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891.
We present a simple method of obtaining electrically conducting electrospun silk non-woven membranes consisting of nanofibers
with multi-walled carbon nanotubes (MWCNTs) adsorbed on their surface. Nanofibrous membranes with fibroin diameters of 460 ± 40 nm
were formed from aqueous Bombyx mori fibroin solution by electrospinning. The MWCNTs adhered well to the surface of the highly porous silk nanofibrous membranes
when Triton X-100 was used as the surfactant for the dispersion of the MWCNTs in aqueous media. The electrical conductivity
of the membranes was 2.4 × 10−4 S/cm due to the presence of the MWCNTs on their surface. In addition, the strong interaction between the MWCNTs and nanofibers
keeps them from separating each other, even after ultrasonication. The combination of the high conductivity of the membranes
and the simple process used to fabricate them could lead to significant advances in the development of new materials, such
as electromagnetic interference shielding or electrostatic dissipation membranes. 相似文献
892.
The introduction of mesoporous nanosize zirconia to the catalyst for methanol synthesis dedicates the nanosized catalyst and mesoporous duplicated properties. The catalyst bears the larger surface area, larger mesoporous volume and more uniform diameter, more surface metal atoms and oxygen vacancies than the catalyst prepared with the conventional coprecipitation method. The modification of microstructure and electronic effect could result in the change of the reduced chemical state and decrease of reducuction temperature of copper, donating the higher activity and methanol selectivity to the catalyst. The results of methanol synthesis demonstrate that the Cu^+ is the optimum active site. Also, the interaction between the copper and zirconia shows the synergistic effect to fulfil the methanol synthesis. 相似文献
893.
The history and present state of the art in the chemistry of mesophase pitch, which is an important precursor for carbon fiber and other high-performance industrial carbons, are reviewed relative to their structural properties. The structural concepts in both microscopic and macroscopic views are summarized in terms of the sp(2) carbon hexagonal plane as a basic unit common to graphitic materials, its planar stacking in clusters, and cluster assembly into microdomains and domains, the latter of which reflect the isochromatic unit of optical anisotropy. Such a series of structural units is described in a semiquantitative manner corresponding to the same units of graphitic materials, although the size and stacking height of the hexagonal planes (graphitic sheets) are very different. Mesophase pitch is a liquid crystal material whose basic structural concepts are maintained in the temperature range of 250 to 350 degrees C. The melt flow and thermal properties are related to its micro- and mesoscopic structure. The structure of mesophase-pitch-based carbon fiber of high tensile strength, modulus, and thermal conductivity has been formed through spinning, and has inherited the same structural concepts of mesophase pitch. Stabilization settles the structure in successive heat treatments up to 3000 degrees C. Carbonization and graphitization enable growth of the hexagonal planes and their stacking into units of graphite. Such growth is governed and controlled by the alignment of micro- and mesoscopic structures in the mesophase pitch, which define the derived carbon materials as nanostructural materials. Their properties are controlled by the nanoscopic units that are expected to behave as nanomaterials when appropriately isolated or handled. 相似文献
894.
Sung Woo Moon Gun-Dae Lee Seong Soo Park Seong-Soo Hong 《Reaction Kinetics and Catalysis Letters》2004,82(2):303-310
Catalytic combustion of chlorobenzene over supported vanadium oxides has been investigated. TiO2 was prepared by the sol-gel method from titanium isopropoxide. The supported vanadium oxide catalysts have been prepared
by precipitation-deposition and impregnation method and characterized by XRD, FT-Raman and TPR. In the VOx/TiO2catalysts prepared using the impregnation method, when vanadium loading reaches 3 wt.%, the activity shows a maximum. However,
in the VOx/TiO2catalysts prepared by precipitation-deposition, when vanadium loading reaches 7 wt.%, the activity shows a maximum. This result
suggests that the precipitation-deposition can yield a higher metal loading on the support and a high dispersion compared
to the impregnation method.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
895.
