Angle-resolved X-ray emission spectroscopy facility realized by an innovative spectrometer rotation mechanism at SPring-8 BL07LSU.

The X-ray emission spectrometer at SPring-8 BL07LSU has recently been upgraded with advanced modifications that enable the rotation of the spectrometer with respect to the scattering angle. This major upgrade allows the scattering angle to be flexibly changed within the range of 45-135°, which considerably simplifies the measurement of angle-resolved X-ray emission spectroscopy. To accomplish the rotation system, a sophisticated sample chamber and a highly precise spectrometer rotation mechanism have been developed. The sample chamber has a specially designed combination of three rotary stages that can smoothly move the connection flange along the wide scattering angle without breaking the vacuum. In addition, the spectrometer is rotated by sliding on a flat metal surface, ensuring exceptionally high accuracy in rotation and eliminating the need for any further adjustments during rotation. A control system that integrates the sample chamber and rotation mechanism to automate the measurement of angle-resolved X-ray emission spectroscopy has also been developed. This automation substantially streamlines the process of measuring angle-resolved spectra, making it far easier than ever before. Furthermore, the upgraded X-ray emission spectrometer can now also be utilized in diffraction experiments, providing even greater versatility to our research capabilities.

The role of carboxylate ligand orbitals in the breathing dynamics of a metal-organic framework by resonant X-ray emission spectroscopy.

Metal-organic frameworks (MOFs) exhibit structural flexibility induced by temperature and guest adsorption, as demonstrated in the structural breathing transition in certain MOFs between narrow-pore and large-pore phases. Soft modes were suggested to entropically drive such pore breathing through enhanced vibrational dynamics at high temperatures. In this work, oxygen K-edge resonant X-ray emission spectroscopy of the MIL-53(Al) MOF was performed to selectively probe the electronic perturbation accompanying pore breathing dynamics at the ligand carboxylate site for metal-ligand interaction. It was observed that the temperature-induced vibrational dynamics involves switching occupancy between antisymmetric and symmetric configurations of the carboxylate oxygen lone pair orbitals, through which electron density around carboxylate oxygen sites is redistributed and metal-ligand interactions are tuned. In turn, water adsorption involves an additional perturbation of π orbitals not observed in the structural change solely induced by temperature.

Double-Layered Perovskite Oxyfluoride Cathodes with High Capacity Involving O-O Bond Formation for Fluoride-Ion Batteries.

Developing electrochemical high-energy storage systems is of crucial importance toward a green and sustainable energy supply. A promising candidate is fluoride-ion batteries (FIBs), which can deliver a much higher volumetric energy density than lithium-ion batteries. However, typical metal fluoride cathodes with conversion-type reactions cause a low-rate capability. Recently, layered perovskite oxides and oxyfluorides, such as LaSrMnO4 and Sr3Fe2O5F2, have been reported to exhibit relatively high rate performance and cycle stability compared to typical metal fluoride cathodes with conversion-type reactions, but their discharge capacities (∼118 mA h/g) are lower than those of typical cathodes used in lithium-ion batteries. Here, we show that double-layered perovskite oxyfluoride La1.2Sr1.8Mn2O7-δF2 exhibits (de) intercalation of two fluoride ions to rock-salt slabs and further (de) intercalation of excess fluoride ions to the perovskite layer, leading to a reversible capacity of 200 mA h/g. The additional fluoride-ion intercalation leads to the formation of O-O bond in the structure for charge compensation (i.e., anion redox). These results highlight the layered perovskite oxyfluorides as a new class of active materials for the construction of high-performance FIBs.

Hydrogen-Bonded Structures of Water Molecules in Hydroxy-Functionalized Nanochannels of Columnar Liquid Crystalline Nanostructured Membranes Studied by Soft X-ray Emission Spectroscopy.

Here, we report a synchrotron-based high-resolution soft X-ray emission spectroscopy study on hydrogen-bonded structures of water molecules in the self-organized, hydroxy-group-functionalized one-dimensional nanochannels of liquid crystalline nanostructured membranes. The water molecules confined in the uncharged hydroxy-functionalized nanochannels (which have a diameter of about 1.5 nm) exhibit hydrogen-bonded structures close to those of bulk liquid water, even directly interacting with diol groups. These hydrogen-bonded structures contrast with the more distorted hydrogen bonding of water molecules confined in self-organized channels with a diameter of 0.6 nm formed by an analogous nanostructured membrane with a cationic moiety, which was explained by the ability of the channel functional groups to donate and accept hydrogen bonds in a confined space and the nanochannel diameter.

