Near-edge Spectroscopy Research Articles

(Digital Presentation) Mn-VOH Micro Flakes Interconnected with CNT As Cathodes for Aqueous Zinc-Ion Batteries

With increasing energy consumption and environmental awareness, the demand for next-generation energy storage systems has grown. Aqueous zinc-ion batteries (AZIBs) have received considerable attention among various types of energy storage devices due to their high safety standards and low cost. Herein, we present a sustainable synthesis approach for synthesizing MnVOH@CNT composite material and its application as the cathode material for aqueous Zinc-ion batteries (AZIBs) by using a low-temperature (120 °C) hydrothermal process. Moreover, with a continuous network structure and expanded interlayer spacing, such a configuration can provide rapid electron transfer kinetics (DZn 2+: 10 ̶ 11−10−12 cm2 s−1) while ensuring close interaction between MnVOH and CNT during cycling. The materials have excellent electrochemical properties as cathodes in the AZIBs. The resultant batteries exhibit a high intercalation storage capacity of c.a. 380 mAh g−1 at acurrent density of 0.1 A g−1, minimized polarization, and excellent capacity retention of c.a. 90% after 300 cycles. Furthermore, operando synchrotron X-ray absorption, near-edge spectroscopy was used for the first time to confirm the Zn2+ charge-storage mechanism. Operando synchrotron X-ray diffraction, studies were also done to better understand the structural changes of the MnVOH@CNT nanocomposite during the discharge/charge processes. Meanwhile, the ZIBs using MnVOH@CNT as cathode can maintain an energy density of c.a. 190 Wh kg−1 at a high power density of 3.2 kW kg−1, demonstrating that MnVOH@CNT is a promising cathode material for high-performance cathode material for low-cost and environment-friendly AZIB applications. KEYWORDS: AZIB, MnVOH@CNT, operando XANES, operando XRD, cathode material

Benchmarking Plane Waves Quantum Mechanical Calculations of Iron(II) Tris(2,2′-bipyridine) Complex by X-ray Absorption Spectroscopy

In this work, we used, for the first time, a computational Self-Consistent Field procedure based on plane waves to describe the low and high spin conformational states of the complex [Fe(bpy)3]2+. The results obtained in the study of the minimum energy structures of this complex, a prototype of a wide class of compounds called Spin Cross Over, show how the plane wave calculations are in line with the most recent studies based on gaussian basis set functions and, above all, reproduce within acceptable errors the experimental spectra of X-ray absorption near-edge structure spectroscopy (XANES). This preliminary study shows the capabilities of plane wave methods to correctly describe the molecular structures of metal-organic complexes of this type and paves the way for future even complex computational simulations based on the energy gradient, such as Nudge Elastic Band or ab-initio Born-Oppenheimer molecular dynamics.

A primordial 15N-depleted organic component detected within the carbonaceous chondrite Maribo

We report on the detection of primordial organic matter within the carbonaceous chondrite Maribo that is distinct from the majority of organics found in extraterrestrial samples. We have applied high-spatial resolution techniques to obtain C-N isotopic compositions, chemical, and structural information of this material. The organic matter is depleted in 15N relative to the terrestrial value at around δ15N ~ -200‰, close to compositions in the local interstellar medium. Morphological investigations by electron microscopy revealed that the material consists of µm- to sub-µm-sized diffuse particles dispersed within the meteorite matrix. Electron energy loss and synchrotron X-ray absorption near-edge structure spectroscopies show that the carbon functional chemistry is dominated by aromatic and C=O bonding environments similar to primordial organics from other carbonaceous chondrites. The nitrogen functional chemistry is characterized by C-N double and triple bonding environments distinct from what is usually found in 15N-enriched organics from aqueously altered carbonaceous chondrites. Our investigations demonstrate that Maribo represents one of the least altered CM chondrite breccias found to date and contains primordial organic matter, probably originating in the interstellar medium.

