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131.
The electrophoretic behavior of a planar particle covered by an ion-penetrable membrane, which simulates a biological entity, is investigated. We show that, in general, a point charge model will overestimate the electrophoretic mobility of a particle and the deviation increases with the increase in the concentration of fixed charge and with the decrease in the thickness of membrane layer. As in the case of a point charge model, the present model also predicts a local maximum in the absolute mobility as the thickness of membrane layer varies. If the sizes of counterions of various valences are the same, then the lower the valence of counterions, the larger the mobility, and the larger the counterions, the greater the mobility. The latter is consistent with the experimental observations in the literature. For the level of the concentration of fixed charge examined, the effect of coions on the mobility is negligible. 相似文献
132.
The electrophoretic behavior of a sphere in a non-Newtonian fluid is investigated theoretically by analyzing the phenomenon that occurs in a spherical cavity under the condition of a weak applied electrical field. Non-Newtonian behavior in the liquid phase may be due to, for example, the addition of polymer to a colloidal dispersion to improve its stability. It may also arise from the increase in the volume fraction of the dispersed phase such as the slurry used in chemical mechanical polishing. A Carreau model is adopted to characterize the shear-thinning behavior of the liquid phase. We show that the difference between the mobility of the particle based on the present model and that based on the corresponding Newtonian fluid increases with the decrease in the thickness of a double layer. The shear-thinning nature of the liquid phase has the effect of increasing the mobility. 相似文献
133.
A mechanistic study of diacyl glycerophosphatidic acid (GPA) under low energy collisionally activated decomposition (CAD) with electrospray ionization tandem mass spectrometry is reported. The fragmentation pathways leading to the formation of carboxylate anions [RxCO2-], (x = 1, 2) and the formation of the ions representing neutral loss of fatty acid ([M-H-RxCO2H] ) and neutral loss of ketene ([M-H-R'xCH-C=O] ) (Rx=R'xCH2) are charge-driven processes that are governed by the gas-phase basicity and the steric configuration of the molecules. The preferential formation of the ions of [M-H-R2CO2H]- > [M-H-R1CO2H]- and [M-H-R'2CH=C=O]- > [M-H-R'1CH=C=O]- are attributed to the fact that loss of fatty acid and loss of ketene are sterically more favorable at sn-2. While the observation of the abundance of [M-H-RxCO2H]- > [M-H-R'xCH=C=O]- is attributed to the acidity of the gas phase ion of GPA, which undergoes a more facile neutral loss of acid than loss of ketene. The major pathway leading to the formation of RxCO2- ion under low energy CAD arises from further fragmentation of the [M-H-RxCO2H]- ions by neutral loss of 136, resulting in an abundance of R1CO2- > R2CO2-. The differential formation of the carboxylate anions permits accurate assignment of the regiospecificity of the fatty acid substituents of GPA molecules by tandem mass spectrometry. 相似文献
134.
The bulky teratiary phosphines P-t-Bu2Ph and P-t-Bu2-p-tol, provide binuclear ruthenium(I) complexes. An X-ray analysis of [Ru2Cl2(CO)4(P-t-Bu2-p-tol)2] shows the RuCl2Ru bridge to be non-planar and to have an Ru---Ru distance of 2.632Å. 相似文献
135.
Ion-exchanger phase Spectrophotometry withp-nitrochlorophosphonazo (CPApN) has been developed for the determination of scandium. The linear range is 1–8 g of scandium in 50 ml of solution, using 0.8 g of resin, with an apparent molar absorptivity of 2.76 × 105 1 mol–1 cm–1. Aluminum and rare earth elements in reasonable amounts do not interfere. The method has been applied successfully to the determination of scandium in alloys, with relative standard deviations of 2–4%. 相似文献
136.
采用二硫化碳重结晶富勒烯混合物或二硫化碳二次抽提烟灰以提取高富勒烯(higherfulerenes,Cn,n>70)。产物经高效液相色谱分析,高富勒烯的含量从1%分别提高到4%和6%;经激光飞行时间质谱证明,产物中除含主要成分C60和C70以外,还含有C76、C78、C82、C84以及更高碳原子的富勒烯。 相似文献
137.
