I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[21871]
Open Access
Abstract: β-NaYF4 nanocrystals are a popular class of optical materials. They can be doped with optically active lanthanide ions and shaped into core–multi-shell geometries with controlled dopant distributions. Here, we follow the synthesis of β-NaYF4 nanocrystals from α-NaYF4 precursor particles using in situ small-angle and wide-angle X-ray scattering and ex-situ electron microscopy. We observe an evolution from a monomodal particle size distribution to bimodal, and eventually back to monomodal. The final size distribution is narrower in absolute numbers than the initial distribution. These peculiar growth dynamics happen in large part before the α-to-β phase transformation. We propose that the splitting of the size distribution is caused by variations in the reactivity of α-NaYF4 precursor particles, potentially due to inter-particle differences in stoichiometry. Rate equation modeling confirms that a continuous distribution of reactivities can result in the observed particle growth dynamics.
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May 2023
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[30461]
Open Access
Abstract: Hydrogen-bonded organic frameworks (HOFs) with low densities and high porosities are rare and challenging to design because most molecules have a strong energetic preference for close packing. Crystal structure prediction (CSP) can rank the crystal packings available to an organic molecule based on their relative lattice energies. This has become a powerful tool for the a priori design of porous molecular crystals. Previously, we combined CSP with structure-property predictions to generate energy–structure–function (ESF) maps for a series of triptycene-based molecules with quinoxaline groups. From these ESF maps, triptycene trisquinoxalinedione (TH5) was predicted to form a previously unknown low-energy HOF (TH5-A) with a remarkably low density of 0.374 g cm-3 and three-dimensional (3-D) pores. Here, we demonstrate the reliability of those ESF maps by discovering this TH5-A polymorph experimentally. This material has a high accessible surface area of 3,284 m2 g-1, as measured by nitrogen adsorption, making it one of the most porous HOFs reported to date.
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Apr 2023
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I11-High Resolution Powder Diffraction
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Zi
Wang
,
Alena M.
Sheveleva
,
Daniel
Lee
,
Yinlin
Chen
,
Dinu
Iuga
,
W. Trent
Franks
,
Yujie
Ma
,
Jiangnan
Li
,
Lei
Li
,
Yongqiang
Cheng
,
Luke L.
Daemen
,
Sarah J.
Day
,
Anibal J.
Ramirez-Cuesta
,
Bing
Han
,
Alexander S.
Eggeman
,
Eric J. L.
Mcinnes
,
Floriana
Tuna
,
Sihai
Yang
,
Martin
Schroeder
Abstract: We report the modulation of reactivity of nitrogen dioxide (NO2) in a charged metal-organic framework (MOF) material, MFM-305-CH3 in which unbound N-centres are methylated and the cationic charge counter-balanced by Cl− ions in the pores. Uptake of NO2 into MFM-305-CH3 leads to reaction between NO2 and Cl– to give nitrosyl chloride (NOCl) and NO3− anions. A high dynamic uptake of 6.58 mmol g−1 at 298 K is observed for MFM-305-CH3 as measured using a flow of 500 ppm NO2 in He. In contrast, the analogous neutral material, MFM-305, shows a much lower uptake of 2.38 mmol g−1. The binding domains and reactivity of adsorbed NO2 molecules within MFM-305-CH3 and MFM-305 have been probed using in situ synchrotron X-ray diffraction, inelastic neutron scattering and by electron paramagnetic resonance, high-field solid-state nuclear magnetic resonance and UV-vis spectroscopies. The design of charged porous sorbents provides a new platform to control the reactivity of corrosive air pollutants.
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Apr 2023
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I24-Microfocus Macromolecular Crystallography
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Abstract: RAS proteins control various intracellular signaling networks. Mutations at specific locations were shown to stabilize their active guanosine triphosphate (GTP)-bound state, which is associated with the development of multiple cancers. An attractive approach to modulate RAS signaling is through its regulatory guanine nucleotide exchange factor (GEF) son of sevenless 1 (SOS1). With the recent discovery of Nanobody14 (Nb14), which potently enhances SOS1-catalyzed nucleotide exchange on RAS, we explored the feasibility of developing peptide mimetics by structurally mimicking the complementarity-determining region 3 (CDR3). Guided by a biochemical GEF assay and X-ray co-crystal structures, successive rounds of optimization and gradual conformational rigidification led to CDR3 mimetics showing half of the maximal activation potential of Nb14 with an EC50 value of 29 μM. Altogether, this study demonstrated that peptides able to modulate a protein-protein interaction can be obtained by structural mimicry of a Nb paratope.
