I13-1-Coherence
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Diamond Proposal Number(s):
[28831]
Open Access
Abstract: Diffractive optical elements such as periodic gratings are fundamental devices in X-ray imaging – a technique that medical, material science, and security scans rely upon. Fabrication of such structures with high aspect ratios at the nanoscale creates opportunities to further advance such applications, especially in terms of relaxing X-ray source coherence requirements. This is because typical grating-based X-ray phase imaging techniques (e.g., Talbot self-imaging) require a coherence length of at least one grating period and ideally longer. In this paper, the fabrication challenges in achieving high-aspect ratio nanogratings filled with gold are addressed by a combination of laser interference and nanoimprint lithography, physical vapor deposition, metal assisted chemical etching (MACE), and electroplating. This relatively simple and cost-efficient approach is unlocked by an innovative post-MACE drying step with hexamethyldisilazane, which effectively minimizes the stiction of the nanostructures. The theoretical limits of the approach are discussed and, experimentally, X-ray nanogratings with aspect ratios >40 are demonstrated. Finally, their excellent diffractive abilities are shown when exposed to a hard (12.2 keV) monochromatic X-ray beam at a synchrotron facility, and thus potential applicability in phase-based X-ray imaging.
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Jan 2023
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E02-JEM ARM 300CF
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Diamond Proposal Number(s):
[30614, 29809, 32058]
Open Access
Abstract: Platinum (Pt) is regarded as a promising electrocatalyst for hydrogen evolution reaction (HER). However, its application in an alkaline medium is limited by the activation energy of water dissociation, diffusion of H+, and desorption of H*. Moreover, the formation of effective structures with a low Pt usage amount is still a challenge. Herein, guided by the simulation discovery that the edge effect can boost local electric field (LEF) of the electrocatalysts for faster proton diffusion, platinum nanocrystals on the edge of transition metal phosphide nanosheets are fabricated. The unique heterostructure with ultralow Pt amount delivered an outstanding HER performance in an alkaline medium with a small overpotential of 44.5 mV and excellent stability for 80 h at the current density of −10 mA cm−2. The mass activity of as-prepared electrocatalyst is 2.77 A mg−1Pt, which is 15 times higher than that of commercial Pt/C electrocatalysts (0.18 A mg−1Pt). The density function theory calculation revealed the efficient water dissociation, fast adsorption, and desorption of protons with hybrid structure. The study provides an innovative strategy to design unique nanostructures for boosting HER performances via achieving both synergistic effects from hybrid components and enhanced LEF from the structural edge effect.
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Nov 2022
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[22477]
Open Access
Abstract: Engineering the interplay of structural degrees of freedom that couple to external stimuli such as temperature and pressure is a powerful approach for material design. New structural degrees of freedom expand the potential of the concept, and coordination polymers as a chemically versatile material platform offer fascinating possibilities to address this challenge. Here, we report a new class of perovskite-like AB2X6 coordination polymers based on a [BX3] − ReO3-type host network ([Mn(C2N3)3] −), in which the spatial orientation of divalent A2+ cations ([R3N(CH2)nNR3]2+) with separated charge centers that bridge adjacent ReO3-cavities is introduced as a new geometric degree of freedom. Herringbone and head-to-tail order pattern of [R3N(CH2)nNR3]2+ cations are obtained by varying the separator length n and, together with distortions of the pseudocubic [BX3] − network, they determine the materials’ stimuli-responsive behavior such as counterintuitive large negative compressibility and uniaxial negative thermal expansion. This new family of coordination polymers highlights the chemists’ capabilities of designing matter on a molecular level to address macroscopic material functionality and underpins the opportunities of the design of structural degrees of freedom as a conceptual framework for rational material synthesis in the future.
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Aug 2022
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I22-Small angle scattering & Diffraction
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Yuanhao
Wu
,
Junyao
Yang
,
Alexander
Van Teijlingen
,
Alice
Berardo
,
Ilaria
Corridori
,
Jingyu
Feng
,
Jing
Xu
,
Maria-Magdalena
Titirici
,
Jose Carlos
Rodriguez-Cabello
,
Nicola M.
