SOLARIS National Synchrotron Radiation Centre

Abstract Resonant oscillators with stable frequencies and large quality factors help us to keep track of time with high precision. Examples range from quartz crystal oscillators in wristwatches to atomic oscillators in atomic clocks, which are, at present, our most precise time measurement devices 1 . The search for more stable and convenient reference oscillators is continuing 2–6 . Nuclear oscillators are better than atomic oscillators because of their naturally higher quality factors and higher resilience against external perturbations 7–9 . One of the most promising cases is an ultra-narrow nuclear resonance transition in 45 Sc between the ground state and the 12.4-keV isomeric state with a long lifetime of 0.47 s (ref. 10 ). The scientific potential of 45 Sc was realized long ago, but applications require 45 Sc resonant excitation, which in turn requires accelerator-driven, high-brightness X-ray sources 11 that have become available only recently. Here we report on resonant X-ray excitation of the 45 Sc isomeric state by irradiation of Sc-metal foil with 12.4-keV photon pulses from a state-of-the-art X-ray free-electron laser and subsequent detection of nuclear decay products. Simultaneously, the transition energy was determined as $${\mathrm{12,389.59}}_{+0.12\left({\rm{syst}}\right)}^{\pm 0.15\left({\rm{stat}}\right)}\,{\rm{eV}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mn>12,389.59</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.12</mml:mn> <mml:mfenced> <mml:mrow> <mml:mrow> <mml:mrow> <mml:mi>syst</mml:mi> </mml:mrow> </mml:mrow> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mo>±</mml:mo> <mml:mn>0.15</mml:mn> <mml:mfenced> <mml:mrow> <mml:mrow> <mml:mrow> <mml:mi>stat</mml:mi> </mml:mrow> </mml:mrow> </mml:mrow> </mml:mfenced> </mml:mrow> </mml:msubsup> <mml:mspace/> <mml:mi>eV</mml:mi> </mml:mrow> </mml:math> with an uncertainty that is two orders of magnitude smaller than the previously known values. These advancements enable the application of this isomer in extreme metrology, nuclear clock technology, ultra-high-precision spectroscopy and similar applications.

The manuscript presents the potential of surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS) for label-free characterization of extracellular microvesicles (EVs) and their isolated membranes derived from red blood cells (RBCs) at the nanoscale and at the single-molecule level, providing detection of a few individual amino acids, protein and lipid membrane compartments. The study shows future directions for research, such as investigating the use of the mentioned techniques for the detection and diagnosis of diseases. We demonstrate that SERS and TERS are powerful techniques for identifying the biochemical composition of EVs and their membranes, allowing the detection of small molecules, lipids, and proteins. Furthermore, extracellular vesicles released from red blood cells (REVs) can be broadly classified into exosomes, microvesicles, and apoptotic bodies, based on their size and biogenesis pathways. Our study specifically focuses on microvesicles that range from 100 to 1000 nanometres in diameter, as presented in AFM images. Using SERS and TERS spectra obtained for REVs and their membranes, we were able to characterize the chemical and structural properties of microvesicle membranes with high sensitivity and specificity. This information may help better distinguish and categorize different types of EVs, leading to a better understanding of their functions and potential biomedical applications.

Abstract The novel iron-oxide nanoparticles (NPs) stabilized with triethanolammonium oleate were produced. The specimens were divided into two groups: the top NPs (extracted from the supernatant) and the bottom NPs (nanoparticles sedimented at the bottom of the flask during centrifugation), respectively. The XRD and Mössbauer studies revealed a presence of the Fe 3 O 4 phase in both types of nanoparticles. Furthermore, the formation of maghemite layer on the surface of nanoparticles was observed. Average particle sizes determined from TEM and XRD studies were lower than the superparamagnetic limit for the magnetite NPs. For glycerol dispersions of both types of NPs, when exposed to 100 kHz external magnetic field, a significant heat release was observed. Furthermore, the contrasts of T 1 - and T 2 -weighted MR images were significantly dependent on the concentration of NPs in their water solutions. Additionally, the reductions of the relaxation times were different for the top and the bottom NPs. The viability studies of the colon cancer cells have shown low cytotoxicity of both types of NPs due to their coating with triethanolammonium oleate, which confirm the possibility to apply the NPs for MRI-guided hyperthermia. Moreover, the presence of NPs did not cause greatest increase of the number of apoptotic cells in the human dermal fibroblasts’ culture and has stimulated proliferation of those cells, revealing great potential of the NPs in regenerative medicine. Graphical abstract

