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SOLABS (under construction)

The bending magnet beamline SOLABS will be dedicated to X-ray absorption spectroscopy (XAS) and related techniques in the energy range from 1 keV to ~12–15 keV, covering the K absorption edges of chemical elements between Mg and Se along with the L and M edges of many other elements. XAS is a non-destructive, element specific characterization method which can be applied to both crystalline and amorphous materials, liquids and samples in the gas phase. Moreover, XAS measurements can be performed under application relevant conditions (in situ). Both XANES (X-ray absorption near-edge structure) and EXAFS (extended X-ray absorption fine structure) data contain valuable structural information about the atomic environment of the absorber atoms in the materials under investigation. At SOLABS XAS spectra can be recorded in transmission or fluorescence mode.

The beamline SOLABS (XAS-HN) is intended for fundamental and applied research in:

  • materials science, physics and chemistry (investigation of functional materials, esp. alloys, oxidic systems and catalysts, coatings, adhesives, etc.)
  • biomedicine (investigation of metalloproteins, investigation of the stability, uptake and therapeutic mechanism of action of inorganic and bio-inorganic drugs, etc.)
  • environmental protection (e.g., speciation of toxic elements during bioaccumulation).

In Spring 2021 commissioning will take place, and user operation will start in Summer 2021.

Extended X-ray Absorption Fine Structure (EXAFS)

EXAFS spectroscopy provides information about the average coordination number around the absorber atoms and bond distances

Selected examples from published studies

EXAFS - example 1
 

(a) Schematic illustration of Pt atoms deposited on nitrogen-doped carbon dots (Pt–NCDs) and (b) Fourier transformed Pt L3-edge EXAFS spectra of Pt–NCDs hybridized with TiO2 film, and of PtO2, PtCl2 and Pt foil as references for comparison (measured at beamline B18, Diamond Light Source).

The absence of a scattering peak in the region 2-3.5 Å, corresponding to a Pt-Pt bond, indicates that only isolated Pt atoms are bound to the NCD support, and the single peak at 1.6 Å reveals that they are coordinated to light atoms (4-5 carbon atoms) on the support. 

This example shows that EXAFS data can be used to distinguish between single-atom catalysts and small clusters or nanoparticles bound to the support. Pt single-atoms are important as catalysts for photocatalytic hydrogen production. 

Adapted from Hui Luo, Ying Liu, Stoichko D. Dimitrov, Ludmilla Steier, Shaohui Guo, Xuanhua Li, Jingyu Feng, Fei Xie, Yuanxing Fang, Andrei Sapelkin, Xinchen Wang and Maria-Magdalena Titirici, Pt single-atoms supported on nitrogen-doped carbon dots for highly efficient photocatalytic hydrogen generation, J. Mater. Chem. A, 2020, 8, 14690.
DOI: 10.1039/d0ta04431h

 

EXAFS - example 2
 

(left) Preparation of 17 atoms Pt clusters deposited on γ-Al2O3 (Pt17/γ-Al2O3)

(right) Fourier transform of Pt L3-edge EXAFS spectra of [Pt17(CO)12(PPh3)8]Cln, Pt17(CO)12(PPh3)8/γ-Al2O3, and Pt17/γ-Al2O3 together with EXAFS data of Pt foil and PtO2. In the spectrum of Pt17/γ-Al2O3 the peak at 1.7 Å is attributed to Pt–C or Pt–O bonds at the Pt17/γ-Al2O3 interface.

EXAFS data shows that in the Pt17/γ-Al2O3 system the supported Pt17 is not present in the form of oxide but has a framework structure like a metal cluster. Moreover, it was shown that supported Pt17 clusters are covered by CO molecules at normal temperature. CO molecules adsorbed on fine Pt17 supported clusters generally has a longer C–O bond compared to larger Pt supported nanoparticles, promoting the oxidation reaction and possibly contributing to the high catalytic activity of the Pt17/γ-Al2O3 system for carbon monoxide and propylene oxidation in comparison to γ-Al2O3-supported larger Pt nanoparticles (PtNP/γ-Al2O3)prepared by conventional impregnation.

