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Introduction
Personal literature selection => https://twitter.com/scimaus
List of publications => http://orcid.org/0000-0003-2539-6198
Additional affiliations
January 2017 - present
January 2014 - January 2017
September 1999 - May 2005
Education
September 2005 - October 2009
September 2000 - May 2005
Publications
Publications (82)
We present the development, manufacturing and performance of spherically bent crystal analyzers (SBCAs) of 100 mm diameter and 0.5 m bending radius. The elastic strain in the crystal wafer is partially released by a "strip-bent" method where the crystal wafer is cut in strips prior to the anodic bonding process. Compared to standard 1 m SBCAs, a ga...
The study of the speciation of highly diluted elements by X‐ray absorption spectroscopy (XAS) is extremely challenging, especially in environmental biogeochemistry sciences. Here we present an innovative synchrotron spectroscopy technique: high‐energy resolution fluorescence detected XAS (HERFD‐XAS). With this approach, measurement of the XAS signa...
This review aims to introduce the x-ray emission spectroscopy (XES) and resonant inelastic x-ray scattering (RIXS) techniques to the materials scientist working with magnetic semiconductors (e.g. semiconductors doped with 3d transition metals) for applications in the field of spin-electronics. We focus our attention on the hard part of the x-ray sp...
Humans are contaminated by mercury in different forms from different sources. In practice, contamination by methylmercury from fish consumption is assessed by measuring hair mercury concentration, whereas exposure to elemental and inorganic mercury from other sources is tested by analysis of blood or urine. Here, we show that diverse sources of hai...
The semiconductors doped with magnetic ions (DMS) are promising materials for applications in the emerging field of spintronics. To address this challenge, a relatively high amount of magnetic impurities should enter the host crystal structure without phase separation, thus a detailed characterization at the nano-scale is mandatory. X-ray absorptio...
Vanadium fluoride phosphates are highly intriguing due to their diverse crystal structures, which significantly influence their electrochemical properties, making them favorable candidates for Li-ion and post Li-ion battery applications. In this study, high-energy resolution fluorescence-detected X-ray absorption near-edge structure (HERFD-XANES) s...
Among all positive electrode materials for K-ion batteries (KIBs), KVPO 4 F offers a high theoretical capacity of 131 mAh·g ⁻¹ and an average working potential reaching above 4.3 V vs K ⁺ /K, resulting in a theoretical energy density of up to 520 Wh·kg ⁻¹ . [1] The anionic substitution of fluorine by oxygen in KVPO 4 F 1-x O x (x = 0, 0.25, 0.5, 0....
This paper presents the development of a novel high-pressure/high-temperature reactor cell dedicated to the characterization of catalysts using synchrotron x-ray absorption spectroscopy under operando conditions. The design of the vitreous carbon reactor allows its use as a plug-flow reactor, monitoring catalyst samples in a powder form with a cont...
Understanding the intricate crystal structure of polyanionic positive electrode materials is essential for elucidating the mechanisms involved during cycling and predicting the working potential of the electrode. To achieve this goal, a clear comprehension of how the coordination environment of the transition metal ion influences the ionicity/coval...
Fluorapatite (FAp, nominally Ca5(PO4)3F) is the most common phosphate mineral at the Earth’s surface and a main host for rare-earth elements (REE) in magmatic and hydrothermal ore deposits and in marine sediments. Our understanding of the enrichment process of REE in FAp rests upon two foundations: (1) being able to elucidate the thermodynamic driv...
Vanadium (V) is the second most abundant transition metal in the oceans. Nevertheless, its concentration in organisms is generally low despite its involvement in various physiological or enzymatic functions. Because exposure to high concentrations was shown to be harmful for various organisms including animals, the unexpected very high concentratio...
Magnetic cooling has the potential to replace conventional gas compression refrigeration. Materials such as La(Fe,Si)$_{13}$ exhibit a sizeable first-order magnetocaloric effect, and it is possible to tailor the phase transition towards room temperature by Mn-H-doping, resulting in a large temperature range for operation. Within this work, we discu...
