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      Correlating Metal Poisoning with Zeolite Deactivation in an Individual Catalyst Particle by Chemical and Phase-Sensitive X-ray Microscopy**

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          Heterogeneities of individual catalyst particles in space and time as monitored by spectroscopy.

          Recent years have witnessed the introduction of spatiotemporal spectroscopy for the characterization of catalysts at work at previously unattainable resolution and sensitivity. They have revealed that heterogeneous catalysts are more heterogeneous than often expected. Dynamic changes in the nature of active sites, such as their distribution and accessibility, occur both between and within particles. Scientists now have micro- and nanospectroscopic methods at hand to improve the understanding of catalyst heterogeneities and exploit them in catalyst design. Here we review the latest developments within this lively field. The trends include detection of single particles or molecules, super-resolution imaging, the transition from two- to three-dimensional imaging, selective staining, integration of spectroscopy with electron microscopy or scanning probe methods, and measuring under realistic reaction conditions. Such experimental approaches change the hitherto somewhat static picture of heterogeneous catalysis into one that acknowledges that catalysts behave almost like living objects--explaining why many characterization methods from the life sciences are being incorporated into catalysis research.
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            Probing the structure of heterogeneous diluted materials by diffraction tomography.

            The advent of nanosciences calls for the development of local structural probes, in particular to characterize ill-ordered or heterogeneous materials. Furthermore, because materials properties are often related to their heterogeneity and the hierarchical arrangement of their structure, different structural probes covering a wide range of scales are required. X-ray diffraction is one of the prime structural methods but suffers from a relatively poor detection limit, whereas transmission electron analysis involves destructive sample preparation. Here we show the potential of coupling pencil-beam tomography with X-ray diffraction to examine unidentified phases in nanomaterials and polycrystalline materials. The demonstration is carried out on a high-pressure pellet containing several carbon phases and on a heterogeneous powder containing chalcedony and iron pigments. The present method enables a non-invasive structural refinement with a weight sensitivity of one part per thousand. It enables the extraction of the scattering patterns of amorphous and crystalline compounds with similar atomic densities and compositions. Furthermore, such a diffraction-tomography experiment can be carried out simultaneously with X-ray fluorescence, Compton and absorption tomographies, enabling a multimodal analysis of prime importance in materials science, chemistry, geology, environmental science, medical science, palaeontology and cultural heritage.
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              Biological applications of X-ray fluorescence microscopy: exploring the subcellular topography and speciation of transition metals.

               J F Fahrni (2007)
              Synchrotron X-ray fluorescence microscopy (SXRF) is a microanalytical technique for the quantitative mapping of elemental distributions. Among currently available imaging modalities, SXRF is the only technique that is compatible with fully hydrated biological samples such as whole cells or tissue sections, while simultaneously offering trace element sensitivity and submicron spatial resolution. Combined with the ability to provide information regarding the oxidation state and coordination environment of metal cations, SXRF is ideally suited to study the intracellular distribution and speciation of trace elements, toxic heavy metals and therapeutic or diagnostic metal complexes.

                Author and article information

                Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitslaan 99 3584 CG Utrecht (The Netherlands) E-mail: b.m.weckhuysen@ a.m.beale@
                Science Division, Diamond Light Source, Harwell Science and Innovation Campus Didcot, Oxon OX11 0DE (UK)
                Author notes

                B.M.W. and J.R.M. acknowledge ACTS-ASPECT and NWO (VENI) for funding. The authors thank Albemarle Catalysts for providing the FCC catalysts, Dr. I. Lezcano (Utrecht University) for help during the synchrotron-based experiments, and DUBBLE beamline in ESRF for the bulk XANES experiments. We thank Diamond Light Source for access to beamline I18 that contributed to the results presented herein.

                Supporting information for this article is available on the WWW under

                Angew Chem Int Ed Engl
                Angew. Chem. Int. Ed. Engl
                Angewandte Chemie (International Ed. in English)
                WILEY-VCH Verlag (Weinheim )
                03 June 2013
                25 April 2013
                : 52
                : 23
                : 5983-5987
                23616490 3749464 10.1002/anie.201210030
                Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

                Re-use of this article is permitted in accordance with the Creative Commons Deed, Attribution 2.5, which does not permit commercial exploitation.



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