Pugno
,
Jiaming
Sun
,
Wen
Wang
,
Tell
Tuttle
,
Alvaro
Mata
Diamond Proposal Number(s):
[28002]
Open Access
Abstract: Materials that combine the functionalities of both of proteins and graphene are of great interest for the engineering of biosensing, drug delivery, and regenerative devices. Graphene oxide (GO) offers an opportunity to design GO-protein interactions but the need for harsh reduction processes to enable GO photoexcitation remains a limitation. A disinfector-assisted low temperature method to reduce GO-protein materials and fabricate surgical dressings with tuneable photothermal efficiency and bioactive properties for the postoperative treatment of melanoma is reported. The approach harnesses the capacity of 70% ethanol to penetrate the protein shell of microorganisms to infiltrate GO-protein complexes and reduce GO at low temperature (85 °C) while maintaining the material structure and bioactivity. Both experiments and coarse-grained simulations are used to describe the reduction process and assess the material properties. In vitro and in vivo validation revealed the capacity of the dressings to prevent tumor recurrence and promote healing after tumor resection.
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Jul 2022
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I10-Beamline for Advanced Dichroism
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Xiaoqian
Zhang
,
Wenqing
Liu
,
Wei
Niu
,
Qiangsheng
Lu
,
Wei
Wang
,
Ali
Sarikhani
,
Xiaohua
Wu
,
Chunhui
Zhu
,
Jiabao
Sun
,
Mitchel
Vaninger
,
Paul. F.
Miceli
,
Jianqi
Li
,
David J.
Singh
,
Yew San
Hor
,
Yue
Zhao
,
Chang
Liu
,
Liang
He
,
Rong
Zhang
,
Guang
Bian
,
Dapeng
Yu
,
Yongbing
Xu
Diamond Proposal Number(s):
[22532]
Abstract: One of the most promising avenues in 2D materials research is the synthesis of antiferromagnets employing 2D van der Waals (vdW) magnets. However, it has proven challenging, due in part to the complicated fabrication process and undesired adsorbates as well as the significantly deteriorated ferromagnetism at atomic layers. Here, the engineering of the antiferromagnetic (AFM) interlayer exchange coupling between atomically thin yet ferromagnetic CrTe2 layers in an ultra-high vacuum-free 2D magnetic crystal, Cr5Te8 is reported. By self-introducing interstitial Cr atoms in the vdW gaps, the emergent AFM ordering and the resultant giant magnetoresistance effect are induced. A large negative magnetoresistance (10%) with a plateau-like feature is revealed, which is consistent with the AFM interlayer coupling between the adjacent CrTe2 main layers in a temperature window of 30 K below the Néel temperature. Notably, the AFM state has a relatively weak interlayer exchange coupling, allowing a switching between the interlayer AFM and ferromagnetic states at moderate magnetic fields. This work represents a new route to engineering low-power devices that underpin the emerging spintronic technologies, and an ideal laboratory to study 2D magnetism.
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May 2022
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Abstract: Transparent conductive oxides (TCOs) exhibiting high near-infrared (NIR) transmittance are one of the key materials for highly efficient thin-film solar cells with widened spectral sensitivity. To realize excellent NIR transparency in a TCO film, developing a dopant providing high mobility (µ) carriers is quite important. Herein, it is demonstrated that W is a high-μ dopant in rutile SnO2, which is unexpected from the conventional strategy. A combination of electrical transport property measurements and hybrid density functional theory calculations reveals that W behaves as a singly charged donor (W5+) showing minimized ionized impurity scattering. This charge state is realized by the splitting of the W 5d t2g-states originating not only from the octahedral crystal field but also hybridization with the O 2p orbitals, whose contribution has not been considered in transition metal-doped TCOs. Hybridization between metal d orbital and O 2p orbitals would provide a new guide for designing a novel dopant of NIR transparent conductors.
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Dec 2021
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E02-JEM ARM 300CF
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Haisheng
Gong
,
Zengxi
Wei
,
Zhichao
Gong
,
Jingjing
Liu
,
Gonglan
Ye
,
Minmin
Yan
,
Juncai
Dong
,
Christopher
Allen
,
Jianbin
Liu
,
Kang
Huang
,
Rui
Liu
,
Guanchao
He
,
Shuangliang
Zhao
,
Huilong
Fei
Diamond Proposal Number(s):
[27260]
Abstract: Electrochemical H2O2 production through the 2-electron oxygen reduction reaction (ORR) is a promising alternative to the energy-intensive anthraquinone process. Herein, by simultaneously regulating the coordination number of the atomically dispersed cobalt sites and the nearby oxygen functional groups via a one-step microwave thermal shock, a highly selective and active Co-N-C electrocatalyst for H2O2 electrosynthesis that exhibits a high H2O2 selectivity (91.3%), outstanding mass activity (44.4 A g−1 at 0.65 V), and large kinetic current density (11.3 mA cm−2 at 0.65 V) in 0.1 m KOH is obtained. In strong contrast to the typical Co-N4 moieties for the 4-electron ORR, the present Co-N-C catalyst possesses a low-coordinated Co-N2 configuration and abundant epoxide groups, which work in synergy for promoting the 2-electron ORR, as demonstrated by a series of control experiments and theoretical simulations. This study may provide an effective avenue to modulating the composition and structure of electrocatalysts at the atomic scale, leading to the development of new electrocatalysts with unprecedented reactivity.
