system lymphomas compared with glioblastoma multiforme, medulloblastomas, and metastases. Tumoral blood flow was significantly greater than in normal white matter. Our results suggest favorable pharmacokinetics to water‐ and lipid‐soluble drugs in primary central nervous system lymphomas. Ann Neurol 2005;57:136–139
Conformational aspects of polypeptides. XVII. Synthesis of oligomers and co‐oligomers derived from L‐alanine and L‐glutamic acid
Authors: Goodman Murray , Langsam Michael 
Published: December 2004

AbstractA series of oligomers was synthesized of the form:

Where Z is the benzyloxycarbonyl group and n = 2, 3, 5, 10. We encountered difficulty in dissolving the decamer in any solvent except strong organic acids. We therefore prepared co‐oligomers of the type:

equation image

where (a) w = x = y = 1; (b) w = 0, x = y = 3; and (c) w = x = y = 3. A series of model compounds composed of glycine L‐alamine and γ‐methyl‐L‐glutamate were also prepared. We converted manyof the benzyloxycarbonyl oligopeptides into their corresponding acetyl derivatives. Some of these peptides were synthesized by mixed anhydride and active ester techniques while others were prepared via azide coupling techniques using the tert‐butoxycarbonylhydrazide blocking group. All reactions proceeded with retention of configuration.
Some water‐insoluble papain derivatives
Authors: Silman Israel H. , Albu‐Weissenberg Martin , Katchalski Ephraim 
Published: December 2004

AbstractA description is given of the preparation and properties of four water‐insoluble papain derivatives by three different techniques: (a) covalent binding to a water‐insoluble diazoimitn salt derived from a copolymer of p‐aminophenylalanine and leucine; (b) binding to insoluble preparations of collagen via bisdiazobenzidine‐2,2′‐disulfonic acid; (c) in‐solubilization by crosslinking the enzyme itself with bisdiazobenzidine. By all three methods it, was possible to obtain stable water‐insoluble papain derivatives retaining much of the activity of the native enzyme on low and high molecular weight substrates.
Optical rotatory dispersion studies of poly‐O‐acetyl‐γ‐hydroxy‐L‐proline forms I and II
Authors: Fasman Gerald D. 
Published: December 2004

AbstractPoly‐O‐acetyl‐hydroxy‐L‐proline, forms I and II have been studied by optical rotatory dispersion (ORD) and ultraviolet spectrophotometry in solution and in the solid state. Cotton effects of opposite sign, but not mirror images, were observed in the 250 mμ region for the two forms (Form I, peak 278 mμ; crossover, 254 mμ; trough, 244 mμ: Form II, trough 270 mμ; crossover, 248 mμ; peak, 238 mμ). Thus, the Cotton effects for a right‐handed and left‐handed helix have been shown to be opposite for the proline type helices I and II. The ORD of films of form I was found to have a positive Cotton effect further into the ultraviolet region with peak at 218 mμ. Absorption spectra showed a shift of 8 mμ in the absorption peak in the 200 mμ region for the two forms (form. I, 211 mμ; form II, 203 mμ). A shoulder was demonstrated in the film absorption spectra in the 250 mμ region where the Cotton effects are found. The mixing of the n, π* and π, π* states of the amide chromophore and n, π* state of the ester chromophore was suggested as being responsible for the Cotton effects in the 250 mμ region.
pH‐Induced conformational changes of DNA
Authors: Costantino L. , Vitagliano V. 
Published: December 2004

AbstractThe electrophoretic mobility of calf thymus DNA has been measured in aqueous buffered solutions as a function of pH. In the pH range 3.7–3.0, two electrophoretic species appear. The faster one migrates with the mobility of native DNA, the slower one migrates with a mobility close to that of thermally denatured DNA. The ratio of the two species varies with pH. Decreasing the pH increase the relative amount of the slower‐moving component. These results may be interpreted by assuming that the DNA used in these experiments has a broad heterogeneity of base composition and that the conformational stability with respect to pH increases with increasing G + C content.
Conformational transition of poly(L‐glutamic acid) in aqueous solution
Authors: Barone G. , Crescenzi V. , Quadrifoglio F. 
Published: December 2004

AbstractFurther direct evidences are given that a clear correlation exists between potentiometric and spectroscopic measurements in monitoring the poly(L‐glutamic, acid) helix+ coil transtition. Specific Li+ ion poly (L‐glUtamic acid) interactions have been observed, suresting that Li+ ions may exert a distinct destabilizing action on the helical conformation of the polyelectrolyte.