B18-Core EXAFS
I18-Microfocus Spectroscopy
I20-EDE-Energy Dispersive EXAFS (EDE)
I20-Scanning-X-ray spectroscopy (XAS/XES)
Controls
Detectors
Optics
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Sofia
Diaz-moreno
,
Monica
Amboage
,
Mark
Basham
,
Roberto
Boada
,
Nicholas E.
Bricknell
,
Giannantonio
Cibin
,
Thomas
Cobb
,
Jacob
Filik
,
Adam
Freeman
,
Kalotina
Geraki
,
Diego
Gianolio
,
Shusaku
Hayama
,
Konstantin
Ignatyev
,
Luke
Keenan
,
Iuliia
Mikulska
,
J. Frederick W.
Mosselmans
,
James J.
Mudd
,
Stephen A.
Parry
Open Access
Abstract: This manuscript presents the current status and technical details of the Spectroscopy Village at Diamond Light Source. The Village is formed of four beamlines: I18, B18, I20-Scanning and I20-EDE. The village provides the UK community with local access to a hard X-ray microprobe, a quick-scanning multi-purpose XAS beamline, a high-intensity beamline for X-ray absorption spectroscopy of dilute samples and X-ray emission spectroscopy, and an energy-dispersive extended X-ray absorption fine-structure beamline. The optics of B18, I20-scanning and I20-EDE are detailed; moreover, recent developments on the four beamlines, including new detector hardware and changes in acquisition software, are described.
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Jul 2018
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B18-Core EXAFS
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Diamond Proposal Number(s):
[10411]
Abstract: We report on results of a comprehensive investigation on reaction mechanisms occurring during Li uptake and release of the composite NiFe2O4/CNT. Operando X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) data collected simultaneously using one in situ cell allowed thorough elucidation of structural and electronic alterations happening during Li uptake. From the beginning of Li uptake, the Bragg intensity of the spinel reflections decreases which can be explained by reduction of Fe3+ ions and simultaneous movement of the Fe2+ cations from tetrahedral 8a to empty octahedral 16c sites. The reduction of Fe3+ is clearly evidenced by XAS. The occupation of tetrahedral sites by Li+ can be excluded based on results of density functional theory calculations. Increasing the Li content leads to formation of a new crystalline phase resembling a monoxide with a NaCl-like structure. The appearance of the new phase is accompanied by a steady decrease of the sizes of coherently scattering domains of the spinel and a growth of the domains of the monoxide phase. After uptake of about 2.5 Li per NiFe2O4, all Fe3+ cations are reduced to Fe2+ and the tetrahedral 8a sites are empty (XAS spectra). Careful Rietveld refinements of X-ray powder patterns demonstrate that the tetrahedral 8a site is successively depleted with increasing Li content. Interestingly, the occupancy of the octahedral 16d site is also slightly reduced. Increasing the Li content beyond 2.5 Li/NiFe2O4 leads to successive reduction of the cations to very small metal particles embedded in a Li2O matrix (as evidenced by 7Li MAS NMR investigations). During Li release metallic Ni and Fe are reoxidized to Ni2+ resp. Fe3+. The cycling stability of NiFe2O4/CNT is significantly improved compared to pure NiFe2O4 or a mechanical mixture of NiFe2O4 and CNTs.
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Jun 2018
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B18-Core EXAFS
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Diamond Proposal Number(s):
[10306]
Abstract: The use of sol-immobilisation to prepare supported metal nanoparticles is an area of growing importance in heterogeneous catalysis; it affords greater control of nanoparticle properties compared to conventional catalytic routes e.g. impregnation. This work, and other recent studies, demonstrate how the properties of the resultant supported metal nanoparticles can be tailored by adjusting the conditions of colloidal synthesis i.e. temperature and solvent. We further demonstrate the applicability of these methods to the hydrogenation of nitrophenols using a series of tailored Pd/TiO2 catalysts, with low Pd loading 0.2 wt. %. Here, the temperature of colloidal synthesis is directly related to the mean particle diameter and the catalytic activity. Smaller Pd particles (2.2 nm, k = 0.632 min-1, TOF = 560 h-1) perform better than their larger counterparts (2.6 nm, k = 0.350 min-1, TOF = 370 h-1) for the hydrogenation of p-nitrophenol, with the catalyst containing smaller NPs found to have increased stability during recyclability studies, with high activity (> 90% conversion after 5 minutes) maintained across 5 catalytic cycles.
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Mar 2018
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B18-Core EXAFS
E01-JEM ARM 200CF
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Chiara
Genovese
,
Manfred E.
Schuster
,
Emma K.