from the recombinant capsid protein of brome mosaic virus (BMV). The analysis of VLPs was performed by Cryo-EM reconstructions and allowed us to visualize a few classes of VLPs, giving insight into the VLP self-assembly process. Apart from the mature icosahedral VLP practically identical with native virions, we describe putative VLP intermediates displaying non-icosahedral arrangements of capsomers, proposed to occur before the final disorder-order transition stage of icosahedral VLP assembly. Some of the described VLP classes show a lack of protein shell continuity, possibly resulting from too strong interaction with the cargo (in this case tRNA) with the capsid protein. We believe that our results are a useful prerequisite for the rational design of VLPs in the future and lead the way to the effective production of modified VLPs.

Using density functional theory, we study the lattice dynamical properties of magnetite (${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$) in the high-temperature cubic and low-temperature monoclinic phases. The calculated phonon dispersion curves and density of states are compared with the available experimental data obtained by inelastic neutron, inelastic x-ray, and nuclear inelastic scattering. We find a very good agreement between the theoretical and experimental results for the monoclinic $Cc$ structure revealing the strong coupling between the charge-orbital (trimeron) order and specific phonon modes. For the cubic phase, clear discrepancies arise due to fluctuation effects, which are not included in the calculation method. Despite this shortcoming, we argue that the main spectral features can be understood assuming that the strong trimeron-phonon coupling is extended above the Verwey transition, with lattice dynamics influenced by the short-range order instead of the average cubic structure. Our results indicate the validity of trimerons (and trimeron-phonon coupling) to explain the physics of magnetite much beyond their original formulation.

Cation doping is an effective strategy for improving the cyclability of layered oxide cathode materials through suppression of phase transitions in the high voltage region (&gt;~4.0V). In this study we choose Mg and Sc as representative dopants in P2- Na0.67Ni0.33Mn0.67O2. While both dopants have a positive effect on the cycling stability, they are found to influence the properties in the high voltage regime in different ways. Through a combination of RIXS, XRD, XAS, PDF analysis, and DFT, we show that it is more than just suppression of the P2 to O2 phase transition that is critical for promoting the favorable properties, and that the interplay between Ni and O activity are also critical aspects that dictate the performance. With Mg doping, we could enhance the Ni activity while simultaneously suppressing the O activity. This is surprising because it is in contrast to what has been reported in other Mn-based layered oxides where Mg is known to trigger oxygen redox. We address this contradiction by proposing a competing mechanism between Ni and Mg that impacts differences in O activity in Na0.67MgxNi0.33-xMn0.67O2 (x&lt;0&lt;0.33). These findings provide a new direction in understanding the effects of cation doping on the electrochemical behavior of layered oxides.

We show that in a uniform thickness NiO(111)/Fe(110) epitaxial bilayer system, at given temperature near 300 K, two magnetic states with orthogonal spin orientations can be stabilized in antiferromagnetic NiO. Field-free, reversible switching between these two antiferromagnetic states is demonstrated. The observed phenomena arise from the unique combination of precisely tuned interface magnetic anisotropy, thermal hysteresis of spin reorientation transition and interfacial ferromagnet/antiferromagnet exchange coupling. The possibility of field-free switching between two magnetic states in an antiferromagnet is fundamentally interesting and can lead to new ideas in heat assisted magnetic recording technology.

