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Excellent Stability (excellent + stability)
Selected AbstractsNovel ZrInZnO Thin-film Transistor with Excellent StabilityADVANCED MATERIALS, Issue 3 2009Jin-Seong Park Novel ZrInZnO semiconductor materials to resolve transistor instability for active-matrix organic light-emitting diodes are proposed. The ZrInZnO film is preprared using a cosputtering method, and presents a nanocrystal structure embedded in an amorphous matrix. The thin-film transistors fabricated have good electrical performances as well as excellent stability under long-term bias stresses. [source] The effect of whole-body tilt on sound lateralizationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2002Jörg Lewald Abstract The effect of passive whole-body tilt in the frontal plane on the lateralization of dichotic sound was investigated in human subjects. Pure-tone pulses (1 kHz, 100 ms duration) with various interaural time differences were presented via headphones while the subject was in an upright position or tilted 45° or 90° to the left or right. Subjects made two-alternative forced-choice (left/right) judgements on the intracranial sound image. During body tilt, the auditory median plane of the head, computed from the resulting psychometric functions, was always shifted to the upward ear, indicating a shift of the auditory percept to the downward ear, that is, in the direction of gravitational linear acceleration. The mean maximum magnitude of the auditory shift obtained with 90° body tilt was 25 µs. On the one hand, these findings suggest a certain influence of the otolith information about body position relative to the direction of gravity on the representation of auditory space. However, in partial contradiction to previous work, which had assumed existence of a significant ,audiogravic illusion', the very slight magnitude of the present effect rather reflects the excellent stability in the neural processing of auditory spatial cues in humans. Thus, it might be misleading to use the term ,illusion' for this quite marginal effect. [source] Microstructure and Properties of Pressureless Sintered HfB2 -Based Composites with Additions of ZrB2 or HfC,ADVANCED ENGINEERING MATERIALS, Issue 10 2007L. Silvestroni Ternary HfB2 -ZrB2 and HfB2 -HfC composites (see figure) with 20,vol.-% MoSi2 were produced from commercial powder and densified through pressureless sintering. Dense materials with fine microstructures were obtained at 1900,1950,°C. Flexural strength at 1500,°C confirmed the excellent stability of the composites at high temperature. [source] Polydisperse Spindle-Shaped ZnO Particles with Their Packing Micropores in the Photoanode for Highly Efficient Quasi-Solid Dye-Sensitized Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Yantao Shi Abstract In this paper, a novel hierarchically structured ZnO photoanode for use in quasi-solid state dye-sensitized solar cells (DSCs) is presented. The film is composed of polydisperse spindle-shaped ZnO particles that are prepared through direct precipitation of zinc acetate in aqueous solution. Without additional pore-forming agents, the microporous structure is well constructed through the packing of polydisperse ZnO particles. In the film, small ZnO particles are able to improve interparticle connectivity and offer a large internal surface area for sufficient dye-adsorption; on the other hand, particles of larger size can enhance the occurrence of light-scattering and introduce micropores for the permeation of quasi-solid state electrolytes. Meanwhile, morphologies, particle size, and specific areas of the products are controlled by altering the reactant concentration and synthetic temperature. Combined with a highly viscous polymer gel electrolyte, a device based on this ZnO photoanode shows high conversion efficiencies, 4.0% and 7.0%, under 100 and 30,mW cm,2 illumination, respectively. Finally, the unsealed device is demonstrated to remain above 90% of its initial conversion efficiency after 7 days, showing excellent stability. [source] Superparamagnetic Hyperbranched Polyglycerol-Grafted Fe3O4 Nanoparticles as a Novel Magnetic Resonance Imaging Contrast Agent: An In Vitro AssessmentADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Liang Wang Abstract Hyperbranched polyglycerol-grafted, magnetic Fe3O4 nanoparticles (HPG-grafted MNPs) are successfully synthesized by surface-initiated ring-opening multibranching polymerization of glycidol. Reactive hydroxyl groups are immobilized on the surface of 6,9,nm Fe3O4 nanoparticles via effective ligand exchange of oleic acid with 6-hydroxy caproic acid. The surface hydroxyl groups are treated with aluminum isopropoxide to form the nanosized macroinitiators. The successful grafting of HPG onto the nanoparticles is confirmed by infrared and X-ray photoelectron spectroscopy. The HPG-grafted MNPs have a uniform hydrodynamic diameter of (24.0,±,3.0) nm, and are very stable in aqueous solution, as well as in cell