Effect of carbon content on electronic structure of uranium carbides.

The electronic structure of UC[Formula: see text] (x = 0.9, 1.0, 1.

Presence of uranium(V) during uranium(VI) reduction by Desulfosporosinus hippei DSM 8344.

Microbial U(VI) reduction influences uranium mobility in contaminated subsurface environments and can affect the disposal of high-level radioactive waste by transforming the water-soluble U(VI) to less mobile U(IV). The reduction of U(VI) by the sulfate-reducing bacterium Desulfosporosinus hippei DSM 8344, a close phylogenetic relative to naturally occurring microorganism present in clay rock and bentonite, was investigated. D.

To form or not to form: PuO nanoparticles at acidic pH.

The aim of this study is to synthesize PuO nanoparticles (NPs) at low pH values and characterize the materials using laboratory and synchrotron-based methods. Properties of the PuO NPs formed under acidic conditions (pH 1-4) are explored here at the atomic scale. High-resolution transmission electron microscopy (HRTEM) is applied to characterize the crystallinity, morphology and size of the particles.

X-ray spectroscopic study of chemical state in uranium carbides.

UC and UMeC (Me = Fe, Zr, Mo) carbides were studied by the high-energy-resolution fluorescence-detected X-ray absorption (HERFD-XAS) technique at the U M and L edges. Both U M and L HERFD-XAS reveal some differences between UMeC and UC; there are differences also between the M and L edge results for both types of carbide in terms of the spectral width and energy position. The observed differences are attributed to the consequences of the U 5f, 6d-4d(3d) hybridization in UMeC.

Insights into the Electronic Structure of a U(IV) Amido and U(V) Imido Complex.

Reaction of the N-heterocylic carbene ligand PrIm (L ) and lithium bis(trimethylsilyl)amide (TMSA) as a base with UCl resulted in U(IV) and U(V) complexes. Uranium's +V oxidation state in (HL ) [U(V)(TMSI)Cl ] (TMSI=trimethylsilylimido) (2) was confirmed by HERFD-XANES measurements. Solid state characterization by SC-XRD and geometry optimisation of [U(IV)(L ) (TMSA)Cl ] (1) indicated a silylamido ligand mediated inverse trans influence (ITI).

X-ray studies bridge the molecular and macro length scales during the emergence of CoO assemblies.

The key to fabricating complex, hierarchical materials is the control of chemical reactions at various length scales. To this end, the classical model of nucleation and growth fails to provide sufficient information. Here, we illustrate how modern X-ray spectroscopic and scattering in situ studies bridge the molecular- and macro- length scales for assemblies of polyhedrally shaped CoO nanocrystals.

Enhanced Sorption of Radionuclides by Defect-Rich Graphene Oxide.

Extremely defect graphene oxide (dGO) is proposed as an advanced sorbent for treatment of radioactive waste and contaminated natural waters. dGO prepared using a modified Hummers oxidation procedure, starting from reduced graphene oxide (rGO) as a precursor, shows significantly higher sorption of U(VI), Am(III), and Eu(III) than standard graphene oxides (GOs). Earlier studies revealed the mechanism of radionuclide sorption related to defects in GO sheets.

Synthesis, Structural, and Electronic Properties of KPuO(CO): An Environmentally Relevant Plutonium Carbonate Complex.

The chemical properties of actinide materials are often predefined and described based on the data available for isostructural species. This is the case for potassium plutonyl () carbonate, KPuO(CO), a complex relevant for nuclear technology and the environment, of which the crystallographic and thermodynamic properties of which are still lacking. We report here the synthesis and characterization of achieved by single-crystal X-ray diffraction analysis and high-energy-resolution fluorescence-detected X-ray absorption near-edge structure at the Pu M-edge coupled with electronic structure calculations.

Signatures of technetium oxidation states: a new approach.

A general strategy for the determination of Tc oxidation state by new approach involving X-ray absorption near edge spectroscopy (XANES) at the Tc L3 edge is shown. A comprehensive series of 99Tc compounds, ranging from oxidation states I to VII, was measured and subsequently simulated within the framework of crystal-field multiplet theory. The observable trends in the absorption edge energy shift in combination with the spectral shape allow for a deeper understanding of complicated Tc coordination chemistry.