Tree bark near former mercury (Hg) mines and roasting plants is known to have exceptionally high (up to several mg kg-1) Hg concentrations. This study explores the change of Hg speciation with depth (down to 25-30 mm from the outermost surface) in black pine (Pinus nigra) bark by means of high-resolution X-ray absorption near edge structure (HR-XAN...
The study of elements with X-ray absorption spectroscopy (XAS) is of particular interest when studying the role of metals in biological systems. Sample preparation is a key and often complex procedure, particularly for biological samples. Although X-ray speciation techniques are widely used, no detailed protocol has been yet disseminated for users...
Pyrite (FeS2), arsenopyrite (FeAsS) and löllingite (FeAs2) are exceptional gold concentrators on Earth; yet the exact redox and structural state of this “invisible” gold and the forces driving its intake and release by these minerals remain highly controversial. Here we applied high resolution X-ray absorption spectroscopy to Au-bearing pyrite and...
X-ray emission spectroscopy in a point-to-point focusing geometry using instruments that employ more than one analyzer crystal poses challenges with respect to mechanical design and performance. This work discusses various options for positioning the components and provides the formulas for calculating their relative placement. Ray-tracing calculat...
Fluids responding to magnetic fields (ferrofluids) offer a scene with no equivalent in nature to explore long-range magnetic dipole interactions. Here, we studied the very original class of binary ferrofluids, embedding soft and hard ferrimagnetic nanoparticles. We used a combination of x-ray magnetic spectroscopy measurements supported by multi-sc...
The design and first results of a large-solid-angle X-ray emission spectrometer that is optimized for energies between 1.5 keV and 5.5 keV are presented. The spectrometer is based on an array of 11 cylindrically bent Johansson crystal analyzers arranged in a non-dispersive Rowland circle geometry. The smallest achievable energy bandwidth is smaller...
In many hydrothermal deposits arsenian pyrite contains economic concentrations of Au in an “invisible” form, which is structurally bound in pyrite or has grain size <0.1 μm. Here we use X-ray absorption spectroscopy (XAS) of natural minerals and synthetic phases to reveal the forms of Au occurrence in pyrite and determine the effect of physicochemi...
We describe the design and show first results of a large solid angle x-ray emission spectrometer that is optimised for energies between 1.5 keV and 5.5 keV. The spectrometer is based on an array of eleven cylindrically bent Johansson crystal analysers arranged in a point-to-point Rowland circle geometry. The smallest achievable energy bandwidth is...
FAME-UHD (French Absorption beamline for Material and Environmental sciences Ultra High Dilution) beamline at the ESRF is dedicated to High-Energy Resolution Fluorescence Detected X-ray Absorption Spectroscopy (HERFD-XAS) and X-ray Emission Spectroscopy in the hard X-ray energy range, from 4.8 to 20 keV. The beamline is open to users' operation sin...
In Rhodospirillum rubrum, the maturation of carbon monoxide dehydrogenase (CODH) requires three nickel chaperones, namely RrCooC, RrCooT and RrCooJ. Recently, the biophysical characterisation of the RrCooT homodimer and the X‐ray structure of its apo form revealed the existence of a solvent‐exposed NiII‐binding site at the dimer interface, involvin...
Yttrium belongs to the rare earth elements (REE) together with lanthanides and scandium. REE are commonly used in modern technologies, and their limited supply has made it necessary to look for new alternative resources. Acid mine drainage (AMD) is a potential resource since is moderately enriched in REE. In fact, in passive remediation systems, wh...
ABSTRACT: The structural chemistry of gold in arsenian pyrite (FeS2)
and arsenopyrite (FeAsS) is as yet unknown, despite the economic
importance of this element and its potential recovery from low-grade ores
and mine tailings. The systematic co-occurrence of Au and As poses a
challenge for measuring the Au L3-edge X-ray absorption spectra because
t...
