I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[17053]
Abstract: Background: The bioavailable supply of copper to ruminants has long been problematic. Complexities in supply exist due to interactions with other dietary elements in the rumen, most notably with iron or molybdenum in combination with sulphur, which can result in copper binding preventing its absorption. The molybdenum-sulphur-copper interaction has been extensively studied over the years. However, very little is known about the iron-sulphur-copper interaction, especially its mode of action in the gastrointestinal tract. Methods In the present work digesta from the rumen and jejunum of sheep fed a high copper, sulphur and iron diet was analysed using X-ray absorption spectroscopy (XAS). Results: X-ray absorption fine structure (XAFS) and X-ray absorption near edge structure (XANES) indicated that all of the copper and iron had changed in bonding in the rumen and that the oxidation state of the elements had been reduced into a mix of Fe2+ & Fe3+ and Cu+ with some Cu0. Conclusion: The copper compounds were most likely to be thiol co-ordinated in line with Cu+ chemistry. Changes to the copper compounds took place in the jejunum, although thiols were still highly favoured the possible existence of a copper-iron-sulphur complex which also included oxygen and chloride was also observed. This possibly has some resemblance to the crystal structure of bornite.
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Jul 2022
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B18-Core EXAFS
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Hongman
Sun
,
Yu
Zhang
,
Chunfen
Wang
,
Mark A.
Isaacs
,
Ahmed I.
Osman
,
Yehong
Wang
,
David
Rooney
,
Youhe
Wang
,
Zifeng
Yan
,
Christopher M. A.
Parlett
,
Feng
Wang
,
Chunfei
Wu
Diamond Proposal Number(s):
[19850]
Abstract: Integrated carbon capture and utilization (ICCU) presents an ideal solution to address anthropogenic carbon dioxide (CO2) emissions from industry and energy sectors, facilitating CO2 capture and subsequent utilization through conversion into high-value chemicals, as opposed to current release into the atmosphere. Herein, we report the synergistic coupling of porous CaO, as a sorbent for CO2 capture, and Ni doped CeO2 nanorods, as catalytic sites for CO2 reduction. It is found that ceria is shown to possess the capacity for CO2 utilization, however, critically it only results in the generation of CO due to the weak CO-ceria bonding. The addition of Ni active sites gives rise to CH4 being the predominant product, via the strong interaction between Ni species and CO, which facilitates further reduction. Through tuning Ni loadings, we have evaluated the role of catalytic active site size, with a Ni loading of only 0.5 wt% providing optimal performance through the formation of sub-nanometer sized clusters. This near-atomic active site dispersion gives rise to CH4 productivity and selectivity of 1540 mmol g−1 Ni and 85.8%, respectively, with this optimal combination of catalyst and sorbent demonstrating high stability over 10 cycles of ICCU process. These observations in parallel with the synergistic coupling of earth-abundant, low-cost materials (CaO and Ni) will have broad implications on the design and implementation of high efficiency, cost-effective ICCU materials and processes.
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Jun 2022
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B22-Multimode InfraRed imaging And Microspectroscopy
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Diamond Proposal Number(s):
[25407]
Abstract: Mechanofluorochromic materials are of great significance for the fabrication of innovative sensors and optoelectronics. However, efficient mechanofluorochromic materials are rarely explored due to the deficiency of existing design strategies. Here, we demonstrate the incarceration of aggregation-induced emission (AIE) materials within metal-organic framework (MOF) single crystals to construct a composite system with turn-on mechanofluorochromism. A new type of AIE@MOF material was designed: integrating a zeolitic MOF (ZIF-71) and tetraphenylethylene (TPE, a topical AIE material) to generate a TPE@ZIF-71 system with exceptional turn-on type mechanofluorochromism. Using terahertz vibrational spectroscopy, we show the unique fluorochromism mainly emanates from the enhanced nanoconfinement effect exerted by ZIF-71 host on TPE guest under pressure. Compared with pure TPE, we demonstrate the nanoconfinement in AIE@MOF not only changes the TPE's turn-off type sensing behavior to a turn-on type, but boosts the original sensitivity markedly by tenfold. Significantly, because ZIF-71 prevents the spontaneous recrystallization of TPE upon unloading, this allows TPE@ZIF-71 to record the stress history. This is the first demonstration of the Guest@MOF system combining the concepts of AIE and MOF; its promising properties and potential engineering applications will stimulate new directions pertaining to luminescent stress sensors and smart optics.
