I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[8211]
Open Access
Abstract: The neutral, distorted octahedral complex [TiCl4(SenBu2)2] (1), prepared from the reaction of TiCl4 with the neutral SenBu2 in a 1:2 ratio and characterized by IR and multinuclear (1H, 13C{1H}, 77Se{1H}) NMR spectroscopy and microanalysis, serves as an efficient single-source precursor for low-pressure chemical vapor deposition (LPCVD) of titanium diselenide, TiSe2, films onto SiO2 and TiN substrates. X-ray diffraction patterns on the deposited films are consistent with single-phase, hexagonal 1T-TiSe2 (P3̅m1), with evidence of some preferred orientation of the crystallites in thicker films. The composition and structural morphology was confirmed by scanning electron microscopy (SEM), energy dispersive X-ray, and Raman spectroscopy. SEM imaging shows hexagonal plate crystallites growing perpendicular to the substrate, but these tend to align parallel to the surface when the quantity of reagent is reduced. The resistivity of the crystalline TiSe2 films is 3.36 ± 0.05 × 10–3 Ω·cm with a carrier density of 1 × 1022 cm–3. Very highly selective film growth from the reagent was observed onto photolithographically patterned substrates, with film growth strongly preferred onto the conducting TiN surfaces of SiO2/TiN patterned substrates. TiSe2 is selectively deposited within the smallest 2 μm diameter TiN holes of the patterned TiN/SiO2 substrates. The variation in crystallite size with different diameter holes is determined by microfocus X-ray diffraction and SEM, revealing that the dimensions increase with the hole size, but that the thickness of the crystals stops increasing above ∼20 μm hole size, whereas their lengths/widths continue to increase.
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Nov 2013
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[7755, 3895]
Open Access
Abstract: The use of fluorescence full spectral micro-X-ray absorption near-edge structure (µXANES) mapping is becoming more widespread in the hard energy regime. This experimental method using the Ca K-edge combined with micro-X-ray diffraction (µXRD) mapping of the same sample has been enabled on beamline I18 at Diamond Light Source. This combined approach has been used to probe both long- and short-range order in calcium carbonate granules produced by the earthworm Lumbricus terrestris. In granules produced by earthworms cultured in a control artificial soil, calcite and vaterite are observed in the granules. However, granules produced by earthworms cultivated in the same artificial soil amended with 500 p.p.m. Mg also contain an aragonite. The two techniques, µXRD and µXANES, probe different sample volumes but there is good agreement in the phase maps produced.
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Jan 2014
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I18-Microfocus Spectroscopy
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Nicholas
Edwards
,
Phillip
Manning
,
Uwe
Bergmann
,
Peter Lars
Larson
,
Bart
Van Dongen
,
William
Sellers
,
Samuel M
Webb
,
Dimosthenis
Sokaras
,
Roberto
Alonso-mori
,
Konstantin
Ignatyev
,
Holly
Barden
,
Arjen
Van Veelen
,
Jennifer
Anne
,
Victoria
Egerton
,
R A
Wogelius
Diamond Proposal Number(s):
[8597]
Open Access
Abstract: Large-scale Synchrotron Rapid Scanning X-ray Fluorescence (SRS-XRF) elemental mapping and X-ray absorption spectroscopy are applied here to fossil leaf material from the ∼50 Mya Green River Formation (USA) in order to improve our understanding of the chemistry of fossilized plant remains. SRS-XRF of fossilized animals has previously shown that bioaccumulated trace metals and sulfur compounds may be preserved in their original distributions and these elements can also act as biomarkers for specific biosynthetic pathways. Similar spatially resolved chemical data for fossilized plants is sparsely represented in the literature despite the multitude of other chemical studies performed. Here, synchrotron data from multiple specimens consistently show that fossil leaves possess chemical inventories consisting of organometallic and organosulfur compounds that: (1) map discretely within the fossils, (2) resolve fine scale biological structures, and (3) are distinct from embedding sedimentary matrices. Additionally, the chemical distributions in fossil leaves are directly comparable to those of extant leaves. This evidence strongly suggests that a significant fraction of the chemical inventory of the examined fossil leaf material is derived from the living organisms and that original bioaccumulated elements have been preserved in situ for 50 million years. Chemical information of this kind has so far been unknown for fossilized plants and could for the first time allow the metallome of extinct flora to be studied.
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Apr 2014
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I18-Microfocus Spectroscopy
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J.
