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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I11-High Resolution Powder Diffraction
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Abstract: Solid-state magnesium electrolytes may pave the way for novel types of rechargeable, sustainable, and cheap batteries with high volumetric and gravimetric capacities. There are, however, currently no solid-state magnesium electrolytes that fulfill the requirements for solid-state battery applications. Here, we present the synthesis, structure, and properties of six new methylamine magnesium borohydride compounds, α- and β-Mg(BH4)2·6CH3NH2, Mg(BH4)2·3CH3NH2, and α-, α′- and β-Mg(BH4)2·CH3NH2. The β-Mg(BH4)2·CH3NH2 polymorph displays a record high Mg2+ ionic conductivity of σ(Mg2+) = 1.50 × 10–4 S cm–1 at room temperature. The high Mg2+ conductivity of β-Mg(BH4)·CH3NH2 is facilitated by a one-dimensional chain-like structure interconnected by weak dihydrogen bonds and dispersion interactions, forming a migration pathway across the chains. The oxidative stability of Mg(BH4)2·CH3NH2 is ∼1.2 V vs Mg/Mg2+, and the reversible plating and stripping were confirmed by cyclic voltammetry and symmetric cell cycling, revealing high stability toward magnesium electrodes for at least 50 cycles at 60 °C.
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Jan 2023
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[17261, 20785]
Open Access
Abstract: The results are presented of a detailed combined experimental and theoretical investigation of the influence of coadsorbed electron-donating alkali atoms and the prototypical electron acceptor molecule 7,7,8,8-tetracyanoquinodimethane (TCNQ) on the Ag(100) surface. Several coadsorption phases were characterized by scanning tunneling microscopy, low-energy electron diffraction, and soft X-ray photoelectron spectroscopy. Quantitative structural data were obtained using normal-incidence X-ray standing wave (NIXSW) measurements and compared with the results of density functional theory (DFT) calculations using several different methods of dispersion correction. Generally, good agreement between theory and experiment was achieved for the quantitative structures, albeit with the prediction of the alkali atom heights being challenging for some methods. The adsorption structures depend sensitively on the interplay of molecule–metal charge transfer and long-range dispersion forces, which are controlled by the composition ratio between alkali atoms and TCNQ. The large difference in atomic size between K and Cs has negligible effects on stability, whereas increasing the ratio of K/TCNQ from 1:4 to 1:1 leads to a weakening of molecule–metal interaction strength in favor of stronger ionic bonds within the two-dimensional alkali–organic network. A strong dependence of the work function on the alkali donor–TCNQ acceptor coadsorption ratio is predicted.
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Jan 2023
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B16-Test Beamline
Optics
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Open Access
Abstract: High-speed adaptive correction of optics, based on real-time metrology feedback, has benefitted numerous scientific communities for several decades. However, it remains a major technological challenge to extend this concept into the hard x ray regime due to the necessity for active mirrors with single-digit nanometer height errors relative to a range of aspheric forms. We have developed a high-resolution, real-time, closed-loop “adaptive” optical system for synchrotron and x ray free electron laser (XFEL) applications. After calibration of the wavefront using x ray speckle scanning, the wavefront diagnostic was removed from the x ray beam path. Non-invasive control of the size and shape of the reflected x ray beam was then demonstrated by driving a piezoelectric deformable bimorph mirror at ∼1Hz
. Continuous feedback was provided by a 20 kHz direct measurement of the optical surface with picometer sensitivity using an array of interferometric sensors. This enabled a non-specialist operator to reproduce a series of pre-defined x ray wavefronts, including focused or non-Gaussian profiles, such as flattop intensity or multiple split peaks with controllable separation and relative amplitude. Such changes can be applied in any order and in rapid succession without the need for invasive wavefront diagnostic sensors that block the x ray beam for scientific usage. These innovations have the potential to profoundly change how x ray focusing elements are utilized at synchrotron radiation and XFEL sources and provide unprecedented dynamic control of photon beams to aid scientific discoveries in a wide range of disciplines.
