B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Diamond Proposal Number(s):
[34919, 37955]
Open Access
Abstract: A combination of experimental methods and computational techniques have been used to investigate the composition of the zinc ferrite (ZnFe2O4) (1 1 1) single crystal surface under different preparation methods. Surface-sensitive XPS and NEXAFS measurements show that upon annealing in ultra-high vacuum (UHV), Zn depletion occurs, leading to the formation of an iron-rich (1 1 1) surface, whereas annealing in the presence of O2 gas maintains a more bulk-like ZnFe2O4 surface composition. Analysis of the Fe 2p photoemission (XPS) and Fe L edge X-ray absorption signals shows a clear difference in iron oxidation state and distribution between the two different preparation conditions. After annealing in UHV, a mixed Fe2+/Fe3+ oxidation state and a cation distribution like that of a magnetite (Fe3O4) structure is observed, whereas after annealing in oxygen gas only Fe3+, mostly in octahedral coordination, is observed, as expected for a ZnFe2O4 structure. Temperature-dependent XPS confirms significant Zn depletion in the near-surface region above 500 °C under UHV, with almost no Zn remaining at 600 °C; under an O2 atmosphere no zinc depletion is observed up to 600 °C. A theoretical model based on DFT simulations illustrates how reduction from ZnFe2O4 to Fe3O4 with formation of O2 and Zn gas is thermodynamically feasible under UHV conditions, whereas the same reaction is not favourable at higher oxygen partial pressures. Our findings demonstrate the strong impact that UHV treatment has on zinc ferrite surfaces, and cautions that UHV environments, routinely employed for surface analysis, can themselves induce substantial modifications to the surface, thereby complicating the interpretation of measurements in the context of catalytically relevant conditions.
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Dec 2025
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
E01-JEM ARM 200CF
I20-Scanning-X-ray spectroscopy (XAS/XES)
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Lu
Chen
,
Xuze
Guan
,
Zhangyi
Yao
,
Shusaku
Hayama
,
Matthijs A.
Van Spronsen
,
Burcu
Karagoz
,
Georg
Held
,
David G.
Hopkinson
,
Christopher S.
Allen
,
June
Callison
,
Paul J.
Dyson
,
Feng Ryan
Wang
Diamond Proposal Number(s):
[30576, 31867, 32996]
Open Access
Abstract: Tuning the electronic properties of nanocatalysts via doping with monodispersed hetero-metal atoms is an effective method used to enhance catalytic properties. Doping CuO nanoparticles with monodispersed Co atoms using different reductants affords catalysts (CoBCu/Al2O3 and CoHCu/Al2O3) with strikingly different electronic structures. Compared to CoHCu/Al2O3, the CuO nanoparticles in CoBCu/Al2O3 have longer and weaker Cu-O bonds, with a lower 1s → 4pz antibonding transition and higher 4p → 1s bonding transition (as demonstrated from HERFD-XANES and valence-to-core X-ray emission spectroscopy). The weaker Cu-O bonds in CoBCu/Al2O3 lead to superior redox activity of the CuO nanoparticles, evidenced from operando XAFS and in-situ near ambient pressure-near edge X-ray absorption fine structures studies. Such superior redox properties of CuO in CoBCu/Al2O3 result in a much reduced activation energy of CoBCu/Al2O3 compared to CoHCu/Al2O3 (40.0 vs. 63.5 kJ/mol), thus leading to an enhancement in catalytic performance in the selective catalytic oxidation of NH3 to N2.
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Oct 2025
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
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Diamond Proposal Number(s):
[33415, 34976]
Open Access
Abstract: Electro-oxidation is one of the most promising and eco-friendly technologies for water decontamination. However, its industrial application is still limited by the high cost, poor faradaic efficiency, low durability, and potential toxicity of common high-power oxidation anodes. These challenges have been addressed by developing a novel composite comprising a mixed metal oxide (NiMnO3) and reduced graphene oxide (rGO). The NiMnO3–rGO anode allowed the fast and complete removal of phenol. Among different highly porous substrates, graphite felt (GF) led to the highest energy efficiency, since the GF/NiMnO3–rGO anode yielded 100% phenol removal within only 30 min at a current density as low as 10 mA cm−2, which was accompanied by 85% COD removal at 120 min. This anode demonstrated excellent stability, maintaining 100% phenol removal efficiency across five consecutive cycles while also showing low energy consumption (60–65 Wh (kg COD)−1). Operando X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) analysis provided mechanistic insights. It is demonstrated that rGO shifts the ˙OH production pathway towards the lattice oxygen mechanism (LOM), in contrast to the adsorbate evolution mechanism (AEM) observed for NiMnO3 alone. This mechanistic shift supports the enhanced stability and sustained electrocatalytic activity, contributing to the high performance of the GF/NiMnO3–rGO composite anode in the context of a more sustainable technology for treating organic contaminants.
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Oct 2025
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
Optics
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Wai Jue
Tan
,
Arindam
Majhi
,
Wadwan
Singhapong
,
Andrew C.
Walters
,
Matthijs A.