Anne
,
Nicholas
Edwards
,
R A
Wogelius
,
A. R.
Tumarkin-deratzian
,
William
Sellers
,
Arjen
Van Veelen
,
U.
Bergmann
,
D.
Sokaras
,
R.
Alonso-mori
,
Konstantin
Ignatyev
,
Victoria
Egerton
,
Phillip
Manning
Open Access
Abstract: Current understanding of bone healing and remodelling strategies in vertebrates has traditionally relied on morphological observations through the histological analysis of thin sections. However, chemical analysis may also be used in such interpretations, as different elements are known to be absorbed and used by bone for different physiological purposes such as growth and healing. These chemical signatures are beyond the detection limit of most laboratory-based analytical techniques (e.g. scanning electron microscopy). However, synchrotron rapid scanningX-ray fluorescence (SRSXRF) is an elemental mapping technique that uniquely combines high sensitivity (ppm), excellent sample resolution (20100 µm) and the ability to scan large specimens (decimetre scale) approximately 3000 times faster than other mapping techniques. Here, we use SRSXRF combined with microfocus elemental mapping (220 µm) to determine the distribution and concentration of trace elements within pathological and normal bone of both extant and extinct archosaurs (Cathartes aura and Allosaurus fragilis). Results reveal discrete chemical inventories within different bone tissue types and preservation modes. Chemical inventories also revealed detail of histological features not observable in thin section, including fine structures within the interface between pathological and normal bone as well as woven texture within pathological tissue.
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Jul 2014
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B18-Core EXAFS
I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[4939]
Open Access
Abstract: The physicochemical state of a catalyst is a key factor in determining both activity and selectivity; however these materials are often not structurally or compositionally homogeneous. Here we report on the 3-dimensional imaging of an industrial catalyst, Mo- promoted colloidal Pt supported on carbon. The distribution of both the active Pt species and Mo promoter have been mapped over a single particle of catalyst using microfocus X-ray Fluorescence computed tomography. X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure revealed a mixed local coordination environment, including the presence of both metallic Pt clusters and Pt chloride species, but also no direct interaction between the catalyst and Mo promoter. We also report on the benefits of scanning μ-XANES computed tomography for chemical imaging, allowing for 2- and 3-dimensional mapping of the local electronic and geometric environment, in this instance for both the Pt catalyst and Mo promoter throughout the catalyst particle.
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Nov 2014
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[8861]
Abstract: Au(I) chloride species are important reactants and intermediates in various processes across the
chemical sciences and engineering. Structure and bonding in Au(I) species are often characterized by Xray
absorption spectroscopy (XAS), including measurements under reaction conditions. Previously
reported XA spectra for Au(I) chloride species have varied significantly, likely as a result of radiation
damage and/or partial disproportionation of [AuCl2]- ions, which are metastable under ambient
conditions. By monitoring the decomposition of tetrabutylammonium dichloroaurate(I), TBA[AuCl2], in
1,2-dichlorobenzene we have obtained a reliable X-ray absorption spectrum of [AuCl2]- ions by
combining the calculation of difference spectra with an extended X-ray absorption fine-structure
(EXAFS) determination of the solution composition. The results show that the X-ray absorption nearedge
structure (XANES) of [AuCl2]- is characterized by a weak Au 2p3/2 - 5d (white line) transition,
which agrees well with the spectrum predicted by electronic structure calculations using the FEFF8
code. Compared to [AuCl4]- the determined [AuCl2]- spectrum has several distinctive features of
diagnostic analytical value. A more detailed densities of states (DOS) analysis of the electronic structure
suggests that the weak white line arises from a hybrid Au 6s/5d DOS band that is partially occupied, up
to the level of the highest occupied molecular orbital (HOMO). Correlation of Cl coordination numbers
determined from the EXAFS with the intensity of the white line in the XANES indicates that the
decomposition is a primarily radiation-induced oxidation to Au(III) species with an average formula of
[AuCl3OH]-
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Dec 2014
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I18-Microfocus Spectroscopy
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Victoria
Egerton
,
R A
Wogelius
,
Mark A.