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Jan 2023
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Open Access
Abstract: Enzymes with iron-containing active sites play crucial roles in catalysing a myriad of oxidative reactions essential to aerobic life. Defining the three-dimensional structures of iron enzymes in resting, oxy-bound intermediate and substrate-bound states is particularly challenging, not least because of the extreme susceptibility of the Fe(III) and Fe(IV) redox states to radiation-induced chemistry caused by intense X-ray or electron beams. The availability of novel sources such as X-ray free electron lasers has enabled structures that are effectively free of the effects of radiation-induced chemistry and allows time-resolved structures to be determined. Important to both applications is the ability to obtain in crystallo spectroscopic data to identify the redox state of the iron in any particular structure or timepoint.
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Dec 2022
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[29757]
Open Access
Abstract: Aqueous phase reforming (APR) of waste oxygenates offers the potential for sustainable hydrogen production. However, catalyst stability remains elusive, due to the aggressive hydrothermal conditions employed. Herein, we show that the catalytic performance and stability of Pt supported on LaAlO3 catalysts for glycerol APR is strongly influenced by the phase purity of LaAlO3. Calcination of the support at 700 °C produces the LaAlO3 perovskite phase and an amorphous lanthanum carbonate phase, which can be removed by calcination at higher temperature. Catalysts comprised of phase pure LaAlO3 were notably more active, with a support calcination temperature of 1100 °C resulting in 20.4% glycerol conversion (TOF 686 h−1) in a 2 h batch reaction. Interestingly, all the catalysts, regardless of LaAlO3 phase purity, eventually transform into Pt/LaCO3OH-AlO(OH) during reaction, but only in the presence of evolved carbon dioxide, itself produced from glycerol reforming. Studies using simulated reaction products showed that organic acid products (lactic acid), in the absence of CO2, facilitated La leaching and loss of crystallinity. A carbonate source (CO2) is essential to limit La leaching and form stable Pt/LaCO3OH. Pt supported on LaCO3OH and AlO(OH) are stable and active catalysts during APR reactions. Yet, the rate of perovskite phase decomposition strongly influences the final catalyst performance, with the initially phase impure LaAlO3 decomposing too quickly to facilitate Pt redistribution. LaAlO3 calcined at higher temperatures evolved more slowly and consequently produced more active catalysts.
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Dec 2022
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I11-High Resolution Powder Diffraction
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Abstract: A high-resolution synchrotron X-ray diffraction study of a single-crystal YCrO3 compound was employed to obtain its crystallographic information, such as lattice parameters, atomic positions, bond lengths and angles, and local crystalline distortion size and mode. The measurements were taken at 120 K (below the antiferromagnetic transition temperature TN ≃ 141.5 K), 300 K (between TN and the ferroelectric transition temperature TC ≃ 473 K) and 500 K (above TC). Using the high intensity of synchrotron X-rays, it was possible to refine collected patterns with the previously proposed noncentrosymmetric monoclinic structural model (P1211, No. 4) and determine detailed structural parameters. Meanwhile, for a controlled study, the data were refined with the centrosymmetric orthorhombic space group (Pmnb, No. 62). The lattice constants a, b and c and the unit-cell volume increased nearly linearly upon heating. With the P1211 space group, the distributions of bond lengths and angles, as well as local distortion strengths, were observed to be more dispersed. This implies that (i) the local distortion mode of Cr2O6 at 120 K correlates with the formation of canted antiferromagnetic order by Cr1–Cr2 spin interactions, primarily via intermediate O3 and O4 ions; and (ii) the previously reported dielectric anomaly may have a microscopic origin in the strain-balanced Cr1—O3(O4) and Cr2—O5(O6) bonds as well as the local distortion modes of Cr1O6 and Cr2O6 octahedra at 300 K. Local crystalline distortion is shown to be an important factor in the formation of ferroelectric order. The comprehensive set of crystallographic information reported here allows for a complete understanding of the unique magnetic and ferroelectric properties of YCrO3.
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Dec 2022
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I10-Beamline for Advanced Dichroism
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Peng
Chen
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Qi
Yao
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Junqi
Xu
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Qiang
Sun
,
Alexander J.
Grutter
,
Patrick
Quarterman
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Purnima P.
Balakrishnan
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Christy J.
Kinane
,
Andrew J.
