Table of contents

This preface of the proceedings volume of the 16^th International Conference on X- ray Absorption Fine Structure (XAFS16) gives a glance on the five days of cutting-edge X-ray science which were held in Karlsruhe, Germany, August 23 - 28, 2015. In addition, several satellite meetings took place in Hamburg, Berlin and Stuttgart, a Sino-German workshop, three data analysis tutorials as well as special symposia on industrial catalysis and XFELs were held at the conference venue.

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Depending on the material and edge under consideration, core level spectra manifest themselves as local excitons with multiplets, edge singularities, resonances, or the local projected density of states. Both extremes, i.e., local excitons and non-interacting delocalized excitations are theoretically well under control. Describing the intermediate regime, where local many body interactions and band-formation are equally important is a challenge. Here we discuss how Quanty, a versatile quantum many body script language, can be used to calculate a variety of different core level spectroscopy types on solids and molecules, both in the frequency as well as the time domain. The flexible nature of Quanty allows one to choose different approximations for different edges and materials. For example, using a newly developed method merging ideas from density renormalization group and quantum chemistry [1-3], Quanty can calculate excitons, resonances and band-excitations in x-ray absorption, photoemission, x-ray emission, fluorescence yield, non-resonant inelastic x-ray scattering, resonant inelastic x-ray scattering and many more spectroscopy types. Quanty can be obtained from: http://www.quanty.org.

GNXAS is a suite of programs based on multiple scattering calculations which performs a structural refinement of EXAFS spectra. It can be used for any system although it has been mainly developed to determine the local structure of disordered substances. We developed a user-friendly graphical user interface (GUI) to facilitate use of the codes by using wxPython. The developed GUI and the codes are multiplatform running on Windows, Macintosh and Linux systems, and are free shareware (http://gnxas.unicam.it). In this work we illustrate features and potentials of this newly developed version of GNXAS (w-GNXAS).

The influence of hydrogen intercalation on the local structure of rhenium trioxide is studied in-situ by the Re L₃-edge EXAFS spectroscopy and analysed using a novel approach, based on the use of evolutionary algorithm and wavelet transform. The proposed method allows us to perform accurate EXAFS analysis within the multiple-scattering approach taking into account contributions from outer coordination shells and to access the information on correlations in atomic thermal motion.

Finite difference method (FDM) implemented in the FDMNES software [Phys. Rev. B, 2001, 63, 125120] was revised. Thorough analysis shows, that the calculated diagonal in the FDM matrix consists of about 96% zero elements. Thus a sparse solver would be more suitable for the problem instead of traditional Gaussian elimination for the diagonal neighbourhood. We have tried several iterative sparse solvers and the direct one MUMPS solver with METIS ordering turned out to be the best. Compared to the Gaussian solver present method is up to 40 times faster and allows XANES simulations for complex systems already on personal computers. We show applicability of the software for metal-organic [Fe(bpy)₃]²⁺ complex both for low spin and high spin states populated after laser excitation.

For Co-containing crystalline compounds measured by XAS, the influence of the local symmetry on the K pre-edge features is studied using advanced Ligand Field Multiplet (LFM) calculations, which accurately take into account the p-d hybridization. The LFM theory is used to calculate the K pre-edge spectra of Co²⁺ in various environments and the absolute intensities of electric-quadrupole and -dipole transitions involved in the pre-edge. This enables to reproduce the spectra for cubic (O_h, T_d) and lower symmetries (C_4v, D_3h), and allows quantitative derivation of the local p-d mixing.

Usually first-principles x-ray absorption near-edge structure (XANES) calculations are performed in the Born-Oppenheimer approximation assuming a static lattice, whereas the nuclear motion undoubtedly impacts XANES spectra notably at the K pre-edge of light elements in oxides. Here, an efficient method based on density-functional theory to account for quantum thermal fluctuations of nuclei is developed and is successfully applied to the K edge of corundum for temperatures up to 930 K. The zero-point motion influence is estimated. Comparison is made with previous theoretical approaches also developed to account for vibrations in XANES.

X-ray absorption calculations of Ca L₂₃-edge spectra of calcium carbonate in its two main crystal phases, calcite and aragonite, are reported. The multichannel multiple scattering theory with a correlated particle-hole wave function and a partially screened core-hole potential is used. Very good agreement with experiment for both CaCO₃ phases is obtained, while the independent particle approximation completely fails. For aragonite, appreciable linear dichroism is predicted in agreement with recent observations.

We present a new implementation of the XAFSmass program that calculates the optimal mass of XAFS samples. It has several improvements as compared to the old Windows based program XAFSmass: 1) it is truly platform independent, as provided by Python language, 2) it has an improved parser of chemical formulas that enables parentheses and nested inclusion-to-matrix weight percentages. The program calculates the absorption edge height given the total optical thickness, operates with differently determined sample amounts (mass, pressure, density or sample area) depending on the aggregate state of the sample and solves the inverse problem of finding the elemental composition given the experimental absorption edge jump and the chemical formula.

Scandium fluoride ScF₃ has a simple cubic structure and attracts attention due to its large negative thermal expansion (NTE) over a wide range of temperatures (0-1100 K). In this study we present ab initio molecular dynamics (AIMD) simulations of ScF₃ and their validation using the Sc K-edge EXAFS spectra in the temperature range from 300 K to 1000 K measured at the XAFS beamline of ELETTRA. The obtained results allow an assessement of the employed AIMD model and provide insight into the local structure and the lattice dynamics of ScF₃ beyond the harmonic approximation. A strong anisotropy of the fluorine atom vibrations in the direction orthogonal to the -Sc-F-Sc- chain is observed. An expansion of the ScF₆ octahedra is found upon increasing temperature despite of the overall NTE of the crystal.

The effects of the spin-orbit interaction on surrounding atoms for XMCD spectra are studied by a real-space multiple-scattering theory. The present numerical calculation for Fe K-edge XMCD spectra from BCC iron demonstrates the importance of the spin-orbit interaction on scattering atoms, which has been disregarded in previous works. These effects will be inevitable for K-edge XMCD analyses of light elements surrounded by heavy magnetic atoms.

Zinc chromite ZnCr₂O₄ has been investigated by X-ray absorption near edge structure (XANES) spectroscopy at the Cr K-edge, with the objective of better understanding the origin of the electronic excitations giving rise to the pre-edge features. In particular, the origin of a third feature visible only in Cr-rich compounds of the ZnAl₂O₄-ZnCr₂O₄ solid solution is studied. Standard density functional theory (DFT) XANES calculations were first performed, then a Hubbard U parameter was included in an attempt to improve the relative peak positions by increasing the localization of the Cr 3d states. The origin of the pre-edge features in ZnCr₂O₄ has been analyzed using DFT+U calculations, local projected densities of states and the assignment of the spectral features for the dilute ZnAl₂O₄:Cr³+ compound. We show that DFT+U does not overcome the limitations of standard DFT in modeling the relative peak positions, and that approaches including advanced description of the electron-hole interaction are needed.

The software PrestoPronto consist to a full graphical user interface (GUI) program aimed to execute the analysis of large X-ray Absorption Spectroscopy data sets. Written in Python is free and open source. The code is able to read large datasets, apply calibration, alignment corrections and perform classical data analysis, from the extraction of the signal to EXAFS fit. The package includes also programs with GUIs] to perform, Principal Component Analysis and Linear Combination Fits. The main benefit of this program is allow to follow quickly the evolution of time resolved experiments coming from Quick-EXAFS (QEXAFS) and dispersive EXAFS beamlines.

We propose an approach beyond the quasiharmonic approximation for interpretation of EXAFS and XRD data and for ab initio calculations of electronic and vibration properties of materials with negative thermal expansion. Ab initio electronic structure and lattice dynamics calculations for cubic and distorted ScF₃ were performed using the linear combination of atomic orbitals (LCAO) method. The band gap obtained in calculations for ScF₃ is equal to 10.54 eV and agree well with the expected value. The calculated infrared spectra of F displaced (FD) cubic ScF₃ allow us to predict that its mean Sc-F-Sc angle within NTE deviates from 180 degree.

An efficient referencing and sample positioning system is a basic tool for a micro focus beamline at a synchrotron. The seven years ago introduced command line based system was upgraded at SUL-X beamline at ANKA [1]. A new combination of current server client techniques offers direct control and facilitates unexperienced users the handling of this frequently used tool.

We have recently demonstrated a very favorable, inexpensive modernization of lab- based x-ray absorption fine structure (XAFS) and high-resolution x-ray emission spectroscopy (XES) using only commercially-available optics and x-ray tube sources. Here, we survey several proven instrument designs that can be readily implemented in any laboratory setting to achieve synchrotron-quality XAFS and XES for many systems in the 5 keV to 10 keV energy range. These approaches are based on our immediate experience with the development of: (1) an inexpensive, low-powered monochromator capable of performing either XAFS or XES, (2) a mid-scale XAFS user facility having 10⁶/sec flux with sub-eV bandwidth on each of two independent beamlines, and (3) multiple XES spectrometers having outstanding performance that can complement synchrotron XAFS studies in battery and actinide research.

X-ray absorption spectroscopy on dilute samples is still a challenge nowadays. By means of the fluorescence processes that follow the absorption it is possible to obtain the XAS spectrum; however, in order to gain sufficient statistics a multi-pixel fluorescence detector is required. A 100 pixel Ge detector will be available at beamline P64 at PETRA III for ultra dilute sample systems. Here, we propose a method of data reduction that resolves the line of interest from the scattering peak, improving the signal-to-noise ratio of the final XAS spectrum compared with the one obtained with a simple region of interest (ROI).

XAFS-experiments in transmission and reflection modes have been performed using a Pilatus 100K pixel detector. Transmission mode XAFS spectra from a Co metal foil and Co₃O₄ were recorded to evaluate the data quality offered by this 2D-detector. Furthermore, the pixel detector was also used to measure reflection mode grazing incidence EXAFS data. Using different regions of interest in the collected scattering patterns, we will show that the diffuse scattering can be separated for the different contributing surfaces and interfaces, allowing simultaneous investigations of surfaces and buried interfaces within multi-layered samples.

The emission spectrometer at Balder/MAX IV beamline is presented. Its unique features are described. Comparison is given with other types of curved crystals analyzers.

A new hard X-ray beamline for CATalysis and ACTinide research has been built at the synchrotron radiation facility ANKA. The beamline design is dedicated to X-ray spectroscopy, including 'flux hungry' photon-in/photon-out and correlative techniques with a special infrastructure for radionuclide and catalysis research. The CAT-ACT beamline will help serve the growing need for high flux/hard X-ray spectroscopy in these communities. The design, the first spectra and the current status of this project are reported.

First fast EXAFS spectra have been successfully measured at the Hard X-ray Micro-probe Beamline P06 (PETRA III) synchronously scanning the U32 undulator gap and the monochromator Bragg axis. Stability and spatial homogeneity of the beam are proved to be the limiting factors for the quality of the EXAFS spectra, whereas the performance of the data acquisition electronics limits the energy resolution when total scan time is reduced to 30 seconds. Results of the test measurements give us the estimate of the utmost performance of 510 seconds per full EXAFS scan considering certain hardware modifications.

LISA is the acronym of Linea Italiana per la Spettroscopia di Assorbimento di raggi X (Italian beamline for X-ray Absorption Spectroscopy) and is the upgrade of the former GILDA beamline installed on the BM08 bending magnet port of European Synchrotron Radiation Facility (ESRF). Within this contribution a full description of the project is provided.

The XAFS2 is a general-purpose X-ray absorption beamline. It is the second one built at the LNLS. After approximately 7 years in operation this beamline has been substantially updated in order to improve its experimental possibilities. Recently arrived, a 4-circle Huber diffractometer has been incorporated to perform combined experiments. This collects XRD patterns with the XAFS. Through the development of a new sampling environment it is now also possible to perform these measurements in situ/operando conditions. Other upgrades include a complete remodelling of the beamline software and its control system. The following new systems are crucial for the next steps that are currently underway at the beamline, namely, (i) enabling remote access for users and (ii) the testing of QEXAFS measurements.

