Investigation of the local environment of iodate in hydroxyapatite by combination of X-ray absorption spectroscopy and DFT modeling

RSC Advances ◽  
2014 ◽  
Vol 4 (28) ◽  
pp. 14700-14707 ◽  
Author(s):  
Danielle Laurencin ◽  
Delphine Vantelon ◽  
Valérie Briois ◽  
Christel Gervais ◽  
Antoine Coulon ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Local Environment ◽  
X Ray ◽  
Dft Modeling ◽  
X Ray Absorption

scholarly journals Correction: Investigation of the local environment of iodate in hydroxyapatite by combination of X-ray absorption spectroscopy and DFT modeling

RSC Advances ◽  
2014 ◽  
Vol 4 (81) ◽  
pp. 43166-43166
Author(s):  
Danielle Laurencin ◽  
Delphine Vantelon ◽  
Valérie Briois ◽  
Christel Gervais ◽  
Antoine Coulon ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Local Environment ◽  
X Ray ◽  
Dft Modeling ◽  
X Ray Absorption

Titanium environment in TiO2–BaO–ZnO–B2O3 glasses by x-ray absorption spectroscopy

2000 ◽  
Vol 15 (3) ◽  
pp. 793-797 ◽  
Author(s):  
N. Watanabe ◽  
A. Y. Ramos ◽  
M. C. M. Alves ◽  
H. Tolentino ◽  
O. L. Alves ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Local Environment ◽  
Titanium Content ◽  
Optical Performance ◽  
X Ray ◽  
X Ray Absorption

The local environment of titanium in glasses of the system TiO2–BaO–ZnO–B2O3 was studied by x-ray absorption spectroscopy. In all glasses, for TiO2 content varying from 35 to 49 mol%, the titanium atoms are mainly fourfold coordinated network formers. For the glass with the highest titanium content, about 20% of the titanium enters into a sixfold environment, indicating the presence of precrystalline nuclei. These nuclei are responsible for the decrease of the optical performance of the glass above threshold titanium content, prior to any observable crystallization.

X-ray Absorption Spectroscopy study of lithium insertion mechanism in Li1.2V3O8

2002 ◽  
Vol 756 ◽  
Author(s):  
N. Bourgeon ◽  
J. Gaubicher ◽  
D. Guyomard ◽  
G. Ouvrard
Keyword(s):  
Absorption Spectroscopy ◽  
Local Environment ◽  
Lithium Insertion ◽  
Spectroscopy Study ◽  
X Ray ◽  
Lithium Insertion Mechanism ◽  
Insertion Mechanism ◽  
Reversible Evolution ◽  
X Ray Absorption

ABSTRACTX-ray absorption spectroscopy (XAS) measurements were performed to thoroughly understand lithium insertion mechanism in Li1.2V3O8. The evolution of the absorption pre-edge and edge corresponding to the local environment of the vanadium in the bulk has been examined by ex-si tu XAS measurement at the vanadium K edge, during the first discharge-charge cycle. The results show a regular and reversible evolution of the pre-edge intensity, the edge position and the vanadium environment toward nearly perfect VO6 octahedra.

X-ray absorption spectroscopy studies of phase transformations and amorphicity in nanotitania powder and silica–titania core–shell photocatalysts

2008 ◽  
Vol 41 (6) ◽  
pp. 1009-1018 ◽  
Author(s):  
S. H. Lim ◽  
N. Phonthammachai ◽  
T. Liu ◽  
T. J. White
Keyword(s):  
Absorption Spectroscopy ◽  
Sol Gel ◽  
Local Environment ◽  
Core Shell ◽  
Transformation Mechanism ◽  
X Ray ◽  
Amorphous Content ◽  
Silica Substrate ◽  
The Core ◽  
X Ray Absorption