Arsenian pyrite is an abundant mineral occurring in many geological settings at the Earth's surface, including hydrothermal ore deposits which are the main source of Au. So-called "invisible" (or refractory) form of Au is present in pyrites in all types of these deposits, and its concentration is often directly correlated with As content. Here we r...
FAME (French Absorption beamline for Material and Environmental sciences) and FAME-UHD (FAME-Ultra High Dilution) are two French CRG beamlines at ESRF dedicated to X-ray Absorption Spectroscopy (XAS) in material science, catalysis and especially in environmental and Earth sciences. The study of the speciation of highly-diluted elements by XAS is ex...
This study reports the influence of magnesium incorporation into cuprous oxide (Cu 2 O) on its transformation into cupric oxide (CuO). Thermal treatments under oxidizing conditions are performed on undoped and magnesium-doped cuprous oxide thin films, Cu 2 O and Cu 2 O:Mg respectively, deposited by aerosol-assisted metal-organic chemical vapor depo...
The freshwater cyprinid Tanichthys albonubes was used to assess the bioavailability of divalent mercury (Hg(II)) complexed in dissolved organic matter (DOM) to fish. The fish acquired 0.3 to 2.2 µg Hg/g dry weight after eight weeks in aquaria containing DOM from a Carex peat with complexed mercury at initial concentrations of 14 nM to 724 nM. Chang...
Blue mussel, a widely distributed filter‐feeder mollusk often used as a sentinel organism for marine pollutants, copes with metal toxicity by overexpressing metallothionein, represented as wicked enchantments on the frontispiece. Two mercury‐thiolate complexes were identified in metallothionein in response to in vivo Hg exposure using high energy‐r...
Of all divalent metals, mercury (HgII) has the highest affinity for metallothioneins. HgII is considered to be enclosed in the α and β domains as tetrahedral α‐type Hg4Cys11‐12 and β‐type Hg3Cys9 clusters similar to CdII and ZnII. However, neither the four‐fold coordination of Hg nor the existence of Hg–Hg atomic pairs have ever been demonstrated,...
Zinc (Zn) is a potentially toxic trace element that is present in large amounts in organic wastes (OWs) spread on agricultural lands as fertilizer. Zn speciation in OW is a crucial parameter to understand its fate in soil after spreading and to assess the risk associated with agricultural recycling of OW. Here, we investigated changes in Zn speciat...
Poster presenting FAME-UHD: a bending magnet beamline specialized in high energy resolution X-ray absorption and emission spectroscopy. FAME-UHD (BM16) is part of the French CRG pool of beamlines located at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France.
In many deposits of hydrothermal origin arsenian pyrites host industrial concentrations of Au with direct correlation between Au and As contents. The aim of our study is to characterize the state of Au in arsenian pyrite by means of X-ray absorption spectroscopy. For this purpose, we synthesized Au-bearing pure and arsenian pyrites using hydrotherm...
Plant leaves serve both as a sink for gaseous elemental mercury (Hg) from the atmosphere and a source of toxic mercury to terrestrial ecosystems. Litterfall is the primary deposition pathway of atmospheric Hg to vegetated soils, yet the chemical form of this major Hg input remains elusive. We report the first observation of in vivo formation of mer...
The nanoscale distribution of magnetic anisotropies is measured in core@shell MnFe2O4@CoFe2O4 7.0 nm particles using a combination of element selective magnetic spectroscopies with different probing depths. As this picture is not accessible by any other technique, emergent magnetic properties are revealed. The coercive field is not constant in a wh...
The study of the speciation of highly-diluted elements is experimentally extremely challenging, especially in environmental and geochemistry sciences. Here we present an innovative synchrotron spectroscopy technique, namely high energy resolution fluorescence detected X-ray absorption spectroscopy (HERFD-XAS). Within this approach the XAS signal in...
