An attempt at kidney stone analysis with the application of synchrotron radiation

X‐ray absorption near‐edge spectroscopy (XANES) is a spectroscopic technique using synchrotron light to determine the valence state of excited atoms as well as the electronegativity of their neighbouring atoms. XANES spectra can provide information about the chemical bond in the second coordination shell of the excited atom. In this study, XANES spectra of unknown compounds from human kidney stones were recorded around the K‐edges of sulfur, phosphorus and calcium. The XANES results agree well with the diffractogram data of the same stones obtained through an X‐ray powder diffraction (XRPD) technique. By comparing the measurement techniques presented here, it is shown that XANES requires a smaller amount of each sample than XRPD for analysis.     

Synchrotron XANES and ED‐XRF analyses of fine‐paste ware from 13th to 14th century maritime Southeast Asia

The combination of energy dispersive X‐ray fluorescence (ED‐XRF) and synchrotron X‐ray absorption near‐edge structure (XANES) provides the detailed composition of fine‐paste ware (FPW) kendis, dated back to 13th–14th century maritime Southeast Asia. Sources of clay and production sites were classified according to Al₂O₃, SiO₂, α‐Fe₂O₃ and γ‐Fe₂O₃ as well as trace elements. The similarities based on these components provided another evidence of a trade route between Kota Cina in North Sumatra of Indonesia and Kok Moh on Satingphra Peninsula, a well‐known production area in present‐day Thailand. In additions, the uniquely large contribution of α‐Fe₂O₃ in XANES spectra suggests that Nakhon Si Thammarat province of Thailand could also be one of FPW production areas in maritime Southeast Asia. Copyright © 2017 John Wiley & Sons, Ltd.     

Soft X‐ray absorption spectroscopy and resonant inelastic X‐ray scattering spectroscopy below 100 eV: probing first‐row transition‐metal M‐edges in chemical complexes

X‐ray absorption and scattering spectroscopies involving the 3d transition‐metal K‐ and L‐edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using the M‐edges, which are below 100 eV. Synchrotron‐based X‐ray sources can have higher energy resolution at M‐edges. M‐edge X‐ray absorption spectroscopy (XAS) and resonant inelastic X‐ray scattering (RIXS) could therefore provide complementary information to K‐ and L‐edge spectroscopies. In this study, M_2,3‐edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition, M_2,3‐edge RIXS on NiO, NiF₂ and two other covalent complexes have been performed and different d–d transition patterns have been observed. Although still preliminary, this work on 3d metal complexes demonstrates the potential to use M‐edge XAS and RIXS on more complicated 3d metal complexes in the future. The potential for using high‐sensitivity and high‐resolution superconducting tunnel junction X‐ray detectors below 100 eV is also illustrated and discussed.     

Extended X‐ray absorption fine structure and multiple‐scattering simulation of nickel dithiolene complexes Ni[S2C2(CF3)2]2n (n = −2, −1, 0) and an olefin adduct Ni[S2C2(CF3)2]2(1‐hexene)

A series of Ni dithiolene complexes Ni[S₂C₂(CF₃)]₂ⁿ (n = ?2, ?1, 0) ( 1 , 2 , 3 ) and a 1‐hexene adduct Ni[S₂C₂(CF₃)₂]₂(C₆H₁₂) ( 4 ) have been examined by Ni K‐edge X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine‐structure (EXAFS) spectroscopies. Ni XANES for 1 – 3 reveals clear pre‐edge features and approximately +0.7 eV shift in the Ni K‐edge position for `one‐electron' oxidation. EXAFS simulation shows that the Ni—S bond distances for 1 , 2 and 3 (2.11–2.16 Å) are within the typical values for square planar complexes and decrease by ～0.022 Å for each `one‐electron' oxidation. The changes in Ni K‐edge energy positions and Ni—S distances are consistent with the `non‐innocent' character of the dithiolene ligand. The Ni—C interactions at ～3.0 Å are analyzed and the multiple‐scattering parameters are also determined, leading to a better simulation for the overall EXAFS spectra. The 1‐hexene adduct 4 presents no pre‐edge feature, and its Ni K‐edge position shifts by ?0.8 eV in comparison with its starting dithiolene complex 3 . Consistently, EXAFS also showed that the Ni—S distances in 4 elongate by ～0.046 Å in comparison with 3 . The evidence confirms that the neutral complex is `reduced' upon addition of olefin, presumably by olefin donating the π‐electron density to the LUMO of 3 as suggested by UV/visible spectroscopy in the literature.     