Artifacts from manganese reduction in rock samples prepared by focused ion beam (FIB) slicing for X-ray microspectroscopy

Abstract. The spatial distribution of transition metal valence states is of broad interest in the microanalysis of geological and environmental samples. An example is rock varnish, a natural manganese (Mn)-rich rock coating, whose genesis mechanism remains a subject of scientific debate. We conducted scanning transmission X-ray microscopy with near-edge X-ray absorption fine-structure spectroscopy (STXM-NEXAFS) measurements of the abundance and spatial distribution of different Mn oxidation states within the nano- to micrometer thick varnish crusts. Such microanalytical measurements of thin and hard rock crusts require sample preparation with minimal contamination risk. Focused ion beam (FIB) slicing was used to obtain ∼100–1000 nm thin wedge-shaped slices of the samples for STXM, using standard parameters. However, while this preparation is suitable for investigating element distributions and structures in rock samples, we observed artifactual modifications of the Mn oxidation states at the surfaces of the FIB slices. Our results suggest that the preparation causes a reduction of Mn4+ to Mn2+. We draw attention to this issue, since FIB slicing, scanning electron microscopy (SEM) imaging, and other preparation and visualization techniques operating in the kilo-electron-volt range are well-established in geosciences, but researchers are often unaware of the potential for the reduction of Mn and possibly other elements in the samples.

Pseudo-equilibrium equation of calcium phosphate precipitation from aqueous solution.

An X-ray amorphous phase is frequently present at the early stage of calcium phosphate crystallization, and the relevant solution chemistry is essential for understanding the mechanism of reaction. Here, we report a quantitative study of a series of reaction systems at pseudo-equilibrium states. We determined the composition of solutions and the quantities of the precipitate samples, and characterized the long- and short-range order of the precipitate using X-ray diffraction and synchrotron X-ray absorption near-edge structure spectroscopy, respectively. We found that, in a particle with multiple structural units, only a fraction of the units was able to reach pseudo-equilibrium with the solution composition, which represents the average number of surficial clusters per unit. These findings enabled us to propose a general form of the equilibrium constant equation. The equation fits the pseudo-equilibrium data well, and it converts to the "solubility product (Ksp)" and the conventional "reaction quotient" in two limit cases, respectively. Further, using a cube model, we derived a "particle equation" that reveals the connection between the particle structure and the form of equilibrium constant equation. The dependency of the form of pseudo-equilibrium equation on the structure and size of the precipitate reveals a fundamental relation in chemistry, and its applicability remains to be examined in other reaction systems, such as those involving nanocrystals and porous materials.

Determination and speciation of phosphorus in fertilizers and mineral supplements for cattle by X-ray absorption near-edge structure spectroscopy: a simple nondestructive method

X-ray absorption near-edge structure (XANES) spectroscopy was used to determine phosphorus species in agricultural inputs.

Ab Initio Study of Covalency in the Ground versus Core-Excited States and X-ray Absorption Spectra of Actinide Complexes.

Relativistic multireference ab initio wave function calculations within the restricted active space (RAS) framework were performed to calculate metal and ligand X-ray absorption (XAS) near-edge spectroscopy (XANES) intensities for the metal M4,5 edges of [PuO2(H2O)5]2+, [AnVIO2]2+ (An = U, Np, Pu), and [AmCl6]3- and the Cl K edge of the Am complex. The extent of An(5f)-ligand bonding was determined via natural localized molecular orbital analyses of the relevant spin-orbit coupled multireference states. The calculated spectra are in good agreement with experiments and allow a detailed assignment of the observed spectral features. The XANES M4,5-edge spectra are representative of the actinide orbital covalency in the probed core-excited states, which may be different from the ground-state covalency. An assignment of ground-state An orbital covalency based on XAS spectra should therefore be made with caution.

