B18-Core EXAFS
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Diamond Proposal Number(s):
[33047]
Open Access
Abstract: Human skeletal samples burned between 200 and 1000 °C, in both aerobic and anaerobic conditions, were probed by synchrotron-based Extended X-ray Absorption Fine Structure with a view to interpret heat-induced variations in chemical composition and structure. Heat-prompted changes in Ca2+ first and second coordination shells were unveiled (regarding PO43−, CO32− and/or OH− ligands). A higher crystallinity degree was found for 800-1000 °C burning temperatures as compared to 200-700 °C, in agreement with the higher amount of organic components in moderately heated samples. The unique local structural information delivered by XAS, particularly on the Ca2+ coordination environment which determines bone's structural features and degree of crystallinity, enabled an improved understanding of the heat-elicited changes undergone by bone, not previously accessed by other techniques. This is an innovative study, with a high impact in forensic and bioarchaeological research, focused on the analysis of burned human skeletal remains.
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Oct 2026
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Diamond Proposal Number(s):
[43895]
Open Access
Abstract: X-ray photoelectron spectroscopy (XPS) is a major technique in catalyst research due to its ability to determine chemical states on the surface. Near ambient pressure XPS (NAP-XPS) enables in situ analysis, offering valuable insight into catalytic processes. However, modern catalysts are often supported on non-conductive supports such as TiO2 or SiO2, which can present significant challenges for XPS analysis due to charging and differential charging. These issues can distort spectral data, rendering data unusable and wasting valuable instrument time. While several sample preparation strategies exist, many are limited by not allowing high temperature analysis, the risk of sample loss (e.g., from powder flaking off), or continued susceptibility to charging. In this work, we introduce a simple, robust, and time-efficient method for mounting catalyst powders by compressing them between aluminium foil disks. This approach provides excellent sample hold, minimises charging effects, and is suitable for high-temperature NAP-XPS analysis and synchrotron x-ray sources. The method addresses key limitations of conventional preparation techniques and enables more reliable characterisation of insulating catalyst materials.
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Aug 2026
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B18-Core EXAFS
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Diamond Proposal Number(s):
[30629]
Abstract: Geopolymer cements are highly promising materials for long-term immobilisation of Strontium-90 radioactive waste, offering superior durability and cation binding sites compared to conventional Portland cement matrices. This study investigates the influence of prolonged leaching on the Sr immobilisation mechanism and structural integrity of metakaolin-based geopolymers using the ANSI/ANS 16.1 semi-dynamic leaching test. All geopolymers demonstrated high Sr retention, with Leachability Indices at least 14.7 for all samples, significantly exceeding the industry guideline of 6.0, confirming their effectiveness. Importantly, potassium silicate–activated geopolymers exhibited reduced Sr release and substantially lower leaching rates than sodium silicate–activated geopolymers. Multiscale spectroscopic and diffractometric analysis, including synchrotron X-ray absorption spectroscopy and multinuclear high-field solid-state MAS NMR probing 39K, 23Na, 27Al, and 29Si, revealed that the alkali aluminosilicate gel framework remained structurally stable after leaching for 28 days, with no significant alterations to Si and Al bonding environments. Sr release is primarily controlled by diffusion, and the dominant immobilisation mechanism is the formation of insoluble SrCO3. Atomic-level Sr structural analysis using XANES/EXAFS revealed an increase in the average Sr coordination number in both systems after leaching, with a more pronounced rise in potassium-based geopolymers, consistent with enhanced SrCO3 formation. Overall, these findings demonstrate that geopolymers maintain structural integrity during leaching and show for the first time that using potassium rather than sodium as an alkali activator is definitively more advantageous for maximising the long-term effectiveness of geopolymer wasteforms. This demonstrates their strong suitability as wasteforms for the safe long-term immobilisation of Sr-containing radioactive wastes.
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Jul 2026
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B18-Core EXAFS
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Abstract: Industrial W-based olefin metathesis catalysts use silica as the support and generally show low activities. This is due to the difficulty in dispersing W species and in maintaining the structural integrity of W active centers on the silica surface. These catalysts also have poor W redox kinetics and slow olefin adsorption at reaction temperatures, which prohibits high reaction rates. Here, for the first time, we systematically demonstrate the dramatic multiple contributions from zeolite Y to the overall catalytic activity when it is used as the catalyst support. The high surface area and porous nature of zeolite Y can provide the isolation, immobilization, and confinement of W active centers. Isolated W active centers in zeolite Y show faster redox kinetics, which is crucial for olefin metathesis. Zeolite Y also facilitates rapid adsorption and isomerization of olefin substrates by its Brønsted acid sites for synergetic catalysis with W active centers.