Next-generation, high-brilliance x-ray photon sources call for new x-ray optics. Here we demonstrate the feasibility of using monolithic diamond channel-cut crystals as high-heat-load, beam-multiplexing, narrow-band, mechanically-stable x-ray monochromators with high-power x-ray beams at cutting-edge, high-repetition-rate x-ray free-electron laser (XFEL) facilities. The diamond channel-cut crystals fabricated and characterized in these studies are designed as two-bounce Bragg reflection monochromators directing 14.4-keV or 12.4-keV x-rays within a 15-meV-bandwidth to $^{57}$Fe or $^{45}$Sc nuclear resonant scattering experiments, respectively. The crystal design allows out-of-band x-rays within a $\simeq 1$-eV XFEL bandwidth to be transmitted with minimal losses to alternative simultaneous experiments. Only $\lesssim 2$\% of the incident $\simeq 100$-W x-ray beam is absorbed in a 50-$\mu$m-thick first diamond crystal reflector, ensuring that the monochromator crystal is highly stable. Other x-ray optics applications of diamond channel-cut crystals are anticipated.

MnO 2 dissolution during first discharge in neutral Zn–MnO 2 batteries originates preferentially from Mn–Mn edge-sharing coordination.

2D structure of bismuth iodide brakes into fragments of different dimensionality and geometry upon reaction with substituted pyridinium iodides. The main factor determining the structure of the product is dipole moment of pyridinium cation.

Abstract Both preserved gapless states and gapping of Dirac states due to broken time reversal symmetry in bismuth chalcogenide topological insulators with surface and bulk magnetic impurities have been observed and reported in the literature. In order to shed more light on the mechanism of such effects we have performed comprehensive element selective study of the impact of Fe impurity position in the Bi 2 Se 3 lattice on its magnetism. The iron atoms were imbedded in the structure (volume dopants) or deposited on the surface (adatoms) and they revealed striking phenomena. Volume doping preserves non-trivial topology of Bi 1.98 Fe 0.02 Se 3 . Fe atoms not only substitute Bi, but also locate in van der Waals gap. The former are magnetically isotropic, while the latter reveal large magnetic moment (4.5 μ B ) with perpendicular anisotropy if located near the surface. Majority of Fe adatoms on the surface of Bi 2 Se 3 exhibit weaker moment (3.5 μ B ) with in-plane anisotropy, as expected for non-interacting species. Negligible interaction between surface electronic states and magnetic adatoms is confirmed by identical vibration spectra of Fe deposited on TI surface of Bi 2 Se 3 and non-TI surface of Bi 2 S 3 . The data gathered show how indispensable is the knowledge of the magnetic impurity distribution for applications of bismuth chalcogenide systems.

When a magnetic field is applied to a single crystal of magnetite at $124\phantom{\rule{0.16em}{0ex}}\mathrm{K}&gt;T&gt;50\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, the monoclinic ${c}_{M}$ axis, which is the easy magnetization axis, switches to one of the ⟨100⟩ cubic directions, nearest to the direction of the magnetic field, and the phenomenon known as an axis switching (AS) occurs. A global symmetry probe, resonant x-ray scattering, and a local probe, M\"ossbauer spectroscopy, are used to better understand the mechanism of axis switching. The behavior of three subsystems ordered below the Verwey transition temperature ${T}_{V}$, i.e., lattice distortion, an orbital, and charge orderings, was observed via resonant x-ray scattering as a function of an external magnetic field. This was preceded by calculation of selected peak intensities using the fdmnes code. The M\"ossbauer spectroscopy studies confirmed that the magnetic field triggers electronic rearrangements and atomic displacements. The structure observed after the process of axis switching is very similar to the one obtained after cooling below ${T}_{V}$ with the magnetic field applied along one of the initial ⟨100⟩ cubic directions and distinct from the cooling in the absence of a magnetic field. From all the experimental observations of the phenomenon done so far, it is clear that AS starts from the fluctuations between octahedral iron orbitals that ultimately lead to the Verwey transition, but also to the higher-temperature trimeron dynamics. Therefore, further observation of the axis switching may be a key point to the understanding of a majority of strongly correlated electronic behavior in magnetite as well as in other transition metal oxides.