The study of the speciation of highly diluted elements by X-ray absorption spectroscopy (XAS) is extremely challenging, especially in environmental biogeochemistry sciences. Here we present an innovative synchrotron spectroscopy technique: high-energy resolution fluorescence detected XAS (HERFD-XAS). With this approach, measurement of the XAS signa...
Magnetic anisotropies in a ferrofluid of core@shell MnFe2O4@CoFe2O4 nanoparticles are studied in the liquid and frozen states using a unique sample cell developed for element specific hard X-ray magnetic spectroscopies. The MnFe2O4@CoFe2O4 6.7 nm particles reveal original magnetic properties, with a gradient in coercive field inside a nanospinel. T...
The valence and spin state evolution of Mn and Co on TbMn$_{\rm 1-x}$Co$_{\rm x}$O$_3$ series is precisely determined by means of soft and hard x-ray absorption spectroscopy (XAS) and K$\beta$ x-ray emission spectroscopy (XES). Our results show the change from Mn$^{3+}$ to Mn$^{4+}$ both high-spin (HS) together with the evolution from Co$^{2+}$ HS...
We present the development, manufacturing and performance of spherically bent crystal analyzers (SBCAs) of 100 mm diameter and 0.5 m bending radius. The elastic strain in the crystal wafer is partially released by a "strip-bent" method where the crystal wafer is cut in strips prior to the bending and the anodic bonding process. Compared to standard...
The valence and spin state evolution of Mn and Co on TbMn$_{\rm 1-x}$Co$_{\rm x}$O$_3$ series is precisely determined by means of soft and hard x-ray absorption spectroscopy (XAS) and K$\beta$ x-ray emission spectroscopy (XES). Our results show the change from Mn$^{3+}$ to Mn$^{4+}$ both high-spin (HS) together with the evolution from Co$^{2+}$ HS...
Mercury 5d-orbitals are involved in intramolecular π-interactions with carbon and sulfur nearest and next-nearest neighbors in mercury-aryl complexes. This unexpected character of the electron cloud of mercury was revealed by high energy-resolution XANES spectroscopy readily interpreted in terms of a final-state local (l,m)-projected density of sta...
Combined high-resolution fluorescence detection X-ray absorption near-edge spectroscopy, X-ray diffraction, and X-ray emission spectroscopy have been employed under operando conditions to obtain detailed new insight into the nature of the Mo species on zeolite ZSM-5 during methane dehydroaromatization. The results show that isolated Mo-oxo species...
We present results obtained from high energy-resolution L3-edge XANES spectroscopy and first-principles calculations for the structure, bonding, and stability of mercury(II) complexes with thiolate and thioether ligands in crystalline compounds, aqueous solution, and macromolecular natural organic matter (NOM). Core-to-valence XANES features that v...
Theoretical predictions show that depending on the populations of the Fe 3d
xy
, 3d
xz
, and 3d
yz
orbitals two possible quintet states can exist for the high-spin state of the photoswitchable model system [Fe(terpy)2]2+. The differences in the structure and molecular properties of these 5B2 and 5E quintets are very small and pose a substantial...
Synchrotron radiation x-ray absorption and emission spectroscopy techniques,
complemented by high-resolution transmission electron microscopy methods and
density functional theory calculations are employed to investigate the effect
of Mn in Al$_{x}$Ga$_{1-x}$N:Mn samples with an Al content up to 100%. The
atomic and electronic structure of Mn is es...
High energy resolution fluorescence-detected x-ray absorption spectroscopy and density functional theory calculations were used to investigate the local bonding and electronic structure of Sc in epitaxial wurtzite-structure ScxGa1-xN films with x ≤ 0.059. Sc atoms are found to substitute for Ga atoms, accompanied by a local distortion involving an...
The combination of x-ray spectroscopy methods complemented with theoretical
analysis unravels the coexistence of paramagnetic and antiferromagnetic phases
in the Zn_0.9Mn_0.1O shell deposited onto array of wurtzite ZnO nanowires. The
shell is crystalline with orientation toward the ZnO growth axis, as
demonstrated by X-ray linear dichroism. EXAFS a...