Chemical-state distributions in charged LiCoO2 cathode particles visualized by soft X-ray spectromicroscopy.

Lithium-ion deintercalation/intercalation during charge/discharge processes is one of the essential reactions that occur in the layered cathodes of lithium-ion batteries, and the performance of the cathode can be expressed as the sum of the reactions that occur in the local area of the individual cathode particles. In this study, the spatial distributions of the chemical states present in prototypical layered LiCoO2 cathode particles were determined at different charging conditions using scanning transmission X-ray microscopy (STXM) with a spatial resolution of approximately 100 nm. The Co L3- and O K-edge X-ray absorption spectroscopy (XAS) spectra, extracted from the same area of the corresponding STXM images, at the initial state as well as after charging to 4.5 V demonstrate the spatial distribution of the chemical state changes depending on individual particles. In addition to the Co L3-edge XAS spectra, the O K-edge XAS spectra of the initial and charged LiCoO2 particles are different, indicating that both the Co and O sites participate in charge compensation during the charging process possibly through the hybridization between the Co 3d and O 2p orbitals. Furthermore, the element maps of both the Co and O sites, derived from the STXM stack images, reveal the spatial distribution of the chemical states inside individual particles after charging to 4.5 V. The element mapping analysis suggests that inhomogeneous reactions occur on the active particles and confirm the existence of non-active particles. The results of this study demonstrate that an STXM-based spatially resolved electronic structural analysis method is useful for understanding the charging and discharging of battery materials.

Soft X-ray ptychography system using a Wolter mirror for achromatic illumination optics.

A soft X-ray ptychography system using a Wolter mirror for the illumination optics has been developed. By taking advantage of the achromaticity of the optics, the system is capable of seamlessly imaging at half-period resolution of 50 nm with a broad photon-energy range from 250 eV to 2 keV while maintaining the focal position. Imaging a mammalian cell at various wavelengths was demonstrated, and high-resolution visualization of organelle was achieved. Stereo imaging was also performed with a long working distance of 20 mm. In combination with in-situ/operando and tomographic measurements, this system will be a powerful tool for observing biological and material targets with complex features.

Operando resonant soft X-ray emission spectroscopy of the LiMn2O4 cathode using an aqueous electrolyte solution.

The Mn 3d electronic-structure change of the LiMn2O4 cathode during Li-ion extraction/insertion in an aqueous electrolyte solution was studied by operando resonant soft X-ray emission spectroscopy (RXES). The Mn L3 RXES spectra for the charged state revealed the Mn4+ state with strong charge-transfer from the O 2p to Mn 3d orbitals dominates, while for the open-circuit-voltage and discharged states it is ascribed to the mixture of sites with Mn3+ and Mn4+ states. The degree of charge transfer is significantly different between the Mn3+ and Mn4+ states, indicating that the redox reaction takes place on the strongly-hybridized Mn 3d-O 2p orbital rather than the localized Mn 3d orbital.

Infrared Spectra and Hydrogen-Bond Configurations of Water Molecules at the Interface of Water-Insoluble Polymers under Humidified Conditions.

Elucidating the state of interfacial water, especially the hydrogen-bond configurations, is considered to be key for a better understanding of the functions of polymers that are exhibited in the presence of water. Here, an analysis in this direction is conducted for two water-insoluble biocompatible polymers, poly(2-methoxyethyl acrylate) and cyclic(poly(2-methoxyethyl acrylate)), and a non-biocompatible polymer, poly(n-butyl acrylate), by measuring their IR spectra under humidified conditions and by carrying out theoretical calculations on model complex systems. It is found that the OH stretching bands of water are decomposed into four components, and while the higher-frequency components (with peaks at ∼3610 and ∼3540 cm-1) behave in parallel with the C═O and C-O-C stretching and CH deformation bands of the polymers, the lower-frequency components (with peaks at ∼3430 and ∼3260 cm-1) become pronounced to a greater extent with increasing humidity. From the theoretical calculations, it is shown that the OH stretching frequency that is distributed from ∼3650 to ∼3200 cm-1 is correlated to the hydrogen-bond configurations and is mainly controlled by the electric field that is sensed by the vibrating H atom. By combining these observed and calculated results, the configurations of water at the interface of the polymers are discussed.

