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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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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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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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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B18-Core EXAFS
I18-Microfocus Spectroscopy
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Swaroop
Chakraborty
,
Iuliia
Mikulska
,
Rhiannon
Boseley
,
Sang
Pham
,
Prathmesh
Bhadane
,
Pankti
Dhumal
,
Santanu
Majumder
,
Jajati
Mandal
,
Tina
Geraki
,
Superb K.
Misra
,
Christian
Pfrang
,
Iseult
Lynch
Diamond Proposal Number(s):
[33674, 35117, 41674]
Open Access
Abstract: Metal–organic frameworks (MOFs) are increasingly deployed in environmental technologies, yet their fate and hazard under realistic multistep exposure scenarios remain poorly constrained. Here, we track hierarchical transformations of nanoscale ZIF-8 (Zeolitic Imidazolate Framework-8) across an exposure cascade spanning atmospheric aging (air and reactive gases O3/NO2), aqueous aging in environmentally and biologically relevant media, and ingestion by the freshwater crustacean Daphnia magna. Synchrotron Zn K-edge X-ray absorption spectroscopy (XAS), micro-X-ray fluorescence (μ-XRF), X-ray photoelectron spectroscopy (XPS), and electron microscopy show that gas-phase exposure produces only minor surface perturbations, whereas aqueous contact drives pronounced medium-dependent restructuring, including nitrogen depletion and oxygen enrichment at the surface and time-resolved dissolved Zn release with chemistry-imposed plateaus. In vivo, Zn speciation diverges from the pristine Zn–N fingerprint; an unexposed endogenous Zn baseline and linear combination fitting (LCF) indicate a mixture of endogenous Zn with transformed Zn pools dominated by O/P/S-type coordination environments. Acute ecotoxicity assay demonstrates strong concentration dependence (48 h immobilization EC50 ≈0.5 μg mL–1), and chronic exposure at 0.10 μg mL–1 reduces cumulative brood production with increased adult mortality over 24 days. Mechanistically, fractionated toxicity assays show that washed aged particles/precipitates and whole aged suspensions are more potent than particle-free filtrates, indicating that particle-associated transformed Zn pools contribute substantially beyond dissolved Zn alone. Together, these results show that ZIF-8 risk emerges from its sequential transformation trajectory rather than its pristine state, motivating tiered aging protocols coupled to in vivo speciation and fractionated hazard testing for MOF safety assessment.
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May 2026
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B18-Core EXAFS
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Niqab
Khan
,
Erick
Jo Prada
,
Mohammed A. M.
Bajiri
,
Washington
Santa Rosa
,
Flavio L.
Souza
,
Gazi N.
Aliev
,
Wolfgang
Theis
,
Heberton
Wender
,
Valmor R.
Mastelaro
,
Jesum
Alves Fernandes
,
Renato V.
Goncalves
Diamond Proposal Number(s):
[35043]
Open Access
Abstract: Photocatalytic hydrogen (H2) evolution offers a promising solution to environmental pollution and the global energy crisis. Among different photocatalysts, graphitic carbon nitride (g-C3N4), most known as melon in the literature, is distinguished by its availability, large surface area, low cost, and unique optical and electrical properties. However, the efficiency of pristine g-C3N4 is limited by rapid electron–hole recombination, presence of charged trapped states and high charge transference resistance. To overcome these challenges, we used a facile magnetron sputtering technique to load Cu and Pt single atoms onto g-C3N4, confirmed by AC-STEM, XPS, ICP-OES, and XAS characterizations. This approach not only overcomes the problems related to the charge carrier dynamics of the pristine graphitic carbon nitride but also ensures uniform, contamination-free deposition and high distribution of single atoms, thereby optimizing photocatalytic performance. Under solar irradiation (AM 1.5G) for 5 h, the Cu and Pt-loaded g-C3N4 demonstrated significantly improved photocatalytic activity, achieving H2 accumulated values of 93 μmol and 173 μmol, respectively, compared to only 0.3 μmol for pristine g-C3N4. For comparison, Pt and Cu nanoparticles (NPs)- loaded g-C3N4 samples were also prepared, achieving H2 accumulation values of 86.3 and 24.3 μmol, respectively, compared to pristine g-C3N4. However, these values are lower than those of Pt and Cu single-atom-loaded samples. The enhanced H2 evolution performance is attributed to the deposition of metal single atoms acting as electron traps and active catalytic sites, thus improving electron–hole separation. These findings highlight the potential of sputter depositing single-atom to overcome the inherent limitations of g-C3N4, paving the way for more efficient and scalable hydrogen production systems.