Building a detailed understanding of the structure function relationship is a crucial step in the optimization of molecular photocatalysts employed in water splitting schemes. The optically dark nature of their active sites usually prevents a complete mapping of the photoinduced dynamics. In this work, transient X-ray absorption spectroscopy highli...
We report on extending hard X-ray emission spectroscopy (XES) along with resonant inelastic X-ray scattering (RIXS) to study ultrafast phenomena in a pump-probe scheme at MHz repetition rates. The investigated systems include low-spin (LS) FeII complex compounds, where optical pulses induce a spin-state transition to their (sub)nanosecond-lived hig...
Particle size and support effects were determined for the hydrogenation of nitrobenzene over gold supported on alumina and titania by kinetic experiments, TEM and in situ high energy resolution fluorescence detected X-ray absorption spectroscopy (HERFD XAS). Especially when supported on alumina, the catalytic activity correlated well with the fract...
Owing to the variety of possible charge and spin states and to the different ways of coupling to the environment, paramagnetic centres in wide band-gap semiconductors and insulators exhibit a strikingly rich spectrum of properties and functionalities, exploited in commercial light emitters and proposed for applications in quantum information. Here...
Supplementary Information
This document reports the x-ray powder diffraction main reflections
(intensity threshold >= 100) for possible Fe-related phases forming during the
metal-organic vapor phase epitaxy (MOVPE) growth of Fe in NH_3/H_2 mixture on
wurtzite-GaN/sapphire. The 2\theta values are given for Cu K\alpha_1 radiation
(1.5406 \AA) in the range 25-100 deg (ordered...
We present an EXAFS study of the Mn atomic environment in Mn-doped GaAs nanowires. Mn doping has been obtained either via the diffusion of the Mn used as seed for the nanowire growth or by providing Mn during the growth of Au-induced wires. As a general finding, we observe that Mn forms chemical bonds with As but is not incorporated in a substituti...
We use extensive first principle simulations to show the major role played by
interfaces in the mechanism of phase separation observed in semiconductor
multifunctional materials. We make an analogy with the precipitation sequence
observed in over-saturated AlCu alloys, and replace the Guinier-Preston zones
in this new context. A new class of materi...
The sign, magnitude, and range of the exchange couplings between pairs of Mn ions is determined for (Ga,Mn)N and (Ga,Mn)N:Si with x≲3%. The samples have been grown by metalorganic vapor phase epitaxy and characterized by secondary-ion mass spectroscopy; high-resolution transmission electron microscopy with capabilities allowing for chemical analysi...
The effect of Mg codoping and Mg deposition mode on the Fe distribution in (Ga,Fe)N layers grown by metal-organic vapor phase epitaxy is investigated. Both homogeneously and digitally Mg-codoped samples are considered and contrasted to the case of (Ga,Fe)N layers obtained without any codoping by shallow impurities. The structural analysis of the la...
We report on the structural properties of Ge1−xMnx layers grown by molecular-beam epitaxy. In these layers, nanocolumns with a high Mn content are embedded in an almost-pure Ge matrix. We have used grazing-incidence x-ray scattering, atomic force and transmission electron microscopy to study the structural properties of the columns. We demonstrate...
Systematic investigations of the structural and magnetic properties of single crystal Ga1−xMnxN films grown by metal organic vapor phase epitaxy are presented. High-resolution transmission electron microscopy, synchrotron x-ray diffraction, and extended x-ray absorption fine structure studies do not reveal any crystallographic phase separation and...
InAs nanowires have been grown by molecular beam epitaxy using Mn as growth catalyst. Nanowires (NWs) have been obtained on SiO(2) and oxidized GaAs for growth temperatures in the range of 370-410 degrees C. The growth temperature is found to be the same as that of the growth of Au-catalyzed InAs wires. These results suggest that the InAs NWs grow...