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Jun 2022
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[19081]
Open Access
Abstract: The protective carapace of Skogsbergia lerneri, a marine ostracod, is scratch-resistant and transparent. The compositional and structural organisation of the carapace that underlies these properties is unknown. In this study, we aimed to quantify and determine the distribution of chemical elements and chitin within the carapace of adult ostracods, as well as at different stages of ostracod development, to gain insight into its composition. Elemental analyses included X-ray absorption near-edge structure, X-ray fluorescence and X-ray diffraction. Nonlinear microscopy and spectral imaging were performed to determine chitin distribution within the carapace. High levels of calcium (20.3%) and substantial levels of magnesium (1.89%) were identified throughout development. Amorphous calcium carbonate (ACC) was detected in carapaces of all developmental stages, with the polymorph, aragonite, identified in A-1 and adult carapaces. Novel chitin-derived second harmonic generation signals (430/5 nm) were detected. Quantification of relative chitin content within the developing and adult carapaces identified negligible differences in chitin content between developmental stages and adult carapaces, except for the lower chitin contribution in A-2 (66.8 ± 7.6%) compared to A-5 (85.5 ± 10%) (p = 0.03). Skogsbergia lerneri carapace calcium carbonate composition was distinct to other myodocopid ostracods. These calcium polymorphs and ACC are described in other biological transparent materials, and with the consistent chitin distribution throughout S. lerneri development, may imply a biological adaptation to preserve carapace physical properties. Realisation of S. lerneri carapace synthesis and structural organisation will enable exploitation to manufacture biomaterials and biomimetics with huge potential in industrial and military applications.
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Jun 2022
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I06-Nanoscience
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G.
Awana
,
R.
Fujita
,
A.
Frisk
,
P.
Chen
,
Q.
Yao
,
A. J.
Caruana
,
C. J.
Kinane
,
N.-J.
Steinke
,
S.
Langridge
,
P.
Olalde-Velasco
,
S. S.
Dhesi
,
G.
Van Der Laan
,
X. F.
Kou
,
S. L.
Zhang
,
T.
Hesjedal
,
D.
Backes
Diamond Proposal Number(s):
[23748]
Open Access
Abstract: An elegant approach to overcome the intrinsic limitations of magnetically doped topological insulators is to bring a topological insulator in direct contact with a magnetic material. The aspiration is to realize the quantum anomalous Hall effect at high temperatures where the symmetry-breaking magnetic field is provided by a proximity-induced magnetization at the interface. Hence, a detailed understanding of the interfacial magnetism in such heterostructures is crucial, yet its distinction from structural and magnetic background effects is a rather nontrivial task. Here, we combine several magnetic characterization techniques to investigate the magnetic ordering in
MnTe
/
Bi
2
Te
3
heterostructures. A magnetization profile of the layer stack is obtained using depth-sensitive polarized neutron reflectometry. The magnetic constituents are characterized in more detail using element-sensitive magnetic x-ray spectroscopy. Magnetotransport measurements provide additional information about the magnetic transitions. We find that the supposedly antiferromagnetic MnTe layer does not exhibit an x-ray magnetic linear dichroic signal, raising doubt that it is in its antiferromagnetic state. Instead, Mn seems to penetrate into the surface region of the
Bi
2
Te
3
layer. Furthermore, the interface between MnTe and
Bi
2
Te
3
is not abrupt, but extending over
∼
2.2
nm. These conditions are the likely reason that we do not observe proximity-induced magnetization at the interface. Our findings illustrate the importance of not solely relying on one single technique as proof for proximity-induced magnetism at interfaces. We demonstrate that a holistic, multitechnique approach is essential to gain a more complete picture of the magnetic structure in which the interface is embedded.
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May 2022
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[20076]
Abstract: X-ray standing-wave (XSW) excited photoelectron emission was used to measure the site-specific valence band (VB) for ½ monolayer (ML) Pt grown on a
SrTiO
3
(001) surface. The XSW induced modulations in the core level (CL), and VB photoemission from the surface and substrate atoms were monitored for three
h
k
l
substrate Bragg reflections. The XSW CL analysis shows the Pt to have a face-centered-cubic-like cube-on-cube epitaxy with the substrate. The XSW VB information compares well to a density functional theory calculated projected density of states from the surface and substrate atoms. Overall, this Letter represents a novel method for determining the contribution to the density of states by valence electrons from specific atomic surface sites.