culture medium, for months. These nanoparticles have great potential for application as a new magnetic resonance imaging contrast agent, as evidenced by their lack of cytotoxicity towards mammalian cells, low uptake by macrophages, excellent stability in aqueous medium and magnetic fields, and favorable magnetic properties. Furthermore, the possibility of functionalizing the hydroxyl end-groups of the HPG with cell-specific targeting ligands will expand the range of applications of these MNPs. [source] Photoresponse Properties of CdSe Single-Nanoribbon Photodetectors,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2007Y. Jiang Abstract Photodetectors are fabricated from individual single-crystal CdSe nanoribbons, and the photoresponse properties of the devices are studied systematically. The photodetector shows a high sensitivity towards excitation wavelength with a sharp cut-off at 710,nm, corresponding to the bandgap of CdSe. The device exhibits a high photo-to-dark current ratio of five orders of magnitude at 650,nm, and can function with excellent stability, reproducibility, and high response speed (<,1,ms) in a wide range of switching frequency (up to 300,Hz). The photocurrent of the device shows a power-law dependence on light intensity. This finding together with the analysis of the light intensity-dependent response speed reveals the existence of various traps at different energy levels (shallow and deep) in the bandgap. Coating with a thin SiO2 isolating layer increases the photocurrent but decreases the response speed of the CdSe nanoribbon, which is attributed to reduction of recombination centers on ribbon surface. [source] High Molar Extinction Coefficient Ion-Coordinating Ruthenium Sensitizer for Efficient and Stable Mesoscopic Dye-Sensitized Solar Cells,ADVANCED FUNCTIONAL MATERIALS, Issue 1 2007D. Kuang Abstract Ru(4,4-dicarboxylic acid-2,2,-bipyridine) (4,4,-bis(2-(4-(1,4,7,10-tetraoxyundecyl)phenyl)ethenyl)-2,2,-bipyridine) (NCS)2, a new high molar extinction coefficient ion-coordinating ruthenium sensitizer was synthesized and characterized using 1H,NMR, Fourier transform IR (FTIR), and UV/vis spectroscopies and cyclic voltammetry. Using this sensitizer in combination with a nonvolatile organic-solvent-based electrolyte, we obtain a photovoltaic efficiency of 8.4,% under standard global AM,1.5 sunlight. These devices exhibit excellent stability when subjected to continuous thermal stress at 80,°C or light soaking at 60,°C for 1000,h. An electrochemical impedance spectroscopy study revealed that device stability is maintained by stabilizing the TiO2/dye/electrolyte and Pt/electrolyte interface during the aging process. The influence of Li+ present in the electrolyte on the device photovoltaic parameters was studied, and the FTIR spectral and photovoltage transient study showed that Li+ coordinates to the triethyleneoxide methylether side chains on the K60 sensitizer molecules. [source] High-Performance Solution-Processable Poly(p -phenylene vinylene)s for Air-Stable Organic Field-Effect TransistorsADVANCED FUNCTIONAL MATERIALS, Issue 5 2005Abstract The influence of the substitution pattern (unsymmetrical or symmetrical), the nature of the side chain (linear or branched), and the processing of several solution processable alkoxy-substituted poly(p -phenylene vinylene)s (PPVs) on the charge-carrier mobility in organic field-effect transistors (OFETs) is investigated. We have found the highest mobilities in a class of symmetrically substituted PPVs with linear alkyl chains (e.g., R1, R2,=,n -C11H23, R3,=,n -C18H37). We have shown that the mobility of these PPVs can be improved significantly up to values of 10,2,cm2,V,1,s,1 by annealing at 110,°C. In addition, these devices display an excellent stability in air and dark conditions. No change in the electrical performance is observed, even after storage for thirty days in humid air. [source] Fluorene-Based Oligomers for Highly Efficient and Stable Organic Blue-Light-Emitting DiodesADVANCED MATERIALS, Issue 23 2009Chang-Gua Zhen Highly efficient and stable blue-light-emitting materials consisting of oligofluorenyl blocks and charge transporting segments are synthesized. The external quantum efficiencies of the solution-processed light-emitting diodes were of up to 6.1% and 8.6% for undoped and doped devices, respectively. The exceedingly high efficiency and excellent stability of these devices suggest that these new developed materials are very promising for deep-blue-light OLEDs. [source] Novel ZrInZnO Thin-film Transistor with Excellent StabilityADVANCED MATERIALS, Issue 3 2009Jin-Seong Park Novel ZrInZnO semiconductor materials to resolve transistor instability for active-matrix organic light-emitting diodes are proposed. The ZrInZnO film is preprared using a cosputtering method, and presents a nanocrystal structure embedded in an amorphous matrix. The thin-film transistors fabricated have good electrical performances as well as excellent stability under