Relationship between the structural distortion and the Mn electronic state in La1−xCaxMnO3: a Mn K‐edge XANES study

A theoretical study of the X‐ray absorption near‐edge structure (XANES) spectra at the Mn K‐edge in the La_1?xCa_xMnO₃ series is reported. The relationship between the edge shift, the Ca–La substitution and the distortion of the MnO₆ octahedra in these systems has been studied. It is shown that, by correctly considering these effects simultaneously, the experimental XANES data are consistent with the presence of two different Mn local environments in the intermediate La_1?xCa_xMnO₃ compounds. By taking into account the energy shift associated with the modification of the MnO₆ distortion as Ca substitutes for La, it is possible to reproduce the XANES spectra of the intermediate‐doped compounds starting from the experimental spectra of the end‐members LaMnO₃ and CaMnO₃. These results point out the need to re‐examine the conclusions derived in the past from the simple analysis of the Mn K‐edge XANES edge‐shift in these materials. In particular, it is shown that the modification of the Mn K‐edge absorption through the La_1?xCa_xMnO₃ series is well reproduced by considering the simultaneous presence of both distorted and undistorted octahedra and, consequently, that the existence of charge‐ordering phenomena cannot be ruled out from the XANES data.     

Synchrotron‐based spectroscopy of X‐ray channeling through hollow capillary microchannels inside glass plates

Here, soft X‐ray synchrotron radiation transmitted through microchannel plates is studied experimentally. Fine structures of reflection and XANES Si L‐edge spectra detected on the exit of silicon glass microcapillary structures under conditions of total X‐ray reflection are presented and analyzed. The phenomenon of the interaction of channeling radiation with unoccupied electronic states and propagation of X‐ray fluorescence excited in the microchannels is revealed. Investigations of the interaction of monochromatic radiation with the inner‐shell capillary surface and propagation of fluorescence radiation through hollow glass capillary waveguides contribute to the development of novel X‐ray focusing devices in the future.     

SUT‐NANOTEC‐SLRI beamline for X‐ray absorption spectroscopy

The SUT‐NANOTEC‐SLRI beamline was constructed in 2012 as the flagship of the SUT‐NANOTEC‐SLRI Joint Research Facility for Synchrotron Utilization, co‐established by Suranaree University of Technology (SUT), National Nanotechnology Center (NANOTEC) and Synchrotron Light Research Institute (SLRI). It is an intermediate‐energy X‐ray absorption spectroscopy (XAS) beamline at SLRI. The beamline delivers an unfocused monochromatic X‐ray beam of tunable photon energy (1.25–10 keV). The maximum normal incident beam size is 13 mm (width) × 1 mm (height) with a photon flux of 3 × 10⁸ to 2 × 10¹⁰ photons s^?1 (100 mA)^?1 varying across photon energies. Details of the beamline and XAS instrumentation are described. To demonstrate the beamline performance, K‐edge XANES spectra of MgO, Al₂O₃, S₈, FeS, FeSO₄, Cu, Cu₂O and CuO, and EXAFS spectra of Cu and CuO are presented.     

On the correlation between the X‐ray absorption chemical shift and the formal valence state in mixed‐valence manganites

Here the correlation between the chemical shift in X‐ray absorption spectroscopy, the geometrical structure and the formal valence state of the Mn atom in mixed‐valence manganites are discussed. It is shown that this empirical correlation can be reliably used to determine the formal valence of Mn, using either X‐ray absorption spectroscopy or resonant X‐ray scattering techniques. The difficulties in obtaining a reliable comparison between experimental XANES spectra and theoretical simulations on an absolute energy scale are revealed. It is concluded that the contributions from the electronic occupation and the local structure to the XANES spectra cannot be separated either experimentally or theoretically. In this way the geometrical and electronic structure of the Mn atom in mixed‐valence manganites cannot be described as a bimodal distribution of the formal integer Mn³⁺ and Mn⁴⁺ valence states corresponding to the undoped references.     

