Local coordination geometry around Cu and Cu ions in silicate glasses: an X-ray absorption near edge structure investigation

2000 ◽  
Vol 14 (2) ◽  
pp. 211-216 ◽  
Author(s):  
C. Maurizio ◽  
F. d'Acapito ◽  
M. Benfatto ◽  
S. Mobilio ◽  
E. Cattaruzza ◽  
...  
Keyword(s):  
Silicate Glasses ◽  
Coordination Geometry ◽  
Structure Investigation ◽  
Edge Structure ◽  
X Ray ◽  
Local Coordination ◽  
X Ray Absorption ◽  
Cu Ions

X-ray absorption near edge structure investigation of iron–sodium silicate glasses

2011 ◽  
Vol 357 (22-23) ◽  
pp. 3803-3806 ◽  
Author(s):  
M. Faiz ◽  
A. Mekki ◽  
M.S. Kariapper ◽  
B.S. Mun ◽  
Z. Hussain
Keyword(s):  
Sodium Silicate ◽  
Silicate Glasses ◽  
Structure Investigation ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

Oxygen Reduction Effect on T’-Pr2-xCexCuO4 Nanopowders in the Underdoped Regime Studied by X-Ray Absorption near Edge Structure

2018 ◽  
Vol 936 ◽  
pp. 93-97 ◽  
Author(s):  
Irfanita Resky ◽  
Putu Eka Dharma Putra ◽  
Triono Bambang ◽  
Saiyasombat Chatree ◽  
Kamonsuangkasem Krongthong ◽  
...  
Keyword(s):  
Oxidation State ◽  
Oxidation States ◽  
Edge Structure ◽  
X Ray ◽  
Reduction Annealing ◽  
Gas Atmosphere ◽  
Reduction Effect ◽  
Ar Gas ◽  
X Ray Absorption ◽  
Cu Ions

This research is aimed to examine oxidation state of Copper (Cu) in both as-synthesized and reduced T’-Pr2-xCexCuO4 (T’-PCCO) with x = 0, 0.10, and 0.15 using Cu K-edge x-ray absorption near edge structure (XANES). The T‘-PCCO nanopowders were successfully synthesized by the chemically dissolved method with HNO3 as a dissolving agent continued by calcination at 1000°C for 15 h. The reduced T’-PCCO nanopowders were obtained by reduction annealing process at 700°C for 5 h under Ar gas atmosphere. The analyses of XANES spectra show that oxidation states of the Cu ions in all of the T'-PCCO nanopowders have values between +1 and +2. This indicates the existence of electron doping in the CuO2 planes, even in the undoped T’-structure. It is found that the oxidation states of the Cu ions change after reduction annealing depending on the existence of apical oxygen in the T'-structure. Based on the XANES analyses, it is revealed that the change of oxidation state is influenced by the presence of both electron and hole carriers in the two-carrier model of T’-structure.

Manganese speciation in soils using X-ray absorption spectroscopy

2020 ◽  
Author(s):  
Teresa Zahoransky ◽  
Christian Mikutta
Keyword(s):  
Absorption Spectroscopy ◽  
Chemical Reactivity ◽  
Mixed Valence ◽  
Oxidation States ◽  
Plant Residues ◽  
Edge Structure ◽  
Coordination Environment ◽  
X Ray ◽  
Local Coordination ◽  
X Ray Absorption

<p>Being one of Earth´s most redox-active elements, manganese participates in a great variety of environmental processes and is recognized as a key player controlling carbon turnover and oxidative transformation of organic and inorganic pollutants in soils. Moreover, Mn(III), Mn(IV) or mixed-valence Mn(III/IV) oxides and (oxy)hydroxides are highly effective sorbents for metal pollutants and nutrients in soils. Chemical reactivity, mobility, and bioavailability of Mn depend crucially on its speciation (chemical form). Yet, speciation studies on soil Mn are scarce. Therefore, we employed Mn K-edge (6,539 eV) X-ray absorption spectroscopy (XAS) to determine the oxidation states and local coordination environment (<5 Å) of Mn in oxic bulk soils (Cambisols, Luvisols, Stagnosol) from various field sites in Germany. Our XAS analyses cover 23 soil L, O, A, B, and C horizons exhibiting total Mn concentrations of between 200 and 2,300 mg/kg. For comparison, we also analyze a suite of 31 Mn reference compounds, including Mn carbonate, phosphate, oxides and (oxy)hydroxides, silicates, organic Mn compounds as well as clay and hydroxide minerals with adsorbed Mn(II). X-ray absorption near-edge structure (XANES) spectra are evaluated for the oxidation states of soil Mn using linear combination fit (LCF) analysis. In addition, the average local coordination environment of Mn in the soil samples is assessed by shell-fitting of extended X-ray absorption fine structure (EXAFS) spectra. Based on our XAS results, we will test the following hypotheses: (1) Soil L/O horizons comprise predominantly organically complexed Mn(II) and Mn(III), dominated by the former Mn species; (2) soil A horizons are dominated by Mn(III/IV) in Mn(III/IV)-oxide structures owing to high microbial activity, release of Mn(II) from primary silicates and/or plant residues, and its subsequent (a)biotic oxidation and precipitation as Mn(III/IV) oxides; (3) soil B horizons of different genesis differ in their bulk Mn speciation; Bt horizons of Luvisols are dominated by Mn(II) associated with phyllosilicates, whereas the Stagnosol Bg horizon is dominated by layer-type Mn(III/IV) oxides. In summary, our study will provide first comprehensive data on bulk Mn speciation in three major European soil types. This knowledge is a prerequisite for a better understanding of the biogeochemical Mn cycle in soils.</p>

