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High entropy oxides (HEOs) have garnered much interest due to their available high degree of tunability. Here, we study the local structure of (MgNiCuCoZn)0.167(MnCr)0.083O, a composition based on the parent HEO (MgNiCuCoZn)0.2O. We synthesized a series of thin films via pulsed laser deposition at incremental oxygen partial pressures. X‐ray diffraction shows lattice parameters to decrease with increased pO2 pressures until the onset of phase separation. X‐ray absorption fine structure shows that specific atomic species in the composition dictate the global structure of the material as Cr, Co, and Mn shift to energetically favorable coordination with increasing pressure. Transmission electron microscopy analysis on a lower‐pressure sample exhibits a rock salt structure, but the higher‐pressure sample reveals reflections reminiscent of the spinel structure. In all, these findings give a more complete picture of how (MgNiCuCoZn)0.167(MnCr)0.083O forms with varying initial conditions and advances fundamental knowledge of cation behavior in high entropy oxides. [ABSTRACT FROM AUTHOR]

Conventional neutralization treatment for manganese (Mn)-bearing mine drainage provides a challenge of cost-efficiency, and new approaches should be explored for efficient removal of Mn. We focused on Mn neutralization sludge, a by-product of the Mn-bearing drainage treatment process, which was assumed to be useful as a water purification material. Mn and zinc (Zn) removal tests in simulated drainage were performed using Mn neutralization sludge, and the reaction mechanism was elucidated using geochemical modeling and X-ray absorption fine structure (XAFS) analysis. The results showed that the addition of sludge enabled to lower the Mn and Zn concentration below Japanese effluent standard (10 mg dm−3 for Mn; 2 mg dm−3 for Zn) within 1 h. Furthermore, heavy metal immobilization was achieved at neutral pH (7–8) with the sludge addition, while the conventional neutralization process without adding the sludge requires higher pH (>10) to lower Mn concentration. These removal behaviors were not explainable by considering only well-known phenomena: hydroxide precipitation, surface complexation reaction onto δ-MnO2, and autocatalytic Mn oxidation. Hence, we advanced the geochemical model for simulation, suggesting that a surface complexation reaction onto γ-MnOOH greatly contributed to the removal of Mn. Besides, Zn was calculated to be predominantly precipitated as ZnMn2O4. Solid residue analysis by XAFS measurement supported the result of above calculation, validating the reliability of the constructed geochemical model. Overall, we concluded that the advanced geochemical model would be useful in predicting the Mn and Zn behavior during mine drainage treatment with Mn neutralization sludge. [ABSTRACT FROM AUTHOR]

Structural transformation and magnetic change of pure and 1% La/Nd‐doped multiferroic BiFeO3 (BFO) nanoparticles are presented to study the influence of introducing rare‐earth elements at the A‐site in BFO. All samples are successfully produced by the conventional hydrothermal method. Scanning electron microscopy picture demonstrates that doping has an impact on the surface and size of particles, and the magnetic properties of BFO also are improved, even significant ferromagnetism is observed in the Nd‐doped sample. Though the room‐temperature X‐ray diffraction patterns reveal the rhombohedral R3c symmetry for all samples, further identified by the Bi L3‐edge and Fe K‐edge X‐ray absorption fine structure (XAFS) spectra, the nanoscale secondary orthorhombic phase is only detected in Bi0.99Nd0.01FeO3 when analyzing the doped elements according to the La and Nd L3‐edge XAFS spectra. The different magnetic behavior is speculated to be in connection with the orthorhombic symmetry around the Nd atom. [ABSTRACT FROM AUTHOR]

The influence of Yb3+ cations substitution for Pr3+ on the structure and catalytic activity of (Pr1−xYbx)2Zr2O7 powders synthesized via coprecipitation followed by calcination is studied using a combination of long- (s-XRD), medium- (Raman, FT-IR, and SEM-EDS) and short-range (XAFS) sensitive methods, as well as adsorption and catalytic techniques. It is established that chemical composition and calcination temperature are the two major factors that govern the phase composition, crystallographic, and local-structure parameters of these polycrystalline materials. The crystallographic and local-structure parameters of (Pr1−xYbx)2Zr2O7 samples prepared at 1400 °C/3 h demonstrate a tight correlation with their catalytic activity towards propane cracking. The progressive replacement of Pr3+ with Yb3+ cations gives rise to an increase in the catalytic activity. A mechanism of the catalytic cracking of propane is proposed, which considers the geometrical match between the metal–oxygen (Pr–O, Yb–O, and Zr–O) bond lengths within the active sites and the size of adsorbed propane molecule to be the decisive factor governing the reaction route. [ABSTRACT FROM AUTHOR]