Norell
,
Nicholas
Edwards
,
William
Sellers
,
Uwe
Bergmann
,
Dimosthenis
Sokaras
,
Roberto
Alonso-mori
,
Konstantin
Ignatyev
,
Arjen
Van Veelen
,
Jennifer
Anné
,
Bart
Van Dongen
,
Fabien
Knoll
,
Phillip
Manning
Diamond Proposal Number(s):
[8597, 9488]
Open Access
Abstract: The preservation of fossils reflects the interplay of inorganic and organic chemical processes, which should be clearly differentiated to make interpretations about the biology of extinct organisms. A new coliiformes bird (mouse bird) from the [similar]50 million year old Green River Formation (Wyoming, USA) has here been analysed using synchrotron X-ray fluorescence and environmental scanning electron microscopy with an attached X-ray energy dispersive system (ESEM-EDS). The concentration and distribution of 16 elements (Si, P, S, Cl, K, Ca, Ti, Mg, Fe, Ni, Cu, Zn, As, Br, Ba, Hg) has been mapped for individual points on the sample. S, Cu and Zn map distinctly within visibly preserved feathers and X-ray Absorption Spectroscopy (XAS) shows that S and Cu within the feathers are organically bound in a similar manner to modern feathers. The morphological preservation of the feathers, on both macro- and microscopic scales, is variable throughout the fossil and the differences in the lateral microfacies have resulted in a morphological preservation gradient. This study clearly differentiates endogenous organic remains from those representing exogenous overprinted geochemical precipitates and illustrates the chemical complexity of the overall taphonomic process.
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Jan 2015
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[11043]
Open Access
Abstract: Heterogeneous catalysis performed in the liquid phase is an important type of catalytic process which is rarely studied in situ. Using microfocus X-ray fluorescence and X-ray diffraction computed tomography (μ-XRF-CT, μ-XRD-CT) in combination with X-ray absorption near-edge spectroscopy (XANES), we have determined the active state of a Mo-promoted Pt/C catalyst (NanoSelect) for the liquid-phase hydrogenation of nitrobenzene under standard operating conditions. First, μ-XRF-CT and μ-XRD-CT reveal the active state of Pt catalyst to be reduced, noncrystalline, and evenly dispersed across the support surface. Second, imaging of the Pt and Mo distribution reveals they are highly stable on the support and not prone to leaching during the reaction. This study demonstrates the ability of chemical computed tomography to image the nature and spatial distribution of catalysts under reaction conditions.
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Jul 2015
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[11043]
Abstract: Heterogeneous catalysis performed in the liquidphase is an important type of catalytic process whichisrarelystudied in situ. Using microfocus X-ray fluorescence and X-raydiffraction computed tomography (m-XRF-CT, m-XRD-CT) incombination with X-ray absorption near-edge spectroscopy(XANES), we have determined the active state of aMo-promoted Pt/C catalyst (NanoSelect) for the liquid-phasehydrogenation of nitrobenzene under standardoperatingconditions.First, m-XRF-CT and m-XRD-CT reveal the activestate of Pt catalyst to be reduced, noncrystalline,and evenlydispersed across the support surface.Second, imaging of the Ptand Mo distribution reveals they are highly stable on thesupport and not prone to leaching during the reaction. Thisstudy demonstrates the ability of chemical computed tomog-raphy to image the nature and spatial distribution of catalystsunder reaction conditions.
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Aug 2015
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[9488, 8597]
Open Access
Abstract: Bone remodelling is a crucial biological process needed to maintain elemental homeostasis. It is important to understand the trace elemental inventories that govern these processes as malfunctions in bone remodelling can have devastating effects on an organism. In this study, we use a combination of X-ray techniques to map, quantify, and characterise the coordination chemistry of trace elements within the highly remodelled bone tissues of extant and extinct Sirenia (manatees and dugongs). The dense bone structure and unique body chemistry of sirenians represent ideal tissues for studying both high remodelling rates as well as unique fossilisation pathways. Here, elemental maps revealed uncorrelated patterning of Ca and Zn within secondary osteons in both extant and fossil sirenians, as well as elevated Sr within the connecting canals of fossil sirenians. Concentrations of these elements are comparable between extant and fossil material indicating geochemical processing of the fossil bone has been minimal. Zn was found to be bound in the same coordination within the apatite structure in both extant and fossil bone. Accurate quantification of trace elements in extant material was only possible when the organic constituents of the bone were included. The comparable distributions, concentrations, and chemical coordination of these physiologically important trace elements indicate the chemistry of bone remodelling has been preserved for 19 million years. This study signifies the powerful potential of merging histological and chemical techniques in the understanding of physiological processes in both extant and extinct vertebrates.
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Mar 2016
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