B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Diamond Proposal Number(s):
[33956]
Abstract: Multiwavelength light emission was observed in undoped tin oxide thin films deposited by metal-organic chemical vapor deposition at temperatures ranging from 700°C to 800°C. This work presents the relationship between the presence and nature of defects in undoped SnO2 thin films and their emission properties. Blue and orange emissions were observed on SnO2 thin films using a He-Cd laser and an Xe lamp at an excitation wavelength of 325 nm. Systematic characterization and analysis techniques, including low-temperature photoluminescence at temperatures ranging from 77K to 298K and surface-sensitive techniques using brilliant synchrotron radiation facilities, were applied to elucidate the features and origin of emission in undoped SnO2 layers. Based on our results, surface and bulk oxygen and interstitial tin defects play an important role in multi-wavelength emission processes and can be separately activated by controlling the applied light source.
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Dec 2025
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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-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Diamond Proposal Number(s):
[40403]
Open Access
Abstract: Metal−organic gels (MOGs) and their derived aerogels (MOAs) offer an alternative to crystalline MOFs, combining the coordination-driven tunability with the flexibility, hierarchical porosity, and easy processability of sol–gel polymers. Their noncrystalline nature enables the integration of functional units without crystallization constraints, facilitating diverse uses, and drawing recent attention for photocatalytic applications. Herein we report the design of a new approach to prepare a titanium-based MOA synthesized via a two-step strategy involving a preformed titanium oxo-cluster ([Ti8O8(benzoato)16]), and a subsequent ligand exchange with benzene-1,3,5-tricarboxylato ligands. A combined chemical, microstructural, and NEXAFS analysis confirms the retention of Ti8 cluster and the presence of uncoordinated −COOH groups after meso-macroporous gel formation. Those enabled a subsequent homogeneous incorporation of single-atom site co-catalysts via coordination with Ru, Co, Ni, and Cu complexes bearing terpyridine, bipyridine, and phenanthroline N-ligands. Photocatalytic hydrogen evolution under 365 nm LED irradiation exhibited significant activity (110 μmol·g–1·h–1), which further increased upon functionalization. The MOAs functionalized with Ru- and Cu-terpyridine complexes showed the highest performance (167 and 164 μmol·g–1·h–1, respectively), surpassing even Pt-loaded analogues and highlighting the role of terpyridine in facilitating multielectron storage. The system also showed stable long-term performance up to 24 h.
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Dec 2025
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Burcu
Karagoz
,
Tianhao
Hu
,
Joakim
Halldin Stenlid
,
Xiaoming
Hu
,
Markus
Soldemo
,
Frank
Abild-Pedersen
,
Kess
Marks
,
Henrik
Öström
,
Dario
Stacchiola
,
Jonas
Weissenrieder
,
Ashley R.
Head
Diamond Proposal Number(s):
[34882]
Open Access
Abstract: Performing oxidation reactions at low temperatures using earth-abundant materials is crucial for advancing solutions for sustainable chemistry. CO oxidation serves as a benchmark reaction to characterize oxidation and to advance fundamental concepts in surface chemistry. While there are several examples of CO oxidation occurring on metal oxides at low temperatures, from 300 K to ∼200 K, reactivity in the cryogenic temperature regime typically requires a metal nanoparticle on a metal oxide. Here, we show oxygen atoms on the (111) facet of Cu2O react with CO to form CO2 at temperatures below 100 K. Combining spectroscopic experimental evidence with calculations, we propose a low barrier path for CO oxidation at reconstructed surface sites on Cu2O(111). This finding is a rare example of an earth-abundant metal oxide, in this case copper, that can provide highly reactive multifunctional sites, enabling both adsorption and reaction fundamental steps toward the efficient heterogeneous oxidation of chemicals.
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Nov 2025
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Jonathan R.
Thurston
,
Shuya
Li
,
Qi
Sun
,
Dennis
Nordlund
,
Luis
Kitsu Iglesias
,
Collin
Sindt
,
Santosh
Kumar
,
David C.
Grinter
,
Hong
Li
,
Ann L.
Greenaway
,
Elisa M.
Miller
,
Michael F.
