B18-Core EXAFS
I11-High Resolution Powder Diffraction
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Pu
Zhao
,
Lin
Ye
,
Guangchao
Li
,
Chen
Huang
,
Simson
Wu
,
Ping-Luen
Ho
,
Haokun
Wang
,
Tatchamapan
Yoskamtorn
,
Denis
Sheptyakov
,
Giannantonio
Cibin
,
Angus I.
Kirkland
,
Chiu C.
Tang
,
Anmin
Zheng
,
Wenjuan
Xue
,
Donghai
Mei
,
Kongkiat
Suriye
,
Shik Chi Edman
Tsang
Abstract: Synthesizing atomically dispersed synergistic active pairs is crucial yet challenging in developing highly active heterogeneous catalysts for various industrially important reactions. Here, a single molecular Re species is immobilized on the inner surface of a Y zeolite with Brønsted acid sites (BASs) within atomic proximity to form Re OMS–BAS active pairs for the efficient catalysis of olefin metathesis reactions (OMS: olefin metathesis site). The synergy within the active pairs is revealed by studying the coadsorption geometry of the olefin substrates over the active pairs by synchrotron X-ray and neutron powder diffraction. It is shown that the BAS not only facilitates olefin adsorption but also aligns the olefin molecule to the Re OMS for efficient intermediate formation. Consequently, for the cross-metathesis of ethene and trans-2-butene to propene, this catalyst shows high activity under mild reaction conditions without observable deactivation. The catalyst outperforms not only traditional ReOx-based catalysts but also the best industrially applicable WOx-based catalyst thus far that we discovered previously. The concept of using two isolated active sites of different functionalities within atomic proximity in a confined cavity can provide opportunities for designing synergistically catalytic materials.
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Mar 2021
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Liqun
Kang
,
Bolun
Wang
,
Andreas T.
Güntner
,
Siyuan
Xu
,
Xuhao
Wan
,
Yiyun
Liu
,
Sushila
Marlow
,
Yifei
Ren
,
Diego
Gianolio
,
Chiu C.
Tang
,
Vadim
Murzin
,
Hiroyuki
Asakura
,
Qian
He
,
Shaoliang
Guan
,
Juan J.
Velasco-Vélez
,
Sotiris E.
Pratsinis
,
Yuzheng
Guo
,
Feng Ryan
Wang
Open Access
Abstract: Electronic metal‐support interaction (EMSI) describes the electron flow between metal sites and a metal oxide support. It is generally used to follow the mechanism of redox reactions. In the study of CuO‐CeO2 redox, an additional flow of electron from metallic Cu to surface carbon species is observed via a combination of operando X‐ray absorption spectroscopy, synchrotron X‐ray powder diffraction, near ambient pressure‐near edge X‐ray absorption fine structure, and diffuse reflectance infrared Fourier transform spectroscopy. An electronic metal‐support‐carbon interaction (EMSCI) is proposed to explain the reaction pathway of CO oxidation. The EMSCI provides a complete picture of the mass and electron flow, which will help predict and improve the catalytic performance in the selective activation of CO2 , carbonate or carbonyl species in C1 chemistry.
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Mar 2021
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I12-JEEP: Joint Engineering, Environmental and Processing
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Yunhui
Chen
,
Samuel J.
Clark
,
Lorna
Sinclair
,
Chu Lun Alex
Leung
,
Sebastian
Marussi
,
Thomas
Connolley
,
Robert C.
Atwood
,
Gavin J.
Baxter
,
Martyn A.
Jones
,
Iain
Todd
,
Peter D.
Lee
Diamond Proposal Number(s):
[20096]
Abstract: Directed Energy Deposition Additive Manufacturing (DED-AM) is transformative for the production of larger, geometrically complex metallic components. However, the mechanical properties of titanium alloy DED-AM components do not always reach their full potential due to microstructural features including porosity and regions of lack of fusion. Using in situ and operando synchrotron X-ray imaging we gain insights into key laser-matter interaction and microstructural feature formation mechanisms during DED-AM of Ti-6242. Analysis of the process conditions reveals that laser power is dominant for build efficiency while higher traverse speed can effectively reduce lack of fusion regions. We also elucidate the mechanisms underlying several physical phenomena occurring during the deposition of titanium alloys, including the formation of a saddle-shaped melt pool and pore pushing. The findings of this work clarify the transient kinetics behind the DED-AM of titanium alloys and can be used as a guide for optimising industrial additive manufacturing processes.
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Mar 2021
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I04-1-Macromolecular Crystallography (fixed wavelength)
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Derun
Li
,
Yongqi
Deng
,
Abdelghani
Achab
,
Indu
Bharathan
,
Brett Andrew
Hopkins
,
Wensheng
Yu
,
Hongjun
Zhang
,
Sulagna
Sanyal
,
Qinglin
Pu
,
Hua
Zhou
,
Kun
Liu
,
Jongwon
Lim
,
Xavier
Fradera
,
Charles A.