The common approach to modify the thermoelectric activity of oxides is based on the concept of selective metal substitution. Herein, we demonstrate an alternative approach based on the formation of multiphase composites, at which the individual components have distinctions in the electric and thermal conductivities. The proof-of-concept includes the formation of multiphase composites between well-defined thermoelectric Co-based oxides: Ni, Fe co-substituted perovskite, LaCo0.8Ni0.1Fe0.1O3 (LCO), and misfit layered Ca3Co4O9. The interfacial chemical and electrical properties of composites are probed with the means of SEM, PEEM/XAS, and XPS tools, as well as the magnetic susceptibility measurements. The thermoelectric power of the multiphase composites is evaluated by the dimensionless figure of merit, ZT, calculated from the independently measured electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (λ). It has been demonstrated that the magnitude’s electric and thermal conductivities depend more significantly on the composite interfaces than the Seebeck coefficient values. As a result, the highest thermoelectric activity is observed at the composite richer on the perovskite (i.e., ZT = 0.34 at 298 K).

Correction for 'Fine tuning of ferromagnet/antiferromagnet interface magnetic anisotropy for field-free switching of antiferromagnetic spins' by M. Slęzak et al., Nanoscale, 2020, DOI: 10.1039/d0nr04193a.

Photoemission is one of the fundamental processes that describes the generation of charged particles from materials irradiated by photons. The continuous progress in the development of ultrashort lasers allows investigation into the dynamics of the process at the femtosecond timescale. Here we report about experimental measurements using two ultrashort ultraviolet laser pulses to temporally probe the electrons release from a copper cathode in a radio-frequency photoinjector. By changing their relative delay, we studied how the release mechanism is affected by two-photon photoemission when tens of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">G</mml:mi> <mml:mi mathvariant="normal">W</mml:mi> </mml:mrow> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>/</mml:mo> </mml:mrow> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">c</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:mrow> <mml:mn>2</mml:mn> </mml:msup> </mml:math> intensities are employed. We evaluated the limits it poses on the achievable beam brightness and analyzed the resulting emission yield in terms of the electronic temperature by modeling the cathode as a two-temperature system.

This study aims to thoroughly understand the local structure of copper phosphonate groups covalently attached via propyl arms to pores interior of SBA-15 mesoporous silica. The studied sample contains 20% of propyl-POO2Cu groups attached to the mesoporous silica matrix as host material. X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) at the copper K-edge were utilized to discern the valence state and geometric arrangement of copper sites within the pores. Various machine learning techniques, including principal component analysis, K-means clustering, and neural networks, were applied to theoretically calculated XANES spectra. This facilitated our quantitative analysis of the experimental spectrum and the extension of the EXAFS equation fit to the second shell. Additional molecular structure analysis was performed based on Raman scattering supported by numerical simulations. Nuclear magnetic resonance aided in analyzing the silicon and phosphorus environment. Results indicate that copper atoms are coordinated by two phosphonate groups, forming a pseudo-bi-trigonal pyramid with surrounding oxygen atoms. These results contribute to a better understanding of the physical properties of the studied nanocomposite material. This, in turn, makes it possible to optimize the molecular structure of materials to optimize their antimicrobial and photonic properties, making them useful in practice.

We present the in situ modification of the magnetocrystalline anisotropy of iron-rich cobalt-ferrite epitaxial islands by changing their composition. Crystalline cobalt-ferrite spinel islands have been grown by oxygen-assisted molecular beam epitaxy on a Ru(0001) single crystal. The micro-crystals are several micrometers wide with heights of tens of nanometers. Their spatially-resolved vector magnetization is mapped by x-ray magnetic circular dichroism in photoemission microscopy at the L 3 absorption edges of Co and Fe. Thick islands present a closure-like magnetic domain structure with the magnetization directions predominantly aligned along the projections of the easy magnetic axes onto the (111) surface plane. Thinner islands are more affected by growth defects and present a more complex domain structure. Upon deposition of additional Fe in an oxygen background pressure, Co is found to segregate out of the spinel islands, while their Fe content increases. This produces a reduction in the magnetocrystalline anisotropy, which manifests as a reorientation of the magnetization directions towards the edges of the islands, reflecting an increased contribution of the shape anisotropy. • 3D islands of iron-rich cobalt ferrites are grown by MBE and modified in-situ by the deposition of iron. • The Fe deposition induces the segregation of metallic cobalt out of the islands into surrounding areas. • The islands domains evolve from being dictated by magneto-crystalline to shape anisotropy. • The changes can be understood by the reduction in cobalt content in the islands.

