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Extended X-ray absorption fine structure

About: Extended X-ray absorption fine structure is a research topic. Over the lifetime, 10452 publications have been published within this topic receiving 276744 citations.


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Journal ArticleDOI
TL;DR: The physical interpretation of results concerning the amorphous materials and their evolution under thermal treatment gives conclusive evidence that local, intraparticle ordering variations determine the temperature for the onset of the nucleation process and drive the solid behavior through the whole crystallization process.
Abstract: Nanoparticulated TiO2 materials with anatase structure were synthesized by using a microemulsion method. The structural characteristics of the amorphous solid precursors and their evolution during thermal treatments were studied by using X-ray absorption structure (X-ray absorption near edge structure XANES and extended X-ray absorption fine structure EXAFS), XRD-PDF (X-ray diffraction-pair distribution function), and infrared spectroscopy. Concerning the precursor materials, XANES and EXAFS showed a local order closely related to that of the anatase structure but containing defective, undercoordinated Ti5c4+ species in addition to normal Ti6c4+ species. The PDF technique detects differences among samples in the local order (below 1 nm) and showed that primary particle size varies throughout the amorphous precursor series. The physical interpretation of results concerning the amorphous materials and their evolution under thermal treatment gives conclusive evidence that local, intraparticle ordering variations determine the temperature for the onset of the nucleation process and drive the solid behavior through the whole crystallization process. The significance of this result in the context of current crystallization theories of oxide-based nanocrystalline solids is discussed.

84 citations

Journal ArticleDOI
TL;DR: The first coordination sphere of the uranyl cation in room-temperature ionic liquids (ILs) results from the competition between its initially bound counterions, the IL anions, and other anions (e.g., present as impurities or added to the solution).
Abstract: The first coordination sphere of the uranyl cation in room-temperature ionic liquids (ILs) results from the competition between its initially bound counterions, the IL anions, and other anions (e.g., present as impurities or added to the solution). We present a joined spectroscopic (UV−visible and extended X-ray absorption fine structure)-simulation study of the coordination of uranyl initially introduced either as UO2X2 salts (X- = nitrate NO3-, triflate TfO-, perchlorate ClO4-) or as UO2(SO4) in a series of imidazolium-based ILs (C4mimA, A- = PF6-, Tf2N-, BF4- and C4mim = 1-methyl-3-butyl-imidazolium) as well as in the Me3NBuTf2N IL. The solubility and dissociation of the uranyl salts are found to depend on the nature of X- and A-. The addition of Cl- anions promotes the solubilization of the nitrate and triflate salts in the C4mimPF6 and the C4mimBF4 ILs via the formation of chloro complexes, also formed with other salts. The first coordination sphere of uranyl is further investigated by molecular dyna...

84 citations

Journal ArticleDOI
TL;DR: A sharp optical absorption edge has been found at about 0.5 eV for amorphous Ge on a quartz substrate as discussed by the authors, which is comparable in sharpness with the direct edge of crystalline Ge.
Abstract: A sharp optical absorption edge has been found at about 0.5 eV for amorphous Ge on a quartz substrate. The edge is comparable in sharpness with the direct edge of crystalline Ge. No evidence for tailing of the band edges into the forbidden band or for a high density of states in the forbidden band is found by these optical measurements. A new density determination gives a value of 4.54\ifmmode\pm\else\textpm\fi{} 0.14 g/${\mathrm{cm}}^{3}$.

84 citations

Journal ArticleDOI
TL;DR: These results place the various Cp2*Yb(bipy) complexes in a new tautomeric class, that is, intermediate-valence tautomers, and are supported by CASSCF-MP2 calculations.
Abstract: Multiconfigurational, intermediate valent ground states are established in several methyl-substituted bipyridine complexes of bis(pentamethylcyclopentadienyl)ytterbium, Cp2*Yb (Mex-bipy). In contrast to Cp2*Yb(bipy) and other substituted-bipy complexes, the nature of both the ground state and the first excited state are altered by changing the position of the methyl or dimethyl substitutions on the bipyridine rings. In particular, certain substitutions result in multiconfigurational, intermediate valent open-shell singlet states in both the ground state and the first excited state. These conclusions are reached after consideration of single-crystal X-ray diffraction (XRD), the temperature dependence of X-ray absorption near-edge structure (XANES), extended X-ray absorption fine-structure (EXAFS), and magnetic susceptibility data, and are supported by CASSCF-MP2 calculations. These results place the various Cp2*Yb(bipy) complexes in a new tautomeric class, that is, intermediate-valence tautomers.

84 citations

Journal ArticleDOI
24 Nov 2010
TL;DR: Formation of nitrogen vacancies under low-energy ion bombardment reduces oxidation resistance of BN structures and promotes an efficient oxygen-healing mechanism, in full agreement with some recent theoretical predictions.
Abstract: Decoration of nitrogen vacancies by oxygen atoms has been studied by near-edge x-ray absorption fine structure (NEXAFS) in several boron nitride (BN) structures, including bamboo-like and multi-walled BN nanotubes. Formation of nitrogen vacancies under low-energy ion bombardment reduces oxidation resistance of BN structures and promotes an efficient oxygen-healing mechanism, in full agreement with some recent theoretical predictions.

84 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023110
2022264
2021156
2020164
2019164
2018151