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51.
E. D. Ion B. Malič I. Arčon A. Kodre M. Kosec 《Journal of Sol-Gel Science and Technology》2008,45(2):213-218
PbZrO3 powders have been prepared by an alkoxide-based sol–gel route, starting from lead acetate, zirconium n-butoxide, and n-butanol as a solvent, and hydrolysed with different amounts of water in neutral and alkaline medium. The local environment
of Zr and Pb atoms was pursued from the sol to the dried (150 °C) and heated (400 °C) powders, by extended x-ray absorption
fine structure (EXAFS). The analysis of the sol revealed links between Pb and Zr, and even more links between Zr and Zr. The
metal neighbourhoods in the dried powders are not influenced by the hydrolysis conditions. Pb-Zr correlations are gradually
lost from the sol to the dried and heated powders, while the loss of Zr–Zr correlations is considerably lower. 相似文献
52.
Linjuan Zhang Jing Zhou Jianyong Zhang Jing Su Shuo Zhang Ning Chen Yunpeng Jia Jiong Li Yu Wang Jian-Qiang Wang 《Journal of synchrotron radiation》2016,23(3):758-768
Obtaining structural information of uranyl species at an atomic/molecular scale is a critical step to control and predict their physical and chemical properties. To obtain such information, experimental and theoretical L3‐edge X‐ray absorption near‐edge structure (XANES) spectra of uranium were studied systematically for uranyl complexes. It was demonstrated that the bond lengths (R) in the uranyl species and relative energy positions (ΔE) of the XANES were determined as follows: ΔE1 = 168.3/R(U—Oax)2 ? 38.5 (for the axial plane) and ΔE2 = 428.4/R(U—Oeq)2 ? 37.1 (for the equatorial plane). These formulae could be used to directly extract the distances between the uranium absorber and oxygen ligand atoms in the axial and equatorial planes of uranyl ions based on the U L3‐edge XANES experimental data. In addition, the relative weights were estimated for each configuration derived from the water molecule and nitrate ligand based on the obtained average equatorial coordination bond lengths in a series of uranyl nitrate complexes with progressively varied nitrate concentrations. Results obtained from XANES analysis were identical to that from extended X‐ray absorption fine‐structure (EXAFS) analysis. XANES analysis is applicable to ubiquitous uranyl–ligand complexes, such as the uranyl–carbonate complex. Most importantly, the XANES research method could be extended to low‐concentration uranyl systems, as indicated by the results of the uranyl–amidoximate complex (~40 p.p.m. uranium). Quantitative XANES analysis, a reliable and straightforward method, provides a simplified approach applied to the structural chemistry of actinides. 相似文献
53.
In this study, facile preparation of pure and nano-sized cobalt oxides particles was achieved using low-cost mechanical ball-milling synthesis route. Microstructural and morphological properties of synthesised products were characterised by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. XRD results indicated that the fabricated samples composed of cubic pure phase CoO and Co3O4 nanocrystalline particles with an average crystallite size of 37.2 and 31.8 nm, respectively. TEM images showed that the resulting samples consisted of agglomerates of particles with average diameter of about 37.6 nm for CoO and 31.9 nm for Co3O4. Phase purity of the prepared samples was further investigated due to their promising technological applications. Local atomic structure properties of the prepared nanoparticles were probed using synchrotron radiation-based X-ray absorption spectroscopy (XAS) including X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). EXAFS data analysis further confirmed the formation of single-phase CoO and Co3O4 nanoparticles. In addition, structural properties of cobalt oxide nanoparticles were investigated by performing density functional theory calculations at B3LYP/TZVP level and Born–Oppenheimer molecular dynamics. Theoretical calculations for both prepared samples were found to be consistent with the experimental results derived from EXAFS analysis. Obtained results herein reveals that highly crystalline and pure phase CoO and Co3O4 nanoparticles can be synthesised using simple, inexpensive and eco-friendly ball-milling method for renewable energy applications involving fuel cells and water splitting devices. 相似文献
54.
本文利用EXAFS(Extended X-ray Absorption Fine Structure)对铑基担载液相催化剂(Supported Liquid Phase Catalyst SLPC)进行了结构表征。采用球面波理论对SLPC的EXAFS结果进行了多参数拟合。结果表明,在新鲜催化剂上,铑络合物以二聚物形式存在,推测其结构为(PPh_3)_2(CO)Rh-Rah(CO)(PPh_3)_2,Rh-C-O偏离共线分布。在经过羰化反应活化的活性SLPC上,铑络合物为单核的HRh(CO)_2(PPh_3)或Rh(CO)_2(PPh_32)_3。文中还讨论了SLPC的XRD谱。 相似文献
55.
