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- 2017 (5) (entfernen)
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- Adsorption of phosphate (1)
- BAMline (1)
- BESSY (1)
- Biomedical applications (1)
- Catalysis (1)
- Coordination polymers (1)
- EXAFS (1)
- In situ (1)
- In situ characterization (1)
- Mechanochemistry (1)
Eingeladener Vortrag
- nein (1)
Currently great effort is made to find materials and technologies for the recycling of phosphate from wastewater.
Herein, we present an in-depth study of the Phosphate adsorption mechanism of a promising adsorber material, a Zn−Fe−Zr oxyhydroxide-based nanostructured precipitate. The behavior of the multicomponent nanomaterial, consisting of both crystalline and amorphous parts, is investigated via X-ray absorption fine structure spectroscopy and Mössbauer spectroscopy, revealing the importance of the nanostructured composition for the phosphate adsorption. We found evidence that adsorption takes place especially in the vicinity of iron sites in the amorphous part of the material.
In the quest for finding the ideal synchrotron-radiation-induced imaging method for the investigation of trace element distributions in human bone samples, experiments were performed using both a scanning confocal synchrotron radiation micro X-ray fluorescence (SR-mXRF) (FLUO beamline at ANKA) setup and a full-field color X-ray camera (BAMline at BESSY-II) setup. As zinc is a trace element of special interest in bone, the setups were optimized for its detection. The setups were compared with respect to count rate, required measurement time and spatial resolution. It was demonstrated that the ideal method depends on the element of interest. Although for Ca (a major constituent of the bone with a low energy of 3.69 keV for its K alpha XRF line) the color X-ray camera provided a higher resolution in the plane, for Zn (a trace element in bone) only the confocal SR-µXRF setup was able to sufficiently image the distribution.
Efficient water oxidation catalysts are required for the development of water splitting technologies. Herein, the synthesis of layered hybrid NiFephenylphosphonate compounds from metal acetylacetonate precursors and phenylphosphonic acid in benzyl alcohol, and their Oxygen evolution reaction performance in alkaline medium, are reported. The hybrid particles are formed by inorganic layers of NiO6 and FeO6 distorted octahedra separated by bilayers of the organic group, and template the Formation in situ of NiFe hydroxide nanosheets of sizes between 5 and 25 nm and thicknesses between 3 and 10 nm. X-ray absorption spectroscopy measurements suggest that the hybrid also acts as a template for the local structure of the metal sites in the active catalyst, which remain distorted after the transformation. Optimum electrocatalytic activity is achieved with the hybrid compound with a Fe content of 16%. The combination of the synergistic effect between Ni and Fe with the structural properties of the hybrid results in an efficient catalyst that generates a current density of 10 mA cm−2 at an overpotential of 240 mV, and also in a stable catalyst that operates continuously at low overpotentials for 160 h.
New fluorinated coordination polymers were prepared mechanochemically by milling the alkaline earth metal hydroxides MII(OH)2·xH2O (MII: Ca, Sr) with tetrafluoroisophthalic acid (H2mBDC-F4). The structures of [{Ca(mBDC-F4)(H2O)2}·H2O] and [{Sr(mBDC-F4)(H2O)2}·H2O] were determined based on ab initio calculations and their powder X-ray diffraction (PXRD) data. The compounds are isomorphous and crystallize in the orthorhombic space group P212121. The determined structures were validated by using extended X-ray absorption (EXAFS) data. The new materials were thoroughly characterized using elemental analysis, thermal analysis, magic angle spinning NMR, and attenuated total reflection-infrared spectroscopy. Further characterization methods such as BET, dynamic vapor sorption, and scanning electron microscopy imaging were also used. Our investigations indicate that mechanochemistry is an efficient method for preparing such materials.
S2XAFS: Time-resolved X-ray absorption spectroscopy in a ‘single-shot’ – First in situ applications
(2017)
The newly developed EXAFS set-up comprises both time- and spatially-resolved EXAFS information simultaneously in a single-shot. This facile, stable and scanningless set-up was tested at the BAMline @ BESSY-II (Berlin, Germany). The pri-mary broadband beam is generated by a filter/X-ray-mirror combination (bandpass). The transmitted beam through the sample is diffracted by a convexly bent Si (111) crystal, producing a divergent beam. This, in turn, is collected by an area sensitive detector, in a theta - 2 theta geometry. The first in situ measurements were successfully carried out and hereby presented. The case-study deals with research on Zn-based Metal-Organic-Frameworks (MOFs) that have potential for medi-cal/pharmaceutical applications. This hot topic of MOF research targets encapsulation of therapeutically relevant bio-macromolecules (e.g. Enzymes) for drug delivery applications. Questions regarding the influence of proteins on the coor-dination of Zn during MOF crystal growth and within the final MOF can be answered with this new setup. We were able to track structural changes within a 1s time resolution.