The development of bifunctional catalysts for solar-driven hydrogen and oxygen evolution has been regarded as a challenging but interesting research topic. As promising multi-electron-transfer catalysts, reported polyoxometalate (POM)-based catalysts often contain only a single type of transition metal substitution for driving either hydrogen production or oxygen evolution. Herein, a viable two-step parental substitution approach has been developed to synthesize two structurally-new mixed-transition-metal-substituted polyoxometalates (mixed TMSPs), K6Na4[Mn2Ni2(H2O)2(PW9O34)2]·21H2O ({Mn2Ni2}) and K10[Mn2Co2-(H2O)2(PW9O34)2]·35H2O ({Mn2Co2}), using Na12[Mn2Na2(PW9O34)2]·36H2O ({Mn2Na2}) as the precursor. Characterization results confirmed the nearly quantitative substitution of Na+ with Ni2+ and Co2+ ions. X-ray absorption fine structure (XAFS) spectroscopy revealed that the Mn atoms are preferentially located in the internal positions of the central belt while Ni and Co atoms preferentially reside in the external, solvent-accessible positions. Benefiting from the second substitution of catalytically active transition metals, the resulting {Mn2Ni2} and {Mn2Co2} can be utilized as Janus catalysts towards H2 evolution and O2 evolution under visible light irradiation with greatly-enhanced activity compared to that of parental {Mn2Na2}. The introduction of mixed transition metals into POM structures not only enriches the POMs family, but also provides an effective strategy to control electronic structures and catalytic properties of POM-based catalysts at the atomic level. [ABSTRACT FROM AUTHOR]

Red slipped and painted wares (RSW and RPW) were manufactured to cook, serve, or store foods and liquids in the middle Yangtze River valley (MYRV) of China some 8500 and 7800 years ago, respectively. Their primary use narrowed down to serving and drinking in the Upper Qujialing (5300–4500 cal BP) and Shijiahe (4500–4200 cal BP) periods when initial states (bang guo) took shape and developed in the region. The increasing social complexity in MYRV correlated with the formation of community and neighborhood identity through rituals and socio-economic ties involving the widespread use of RSW and RPW. How the two wares were produced and used helps us understand the relationships among productive activities, identity, and social inequality in MYRV. This paper presents the first overview of RSW and RPW in the Neolithic MRYV. It introduces a multi-analytical study of the two wares—mostly dating to the Shijiahe period—unearthed from the site of Fenghuangzui in Xianyang City of Hubei Province, China. Optical microscopic examination revealed that the paint of RPW—50 μm thick on average—was applied using a brush while the slip of RSW is thinner and finer and possibly formed by self-slipping. Handheld X-ray fluorescence (hhXRF) and benchtop micro-XRF analyses ascribed the red paint or slip to iron and iron oxide. Raman and X-ray absorption fine structure analyses confirmed that iron was present in the paint or slip in the form of hematite with a poorly developed crystalline structure. Furthermore, thin-section petrography implied that different pastes were used to produce RPW and RSW, and hhXRF data indicated that the Upper Qujialing and Shijiahe pottery differ in the concentrations of five elements (Zr, Fe, Mn, Ti, and Ba), which might be helpful in future provenance studies of RSW and RPW. Our study discloses the complexity of the manufacture of RSW and RPW at Fenghuangzui. More details of RSW and RPW production and use from our ongoing project shall reveal the role of the two wares in the social dynamics of the Late Neolithic MYRV. [ABSTRACT FROM AUTHOR]

"Intrinsic" strategies for manipulating the local electronic structure and coordination environment of defect-regulated materials can optimize electrochemical storage performance. Nevertheless, the structure–activity relationship between defects and charge storage is ambiguous, which may be revealed by constructing highly ordered vacancy structures. Herein, we demonstrate molybdenum carbide MXene nanosheets with customized in-plane chemical ordered vacancies (Mo1.33CTx), by utilizing selective etching strategies. Synchrotron-based X-ray characterizations reveal that Mo atoms in Mo1.33CTx show increased average valence of +4.44 compared with the control Mo2CTx. Benefited from the introduced atomic active sites and high valence of Mo, Mo1.33CTx achieves an outstanding capacity of 603 mAh·g−1 at 0.2 A·g−1, superior to most original MXenes. Li+ storage kinetics analysis and density functional theory (DFT) simulations show that this optimized performance ensues from the more charge compensation during charge–discharge process, which enhances Faraday reaction compared with pure Mo2CTx. This vacancy manipulation provides an efficient way to realize MXene's potential as promising electrodes.

The influence of Yb3+ cations substitution for Pr3+ on the structure and catalytic activity of (Pr1−xYbx)2Zr2O7 powders synthesized via coprecipitation followed by calcination is studied using a combination of long- (s-XRD), medium- (Raman, FT-IR, and SEM-EDS) and short-range (XAFS) sensitive methods, as well as adsorption and catalytic techniques. It is established that chemical composition and calcination temperature are the two major factors that govern the phase composition, crystallographic, and local-structure parameters of these polycrystalline materials. The crystallographic and local-structure parameters of (Pr1−xYbx)2Zr2O7 samples prepared at 1400 °C/3 h demonstrate a tight correlation with their catalytic activity towards propane cracking. The progressive replacement of Pr3+ with Yb3+ cations gives rise to an increase in the catalytic activity. A mechanism of the catalytic cracking of propane is proposed, which considers the geometrical match between the metal–oxygen (Pr–O, Yb–O, and Zr–O) bond lengths within the active sites and the size of adsorbed propane molecule to be the decisive factor governing the reaction route.