X-ray absorption spectroscopy (XAS) includes well-established methods to study the local structure around the absorbing element - extended X-ray absorption fine structure (EXAFS), and the effective oxidation number or to quantitatively determine the speciation of an element in a complex matrix - X-ray absorption near-edge structure (XANES). The increased brilliance and intensities available at the new generation of synchrotron light sources makes it possible to study, in-situ and in-operando, much more dilute systems with relevance for natural systems, as well as the micro-scale variability and dynamics of chemical reactions on the millisecond time-scale. The design of the BALDER beamline at the MAX IV Laboratory 3 GeV ring has focused on a high flux of photons in a wide energy range, 2.4-40 keV, where the K-edge is covered for the elements S to La, and the L₃-edge for all elements heavier than Sb. The overall design of the beamline will allow large flexibility in energy range, beam size and data collection time. The other focus of the beamline design is the possibility to perform multi-technique analyses on samples. Development of sample environment requires focus on implementation of auxiliary methods in such a way that techniques like Fourier transform infrared (FTIR) spectroscopy, UV-Raman spectroscopy, X-ray diffraction and/or mass spectrometry can be performed simultaneously as the XAS study. It will be a flexible system where different instruments can be plugged in and out depending on the needs for the particular investigation. Many research areas will benefit from the properties of the wiggler based light source and the capabilities to perform in-situ and in-operando measurements, for example environmental and geochemical sciences, nuclear chemistry, catalysis, materials sciences, and cultural heritage.

The development of the next generation synchrotron radiation sources - free electron lasers - is approaching to become an effective tool for the time-resolved experiments aimed to solve actual problems in various fields such as chemistry' biology' medicine' etc. In order to demonstrate' how these experiments may be performed for the real systems to obtain information at the atomic and macromolecular levels' we have performed a molecular dynamics computer simulation combined with quantum chemistry calculations for the human phosphoglycerate kinase enzyme with Mg containing substrate. The simulated structures were used to calculate coherent X-ray diffraction patterns' reflecting the conformational state of the enzyme, and Mg K-edge X-ray absorption spectra, which depend on the local structure of the substrate. These two techniques give complementary information making such an approach highly effective for time-resolved investigation of various biological complexes, such as metalloproteins or enzymes with metal-containing substrate, to obtain information about both metal-containing active site or substrate and the atomic structure of each conformation.

A highly stable Bragg polychromator for energy dispersive XAFS (DXAFS) systems was developed at the bending magnet beamline BL28B2 at SPring-8. The bending device is a four-point-type bender. Additional stoppers for the crystal are attached at both ends of the bender to maintain the position and curvature of the crystal in the bender. The crystal was indirectly cooled in a copper grain bath with good thermal contact, the temperature of which was precisely controlled using water cooling. A performance test of stability of the new Bragg polychromator showed that the energy drift in the DXAFS spectra was reduced to less than 0.01 eV for 2 hrs.

The layout and the characteristics of the hard X-ray beamline BL 10 at the superconducting asymmetric wiggler at the 1.5 GeV Dortmund Electron Accelerator DELTA are described. Equipped with a stable and robust Si(111) channel-cut monochromator, this beamline is suited for XAFS studies in the spectral range from about 4 keV to ca. 16 keV photon energy. We will illustrate the performance of the beamline, and present EXAFS data obtained from several reference compounds. XANES data measured for dilute sample systems as well as surface sensitive grazing incidence EXAFS obtained from thin film samples will also be discussed.

A XAFS beamline, BL5S1, had been operated at Aichi Synchrotron Radiation Center, Japan since March 2013. The beamline was designed for the measurements in the energy range from 5 to 20 keV. The photon flux of 6 x 10¹⁰ at around 9 keV and beam spot size of 0.5 x 0.3 mm at sample position are as good as designed. For the standard transmission XAFS measurement, both of the step- and quick- scan modes are available. Energy resolution at around 9keV is good enough to discuss the energy shift of the order of 0.1 eV or higher even when the measurements are conducted in the quick-scan mode. With several kinds of detectors for fluorescence and/or CEY detection mode measurements, and various kinds of sample holders which are supported by the XAFS measurement software, users easily obtain spectra for their samples. Such a standard, well operated and easy to access XAFS beamline must be very important to broaden the base of the XAFS society further.

ReflXAFS is a well-known, surface sensitive method to investigate the structure of e.g. thin films. By a proper choice of incident and exit angles the Yoneda-peak, a distinct intensity maximum in the diffuse scattering, becomes visible. For multilayered samples, several Yoneda-peaks related to surface and interface regions may be observed. It is possible to utilize these peaks to measure the fine structure of an element inside the related surface and interface regions of a multi-layered sample. We will show that the use of 2D-area detectors allow the simultaneous measurement of the entire scattering pattern for each energy in an EXAFS spectrum, providing access to detailed in-situ structure information of the surface and interface regions in multilayered samples.

Acetyl-CoA synthase (ACS) is involved in the bacterial carbon oxide conversion pathway. The binuclear nickel sites in ACS enzyme and two biomimetic synthetic compounds containing a Ni(II)Ni(II) unit (1 and 2) were compared using XAS/XES. EXAFS analysis of ACS proteins revealed similar Ni-N/O/S bond lengths and Ni-Ni/Fe distances as in the crystal structure in oxidized ACS, but elongated Ni-ligand bonds in reduced ACS, suggesting more reduced nickel species. The XANES spectra of ACS and the dinickel complexes showed overall similar shapes, but less resolved pre-edge and edge features in ACS, attributed to more distorted square-planar nickel sites in particular in reduced ACS. DFT calculation of pre-edge absorption and Kβ_2,5 emission features reproduced the experimental spectra of the synthetic complexes, was sensitive even to the small geometry differences in 1 and 2, and indicated low-spin Ni(II) sites. Comparison of nickel sites in proteins and biomimetic compounds is valuable for deducing structural and electronic differences in response to ligation and redox changes.

Selective catalytic reduction of NO_x by ammonia over Cu-ZSM-5 was monitored by operando QEXAFS during simulation of the New European Driving Cycle. The required fast temperature transients were realized using a novel silicon microreactor, enabling simultaneous spectroscopic and kinetic analysis by X-ray absorption spectroscopy (XAS) and mass spectrometry (MS). Periods of high temperature were correlated to an increase in both N₂ production and change of coordination of Cu sites. This operando approach using Si microreactors can be applied to other heterogeneous catalytic systems involving fast temperature transients.

Reflectivity measurements on graphitic materials such as graphene at energies across the carbon K-edge are frustrated by significant intensity loss due to adventitious carbon on beamline mirrors. Such intensity reduction enhances effects due to perturbing high-order harmonics in the beam. These effects distort the actual structure of the reflectance curve. In order to overcome this limitation, a correction technique has been developed and demonstrated first with measurements for highly ordered pyrolytic graphite. The same approach may be applied to other graphitic materials such as graphene and it may be used with other synchrotron beamlines. The fraction of high-order harmonics was determined by passing the incident beam through a 87 nm thin silicon nitride absorber that can be well modeled. Using the corrected measurements the x-ray natural linear dichroism of the sample has been determined.

In the current work we present a detailed analysis of the hydride phase formation in industrial Pd/C nanocatalysts by means of combined in situ X-ray absorption spectroscopy (EXAFS), X-ray diffraction (XRD) and volumetric measurements for the temperatures from - 10 to 50 °C in the hydrogen pressure range from 0 to 1000 mbar. α- and β- hydride phases are clearly distinguished in XRD. For the first time, H/Pd atomic ratio were obtained by theoretical fitting of the near-edge region of the absorption spectra (XANES) and compared with volumetric measurements.

A depth-resolved X-ray magnetic circular dichroism (XMCD) technique has been developed in the soft X-ray region by combining a multi-anode microchannel plate detector with polarization switching between right and left circular polarizations. A simultaneous measurement for 30-channel anodes has been achieved with a continuous data acquisition rate of 1 kHz, which is fast enough for 10 Hz polarization switching. This enables us to realize the layer-resolved XMCD analysis with a high signal-to-noise ratio.

NEXAFS-RIXS and home laboratory-based UV-Vis absorption spectroscopy are combined to examine the speciation and electronic structure of para-aminobenzoic acid (PABA) in aqueous solution as a function of pH. DFT and TD-DFT electronic structure calculations reproduce the experimental trends and provide a correlation between the experimental HOMO↔LUMO gap as well as the electronic transitions between molecular orbitals in the non-ionic, anionic and cationic forms of PABA.

Understanding the formation mechanism of gold nanoclusters is essential to the development of their synthetic chemistry. Here, by using x-ray absorption fine-structure (XAFS) spectroscopy, UV-Vis and MS spectra, the formation process of monodisperse Au₁₃ nanoclusters is investigated. We find that a critical step involving the formation of smaller Au₈-Au₁₁ metastable intermediate clusters induced by the HCl + HSR etching of the polydisperse Au_n precursor clusters occurs firstly. Then these intermediate species undergo a size-growth to Au₁₃ cores, followed by a slow structure rearrangement to reach the final stable structure. This work enriches the understanding of cluster formation chemistry and may guide the way towards the design and the controllable synthesis of nanoclusters.

Recently developed instrumentation at the University of Washington has allowed for nonresonant x-ray emission spectra (XES) to be measured in a laboratory-setting with an inexpensive, easily operated system. We present a critical evaluation of this equipment by means of Kβ and valence-level XES measurements for several Co compounds. We find peak count rates of ∼5000/s for concentrated samples and a robust relative energy scale with reproducibility of 25 meV or better. We furthermore find excellent agreement with synchrotron measurements with only modest loss in energy resolution. Instruments such as ours, based on only conventional sources that are widely sold for elemental analysis by x-ray fluorescence, can fill an important role to diversify the research applications of XES both by their presence in non-synchrotron laboratories and by their use in conjunction with XAFS beamlines where the complementarity of XAFS and XES holds high scientific potential.

It is shown that the regularization method with two kernels can resolve the double shells of different kinds of atomic species. The method was tested for simulated and experimental spectra. In both works, it provided successful results in separation of the double shells of different atoms.

The nature of local point symmetry in simple monoatomic liquids has been a fundamental open question for almost 40 years of computational and experimental studies. We present original results of local ordering in different monoatomic liquids obtained by x-ray absorption spectroscopy (XAS), exploiting its high sensitivity to short-range ordering. We used Reverse Monte Carlo (RMC) analysis (RMC-GNXAS package) for obtaining structural models compatible with XAS experimental data (and diffraction techniques for long-range ordering). Pair, bond-angle distributions and suitable indicators for point symmetry are calculated for different liquid metals.

Simultaneous time-resolved SAXS and XANES techniques were employed to follow in situ the formation of Pd nanoparticles from palladium acetate precursor in two porous polymeric supports: polystyrene (PS) and poly(4-vinyl-pyridine) (P4VP). In this study we have investigated the effect of the use of different reducing agents (H₂ and CO) from the gas phase. These results, in conjunction with data obtained by diffuse reflectance IR (DRIFT) spectroscopy and TEM measurements, allowed us to unravel the different roles played by gaseous H₂ and CO in the formation of the Pd nanoparticles for both PS and P4VP hosting scaffolds.

Structure of acetic acid (AA) and methyl formate (MF) in the liquid phase is studied using X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) experimentally and theoretically. Two distinct XES spectra are observed by tuning photon energy for both molecules. Model structure in the liquid phase is constructed using the classical and first principle molecular dynamics simulations, and XES spectra are calculated using density functional theory. Calculated XES spectra are consistent with experimental ones. The effect of core-hole induced excited state molecular dynamics are discussed.

