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31.
Iulian Preda Leonardo Soriano Daniel Díaz‐Fernández Guillermo Domínguez‐Cañizares Alejandro Gutiérrez Germán R. Castro Jesús Chaboy 《Journal of synchrotron radiation》2013,20(4):635-640
This work reports an X‐ray absorption near‐edge structure (XANES) spectroscopy study at the Ni K‐edge in the early stages of growth of NiO on non‐ordered SiO2, Al2O3 and MgO thin films substrates. Two different coverages of NiO on the substrates have been studied. The analysis of the XANES region shows that for high coverages (80 Eq‐ML) the spectra are similar to that of bulk NiO, being identical for all substrates. In contrast, for low coverages (1 Eq‐ML) the spectra differ from that of large coverages indicating that the local order around Ni is limited to the first two coordination shells. In addition, the results also suggest the formation of cross‐linking bonds Ni—O—M (M = Si, Al, Mg) at the interface. 相似文献
32.
Toshihiro Yoshimura Yusuke Tamenori Nozomu Iwasaki Hiroshi Hasegawa Atsushi Suzuki Hodaka Kawahata 《Journal of synchrotron radiation》2013,20(5):734-740
Magnesium K‐edge X‐ray absorption near‐edge structure (XANES) spectra have been investigated to develop a systematic understanding of a suite of Mg‐bearing geological materials such as silicate and carbonate minerals, sediments, rocks and chemical reagents. For the model compounds the Mg XANES was found to vary widely between compounds and to provide a fingerprint for the form of Mg involved in geologic materials. The energy positions and resonance features obtained from these spectra can be used to specify the dominant molecular host site of Mg, thus shedding light on Mg partitioning and isotope fractionation in geologic materials and providing a valuable complement to existing knowledge of Mg geochemistry. 相似文献
33.
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
34.
Silvia H. Santagneli Matthias T. Rinke Younes Messaddeq Hellmut Eckert 《Journal of Non》2011,357(10):2126-2131
Glasses were prepared in the pseudo-binary system (1 − x)AgPO3-xWO3 (0≤ × ≤ 0.6 mol%). The structural evolution of the vitreous network was studied as a function of composition by thermal analysis, Fourier Transform Infrared spectroscopy (FTIR), Raman scattering, high resolution 31P solid state NMR and XANES at the W-L1 absorption edge. For compositions with x ranging from 0 to 0.5 a pronounced increase in the glass transition temperature is observed, suggesting a significant increase in the glass network connectivity. At the same time Raman spectra indicate that tungsten atoms are linked to non-bridging oxygen atoms (W-O- or W=O bonded species) whereas the 31P MAS-NMR spectra indicate the successive formation of new P-O-W linkages. The formation of some anionic tungsten sites (if these are revealed by the presence of W-O terminal bonds) implies an increase in the average degree of polymerization of the phosphate network, which is consistent with the compositional evolution of the 31P MAS-NMR spectra at low x values. For higher x-values, the Raman spectra indicate the presence of W-O-W linkages. W-L1 XANES data indicate that at least 90% of tungsten atoms are octahedrally coordinated. 相似文献
35.
M.T. Klepka K. Lawniczak-Jablonska M. Jablonski 《Journal of Electron Spectroscopy and Related Phenomena》2010,182(3):85-89
Natural ilmenites are used all over the world as raw materials in white pigment (TiO2) production. Besides the FeTiO3 in the raw material many other compounds are present. The chemical compounds based on the minority elements influence quality of the final product and are difficult to identify. The knowledge about chemical bonding of the minor elements enables to properly adjust chemical reactions during production processes and to improve quality of the final product. In this paper the X-ray absorption spectroscopy (XAS) identification of the chemical compounds formed by Mg, Mn and Cr in natural ilmenites originating from different places is presented. 相似文献
36.
Hiroshi Negishi Saiko Negishi Minoru Sasaki Masasi Inoue Shigeo Ohara 《Molecular Crystals and Liquid Crystals》2013,570(2):63-68
Abstract EXAFS and XANES spectra of Ti K-edge have been measured for 3d transition metal intercalation compounds M x TiS2 (M = Mn, Fe, Co and Ni; x ≤ 0.33). We have found that the interatomic distance between Ti and the first nearest neighbor S atoms, R(Ti-S), increases with the guest concentration x. The variation in XANES spectra with x reveals the reduction of the valence state of Ti atoms upon intercalation of M. From these results as well as the M K-edge EXAFS data studied previously, we have proposed a simple model on the local structure of M x TiS2 to reproduce the observed values of R(Ti-S) by averaging local shift of S atoms caused by intercalation. 相似文献
37.
Abstract We have investigated Cu, Zn Superoxide Dismutase (Cu, Zn SOD) metal sites at high pressure using X-ray absorption. XAS (X-ray Absorption Spectroscopy) gives information on local structure and it is particularly suited to metal site investigation. To the best of our knowledge, this is the first time that protein conformational states have been investigated using the high pressure XAS technique. Cu, Zn SOD catalyses the dismutation of toxic oxygen radicals produced in cells; this reaction occurs at the copper metal site. Structural changes around the copper, induced by pressure, can be directly related to protein substates. Their characterisation is thus important in the understanding of protein activity. The high-pressure device was a Paris-Edinburgh large volume cell. Experiments were performed on lyophilised Cu, Zn SOD between 0 and 48 kbar at the copper and zinc K-edges. The two metal local atomic environments have a different behaviour as pressure increases: copper exhibits a more flexible environment; on the contrary, zinc shows small structural modifications. We have identified a state, formed between 3 and 8 kbar, which is stable up to 48 kbar. 相似文献
38.
39.
Shogo Morisako Seiya Watanabe Satoru Ikemoto Satoshi Muratsugu Mizuki Tada Makoto Yamashita 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(42):15173-15177
A pincer‐iridium complex bearing a Lewis‐base‐free X‐type alumanyl ligand has been synthesized. X‐ray diffraction, NMR and IR spectroscopy, as well as XANES analysis confirmed its tetrahydrido‐IrV structure and Lewis acidity at the Al center as supported by DFT calculations. The resulting complex was applied as a catalyst for the transfer dehydrogenation of cyclooctane. 相似文献
40.
Ali M. Abdel‐Mageed Alexander Klyushin Azita Rezvani Axel Knop‐Gericke Robert Schlgl R. Jürgen Behm 《Angewandte Chemie (International ed. in English)》2019,58(30):10325-10329
The electronic and structural properties of Au/ZnO under industrial and idealized methanol synthesis conditions have been investigated. This was achieved by kinetic measurements in combination with time‐resolved operando infrared (DRIFTS) as well as in situ near‐ambient pressure X‐ray photoelectron spectroscopy (NAP‐XPS) and X‐ray absorption near‐edge spectroscopy (XANES) measurements at the O K‐edge together with high‐resolution electron microscopy. The adsorption of CO during the reaction revealed the presence of negatively charged Au nanoparticles/Au sites during the initial phase of the reaction. Near‐ambient‐pressure XPS and XANES demonstrate the build‐up of O vacancies during the reaction, which goes along with a substantial increase in the rate of methanol formation. The results are discussed in comparison with previous findings for Cu/ZnO and Au/ZnO catalysts. 相似文献