Adsorption of iodine in metal-organic framework materials.

Nuclear power will continue to provide energy for the foreseeable future, but it can pose significant challenges in terms of the disposal of waste and potential release of untreated radioactive substances. Iodine is a volatile product from uranium fission and is particularly problematic due to its solubility. Different isotopes of iodine present different issues for people and the environment.

Recent advances in analysis of trace elements in environmental samples by X-ray based techniques (IUPAC Technical Report).

Trace elements analysis is a fundamental challenge in environmental sciences. Scientists measure trace elements in environmental media in order to assess the quality and safety of ecosystems and to quantify the burden of anthropogenic pollution. Among the available analytical techniques, X-ray based methods are particularly powerful, as they can quantify trace elements .

Coherent Tabletop EUV Ptychography of Nanopatterns.

Coherent diffraction imaging (CDI) or lensless X-ray microscopy has become of great interest for high spatial resolution imaging of, e.g., nanostructures and biological specimens.

Fate of Lu(III) sorbed on 2-line ferrihydrite at pH 5.7 and aged for 12 years at room temperature. II: insights from STEM-EDXS and DFT calculations.

Transformation products of two-line ferrihydrite associated with Lu(III) were studied after 12 years of aging using aberration-corrected high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), high-efficiency energy-dispersive X-ray spectroscopy (EDXS), and density functional theory (DFT). The transformation products consisted of hematite nanoparticles with overgrown goethite needles. High-efficiency STEM-EDXS revealed that Lu is only associated with goethite needles, and atomic-resolution HAADF-STEM reveals structural incorporation of Lu within goethite, partially replacing structural Fe sites.

Characterisation, coverage, and orientation of functionalised graphene using sum-frequency generation spectroscopy.

We report the unambiguous detection of phenyl groups covalently attached to functionalised graphene using non-linear spectroscopy. Sum-frequency generation was employed to probe graphene on a gold surface after chemical functionalisation using a benzene diazonium salt. We observe a distinct resonance at 3064 cm-1 which can clearly be assigned to an aromatic C-H stretch by comparison with a self-assembled monolayer on a gold substrate formed from benzenethiol.

CAT-ACT-A new highly versatile x-ray spectroscopy beamline for catalysis and radionuclide science at the KIT synchrotron light facility ANKA.

CAT-ACT-the hard X-ray beamline for CATalysis and ACTinide/radionuclide research at the KIT synchrotron radiation facility ANKA-is dedicated to X-ray spectroscopy, including "flux hungry" photon-in/photon-out and correlative techniques and combines state-of-the-art optics with a unique infrastructure for radionuclide and catalysis research. Measurements can be performed at photon energies varying between 3.4 keV and 55 keV, thus encompassing the actinide M- and L-edge or potassium K-edge up to the K-edges of the lanthanide series such as cerium.

Coherent diffractive imaging of graphite nanoparticles using a tabletop EUV source.

Structural information of nanostructures plays a key role in synthesis of novel nano-sized materials for promising applications such as high-performance nanoelectronics and nanophotonics. In this study, we apply for the first time the state-of-the-art coherent diffractive imaging method to characterize the structure of graphite nanoparticles. A sample with nanographites on a SiN support was exposed to 30 nm radiation from a tabletop laser-driven high-order harmonic generation extreme ultraviolet (EUV) source.

Confinement of Iodine Molecules into Triple-Helical Chains within Robust Metal-Organic Frameworks.

During nuclear waste disposal process, radioactive iodine as a fission product can be released. The widespread implementation of sustainable nuclear energy thus requires the development of efficient iodine stores that have simultaneously high capacity, stability and more importantly, storage density (and hence minimized system volume). Here, we report high I adsorption in a series of robust porous metal-organic materials, MFM-300(M) (M = Al, Sc, Fe, In).

The role of the 5f valence orbitals of early actinides in chemical bonding.

One of the long standing debates in actinide chemistry is the level of localization and participation of the actinide 5f valence orbitals in covalent bonds across the actinide series. Here we illuminate the role of the 5f valence orbitals of uranium, neptunium and plutonium in chemical bonding using advanced spectroscopies: actinide M HR-XANES and 3d4f RIXS. Results reveal that the 5f orbitals are active in the chemical bonding for uranium and neptunium, shown by significant variations in the level of their localization evidenced in the spectra.