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Apr 2023
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B18-Core EXAFS
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Wei
Zong
,
Haiqi
Gao
,
Yue
Ouyang
,
Kaibin
Chu
,
Hele
Guo
,
Leiqian
Zhang
,
Wei
Zhang
,
Ruwei
Chen
,
Yuhang
Dai
,
Fei
Guo
,
Jiexin
Zhu
,
Zhenfang
Zhang
,
Chumei
Ye
,
Yue-E
Miao
,
Johan
Hofkens
,
Feili
Lai
,
Tianxi
Liu
Diamond Proposal Number(s):
[31573]
Open Access
Abstract: Overwhelming competition from hydrogen/oxygen evolution reactions and low solubility of N2 in aqueous systems drain on selectivity and activity on nitrogen fixation reaction. Herein, we design an aerobic-hydrophobic Janus structure by introducing fluorinated modification on porous carbon nanofibers embedded with partially carbonized iron heterojunctions (Fe3C/Fe@PCNF-F). The simulations prove that the Janus structure can keep the internal Fe3C/Fe@PCNF-F away from water infiltration and endow a N2 molecule-concentrating effect, suppressing the competing reactions and overcoming the mass-transfer limitations to build a robust "quasi-solid-gas" state micro-domain around the catalyst surface. In this proof-of-concept system, the Fe3C/Fe@PCNF-F exhibits excellent electrocatalytic performance for nitrogen fixation (NH3 yield rate up to 29.2 μg h-1 mg-1cat. and Faraday efficiency (FE) up to 27.8% in NRR; NO3- yield rate up to 15.7 μg h-1 mg-1cat. and FE up to 3.4 % in NOR).
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Apr 2023
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E01-JEM ARM 200CF
E02-JEM ARM 300CF
I20-Scanning-X-ray spectroscopy (XAS/XES)
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Runjia
Lin
,
Liqun
Kang
,
Karolina
Lisowska
,
Weiying
He
,
Siyu
Zhao
,
Shusaku
Hayama
,
Dan
Brett
,
Graham
Hutchings
,
Furio
Corà
,
Ivan
Parkin
,
Guanjie
He
Diamond Proposal Number(s):
[29254, 29207]
Open Access
Abstract: Electrocatalytic oxygen reduction reaction (ORR) has been intensively studied for efficient and environmentally benign energy conversion processes. However, insufficient understanding of ORR 2e--pathway mechanism at the atomic level inhibits rational design of electrocatalysts with both high activity and selectivity, causing concerns including catalyst degradation due to Fenton reaction or poor efficiency of H2O2 electrosynthesis. Herein we show that the generally accepted ORR electrocatalyst design based on a Sabatier volcano plot argument optimises activity but is unable to account for the 2e--pathway selectivity; an extended “dynamic active site saturation” model that examines in addition the hydrogenation kinetics linked to the OOH* adsorption energy enables us to resolve the activity-selectivity compromise. Through electrochemical and operando spectroscopic studies on the ORR process governed by a series of Co-N x /carbon nanotube hybrids, a construction-driven approach that aims to create the maximum number of 2e- ORR sites by directing the secondary ORR electron transfer step towards the 2e- intermediate is proven to be attainable by manipulating O2 hydrogenation kinetics. Control experiments reveal the O2 hydrogenation chemistry is related to a catalyst reconstruction with lower symmetry around the Co active centre induced by the application of a cathodic potential. The optimised catalyst exhibits a ~100% H2O2 selectivity and an outstanding activity with an ORR potential of 0.82 V versus the reversible hydrogen electrode to reach the ring current density of 1 mA cm-2 by using rotating ring-disk electrode measurement, which is the best-performing 2e- ORR electrocatalyst reported to date, and approaches the thermodynamic limit.
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Mar 2023
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[21497]
Open Access
Abstract: Self-assembly of a flexible tritopic aniline and 3-substituted 2-formylpyridine subcomponents around iron(II) templates gave rise to low-spin FeII4L4 capsule, whereas a high-spin FeII3L2 sandwich species formed when a sterically hindered 6-methyl-2-formylpyridine was used. The FeII4L4 cage adopted a new structure type with S4 symmetry, having two mer-Δ and two mer-Ʌ metal vertices, as confirmed by NMR and X-ray crystallographic analysis. The flexibility of the face-capping ligand endows the resulting FeII4L4 framework with conformational plasticity, enabling it to adapt structurally from S4 to T or C3 symmetry upon guest binding. The cage also displayed negative allosteric cooperativity in simultaneously binding different guests within its cavity and at the apertures between its faces.