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Jun 2026
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B18-Core EXAFS
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Diamond Proposal Number(s):
[37966]
Open Access
Abstract: With the ongoing interest in developing more stable and versatile catalysts for CO2 hydrogenation to methanol, molybdenum sulfide (MoS2) has been recently proposed as an alternative material. However, in its bulk state, CO2 hydrogenation over MoS2 typically favors methane formation. In this work, a wet impregnation method is applied for the production of ZnS-supported MoS2, as confirmed by characterization via X-ray Diffraction, Raman and X-ray Photoelectron Spectroscopy. In contrast with the negligible methanol production shown by the pure MoS2 reference, 2% MoS2/ZnS presents a methanol selectivity of 78% at a CO2 conversion of 2.3% under the mild reaction conditions of 200 °C and 20 bar. Density Functional Theory and Transmission Electron Microscopy suggest that the improved catalytic activity arises from an even dispersion of few-layer MoS2 with exposed basal plane sites at the ZnS surface, an arrangement possibly enabled by the structural similarity and the shared S atoms between 2H-MoS2 and W–ZnS phases. This hypothesis is strengthened by the comparison with the reference sample consisting of ZrO2-supported MoS2 sample, in which more agglomerated MoS2 particles resulted in a lower and less selective methanol production. Moreover, in situ X-ray absorption spectroscopy and H2 temperature-programmed reduction suggest further evidence of a MoS2/ZnS interaction during the H2 pretreatment, which may promote not only the expected formation of S-vacancies but also a partial reconstruction of MoS2 given the close contact and sharing of S atoms with the ZnS support.
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Jun 2026
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I05-ARPES
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Chan-Young
Lim
,
Francesc
Ballester
,
Arunava
Kar
,
Manex
Alkorta
,
David
Subires
,
Ji
Dai
,
Massimo
Tallarida
,
Elio
Vescovo
,
Timur K.
Kim
,
Cephise
Cacho
,
Changjiang
Yi
,
Subhajit
Roychowdhury
,
Avdhesh Kumar
Sharma
,
Yongseong
Choi
,
Gilberto
Fabbris
,
Joerg
Strempfer
,
Pierluigi
Gargiani
,
Chandra
Shekhar
,
Claudia
Felser
,
Ion
Errea
,
Maia G.
Vergniory
,
Santiago
Blanco-Canosa
Diamond Proposal Number(s):
[36505]
Abstract: Kagome materials are known for hosting emergent quantum phenomena driven by the interaction between different lattice, charge, and spin orders. Here, we present a detailed angle-resolved photoemission (ARPES), density functional theory (DFT), and x-ray magnetic circular dichroism (XMCD) study of the electronic and magnetic structure of 𝑅Ti3Bi4 (𝑅=Nd, Sm, Gd). ARPES and DFT demonstrate that the bulk electronic band structure is dominated by the hybridization of the Ti bands, and the weak electron-like pocket at Γ is identified as a surface state. The isotropic XAS profile of the 𝑀4,5 edge of the rare earth is consistent with the presence of the 𝑅3+ oxidation state. Using the XMCD sum rules, backed by the atomic-multiplet-theory calculations, we obtain the spin and orbital magnetic moments. The Ti 𝐿2,3-edge XMCD reveals the presence of a small magnetic moment in GdTi3Bi4, presumably driven by the proximity of the Ti kagome layers to the zigzag chains of Gd, while the total magnetic moment of Gd is shared by the 𝑓 and 𝑑 electrons. Our combined XMCD, ARPES, and DFT study provides an important piece of information to understand the spin-flip transitions and anomalous Hall effect observed in the 𝑅Ti3Bi4 kagome metals.
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Jun 2026
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B18-Core EXAFS
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Abstract: In recent years, the hydrogenation of CO2 into fuels and chemicals has gained increasing attention as a key technology for achieving a sustainable circular carbon economy. This research focuses on heterogeneous thermocatalytic hydrogenation of CO2 into value-added products containing carbon– carbon bonds (C–C coupled products). In recognition of the two subfields within thermocatalytic CO2 hydrogenation research, this thesis includes research related to both approaches.
Before laying out the findings of the current research, Chapter 1 of this thesis provides general background to the research described in Chapters 3, 4 and 5. Chapter 1 starts with a discussion of the societal relevance of the research. This is followed by a general discussion of CO2 hydrogenation catalysis including thermodynamics and orbital theory. Hereafter, more details are provided on the literature specifically relevant to the current research. This includes a separate discussion on direct and tandem CO2 conversion. The experimental methods are described in Chapter 2. After presenting the findings in Chapter 3, 4 and 5, final conclusion and suggestions for future research are briefly laid out in Chapter 5.
