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XANES

About: XANES is a research topic. Over the lifetime, 7737 publications have been published within this topic receiving 188032 citations.


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Journal ArticleDOI
TL;DR: In this paper, the synthesis of Fe-doped ZnO with nominal composition of Zn0.99Fe0.01O by using a coprecipitation method was reported.
Abstract: We report on the synthesis of Fe-doped ZnO with nominal composition of Zn0.99Fe0.01O by using a coprecipitation method. X-ray diffraction and selective area electron diffraction studies reveal a single phase wurtzite crystal structure without any secondary phase. Field emission transmission electron microscopy measurements infer that Zn0.99Fe0.01O have nanorod-type microstructures. Magnetic hysteresis measurement performed at different temperatures show that Zn0.99Fe0.01O exhibits a weak ferromagnetic behavior at room temperature. A detailed investigation of the electronic and local structure using O K-, Fe L3,2 near edge x-ray absorption fine structure suggests that Fe is substituting Zn in ZnO matrix and is in Fe3+ state.

63 citations

Journal ArticleDOI
TL;DR: In this paper, the mechanism of catalytic oxidation reactions was studied using in situ X-ray absorption spectroscopy (XAFS) over a 17.5 wt% V2O5/Al2O3 catalyst at reaction temperatures and in the presence of reactants.
Abstract: The mechanism of catalytic oxidation reactions was studied using in situ X-ray absorption spectroscopy (XAFS) over a 17.5 wt% V2O5/Al2O3 catalyst, i.e., at reaction temperatures and in the presence of reactants. It was found that X-ray absorption near-edge structure (XANES) is a powerful tool to study changes in the local environment and the oxidation state of the vanadium centres during catalytic oxidation. At 623 K, the catalyst follows the associative mechanism in CO oxidation. XAFS revealed that the Mars–van Krevelen mechanism is operative at 723 K for CO oxidation. The extended X-ray absorption fine structure (EXAFS) results showed that the structure of the supported V2O5 phase consists of monomeric tetrahedral (Al–O)3–V=O units after dehydration in air at 623 K. However, the residuals of the EXAFS analysis indicate that an extra contribution has to be accounted for. This contribution probably consists of polymeric vanadate species. The structure remains unchanged during steady-state CO oxidation at 623 and 723 K. Furthermore, when oxygen was removed from the feed at 623 K, no changes in the spectra occurred. However, when oxygen is removed from the feed at 723 K, reduction of the vanadium species was observed, i.e., the vanadyl oxygen atom is removed. The V3+ ion subsequently migrates into the γ-Al2O3 lattice, where it is positioned at an Al3+ octahedral position. This migration process appears to be reversible; so the (Al–O)3–V=O units are thus restored by re-oxidation.

63 citations

Journal ArticleDOI
TL;DR: In this paper, an air-stable Ge(111) surface can be made by wet chemical HCl treatment in ambient atmosphere using X-ray photoelectron spectroscopy (XPS) and photon electrical field polarization-dependent Cl K-edge x-ray absorption spectrography (XANES).
Abstract: It is shown that an air‐stable Ge(111) surface can be made by wet chemical HCl treatment in ambient atmosphere. X‐ray photoelectron spectroscopy (XPS) and photon electrical field polarization‐dependent Cl K‐edge x‐ray absorption spectroscopy (XANES) were used to study the chemical structure and the physical orientation of chemisorbed Cl. It is found that Cl forms a monovalent bond with the Ge(111) dangling bond (DB) along 〈111〉 surface normal. The stability of HCl‐treated Ge(111) is attributed to the surface DBs being terminated by monochloride. Thermodynamics are found to be the governing force in the Ge–HCl reaction processes.

63 citations

Journal ArticleDOI
TL;DR: In this paper, the X-ray absorption near-edge structure (XANES) spectra of aluminium-containing oxides was used to quantify the variations of Al coordinations in transition alumina and silica-alumina with the Al content.
Abstract: The Al coordinations (AlO4 tetrahedra and AlO6 octahedra) in aluminium-containing oxides were successfully quantified by the curve fitting analysis of Al K-edge X-ray absorption near-edge structure (XANES). XANES spectra of aluminium-containing oxides showed three distinguishable peaks: one at 1566 eV assignable to tetrahedral AlO4 and two at 1568 and 1572 eV characteristic of octahedral AlO6. For the five reference oxides of well-known local structures, the ratio of the peak area at 1566 eV to that at 1568 eV estimated by curve fitting analysis agreed well with the known ratio of AlO4 to AlO6 species, when mixed Gaussian–Lorentzian functions were employed. This method was applied to quantify the variations of Al coordinations in transition alumina with the calcination temperature and in silica–alumina with the Al content.

62 citations

Journal ArticleDOI
J. Rothe1, Josef Hormes1, H. Bönnemann1, and W. Brijoux1, K. Siepen1 
TL;DR: In this paper, an in situ X-ray absorption near edge structure (XANES) investigation was performed for the first time during the colloid synthesis, which revealed the formation of an intermediate Cu+ state prior to the nucleation of the particles, thus giving direct insight into the mechanism of colloid formation.
Abstract: The reduction of [N(octyl)4]2[CuCl2Br2] in organic solution (toluene) using Li[BEt3H] leads to colloidal Cu protected by cationic surfactants (NR4+). According to HRTEM (high-resolution transmission electron microscopy) and UV/vis data, the organosol is composed of relatively large Cu particles with diameters of between 5 and 10 nm. An in situ XANES (X-ray absorption near edge structure) investigation was performed for the first time during the colloid synthesis. Our measurements revealed the formation of an intermediate Cu+ state prior to the nucleation of the particles, thus giving direct insight into the mechanism of the colloid formation. The significant differences between the near edge structures of the bulk sample and the colloidal Cu have to be traced back to structural disorder in the lattice of this nanosized material.

62 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023186
2022403
2021212
2020232
2019242
2018256