小型掠入射式近边X射线吸收谱仪的设计

小型掠入射式近边X射线吸收谱仪的设计

Evolution of Eu valence and superconductivity in layered Eu0.5La0.5FBiS2−xSex system

We have studied the effect of Se substitution on Eu valence in a layered ${\mathrm{Eu}}_{0.5}{\mathrm{La}}_{0.5}{\mathrm{FBiS}}_{2\ensuremath{-}x}{\mathrm{Se}}_{x}$ superconductor using a combined analysis of x-ray absorption near-edge structure (XANES) and x-ray photoelectron spectroscopy (XPS) measurements. Eu ${L}_{3}$-edge XANES spectra reveal that Eu is in the mixed valence state with coexisting ${\mathrm{Eu}}^{2+}$ and ${\mathrm{Eu}}^{3+}$. The average Eu valence decreases sharply from $\ensuremath{\sim}2.3$ for $x=0.0$ to $\ensuremath{\sim}2.1$ for $x=0.4$. Consistently, Eu $3d$ XPS shows a clear decrease in the average valence by Se substitution. Bi $4f$ XPS indicates that effective charge carriers in the ${\mathrm{BiCh}}_{2}$ (Ch = S, Se) layers are slightly increased by Se substitution. On the basis of the present results it has been discussed that the metallic character induced by Se substitution in ${\mathrm{Eu}}_{0.5}{\mathrm{La}}_{0.5}{\mathrm{FBiS}}_{2\ensuremath{-}x}{\mathrm{Se}}_{x}$ is likely to be due to increased in-plane orbital overlap driven by reduced in-plane disorder that affects the carrier mobility.

Fabrication and characterization of fine-grained 316L steel with 2.0 mass% TiC

ABSTRACTDevelopment of fine grain 316L with small amount of TiC for high radiation-tolerant performance was tried considering the fabrication process of thermo-mechanical treatments. The materials obtained are UFG316L+2.0 mass% TiC with the grain size of 90–270 nm, depending on the final annealing temperature from 700 ℃ to 900 ℃. The materials were examined by transmission electron microscopy observation, X-ray absorption near-edge structure spectroscopy, high voltage electron microscope electron irradiation and stress corrosion cracking by crevice bent beam method in high-temperature water with 8 ppm dissolved oxygen. The test results showed that the material is generally of excellent quality. Especially void swelling induced by the electron irradiation at 400 ℃ is less than 1/10 compared to the commercial SUS316L.

XANES and micro-Raman spectroscopy study of the barium titanosilicates BaTiSi2O7 and BaTiSi4O11

The coordination environment around Ti4+ in the photoluminescent compound BaTiSi2O7 and in BaTiSi4O11 was investigated with X-ray absorption near-edge structure spectroscopy and micro-Raman spectroscopy. The presence of VTi in TiO5 pyramidal units with one short Ti–O bond involving the apical oxygen was detected in both compounds. Interpretation of the vibrational signal from the silicate framework suggested that BaTiSi4O11 is a metasilicate containing building units of SiO4 tetrahedra, which are larger than in other barium titanosilicates. These results confirmed the same structural environment of Ti4+ as recently disclosed by structure refinement of BaTiSi2O7 and provided new insights into the unknown structure of BaTiSi4O11 in the light of the study of its physical properties as potential functional material.

X-ray spectral diagnostics of synthetic lanthanide silicates

Potassium and rare-earth (Eu, Sm, Yb, Ce) silicate and aluminosilicate crystals are hydrothermally synthesized under isothermal conditions at 500°C and a pressure of 100 MPa. The chemical and structural formulas of the synthesized compounds HK6Eu[Si10O25], K7Sm3[Si12O32], K2Sm[AlSi4O12] · 0.375H2O, K4Yb2[Si8O21], and K4Ce2[Al2Si8O24] are determined. In addition, a synthesis product with Eu, in which the dominant phase is assumed to be K3Eu3+[Si6O15] · 2H2O, is studied. The oxidation state of lanthanides in the silicates under study is determined based on X-ray absorption near-edge structure spectroscopy. The Eu L3-, Sm L3-, Yb L3-, and Ce L3-edge X-ray absorption spectra of the studied silicates and reference samples are recorded using a Rigaku R-XAS laboratory spectrometer. As reference samples, Eu2+S, Eu3+F3, Eu23+O3, Sm23+O3, Yb23+O3, Yb3+F3, Yb3+Cl3, Ce23+O3, and Ce4+O2 are used. Comparison of the absorption edge energies of lanthanide silicates and reference samples shows that Eu, Sm, Yb, and Cе in all the samples studied are in the oxidation state 3+. The synthesized silicates will supplement our knowledge of possible rare-earth minerals existing in hydrothermal systems, which is important for analyzing the distribution spectra of rare elements, which are widely used for diagnostics of geochemical processes and determination of sources of ore materials.