Van Spronsen
,
Georg
Held
,
Burcu
Karagoz
,
David C.
Grinter
,
Pilar
Ferrer
,
Guru
Venkat
,
Qiushi
Huang
,
Zhe
Zhang
,
Zhanshan
Wang
,
Patrick Yuheng
Wang
,
Andrey
Sokolov
,
Hongchang
Wang
,
Kawal
Sawhney
Open Access
Abstract: X-ray Photoelectron Spectroscopy (XPS) is a powerful tool for probing the chemical and electronic states of materials with elemental specificity and surface sensitivity. However, its application in the tender X-ray range (1–5 keV) for synchrotron radiation has remained limited due to the limited choice of optics capable of maintaining high reflectivity and efficiency in this energy window. To address this, multilayer (ML) grating structures have become increasingly popular, offering significantly higher efficiency than SL coatings in the tender X-ray region. This paper presents the development of ML laminar gratings optimised for enhancing efficiency in the tender X-ray range, and capable of retaining performance under intense X-ray exposure in the oxygen partial pressure of 10 mbar. The ML coating quality was verified through X-ray reflectivity (XRR), XPS and near-edge X-ray absorption fine structures (NEXAFS) measurements, while the performance of the grating was validated through beamline flux transmission and XPS measurements. The MLLG demonstrated 22 higher intensity in flux and XPS, significantly improving the signal-to-noise ratio. Most importantly, the MLLGs outperformed traditional designs by offering improved spectral resolution while maintaining measurement capability at varying values without compromising the intensity. Furthermore, we demonstrated that the incorporation of nitrogen during deposition further enhances flux transmission.
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Oct 2025
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Gisella
Di Mari
,
Giacometta
Mineo
,
Henry
Hoddinott
,
Vincenzina
Strano
,
Claudio
Lentini Campallegio
,
Bernat
Mundet
,
Sara
Martì Sanchez
,
Giorgia
Franzò
,
Jordi
Arbiol
,
Bernd
Von Issendorff
,
Georg
Held
,
Richard
Palmer
,
Elena
Bruno
,
Salvo
Mirabella
,
Maria Chiara
Spadaro
Open Access
Abstract: Hybrid nanostructures combining semiconductor materials and noble metal clusters of atoms (nanoparticles) are of high interest in the energy sector and catalysis, with the idea of tuning the physicochemical properties of the system toward the desired performance. The design of this type of complex system requires the appropriate selection of the material combination to optimize the desired properties. However, less attention has been devoted to the effect of cluster size. In this work, we investigate the size and density effects for mass-selected monometallic Au clusters decorating ZnO-based nanostars. The Au clusters were prepared with narrow control of their size, in terms of atoms per cluster, via cluster deposition in a vacuum and mass selection with a cluster beam source. We study the coupling of ZnO nanostars with deposited AuN (N = 55, 147, and 309) clusters. We exploit transmission electron microscopy and Rutherford backscattering spectrometry for the structural characterization and for the determination of Au cluster density, obtaining 3.43 × 1012, 4.55 × 1011, and 7.98 × 1010 clusters/cm2 for samples decorated with Au clusters containing 55, 147, and 309 atoms, respectively. Moreover, we highlight the formation of a Schottky junction by performing photoluminescence investigations. We find distinctive changes in the behavior of the visible and UV emission as a function of the cluster size and density on the ZnO-based nanostars, identifying an increase of the photoluminescence efficiency with the decrease of the cluster dimension. Our findings indicate the enormous potential that a proper selection of cluster size offers in the fabrication of nanocomposite materials with precise electronic properties.
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Sep 2025
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Optics
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Open Access
Abstract: The plane grating monochromator (PGM) is an optical instrument used in the majority of soft X-ray beamlines. Despite its ubiquity, the PGM efficiency can easily be overestimated, because the geometry of many modern PGMs can lead to unexpected blocking of the beam. We have developed a new workflow in Python for simulating PGMs, thus extending the capabilities of SHADOW3, a well established ray tracing software tool. We have used our method to simulate the flux on branch C of the Versatile Soft X-ray (VerSoX) beamline B07 at Diamond Light Source. The simulation results demonstrate qualitative agreement with the experimental measurements, confirming the robustness of the proposed methodology.
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Jul 2025
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B18-Core EXAFS
I14-Hard X-ray Nanoprobe
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Lotfi
Boudjema
,
Anil Kumar
Dahiya
,
Ivan
Da Silva
,
Diego
Gianolio
,
Izuchika
Nduka
,
Manfred Erwin
Schuster
,
Gea T.
Van De Kerkhof
,
Paulina
Kalinowska
,
Emilio
Borrego-Marin
,
Jorge A. R.
Navarro
,
Valentina
Colombo
,
June
Mccorquodale
,
David C.