long-term bias stresses. [source] Photoconductivity of a Single Small-Molecule Organic Nanowire,ADVANCED MATERIALS, Issue 12 2008Xiujuan Zhang The photoconductivity of a methyl squarylium (MeSq) single-nanowire device shows a high light sensitivity, wavelength-dependent photoresponse, good response speed, and excellent stability and reproducibility. Nanodevices fabricated on flexible substrates (see figure) exhibit good mechanical bendability and no obvious change in performance after bending to a curvature of 0.5,cm,1. [source] Stability and optimum polymerized condition of polysiloxane,polyacrylate core/shell polymerADVANCES IN POLYMER TECHNOLOGY, Issue 3 2010Chengyue Ge Abstract The stable emulsion of core/shell latex with little coagulum (no more than 0.5% in quality relative to total monomers) has been prepared at low temperature with potassium-persulfate (KPS), sodium formaldehyde sulfoxylate (SFS), and 2,2,-azobis(2-(2-imidazolin-2-yl)propane)dihydrochloride (VA-044) as composite initiators by staged emulsion polymerization. Reactive surfactants were used to significantly improve the stability of emulsion. More interestingly, reverse core/shell structure was investigated when the organic silicon was added in the late period of polymerization. The effects of the emulsifier, initiators, dosage of organic silicon, and monomer's content on conversion and graft efficiency were studied in detail. Moreover, the stability of emulsion was investigated by the values of zeta potential (,) and coagulum. More importantly, the thermal performance and stability of PSI/PA composite latex was studied by the glass transition temperature (Tg). The results showed that there are appropriate values for all factors to obtain high conversion, graft efficiency, and excellent stability: The dosage of surfactant was about 0.44 g, the dosage of VA-044 was about 1000 mg kg,1, the dosage of organic silicon was about 15%, and the monomer's content was about 30%. In addition, the introduction of organic silicon improved the Tg. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:161,172, 2010; View this article online at wileyonlinelibrary. DOI 10.1002/adv.20182 [source] Preparation and properties of waterborne interpenetrating polymer networks composed of polyurethaneurea and graft vinyl ester resinJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2009Teng Su Abstract Various waterborne interpenetrating polymer networks (IPNs) composed of polyurethaneurea (PUU) and graft vinyl ester resin were prepared from polyester polyol, dimethylolpropionic acid, isophorone diisocyanate, ethylenediamine and a well-defined graft vinyl ester resin containing butanol side chains (BO-g-VER). These anionic IPN aqueous dispersions were stable at the ambient temperature for >1 yr, and also had the excellent stability at low and high temperatures. The experimental results showed that the introduction of BO-g-VER network has not only greatly affected the particle morphology, stability and rheological behavior of these aqueous dispersions, but also rendered the films with the augmented surface hydrophobicity as well as the excellent water-resistance performance and mechanical properties. A synergistic effect was observed at a certain BO-g-VER composition (20 wt %) to give significant reinforcement to the PUU, resulting from the compatibility and/or the interpenetration between the PUU network and the BO-g-VER network. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Effects of chemical structure on the properties of carboxylate-type copolymer dispersant for coal-water slurryAICHE JOURNAL, Issue 9 2009Renfu Xu Abstract In this study, a series of carboxylate-type copolymer dispersants were prepared. The effects of chemical structures of the copolymer dispersants, including the molecular weight, kind, quantity and ratio of hydrophilic/hydrophobic groups, and side chain length, on the solid loading, apparent viscosity, zeta potential, rheological behavior, and stability of coal-water slurry (CWS) prepared from Dongtan, Yima, and Datong coals were systematically investigated. The dispersion performance of the copolymer can be improved by adjusting its chemical structures, and the dispersion mechanism was discussed. In addition, a high solid loading CWS with excellent stability toward settling can be achieved by means of the copolymer dispersant and carboxymethyl cellulose sodium salt (CMC-Na). Experiments have proved that the copolymer has the potential to be developed as a new high-effective dispersant for CWS. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Novel thermally stable poly(amine hydrazide)s and poly(amine-1,3,4-oxadiazole)s for luminescent and electrochromic materialsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2005Guey-Sheng Liou Abstract We describe the preparation, characterization, and luminescence of four novel electrochromic aromatic poly(amine hydrazide)s containing main-chain triphenylamine units with or without a para-substituted N,N -diphenylamino group on the pendent phenyl ring. These polymers were prepared from either 4,4,-dicarboxy-4,- N,N -diphenylaminotriphenylamine or 4,4,-dicarboxytriphenylamine and the respective aromatic dihydrazide monomers via a direct phosphorylation polycondensation reaction. All the poly(amine hydrazide)s were amorphous and readily soluble in many common organic solvents and could be solution-cast into transparent and flexible films with good mechanical properties. These poly(amine hydrazide)s exhibited strong ultraviolet,visible absorption bands at 346,348 nm in N -methyl-2-pyrrolidone (NMP) solutions. Their photoluminescence spectra in NMP solutions or as cast films showed maximum bands around 508,544 and 448,487 nm in the green and blue region for the two series of polymers. The hole-transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. All obtained poly(amine hydrazide)s and poly(amine-1,3,4-oxadiazole)s exhibited two reversible oxidation redox couples at 0.8 and 1.24 V vs. Ag/AgCl in acetonitrile solution and revealed excellent stability of electrochromic characteristics, changing color from original pale yellow to green and then to blue at electrode potentials of 0.87 and 1.24 V, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3245,3256, 2005 [source] Novel family of triphenylamine-containing, hole-transporting, amorphous, aromatic polyamides with stable electrochromic propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2005Tzy-Hsiang Su Abstract We report the preparation and characterization of a series of novel electrochromic, aromatic poly(amine amide)s with pendent triphenylamine units. The synthesis proceeded via direct phosphorylation polycondensation between a novel diamine, N,N -bis(4-aminophenyl)- N,,N,-diphenyl-1,4-phenylenediamine, and various aromatic dicarboxylic acids. All the poly(amine amide)s were amorphous and readily soluble in many common organic solvents and could be solution-cast into transparent, tough, and flexible films with good mechanical properties. They exhibited good thermal stability and 10% weight-loss temperatures above 540 °C. Their glass-transition temperatures were 263,290 °C. These polymers in N -methyl-2-pyrrolidinone solutions exhibited strong ultraviolet,visible absorption peaks at 307,358 nm and photoluminescence peaks around 532,590 nm in the green region. The hole-transporting and electrochromic properties were studied with electrochemical and spectroelectrochemical methods. Cyclic voltammograms of poly(amine amide) films prepared by the casting of polymer solutions onto an indium tin oxide coated glass substrate exhibited two reversible oxidation redox couples at 0.65 and 1.03 V versus Ag/AgCl in an acetonitrile solution. All the poly(amine amide)s showed excellent stability with respect to their electrochromic characteristics; the color of the films changed from pale yellow to green and then blue at 0.85 and 1.25 V, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2085,2098, 2005 [source] Gold Nanoparticles Functionalized by a Dextran-Based pH- and Temperature-Sensitive PolymerMACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2010Weipeng Lv Abstract A dextran-based dual-sensitive polymer is employed to endow gold nanoparticles with stability and pH- and temperature-sensitivity. The dual-sensitive polymer is prepared by RAFT polymerization of N -isopropylacrylamide from trithiocarbonate groups linked to dextran and succinoylation of dextran after polymerization. The functionalized nanoparticles show excellent stability under various conditions and can be stored in powder-form. UV and DLS measurements confirm that the temperature-induced optical changes and aggregation behaviors of the particles are strongly dependent on pH. [source] Solvent Resistant Honeycomb Films from Photo-Crosslinkable PolycinnamateMACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2007Olaf Karthaus Abstract Microporous films consisting of two-dimensionally ordered void structures - so-called honeycomb films - were produced by evaporation of polymer solutions under high humidity. Two types of poly(vinyl cinnamate)s were used: A newly synthesized amphiphilic poly(vinyl cinnamate) and a mixture of a commercial poly(vinyl cinnamate) and an amphiphilic polyion complex. Photo-crosslinking of the honeycomb structure could be achieved by UV irradiation while completely retaining the film morphology. The crosslinked films showed excellent stability against organic solvents. [source] Interface properties and junction behavior of Pd contact on ZnO thin film grown by vacuum deposition techniquePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010Ghusoon M. Ali Abstract In this paper we explain the results of our experimental investigation on interface properties and junction behavior of Pd contact on ZnO thin film based Schottky diode. We used a conventional vacuum evaporation deposition unit for sequential deposition of ZnO film and metallic layer. For the first time a high quality Pd/ZnO Schottky diode is fabricated successfully in our laboratory by vacuum evaporation method. The I-V and C-V characteristics of the devices were studied by using microprobe arrangement. The parameter such as ideality factor, leakage current, resistance-area-product, carrier concentration and barrier height were extracted from the measured data. The surface morphological and the structural properties of thin film were studied by atomic force microscope. The optical band gap of thin film was determined using UV-visible spectrophotometer. The device fabricated by a simple technique exhibited excellent stability for use as an electronic or optoelectronic component. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Heck reaction catalyzed by a recyclable palladium supported on shell powderAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2010Yong-Miao Shen Abstract A novel palladium catalyst supported on shell powder has been prepared, and its application to the Heck reaction of aryl iodides with olefins has been reported. The results showed that the novel catalyst had extremely high activities for the reactions with the average yield over 90%. Also, this catalyst showed excellent stability in Heck reactions, being reused three times. The catalyst was characterized by X-ray powder diffraction and field-emission scanned electron microscopy images, and the energy dispersive X-ray analyzer. Copyright © 2010 John Wiley & Sons, Ltd. [source] Model-based characterization of an amino acid racemase from Pseudomonas putida DSM 3263 for application in medium-constrained continuous processesBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2007M. Bechtold Abstract The amino acid racemase with broad substrate specificity from Pseudomonas putida DSM 3263 was overproduced and characterized with respect to application in an integrated multi-step process (e.g., dynamic kinetic resolution) that,theoretically,would allow for 100% chemical yield and 100% enantiomeric excess. Overexpression of the racemase gene in Escherichia coli delivered cell free extract with easily sufficient activity (20,50 U,mg,1 total protein) for application in an enzyme membrane reactor (EMR) setting. Model-based experimental analysis of a set of enzyme assays clearly indicated that racemization of the model substrates D - or L -methionine could be accurately described by reversible Michaelis,Menten kinetics. The corresponding kinetic parameters were determined from progress curves for the entire suitable set of aqueous-organic mixtures (up to 60% methanol and 40% acetonitrile) that are eligible for an integrated process scheme. The resulting kinetic expression could be successfully applied to describe enzyme membrane reactor performance under a large variety of settings. Model-based calculations suggested that a methanol content of 10% and an acetonitrile content of 20% provide maximum productivity in EMR operations. However product concentrations were decreased in comparison to purely aqueous operation due to decreasing solubility of methionine with increasing organic solvent content. Finally, biocatalyst stability was investigated in different solvent compositions following a model-based approach. Buffer without organic content provided excellent stability at moderate temperatures (20,35°C) while addition of 20% acetonitrile or methanol drastically reduced the half-life of the racemase. Biotechnol. Bioeng. 2007; 98: 812,824. © 2007 Wiley Periodicals, Inc. [source] Dehydrohalogenation in Alpha-Functionalized Poly- p -xylylenes,CHEMICAL VAPOR DEPOSITION, Issue 4 2006P. Carrow Abstract Poly(p -xylylene) or parylene has been around for more than a half a century. It is typically deposited by the Gorham method from [2.2] paracyclophane. However, another method is via alpha-derivatives of p -xylene. Both poly(,-bromo- p -xylylene) and poly(,-chloro- p -xylylene) have been successfully deposited by this route through predominately HBr or HCl dehydrohalogenation gas-phase reactions. In the study reported here we synthesize ,,,,,-tribromo- p -xylene and ,-bromo-,,,,,-dichloro- p -xylene as CVD precursors to yield ,,,- and ,,,,-dihalogenated poly(p -xylylene)s to try to convert them, via post-deposition annealing, to poly(phenylene ethynylene) (PPE). PPE and its intermediate poly(phenylene vinylene) (PPV), have potentially better thermal and oxidative properties, and in addition they are both photoluminescent. The as-deposited and annealed thin films have been characterized by Rutherford backscattering spectrometry (RBS), infrared spectroscopy, and UV-vis spectrophotometry, and electrically tested by dielectric constant, bias-temperature stress (BTS), and leakage current. It is found that the thin films crystallizes concurrent with the formation of PPV and possibly converts to PPE but has much residual chlorine and bromine. However, PPV exhibits excellent stability in contact with copper and is more thermally stable than poly(p -xylylene). [source] | ||||||||||||||||||||||||||||