138.
Zhang JJ Sheng TL Hu SM Xia SQ Leibeling G Meyer F Fu ZY Chen L Fu RB Wu XT 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(16):3963-3969
The first successful attempt to construct 3D supramolecular frameworks with high-nuclear 3d-4f heterometallic clusters as a node is reported. The self-assembly of Ln3+, Cu2+ and amino acid in solution leads to the formation of two polymers, 35-nuclear complex [Sm6Cu29] 1 with a primitive cubic net-like structure and 36-nuclear complex [Nd6Cu30] 2 with a face-centred cubic network type structure. Glycine and L-proline, respectively, were used as ligands. It should be noted that 2 has a chiral framework. X-ray structure analyses show that 1 crystallizes in the triclinic P1 space group (a=19.6451(8), b=20.4682(8), c=20.7046(8) A, alpha=89.453(1), beta=66.290(1), gamma=68.572(1) degrees, V=7003.0(5) A3 and Z=1) and 2 belongs to the cubic P2(1)3 space group (a=b=c=32.4341(3) A, V=34 119.7(5) A3 and Z=4). Both complexes utilize Ln6Cu24 octahedral clusters as nodes and trans-Cu(amino acid)2 groups as bridges. Electrical conductivity measurements reveal that both polymers behave as semiconductors. 相似文献
139.
Quarez E Hsu KF Pcionek R Frangis N Polychroniadis EK Kanatzidis MG 《Journal of the American Chemical Society》2005,127(25):9177-9190
The nature of the thermoelectric materials Ag(1-x)Pb(m)SbTe(m+2) or LAST-m materials (LAST for Lead Antimony Silver Tellurium) with different m values at the atomic as well as nanoscale was studied with powder/single-crystal X-ray diffraction, electron diffraction, and high-resolution transmission electron microscopy. Powder diffraction patterns of different members (m = 0, 6, 12, 18, infinity) are consistent with pure phases crystallizing in the NaCl-structure-type (Fmm) and the proposition that the LAST family behaved as solid solutions between the PbTe and AgSbTe2 compounds. However, electron diffraction and high resolution transmission electron microscopy studies suggest the LAST phases are inhomogeneous at the nanoscale with at least two coexisting sets of well-defined phases. The minority phase which is richer in Ag and Sb is on the nanosized length scale, and it is endotaxially embedded in the majority phase which is poorer in Ag and Sb. Moreover, within each nanodomain we observe extensive long range ordering of Ag, Pb, and Sb atoms. The long range ordering can be confirmed by single crystal X-ray diffraction studies. Indeed, data collections of five different single crystals were successfully refined in space groups of lower symmetry than Fmm including P4/mmm and Rm. The results reported here provide experimental evidence for a conceptual basis that could be employed when designing high performance thermoelectric materials and dispel the decades long belief that the systems (AgSbTe2)(1-x)(PbTe)x are solid solutions. 相似文献
140.
烟酸对酸性硫酸盐体系铜电沉积的影响 总被引:2,自引:0,他引:2
对溶液A: 0.8 mol•L-1硫酸铜,0.6 mol•L-1硫酸,5.0×10-5 mol•L-1氯离子,1.0×10-4 mol•L-1聚乙二醇的溶液,溶液B:在溶液A中加入2.0×10-2 mol•L-1烟酸,pH为0.5,运用循环伏安和计时安培法研究玻碳电极上铜的电沉积行为.结果表明,铜的电沉积过程经历了晶核形成过程,其电结晶按瞬时成核和三维生长方式进行.烟酸的加入对铜的电沉积具有阻化作用,但不改变铜的电结晶机理.沉积层的X射线衍射表明Cu为面心立方结构,在烟酸存在下沉积层出现(220)高择优取向,这可能是烟酸在Cu(220)晶面上发生强烈吸附作用的结果. 相似文献