Hydrophilic 2,9-bis-triazolyl-1,10-phenanthroline ligands enable selective Am(iii) separation: a step further towards sustainable nuclear energy.

The first hydrophilic, 1,10-phenanthroline derived ligands consisting of only C, H, O and N atoms for the selective extraction of Am(iii) from spent nuclear fuel are reported herein. One of these 2,9-bis-triazolyl-1,10-phenanthroline (BTrzPhen) ligands combined with a non-selective extracting agent, was found to exhibit process-suitable selectivity for Am(iii) over Eu(iii) and Cm(iii), providing a clear step forward.

First structural characterization of Pa(iv) in aqueous solution and quantum chemical investigations of the tetravalent actinides up to Bk(IV): the evidence of a curium break.

More than a century after its discovery the structure of the Pa(4+) ion in acidic aqueous solution has been investigated for the first time experimentally and by quantum chemistry. The combined results of EXAFS data and quantum chemically optimized structures suggest that the Pa(4+) aqua ion has an average of nine water molecules in its first hydration sphere at a mean Pa-O distance of 2.43 Å.

Nature and reactivity of layered double hydroxides formed by coprecipitating Mg, Al and As(V): Effect of arsenic concentration, pH, and aging.

Arsenic (As) co-precipitation is one of the major processes controlling As solubility in soils and waters. When As is co-precipitated with Al and Mg, the possible formation of layered double hydroxides (LDHs) and other nanocomposites can stabilize As in their structures thus making this toxic element less available. We investigated the nature and reactivity of Mg-Al-arsenate [As(V)] co-precipitated LDHs formed in solution affected by As concentration, pH, and aging.

Regioselective Synthesis of V-Shaped Bistriazinyl-phenanthrolines.

A new, regioselective synthesis of V-shaped 2,9-bis(6-(4-halophenyl)-1,2,4-triazin-3-yl)-1,10-phenanthrolines (4XPhBTPhen) ligands was developed, creating access to a simple and reliable synthesis of precursors for future supramolecular actinide complexing systems. Described is a reactant-directed regioselective synthetic method, which was found to be high yielding and reliable and yields exclusively 6,6'-phenyl BTPhen derivatives (including 4-chloro and 4-bromo) in five simple steps. Molecular and crystal structures of PhBTP and PhBTPhen products are fully determined and both were found to be in space group C2/c.

Micro-distribution of uranium in bone after contamination: new insight into its mechanism of accumulation into bone tissue.

After internal contamination, uranium rapidly distributes in the body; up to 20 % of the initial dose is retained in the skeleton, where it remains for years. Several studies suggest that uranium has a deleterious effect on the bone cell system, but little is known regarding the mechanisms leading to accumulation of uranium in bone tissue. We have performed synchrotron radiation-based micro-X-ray fluorescence (SR μ-XRF) studies to assess the initial distribution of uranium within cortical and trabecular bones in contaminated rats' femurs at the micrometer scale.

Polarization dependent high energy resolution X-ray absorption study of dicesium uranyl tetrachloride.

Dicesium uranyl tetrachloride (Cs2UO2Cl4) has been a model compound for experimental and theoretical studies of electronic structure of U(VI) in the form of UO2(2+) (uranyl ion) for decades. We have obtained angle-resolved electronic structure information for oriented Cs2UO2Cl4 crystal, specifically relative energies of 5f and 6d valence orbitals probed with extraordinary energy resolution by polarization dependent high energy resolution X-ray absorption near edge structure (PD-HR-XANES) and compare these with predictions from quantum chemical Amsterdam density functional theory (ADF) and ab initio real space multiple-scattering Green's function based FEFF codes. The obtained results have fundamental value but also demonstrate an experimental approach, which offers great potential to benchmark and drive improvement in theoretical calculations of electronic structures of actinide elements.

Synchrotron applications to f-element research in the nuclear fuel cycle.

Synchrotron-based techniques are increasingly used to characterize radioactive materials and elucidate determinant processes relevant to the nuclear fuel cycle. Many recent advances are driven by the need to characterize such materials with high resolution, for example spatial resolution for studies of localized components of heterogeneous systems and energy resolution for characterising the 5f-element oxidation state. Examples of synchrotron-based investigations into f-element chemistry are presented, which illustrate utilizing such high resolution, while pointing out various aspects of synchrotron R&D related to the nuclear fuel cycle.

6-(Tetrazol-5-yl)-2,2'-bipyridine: a highly selective ligand for the separation of lanthanides(III) and actinides(III).