Assessment of sulfur and iron speciation in a soil aggregate by combined S and Fe micro‐XANES: microspatial patterns and relationships

To test whether synchrotron‐based spectromicroscopy can be used to identify spatial patterns of sulfur (S) and iron (Fe) speciation as well as relationships between the speciation of S and Fe in soil colloids or aggregates at the micrometre and sub‐micrometre level, an anoxically prepared dissected soil aggregate (size ～1 mm³) was analyzed by µ‐XANES at the K‐edges of S (2472 eV) and Fe (7112 eV). The experiment included (i) elemental mapping at the S K‐edge (S, Si, Al) and the Fe K‐edge (Fe, Si), (ii) acquisition of 300 µm × 300 µm images of the region of interest with X‐ray energies of 2474 eV (addressing reduced organic and inorganic S), 2483 eV (total S), 7121 eV (divalent Fe) and 7200 eV (total Fe), as well as (iii) acquisition of S and Fe µ‐XANES spectra at two different positions, where image analysis suggested the dominance of reduced and oxidized S and Fe, respectively. Image analysis revealed a heterogeneous distribution of total Si, S and Fe as well as of different S and Fe species in the aggregate. Microregions which were either enriched in reduced or in oxidized S and Fe could be identified. A microregion with a large contribution of oxidized S (sulfate, sulfonate) to total S contained exclusively Fe(III) oxyhydroxides (probably ferrihydrite) as S‐bearing phase, whereas another microregion with a large contribution of reduced organic S (thiol, organic disulfide) to total S contained a small amount of Fe(II)‐bearing silicate in addition to the dominating Fe(III) oxyhydroxides. Our results show that combined S and Fe µ‐XANES is a powerful tool for studying microscale spatial patterns of S and Fe speciation as well as microscale relationships between the speciation of S and Fe in soil aggregates.     

Characterizing arsenic in preserved hair for assessing exposure potential and discriminating poisoning

Advanced analytical techniques have been used to characterize arsenic in taxidermy specimens. Arsenic was examined to aid in discriminating its use as a preservative from that incorporated by ingestion and hence indicate poisoning (in the case of historical figures). The results are relevant to museum curators, occupational and environmental exposure concerns, toxicological and anthropological investigations. Hair samples were obtained from six taxidermy specimens preserved with arsenic in the late 1800s and early 1900s to investigate the arsenic incorporation. The presence of arsenic poses a potential hazard in museum and private collections. For one sample, arsenic was confirmed to be present on the hair with time‐of‐flight secondary ion mass spectrometry and then measured with neutron activation analysis to comprise 176 µg g^?1. The hair cross section was analysed with synchrotron micro‐X‐ray fluorescence to investigate the transverse distribution of topically applied arsenic. It was found that the arsenic had significantly penetrated all hair samples. Association with melanin clusters and the medulla was observed. Lead and mercury were also identified in one sample. X‐ray absorption near‐edge spectroscopy of the As K‐edge indicated that an arsenate species predominantly existed in all samples; however, analysis was hindered by very rapid photoreduction of the arsenic. It would be difficult to discriminate arsenic consumption from topically applied arsenic based on the physical transverse distribution. Longitudinal distributions and chemical speciation may still allow differentiation.     