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May 2022
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Abstract: High charge synthetic Na-Mica-2 has been synthesized by the NaCl melt method. The Na+ cations in the interlayer space of the clay have been exchanged with Eu3+ ions by a cation exchange reaction. The correct incorporation of Eu3+ and further characterization of its coordination environment and location within the clay, as well as its optical properties, have been studied by means of x-ray diffraction, x-ray absorption (XANES and EXAFS), thermogravimetry and luminescence. Different structural scenarios for the incorporation of europium have been proposed and evaluated.
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May 2022
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I11-High Resolution Powder Diffraction
I15-Extreme Conditions
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Diamond Proposal Number(s):
[14061, 17673, 16390]
Open Access
Abstract: The similar electronic structures of Bi3+ and Pb2+ have motivated researchers to explore bismuth-based perovskite compounds, which in the past decade has been further fuelled by the demand for developing lead-free piezoceramics. The difficulty in stabilizing the perovskite phase in bismuth based compounds has directed most research activities towards exploring two main compounds - multiferroic BiFeO3 and relaxor ferroelectric Na1/2Bi1/2TiO3 and their derivatives. In recent years, quenching these materials from the sintering temperature or from the paraelectric phase (above the Curie temperature, Tc) has resulted in a plethora of fundamentally interesting and technologically relevant advances, including enhanced thermal depolarization temperature, high Tc, giant strain and control over the atomic structure and electrical conductivity at the domain wall. In this contribution, a brief overview of quenching piezoceramics is presented, with majority of the discussion encompassing salient features of quenching lead-free perovskite structured Na1/2Bi1/2TiO3- and BiFeO3- based materials. For each material system, the influence of quenching on phase transitions, domain switching behavior and electromechanical properties are presented, apart from outlining the current understanding of the underlying mechanisms. The review provides guidelines for further exploration of the quenching strategy for improving the functionality of Bi-based piezoceramics.
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May 2022
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B22-Multimode InfraRed imaging And Microspectroscopy
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Open Access
Abstract: Motivation: With continually improved instrumentation, Fourier transform infrared (FTIR) microspectroscopy can now be used to capture thousands of high-resolution spectra for chemical characterisation of a sample. The spatially resolved nature of this method lends itself well to histological profiling of complex biological specimens. However, current software can make joint analysis of multiple samples challenging and, for large datasets, computationally infeasible. Results: To overcome these limitations, we have developed Photizo – an open-source Python library enabling high-throughput spectral data pre-processing, visualisation and downstream analysis, including principal component analysis, clustering, macromolecular quantification and mapping. Photizo can be used for analysis of data without a spatial component, as well as spatially-resolved data, obtained e.g. by scanning mode IR microspectroscopy and IR imaging by focal plane array (FPA) detector. Availability: The code underlying this article is available at https://github.com/DendrouLab/Photizo with access to example data available at https://zenodo.org/record/6417982#.Yk2O9TfMI6A.
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May 2022
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[16243]
Open Access
Abstract: A combined high resolution X-ray photoelectron spectroscopy and X-ray standing wave study into the adsorption structure of hydrogenated graphene on Ir(111) is presented. By exploiting the unique absorption profiles and significant modulations in signal intensity found within the X-ray standing wave results, we refine the fitting of the C 1s X-ray photoelectron spectra, allowing us to disentangle the contributions from hydrogenation of graphene in different high-symmetry regions of the moiré supercell. We clearly demonstrate that hydrogenation in the FCC regions results in the formation of a graphane-like structure, giving a standalone component that is separated from the component assigned to the similar structure in the HCP regions. The contribution from dimer structures in the ATOP regions is found to be minor or negligible. This is in contrast to the previous findings where a dimer structure was assumed to contribute significantly to the sp3 part of the C 1s spectra. The corrugation of the remaining pristine parts of the H-graphene is shown to increase with the H coverage, reflecting an increasing number and size of pinning centers of the graphene to the Ir(111) substrate with increasing H exposure.
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May 2022
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