The missing pieces of the PuO nanoparticle puzzle.

The nanoscience field often produces results more mystifying than any other discipline. It has been argued that changes in the plutonium dioxide (PuO) particle size from bulk to nano can have a drastic effect on PuO properties. Here we report a full characterization of PuO nanoparticles (NPs) at the atomic level and probe their local and electronic structures by a variety of methods available at the synchrotron, including extended X-ray absorption fine structure (EXAFS) at the Pu L edge, X-ray absorption near edge structure (XANES) in high energy resolution fluorescence detection (HERFD) mode at the Pu L and M edges, high energy X-ray scattering (HEXS) and X-ray diffraction (XRD).

A multi-technique study of altered granitic rock from the Krunkelbach Valley uranium deposit, Southern Germany.

Herein, a multi-technique study was performed to reveal the elemental speciation and microphase composition in altered granitic rock collected from the Krunkelbach Valley uranium (U) deposit area near an abandoned U mine, Black Forest, Southern Germany. The former Krunkelbach U mine with 1-2 km surrounding area represents a unique natural analogue site with the rich accumulation of secondary U minerals suitable for radionuclide migration studies from a spent nuclear fuel (SNF) repository. Based on a micro-technique analysis using several synchrotron-based techniques such as X-ray fluorescence analysis, X-ray absorption spectroscopy, powder X-ray diffraction and laboratory-based scanning electron microscopy and Raman spectroscopy, the complex mineral assemblage was identified.

Nanoscopic X-ray imaging and quantification of the iron cellular architecture within single fibroblasts of Friedreich's ataxia patients.

Friedreich's ataxia (FRDA) is a neurodegenerative disease characterized by an increase in intracytoplasmic iron concentration. Here the nanoscale iron distribution within single fibroblasts from FRDA patients was investigated using synchrotron-radiation-based nanoscopic X-ray fluorescence and X-ray in-line holography at the ID16A nano-imaging beamline of the ESRF. This unique probe was deployed to uncover the iron cellular two-dimensional architecture of freeze-dried FRDA fibroblasts.

Towards the surface hydroxyl species in CeO nanoparticles.

Understanding the complex chemistry of functional nanomaterials is of fundamental importance. Controlled synthesis and characterization at the atomic level is essential to gain deeper insight into the unique chemical reactivity exhibited by many nanomaterials. Cerium oxide nanoparticles have many industrial and commercial applications, resulting from very strong catalytic, pro- and anti-oxidant activity.

Development and Applications of a Laboratory Micro X-ray Fluorescence (μXRF) Spectrometer Using Monochromatic Excitation for Quantitative Elemental Analysis.

The analytical characterization and an application example of a novel laboratory X-ray fluorescence (μXRF) microprobe is presented, which combines monochromatic, focused X-ray beam excitation with a high-performance silicon drift detector (SDD) and two-dimensional/three-dimensional (2D/3D) scanning capability. Because of the monochromatic excitation, below the (multiple) Compton/Rayleigh scattering peak region, the XRF spectra obtained by this laboratory spectrometer has similarly high peak-to-background ratios as those which can be obtained at synchrotron sources. However, the flux density difference between the proposed laboratory instrument and current synchrotron end stations is on the order of several orders of magnitude.

Full-field fluorescence mode micro-XANES imaging using a unique energy dispersive CCD detector.

X-ray absorption near-edge structure (XANES) spectroscopy is a well-known nondestructive technique that allows for chemical state and local structure determination. Spatially resolved oxidation state imaging is possible performing full-field transmission mode XANES experiments, providing chemical state information on the illuminated sample area, but these experiments are limited to thin, concentrated samples. Here we present the use of a unique energy dispersive (ED) pnCCD detector, the SLcam, for full-field fluorescence mode XANES experiments, thereby significantly relaxing the constraints on sample thickness.