Cu-SSZ-13 is a highly active catalyst for the NH₃-assisted selective catalytic reduction (SCR) of the harmful nitrogen oxides (NO_x, x=1, 2). Since the catalytically active sites for this reaction are mainly represented by isolated Cu ions incorporated into the zeolitic framework, element-selective studies of Cu local environment are crucial to fully understand the enhanced catalytic properties of this material. Herein, we highlight the recent advances in the characterization of the most abundant Cu-sites in Cu-SSZ-13 upon different reaction-relevant conditions made employing XAS and XES spectroscopies, complemented by computational analysis. A concise review of the most relevant literature is also presented.

We have studied surface structural change of supported Pd metal nanoparticles caused by CO adsorption and following temperature increase by using in situ and time-resolved X- ray absorption fine structure technique with dispersive optics. CO adsorption on Pd metal nanoparticles at room temperature shows two types of adsorption behavior and the less stable CO which brings about surface expansion of Pd metal nanoparticles is desorbed just after temperature increase. Pd carbide layer is created at around 350 °C by CO decomposition, which was clearly detected by the elongation of Pd-Pd interatomic distance and the increase of Debye-Waller factor and third cumulant.

Reduction process of Pd-containing La-Fe perovskites was investigated by in-situ Pd K-edge dispersive X-ray absorption fine structure as well as mass spectroscopy. The prepared perovskite was characterized by a conventional X-ray absorption spectra to confirm the incorporation of cationic Pd into perovskite matrix. Under the reductive atmosphere (5 vol%H₂/He), we found the presence of three reduction processes of Pd cations in perovskite structure. The segregation of Pd metal particles was observed from 200-400 ^oC although the cationic Pd species remained at 700 ^oC due to the strong metal-support interaction.

Changes of the geometric and electronic structure of gold on Au/CeO₂ catalysts induced by different pre-treatments (oxidative and reductive) and by the CO oxidation reaction at 80°C were followed by operando XANES / EXAFS measurements. The results showed that i) oxidative pre-treatment (O₂) leads to larger Au nanoparticles than reductive pre-treatment (CO), that ii) Au is predominantly metallic during CO oxidation, irrespective of the preceding pre-treatment, and that iii) there is a reaction induced Au particle growth. Correlations with the activity of the respective catalysts and its temporal evolution give insights into the origin of deactivation of these catalysts under reaction conditions, in particular on reaction induced changes in the Au particle size.

Combined X-ray absorption spectroscopy (XAS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were applied to investigate the interaction between reaction atmosphere, adsorbates and Pt oxidation state of Pt/Al₂O₃ model diesel oxidation catalysts under CO/NO oxidation conditions. The Pt oxidation state was correlated to the adsorbates on the catalyst's surface. Even at low temperature the reaction atmosphere had a strong impact on the oxidation state of the catalyst, and the oxidation state in turn strongly affected CO adsorption on the Pt particles.

Conducting Bridge Random Access Memories (CBRAM) are a promising substitute for FLASH technology but problems with limited retention of the low resistance ON state still hamper their massive deployment. Depth resolved X-ray Absorption Spectroscopy has been used to describe the chemical state of the atoms of the active electrode (in this case Ag) and to reveal the role of Sb as stabilizer of the metallic state.

Different thermal treatments were performed for the anti-oxidation of steel surfaces, and the processes were investigated ex-situ and in-situ by surface sensitive reflection mode EXAFS experiments at the Cr and Fe K-edges. While the samples for the ex-situ studies were heat-treated in a conveyor belt furnace at temperatures between 600 and 900 °C in inert carrier gases (N₂ or Ar) using different additives such as hydrogen (H₂) and monosilane (SiH₄), the in- situ anti-oxidation treatments have been performed in a high vacuum environment (p < 10^-6 mbar). While the ex-situ experiments suggest that SiH₄-additives are needed for the reduction of the steel to a metallic state, the in-vacuum treatments appear successful for temperatures above approx. 900 °C.

Nanocatalysts PtCu/C with different distribution of components in bimetallic PtCu nanoparticles (NPs) were synthesized by simultaneous and sequential deposition of Cu and Pt on carbon support. Electrochemical stability of the obtained samples PtCu/C was studied using the cyclic voltammetry. Characterization of atomic structure of as prepared PtCu NPs and obtained after acid treatment was performed by Pt L₃- and Cu K-edge EXAFS using the technique for determining local structure parameters of the absorbing atom under strong correlations among them. EXAFS derived parameters were used for generation of structural models of PtCu NPs by the method of cluster simulations. Within this approach, the models of atomic structure of PtCu NPs obtained by the two methods of synthesis, before and after post treatment and after two months from their preparation were revealed.

Time resolved oxidation and reduction cycles of ZrO₂-supported Ni catalysts for dry reforming of CH₄ (CO₂ + CH₄ ↔ 2 CO + 2 H₂) during feed modulations have been studied. Under reaction conditions (1073 K) Ni remains fully reduced, whereas switching the feed gas to pure CO₂ results in a slow (25 sec) formation of a stable NiO phase. When switching back to reaction conditions the NiO phase is rapidly reduced (∼ 1 sec) to metallic Ni. In the context of this study, a novel capillary cell has been built, allowing the parallel treatment of 5 catalyst samples with different gas compositions and different pressures. A comparison of the capillary cell to conventional systems regarding the spectral quality and the kinetic data shows that the capillary cell can be used to obtain identical kinetic data and high quality X-ray absorption spectra.

A 10 wt.-% Ni/Al₂O₃ catalyst with Ni particles of about 4 nm was prepared and applied in the methanation of CO₂ under dynamic reaction conditions. Fast phase transformations between metallic Ni, NiO and NiCO₃ were observed under changing reaction atmospheres using operando X-ray absorption spectroscopy (XAS). Removing H₂ from the feed gas and, thus, simulating a H₂ dropout during the methanation reaction led to oxidation of the active sites. The initial reduced state of the Ni particles could not be recovered under methanation atmosphere (H₂/CO₂ = 4); this was only possible with an effective reactivation step applying H₂ at increased temperatures. Furthermore, the cycling of the gas atmospheres resulted in a steady deactivation of the catalyst. Operando XAS is a powerful tool to monitor these changes and the behavior of the catalyst under working conditions to improve the understanding of the catalytic processes and deactivation phenomena.

Methane oxidation on Pd/Al₂O3 has been investigated using operando X-ray absorption spectroscopy (XAS) at the Pd K-edge. The influence of CO and NO on methane abatement has been addressed performing temperature programmed reaction runs while recording simultaneously XANES spectra. During CO oxidation Pd is reduced while methane conversion is shifted to higher temperature. NO strongly inhibits both CO and CH₄ oxidation, despite the higher fraction of oxidized palladium.

Hybrid catalysts based on Iridium N-heterocyclic carbenes anchored to carbon nanotubes (CNT) have been studied by XAFS spectroscopy. Oxidation of CNT yields a large amount of functional groups, mainly hydroxyl groups at the walls and carboxylic groups at the tips, defects and edges. Different kinds of esterification reactions were performed to functionalize oxidized CNT with imidazolium salts. Then, the resulting products were reacted with an Ir organometallic compound to form hybrid catalysts efficient in hydrogen transfer processes. XANES spectroscopy agree with the presence of Ir(I) in these catalysts and the EXAFS spectra detected differences in the local structure of Ir atoms between the initial Ir organometallic compound and the Ir complexes anchored to the CNT. Our results confirm that the halide atom, present in the Ir precursor, was replaced by oxygen from -OH groups at the CNT wall in the first coordination shell of Ir. The lability of this group accounts for the good recyclability and the good efficiency shown by these hybrid catalysts.

We synthesized UiO-67 metal-organic-frameworks (MOFs) functionalized with different transition metals (Rh, Ir). Using EXAFS we verified that the synthesis has been successful. Furthermore, we observed the change of local environment while varying of metal site. XAS spectroscopy is the most informative technique to characterize these kind of materials and to study the local environment around the metal site.

Microreactor technology with high heat transfer in combination with stable catalysts is a very attractive approach for reactions involving major heat effects such as methane steam reforming and to some extent, also the high temperature water gas shift (WGS) reaction. For this study Rh/ceria catalysts and an ultrathin hydrogen selective membrane were characterized in situ in a microreactor specially designed for x-ray absorption spectroscopic measurements under WGS conditions. The results of these experiments can serve as a basis for further development of the catalysts and membranes.

Oxidation state, local and electronic structure as well as the surface morphology of a CuO_x nanocomposites were investigated. The research is focused on studying the relationships between surface morphology and structure of the inorganic component of the nanocomposites. The physico-chemical mechanisms of change in local and electronic structure, oxidation state and the surface morphology of nanocomposites in the interaction of metal oxide nanoparticles with different types of matrices were determined.

Ga₂O₃ loaded Al₂O₃ samples (Ga₂O₃/Al₂O₃) were prepared to change coordination structures around Ga atoms. Ga K-edge XANES spectra of the Ga₂O₃/Al₂O₃ samples showed two peaks assigned to Ga atoms having tetrahedral coordination structure (Ga(t)) and octahedral one (Ga(o)). Curve-fitting analysis of XANES spectra was carried out with a set of pseudo- Voight and arctangent functions, and the fractions of Ga(t) and Ga(o) were quantitatively estimated from the ratio of the peak areas. EXAFS curve-fitting analysis also evaluated the fractions of Ga(t) and Ga(o) and they were in good agreement with those obtained by XANES analysis. It was revealed that the fraction of Ga(t) increased with the decrease in the loading amount of Ga₂O₃ due to the interaction of Ga species with Al₂O₃. The fractions of Ga(t) and Ga(o) might relate to the photocatalytic activity for CO₂ reduction with H₂O over the Ga₂O₃/Al₂O₃ samples.

Pd-Cu bimetallic Solvated Metal Atoms (SMA) were synthesized by metal vapor synthesis technique and supported on PVPy resin. Since the catalytic activity, of the Pd-Cu system turned out to be quite high also compared to the corresponding monometallic system, a structural characterization, using electron microscopy techniques and X-ray Absorption Fine Structure spectroscopy, was performed. HRTEM analysis showed the presence of Pd particles distributed in a narrow range with a mean diameter of about 2.5 nm while the XAFS analysis, confirmed the presence of the Pd nanoparticles but revealed also some alloying with Cu atoms.

Energy dispersive extended X-ray absorption fine structure (EDE) has been applied to Pd nanoparticle nucleation at a liquid/liquid interface under control over the interfacial potential and thereby the driving force for nucleation. Preliminary analysis focusing on Pd K edge-step height determination shows that under supersaturated conditions the concentration of Pd near the interface fluctuate over a period of several hours, likely due to the continuous formation and dissolution of sub-critical nuclei. Open circuit potential measurements conducted ex-situ in a liquid/liquid electrochemical cell support this view, showing that the fluctuations in Pd concentration are also visible as variations in potential across the liquid/liquid interface. By decreasing the interfacial potential through inclusion of a common ion (tetraethylammonium, TEA⁺) the Pd nanoparticle growth rate could be slowed down, resulting in a smooth nucleation process. Eventually, when the TEA⁺ ions reached an equilibrium potential, Pd nucleation and particle growth were inhibited.

Results of iridium L₃ edge EXAFS measurements of compounds relevant for water oxidation catalysis are compared to those of other structural techniques. The structural results from EXAFS for the Ir compounds investigated here compare well to those of other structural techniques. Multiple scattering contributions are important in the coordinated Cp* and NHC ligands as well as in the IrCl₆ unit and the IrO₂ rutile structure. NHC is relatively weak compared to Ir, Cl, and even Cp* and O, and often out of phase with the other contributions.