Toney
Diamond Proposal Number(s):
[35956]
Abstract: P(NDI2OD-T2), commonly referred to as N2200, stands out as a promising electron-transporting (n-type) polymer for low-cost, flexible (photo)electrochemical applications due to its reversible two-electron reduction and high electron mobility. UV–vis spectroelectrochemistry in the tetrabutyl ammonium hexafluorophosphate/acetonitrile electrolyte shows two sets of chemically reversible redox signals in the cyclic voltammetry corresponding to the reduction of the neutral polymer film to polaronic and bipolaronic species. These electrochemical signatures suggest a distinct electronic reorganization upon reduction (polaron/bipolaron formation), highlighting the need for molecular-level insights into how charges are accommodated within the polymer backbone. While it has been previously hypothesized that charge predominantly localizes on the naphthalene diimide (NDI) unit during reductive charging, specific changes in atomic environments that confirm this localization have not been characterized in n-type polymers. Herein, we use near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to probe electronic transitions in an electrochemically charged polymer to deduce charge localization. The O K-edge (1s) spectra exhibit two distinct π* peaks; the intensity of the lower-energy π*a peak that corresponds to an excitation to a largely localized carbonyl state decreases with reductive potentials relative to the higher-energy π*b peak. We corroborate this with Raman spectroscopy at different potentials, which shows a decrease in intensity on the C–C/C═C and C═O stretching bands of NDI as well as a red shift of the carbonyl band due to the formation of a polaron on the NDI. Additionally, new Raman active NDI signals associated with elongated C═O and C═C bonds are observed at lower energy during the formation of charged states. Together with theoretical calculations, these findings show that the injected charge spatially localizes on the NDI units and is dominantly distributed on the carbonyl groups. The combination of NEXAFS, optical and vibrational spectroscopies, and theoretical calculations is generalizable to other pi-conjugated polymers and can identify charge localization for the further development of organic semiconductors.
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Oct 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-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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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Diamond Proposal Number(s):
[33408]
Open Access
Abstract: In pursuing environmentally friendly lubrication solutions, it is advantageous to employ organic additives that are free from heavy metals and have low or zero levels of phosphorus and sulfur functionalities. Organic friction modifiers strongly reduce friction and wear when added to engine oils through the formation of an adsorbed boundary film on the contacting surfaces. The mechanism of tribofilm formation and its chemical effects on friction reduction are not entirely understood. In this study, the lubrication mechanism of OFM was investigated with a new approach combining three different acylglycerols with varying ratios. The lubricating performance of mixtures of glycerol monooleate (GMO), glycerol trioleate (triolein), and glycerol dioleate (GDO), as well as individual GMO and triolein in PAO4, was evaluated under the boundary lubrication regime at two temperatures, 60 °C and 100 °C. A synergetic effect on tribological performance has been observed for the mixture formulation. This resulted in lower friction and wear than the single additive in the base oil at both temperatures. The HRTEM analysis indicated that the combination of different acylglycerols provides a thicker tribofilm compared to the single additive. The ToF-SIMS and NEXAFS analyses of the resulting tribofilms showed that at a temperature of 60 °C, the main components of the tribofilm were compounds formed by GMO decomposition and oleate ions, indicating that chemisorption plays a significant role in reducing friction at lower temperatures for the tested OFM additives.
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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
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Mark A.
Isaacs
,
Charalampos
Drivas
,
Arthur
Graf
,
Sasha
Kroon
,
Santosh
Kumar
,
Junxi
Liu
,
Antonio
Torres‐lopez
,
Cameron
Price
,
Edward
Garland
,
Ines
Lezcano-Gonzalez
,
Christopher M. A.
Parlett
,
Vannia C.
Dos Santos-Durndell
,
Lee J.
Durndell
Diamond Proposal Number(s):
[40403]
Open Access
Abstract: 2.5% of global carbon emissions result from air travel, underscoring the need for sustainable aviation fuels (SAF) derived from second-generation lignocellulosic biomass to enhance the green credentials of the aviation sector. This study demonstrates the first solvent-free photocatalytic conversion of furfural (FAL) and cyclopentanone (CPO) to produce 2,5-bis(2-furylmethylidene)cyclopentanone (F2Cp), a jet fuel precursor, using Ti-SBA-15 catalysts, synthesized via alkoxide grafting and controlled titanium surface coverage. Sub-monolayer titania films on SBA-15 supports are achieved with tuneable Ti content, confirmed by XPS (X-ray photoelectron spectroscopy), UPS (ultraviolet photoelectron spectroscopy), REELS (reflectance electron energy loss spectroscopy), ISS (ion scattering spectroscopy), and Raman analysis. XPS analyses reveal coverage-dependent Ti speciation, transitioning from isolated Ti atoms to interconnected Ti-O-Ti networks, with corresponding shifts in Auger parameters, indicating increased surface polarizability and Lewis acidity. Optimized Ti-SBA-15 catalysts exhibit a fourfold activity enhancement in photocatalytic activity over bulk TiO₂, attributed to improved mass transport, active site accessibility, and surface stability. This work highlights the potential of rationally designed hierarchical catalysts for scalable, energy-efficient biomass valorization into SAF precursors, offering a scalable, energy-efficient pathway for sustainable jet fuel production. By elucidating the structure-function relationships in sub-monolayer Ti-SBA-15 materials, this study provides critical insights for advancing photocatalytic technologies in renewable energy applications.
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Jul 2025
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