Kotaro Ishiji Tomoyuki Matsuda Hiroko Tokoro Toshiaki Iwazumi Shin-ichi Ohkoshi 《Journal of Physics and Chemistry of Solids》2007,68(11):2158-2161
Cesium manganese hexacyanoferrates exhibit an interesting phenomenon of temperature-induced phase transition accompanied by a variation in the magnetic susceptibility. We observed the variation in the electronic state of Mn during the phase transition by using X-ray absorption spectroscopy. The results of the analyses showed that the content ratio of FeII-CN-MnIII and FeIII-CN-MnII systematically varied during the phase transition. However, the ratio of FeII-CN-MnII remained constant at almost all temperatures. These results suggest that the charge transfer between Fe and Mn ions in the FeIII-CN-MnII or the FeII-CN-MnIII bond produces the phase transition. 相似文献
56.
S K Deshpande S M Chaudhari Ashok Pimpale A S Nigavekar S B Ogale V G Bhide 《Pramana》1991,37(4):373-385
An automated linear laboratory EXAFS spectrometer of the Johansson type has been indigenously developed. Only two translational
motions are required to achieve the necessary Rowland circle configuration for the (fixed) X-ray source, the dispersing and
focusing bent crystal and the receiving slit. With the available crystals the spectral region from 5 to 25 keV can be scanned.
The linear motions of the crystal and receiving slit including the detector assembly are achieved by employing software-controlled
DC motors and utilizing optical encoders for position sensing. The appropriate rotation of the crystal is achieved by the
geometry of the instrument. There is a facility to place the sample alternately in the path of the X-ray beam and out of the
path to record both the incident X-ray intensityI
0 and the transmitted intensityI employing the scintillation detector. An arrangement with a two-window proportional detector before the sample to measureI
0 and the scintillation detector to recordI is also developed; in this case it is not necessary to oscillate the sample. Fast electronic circuits are employed to minimize
counting errors. The instrument is user-friendly and it is operated through a menu-driven IBM compatible PC. EXAFS spectra
of high resolution have been recorded using the spectrometer and employing the Si(111) reflecting planes; the X-ray source
being a Rigaku 12 kW rotating anode with Cu target. We describe the spectrometer and discuss its performance with a few representative
spectra. 相似文献
57.
A metal-support interaction between Pd and various kinds of zeolite and metal oxide supports was studied, which were active in the catalytic combustion and selective reduction of NO. The acid-base properties of supports affected the oxidation state, structure and catalytic activity of Pd. The acid sites of zeolite played the role to anchor the dispersed PdO as evidenced by the dynamic structural change of Pd. It was found that the metal-support interaction is an important factor, affecting the oxidation state, structure and catalytic performance of Pd. 相似文献
58.
In the back-end of the nuclear fuel cycle, liquid–liquid extraction is the selected separation method. For an improved design of new extracting agent, the knowledge of the coordination polyhedra of the metal ions is important. In this paper, we investigated the coordination sphere of a series of uranyl complexes with selected organophosphorus extracting molecules: UO2(NO3)2L2 (with L=tri-iso-butylphosphate, tri-n-butylphosphate, trimethylphosphate and triphenylphosphate) using X-ray absorption spectroscopy. FEFF7 calculations of the EXAFS spectra corresponding to the model compound UO2(NO3)2(TiBP)2 (with TiBP=tri-iso-butylphosphate) for which the crystal structure is known led to a multiple scattering approach of the data fitting. EXAFS results show subtle U–O(P) bond distance differences between the different complexes that are discussed in terms of both electronic and steric effects of L. These results are discussed with regards to the extraction ability of L. In the same time, exploratory work has been attempted in order to evaluate U–O–P bond angle variations as a function of L using multiple photon-scattering paths. Satisfactory values have been obtained compared to the crystallographic data. 相似文献
59.
60.
Walther C Rothe J Fuss M Büchner S Koltsov S Bergmann T 《Analytical and bioanalytical chemistry》2007,388(2):409-431
Polynuclear species of zirconium in acidic aqueous solution are investigated by combining X-ray absorption spectroscopy (XAFS)
and nanoelectrospray mass spectrometry (ESI-MS). Species distributions are measured between pHC 0 and pHC 3 for [Zr] = 1.5–10 mM. While the monomer remains a minor species, with increasing pH the degree of polymerization increases
and the formation of tetramers, pentamers, octamers, and larger polymers is observed. The high resolution of the mass spectrometer
permits the unambiguous determination of polynuclear zirconium hydroxide complexes by means of their isotopic patterns. The
relative abundances of mononuclear and polynuclear species present simultaneously in solution are measured, even if one of
the species contributes only 0.1% of the Zr concentration. For the first time it has been directly observed that the hydrolysis
of polynuclear Zr species is a continuous process which leads to charge compensation through the sequential substitution of
water molecules by hydroxide ligands until doubly charged polymers dominate at conditions (H+ and Zr concentrations) close to the solubility of Zr(OH)4(am). The invasiveness of the electrospray process was minimized by using very mild declustering conditions, leaving the polynuclear
species within a solvent shell of approximately 20 water molecules.
Figure Schematic Diagram of Multiplexed Measurement of 9 Anti-Nuclear Antibodies Using the AtheNa Multilyte Assay 相似文献