Experimental and theoretical study of the structural environment of magnesium in minerals and silicate glasses using X-ray absorption near-edge structure

2008 ◽  
Vol 36 (5) ◽  
pp. 241-257 ◽  
Author(s):  
Nicolas Trcera ◽  
Delphine Cabaret ◽  
Stéphanie Rossano ◽  
François Farges ◽  
Anne-Marie Flank ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Silicate Glasses ◽  
Edge Structure ◽  
X Ray ◽  
Structural Environment ◽  
X Ray Absorption

X-ray absorption near-edge structure and extended x-ray absorption fine-structure investigation of Pd silicides

1985 ◽  
Vol 32 (2) ◽  
pp. 612-622 ◽  
Author(s):  
M. De Crescenzi ◽  
E. Colavita ◽  
U. Del Pennino ◽  
P. Sassaroli ◽  
S. Valeri ◽  
...  
Keyword(s):  
Fine Structure ◽  
Structure Investigation ◽  
Edge Structure ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption

X-ray absorption near edge structure investigation of vanadium-doped ZnO thin films

2006 ◽  
Vol 515 (4) ◽  
pp. 1377-1379 ◽  
Author(s):  
M. Faiz ◽  
N. Tabet ◽  
A. Mekki ◽  
B.S. Mun ◽  
Z. Hussain
Keyword(s):  
Thin Films ◽  
Zno Thin Films ◽  
Structure Investigation ◽  
Edge Structure ◽  
X Ray ◽  
Doped Zno ◽  
X Ray Absorption

3-Deoxy-D-erythro-hexos-2-ulose bis(thiosemicarbazone) copper(II) chelate. Studies in solution and in the solid state

1999 ◽  
Vol 77 (9) ◽  
pp. 1492-1497 ◽  
Author(s):  
Sandra Signorella ◽  
Claudia Palopoli ◽  
Alejandro Frutos ◽  
Graciela Escandar ◽  
Tomoaki Tanase ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Structure Stability ◽  
Planar Geometry ◽  
Powdered Sample ◽  
Coordination Geometry ◽  
Spectra Analysis ◽  
X Ray ◽  
Local Coordination ◽  
Square Planar ◽  
X Ray Absorption

The 3-deoxy-D-erythro-hexos-2-ulose bis(thiosemicarbazone) (LH2) acts as a tetradentate ligand with S2N2 donor sites to form a copper(II) chelate (Cu(II)L). The Cu K-edge X-ray absorption spectra analysis of a powdered sample revealed a square-planar S2N2 local coordination geometry with average Cu—N and Cu—S distances of 1.92 and 2.33 Å. The EXAFS and XANES spectra and the structural parameters of a DMF solution sample indicate the retention of the square-planar local structure of the Cu(II)S2N2 chromophore upon dissolution. Semiempirical PM3 calculations indicate that the structure of Cu(II)L with the copper(II) ion bound to the S2N2 donor set disposed in a square-planar geometry is the most favorable one (with the highest |ΔHf |). The formation constant (log Kf = 20.65 ± 0.06) of the neutral [CuL] species was calculated in 30% v/v dioxane-water and the protonation and deprotonation constants determined.Key words: bis(thiosemicarbazone), copper(II), chelate, structure, stability constant.

Titanium coordination in silicate glasses investigated using O K-edge X-ray absorption spectroscopy

2003 ◽  
Vol 67 (4) ◽  
pp. 597-607 ◽  
Author(s):  
G. S. Henderson ◽  
Xiaoyang Liu ◽  
M. E. Fleet
Keyword(s):  
Glass Sample ◽  
Surface Region ◽  
Bulk Sample ◽  
Silicate Glasses ◽  
Titanium Silicate ◽  
Edge Structure ◽  
Near Surface ◽  
X Ray ◽  
Edge Features ◽  
X Ray Absorption

AbstractA series of titanium silicate glasses along the composition joins TiO2-SiO2, TiO2-Na2SiO3, TiO2-K2SiO3 and TiO2-CaSiO3, has been examined using oxygen K-edge X-ray absorption near edge structure spectroscopy (XANES) confined to the near-surface region. Sharp pre-edge features in the spectra can be used to determine the Ti coordination in the glasses. The presence of [4]Ti is indicated by a pre-edge peak at ∼534 eV while [5]Ti is indicated by a peak at ∼533 eV. Titanium exists in all these glasses as [4]Ti and [5]Ti with no [6]Ti being present. For alkali-containing glasses the [5]Ti site becomes more prevalent with increasing TiO2. TiO2-K2SiO3 compositions contain a greater proportion of [4]Ti than comparable Na2O compositions. This is consistent with earlier Ti L-edge findings. The TEY spectra for the TiO2-CaSiO3 compositions indicate the presence of significant amounts of [5]Ti at high TiO2 contents; however, comparison of TEY (near surface) and FY (bulk sample) XANES shows that the [5]Ti is confined to the surface of the glass sample with the bulk of the glass containing [4]Ti.

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