Grinter
,
Pilar
Ferrer
,
Georg
Held
,
C. Richard A.
Catlow
,
Rosa
Arrigo
Diamond Proposal Number(s):
[28630]
Open Access
Abstract: We investigate the rapid microwave-assisted solvothermal synthesis of a Cu-MOF (Metal-Organic Framework) with open metal sites, with a focus on understanding its CO2 capture properties in relation to phase purity and stability. A combined experimental and theoretical approach is used to identify the MOF structural features involved in the adsorption process. Specifically, Cu(I) defects are found playing an important role in the CO2 adsorption process, with the Cu-1 sample, synthesized using an optimized ligand/Cu precursor ratio for highest phase purity, exhibiting more abundant Cu(I) defects as well as highest adsorption capacity. Grand Canonical Monte Carlo simulations show that the Cu(I) sites exhibit a greater affinity for CO2 adsorption compared to the Cu(II) sites. In situ spectroscopic soft and hard X-ray absorption fine structure spectroscopy confirm the conversion of Cu(I) to Cu(II) upon CO2 chemisorption, with this conversion being more pronounced in the core of the particles. The simulations are used to estimate the fraction of Cu(I) defects and Cu(II) sites present within the Cu-1 MOF and to validate the experimental isotherm. Overall, this study provides insights into the CO2 capture properties of GIF-KUC Cu-MOFs and highlights the importance of phase purity for achieving high adsorption performance.
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Jun 2025
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E02-JEM ARM 300CF
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Emanuele
Telari
,
Antonio
Tinti
,
Manoj
Settem
,
Carlo
Guardiani
,
Lakshmi Kumar
Kunche
,
Morgan
Rees
,
Henry
Hoddinott
,
Malcolm
Dearg
,
Bernd
Von Issendorff
,
Georg
Held
,
Thomas
Slater
,
Richard E.
Palmer
,
Luca
Maragliano
,
Riccardo
Ferrando
,
Alberto
Giacomello
Diamond Proposal Number(s):
[28449]
Open Access
Abstract: Finding proper collective variables for complex systems and processes is one of the most challenging tasks in simulations, which limits the interpretation of experimental and sim- ulated data and the application of enhanced sampling techniques. Here, we propose a machine learning approach able to distill few, physically relevant variables by associating instantaneous configurations of the system to their corresponding inherent structures as defined in liquids theory. We apply this approach to the challenging case of structural tran- sitions in nanoclusters, managing to characterize and explore the structural complexity of
an experimentally relevant system constituted by 147 gold atoms. Our inherent-structure variables are shown to be e!ective at computing complex free-energy landscapes, transi-
tion rates, and at describing non-equilibrium melting and freezing processes. In addition,
we illustrate the generality of this machine learning strategy by deploying it to understand conformational rearrangements of the bradykinin peptide, indicating its applicability to a vast range of systems, including liquids, glasses, and proteins.
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May 2025
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Abstract: Of all experimental Surface Science techniques, LEED-IV surface crystallography delivers the most complete set of crystallographic data for the near-surface regions (down to
Å below the surface) of ordered single crystal surfaces. In the last five decades a large number of surface structures have been determined but theoretical and experimental procedures need to be adopted to meet the requirements of new directions in Surface Science. In this perspective article approaches will be discussed for extracting structural information from disordered and rough surfaces, increasing the experimental data set for large unit cells with complex unit cells, improving the scattering potentials used to calculate LEED-IV curves, and expanding the pressure range of the technique.
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Jan 2025
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
E01-JEM ARM 200CF
E02-JEM ARM 300CF
I20-EDE-Energy Dispersive EXAFS (EDE)
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Lu
Chen
,
Xuze
Guan
,
Zhaofu
Fei
,
Hiroyuki
Asakura
,
Lun
Zhang
,
Zhipeng
Wang
,
Xinlian
Su
,
Zhangyi
Yao
,
Luke L.
Keenan
,
Shusaku
Hayama
,
Matthijs A.
Van Spronsen
,
Burcu
Karagoz
,
Georg
Held
,
Christopher S.
Allen
,
David G.
Hopkinson
,
Donato
Decarolis
,
June
Callison
,
Paul J.
Dyson
,
Feng Ryan
Wang
Diamond Proposal Number(s):
[30622, 33257, 31922]
Open Access
Abstract: Selective catalytic oxidation (SCO) of NH3 to N2 is one of the most effective methods used to eliminate NH3 emissions. However, achieving high conversion over a wide operating temperature range while avoiding over-oxidation to NOx remains a significant challenge. Here, we report a bi-metallic surficial catalyst (PtSCuO/Al2O3) with improved Pt atom efficiency that overcomes the limitations of current catalysts. It achieves full NH3 conversion at 250 °C with a weight hourly space velocity of 600 ml NH3·h−1·g−1, which is 50 °C lower than commercial Pt/Al2O3, and maintains high N2 selectivity through a wide temperature window. Operando XAFS studies reveal that the surface Pt atoms in PtSCuO/Al2O3 enhance the redox properties of the Cu species, thus accelerating the Cu2+ reduction rate and improving the rate of the NH3-SCO reaction. Moreover, a synergistic effect between Pt and Cu sites in PtSCuO/Al2O3 contributes to the high selectivity by facilitating internal selective catalytic reduction.
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Jan 2025
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