An EXAFS spectroscopic study of Am(III) complexation with lactate

2015 ◽  
Vol 22 (6) ◽  
pp. 1469-1474 ◽  
Author(s):  
Daniel R. Fröhlich ◽  
Andrej Skerencak-Frech ◽  
Ugras Kaplan ◽  
Carsten Koke ◽  
André Rossberg ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Structural Model ◽  
Ph Dependence ◽  
Structural Data ◽  
X Ray ◽  
Coordination Numbers ◽  
Data Coordination ◽  
X Ray Absorption ◽  
Good Agreement ◽  
Exafs Spectra

The pH dependence (1–7) of Am(III) complexation with lactate in aqueous solution is studied using extended X-ray absorption fine-structure (EXAFS) spectroscopy. Structural data (coordination numbers, Am—O and Am—C distances) of the formed Am(III)–lactate species are determined from the rawk3-weighted AmLIII-edge EXAFS spectra. Between pH 1 and pH 6, Am(III) speciation shifts continuously towards complexed species with increasing pH. At higher pH, the amount of complexed species decreases due to formation of hydroxo species. The coordination numbers and distances (3.41–3.43 Å) of the coordinating carbon atoms clearly point out that lactate is bound `side-on' to Am(III) through both the carboxylic and the α-hydroxy function of lactate. The experimentally determined coordination numbers are compared with speciation calculations on the basis of tabulated thermodynamic stability constants. Both EXAFS data and thermodynamic modelling are in very good agreement. The EXAFS spectra are also analyzed by iterative transformation factor analysis to further verify the determined Am(III) speciation and the used structural model.

The pH dependence of Am(III) complexation with acetate: an EXAFS study

2015 ◽  
Vol 22 (1) ◽  
pp. 99-104 ◽  
Author(s):  
Daniel R. Fröhlich ◽  
Andrej Skerencak-Frech ◽  
Nicole Bauer ◽  
André Rossberg ◽  
Petra J. Panak
Keyword(s):  
Structural Model ◽  
Ph Value ◽  
Ph Dependence ◽  
Bidentate Coordination ◽  
Coordination Numbers ◽  
Thermodynamic Constants ◽  
Exafs Study ◽  
X Ray Absorption ◽  
Good Agreement ◽  
Exafs Spectra

The complexation of acetate with Am(III) is studied as a function of the pH (1–6) by extended X-ray absorption fine-structure (EXAFS) spectroscopy. The molecular structure of the Am(III)–acetate complexes (coordination numbers, oxygen and carbon distances) is determined from the rawk3-weighted AmLIII-edge EXAFS spectra. The results show a continuous shift of Am(III) speciation with increasing pH value towards the complexed species. Furthermore, it is verified that acetate coordinates in a bidentate coordination mode to Am(III) (Am—C distance: 2.82 ± 0.03 Å). The EXAFS data are analyzed by iterative transformation factor analysis to further verify the chemical speciation, which is calculated on the basis of thermodynamic constants, and the used structural model. The experimental results are in very good agreement with the thermodynamic modelling.

Structural Investigation of the Hydrolysis-Condensation Process of a Modified Titanium Alkoxide.

1988 ◽  
Vol 121 ◽  
Author(s):  
Florence Babonneau ◽  
Anne Leaustic ◽  
Jacques Livage
Keyword(s):  
Structural Investigation ◽  
Structural Model ◽  
Structural Data ◽  
Titanium Isopropoxide ◽  
Condensation Process ◽  
Titanium Alkoxide ◽  
X Ray ◽  
Data Coordination ◽  
X Ray Absorption ◽  
C Nmr

ABSTRACTTitanium isopropoxide was modified with acetylacetone in order to get stable photosensitive colloids via an hydrolysis-condensation process. The various steps of this process were followed by infrared, 1H and 13C NMR and X-Ray absorption (XANES and EXAFS). The latter techniques provided some interesting structural data (coordination of titanium, Ti-O and Ti-Ti distances) on the various species, from the precursor to the colloids. A structural model is proposed for each one, with a scheme of the different reactions occuring during the process.

scholarly journals XANES and EXAFS of dilute solutions of transition metals at XFELs

2019 ◽  
Vol 26 (5) ◽  
pp. 1716-1724 ◽  
Author(s):  
Ruchira Chatterjee ◽  
Clemens Weninger ◽  
Anton Loukianov ◽  
Sheraz Gul ◽  
Franklin D. Fuller ◽  
...  
Keyword(s):  
High Repetition Rate ◽  
Dilute Solution ◽  
Delivery Methods ◽  
X Ray ◽  
Drop On Demand ◽  
Exafs Study ◽  
X Ray Absorption ◽  
Data Analysis Methods ◽  
Good Agreement ◽  
Exafs Spectra

This work has demonstrated that X-ray absorption spectroscopy (XAS), both Mn XANES and EXAFS, of solutions with millimolar concentrations of metal is possible using the femtosecond X-ray pulses from XFELs. Mn XAS data were collected using two different sample delivery methods, a Rayleigh jet and a drop-on-demand setup, with varying concentrations of Mn. Here, a new method for normalization of XAS spectra based on solvent scattering that is compatible with data collection from a highly variable pulsed source is described. The measured XANES and EXAFS spectra of such dilute solution samples are in good agreement with data collected at synchrotron sources using traditional scanning protocols. The procedures described here will enable XFEL-based XAS on dilute biological samples, especially metalloproteins, with low sample consumption. Details of the experimental setup and data analysis methods used in this XANES and EXAFS study are presented. This method will also benefit XAS performed at high-repetition-rate XFELs such as the European XFEL, LCLS-II and LCLS-II-HE.