The local environment of titanium in nanocrystalline sol-gel synthesized titania, cobaltiferous titania and silica–titania core–shell photocatalysts was investigated using X-ray absorption spectroscopy (XAS). Anatase reconstructively transforms to rutileviaa persistent amorphous phase that is retained, in part, up to 1273 K. In nanotitania, temperature-dependent trends in Ti order correlation observed by XAS parallel the development of amorphous content extracted from powder X-ray diffraction patterns, such that amorphicity shows a transient maximum at ∼873 K with the onset of rutile crystallization. Cobaltiferous and core–shell materials behaved similarly, but with anatase retained to 973 and 1273 K, respectively. In the former, cobalt redox reactions may stabilize anatase to higher temperatures by ready charge-balancing during the loss of hydroxyl and the formation of oxygen vacancies. In the core–shell architecture, higher Ti coordination and interatomic distance variance in the first- and second-nearest-neighbour shells are maintained to 1273 K by interaction of a substantially aperiodic TiO6network with the glassy silica substrate, which inhibits crystallization of rutile from the amorphous intermediate. Comparisons are also drawn with the commercial P25 catalyst. The overall transformation mechanism can be summarized as gel → non-stoichiometric anatase → amorphous titania → rutile. Smaller anatase crystals and a higher average Ti—Ti coordination environment in the core–shell structure may enhance photocatalytic activity directly, by creating larger specific surface areas and hosting reactive defects, or indirectly, by inhibiting exciton annihilation in aperiodic titania and delaying the crystallization of less photoactive rutile.

An X-ray absorption spectroscopy study of the local environment of iron in degradable iron–phosphate glasses

2008 ◽  
Vol 354 (52-54) ◽  
pp. 5542-5546 ◽  
Author(s):  
Dong Qiu ◽  
Robert M. Moss ◽  
Dave M. Pickup ◽  
Ifty Ahmed ◽  
Jonathan C. Knowles ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Local Environment ◽  
Iron Phosphate ◽  
Phosphate Glasses ◽  
Spectroscopy Study ◽  
X Ray ◽  
Iron Phosphate Glasses ◽  
X Ray Absorption

scholarly journals The local environment of metal sites in intracellular granules investigated by using X-ray-absorption spectroscopy

1984 ◽  
Vol 221 (3) ◽  
pp. 855-868 ◽  
Author(s):  
G N Greaves ◽  
K Simkiss ◽  
M Taylor ◽  
N Binsted
Keyword(s):  
Absorption Spectroscopy ◽  
Local Environment ◽  
Nearest Neighbour ◽  
Model Compounds ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption ◽  
Oxygen Bond ◽  
Phosphate Deposits ◽  
Phosphate Groups

We report the use of X-ray-absorption spectroscopy (x.a.s.) to study the local atomic environment of cations in intracellular granules from the hepatopancreas of Helix aspersa. Both the calcium K-edge in these concretions and the manganese K-edge in doped specimens were measured. Electron-microprobe measurements confirm that the introduced Mn2+ is concentrated in irregular growths on the surfaces of the granules. The near-edge structure (x.a.n.e.s.) of calcium is similar to that of manganese, indicating that the oxygen-co-ordination spheres of both cations share a similar symmetry. From the extended structure (e.x.a.f.s.) the metal-oxygen bond lengths of 0.230 nm (2.30A) for Ca-O and 0.218 nm (2.18A) for Mn-O [+/- 0.004 nm (0.04A)] were determined, reference being made to a variety of model compounds. The low density of the granules (2.07 g/cm3), together with the local atomic distribution, suggest an open hydrated structure for these phosphate deposits. Detailed analysis of the distribution of nearest-neighbour oxygen atoms demonstrates that this is asymmetric and considerably broader for Ca2+ than for Mn2+. Compared with the model compounds, the Ca2+ environment in the granules is similar to that observed in Ca2P2O7. I.r. spectra indicate the presence of condensed phosphate groups in the granules, with the strong possibility these are pyrophosphate (P2O7(4-) groups.

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