Gibson
,
Diego
Gianolio
,
Victor
Posligua
,
Ricardo
Grau-crespo
,
Giannantonio
Cibin
,
Peter
Wells
,
Debi
Garai
,
Vladyslav
Solokha
,
Sandra
Krick Calderon
,
Juan J.
Velasco-velez
,
Claudio
Ampelli
,
Siglinda
Perathoner
,
Georg
Held
,
Gabriele
Centi
,
Rosa
Arrigo
Diamond Proposal Number(s):
[17031, 10306]
Open Access
Abstract: The carbon–carbon coupling via electrochemical reduction of carbon dioxide represents the biggest challenge for using this route as platform for chemicals synthesis. Here we show that nanostructured iron (III) oxyhydroxide on nitrogen-doped carbon enables high Faraday efficiency (97.4%) and selectivity to acetic acid (61%) at very-low potential (−0.5 V vs silver/silver chloride). Using a combination of electron microscopy, operando X-ray spectroscopy techniques and density functional theory simulations, we correlate the activity to acetic acid at this potential to the formation of nitrogen-coordinated iron (II) sites as single atoms or polyatomic species at the interface between iron oxyhydroxide and the nitrogen-doped carbon. The evolution of hydrogen is correlated to the formation of metallic iron and observed as dominant reaction path over iron oxyhydroxide on oxygen-doped carbon in the overall range of negative potential investigated, whereas over iron oxyhydroxide on nitrogen-doped carbon it becomes important only at more negative potentials.
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Mar 2018
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B18-Core EXAFS
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Diamond Proposal Number(s):
[12775]
Open Access
Abstract: Pd nanoparticles supported on SiO2, Si3N4 and Al2O3 were studied to examine the effect of particle size and support type on the hydrogenation of 1,3-butadiene. Pd nanoparticles were produced using a reverse micelle method resulting in particles with a remarkably small particle size distribution (σ < < 1 nm). The support type and particle size were observed to affect both catalytic activity and product selectivity. All catalysts showed a decrease of their activity with time on stream, paired with an increase in selectivity to butenes (1-butene and cis/trans-2-butene) from a product stream initially dominated by n-butane. In situ XAFS demonstrated a correlation between the formation of palladium hydride and n-butane production in the early stages (~ 1 h) of reaction. The extent of palladium hydride formation, as well as its depletion with time on stream, was dependent on both particle size and support type. Metallic Pd was identified as the species selective towards the production of butenes.
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Jan 2018
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B18-Core EXAFS
I10-Beamline for Advanced Dichroism
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Richard
Kimber
,
Edward A.
Lewis
,
Fabio
Parmeggiani
,
Kurt
Smith
,
Heath
Bagshaw
,
Toby
Starborg
,
Nimisha
Joshi
,
Adriana
Figueroa
,
Gerrit
Van Der Laan
,
Giannantonio
Cibin
,
Diego
Gianolio
,
Sarah J.
Haigh
,
Richard A. D.
Pattrick
,
Nicholas J.
Turner
,
Jonathan R.
Lloyd
Diamond Proposal Number(s):
[15476, 16136]
Open Access
Abstract: Copper nanoparticles (Cu-NPs) have a wide range of applications as heterogeneous catalysts. In this study, a novel green biosynthesis route for producing Cu-NPs using the metal-reducing bacterium, Shewanella oneidensis is demonstrated. Thin section transmission electron microscopy shows that the Cu-NPs are predominantly intracellular and present in a typical size range of 20–40 nm. Serial block-face scanning electron microscopy demonstrates the Cu-NPs are well-dispersed across the 3D structure of the cells. X-ray absorption near-edge
spectroscopy and extended X-ray absorption fine-structure spectroscopy analysis show the nanoparticles are Cu(0), however, atomic resolution images and electron energy loss spectroscopy suggest partial oxidation of the surface layer to Cu2O upon exposure to air. The catalytic activity of the Cu-NPs is demonstrated in an archetypal “click chemistry” reaction, generating good yields during azide-alkyne cycloadditions, most likely catalyzed by the Cu(I) surface layer of the nanoparticles. Furthermore, cytochrome deletion mutants suggest a novel metal reduction system is involved in enzymatic Cu(II) reduction and Cu-NP synthesis, which is not dependent on the Mtr pathway commonly used to reduce other high oxidation state metals in this bacterium. This work demonstrates a novel, simple, green biosynthesis method for producing efficient copper nanoparticle catalysts.