Adapted from Yuichi Negishi, Nobuyuki Shimizu, Kanako Funai, Ryo Kaneko, Kosuke Wakamatsu, Atsuya Harasawa, Sakiat Hossain, Manfred E. Schuster, Dogan Ozkaya, Wataru Kurashige, Tokuhisa Kawawaki, Seiji Yamazoe and Shuhei Nagaoka, γ-Alumina-supported Pt17 cluster: controlled loading, geometrical structure, and size-specific catalytic activity for carbon monoxide and propylene oxidation, Nanoscale Adv., 2020, 2, 669-678. https://doi.org/10.1039/C9NA00579J

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X-ray absorption near edge structure (XANES)

XANES spectra are highly sensitive to the coordination environment of the absorber atoms (e.g., oxidation state)

Selected examples from published studies

XANES - example 1

 

 

Sulfur K-edge XANES spectra of substances with sulphur atoms in different oxidation states, attached to different ligands and in different coordination geometries. Obviously, different coordination environments cause characteristic features in XANES spectra, which can serve as ´spectral fingerprints´, and the sulfur speciation in an unknown sample can be determined by comparison with reference XANES spectra. Moreover, XANES spectra can be fit to linear combinations of reference spectra, from which the relative concentrations of the different species can directly be obtained. 

Adapted from Gøril Jahrsengene, Hannah C. Wells, Stein Rorvik, Arne Petter Ratvik, Richard G. Haverkamp & Ann Mari Svensson, A XANES Study of Sulfur Speciation and Reactivity in Cokes for Anodes Used in Aluminum Production, METALL MATER TRANS B 49, pages1434–1443(2018) https://doi.org/10.1007/s11663-018-1215-x

XANES - example 2

 

 

Linear combination fitting (LCF) of Cl K-edge XANES spectra of Ce glass-ceramics with nominal (a) 0.9 wt% Cl and (b) 1.7 wt% Cl; (c) comparison of the weighted contributions of reference compounds fitted to the Cl K-edge XANES data of Ce-free and Ce-incorporated glass-ceramics (samples were fabricated with CeO2, which model a PuO2 surrogate). XANES spectroscopy was used to investigate the potential application of an albite glass-zirconolite ceramic material for immobilisation of chloride contaminated plutonium oxide residues. XANES data confirm partitioning of Cl to the glass phase with exsolution of crystalline NaCl above the chlorine solubility limit. LCF results indicate an association of Cl with Na and Ca modifier cations, with environments characteristic of the aluminosilicate chloride minerals eudialyte, sodalite, chlorellestadite and afghanite. This study demonstrates the compatibility of the glass-ceramic wasteform toward Cl solubility at the expected incorporation rate (below the determined solubility limit) and provides confidence that upstream heat treatment or blending of waste feed are not required.

Adapted from Stephanie M. Thornber, Lucy M. Mottram, Amber R. Mason, Paul Thompson, Martin C. Stennett and Neil C. Hyatt, Solubility, speciation and local environment of chlorine in zirconolite glass–ceramics for the immobilisation of plutonium residues, RSC Adv., 2020, 10, 32497. DOI: 10.1039/d0ra04938g   

XANES - example 3

Vanadium K-edge XANES spectra of (a) electrochemically lithiationed V2O3(SO4)2 electrodes at various states of discharge and charge and (b) chemically lithiated V2O3(SO4)2 samples compared to the reference materials V2O5, VOSO4·3H2O and V2O3; (c) vanadium K-edge Energy (at half-height) as a function of oxidation state. In this case, XANES spectroscopy was used to investigate Li+ insertion into V2O3(SO4)2 (promising material for high energy density lithium-ion batteries) via electrochemical and chemical routes. The results show that 2.0 Li+ ions can be incorporated electrochemically, resulting in Li2V2O3(SO4)2 attributed to the V4+/V5+ redox couple. For the chemically lithiated materials up to 4.0 Li+ ions can be inserted into V2O3(SO4)2, reducing V5+ to V3+.

Reproduced from Stephanie F. Linnell, Julia L. Payne, David M. Pickup, Alan V. Chadwick, A. Robert Armstong and John T. S. Irvine, Lithiation of V2O3(SO4)2 – a flexible insertion host, J. Mater. Chem. A, 2020, 8, 19502. DOI: 10.1039/d0ta06608g

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The SOLABS beamline was especially designed for XANES/EXAFS measurements in the tender X-ray range, i.e., at the K absorption edges of important elements such as P, S, Si, Al and Mg. Besides, SOLABS` energy range also includes K-edges of heavier elements up to Se, L-edges of elements up to Bi and some M-edges of elements including U, which allows investigation of a variety of highly relevant materials.

The beamline is built by the project leader Hochschule Niederrhein University of Applied Sciences  (Germany) in collaboration with the Synchrotron Light Research Institute (Thailand), the Physics Institute of Bonn University and National Synchrotron Radiation Centre SOLARIS Jagiellonian University.

Beamline parameters:

Beamline radiation source: Bending magnet

Available (optimal) energy range: 1000–12000(15000) eV

Energy resolution ΔE/E: ~ 10-4

Predicted photon flux at source: 1012-1010 [ph/s/0.1 %]

Polarization: Linear

Research techniques: absorption spectroscopy, XANES, EXAFS, XRF