Characterization of Microbe-Mineral Interfacial Interaction Based on Synchrotron Radiation Techniques

This article presents the progress on characterization of the interfacial interaction between sulfur oxidizing microbes and sulfide minerals by using of synchrotron radiation-based techniques including S/Fe/Cu X-ray absorption near-edge structure spectroscopy (XANES), X-ray Diffraction (XRD), micro-X-ray fluorescence (μ-XRF) mapping and micro-scanning transmission X-ray microscopy (μ-STXM) imaging, together with other accessory approaches such as SEM/EDS, Raman spectroscopy, FT-IR spectroscopy, and electrochemical methods as well as comparative proteomics methodology.

Do selenium hyperaccumulators affect selenium speciation in neighboring plants and soil? An X-Ray Microprobe Analysis

Neighbors of Se hyperaccumulators Stanleya pinnata and Astragalus bisulcatus were found earlier to have elevated Se levels. Here we investigate whether Se hyperaccumulators affect Se localization and speciation in surrounding soil and neighboring plants. X-ray fluorescence mapping and X-ray absorption near-edge structure spectroscopy were used to analyze Se localization and speciation in leaves of Artemisia ludoviciana, Symphyotrichum ericoides and Chenopodium album growing next to Se hyperaccumulators or non-accumulators at a seleniferous site. Regardless of neighbors, A. ludoviciana, S. ericoides and C. album accumulated predominantly (73–92%) reduced selenocompounds with XANES spectra similar to the C-Se-C compounds selenomethionine and methyl-selenocysteine. Preliminary data indicate that the largest Se fraction (65–75%), both in soil next to hyperaccumulator S. pinnata and next to nonaccumulator species was reduced Se with spectra similar to C-Se-C standards. These same C-Se-C forms are found in hyperaccumulators. Thus, hyperaccumulator litter may be a source of organic soil Se, but soil microorganisms may also contribute. These findings are relevant for phytoremediation and biofortification since organic Se is more readily accumulated by plants, and more effective for dietary Se supplementation.

Formation of Si nanocrystals in multilayered nanoperiodic Al2O3/SiO x /Al2O3/SiO x /.../Si(100) structures: Synchrotron and photoluminescence data

The results of X-ray absorption near-edge structure spectroscopy data obtained with synchrotron radiation for multilayered nanoperiodic Al2O3/SiOx/Al2O3/SiOx/.../Si(100) structures annealed at temperatures of 500–1100°C are reported. The data show that, upon high-temperature annealing (∼1100°C), the structures are modified. The modification is attributed to the formation of Si nanocrystals in deep layers of the structures. At the same time, the structures exhibit size-dependent high-intensity photoluminescence in the photon-energy range 1.4–1.52 eV.

Investigation of Sulfur Crosslinking Interfacial of Natural Rubber (NR) Blending with Carboxyalted Styrene Butadiene Rubber (XSBR) Using X-Ray Absorption Spectroscopy

The sulfur crosslinking films from Natural Rubber (NR), Carboxylated Stryrene Butadiene Rubber (XSBR) latices, and their blends have been investigated using X-ray absorption near-edge structure spectroscopy (XANES). The film was prepared by casting the latex compound on glass surface and heating at 120oC in a hot air oven for 10 minutes. The sulfur crosslinking density were studied by the XANES. This was done to provide the local geometry and electronic environment of sulfur bonding in the rubber networks. We found that the reversion takes place before the onset of oxidative processes at the sulfur bridges. Parallel to the oxidative processes, the production of cyclic sulfanes takes places. This relationship depends on the rubber compositions.