Lesburg
,
Alfred
Lammens
,
Theodore A.
Martinot
,
Ryan D.
Cohen
,
Amy C.
Doty
,
Heidi
Ferguson
,
Elliott B.
Nickbarg
,
Mangeng
Cheng
,
Peter
Spacciapoli
,
Prasanthi
Geda
,
Xuelei
Song
,
Nadya
Smotrov
,
Pravien
Abeywickrema
,
Christine
Andrews
,
Chad
Chamberlin
,
Omar
Mabrouk
,
Patrick
Curran
,
Matthew
Richards
,
Peter
Saradjian
,
J. Richard
Miller
,
Ian
Knemeyer
,
Karin M.
Otte
,
Stella
Vincent
,
Nunzio
Sciammetta
,
Alexander
Pasternak
,
David Jonathan
Bennett
,
Yongxin
Han
Abstract: Indoleamine-2,3-dioxygenase-1 (IDO1) has emerged as an attractive target for cancer immunotherapy. An automated ligand identification system screen afforded the tetrahydroquinoline class of novel IDO1 inhibitors. Potency and pharmacokinetic (PK) were key issues with this class of compounds. Structure-based drug design and strategic incorporation of polarity enabled the rapid improvement on potency, solubility, and oxidative metabolic stability. Metabolite identification studies revealed that amide hydrolysis in the D-pocket was the key clearance mechanism for this class. Strategic survey of amide isosteres revealed that carbamates and N-pyrimidines, which maintained exquisite potencies, mitigated the amide hydrolysis issue and led to an improved rat PK profile. The lead compound 28 is a potent IDO1 inhibitor, with clean off-target profiles and the potential for quaque die dosing in humans.
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Mar 2021
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[20249]
Abstract: A detailed understanding of the local dynamics in ionic liquids remains an important aspect in the design of new ionic liquids as advanced functional fluids. Here, we use small-angle X-ray scattering and quasi-elastic neutron spectroscopy to investigate the local structure and dynamics in a model ionic liquid as a function of temperature and pressure, with a particular focus on state points (P,T) where the macroscopic dynamics, i.e., conductivity, is the same. Our results suggest that the initial step of ion transport is a confined diffusion process, on the nanosecond timescale, where the motion is restricted by a cage of nearest neighbors. This process is invariant considering timescale, geometry, and the participation ratio, at state points of constant conductivity, i.e., state points of isoconductivity. The connection to the nearest-neighbor structure is underlined by the invariance of the peak in the structure factor corresponding to nearest-neighbor correlations. At shorter timescales, picoseconds, two localized relaxation processes of the cation can be observed, which are not directly linked to ion transport. However, these processes also show invariance at isoconductivity. This points to that the overall energy landscape in ionic liquids responds in the same way to density changes and is mainly governed by the nearest-neighbor interactions.
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Mar 2021
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I02-Macromolecular Crystallography
I04-Macromolecular Crystallography
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Nur Zazarina
Ramly
,
Samuel R.
Dix
,
Sergey N.
Ruzheinikov
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Svetlana E.
Sedelnikova
,
Patrick J.
Baker
,
Yock-Ping
Chow
,
Fiona M.
Tomley
,
Damer P.
Blake
,
Kiew-Lian
Wan
,
Sheila
Nathan
,
David W.
Rice
Diamond Proposal Number(s):
[1218, 24447]
Open Access
Abstract: In infections by apicomplexan parasites including Plasmodium, Toxoplasma gondii, and Eimeria, host interactions are mediated by proteins including families of membrane-anchored cysteine-rich surface antigens (SAGs) and SAG-related sequences (SRS). Eimeria tenella causes caecal coccidiosis in chickens and has a SAG family with over 80 members making up 1% of the proteome. We have solved the structure of a representative E. tenella SAG, EtSAG19, revealing that, despite a low level of sequence similarity, the entire Eimeria SAG family is unified by its three-layer αβα fold which is related to that of the CAP superfamily. Furthermore, sequence comparisons show that the Eimeria SAG fold is conserved in surface antigens of the human coccidial parasite Cyclospora cayetanensis but this fold is unrelated to that of the SAGs/SRS proteins expressed in other apicomplexans including Plasmodium species and the cyst-forming coccidia Toxoplasma gondii, Neospora caninum and Besnoitia besnoiti. However, despite having very different structures, Consurf analysis showed that Eimeria SAG and Toxoplasma SRS families each exhibit marked hotspots of sequence hypervariability that map to their surfaces distal to the membrane anchor. This suggests that the primary and convergent purpose of the different structures is to provide a platform onto which sequence variability can be imposed.