Mesoporous silica SBA-15 supported NbC catalysts were prepared under reduced pressure of CH₄-H₂ gas in a closed circulating system. Nb K- and L₃-edges XAFS measurements revealed that small NbC cluster formed on SBA-15 support and gradual carburization process by lengthening the carburization temperature-maintaining period. Carburization degree of Nb species was clearly explained by using threshold energy shift of Nb L₃-edge XANES profile.

The chemical state conversion of the Co species supported on SiO₂ was investigated using the in-situ and the time-resolved XAFS techniques. The supported Co₃O₄ species was finally reduced to metallic Co with the stable intermediate state of CoO for both the temperature-programmed and time-course processes. The oxidation of Co⁰ traced the reverse route to Co₃O₄, whereas the relative stability of the Co₃O₄ species to the CoO intermediate under the oxidative environment diminished the composition of CoO. The time-resolved measurement for the oxidation reaction showed an additional intermediate at the early stage of the CoO intermediate formation suggesting the Co⁰ particle dispersion.

Double metal cyanide (DMC) catalysts are commonly applied at industrial ring opening polymerization of epoxides. Nevertheless, the knowledge on the molecular nature of their high activity and selectivity is limited. XAS studies were performed to look for the possible catalytic centre in this family of catalysts. DMC catalysts were synthesized from ZnCl₂ and potassium hexacyanocobaltate(III) solution, in the presence of the different organic ligands and show significant fraction of the non-crystalline structure. Two ligands were analysed (tert-butanol (^tBuOH) or glyme (CH₃OCH₂CH₂OCH₃)). EXAFS analysis established that only Zn atoms are the active metallic centers in DMC regardless the used ligand. The coordination around Zn was changed from octahedral in reference non catalytic material to tetrahedral in catalysts, and Cl atoms were detected near some of Zn atoms.

Characterizing size related thermal properties of nanoclusters is challenging due to the requirement to accurately control both their average sizes and the size distributions. In this work, temperature-dependent Extended X-ray Absorption Fine Structure spectroscopy and the phenomenological bond-order-length-strength (BOLS) model were employed to investigate the size-dependent Einstein temperature of Au nanoclusters. Theoretical calculations of Einstein temperature and average bond distance for clusters with different sizes agree quantitatively with experiment. The BOLS model is thus useful for predictive understanding of structure and thermal properties in well-defined metal clusters.

A peculiar property of ceria is the ease to form oxygen vacancies, producing reactive sites or facilitating ionic diffusion. For these reasons ceria promotes catalytic activities for a number of important reactions when it is used as a support for transition metals. In our work we study the temporal evolution of oxygen vacancies formation by time-resolved XANES at Ce K- edge and XRD measurements on CeO₂/Pt nanoparticles, successfully monitoring the reaction of CO oxidation.

Rh/ceria catalysts were synthesized by flame spray pyrolysis for high temperature water gas shift (WGS) reactions. These catalysts show a high specific surface area due to a high degree of nanocrystallinity. X-ray absorption spectroscopy (XAS) unraveled the formation of small Rh particles under WGS reaction conditions. The catalytic activity was examined at atmospheric pressure by measuring CO conversion as a function of temperature. Some methane formation was observed above 310°C.

Understanding the influence of thiol on nanoparticle size and structure is essential for the fundamental and applied researches. Here, using x-ray absorption fine structure (XAFS) spectroscopy, we investigate the structural order of Au nanoparticles (NPs) in the protection of thiol ligands with different contents. We found that besides protecting Au NPs against aggregation and growth, thiolates can effectively eliminate the dangling bonds of unsaturated Au atoms, and thus increase the structural order. This work enriches our knowledge of Au-S interface interaction and guides the way towards preparing size-controllable nanoparticles with specific physical/chemical properties.

Local coordination environments around Pd and Pt in a Pd-core Pt-shell nanoparticle (NP) at temperatures ranging from 473 to 873 K was evaluated by utilizing in situ XAFS measurement technique to investigate the temperature range in which a core-shell structure is preserved. The core-shell structure was considered to be kept up to 673 K and start to change at about 773 K. Heating to 873 K accelerated atomic mixing in the core-shell NPs. Catalytic properties of the present Pd-core Pt-shell NP are available in the stoichiometric C₃H₆-O₂ atmosphere at temperatures less than 773 K at most.

Polydimethylsiloxane (PDMS) has proven to be a suitable embedding medium for silver clusters to prevent aggregation. In order to investigate the influence of the PDMS on the electronic and local atomic structure of the clusters the measurement of x-ray absorption near edge structure (XANES) spectra for different coverages of silver clusters in PDMS and calculations of corresponding XANES spectra have been performed. The coalescence process and the cluster-PDMS interaction were investigated with XANES.

NiO nanocluster catalysts were prepared on a SiO₂ support. Ni K-edge XAFS analysis revealed that the combined structure of NiO and Ni-silicate formed by using [Ni(NH₃)₆]²⁺ as a precursor, whereas pure NiO formed by using Ni-acetylacetonate or Ni- nitrate as a precursor. The obtained NiO nanocluster on Ni-silicate showed the catalytic activity for the oxidative coupling of thiophenol under air atmosphere. The combined structure of NiO and Ni-silicate showed the higher activity than pure NiO nanocluster did.

With the advent of high-throughput and imaging core level spectroscopies (including X-ray absorption spectroscopy, XAS, as well as electron energy loss spectroscopy, EELS), automated data processing, visualisation and analytics will become a necessity. As a first step towards these objectives we examined the possibilities and limitations of a simple automated XANES peak fitting procedure written in MATLAB, for the parametrisation of XANES features, including ionisation potentials as well as the energies and intensities of electronic transitions. Using a series of Au L₃-edge XANES reference spectra we show that most of the relevant information can be captured through a small number of rules applied to constrain the fits. Uncertainty in this strategy arises mostly when the ionisation potential (IP) overlaps with weak electronic transitions or features in the continuum beyond the IP, which can result in ambiguity through multiple equally good fits.

In this article, we demonstrate the potential of hard X-ray techniques to characterize catalysts under working conditions. Operando high energy resolution fluorescence detected (HERFD) XANES and valence to core (vtc) X-ray emission spectroscopy (XES) have been used in a spatially-resolved manner to study Cu-zeolite catalysts during the standard-SCR reaction and related model conditions. The results show a gradient in Cu oxidation state and coordination along the catalyst bed as the reactants are consumed. Vtc-XES gives complementary information on the direct adsorption of ammonia at the Cu sites. The structural information on the catalyst shows the suitability of X-ray techniques to understand catalytic reactions and to facilitate catalyst optimization.

A new setup with an integrated microfluidic chip with small dead time, high time resolution and compatibility with in situ X-ray absorption (XAS) measurements is presented. It can also be combined with a free liquid jet. By using the microfluidic chip the short reaction times from 2 to 20 milliseconds can be observed, beyond that an external cyclone mixer for extended observation times was applied. The reduction of gold ions with tetrakis(hydroxy-methyl)phosphonium (THPC) has been investigated in the microfluidic setup to monitor this reaction yielding small gold nanoparticles, requiring preferentially a free liquid jet.

The catalytic performance is largely affected by the oxidation state of supported Cr species, and its control changes the activity of Cr catalysts and the selectivity of products. In this study, the calcination process of the supported Cr catalysts on γ-Al₂O₃ and SiO₂ was investigated by in-situ XAFS spectroscopy. The hydrate species was first supported by the impregnation method and was converted to CrO₃ via Cr₂O₃ during the calcination process on both supporting materials. It was found that the temperature to complete the oxidation from Cr₂O₃ to CrO₃ on SiO₂ was higher than that on γ-Al₂O₃. The similarity of the interatomic distance between the surface oxygen atoms of the intermediate Cr₂O₃ species to that of SiO₂ contributes to the stabilization of Cr₂O₃ on SiO₂ during the calcination process.

Ag loaded Ga₂O₃ (Ag/Ga₂O₃) shows photocatalytic activity for reduction of CO₂ with water. Ag L₃-edge XANES and K-edge EXAFS spectra were measured for various Ag/Ga₂O₃ samples, which suggested that structural and chemical states of Ag species varied with the loading amount of Ag and the preparation method. The Ag species were metallic Ag particles with an AgGaO₂-like interface structure in the sample with high loading amount of Ag while predominantly Ag metal clusters in the sample with low loading amount of Ag. The XANES feature just above the edge represented the interaction between the Ag species and the Ga₂O₃ surface, showing that the Ag metal clusters had more electrons in the d-orbitals by interacting with the Ga₂O₃ surface, which would contribute the high photocatalytic activity.

The oxidation property of SiO₂-supported small Ni particle has been studied by means of the in-situ XAFS method. The Ni particle with the average diameter of 4 nm supported on SiO₂ was prepared by the sol-gel method. The XANES spectrum of the small metallic Ni particle was clearly different from that of bulk Ni. The exposure of diluted O₂ gas at room temperature promoted the surface oxidation of Ni(0) particle. During the temperature programmed oxidation process, the supported Ni(0) particle was quantitatively oxidized to NiO, and the oxidation temperature was lower by ca. 200 °C than that of the SiO₂-supported Ni particle with the larger particle radius of 17 nm prepared by the impregnation method.

A photodeposition process of Pt metal particles on anatase TiO₂ in the aqueous solution of H₂PtCl₆ (precursor) and methanol (reductant) was studied using transmission electron microscopy, UV-vis spectroscopy and X-ray absorption fine structure spectroscopy. These analyses proposed the photodeposition mechanism of Pt on TiO₂ by the photogenerated electrons: the photo-assisted adsorption of Pt⁴⁺ complexes on TiO₂ through the ligand exchange at the initial stage, followed by the successive rapid reduction of Pt⁴⁺ to Pt⁰ to grow the Pt metal particles, which gives small and almost uniform size of Pt metal nanoparticles.

Iron-ore sinters constitute the major component of the iron-bearing burden in blast furnaces, and the mechanism of their reduction is one of the key processes in iron making. The heterogeneous reduction of sintered oxides was investigated by the combination of X-ray fluorescence and absorption fine structure, X-ray diffraction, and computed tomography. Two - dimensional mapping of the chemical states (CSs) was performed. The iron CSs Fe^III, Fe^II, and Fe⁰ exhibited a heterogeneous distribution in a reduced sinter. The reduction started near micro pores, at iron-oxide grains rather than calcium-ferrite ones. The heterogeneous reduction among grains in a sinter may cause the formation of micro cracks. These results provide fundamental insights into heterogeneous reduction schemes for iron-ore sinters.

We present XAFS data collected at the Hg L_III-edge for bacterial cells of Escherichia coli that have been exposed to 500 and 50 nano-molar Hg²⁺ in aqueous solution, which corresponds to ∼30 and ∼3μg Hg per g cells (wet weight). These concentrations are respectively 1 and 2 orders of magnitude lower than what has been previously reported for Hg-bacteria XAFS experiments. The cells were metabolically active while exposed to Hg(II), providing coordination information that can be directly compared to Hg(II) biouptake experiments. At these amounts of total dissolved metal, Hg(II) binds primarily to thiol moieties that are either present at the cell membrane or localized in the cytoplasm. We show that in this case the Hg binding environment is a mixture of 2- and 4-fold coordination to thiols. This information can be inferred from XANES spectra but the EXAFS provides a more quantitative answer.

X-ray absorption spectroscopy (XAS) and cadmium (Cd) isotherm experiments determine how Cd adsorbs to the surface of halophilic archaeon Halobacterium noricense. This archaeon, isolated from the Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico could be involved with the transport of toxic metals stored in the transuranic waste in the salt mine. The isotherm experiments show that adsorption is relatively constant across the tolerable pH range for H. noricense. The XAS results indicate that Cd adsorption occurs predominately via a sulfur site, most likely sulfhydryl, with the same site dominating all measured pH values.