Interpretation of the X-Ray Emission Spectra of Liquid Water through Temperature and Isotope Dependence.

The interpretation of x-ray emission spectroscopy (XES) spectra in terms of their sensitivity to the hydrogen bonding and the consequent microheterogeneity in liquid water has been debated over a decade. To shed a light on this problem, we report the theoretical reproduction of the debated 1b_{1} peaks observed in the XES spectra of liquid water using semiclassical Kramers-Heisenberg formula. The essence of the temperature and isotope dependence of the 1b_{1} double peaks is explained by molecular dynamics simulations including full vibrational (O─H stretching, bending, and) modes, rotational combined with the density functional theory and core-hole induced dynamics. Some inconsistencies exist with the experimental XES profile, which illustrates the need to employ a more precise theoretical calculations for both geometry sampling and electronic structure using a more sophisticated procedure.

Critical In-Plane Density of Polyelectrolyte Brush for the Ordered Hydrogen-Bonded Structure of Incorporated Water.

A polymer electrolyte brush is a reasonable platform to confine water molecules within a nanoscopic area to study their role in the function of interacting media because of their adjustable nanospace and charge by changing the in-plane density and side chains of the brush. Here, we demonstrate how the in-plane spacing of cationic polymer brush chains, poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMTAC), affects the hydrogen bond configuration of incorporated water using soft X-ray emission spectroscopy. At the critical in-plane density σ = 0.30 chains/nm2 of PMTAC, tetrahedrally coordinated water molecules started to melt into distorted or broken hydrogen-bonded configurations. Considering the charge on the quaternary ammonium cations, the electric field required to form a tetrahedrally coordinated hydrogen-bonded configuration was estimated as ∼500 kV cm-1 and is effective up to ∼1 nm from the surface of the polymer chain. These findings are useful for designing specific interface properties and the resultant surface function of polyelectrolyte-based materials.

Identification of Valence Electronic States Reflecting the Hydrogen Bonding in Liquid Ethanol.

The temperature-dependent X-ray emission spectra of liquid ethanol were calculated theoretically using a semi-classical approximation to the Kramers-Heisenberg formula, which includes the dynamical effects induced by a core-hole. Soft X-ray emission spectroscopic measurements were performed to discern the changes in the hydrogen bonding (h-bonding) structure of liquid ethanol using a temperature-controlled liquid cell at 241 and 313 K. The relative intensities of the peaks at approximately 526.5 and 527.1 eV varied with temperature, and the corresponding behavior was reproduced theoretically, although the variation with temperature in the calculated spectra were more enhanced than that in the experiment. The two peaks can be attributed to the 3a″ + 10a' mixed state and pure 3a″ state, respectively, depending on the behavior of the local h-bonding structure. The splitting of the 3a″ component occurred because of the h-bonding behavior of liquid ethanol. Furthermore, the size of the ethanol cluster decreased with an increase in temperature, mainly due to the breaking of the one-donor/one-acceptor type h-bonding. Our studies suggest that the electronic state of liquid ethanol reflects several types of h-bonding structures, and the ratios of these h-bonding types vary with temperature.

Hydration Mechanism in Blood-Compatible Polymers Undergoing Phase Separation.

Interactions involving intermediate water are crucial for the design of novel blood-compatible materials. Herein, we use a combination of atomic force microscopy, quartz crystal microbalance measurements, and soft X-ray emission spectroscopy to investigate the local hydrogen-bonded configuration of water on blood-compatible poly(2-methoxyethyl acrylate) and non-blood-compatible poly(n-butyl acrylate) grafted on a gold substrate. We find that the initially incorporated water induces polymer-dependent phase separation, facilitating further water uptake. For the blood-compatible polymer, tetrahedrally coordinated water coexists with water adsorbed on C═O groups in low-density regions of the grafted polymer surface, providing a scaffold for the formation of intermediate water. The amount of intermediate water is determined by the type of functional groups, local polymer configuration, and polymer morphology. Thus, blood compatibility is governed by the complex water/polymer interactions.

Hydrogen-Bonded Structure of Water in the Loop of Anchored Polyrotaxane Chain Controlled by Anchoring Density.