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May 2026
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I12-JEEP: Joint Engineering, Environmental and Processing
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Abstract: Amid rising global demand for renewable energy and effective plastic waste management, adopting green methods to utilize plastic waste for chemicals is a win–win strategy. Constituting the largest amount of single-use plastic litter worldwide, cellulose diacetate (CDA) based waste cigarette filters urgently require sustainable valorization pathways. However, CDA photoconversion remains highly challenging due to substantial energy barriers for selective bond cleavage, inadequate radical generation capability, and inefficient charge-carrier separation. Herein we propose a strategy to efficiently obtain C2H4 through carbene-mediated CDA photoconversion by using a sulfur vacancy-regulated copper-gallium-zinc-sulfide (VS-CGZS) catalyst. VS-CGZS enhances the thermal effect of light and lowers the energy barrier for acetyl group (*CH3CO) desorption from CDA. VS reduces the adsorption energy of *CH3CO on VS-CGZS and facilitated :CH2 formation. Consumption of photogenerated holes via *CH3CO desorption and VS-enhanced carrier separation synergistically elevate the photogenerated electrons concentration for :CH2 coupling, thereby selectively triggering and boosting C2H4 yield. Therefore, we achieve a record-breaking 14.43 mmol·gcat–1 C2H4 for CDA photoconversion within 4 h, over 6 times exceeding previous reports on photoconverting plastic into C2H4. This work establishes a strategy for efficient ethylene production from photoconversion of cellulose diacetate and carves out a paradigm in solar-driven plastic valorization.
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May 2026
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I10-Beamline for Advanced Dichroism - scattering
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Duncan
Miertschin
,
Alessandro R.
Mazza
,
Balaram
Regmi
,
Sundar
Kunwar
,
Poshan
Kandel
,
Ryan
Mueller
,
Clayton
Hearn
,
Peter
Bencok
,
David A.
Jack
,
Thomas
Prokscha
,
Andreas
Suter
,
Zaher
Salman
,
Alan
Farhan
,
Thomas Zac
Ward
Diamond Proposal Number(s):
[38952]
Open Access
Abstract: Chemical disorder in compositionally complex perovskite oxides generates a broad distribution of exchange pathways and spin states, but the microscopic origin and spatial homogeneity of the resulting magnetic phases remain debated. Here, we tune the Mn fraction (x = 0.2–0.6) in epitaxial La(Cr, Mn, Fe, Co, Ni)O3 thin films and resolve the coupled evolution of valence, spin state, and magnetism using element-specific x-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD). Mn enrichment drives an internal redistribution of charge, in which Mn evolves toward a Mn3+-rich mixed valence, while Co converts from predominantly Co3+ to high-spin Co2+. This valence/spin-state coupling amplifies the Mn- and Co-derived ferromagnetic response by nearly an order of magnitude while increasing the magnetic onset temperature to at least 250 K, whereas Fe and Cr remain essentially trivalent with weak dichroism. Depth-resolved low-energy muon spin spectroscopy (LE-μSR) shows magnetic homogeneity through the film thickness, with a secondary relaxation maximum near 25 K indicating a low-temperature dynamical crossover consistent with frustrated magnetism in a strongly disordered spin lattice.
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May 2026
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