Development and exploration of a new methodology for the fitting and analysis of XAS data

A new data analysis methodology for X‐ray absorption near‐edge spectroscopy (XANES) is introduced and tested using several examples. The methodology has been implemented within the context of a new Matlab‐based program discussed in a companion related article [Delgado‐Jaime et al. (2010), J. Synchrotron Rad. 17 , 132–137]. The approach makes use of a Monte Carlo search method to seek appropriate starting points for a fit model, allowing for the generation of a large number of independent fits with minimal user‐induced bias. The applicability of this methodology is tested using various data sets on the Cl K‐edge XAS data for tetragonal CuCl₄^2?, a common reference compound used for calibration and covalency estimation in M—Cl bonds. A new background model function that effectively blends together background profiles with spectral features is an important component of the discussed methodology. The development of a robust evaluation function to fit multiple‐edge data is discussed and the implications regarding standard approaches to data analysis are discussed and explored within these examples.     

X‐ray spectroscopy for chemistry in the 2‐4 keV energy regime at the XMaS beamline: ionic liquids,Rh and Pd catalysts in gas and liquid environments,and Cl contamination in γ‐Al2O3

The 2–4 keV energy range provides a rich window into many facets of materials science and chemistry. Within this window, P, S, Cl, K and Ca K‐edges may be found along with the L‐edges of industrially important elements from Y through to Sn. Yet, compared with those that cater for energies above ca. 4–5 keV, there are relatively few resources available for X‐ray spectroscopy below these energies. In addition, in situ or operando studies become to varying degrees more challenging than at higher X‐ray energies due to restrictions imposed by the lower energies of the X‐rays upon the design and construction of appropriate sample environments. The XMaS beamline at the ESRF has recently made efforts to extend its operational energy range to include this softer end of the X‐ray spectrum. In this report the resulting performance of this resource for X‐ray spectroscopy is detailed with specific attention drawn to: understanding electrostatic and charge transfer effects at the S K‐edge in ionic liquids; quantification of dilution limits at the Cl K‐ and Rh L₃‐edges and structural equilibria in solution; in vacuum deposition and reduction of [Rh^I(CO)₂Cl]₂ to γ‐Al₂O₃; contamination of γ‐Al₂O₃ by Cl and its potential role in determining the chemical character of supported Rh catalysts; and the development of chlorinated Pd catalysts in `green' solvent systems. Sample environments thus far developed are also presented, characterized and their overall performance evaluated.     

The unoccupied electronic structure characterization of hydrothermally grown ThO2 single crystals

Single crystals of thorium dioxide ThO₂, grown by the hydrothermal growth technique, have been investigated by ultraviolet photoemission spectroscopy (UPS), inverse photoemission spectroscopy (IPES), and L₃, M₃, M₄, and M₅ X‐ray absorption near edge spectroscopy (XANES). The experimental band gap for large single crystals has been determined to be 6 eV to 7 eV, from UPS and IPES, in line with expectations. The combined UPS and IPES, place the Fermi level near the conduction band minimum, making these crystals n‐type, with extensive band tailing, suggesting an optical gap in the region of 4.8 eV for excitations from occupied to unoccupied edge states. Hybridization between the Th 6d/5f bands with O 2p is strongly implicated. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

An attempt to analyze the bark disease in Havea brasiliensis using X‐ray absorption near‐edge spectroscopy

The X‐ray absorption near‐edge spectroscopy (XANES) technique has been used to determine the chemical change of elements induced by bark diseases in Havea brasiliensis (rubber latex tree). The results show the good sensitivity of in situ XANES for characterizing the chemical structure of phosphorus, sulfur, potassium and calcium in healthy and diseased Havea brasiliensis. Important information for understanding the bark disease involved in the sulfur metabolism of plants was also obtained from XANES.     

Nature of chemical states of sulfur embedded in atomic‐layer‐deposited HfO2 film on Ge substrate for interface passivation

Sulfur was embedded in atomic‐layer‐deposited (ALD) HfO₂ films grown on Ge substrate by annealing under H₂S gas before and after HfO₂ ALD. The chemical states of sulfur in the film were examined by S K‐edge X‐ray absorption spectroscopy. It was revealed that the valences of S‐ions were mostly –2 at Ge/HfO₂ interface (GeS_x or HfO_2–yS_y to passivate the interface), while they were mostly +6 in HfO₂ layers (sulfates; HfO_2–z(SO₄)_z). The leakage current density in post‐deposi‐tion‐treated film was lower than that in pre‐deposition‐treated one. This suggests that the passivation of defects in oxide layer by sulfate ions is more effective to lower the leakage current rather than the interface defect passivation by S^2– ions. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Characterisation of Sonochemically Produced PdO Nanoparticles by X‐ray Absorption Near Edge Structure Spectroscopy