Hydrogen-bonded network of water surrounding polymers is expected to be one of the most relevant factors affecting biocompatibility, while the specific hydrogen-bonded structure of water responsible for biocompatibility is still under debate. Here we study the hydrogen-bonded structure of water in a loop-shaped poly(ethylene glycol) chain in a polyrotaxane using synchrotron soft X-ray emission spectroscopy. By changing the density of anchoring molecules, hydrogen-bonded structure of water confined in the poly(ethylene glycol) loop was identified. The XES profile of the confined water indicates the absence of the low energy lone-pair peak, probably because the limited space of the polymer loop entropically inhibits the formation of tetrahedrally coordinated water. The volume of the confined water can be changed by the anchoring density, which implies the ability to control the biocompatibility of loop-shaped polymers.

Improved developmental potential of mouse vitrified-warmed oocytes achieved by culturing in recovery medium with glutathione ethyl ester (GSH-OEt).

PURPOSE: The aim of the present study was to investigate the effect of glutathione ethyl ester (GSH-OEt) in the recovery medium on the developmental competence of mouse vitrified-warmed MII oocytes. METHODS: Vitrified-warmed oocytes were incubated for 1 h in recovery medium in the presence or absence of 0.5 mM GSH-OEt. The authors examined the effects of GSH-OEt, first on the levels of glutathione (GSH) and reactive oxygen species (ROS) in vitrified-warmed oocytes, and second, on in vitro blastocyst development, division speed to blastocysts, and total cell numbers of blastocysts from vitrified-warmed oocytes fertilized by Intracytoplasmic sperm injection (ICSI). RESULTS: Adding GSH-OEt to the recovery medium significantly (p < 0.05) increased GSH content and decreased ROS levels in vitrified-warmed oocytes. The blastocyst rate did not differ significantly between the two groups, but the speed of development to blastocysts in the GSH-OEt (+) group was significantly more rapid. In addition, the total blastocyst cell number was significantly higher in the GSH-OEt (+) group than in the GSH-OEt (-) group (92.8 ± 5.1 vs. 71.4 ± 3.5, p < 0.01). CONCLUSION: Adding GSH-OEt to the recovery medium of vitrified-warmed mouse oocytes enhances the development potential of oocytes and improves the quality of blastocysts.

Soft X-ray Emission Studies on Hydrate-Melt Electrolytes.

Highly salt-concentrated aqueous solutions are a new class of electrolytes, which provide a wide potential window exceeding 3 V and, hence, realize possibly inexpensive, safe, and high-energy-density storage devices. Herein, we investigate the evolution of the coordination structure and electronic state depending on the salt concentration through soft X-ray emission spectroscopy and first-principles molecular dynamics calculations. Close to the concentration limit, categorized as a "hydrate melt," a long-range hydrogen-bond network of water molecules disappears with emerging localized electronic states that resemble those in the gas phase. Such localized electronic states are attributed not only to their geometrically isolated nature but also to their dominant electrostatic interaction with Li+ cations. Therefore, the electrical properties of water in the hydrate melt can be more gaslike than liquidlike.

Simulation Study of the Effects of Interfacial Bonds on Adhesion and Fracture Behavior of Epoxy Resin Layers.

The adhesion and fracture behavior of tetraglycidyl-4,4'-diaminodiphenylmethane (TGDDM)/4,4'-diaminodiphenyl sulfone (44DDS)-bisphenol A diglycidyl ether (DGEBA)/44DDS layer interfaces were investigated by molecular dynamics (MD) simulation, mainly focusing on the role of covalent and noncovalent interactions. To accurately investigate the bond dissociation processes, the force field parameters of several bond potentials of the epoxy resin polymers were optimized by density functional theory calculations. In the MD simulations under a tensile load, small voids gradually developed without covalent bond dissociation in the plateau region. In the final large strain region, the stress rapidly increased with bond breaking, leading to failure. When the chemical bonds across the interface between the two layers were removed, the stress-strain curve in the initial elastic region was almost the same as that with interfacial bonds. This showed that the nonbonded interactions governed adhesion strength in the initial elastic region. In contrast, the bonded interactions at interfaces played important roles in the hardening regions because the bonded interactions made the major contribution to the fracture energies. We also investigated the effect of the etherification reaction in cross-linking. It was found that the etherification reaction mainly contributed to the behavior in the late region with large strain. These simulation results revealed that the nonbonded interactions, especially, van der Waals interactions, are important factors for adhesion of the different polymer layers in the small strain region up to the yield point.