Caruana
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Sean
Langridge
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Ang
Li
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Barat
Achinuq
,
Emily
Heppell
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Yuchen
Ji
,
Shanshan
Liu
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Baoshan
Cui
,
Jiuming
Liu
,
Puyang
Huang
,
Zhongkai
Liu
,
Guoqiang
Yu
,
Faxian
Xiu
,
Thorsten
Hesjedal
,
Jin
Zou
,
Xiaodong
Han
,
Haijun
Zhang
,
Yumeng
Yang
,
Xufeng
Kou
Diamond Proposal Number(s):
[30262]
Abstract: The intrinsic magnetic topological insulator MnBi2Te4 (MBT) provides a platform for the creation of exotic quantum phenomena. Novel properties can be created by modification of the MnBi2Te4 framework, but the design of stable magnetic structures remains challenging. Here we report ferromagnet-intercalated MnBi2Te4 superlattices with tunable magnetic exchange interactions. Using molecular beam epitaxy, we intercalate ferromagnetic MnTe layers into MnBi2Te4 to create [(MBT)(MnTe)m]N superlattices and examine their magnetic interaction properties using polarized neutron reflectometry and magnetoresistance measurements. Incorporation of the ferromagnetic spacer tunes the antiferromagnetic interlayer coupling of the MnBi2Te4 layers through the exchange-spring effect at MnBi2Te4/MnTe hetero-interfaces. The MnTe thickness can be used to modulate the relative strengths of the ferromagnetic and antiferromagnetic order, and the superlattice periodicity can tailor the spin configurations of the synthesized multilayers.
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Dec 2022
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[18995]
Open Access
Abstract: The formation of stacking faults and phase interstratification disorder in layered nickel(II) hydroxides during the chemical precipitation synthesis of materials using nickel(II) nitrate and potassium hydroxide solutions has been investigated in the temperature range of 5 °C to 95 °C and time intervals from 1 hour to 1 week. Stacking faulted materials were identified by broadening of the 00l reflections, while interstratified materials were identified through the splitting of the 001 into two lines. In contrast to the disorder concepts presented in previous studies of these materials, this work has shown through vibrational spectroscopy that both the alpha-phase and beta-phase hydroxides are present in materials described with stacking fault disorder, while layered hydroxysalts were additionally present in the materials considered to be interstratified. Standard mixtures of Ni3(OH)4(NO3)2 and β-Ni(OH)2 were prepared to investigate if the intensity of particular vibrational bands could be correlated with the proportion of the particular phases in mixtures. The intensities of the C2v nitrate infrared and Raman bands at 990 cm−1 and 1315 cm−1 were shown to correlate with the amount of layered hydroxynitrate incorporated in the phase, theoretically providing a method to determine the components in mixed compositions. Since disorder and phase impurities in layered nickel hydroxide materials affect both their electroactive stability and performance as cathode materials, this work has important implications in several research fields.
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Dec 2022
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I03-Macromolecular Crystallography
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Silvia
Gaggero
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Jonathan
Martinez-Fabregas
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Adeline
Cozzani
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Paul K.
Fyfe
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Malo
Leprohon
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Jie
Yang
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F. Emil
Thomasen
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Hauke
Winkelmann
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Romain
Magnez
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Alberto G.
Conti
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Stephan
Wilmes
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Elizabeth
Pohler
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Manuel
Van Gijsel Bonnello
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Xavier
Thuru
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Bruno
Quesnel
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Fabrice
Soncin
,
Jacob
Piehler
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Kresten
Lindorff-Larsen
,
Rahul
Roychoudhuri
,
Ignacio
Moraga
,
Suman
Mitra
Abstract: Cytokines interact with their receptors in the extracellular space to control immune responses. How the physicochemical properties of the extracellular space influence cytokine signaling is incompletely elucidated. Here, we show that the activity of interleukin-2 (IL-2), a cytokine critical to T cell immunity, is profoundly affected by pH, limiting IL-2 signaling within the acidic environment of tumors. Generation of lactic acid by tumors limits STAT5 activation, effector differentiation, and antitumor immunity by CD8+ T cells and renders high-dose IL-2 therapy poorly effective. Directed evolution enabled selection of a pH-selective IL-2 mutein (Switch-2). Switch-2 binds the IL-2 receptor subunit IL-2Rα with higher affinity, triggers STAT5 activation, and drives CD8+ T cell effector function more potently at acidic pH than at neutral pH. Consequently, high-dose Switch-2 therapy induces potent immune activation and tumor rejection with reduced on-target toxicity in normal tissues. Last, we show that sensitivity to pH is a generalizable property of a diverse range of cytokines with broad relevance to immunity and immunotherapy in healthy and diseased tissues.
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Dec 2022
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