Sediments from the basin of Jordan River are to some extent significantly contaminated by heavy metals. The goal of this study was to examine the nature of the heavy metals, their mobility, and their binding in the soil matrix in order to understand the accumulation mechanism. Exhaustive mineralogical and geochemical study on the heavy metals in the vicinity of the river will allow knowing the dominant forms of emitted metals. The structural local order around Cr and Zn in soil samples were investigated by analyzing XAFS data. Our investigations show that the coordination sphere, around both Cr and Zn, is constituted of oxygen atoms at an interatomic distance of ∼2 Å which is close to those in clay minerals. It is also shown that Cr(III) is the most dominating redox state in soil samples. Moreover, the next backscattering neighbors around Zn and Cr are either carbon or sulfur atoms which reveal a multiple and heterogeneous speciation of Cr and Zn with organic matter.

In argillaceous rocks, which are considered as a potential host rock for nuclear waste repositories, sorption and diffusion processes govern the migration behaviour of actinides like neptunium. For the safety analysis of such a repository, a molecular-level understanding of the transport and retardation phenomena of radioactive contaminants in the host rock is mandatory. The speciation of Np during sorption and diffusion in Opalinus Clay was studied at near neutral pH using a combination of spatially resolved synchrotron radiation techniques. During the sorption and diffusion experiments, the interaction of 8 μM Np(V) solutions with the clay lead to the formation of spots at the clay-water interface with increased Np concentrations as determined by μ-XRF. Several of these spots are correlated with areas of increased Fe concentration. Np L₃-edge μ-XANES spectra revealed that up to 85% of the initial Np(V) was reduced to Np(IV). Pyrite could be identified by μ-XRD as a redox-active mineral phase responsible for the formation of Np(IV). The analysis of the diffusion profile within the clay matrix after an in-diffusion experiment for two months showed that Np(V) is progressively reduced with diffusion distance, i.e. Np(IV) amounted to ≈12% and ≈26% at 30 μm and 525 μm, respectively.

The reduction mechanism and adsorption behaviour of Cr(VI) onto Tin(II) oxy- hydroxides are investigated using Cr-K edge X-ray absorption fine structure (XAFS) spectroscopies. The synthesis of the Sn oxy-hydroxide proceeds via hydrolysis of SnSO₄. The successful reduction of Cr(VI) was identified by the analysis of the Cr-K edge XANES spectra where only Cr(III) species in octahedral sites are detected. According to the Cr-K edge EXAFS analysis results, Cr(III) forms bidentate inner sphere (binuclear (²C) and mononuclear (²E)) complexes. However, the surface coverage of Cr affects the type of Cr(III)-complexes formed: as the Cr-loading increases, Cr(III)-oxy-anions preferentially sorb in a "combined" ²C and ¹V configuration, at the expense of the existing ²E sorption geometry.

In-situ EXAFS combined with a Paris-Edinburgh press (PEP) is an outstanding tool to investigate the local environment of trace elements in melts at high pressure and temperature. A novel design of the pressure assembly ensures a highly stable experimental setup (reaching temperatures of up to 2000 K at 2.5 GPa) while permitting the necessary level of X- ray transmission. This study focuses on the structural incorporation of the geochemically important trace elements Y and Sr in sodium-rich silicate-carbonate melts. Y and Sr K edge EXAFS were collected in transmission mode of the melt (at ∼2.5 GPa, 1600 K) and its respective quench products. Distinct changes in the XANES region suggest a change in site symmetry during the cooling process.

XAFS of three Cu(II) diethylenetriamine complexes (in crystalline form) having different coordination geometries have been investigated. First complex has distorted tetragonal pyramidal, second has distorted square planar and third has distorted square pyramidal geometry. The difference in coordination geometries has been inferred from the differences in pre-edge peak, rising part of edge and in shape of white line, which are seen clearly in the derivative XANES spectra. The distortion in geometry has been correlated with the intensity of peaks in derivative spectra. These inferences have been corroborated from EXAFS analysis where the different paths have been used in the theoretical fits in R space to show contributions of different scatterers at different distances.

Trivalent americium was adsorbed on magnetite and maghemite under similar chemical conditions and the local environment probed by EXAFS spectroscopy. In both samples, partially hydrated Am(III) binds the surface but slightly different surface complexes were identified. On Fe₃O₄, Am(III) forms monomeric tridentate surface complexes similar to that reported for Pu(III) at the (111) surface. In contrast, the lower number of detected Fe atoms may suggest that Am(III) forms monomeric bidentate surface complexes on γ-Fe₂O₃. Alternatively, the lower Fe coordination number can also be due to the presence of vacancies in maghemite. XPS data imply very similar binding environments for Am at both Fe oxide surfaces.

The redox variations and changes in local atomic environment of uranium (U) interacted with the magnetite nanoparticles were studied in a proof of principle experiment by the U L₃ and M₄ edges high energy resolution X-ray absorption near edge structure (HR-XANES) technique. We designed and applied a mixed flow reactor (MFR) set-up to maintain dynamic flow conditions during U-magnetite interactions. Formation of hydrolyzed, bi- and poly-nuclear U species were excluded by slow continuous injection of U(VI) (10^-6 M) and pH control integrated in the MFR set-up. The applied U HR-XANES technique is more sensitive to minor changes in the U redox states and bonding compared to the conventional XANES method. Major U(VI) contribution in uranyl type of bonding is found in the magnetite nanoparticles after three days operation time of the MFR. Indications for shortening of the U-O_axial bond length for the magnetite compared to the maghemite system are present too.

The study of elemental speciation in atmospheric particulate matter is important for the assessment of the source of the particle as well for the evaluation of its toxicity. XANES data at Fe, Ni, and Zn K-edges are recorded on a sample of urban dust (from the Rimini area of Emilia Romagna region, Italy) deposited on a filter and on the NIST standard reference material 1648. Using linear combination fitting we give an indication of the chemical species of the three metals present in the samples.

In this study, the chemical reactions between As(III) and As(V) with glutathione, which is a target compound in As biochemistry due to its primordial role in As immobilization and intracellular reduction, in various molar ratios were investigated using As K-edge XAFS spectroscopy. Results showed a gradual substitution of As-O bonds in the coordination of aqueous As(III) and As(V) for three As-S bonds in the As+GSH complex. Moreover, the data showed reduction of As(V) to As(III) prior or concomitant to the As+GSH complex formation.

The local atomic structure around Ti in Ti-bearing hibonite (CaAl₁₂O₁₉) was studied using X-ray absorption near-edge structure (XANES) spectroscopy and computer modelling. Structural models of the direct substitution of Al by Ti³⁺, Al by Ti⁴⁺ charge balanced by the coupled substitution of Mg²+ for Al, and small Ti clusters were considered. The Ti K-XANES spectra of natural hibonite with different Ti concentration were recorded. Theoretical Ti K- XANES spectra for structural models of hibonite were calculated. It was shown that the theoretical Ti K-XANES spectra for a model with Ti at the five-coordinated M2 site are in agreement with the experimental XANES spectra of hibonite with low concentrations of Ti, while the theoretical spectra for a structural model of clustered Ti are in agreement with the experimental spectra of hibonite with higher Ti contents.

Synchrotron radiation micro-X-Ray Fluorescence (μ-XRF), X-ray photoelectron (XPS) and X-ray Absorption Fine Structure (XAFS) spectroscopies are applied for the study of paleontological findings. More specifically the costal plate of a gigantic terrestrial turtle Titanochelon bacharidisi and a fossilized coprolite of the cave spotted hyena Crocuta crocuta spelaea are studied. Ca L_2,3-edge NEXAFS and Ca 2p XPS are applied for the identification and quantification of apatite and Ca containing minerals. XRF mapping and XAFS are employed for the study of the spatial distribution and speciation of the minerals related to the deposition environment.

X-ray absorption spectroscopy is employed to study the local structure of pure and Cr-doped UO₂ at 300 K. The U L₃-edge EXAFS spectrum is interpreted within the multiplescattering (MS) theory using the results of the classical and ab initio molecular dynamics simulations, allowing us to validate the accuracy of theoretical models. The Cr K-edge XANES is simulated within the full-multiple-scattering formalism considering a substitutional model (Cr at U site). It is shown that both unrelaxed and relaxed structures, produced by ab initio density functional theory (DFT) calculations, fail to describe the experiment.

Local atomic and electronic structure investigations of uranium trioxide (UO₃) crystalline phases performed by the U M₄ edge HR-XANES technique is presented. The experimental U M₄ edge HR-XANES spectra of α-UO₃, β-UO₃ and γ-UO₃ polymorphic phases are compared with spectra of uranate (CaU₂O₇) and uranyl (UO₃•1-2(H₂O)) compounds. We describe a finger print approach valuable for characterization of variations of U-O axial bond lengths. Theoretical calculations of spectra using full-multiple-scattering theory (FEFF9.6 code) are performed. We have tested and selected input parameters, which provide best agreement between experimental and calculated spectra.

The dispersants Corexit 9500A and 9527A were used extensively during the Deepwater Horizon oil spill in the Gulf of Mexico. Sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy was used to investigate the dispersants for the sulfur based components. The main sulfur containing component should be dioctyl sodium sulfosuccinate (DOSS). S K-edge XANES analysis shows that indeed the major sulfur species in both kinds of Corexit (9500A and 9527A) is sulfonic acid which is a part of DOSS. In addition some fraction of sulfone was detected.

Environmental toxic metal contamination remediation and prevention is an ongoing issue. Graphene oxide is highly sorptive for many heavy metals over a wide pH range under different ionic strength conditions. We present x-ray absorption fine structure (XAFS) spectroscopy results investigating the binding environment of Pb(II), Cd(II) and U(VI) ions onto multi-layered graphene oxide (MLGO). Analysis indicates that the dominant sorption mechanism of Pb to MLGO changes as a function of pH, with increasing inner sphere contribution as pH increases. In contrast, the sorption mechanism of Cd to MLGO remains constant under the studied pH range. This adsorption mechanism is an electrostatic attraction between the hydrated Cd⁺² ion and the MLGO surface. The U(VI), present as the uranyl ion, changes only subtly as a function of pH and is bound to the surface via an inner sphere bond. Knowledge of the binding mechanism for each metal is necessary to help in optimizing environmental remediation or prevention in filtration systems.

The local structures of meteorite fusion crusts were studied by Ca, Ti and Fe K-edge XANES and EXAFS spectroscopy. The surface of meteorites were melted and volatilized with extreme high temperature and large temperature gradient when meteorites were rushed into atmosphere. This study indicated that meteorite fusion crusts have unique local structures. The local structures of fusion crusts differ from tektites especially in intensity of the shoulder in the rising flank of the edge in Ca XANES spectra. It is consistent with chemical composition change by the volatilization of Si at fusion during atmospheric entry. The high estimated Fe³⁺/ (Fe²⁺+Fe³⁺) ratio in meteorite fusion crusts indicates that meteorite fusion crusts are formed into atmospheric oxidation condition. The Ca-O distances in meteorite fusion crusts are 2.612.66 A and are extremely longer than in other natural glasses. The fusion crusts have unique local structure since they experienced extremely high temperature and short quenching time. The XAFS method is effective in distinction of meteorite fusion crusts and classification of natural glass.