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Jan 2018
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B18-Core EXAFS
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Diamond Proposal Number(s):
[15151]
Open Access
Abstract: Efficient oxidation catalysts are important in many current industrial processes, including the selective oxidation of methanol to formaldehyde. Vanadium-containing catalysts have been shown to be effective selective oxidation catalysts for certain reactions, and research continues to examine their applicability to other reactions of interest. Several VOx/Fe2O3 shell–core catalysts with varying VOx coverage have been produced to investigate the stability of VOx monolayers and their selectivity for methanol oxidation. Catalyst formation proceeds via a clear progression of distinct surface species produced during catalyst calcination. At 300 °C the selective VOx overlayer has formed; by 500 °C a sandwich layer of FeVO4 arises between the VOx shell and the Fe2O3 core, inhibiting iron cation participation in the catalysis and enhancing catalyst selectivity. The resulting catalysts, comprising a shell–subshell–core system of VOx/FeVO4/Fe2O3, possess good catalytic activity and selectivity to formaldehyde.
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Nov 2017
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Abstract: We used Ni K-edge resonant-valence-to-core X-ray emission spectroscopy (RVtC-XES, also referred to as direct RIXS), an element-selective bulk-sensitive synchrotron-based technique, to investigate the electronic structure of the CPO-27-Ni metal–organic framework (MOF) upon molecular adsorption of significant molecular probes: H2O, CO, H2S, and NO. We compare RVtC-XES with UV–vis spectroscopy, and we show that the element selectivity of RVtC-XES is of strategic significance to observe the full set of d–d excitations in Ni2+, which are partially overshadowed by the low-energy π–π* transitions of the Ni ligands in standard diffuse-reflectance UV–vis experiments. Our combined RVtC-XES/UV–vis approach provides access to the whole set of d–d excitations, allowing us a complete discussion of the changes undergone by the electronic configuration of the Ni2+ sites hosted within the MOF upon molecular adsorption. The experimental data have been interpreted by multiplet ligand-field theory calculations based on Wannier orbitals. This study represents a step further in understanding the ability of the CPO-27-Ni MOFs in molecular sorption and separation applications.
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Oct 2017
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B18-Core EXAFS
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Diamond Proposal Number(s):
[12480]
Abstract: EXAFS and XANES experiments were used to assess decavanadate interplay with actin, in both the globular and polymerized forms, under different conditions of pH, temperature, ionic strength, and presence of ATP. This approach allowed us to simultaneously probe, for the first time, all vanadium species present in the system. It was established that decavanadate interacts with G-actin, triggering a protein conformational reorientation that induces oxidation of the cysteine core residues and oxidovanadium (VIV) formation. The local environment of vanadium’s absorbing center in the [decavanadate–protein] adducts was determined, a V–SCys coordination having been verified experimentally. The variations induced in decavanadate’s EXAFS profile by the presence of actin were found to be almost totally reversed by the addition of ATP, which constitutes a solid proof of decavanadate interaction with the protein at its ATP binding site. Additionally, a weak decavanadate interplay with F-actin was suggested to take place, through a mechanism different from that inferred for globular actin. These findings have important consequences for the understanding, at a molecular level, of the significant biological activities of decavanadate and similar polyoxometalates, aiming at potential pharmacological applications.
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Aug 2017
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B18-Core EXAFS
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Ellie K.
Dann
,
Emma K.
Gibson
,
Richard A.
Catlow
,
Paul
Collier
,
Tugce
Eralp Erden
,
Diego
Gianolio
,
Christopher
Hardacre
,
Anna
Kroner
,
Agnes
Raj
,
Alexandre
Goguet
,
Peter
Wells
Diamond Proposal Number(s):
[10306]
Abstract: The rational design of catalysts is of great industrial significance, yet there is a fundamental lack of knowledge in some of the most well-established processes e.g. formation of supported nanoparticle structures through impregnation. Here, the choice of precursor has a significant influence on the resulting catalytic properties of the end material, yet the chemistry that governs the transformation from defined molecular systems to dispersed nanoparticles is often over-looked. A spectroscopic method for advanced in situ characterization is employed to capture the formation of PdO nanoparticles supported on γ-Al2O3 from two alternative molecular precursors; Pd(NO3)2 and Pd(NH3)4(OH)2. Time resolved DRIFTS is able to identify the temperature assisted pathway for ligand decomposition, showing that NH3 lig-ands are oxidised to N2O and NO- species, whereas, NO3- ligands assist in joining Pd centres via bidentate bridging co-ordination. Combining with simultaneous XAFS, the resulting nucleation and growth mechanism of the precious metal oxide nanoparticles are resolved. The bridging ability of palladium nitrate aids formation and growth of larger PdO nanoparticles at lower onset temperature (<250°C). Conversely, impregnation from [Pd(NH3)4]2+ results in well isolated Pd centres, anchored to the support, which require higher temperature (>360°C) for migration to form observ-able Pd-Pd distances of PdO nanoparticles. These smaller nanoparticles have improved dispersion and an increased number of step and edge sites compared to those formed from the conventional Pd(NO3)2 salt, favouring a lower light off temperature for complete methane oxidation.
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Jul 2017
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