Soft X-ray emission spectroscopy for the electronic state of water molecules influenced by plasma-treated multi-walled carbon nanotubes.

In this study, soft X-ray emission spectroscopy of an aqueous colloidal dispersion of multi-walled carbon nanotubes modified via the plasma process in an aqueous solution was performed for investigating the electronic state of water molecules on the colloidal particles. In the aqueous dispersion, reconstruction of the hydrogen-bonded network was implied by the O 1s spectral changes in the 1b1' and 1b1'' peaks. Furthermore, the O 1s spectral intensity around the 3a1 state was enhanced to an unusually broad energy range in comparison with previous studies. This unusual spectral change might be attributed to the hybridization of the electronic states of oxygen-containing functional groups on the surface of the plasma-modified multi-walled carbon nanotubes and that of the surrounding water molecules. Our observation indicates not only reconstruction of the hydrogen-bonded network in the aqueous dispersion but also a significant interaction of the electronic states between the water molecules and the plasma-modified multi-walled carbon nanotubes.

Serum Progesterone Levels with The Use of Four Different Types of Vaginal Progesterone in Frozen-Thawed Embryo Transfer Cycles and Related Pregnancy Outcomes.

BACKGROUND: Luteal phase support (LPS) is essential for hormone replacement therapy (HRT) for frozen-thawed embryo transfer (FET). However, the optimal dose and serum progesterone (P4) levels required for pregnancy are controversial. We attempted to determine the association between pregnancy outcomes and serum P4 levels administered via vaginal suppository for HRT-FET cycles on embryo transfer day. MATERIALS AND METHODS: This was a secondary analysis of the dataset from the EXCULL trial, which prospectively investigated pregnancy outcomes of four different P4 vaginal suppositories (Lutinus, Utrogestan, Luteum, and Crinone) for HRT-FET. It was conducted at a private fertility clinic between December 2016 to December 2017. During this trial, 235 cycles were divided into four groups based on serum P4 values (quartile [Q] 1 group: <7.8 ng/mL; Q2 group: 7.8-10.8 ng/mL; Q3 group: 10.8-13.7 ng/mL; Q4 group: >13.7 ng/mL). We investigated clinical pregnancy rate (CPR), positive fetal heart rate (FHR), live birth rate (LBR), and miscarriage rate (MR) for each group. A logistic regression analysis was performed using age, body mass index (BMI), and transferred embryos as covariates. RESULTS: Serum P4 values (ng/mL) of each drug were as follows: Lutinus, 13.3 ± 4.9; Utrogestan, 9.3 ± 3.3; Luteum, 13.6 ± 4.2; and Crinone, 8.7 ± 3.2 (mean ± standard deviation, P<0.001).The percentages of Utrogestan and Crinone were higher in the Q1 group, while the percentages of Lutinus and Luteum were higher in the Q4 group. Nonetheless, there were no statistical differences between the Q1 and Q4 groups in CPR, FHR, LBR, and MR. CONCLUSION: When vaginal P4 was used for FET, although serum P4 levels on transfer day differed based on the drug that was administered, no relationship was observed between serum progesteronelevels and pregnancy outcomes (Registration number: UMIN000032997).

Ion Selectivity of Water Molecules in Subnanoporous Liquid-Crystalline Water-Treatment Membranes: A Structural Study of Hydrogen Bonding.

We demonstrate hydrogen-bonded structures of water in self-organized subnanoporous water treatment membranes obtained using synchrotron-based high-resolution soft X-ray emission spectroscopy. The ion selectivity of these water treatment membranes is usually understood by the size compatibility of nanochannels in the membrane with the Stokes radius of hydrated ions, or by electrostatic interaction between charges inside the nanochannels and such ions. However, based on a comparison between the hydrogen-bonded structures of water molecules in the nanochannels of the water treatment membrane and those surrounding the ions, we propose a definite contribution of structural consistency among the associated hydrogen-bonded water molecules to the ion selectivity. Our observation delivers a novel concept to the design of water treatment membranes where water molecules in the nanochannel can be regarded as a part of the material that controls the ion selectivity.