X-ray absorption spectroscopy determination of the products of manganese borohydride decomposition upon heating

Manganese borohydride Mn(BH4)2 powder is heated in a hydrogen atmosphere in vacuum. The long-range order in the structure is monitored in situ by means of X-ray absorption spectroscopy and X-ray diffraction; short-range order, via Mg K-edge X-ray absorption near-edge structure spectroscopy. Above 120°C, the X-ray diffraction pattern disappears and an irreversible phase transition occurs, accompanied by sample amorphization and profuse hydrogen desorption. In the hydrogen atmosphere, the phase transition occurs at a temperature of ∼110°C. The standard scheme of borohydride decomposition suggests hydrogen desorption and the formation of metallic manganese and boron. However, a theoretical analysis of X-ray absorption spectra shows that the most likely products of Mn(BH4)2 decomposition are manganese borides.

Towards the Recovery of By-Product Metals from Mine Wastes: An X-Ray Absorption Spectroscopy Study on the Binding State of Rhenium in Debris from a Centennial Iberian Pyrite Belt Mine

Rhenium is a very scarce element, occurring in the Earth's crust mainly carried by molybdenite (MoS2). Due to a very low availability comparative to actual industrial demand, rhenium is nowadays one of the most expensive mineral commodities and an increased interest is focused on ex- ploring residues resulting from a long-term mining, particularly of sulphide ore deposits. It is therefore noteworthy to assign the presence of rhenium (in a concentration up to 3 ppm) in the waste materials from the old sulphur factory at the abandoned mine of Sao Domingos (Iberian Pyrite Belt, Southeast Portugal), exploited since the Roman occupation of Iberia. Aiming at a potential sustainable recovery of rhenium as a by-product, X-ray near-edge absorption spectroscopy (XANES) was applied to clarify the Re-binding and mode of occurrence by comparing Re L3-edge XANES spectra obtained from mine waste samples (previously fully characterized by X-ray laboratory techniques) with similar spectra collected from Re-rich molybdenites (Mo1-xRexS2) and from Re-O model compounds configuring various valences and coordination environments of rhenium ions. Obtained results are commented, ruling out a possible Re-S binding and rather conforming with the binding of rhenium to oxygen in the analysed mine waste materials.

Synchrotron study of the formation of nanoclusters in Al2O3/SiO x /Al2O3/SiO x /…/Si(100) multilayer nanostructures

Al2O3/SiO x /Al2O3/SiO x /…/Si(100) multilayer nanoperiodic structures (MNS) are studied by X-ray absorption near-edge structure spectroscopy (XANES). Experimental XANES spectroscopy spectra are obtained using synchrotron radiation. The formation of Si nanoclusters in the surface layers of the structures during their high-temperature annealing is observed. The structures featured intense size-dependent photoluminescence in the wavelength region near 800 nm. At the same time, it is shown that the formation of aluminum silicates is possible. The inversion effect of the intensity of the XANES spectra during the interaction of synchrotron radiation with MNSs is revealed.

Synthesis of Noble Metal-Doped Cu Nanoparticles by Ultrasonication

Cu nanoparticles doped with small amounts of noble metals were synthesized by ultrasonication. The noble metals selected were Pd, Pt, Ru, Rh and Ir. Mean particle size was most reduced for Cu nanoparticles doped with Pd, with Cu–Pd nanoparticles of approximately 50 nm in diameter being obtained. X-ray absorption, near-edge spectroscopy and extended X-ray absorption were used to conduct fine structure analysis, and these techniques confirmed that Cu–Pd nanoparticles possessed Cu–Pd bonds. High-angle annular dark-field scanning transmission electron microscopy and energy dispersive X-ray spectrometer mapping were used to show that Cu–Pd nanoparticles were dispersed as Pd clusters inside Cu nanoparticles. It was supposed that the surfaces of Cu–Pd nanoparticles were Cu-rich, and Pd clusters were dispersed inside these particles. It is proposed that heterogeneous nucleation of Cu onto Pd nuclei resulted when nucleation of Pd occurred.