The histidine biosynthetic pathway (HBP) is targeted for herbicide design with preliminary success only regarding imidazole-glycerol phosphate dehydratase (IGPD, EC 4.2.1.19), or HISN5, as referred to in plants. HISN5 catalyzes the sixth step of the HBP, in which imidazole-glycerol phosphate (IGP) is dehydrated to imidazole-acetol phosphate. In this work, we present high-resolution cryoEM and crystal structures of Medicago truncatula HISN5 ( Mt HISN5) in complexes with an inactive IGP diastereoisomer and with various other ligands. Mt HISN5 can serve as a new model for plant HISN5 structural studies, as it enables resolving protein-ligand interactions at high (2.2 Å) resolution using cryoEM. We identified ligand-binding hotspots and characterized the features of plant HISN5 enzymes in the context of the HISN5-targeted inhibitor design. Virtual screening performed against millions of small molecules not only revealed candidate molecules but also identified linkers for fragments that were experimentally confirmed to bind. Based on experimental and computational approaches, this study provides guidelines for designing symmetric HISN5 inhibitors that can reach two neighboring active sites. Finally, we conducted analyses of sequence similarity networks revealing that plant HISN5 enzymes derive from cyanobacteria. We also adopted a new approach to measure Mt HISN5 enzymatic activity using isothermal titration calorimetry and enzymatically synthesized IGP.

Abstract X-ray spectroscopy is a demanded tool across multiple user communities. Here we report on a new station for X-ray emission spectroscopy at the Extreme Light Infrastructure Beamlines Facility. The instrument utilizes the von Hamos geometry and works with a number of different sample types, notably including liquid systems. We demonstrate a simple and reliable method for source position control using two cameras. This approach addresses energy calibration dependence on sample position, which is a characteristic source of measurement uncertainty for wavelength dispersive spectrometers in XES arrangement. We also present a straightforward procedure for energy calibration of liquid and powder samples to a thin film reference. The developed instrumentation enabled us to perform the first experimental determination of the Kα lines of liquidized K 3 Fe(CN) 6 as well as powdered and liquidized FeNH 4 (SO 4 ) 2 . Finally, we report on proof-of-principle use of a colliding jet liquid sample delivery system in an XES experiment.

Recent years have witnessed a steady progress towards blending two-dimensional quantum materials into technology, with future applications often rooted in the electronic structure. Since crossings and inversions of electronic bands with different orbital characters determine intrinsic quantum transport properties, knowledge of the orbital character is essential. Here, we benchmark angle-resolved photoelectron emission spectroscopy (ARPES) as a tool to experimentally derive orbital characters. For this purpose we study the valence electronic structure of two technologically relevant quantum materials, graphene and <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>WSe</a:mi><a:mn>2</a:mn></a:msub></a:math>, and focus on circular dichroism that is believed to provide sensitivity to the orbital angular momentum. We analyze the contributions related to angular atomic photoionization profiles, interatomic interference, and multiple scattering. Regimes in which initial-state properties could be disentangled from the ARPES maps are critically discussed and the potential of using circular dichroic ARPES as a tool to investigate the spin polarization of initial bands is explored. For the purpose of generalization, results from two additional materials, <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:msub><b:mi>GdMn</b:mi><b:mn>6</b:mn></b:msub><b:msub><b:mi>Sn</b:mi><b:mn>6</b:mn></b:msub></b:mrow></b:math> and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:msub><c:mi>PtTe</c:mi><c:mn>2</c:mn></c:msub></c:math>, are presented in addition. This research demonstrates rich complexity of the underlying physics of circular dichroic ARPES, providing insights that will shape the interpretation of both past and future circular-dichroic ARPES studies.