scholarly journals An Investigation of the Structure of Amorphous Co-P Alloys. 2: EXAFS at the Phosphorous K-edge, a Feasibility Study

1998 ◽  
Vol 53 (10-11) ◽  
pp. 848-854
Author(s):  
Mi. Nuding ◽  
P. Lamparter ◽  
S. Steeb ◽  
F. Neißendorfer ◽  
F. Schäfers
Keyword(s):  
Fine Structure ◽  
Phase Shift ◽  
Amorphous Alloys ◽  
Reference Sample ◽  
Exafs Spectrum ◽  
Additional Contribution ◽  
X Ray ◽  
Coordination Numbers ◽  
X Ray Absorption ◽  
Exafs Spectra

AbstractAmorphous Co100-xPx foils in the concentration range 13.4 ≤ x ≤ 26 were produced by electrodeposition. The extended X-ray absorption fine structure (EXAFS) at the phosphorous K-edge was measured in transmission mode. The phase shift was determined from the EXAFS spectrum of a crystalline Co2P reference sample. The EXAFS spectra of the amorphous Co-P alloys are characterized mainly by one single contribution from a shell of Co-atoms at a distance of 2.3 Å around the P-atoms. A small additional contribution at a shorter distance of 2.0 Å may be a hint on some direct P-P neighbours. The evaluation of reliable coordination numbers from the EXAFS spectra of the amorphous alloys is not possible.

Local atomic structure in tetragonal pure ZrO2nanopowders

2010 ◽  
Vol 43 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Leandro M. Acuña ◽  
Diego G. Lamas ◽  
Rodolfo O. Fuentes ◽  
Ismael O. Fábregas ◽  
Márcia C. A. Fantini ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Local Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Crystallite Sizes ◽  
Exafs Study ◽  
The Difference ◽  
X Ray Absorption ◽  
Good Agreement

The local atomic structures around the Zr atom of pure (undoped) ZrO2nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO2nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr—O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye–Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to thezdirection; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

Nitrogen K-edge X-ray absorption near edge structure (XANES) spectra of purine-containing nucleotides in aqueous solution

2014 ◽  
Vol 141 (5) ◽  
pp. 055102 ◽  
Author(s):  
Hiroyuki Shimada ◽  
Taishi Fukao ◽  
Hirotake Minami ◽  
Masatoshi Ukai ◽  
Kentaro Fujii ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

X-Ray Absorption Spectroscopic Studies of Catalytic Materials

1988 ◽  
Vol 143 ◽  
Author(s):  
G. H. Via ◽  
J. H. Sinfelt ◽  
G. Meitzner ◽  
F. W. Lytle
Keyword(s):  
Fine Structure ◽  
Physical Environment ◽  
Bimetallic Catalysts ◽  
Spectroscopic Studies ◽  
Interatomic Distances ◽  
X Ray ◽  
Coordination Numbers ◽  
Supported Platinum ◽  
High Fraction ◽  
X Ray Absorption

AbstractX-ray absorption spectra (XAS) contain information in the LIII near-edge region on filling of the absorber d-band, and in the extended fine-structure region on the physical environment of the absorber. We report here an evaluation of the effect on platinum LIII edges of preparation in clusters with a high fraction of Pt atoms at the surface. We also report the effects on platinum and rhenium LIII edges from addition of copper. These effects are surprisingly small.We have also re-evaluated extended x-ray absorption fine-structure spectra (EXAFS) of platinum and rhenium in alumina-supported platinum-rhenium bimetallic catalysts. A novel feature of this new analysis was the requirement that interatomic distances, coordination numbers, and Debye-Waller type factors maintain certain physically necessary relationships among themselves. This procedure decreased the number of free variables and increased the amount of information returned by the analysis.

scholarly journals Local and electronic structure around Ga in CdTe: evidence of DX- and A-centers

2012 ◽  
Vol 20 (1) ◽  
pp. 166-171
Author(s):  
Vasil Koteski ◽  
Jelena Belošević-Čavor ◽  
Petro Fochuk ◽  
Heinz-Eberhard Mahnke
Keyword(s):  
Density Functional ◽  
Plane Waves ◽  
Lattice Relaxation ◽  
Defect Structures ◽  
Functional Theory ◽  
Edge Structure ◽  
X Ray ◽  
First Time ◽  
X Ray Absorption ◽  
Good Agreement

The lattice relaxation around Ga in CdTe is investigated by means of extended X-ray absorption spectroscopy (EXAFS) and density functional theory (DFT) calculations using the linear augmented plane waves plus local orbitals (LAPW+lo) method. In addition to the substitutional position, the calculations are performed for DX- and A-centers of Ga in CdTe. The results of the calculations are in good agreement with the experimental data, as obtained from EXAFS and X-ray absorption near-edge structure (XANES). They allow the experimental identification of several defect structures in CdTe. In particular, direct experimental evidence for the existence of DX-centers in CdTe is provided, and for the first time the local bond lengths of this defect are measured directly.

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