The kinetics of electroreduction of Pd(II) complexes with -alanine, Pd(ala)2, is studied on a rotating Pd disk electrode in solutions of pH 8–13 containing large excess of -alanine and various supporting electrolytes (NaF, Na2SO4, NaClO4). On a Pd electrode, complexes Pd(ala)2 undergo reduction at potentials much more negative than on an Hg electrode. This is attributed to the chemisorption of water on the Pd electrode, which hampers adsorption of Pd(ala)2 that take part in the slow electrochemical stage. As with the Hg electrode, perchlorate ions hinder the Pd(ala)2 reduction on a Pd electrode. Studying adsorption of Pd(ala)2 on a Pd electrode is hampered by parallel processes of hydrogen adsorption and absorption. 相似文献
896.
一代树状碳硅烷液晶的光化学研究--端基含12个4-丁氧基氮苯介晶基元 总被引:2,自引:0,他引:2
研究了新的含12个丁氧基偶氮苯介晶基元的五代树状碳硅烷液晶D1及偶氮苯介 晶基元化合物M5在氯仿、四氢呋喃、N,N-二甲基甲酰胺、乙醇和苯等溶剂中的量 子产率、反-顺光异构化、光回复异构、反/顺异构组分比、热回复异构及活化能 。D1和M5的光致变色速率常数为10~(-1)s~(-1),而含同一偶氮基元的光致变色液 晶聚硅氧烷的光致变色速率常数为10~(-8)s~(-1),因此,液晶树状物D1的光响应 速度比后者快10~7倍。 相似文献
897.
Imide-siloxane block copolymer/silica hybrid membranes: preparation, characterization and gas separation properties 总被引:1,自引:0,他引:1
Ho Bum Park Jang Ki Kim Sang Yong Nam Young Moo Lee 《Journal of membrane science》2003,220(1-2):59-73
Imide-siloxane block copolymer/silica hybrid membranes with covalent bonds were prepared via sol–gel reaction. The structural informations of these hybrid membranes were obtained by using Fourier transform-infrared spectrometry (FT-IR), 29Si nuclear magnetic resonance (29Si NMR), XPS and thermogravimetric analysis (TGA). The gas separation properties of the hybrid membranes were also investigated in terms of organosiloxane (PDMS) or silica content at various temperatures. In the hybrids, the addition of PDMS phase increased the permeabilities of gases such as He, CO2, O2, and N2, indicating that the gas transport occurred mainly through rubbery organic matrix. Meanwhile, the PDMS phase contributed the decreased gas selectivities to nitrogen but the reduction in selectivities was very small in comparison with other siloxane containing polymeric membranes. This might be due to the restriction of chain mobility by the existence of inorganic component such as silica network in the hybrids. Additionally, the increase of silica content in these hybrid membranes considerably retarded the falling-off of gas selectivity at elevated temperature. The increase of silica content in hybrid membranes resulted in well-formed silica networks and hence these inorganic components restricted the plasticization of organic matrix by the thermal segmental motion of organic components, leading to preventing the large decrease of the gas selectivity. 相似文献
898.
899.
Quantitative analysis of docetaxel in human plasma using liquid chromatography coupled with tandem mass spectrometry 总被引:2,自引:0,他引:2
Kuppens IE van Maanen MJ Rosing H Schellens JH Beijnen JH 《Biomedical chromatography : BMC》2005,19(5):355-361
An assay for the quantitative determination of docetaxel in human plasma is described. Docetaxel was extracted from the matrix using liquid-liquid extraction with ter-butylmethylether, followed by high-performance liquid chromatographic analysis using an alkaline eluent. Paclitaxel was used as internal standard. Positive ionization electrospray tandem mass spectrometry was performed for selective and sensitive detection. The method was validated according to the FDA guidelines on bioanalytical method validation. The validated range for docetaxel was from 0.25--1000 ng/mL using 200 microL plasma aliquots. The method requires only a limited volume (200 microL) of human plasma and the method can be applied in studies requiring a low lower limit of quantitation of 0.25 ng/mL. The assay was applied successfully in several clinical and pharmacological studies with docetaxel. 相似文献
900.
Carboxylate-benzyl and nitro-benzyl groups used in phenols protection were selectively debenzylated with 3-25 equiv of Mg in methanol at room temperature. Good yields of the desired phenols were obtained within 3-10 h from a wide variety of O-(carboxylate-benzyl)- or O-(nitro-benzyl)-phenols. Selective O-debenzylation was possible in the presence of O-(carboxylate-benzyl)- or O-(nitro-benzyl)-phenols with Mg/MeOH. 相似文献