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Oct 2021
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I13-2-Diamond Manchester Imaging
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Clara
Anduix-Canto
,
Mark A.
Levenstein
,
Yi-Yeoun
Kim
,
Jose R. A.
Godinho
,
Alexander N.
Kulak
,
Carlos
Gonzalez Nino
,
Philip J.
Withers
,
Jonathan P.
Wright
,
Nikil
Kapur
,
Hugo K.
Christenson
,
Fiona C.
Meldrum
Diamond Proposal Number(s):
[13578, 17314]
Open Access
Abstract: Characterizing the pathways by which crystals form remains a significant challenge, particularly when multiple pathways operate simultaneously. Here, an imaging-based strategy is introduced that exploits confinement effects to track the evolution of a population of crystals in 3D and to characterize crystallization pathways. Focusing on calcium sulfate formation in aqueous solution at room temperature, precipitation is carried out within nanoporous media, which ensures that the crystals are fixed in position and develop slowly. The evolution of their size, shape, and polymorph can then be tracked in situ using synchrotron X-ray computed tomography and diffraction computed tomography without isolating and potentially altering the crystals. The study shows that bassanite (CaSO4 0.5H2O) forms via an amorphous precursor phase and that it exhibits long-term stability in these nanoscale pores. Further, the thermodynamically stable phase gypsum (CaSO4 2H2O) can precipitate by different pathways according to the local physical environment. Insight into crystallization in nanoconfinement is also gained, and the crystals are seen to grow throughout the nanoporous network without causing structural damage. This work therefore offers a novel strategy for studying crystallization pathways and demonstrates the significant impact of confinement on calcium sulfate precipitation, which is relevant to its formation in many real-world environments.
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Sep 2021
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B18-Core EXAFS
I22-Small angle scattering & Diffraction
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Jingyu
Feng
,
Rongsheng
Cai
,
Emanuele
Magliocca
,
Hui
Luo
,
Luke
Higgins
,
Giulio L. Fumagalli
Romario
,
Xiaoqiang
Liang
,
Angus
Pedersen
,
Zhen
Xu
,
Zhenyu
Guo
,
Arun
Periasamy
,
Dan
Brett
,
Thomas S.
Miller
,
Sarah J.
Haigh
,
Bhoopesh
Mishra
,
Maria-Magdalena
Titirici
Diamond Proposal Number(s):
[26201, 27900]
Open Access
Abstract: Atomically dispersed transition metal-nitrogen-carbon catalysts are emerging as low-cost electrocatalysts for the oxygen reduction reaction in fuel cells. However, a cost-effective and scalable synthesis strategy for these catalysts is still required, as well as a greater understanding of their mechanisms. Herein, iron, nitrogen co-doped carbon spheres (Fe@NCS) have been prepared via hydrothermal carbonization and high-temperature post carbonization. It is determined that FeN4 is the main form of iron existing in the obtained Fe@NCS. Two different precursors containing Fe2+ and Fe3+ are compared. Both chemical and structural differences have been observed in catalysts starting from Fe2+ and Fe3+ precursors. Fe2+@NCS-A (starting with Fe2+ precursor) shows better catalytic activity for the oxygen reduction reaction. This catalyst is studied in an anion exchange membrane fuel cell. The high open-circuit voltage demonstrates the potential approach for developing high-performance, low-cost fuel cell catalysts.
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Aug 2021
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[19114]
Open Access
Abstract: The preparation of MOFs including a metal with an easily exchangeable oxidation state, while maintaining the same crystal structure and stability, is of paramount importance for myriad applications. In this work, a new synthesis method is reported that can be used to prepare Ce/Zr‐MOFs (UiO‐66 structure) having only Ce(III), a mixed‐valence Ce(IV)/Ce(III), or only Ce(IV) cations, as desired. The materials are characterized using a large number of techniques, including X‐ray absorption and X‐ray photoelectron spectroscopies.
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May 2021
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