An evidence of local structural disorder across spin-reorientation transition in DyFeO: an extended x-ray absorption fine structure (EXAFS) study.

The present work is aimed at exploring the local atomic structure modifications related to the spin reorientation transition (SRT) in DyFeO orthoferrite exploiting x-ray absorption fine structure (XAFS) spectroscopy. For this purpose we studied by XAFS the evolution of the local atomic structure around Fe and Dy as function of temperature (10-300 K) in a DyFeO sample having the SRT around 50-100 K. For sake of comparison we studied a YFeO sample having no SRT.

Gallium- and Iron-Pyoverdine Coordination Compounds Investigated by X-ray Photoelectron Spectroscopy and X-ray Absorption Spectroscopy.

Iron is an essential nutrient for nearly all forms of life, although scarcely available due to its poor solubility in nature and complex formation in higher eukaryotes. Microorganisms have evolved a vast array of strategies to acquire iron, the most common being the production of high-affinity iron chelators, termed siderophores. The opportunistic bacterial pathogen Pseudomonas aeruginosa synthesizes and secretes two siderophores, pyoverdine (PVD) and pyochelin (PCH), characterized by very different structural and functional properties.

The five-to-six-coordination transition of ferric human serum heme-albumin is allosterically-modulated by ibuprofen and warfarin: a combined XAS and MD study.

Human serum albumin (HSA) is involved physiologically in heme scavenging; in turn, heme-albumin (HSA-heme-Fe) displays globin-like properties. Here, the allosteric effect of ibuprofen and warfarin on the local atomic structure around the ferric heme-Fe (heme-Fe(III)) atom of HSA-heme-Fe (HSA-heme-Fe(III)) has been probed by Fe-K edge X-ray absorption spectroscopy (XAS). The quantitative analysis of the Fe-K edge extended X-ray absorption fine structure (EXAFS) signals and modeling of the near edge (XANES) spectral features demonstrated that warfarin and ibuprofen binding modify the local structure of the heme-Fe(III).

XAS study of lead speciation in a central Italy calcareous soil.

Purpose: The Pb absorption processes on a heavy textured calcareous soil, typical of central Italy, were studied using synchrotron X-ray absorption spectroscopy (XAS) in order to probe, at molecular scale, the structure and chemical nature of Pb in contaminated soils and achieve precise description of Pb ions localization into these contaminated soils.

Materials And Methods: In order to distinguish the role of the different components of soils in Pb retention, samples were prepared from the original soils removing the carbonate fractions, the organic matter, the metal oxides, or selecting the clay fractions. Then these samples were fortified with Pb simulating the natural interactions processes of heavy metal solutions with soils.

High yield synthesis of pure alkanethiolate-capped silver nanoparticles.

One-phase, one-pot synthesis of Ag(0) nanoparticles capped with alkanethiolate molecules has been optimized to easily achieve a pure product in quantitative yield. We report the synthesis of dodecanethiolate-capped silver particles and the chemophysical, structural, and morphologic characterization performed by way of UV-vis, (1)H NMR, and X-ray photoelectron (XPS) spectroscopies, X-ray powder diffraction (XRD) and X-ray absorption fine structure analysis (XFAS), electron diffraction and high-resolution transmission electron microscopy (HR-TEM), and scanning and transmission electron microscopy (SEM and TEM). Depending on the molar ratio of the reagents (dodecylthiosulphate/Ag(+)), the mean Ag(0) particle size D(XRD) is tuned from 4 to 3 nm with a narrow size distribution.

Treatment of EXAFS data taken in the fluorescence mode in non-linear conditions.

The aim of this work is to investigate the possibility of extracting correct structural parameters from fluorescence EXAFS data taken at high count rates with an energy-resolving detector. This situation is often encountered on third-generation synchrotron radiation sources which provide a high flux on the sample. Errors caused by pulse pile-up in the extraction of structural information have been quantified in a real experiment, and different approaches to the problem of data correction have been elaborated.

The ReflEXAFS station at the GILDA beamline (BM08) of ESRF.

The experimental station for measuring X-ray absorption spectra in total reflection geometry operative at the GILDA CRG beamline of ESRF is described. The main features of the station are shown, namely: the possibility of detecting very small signals from thin (a few ML) samples, of depositing thin films under controlled conditions and thermal treating the samples in order to study dynamical processes. Case studies are reported in order to show the performances of the apparatus.

Rietveld refinement on x-ray diffraction patterns of bioapatite in human fetal bones.

Bioapatite, the main constituent of mineralized tissue in mammalian bones, is a calcium-phosphate-based mineral that is similar in structure and composition to hydroxyapatite. In this work, the crystallographic structure of bioapatite in human fetuses was investigated by synchrotron radiation x-ray diffraction (XRD) and microdiffraction ( micro -XRD) techniques. Rietveld refinement analyses of XRD and micro -XRD data allow for quantitative probing of the structural modifications of bioapatite as functions of the mineralization process and gestational age.