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Mar 2021
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B23-Circular Dichroism
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Abstract: The preparation of discotic liquid crystal with a wide thermal nematic phase range remains a challenge. Here, a method to synthesise a class of discotic liquid crystal with exclusive and stable chiral nematic phase over a wide temperature range, based on pentaalkynylbenzene core, is presented and the mesogenic properties are well studied.
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Mar 2021
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I11-High Resolution Powder Diffraction
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Alexandra
Morscher
,
Matthew S.
Dyer
,
Benjamin B.
Duff
,
Guopeng
Han
,
Jacinthe
Gamon
,
Luke
Daniels
,
Yun
Dang
,
T. Wesley
Surta
,
Craig M.
Robertson
,
Frédéric
Blanc
,
John B.
Claridge
,
Matthew J.
Rosseinsky
Diamond Proposal Number(s):
[23666]
Open Access
Abstract: A hexagonal analogue, Li6SiO4Cl2, of the cubic lithium argyrodite family of solid electrolytes is isolated by a computation–experiment approach. We show that the argyrodite structure is equivalent to the cubic antiperovskite solid electrolyte structure through anion site and vacancy ordering within a cubic stacking of two close-packed layers. Construction of models that assemble these layers with the combination of hexagonal and cubic stacking motifs, both well known in the large family of perovskite structural variants, followed by energy minimization identifies Li6SiO4Cl2 as a stable candidate composition. Synthesis and structure determination demonstrate that the material adopts the predicted lithium site-ordered structure with a low lithium conductivity of ∼10–10 S cm–1 at room temperature and the predicted hexagonal argyrodite structure above an order–disorder transition at 469.3(1) K. This transition establishes dynamic Li site disorder analogous to that of cubic argyrodite solid electrolytes in hexagonal argyrodite Li6SiO4Cl2 and increases Li-ion mobility observed via NMR and AC impedance spectroscopy. The compositional flexibility of both argyrodite and perovskite alongside this newly established structural connection, which enables the use of hexagonal and cubic stacking motifs, identifies a wealth of unexplored chemistry significant to the field of solid electrolytes.
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Mar 2021
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I07-Surface & interface diffraction
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Diamond Proposal Number(s):
[21899]
Abstract: Organic charge transfer complexes (CTCs) with near-infrared absorption received growing interest in the past years, but the details of their photophysics, especially in thin films, remain largely unknown. We combined experimental and computational methods to thoroughly investigate and compare CTCs formed by tetracene with 2,2′-(perfluoronaphthalene-2,6-diylidene)dimalononitrile and 2,3,5,6-tetrafluoro-7,7,8,8,-tetracyanoquinodimethane, respectively. Using ultrafast transient absorption spectroscopy, the photophysics of these small bandgap CTCs was revealed, which is dominated by a sub-picosecond relaxation of the excitons back to the ground state. In equimolar blends, tetracene singlet fission is suppressed while in blends with excess of tetracene reduced lifetimes of tetracene, singlet and triplet excitons were found.
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Mar 2021
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I05-ARPES
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Paulina
Majchrzak
,
Ryan
Muzzio
,
Alfred J. H.
Jones
,
Davide
Curcio
,
Klara
Volckaert
,
Deepnarayan
Biswas
,
Jacob
Gobbo
,
Simranjeet
Singh
,
Jeremy T.
Robinson
,
Kenji
Watanabe
,
Takashi
Taniguchi
,
Timur K.
Kim
,
Cephise
Cacho
,
Jill A.
Miwa
,
Philip
Hofmann
,
Jyoti
Katoch
,
Soeren
Ulstrup
Diamond Proposal Number(s):
[24072]
Open Access
Abstract: To pinpoint the electronic and structural mechanisms that affect intrinsic and extrinsic performance limits of two‐dimensional material devices, it is of critical importance to resolve the electronic properties on the mesoscopic length scale of such devices under operating conditions. The present work utilizes angle‐resolved photoemission spectroscopy with nanoscale spatial resolution (nanoARPES) to map the quasiparticle electronic structure of a twisted bilayer graphene device. The dispersion and linewidth of the Dirac cones associated with top and bottom graphene layers are determined as a function of spatial position on the device under both static and operating conditions. The analysis reveals that microscopic rotational domains in the two graphene layers establish a range of twist angles from 9.8∘ to 12.7∘. Application of current and electrostatic gating lead to strong electric fields with peak strengths of 0.75 V/μm at the rotational domain boundaries in the device. These proof‐of‐principle results demonstrate the potential of nanoARPES to link mesoscale structural variations with electronic states in operating device conditions and to disentangle such extrinsic factors from the intrinsic quasiparticle dispersion.
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Mar 2021
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