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Jun 2026
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B22-Multimode InfraRed imaging And Microspectroscopy
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Open Access
Abstract: Measuring live cells by FTIR spectroscopy is challenging due to their small size and the absorbance of water in the mid-IR region. However, measuring cells in their live state is important to observe changes in the biological processes of cells that are unaffected by fixation and drying processes. Recently, ZnS hemispheres were used to sandwich live cells in a 6 µm layer of cell medium, which simultaneously limit the absorbance of water and increase the spatial resolution by x2.25, thereby enabling high quality spectra to be acquired from living cells. So far, this method has been used as an imaging technique to showcase the distribution of biomolecules within a single cell. In this work, we present an alternative use of these ZnS hemispheres as a high throughput screening tool. We obtained high quality spectra of a single cell at a measurement rate of ∼1 min/cell. We’ve applied this technique to observe the biochemical effects of various polystyrene microplastics on two mammalian cell lines (J774A.1 and A549), however the method can easily be expanded to other cell lines, microplastics, and alternative xenobiotics.
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Jun 2026
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I05-ARPES
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Junhyeok
Jeong
,
Yamato
Enomoto
,
Yoshimitsu
Kohama
,
Tomotaka
Nakayama
,
Kotaro
Ando
,
Kifu
Kurokawa
,
Soonsang
Huh
,
Zhuo
Yang
,
Toshihiro
Nomura
,
Matthew D.
Watson
,
Timur K.
Kim
,
Cephise
Cacho
,
Chun
Lin
,
Makoto
Hashimoto
,
Donghui
Lu
,
Shiro
Sakai
,
Takami
Tohyama
,
Kazuyasu
Tokiwa
,
Takeshi
Kondo
Diamond Proposal Number(s):
[36822, 30646, 28930, 25416]
Open Access
Abstract: Fermi arcs observed in underdoped cuprates have sparked debate over whether they represent segments of a large Fermi surface or small Fermi pockets. This ambiguity has long hindered their classification as either the conventional Bardeen-Cooper-Schrieffer (BCS) regime or the strongly coupled Bose-Einstein condensation (BEC) crossover limit. Here, using angle-resolved photoemission spectroscopy and quantum oscillations, we demonstrate the coexistence of a small Fermi pocket and a large superconducting gap in the clean inner CuO2 layers of the four-layer cuprate Ba2Ca3Cu4O8(F,O)2. This coexistence constitutes a hallmark of the BCS-BEC crossover and has remained elusive for decades. Despite the presence of antiferromagnetic (AF) order, the superconducting gap in the small pocket is remarkably large, yielding a gap-to-Fermi energy ratio (Δpocket/εF ~ 0.6) and a critical-to-Fermi temperature ratio (Tc/TF ~ 0.13) that reach the theoretical upper bound for two-dimensional superconductivity. Unexpectedly, this BCS-BEC crossover emerges not as the carrier density decreases but as it increases, abruptly within a narrow doping range of less than 1%. These results provide a long-sought microscopic foundation for the d-wave pairing mechanism in doped AF-Mott insulators.
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Jun 2026
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B18-Core EXAFS
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Diamond Proposal Number(s):
[37961]
Open Access
Abstract: In the present work, we report the exsolution of CoFe nanoalloy nanoparticles from Co and Fe co-doped lanthanum aluminate perovskite oxide, LaAl0.90Co0.05Fe0.05O3, and assess the perovskite oxide as an oxygen reduction reaction (ORR) electrocatalyst. We optimized both intrinsic and extrinsic material properties of perovskites to achieve good electrocatalytic performance in the kinetic and mass-transfer controlled region. Firstly, we demonstrated that the near surface segregation of B-site cation (Co) under reducing environment at low temperature (at 500 °C), believed to represent the initial stage of exsolution, led to high ORR activity in the mass-controlled region, with specific and mass activities of 4.9 mA/cm2 and 37.5 A/g (@0.4 V versus RHE), respectively. Secondly, reducing the particle size of perovskite oxide increased surface exposure to the reducing environment promoting the CoFe nanoalloy particle exsolution. The results demonstrate that cation enrichment in subsurface region, near grain boundaries contributes more effectively to ORR activity than exsolution in the form of nanoparticles in this perovskite oxide composition. Nevertheless, achieving fast charge transfer-kinetics without the use of precious metals still remains a challenge with lanthanum aluminates, as indicated by onset potentials of 0.84 V and 0.81 V (versus RHE) for the pristine and reduced perovskite oxide, respectively. Notably, impregnation of perovskite oxide with 0.2 wt. % Pt followed by heat treatment in reducing atmosphere at 500 °C increased the onset potential to 0.9 V. Overall, this study suggests that non-precious metal-doped lanthanum aluminate, LaAl0.90Co0.05Fe0.05O3, exhibits strong electrocatalytic activity and is further enhanced through impregnation treatment.
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Jun 2026
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