Lanthanide silicates have been hydrothermally synthesized using Cu and Ni containers. Chemical formulae of the synthesized compounds correspond to K₃Eu[Si₆O₁₅] 2H₂O, HK₆Eu[Si₁₀O₂₅], K₇Sm₃[Si₁₂O₃₂], K₂Sm[AlSi₄O₁₂] 0.375H₂O, K₄Yb₂[Si₈O₂₁], K₄Ce₂[Al₂Si₈O₂₄]. The oxidation state of lanthanides (Eu, Ce, Tb, Sm, Yb) in these silicates has been determined using XANES spectroscopy at the Eu, Ce, Tb, Sm, Yb, L₃- edges. The experimental XANES spectra were recorded using the synchrotron radiation source ANKA (Karlsruhe Institute of Technology) and the X-ray laboratory spectrometer Rigaku R- XAS. By comparing the absorption edge energies and white line intensities of the silicates with the ones of reference spectra the oxidation state of lanthanides Eu, Ce, Tb, Sm, Yb has been found to be equal to +3 in all investigated silicates except of the Ce-containing silicate from the run in Cu container where the cerium oxidation state ranges from +3 (Ce in silicate apatite and in a KCe silicate with Si₁₂O₃₂ layers) to +4 (starting CeO₂ or oxidized Ce₂O₃).

Ni, Cr, Fe, Ca and Mn K-edge XANES and EXAFS spectra were measured on K-T boundary clays from Stevns Klint in Denmark. According to XANES spectra and EXAFS analyses, the local structures of Ni, Cr and Fe in K-T boundary clays is similar to Ni(OH)₂, Cr₂O₃ and FeOOH, respectively. It is assumed that the Ni, Cr and Fe elements in impact related glasses is changing into stable hydrate and oxide by the weathering and diagenesis at the surface of the Earth. Ca in K-T boundary clays maintains the diopside-like structure. Local structure of Ca in K-T clays seems to keep information on the condition at meteorite impact. Mn has a local structure like MnCO3 with divalent state. It is assumed that the origin on low abundant of Mn in the Fe-group element in K-T clays was the consumption by life activity and the diffusion to other parts.

The objective of this work was to study the molybdenum chemistry in UO₂ based materials, known as SIMFUELS. These materials could be used as an alternative to irradiated nuclear fuels in the study of fission products behaviour during a nuclear severe accident. UO₂ samples doped with 12 stable isotopes of fission products were submitted to annealing tests in conditions representative to intermediate steps of severe accidents. Samples were characterized by SEM-EDS and XAS. It was found that Mo chemistry seems to be more complex than what is normally estimated by thermodynamic calculations: XAS spectra indicate the presence of Mo species such as metallic Mo, MoO₂, MoO₃ and Cs₂MoO₄.

μ-XRF, XAFS and μ-XAFS spectroscopies were implemented in order to investigate the effect of thermal annealing on the stability of a vitrified tannery waste. The two dimensional μ-XRF scans disclose the presence of Cr-rich and depleted regions where both Cr(III) and Cr(VI) are present. However the polymerization of the Cr-O-Cr chains is different in these two distinct regions. More specifically, the μ-XANES and μ-EXAFS results reveal that in the Cr-rich inclusions, the Cr(in)O₆ belong to Cr₂O₃, while in the Cr-depleted regions, different linkages among the Cr(III)O₆ octahedra are detected. The percentage of the different type of polymeric structure around Cr(III) in the two distinct regions was assessed using Cr-K- EXAFS and XANES spectroscopies. It is revealed that upon thermal annealing the number of Cr(VI) ions is preserved and participate in the formation of the glass matrix. Even though Cr(III) is a glass modifier, the local coordination of the Cr(III)-octahedra changes upon thermal treatment. The presence of Cr(VI) suggests the limited capacity of the vitrification process to inhibit Cr(III) oxidation, however, Cr(VI) is safely trapped into both the glass and glass- ceramic matrix.

Studies of X-ray magnetic circular dichroism (XMCD) were performed for a set of GaMnAs films with different Mn concentrations priory and after high temperature annealing (500 and 600 ^oC). After thermal treatment, GaMnAs samples with zinc blende structure and MnAs hexagonal nano-clusters were formed. In most of the samples, both types of clusters were detected by EXAFS studies. Dependence of the orbital and the spin moments on magnetic field were calculated from XMCD data by applying the sum rule. It was shown that both moments were much larger for MnAs nano-clusters. When these inclusions are formed even in a small amount, they dominate the XMCD signal. Interestingly, in some of samples the zinc blende GaMnAs nano-clusters were observed at a surface while in the bulk of hexagonal MnAs. Therefore, the location of magnetic ions in the host matrix is crucial for their magnetic properties. This unique information can be provided by XAS and XMCD.

Strontium titanate is a model quantum paraelectric in which, in the region of dominating quantum statistics, the ferroelectric instability is inhibited due to nearly complete compensation of the harmonic contribution into ferroelectric soft mode frequency by the zero- point motion contribution. The enhancement of atomic masses by the substitution of ¹⁶ O with ¹⁸O decreases the zero-point atomic motion, and low-T ferroelectricity in SrTi¹⁸O₃ is realized. In this study we report on the local structure of Ti in SrTi¹⁶O₃ and SrTi¹⁸O₃ investigated by Extended X-ray Absorption Fine Structure measurements in the temperature range 6 - 300 K.

The structural configurations of In implanted Ge have been studied via x-ray absorption spectroscopy with and without the codoping of C. In the case of In singly implanted Ge, while the In atoms occupy an substitutional site in Ge (InGe₄) at low In concentration (≤ 2 at. %), they precipitate into a metallic phase (In metal) and form complexes composed of one vacancy and three Ge atoms (InVGe₃) at concentration ≥ 0.6 at. %. This behaviour can be suppressed by the addition of C leading to In-C pairing to form InCGe₃ complexes. This cluster enables In atoms to recover a four-fold coordinated structure and has the potential to improve the electrical activation of In atoms in Ge.

The local electronic and crystal structure of niobium-lead-germanate, Nb₂O₅-PbO- GeO₂ (NPG), glass thin films on silicon substrates were probed by XANES and EXAFS. NPG glasses are promising candidates for applications in nonlinear optical devices because they exhibit interesting optical characteristics such as high nonlinear third order optical susceptibility. In this work NPG glasses were prepared with pulsed laser deposition method with varying oxygen partial pressure to induce thin films with different oxygen stoichiometry. Previously, it was shown that oxygen stoichiometry has a very important effect to produce unusual high optical susceptibility. Detailed EXAFS and XANES analyses in a series of NPG thin films revealed the subtle variations in the local environment around Nb atoms and the Nb oxidation states caused by oxygen deficiencies.

We present soft x-ray absorption spectra from a series of Co doped ZnO films. We discuss systematic variations of the Co L-edge white line intensity and multiplet features for this series of samples. We document sizeable differences in the electronic state of the Co ionic cores, as well as in the local environment of the host lattice atoms, characterised by means of x-ray absorption spectra at the O K-edge and Zn L-edges. Model calculations allow to correlate the observed effects to small structural distortions of the ZnO lattice.

The structure of nano-crystalline Fe₂O₃ particles, synthesized using the microwave plasma technique, has been analysed using synchrotron based X-ray absorption spectroscopy and X-ray powder diffraction, as well as transmission electron microscopy. Furthermore, magnetic properties, the crystal structure, and the microstructures are compared and the potential model character of the samples for structure simulations is discussed.

Size of the clusters and structure details of fcc Cu clusters in nanocrystalline soft magnetic alloy of Fe_85-86Si_1-2B₈P₄Cu₁ (NANOMET) are investigated. A linear combination fitting of XAFS data indicates that about 30% of Cu atoms are partitioned in the fcc clusters and the rest in the amorphous matrix. EXAFS of the fcc Cu nanocluster embedded in amorphous matrix is calculated on the basis of a simple fcc structure model using FEFF9. Surface effect of the nanoclusters is considered by counting a fraction of the nearest neighbour atoms in amorphous matrix. Good agreement with the experimental result is obtained for the fcc nanocluster with 9 coordination shells which consists of total 177 atoms within 1.5 nm in a diameter.

Elemental codoping has been an effective way to regulate the structural and electronic properties of semiconductors. By using x-ray diffraction and x-ray absorption fine structure spectroscopy, we investigate the local structure and spatial occupations of Co dopants in Cu-doped ZnO thin films prepared by pulsed-laser deposition method. It is revealed that the Co dopants are substantially incorporated into ZnO matrix when the deposition temperature is increased up to 650 °C, although the preferential orientation of ZnO film is changed. The results provide experimental guidance in the synthesis of the co-doped ZnO based dilute magnetic semiconductors.

The formation process of 1,5-Bis(diphenylphosphino) pentane (L⁵)-protected Au nanocluster through the reduction of precursor Au₂L⁵Cl₂ by borane-tert-butylamine (TBAB) is traced by a combination of time-dependent x-ray/UV-vis absorption spectroscopies and mass spectrometry. It is revealed that the initial generation of dual-core basic unit Au₄L⁵₂Cl is a critical step, which allows for a subsequent size-growth process via incorporation of the existing Au monomer (Au(I)-Cl) or Au₂L⁵ to form Au⁵L⁵₂, Au8L⁵₃Cl, Au₁₀L⁵₄Cl and finally main Au₁₁L⁵₄Cl₂ This work advances one step further toward understanding the mechanism of formation and growth of diphosphine ligands-protected Au NCs.

Despite transition metal (TM) K-edge x-ray magnetic circular dichroism (XMCD) seems an interesting tool to get magnetic and structural information at the atomic scale, the effects originating this signal are still poorly understood. We thus initiated a deep investigation of the TM K-edge XMCD using Prussian Blue analogs (PBA) as model-compounds. In a recent study of the NiFe PBA family, we demonstrated that the XMCD signals at the TM K-edges strongly vary with external (mechanical) or internal (chemical) pressure and so that they are highly sensitive to small structural distortions. Following these first results, we extended this approach to the MnFe and CoFe families to evaluate the effect of electronic parameters (number of unpaired electrons of the M^II TM) on the XMCD signal. All the results set milestones in the disentanglement of the components originating the XMCD signals at the K-edge of TM and will eventually help in a better understanding of the photomagnetic properties of PBAs.

Plasmonic Ag nanostructures were generated in glass surfaces by means of UV laser irradiation (193 nm). The aim of the work was to identify the correlations between the atomic structure of such nanoparticles and their optical properties. The structural characterization of the samples, prepared with different number of laser pulses was performed by Ag K-edge EXAFS. The processing of the spectra by the Fourier-transform analysis gave the values of Ag-Ag and Ag-O interactions averaged over ionic and neutral states of silver in the sample. The consistent analysis of the behavior of features in optical spectra and the obtained dependencies of Ag-Ag and Ag-O structural parameters upon the number of laser pulses enabled to suggest the mechanism of plasmonic Ag nanoparticles formation in silicate glass, which is influenced by the interaction with polyvalent ions (for example Fe²⁺) and by defect centers (for example HTC and NBOHC centers) generated by UV irradiation.

We report on Co K-edge x-ray magnetic circular dichroism (XMCD) measurements of LaCoO₃ single crystal in temperature range from 5 to 300 K and external magnetic field of 17 T. The response consists of pre-edge (at 7712 eV) and bi-polar peak (up at 7727, down at 7731 eV) with amplitudes, respectively, less than 10^-3 and 10^-2 of the Co K-edge jump. Using the sum rule the orbital magnetic moment of 4p Co is evaluated. Its temperature dependence reaches a maximum of (2.7 ± 0.9) ^x10^-3 μB at 120 K, following the trend for the total magnetic moment on the Co obtained from the superconducting quantum interference device measurements. However, on warming from 25 to 120 K, the orbital magnetic moment of the 4p Co doubles while total magnetic moment of Co increases 10 times. First principle calculations are in order to relate the Co K-edge XMCD results to the orbital and spin moment of 3d Co.

We report the high-pressure XANES study of the electronic phase transition from 4f⁷ to 4f⁶ configuration of europium in the rare-earth compound EuCu₂Ge₂. The hydrostatic pressure dependence of the europium valence was obtained in a wide pressure range (1-30 GPa) at room temperature. It was found that upon the pressure increase above 20 GPa the europium valence does not reach the integer value +3 but stabilizes at 2.87. The experimental results were supported by the band structure calculations in the framework of DFT, which allowed us to discuss the features of 3d-4f hybridization in this system. The study also compares the mechanisms of external and "chemical" pressure by the Si substitution in Ge site in series EuCu₂(Si_xGe_1-x)₂.

