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71.
本文继采用含硫配体(-SH,-SR)对高分子保护金属胶体的配位俘获之后,采用锚联在SiO_2表面的较含硫配体配位能力弱的P,N配体分别与聚乙烯吡咯烷酮(PVP)保护的胶体钯在室温下反应,在P/Pd大于3.5,N/Pd大于7时,可以实施对保护金属胶体的配位俘获,证实了配位俘获法是一种具有普遍意义的方法,经原子吸收光谱分析,溶液中残留的金属钯的量小于0.36 ppm(P/Pd=3.5)。经电子能谱证实,锚联膦胺配体与金属钯之间存在配位作用,这是实施保护胶体负载化的关键。透射电镜分析表明,在整个配位俘获的过程中,无论是在载体上或是在溶液中,胶体钯的颗粒大小与分布均保持不变。因此,配位俘获法是一种能控制多相催化剂中金属颗粒大小与分布的有效方法。由此合成的钯催化剂具有很高的催化活性,良好的选择性和稳定性,在对Cis,Cis-1,3-环辛二烯的选择性加氢中,其活性仅比均相的PVP-Pd胶体催化剂稍低,选择性达100%。在周转数达12,000次/个钯原子后,其催化活性仍保持不变,随着P/Pd比的增大,催化活性迅速下降。 相似文献
72.
Two new isostructural Zintl phases, EuInGe and SrInGe, are obtained from high-temperature reactions of the pure elements in welded Ta tubes. Both ternary phases crystallize in a new structure type in space group Pnma (No. 62), with a = 4.921(1) A, b = 3.9865(9) A, and c = 16.004(3) A for EuInGe; and a = 5.021(1) A, b = 4.0455(9) A, and c = 16.188(4) A for SrInGe. The crystal structures established by single-crystal X-ray diffraction feature zigzag chains of 3-bonded Ge atoms and puckered layers of 4-bonded In atoms. The two structural units are linked into an anionic network with channels composed of 5-membered and 7-membered rings. The channels are filled by the respective divalent cations. The chemical bonding of the anionic [InGe](2)(-) network, derived from a one-electron oxidative distortion of the alpha-ThSi(2) structure, is explained using extended-Hückel band structure calculations. Magnetic measurements indicate that EuInGe exhibits Curie-Weiss paramagnetic behavior above 35 K and antiferromagnetic behavior below 35 K. The calculated effective moment, mu(eff) = 8.11 mu(B), of EuInGe and the diamagnetic behavior of SrInGe are consistent with the oxidation states of Eu(II) and Sr(II), respectively. 相似文献
73.
A novel thin-layer amperometric detector (TLAD) based on chemically modified ring-disc electrode and its application for simultaneous measurements of nitric oxide (NO) and nitrite (NO2−) in rat brain were demonstrated in this work. The ring-disc electrode was simultaneously sensitive to nitric oxide (NO) and nitrite (NO2−) by modifying its inner disc with electropolymerized film of cobalt(II) tetraaminophthalocyanine (polyCoTAPc)/Nafion and its outer ring with poly(vinylpyridine) (PVP), respectively. The ring-disc electrode was used to constitute a novel TLAD in radial flow cell for simultaneous measurements of NO and NO2− in rat brain combined with techniques of high performance liquid chromatography (HPLC) and in vivo microdialysis. It was found that the basal concentration of NO in the caudate nucleus of rat brain is lower than 1.0×10−7 mol l−1, NO2− concentration is 5.0×10−7 mol l−1 and NO exists in brain maybe mainly in the form of its decomposed product. 相似文献
74.
SynthesisandCrystalStructureofTrigadoliniumBromoorthosilicate,Gd_3Br(SiO_4)_2MaoJiang-Gao;ZhuangHong-Hui;HuangJin-Shun(StateKe?.. 相似文献
75.
Mao Jia-Jun Chen Yu-De Zhang Gui-Rong Zhou Zu-Ming 《Journal of Radioanalytical and Nuclear Chemistry》1986,100(1):103-115
A study on the synergistic extraction of uranium(VI) from nitric acid media with double-chelating agent systems 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (PMBP) plus thenoyltrifluoroacetone (TTA), and 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 plus 1-phenyl-3-methyl-4-trifluoroacetyl-pyrazolone-5 (PMTFP) is described. Some synergistic effects have been observed. The experimental results suggest that the composition of synergistic complex species is UO2PMBP·TTA and UO2PMBP·PMTFP, respectively. The equilibrium constants for these synergistic extractions are calculated by three methods and the mechanism and the regularity of extraction are discussed as well. 相似文献
76.
A Novel Dimeric Coumarin from Clausena lenis 总被引:1,自引:0,他引:1
HongPingHE ShunTingCHEN YueMaoSHEN ChangXiangCHEN YiBinZHAO XiaoJiangHAO 《中国化学快报》2003,14(11):1150-1153
A novel dimeric coumarin (1), a dimeric of seselin named diseselin A, was isolated from the aerial part of Clausena lenis. The structure was elucidated based on the MS, 1D and 2D NMR data. 相似文献
77.
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79.
Laser ablation in analytical chemistry-a review 总被引:4,自引:0,他引:4
Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas. 相似文献
80.
Yu P Lin Y Xiang L Su L Zhang J Mao L 《Langmuir : the ACS journal of surfaces and colloids》2005,21(20):9000-9006
This letter describes the formation and possible electrochemical applications of molecular films of water-miscible imidazolium-based ionic liquids (ILs) on glassy carbon (GC) electrodes. X-ray photoelectron spectroscopy (XPS) and electrochemical results indicate that the water-miscible ILs used in this study can interact with the GC electrode and form molecular films on the electrode surface. The formed molecular films are found to possess striking electrochemical properties such as electrocatalysis toward ascorbic acid (AA) and the capability to facilitate direct electron transfer of horseradish peroxidase (HRP). This demonstration would pave the way for new electrochemical applications of water-miscible ILs and is envisaged to be useful for the investigation of the electrochemical properties of water-miscible ILs in aqueous media provided the same counteranion is used as the supporting electrolyte. 相似文献