Brij‐35 [polyoxyethylene(23) lauryl ether] stabilised palladium nanoparticles, obtained on attempted sonochemical reduction of PdCl₂ by sodium sulfite in water under Argon, instantaneously oxidized to PdO. The particles obtained were stable and have narrow size distribution with an average size of 10 nm diameter. PdO nanoparticles were reduced to Pd nanoparticles in an autoclave by treatment with 50 bar hydrogen at 140 °C. The catalytic behaviour of Pd nanoparticles, thus obtained, is unusual in comparison with conventional Pd catalysts. The nanoparticles were characterized by UV‐Vis spectroscopy, TEM and their X‐ray Absorption Near Edge Structure (XANES) at the Pd‐L‐III edge.     

X‐Treme beamline at SLS: X‐ray magnetic circular and linear dichroism at high field and low temperature

X‐Treme is a soft X‐ray beamline recently built in the Swiss Light Source at the Paul Scherrer Institut in collaboration with École Polytechnique Fédérale de Lausanne. The beamline is dedicated to polarization‐dependent X‐ray absorption spectroscopy at high magnetic fields and low temperature. The source is an elliptically polarizing undulator. The end‐station has a superconducting 7 T–2 T vector magnet, with sample temperature down to 2 K and is equipped with an in situ sample preparation system for surface science. The beamline commissioning measurements, which show a resolving power of 8000 and a maximum flux at the sample of 4.7 × 10¹² photons s^?1, are presented. Scientific examples showing X‐ray magnetic circular and X‐ray magnetic linear dichroism measurements are also presented.     

Suppression of the Verwey Transition by Charge Trapping

The Verwey transition in Fe₃O₄ nanoparticles with a mean diameter of 6.3 nm is suppressed after capping the particles with a 3.5 nm thick shell of SiO₂. By X‐ray absorption spectroscopy and its associated X‐ray magnetic circular dichroism this suppression can be correlated to localized Fe²⁺ states and a reduced double exchange visible in different site‐specific magnetization behavior in high magnetic fields. The results are discussed in terms of charge trapping at defects in the Fe₃O₄/ SiO₂ interface and the consequent difficulties in the formation of the common phases of Fe₃O₄. By comparison to X‐ray absorption spectra of bare Fe₃O₄ nanoparticles in course of the Verwey transition, particular changes in the spectral shape could be correlated to changes in the number of unoccupied d states for Fe ions at different lattice sites. These findings are supported by density functional theory calculations.     

Solid‐phase cadmium speciation in soil using L3‐edge XANES spectroscopy with partial least‐squares regression

Cadmium (Cd) has a high toxicity and resolving its speciation in soil is challenging but essential for estimating the environmental risk. In this study partial least‐square (PLS) regression was tested for its capability to deconvolute Cd L₃‐edge X‐ray absorption near‐edge structure (XANES) spectra of multi‐compound mixtures. For this, a library of Cd reference compound spectra and a spectrum of a soil sample were acquired. A good coefficient of determination (R²) of Cd compounds in mixtures was obtained for the PLS model using binary and ternary mixtures of various Cd reference compounds proving the validity of this approach. In order to describe complex systems like soil, multi‐compound mixtures of a variety of Cd compounds must be included in the PLS model. The obtained PLS regression model was then applied to a highly Cd‐contaminated soil revealing Cd₃(PO₄)₂ (36.1%), Cd(NO₃)₂·4H₂O (24.5%), Cd(OH)₂ (21.7%), CdCO₃ (17.1%) and CdCl₂ (0.4%). These preliminary results proved that PLS regression is a promising approach for a direct determination of Cd speciation in the solid phase of a soil sample.