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Mar 2023
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B07-B-Versatile Soft X-ray beamline: High Throughput
E02-JEM ARM 300CF
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Longxiang
Liu
,
Liqun
Kang
,
Arunabhiram
Chutia
,
Jianrui
Feng
,
Martyna
Michalska
,
Pilar
Ferrer
,
David
Grinter
,
Georg
Held
,
Yeshu
Tan
,
Fangjia
Zhao
,
Fei
Guo
,
David
Hopkinson
,
Christopher
Allen
,
Yanbei
Hou
,
Junwen
Gu
,
Ioannis
Papakonstantinou
,
Paul
Shearing
,
Dan
Brett
,
Ivan P.
Parkin
,
Guanjie
He
Diamond Proposal Number(s):
[29340, 32501, 30614, 29809, 32058]
Open Access
Abstract: The electrochemical synthesis of hydrogen peroxide (H2O2) via a two-electron (2e-) oxygen reduction reaction (ORR) process provides a promising alternative to replace the energy-intensive anthraquinone process. However, the development of efficient electrocatalysts is still facing lots of challenges like insufficient understanding of active sites. Herein, we develop a facile template-protected strategy to synthesize a highly active quinone-rich porous carbon catalyst (PCC) for H2O2 electrochemical production. The optimized PCC900 exhibits unprecedented activity and selectivity, of which the onset potential reaches 0.83 V vs. reversible hydrogen electrode in 0.1 M KOH and the H2O2 selectivity is over 95 % in a wide potential range. Comprehensive synchrotron-based near-edge X-ray absorption fine structure (NEXAFS) spectroscopy combined with electrocatalytic characterizations reveals the positive correlation between quinone content and 2e- ORR performance. The effectiveness of chair-form quinone groups as the most efficient active sites is highlighted by the molecule-mimic strategy and theoretical analysis.
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Mar 2023
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[21497]
Open Access
Abstract: A double-walled tetrahedral metal-organic cage assembled in solution from silver(I), 2-formyl-1,8-naphthyridine, halide, and a threefold-symmetric triamine. The AgI4X clusters at its vertices bring together six naphthyridine-imine moieties, leading to a structure in which eight tritopic ligands bridge four clusters in an (AgI4X)4L8 arrangement. Four ligands form an inner set of tetrahedron walls that are surrounded by the outer four. The cage has significant interior volume, and was observed to bind anionic guests. The structure also possesses external binding clefts, located at the edges of the cage, which bound small aromatic guests. Halide ions bound to the silver clusters were observed to exchange in a well-defined hierarchy, allowing modulation of the cavity volume. The principles uncovered here may allow for increasingly more sophisticated cages with silver-cluster vertex architectures, with post-assembly tuning of the interior cavity volume enabling targeted binding behavior.
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Feb 2023
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I15-1-X-ray Pair Distribution Function (XPDF)
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Mohamed. A.
Ali
,
Wessel M. W.
Winters
,
Moushira A.
Mohamed
,
Dezhi
Tan
,
Guojun
Zheng
,
Rasmus S. K.
Madsen
,
Oxana V.
Magdysyuk
,
Maria
Diaz-Lopez
,
Biao
Cai
,
Nan
Gong
,
Yijue
Xu
,
Ivan
Hung
,
Zhehong
Gan
,
Sabyasachi
Sen
,
Hong-Tao
Sun
,
Thomas D.
Bennett
,
Xiaofeng
Liu
,
Yuanzheng
Yue
,
Jianrong
Qiu
Diamond Proposal Number(s):
[30401]
Abstract: Glassy metal coordination compounds (MCC) [e.g., metal-organic framework (MOF), coordination polymer, and metal inorganic-organic complex (MIOC)] are emerging members of the hybrid glass family. So far, a limited number of crystalline MCCs can be converted into glasses by the melt-quenching. Here, we report a universal wet-chemistry method, by which the super-sized supramolecular MIOC glasses can be synthesized from non-meltable MOFs. Alcohol and acid were used as agents to inhibit crystallization. The MIOC glasses demonstrate unique features including high transparency, shaping capability, and anisotropic network. Directional photoluminescence with a large polarization ratio (~47%) was observed from samples doped with organic dyes. This crystallization-suppressing approach enables fabrication of MCC glasses, which cannot be achieved by conventional vitrification methods, and thus allows for exploring new MCC glasses possessing photonic functionalities.
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Feb 2023
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