The coordination structure in the solid state and solution complexation behavior of 6-(tetrazol-5-yl)-2,2'-bipyridine (HN4bipy) with samarium(III) was investigated as a model system for actinide(III)/lanthanide(III) separations. Two different solid 1:2 complexes, [Sm(N4bipy)2(OH)(H2O)2] (1) and [Sm(N4bipy)2(HCOO)(H2O)2] (2), were obtained from the reaction of samarium(III) nitrate with HN4bipy in isopropyl alcohol, resuspension in N,N-dimethylformamide (DMF), and slow crystallization. The formate anion coordinated to samarium in 2 is formed by decomposition of DMF to formic acid and dimethylamine.

Electrolyte layering at the calcite(104)-water interface indicated by Rb(+)- and Se(VI) K-edge resonant interface diffraction.

Calcite-water interface reactions are of major importance in various environmental settings as well as in industrial applications. Here we present resonant interface diffraction results on the calcite(104)-aqueous solution interface, measured in solutions containing either 10 mmol L(-1) RbCl or 0.5 mmol L(-1) Se(VI).

Hydration properties and ionic radii of actinide(III) ions in aqueous solution.

Ionic radii of actinide(III) cations (from U(III) to Cf(III)) in aqueous solution have been derived for the first time starting from accurate experimental determination of the ion-water distances obtained by combining extended X-ray absorption fine structure (EXAFS) results and molecular dynamics (MD) structural data. A strong analogy has been found between the lanthanide and actinide series concerning hydration properties. The existence of a contraction of the An-O distance along the series has been highlighted, while no decrease of the hydration number is evident up to Cf(III).

Evidence for covalence in a N-donor complex of americium(III).

The molecular origin of the selectivity of N-donor ligands, such as alkylated bis-triazinyl pyridines (BTPs), for actinide complexation in the presence of lanthanides is still largely unclear. NMR investigations of an Am(nPrBTP)3(3+) complex with a (15)N labelled ligand showed that it exhibits large differences in (15)N chemical shift for coordinating N-atoms in comparison to both lanthanide(III) complexes and the free ligand. The temperature dependence of NMR chemical shifts observed for this complex indicates a weak paramagnetism.

Oxidation state delineation via U L(III)-edge XANES in a series of isostructural uranium coordination complexes.

We present an X-ray absorption near-edge structure (XANES) study of a series of uranium coordination complexes that possess nearly identical first coordination spheres and geometries in a range of oxidation states from U(III) to U(VI). These compounds were obtained through the activation of small molecules, such as ketones, azides, and carbon dioxide, and upon oxidation of a high-valent U(V)≡O to [U(VI)≡O](+). Most of the compounds have been reported previously.

The INE-Beamline for actinide science at ANKA.

Since its inauguration in 2005, the INE-Beamline for actinide research at the synchrotron source ANKA (KIT North Campus) provides dedicated instrumentation for x-ray spectroscopic characterization of actinide samples and other radioactive materials. R&D work at the beamline focuses on various aspects of nuclear waste disposal within INE's mission to provide the scientific basis for assessing long-term safety of a final nuclear waste repository. The INE-Beamline is accessible for the actinide and radiochemistry community through the ANKA proposal system and the European Union Integrated Infrastructure Initiative ACTINET-I3.

2,6-Bis(5-(2,2-dimethylpropyl)-1H-pyrazol-3-yl)pyridine as a ligand for efficient actinide(III)/lanthanide(III) separation.

The N-donor complexing ligand 2,6-bis(5-(2,2-dimethylpropyl)-1H-pyrazol-3-yl)pyridine (C5-BPP) was synthesized and screened as an extracting agent selective for trivalent actinide cations over lanthanides. C5-BPP extracts Am(III) from up to 1 mol/L HNO(3) with a separation factor over Eu(III) of approximately 100. Due to its good performance as an extracting agent, the complexation of trivalent actinides and lanthanides with C5-BPP was studied.

Structure and reactivity of the calcite-water interface.

The zetapotential of calcite in contact with aqueous solutions of varying composition is determined for pre-equilibrated suspensions by means of electrophoretic measurements and for non-equilibrium solutions by means of streaming potential measurements. Carbonate and calcium are identified as charge determining ions. Studies of the equilibrium solutions show a shift of isoelectric point with changing CO(2) partial pressure.