The process of Tb₂Hf₂O₇ nanocrystals formation upon annealing to 1600°C was investigated by means of X-ray absorption fine structure (XAFS) spectroscopy combined with X-ray diffraction (XRD) and pair distribution function (PDF) analysis. The structure ordering and the growth of nanocrystals upon annealing were estimated independently from XRD patterns and PDF. The probable content of Tb⁴⁺ ions in Tb₂Hf₂O₇ was estimated from XANES. All studies indicate a high disorder and a large number of local structure defects in Tb₂Hf₂O₇ pyrochlore oxide.

The redistribution of Mn atoms in Ga_1-xMn_xAs layer during medium-temperature annealing, 250-450 ^oC, by Mn K-edge X-ray absorption fine structure (XAFS) recorded at ALBA facility, was studied. For this purpose Ga_1-xMn_xAs thin layer with x=0.01 was grown on AlAs buffer layer deposited on GaAs(100) substrate by molecular beam epitaxy (MBE) followed by annealing. The examined layer was detached from the substrate using a "lift-off" procedure in order to eliminate elastic scattering in XAFS spectra. Fourier transform analysis of experimentally obtained EXAFS spectra allowed to propose a model which describes a redistribution/diffusion of Mn atoms in the host matrix. Theoretical XANES spectra, simulated using multiple scattering formalism (FEFF code) with the support of density functional theory (WIEN2k code), qualitatively describe the features observed in the experimental fine structure.

Determining the local structure of catalyst materials is critical for understanding the mechanism of enhanced electrochemical activity in semiconductor electrode. Here, using X-ray absorption fine structure (XAFS) spectra, we reveal that the local disorder structure is formed for the mixed-phase Co₃O₄ nanowire arrays due to the interaction between the phases of Co₃O₄ and Co₂(OH)₂CO₃. Comparing to pure Co₃O₄ nanowire arrays, the mixed phase sample is richer in Co²⁺ and the electronic structure is changed by the local structure, which are demonstrated by the X-ray absorption near-edge structure (XANES) spectra. It is deduced that the mixed-phase Co₃O₄ nanowire arrays with abundant Co²⁺ sites provide more redox centres in electrochemical reaction than the pure Co₃O₄ nanowire arrays.

We report a surface structure study of an amorphous Zn-Sn-O (a-ZTO) transparent conducting film using the grazing incidence X-ray absorption spectroscopy technique. By setting the measuring angles far below the critical angle at which the total external reflection occurs, the details of the surface structure of a film or bulk can be successfully accessed. The results show that unlike in the film where Zn is severely under coordinated (N < 4), it is fully coordinated (N = 4) near the surface while the coordination number around Sn is slightly smaller near the surface than in the film. Despite a 30% Zn doping, the local structure in the film is rutile-like.

Mn₃GaC and Mn₃SnC are two antiperovskites which exhibit a large magnetocaloric effect associated with a magnetostructural transformation. Although structurally similar, the magnetic transition and the nature of magnetocaloric effect in the two compounds is completely different. While Mn₃GaC transforms from a ferromagnetic to an antiferromagnetic state at T_t = 178K with the antiferromagnetic propagation vector along K = ½, ½, ½, in Mn₃SnC the transformation occurs at T_t = 280K from a paramagnetic state to an antiferromagnetic state with K = ½, ½, 0. Mn K EXAFS has been employed to show that these differences in magnetic properties are related to local structural distortions in Mn₆C octahedra which are quite different in the two compounds.

A combined high-resolution Co K-edge extended x-ray absorption fine structure (EXAFS) and high-resolution X-ray powder diffraction (XRD) study has been performed to clarify the detail of anomalous behavior of temperature-dependent magnetic susceptibility curve on the LaCoO₃ across the spin-state (∼120 K) transition. According to XRD analysis, the Debye-Waller factor of Co-O bond exhibit rapid growth below 20 K whereas the temperature dependence of the average Co-O bond length shows linear behavior from 10 K to 400 K. The EXAFS data show an anomalous decrease of the Co-O bond lengths with respect to those obtained by XRD. No local distortion of CoO₆ octahedral as temperature increases up to 400 K has been detected.

We investigated the relative importance of removing the Mn³⁺ Jahn-Teller distortion in driving ferromagnetism in LaMn_1-xSc_xO₃ combining x-ray powder diffraction and x-ray absorption spectroscopy at the Mn and Sc K-edges. By increasing the Sc content, the orthorhombic distortion of the Pbnm cell in LaMnO₃ decreases but the unit-cell remains slightly distorted in LaScO₃. Besides, the nearly tetragonal-distorted MO₆ in LaMnO₃ continuously evolves into a nearly regular one in LaScO₃. On the other hand, x-ray absorption spectra show that the MnO₆ octahedron remains Jahn-Teller distorted and the ScO₆ octahedron is nearly regular along the whole series. Moreover, the ordering of the Mn³⁺ Jahn-Teller distortion is not disrupted in the ab plane for any Sc concentration. This contrasts with the Ga- substituted compounds, where a regular MnO₆ is found for x>0.5. However, both LaMn_0.5Sc_0.5O₃ and LaMn_0.5Ga_0.5O₃ show ferromagnetic behavior independently of the presence (or not) of Jahn-Teller distorted Mn³⁺. Thus, our results point to the Mn-sublattice dilution as the main effect in driving ferromagnetism in these manganites over local structure effects previously proposed by the spin flipping or the vibronic superexchange models.

We examined the synthesis of copper nanoparticles by photoreduction, and characterized them using optical spectroscopy, XAFS measurement, and electron microscopy. Ethanol solution of copper acetate with TiO₂ nanoparticles was photoirradated. Optical absorption observation indicated that copper nanoparticles were formed in the solution. XAFS measurement indicated that the nanoparticles were metallic, not oxidized. Electron microscopy observation exhibited that the nanoparticles kept metallic even under exposure to air.

Zr and Ti K-edge XANES spectra of PbZrO₃, PbTiO₃ and BaTiO₃ perovskite-type compounds were measured in the temperature range from 10K to 850K. Quantitative comparisons for the near-edge spectra were performed in a wide temperature range using the absorption intensity invariant point (AIIP) standardization. Clear temperature dependence for pre-edge shoulder is identified by the calculating the temperature difference of the XANES spectrum intensity. Decrease of pre-edge shoulder and peak intensity is observed only in the para- and ferro-electric phases and draw curves, not straight lines. The gradients for shoulder and pre-edge peak intensity are rich in a variety. The decrease in absorption of pre-edge peak and shoulder is speculated due to the shift from the off-centre position of the Zr atom with respect to the oxygen octahedron to center position. The Zr ion in the PbZrO₃ para-electric phase has same temperature behaviors of Ti ions in the ferroelectric perovskite.

In-situ high-pressure W L₁ and L₃ edges x-ray absorption and mid-infrared spectroscopies complemented by first-principles calculations suggest the existence of pressure- induced insulator-to-metal transition in α-SnWO₄ in the range of 5-7 GPa. Its origin is explained by a symmetrization of metal-oxygen octahedra due to a strong interaction of Sn 5s, W 5d and O 2p states along the b-axis direction, leading to a collapse of the band gap.

The local structural and local density of states of vertically-aligned ZnO nanorods are examined by using polarization-dependent diffraction anomalous near edge structure (DANES) measurements from c-oriented ZnO nanorods at the Zn K edge at the geometry of the incident x-ray electric field parallel and perpendicular to the x-ray momentum transfer direction. Orientation-dependent local structures determined by DANES are comparable with polarization- dependent EXAFS results. Unlike other techniques, polarization-dependent DANES can uniquely describe the orientation-dependent local structural properties and the local density of states of a selected element in selected-phased crystals of compounds or mixed-phased structures.

In situ synchrotron radiation XANES and XRD have been carried out on Li₂FeSiO₄ cathode material in a lithium-ion-battery (LIB) cell. The evolution of the long range lattice structure and the local iron oxidation state has been observed at a charging rate of C/20 for the formation cycle for one Lithium extraction; additional ex situ measurements of the pristine cathode material were taken for comparison. The observed spontaneous interaction between the cathode and the fluorinated electrolyte and the impact of subsequent cycling are discussed.

We synthesized UiO-67 Metal Organic Frameworks (MOFs) functionalized with bpydcPt(II)Cl₂ and bpydcPt(IV)Cl₄ complexes (bpydc = bipyridine-dicarboxylate), as attractive candidates for the heterogenization of homogeneous catalytic reactions. Pt L₃-edge XAFS experiments allowed us to thoroughly characterize these materials, in the local environment of the Pt centers. XAFS studies evidenced the rich reactivity of UiO-67-Pt(II) MOFs, including reduction to bpydcPt(0) under H₂ flow in the 600-700 K range, room-temperature oxidation to bpydcPt(IV)Br₄ through oxidative addition of liquid Br₂ and ligand exchange between 2 Cl^- and even bulky ligands such as toluene-3,4-dithiol. Preliminary XANES simulations with ADF code provide additional information on the oxidation state of Pt sites.

A combined analysis of EXAFS and Raman spectra is applied for the study of In_xGa_1-xN alloys with 0.3<x<0.5. Alloying causes relaxation of the selection rules resulting in Raman spectra that resemble the vibrational density of states. On the other hand, theoretical simulation of the Raman spectra using the Equation of Motion routine of FEFF8 provides the vibrational component of the Debye-Waller factor (DWF). The static disorder component of the DWFs was obtained by fitting the Ga and In K-edge EXAFS spectra. The analysis revealed that the nearest neighbor distances of the 1^st and 2^nd shell deviate from the values predicted by the law of Vegard and the virtual crystal approximation. The static disorder in the first nearest neighboring shell (In-N and Ga-N) is null whereas in the cation-cation neighboring shells the static component is generally smaller than the vibrational.

Operando XANES and EXAFS spectra on the newly prepared Fe hexacyanocobaltate active material for positive electrodes in lithium batteries have been recorded at the XAFS beamline of Elettra using a suitable in situ cell. In this way, it was possible to follow in detail the main structural and electronic changes during the charge and discharge processes of the battery. The use of a chemometric approach for data analysis is also underlined.

Understanding the structure-activity of the metal hydroxide materials is critical to the design of an efficient oxygen evolution reaction (OER) catalyst for water oxidation. A challenge is to identify and collect surface active site relative to bulk. Here, we have prepared an ultrathin α-Co(OH)₂ nanosheet with large exposed surface Co sites as an high-efficiency O₂ evolution catalyst. Using XAFS technique, we have investigated the oxidation state and local structural evolutions of the α-Co(OH)₂ nanosheets catalyst. A coordination-miss Co sites (CoO_6-x) with oxidation state of +3.3 on the nanosheet surface is revealed after the OER procedure, indicating the in situ formation of y-CoOOH nanosheet is a key factor leading to an enhanced water oxidation performance.

The AB and/or Al₂O₃-coated Li_1.20Mn_0.55Ni_0.16Co_0.09O₂ were prepared by the mechanochemical reaction. The optimal condition for sample preparation was selected to be the rotation speed of 2000 rpm and the reaction time of 5 minutes by SEM and XANES measurements. Surface analysis using SEM and XANES data demonstrated that all the samples were rather uniformly covered with AB and/or nano-AEO₃ particles. The AEO₃- coated samples showed less discharge capacity and C-rate performance compared with the pristine sample, while the AB/Al₂O₃-coated sample showed almost the same discharge capacity and C-rate performance and had better cycle performance at 318 K compared with the pristine sample. These results demonstrate that the mechanochemical AB/Al₂O₃-coating process is an effective way of improving the cycle performance at high temperature without degrading the discharge capacity and C-rate performance.

X-ray absorption spectroscopy (XAS) is applied to study the local geometry of Co, Ni, and Mn sites in a new high voltage cathode for lithium batteries. The material is a solid solution between Li₂MnO₃ and Li_(x)Mn_0.4Ni_0.4Co_0.2O₂. The XAS technique has permitted to check the local atomic structure and charge associated with the metals in a series of electrodes with different lithium concentration x, obtained during the first charge operation, and compared to the first discharge and a successive charge. The ex-situ XAS investigation on the initial activation of the cathode material (first charge) can be described by two separated reaction of LiMO₂ (M = Ni and Co) and Li₂MnO₃. The strength and limitations of the ExAFS approach in these materials is underlined.

The paper presents a new results on the bonding environment (coordination number and geometry) and on oxidation states of Fe in nitrogen-modified Fe/C composites used as Pt-free catalysts for oxygen reduction in Direct Hydrogen Fuel Cells. Starting from glucose or fructose, two catalysts displaying different electrochemical performance were prepared and studied in the form of pristine powder and thin catalytic layer of electrode by Fe K-edge XAFS spectroscopy. The results show how the Fe local structure varies as a function of different synthesis conditions and how changes in the structural properties of the catalysts are related to fuel cell electrochemical performance increase during a cell activation period.

The superionic behavior of cubic δ-phase Bi₂O₃, a metastable phase at high temperature, is of great interests from both scientific and technological perspectives. With the highest ionic conductivity among all known compounds, the δ-phase Bi₂O₃ possesses promising applications in solid-oxide fuel cells. Previous investigations pointed out the α to δ- phase transition occurs during the heating process, as supported by the X-ray and Neutron diffraction experiments. Through in situ measurements of the long-range order structure and the local structure by X-ray powder diffraction and X-ray absorption spectroscopy, we investigated the evolution of the structures under different temperatures. Both techniques provided ample evidence that the existence of meta-stable β-phase are crucial for forming the defective fluorite cubic δ phase. Our finding suggested that the phase transition from tetragonal β-phase to δ-phase is an influencing factor for the generation of the oxygen-ion pathways.

Nitrogen K-edge XPS and NEXAFS of the two polymorphic forms of para- aminobenzoic acid (PABA) are significantly different reflecting variation in hydrogen bonding. Alteration in hydrogen bonding at the amino group leads to a shift to high energy for both the XPS N 1s core level and the 3π* NEXAFS resonance with β-PABA. Participation of the amine group in the aromatic system causes the 1π* resonance to be sensitive to the nature of the intermolecular bonding at the para-carboxylic acid group, and a shift to low energy for α- PABA is observed due to hydrogen-bonded carboxylic acid dimer formation. FEFF calculations also successfully reproduce both the energy and intensity variations observed for the σ* shape resonance associated with the C-N bond, with the majority of the decrease in energy observed for b-PABA arising from the longer C-N bond.

Five biomimetic mono- or dinuclear nickel complexes featuring Ni(I) or Ni(II) sites were studied by X-ray absorption and emission spectroscopy and DFT calculations. Ni K-edge XANES spectra and Kβ main and satellite emission lines were collected on powder samples. The pre-edge absorption transitions (core-to-valence excitation) and Kβ_2,5 emission transitions (valence-to-core decay) were calculated using DFT (TPSSh/TZVP) on crystal structures. This yielded theoretical ctv and vtc spectra in near-quantitative agreement with the experiment, showing the adequacy of the DFT approach for electronic structure description, emphasizing the sensitivity of the XAS/XES spectra for ligation/redox changes at nickel, and revealing the configuration of unoccupied and occupied valence levels, as well as the spin-coupling modes in the dinuclear complexes. XAS/XES-DFT is valuable for molecular and electronic structure analysis of synthetic complexes and of nickel centers in H₂ or CO_x converting metalloenzymes.

The structural properties of geminal dicationic ionic liquids ([C_n (mim)₂]Br₂)/water mixtures have been investigated by means of extended X-ray absorption fine structure (EXAFS) spectroscopy and Molecular Dynamics (MD) simulations. This synergic approach allowed us to assess the reliability of the MD results and to provide accurate structural information about the first coordination shell of the Br^- ion. We found that the local environment around the anion changes as a function of the water concentration, while it is the same independently from the length of the bridge-alkyl chain. Moreover, as regards the long-range structural organization, no tail-tail aggregation occurs with increasing alkyl chain length.

Solid-state and solution pH-dependent NEXAFS studies allow direct observation of the electronic state of para-aminobenzoic acid (PABA) as a function of its chemical environment, revealing the chemical state and bonding of the chemical species. Variations in the ionization potential (IP) and 1s→π* resonances unequivocally identify the chemical species (neutral, cationic, or anionic) present and the varying local environment. Shifts in σ* shape resonances relative to the IP in the NEXAFS spectra vary with C-N bond length, and the important effect of minor alterations in bond length is confirmed with nitrogen FEFF calculations, leading to the possibility of bond length determination in solution.

The combination of X-ray diffraction with EXAFS was employed to assess the coordination environment of lanthanide complexes in solutions. This method is based on the assumption that the local structure of lanthanide complexes in solution combines elements of the crystal structure of the complex in the solid state (single- or polycrystalline) and the elements of the local structure of a lanthanide salt, completely dissociated in the solvent (usually chlorides). The success of this approach is demonstrated with the lanthanide (III) 2,3,4,5,6-pentafluorobenzoate complexes, where the local structure in aqueous and methanol solutions were estimated. Moreover, the dissociation degree of the complexes in aqueous and methanol solutions was evaluated.

There are two different motifs of X-ray absorption spectra for Cu(I) K-edge in amyloid-β peptide which could be due to two different configurations of local Cu(I) environment. Two or three histidine ligands can coordinate copper ion in varying conformations. On the other hand, oxidation of amyloid-β peptide could play an additional role in local copper environment. In order to explore the peculiarities of local atomic and electronic structure of Cu(I) binding sites in amyloid-β peptide the x-ray absorption spectra were simulated for various Cu(I) environments including oxidized amyloid-β and compared with experimental data.

The pigment Prussian blue is studied in heritage science because of its capricious fading behavior under light exposure. We show here that XANES can be used to study the photosensitivity of Prussian blue heritage materials despite X-ray radiation damage. We used an original approach based on X-ray photochemistry to investigate in depth the redox process of Prussian blue when it is associated with a cellulosic substrate, as in cyanotypes and watercolors. By modifying cation and proton contents of the paper substrate, we could tune both rate and extent of Prussian blue reduction. These results demonstrate that the photoreduction and fading of Prussian blue is principally mediated by the substrate and its interaction with the oxygen of the environment.

We have used confocal methods to examine the distribution and speciation of arsenic within amphibian tissue (Bufo americanus) from a contaminated mine site. The use of new microchannel technology permits a confocal, and energy-independent, examination of a given voxel within the amphibian tissue without the need for sectioning. We observe differences in arsenic concentration and speciation depending on tissue type, with the Eberth- Katschenko layer in particular containing Mn, Fe, Cu and Zn in addition to Ca and pentavalent arsenic.

The usefulness of full field transmission spectroscopy is shown using the example of mandible of the stick insect Peruphasma schultei. An advanced data evaluation tool chain with an energy drift correction and highly reproducible automatic background correction is presented. The results show significant difference between the top and the bottom of the mandible of an adult stick insect.

A tapered undulator beamline BL36XU was constructed at SPring-8 to conduct structural and electronic analysis of dynamic events on polymer electrolyte fuel cell (PEFC) cathode catalysts for the development of next-generation PEFCs. BL36XU provides various time and spatially resolved XAFS techniques in an energy range from 4.5 to 35 keV for investigating PEFCs under the operating conditions. In addition, we developed in-situ complementary measurement systems, such as in-situ time-resolved XAFS/XRD and ambient pressure HAXPES systems. This report describes the performance and present status of the BL36XU.

The spatial distribution of the oxidation state for the nickel species in the LiNiO₂ cathode was analyzed by means of the in-situ XAFS imaging technique during the charging and discharging processes. The inhomogeneous reaction for the LiNiO2 cathode was observed under the operating condition. The pattern in the 2-dimensional map of the oxidation state of the active material in the discharging process was similar to that in the charging process. It means that the areas preceding the discharging reaction agree with the areas delaying the charging reaction. It was suggested that the diffusion of Li⁺ was restricted by the surface product of the LiNiO₂ electrode, and the concentration gradient of Li⁺ delayed the charging reaction at the reaction channel of the discharging reaction.

The dissolution parameters of calcium carbonates play a key role in agriculture as they regulate the plant nutrients uptake and buffer the pH-value of the soil. The combination of μXRF, μXAS and μXRD mapping in the hard X-ray regime for the examination of both short- and long range order in natural limestones revealed that their dissolution properties depend both on the crystallinity of the mineral phases and their composition. The results particularly show that in many cases the presence of magnesium inhibits dissolution of the phases.

The online sulfiding process for nickel-contained catalyst often ends up with a nickel sulfide mixture in refinery plant. To elucidate the local environment of nickel and its corresponding sulfur species, a model catalyst (nickel sulfide) and model thermal process were employed to explore the possibilities for characterization of real catalysts in industrial conditions. The present investigation shows effectiveness of in situ XANES and EXAFS measurements for studying the phase stability and phase composition in these systems, which could be used to simulate real sulfiding process in industrial reactions, such as hydrodesulfurizations of oil.

Aichi Synchrotron Radiation Center was designed for industrial use following five years of discussion among academia, industry and local government in the Aichi area. Among the six beam lines constructed, those that facilitated X-ray absorption fine structure (XAFS) analysis were given first priority. In addition to the hardware, attention was given to the development of operating procedures that were quick and user-friendly. The facility entered public service in March 2013. In the year 2013, 55% of the experiments involved XAFS analysis (hard X-ray, soft X-ray and vacuum ultraviolet regions) and in 2014 it was 57%. The range of research fields is very broad, emphasizing the importance of the XAFS beam lines.

XAFS-experiments in transmission and reflection modes have been performed using a Pilatus 100K pixel detector. Transmission mode XAFS spectra from a Co metal foil and Co₃O₄ were recorded to evaluate the data quality offered by this 2D-detector. Furthermore, the pixel detector was also used to measure reflection mode grazing incidence EXAFS data. Using different regions of interest in the collected scattering patterns, we will show that the diffuse scattering can be separated for the different contributing surfaces and interfaces, allowing simultaneous investigations of surfaces and buried interfaces within multi-layered samples.

We propose a standard data format for the interchange of XAFS data. The XAFS Data Interchange (XDI) standard is meant to encapsulate a single spectrum of XAFS along with relevant metadata. XDI is a text-based format with a simple syntax which clearly delineates metadata from the data table in a way that is easily interpreted both by a computer and by a human. The metadata header is inspired by the format of an electronic mail header, representing metadata names and values as an associative array. The data table is represented as columns of numbers. This format can be imported as is into most existing XAFS data analysis, spreadsheet, or data visualization programs. Along with a specification and a dictionary of metadata types, we provide an application-programming interface written in C and bindings for programming dynamic languages.

ROCK is a new beamline at SOLEIL dedicated to Quick-EXAFS measurements. The optical layout has been optimized to get full advantage of the monochromators, which were designed at SOLEIL and successfully used at SAMBA from 2009 to 2014. ROCK has started user operations since March 2015. It is mainly employed to monitor fast kinetic processes in materials used in catalysis and energy sciences. A review of the ROCK performances and capabilities is presented. The high automation achieved for fast change of monochromators, optimization of mirrors for harmonic rejection and detectors allows the simultaneous operando characterization of different chemical elements present in a material during the same reaction.