The effect of synthesis conditions on the features of the long- and short-range order of Ln 2 (WO 4 ) 3 (Ln = Gd, Dy, Ho, Yb) powders synthesized via coprecipitation of salts has been studied by a complex of physico-chemical techniques including synchrotron X-ray powder diffraction, X-ray absorption spectroscopy, Raman and infrared spectroscopy, and simultaneous thermal analysis. It was found that crystallization of amorphous precursors begins at 600 °C/3 h and leads to the formation of the monoclinic structure with sp. gr. C12/c1(15) for Ln 2 (WO 4 ) 3 (Ln = Gd, Dy) and with sp. gr. P12 1 /a1(14) for Ln = Yb, whereas crystallization of Ho precursor requires even higher temperature. After annealing at 1000 °C, the P12 1 /a1(14) phase becomes the dominant phase component for all heavy lanthanoid types except for Ln = Gd. It was shown that the Ln (Ln = Dy, Ho, and Yb) tungstates with the P12 1 /a1(14) monoclinic structure correspond to trihydrates Ln 2 (WO 4 ) 3 ·3H 2 O formed due to a rapid spontaneous hydration under ambient conditions. It was concluded that the proneness to hydration is due to a specific structure of the P12 1 /a1(14) phase with large voids available to water molecules. Modifications in the local structure of Ln-O coordination shell accompanying the structure type change and hydration are monitored using EXAFS spectroscopy. [ABSTRACT FROM AUTHOR]

X-ray irradiation offers a promising avenue to expedite the green synthesis of nanoparticles with high efficiency, simplicity, and environmental friendliness. X-ray technologies, such as X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), and synchrotron X-ray technologies are utilized to explore the structural evolution of nanoparticles. We summarize numerous studies concerning X-ray-induced synthesis of gold nanoparticles. Further, we discuss the nuclear growing mechanism—radiolysis and conventional wet synthesis—explored via in situ XAFS analysis. Lastly, we propose the improvement of radiolytic synthesis and the application of in situ XAFS.

Fluorinated and nitrogen-doped graphdiyne (F/N-GDY) have been used in the active layer of perovskite solar cells (PSCs) for the first time. The introduction of heteroatoms turns out to be an effective method for boosted solar cells performance, which increases by 32.8% and 33.0%, better than the pristine or GDY doped PSCs. The enhanced performance can be attributed firstly to the superiority of F/N-GDY originated from the unique structure and optoelectronic properties of GDY. Then, both can further reduce surface defects and improve surface and bulk crystallinity than pristine GDY. What's more, efficiency increase caused by F-GDY is mainly attributed to the improvement of fill factor (FF), while the higher short-circuit current (JSC) plays more important role by N-GDY doping. Most importantly, the detailed mechanism brought about by doping of F-GDY or N-GDY is expounded by systematical characterizations, especially the synchrotron radiation technique. Doping of F-GDY causes PbII+x and forms new Pb-F bonds between F-GDY and Pb ions. Doping of N-GDY or GDY brings about PbII−x (N-GDY doping induces more deviation than that of GDY due to the participation of imine N), improving its electron density and conductivity. [ABSTRACT FROM AUTHOR]

Thin films formed on surfaces have a large impact on the properties of materials and devices. In this study, a method is proposed using X‐ray absorption spectroscopy to derive the film thickness of a thin film formed on a substrate using the spectral separation and logarithmic equation, which is a modified version of the formula used in electron spectroscopy. In the equation, the decay length in X‐ray absorption spectroscopy is longer than in electron spectroscopy due to a cascade of inelastic scattering of electrons generated in a solid. The modification factor, representing a multiple of the decay length, was experimentally determined using oxidized Si and Cu with films of thickness 19 nm and 39 nm, respectively. The validity of the proposed method was verified, and the results indicated that the method can be used in the analysis of various materials with thin films. [ABSTRACT FROM AUTHOR]

One of the most common types of experiment in X-ray absorption spectroscopy (XAS) measures the secondary inelastically scattered fluorescence photon. This widespread approach has a dominant systematic of self-absorption of the fluorescence photon. The large impact of self-absorption compromises accuracy, analysis and insight. Presented here is a detailed self-consistent method to correct for self-absorption and attenuation in fluorescence X-ray measurements. This method and the resulting software package can be applied to any fluorescence data, for XAS or any other experimental approach detecting fluorescence or inelastically scattered radiation, leading to a general solution applicable to a wide range of experimental investigations. The high intrinsic accuracy of the processed data allows these features to be well modelled and yields deeper potential insight.

The effect of synthesis conditions on the features of the long- and short-range order of Ln2(WO4)3 (Ln = Gd, Dy, Ho, Yb) powders synthesized via coprecipitation of salts has been studied by a complex of physico-chemical techniques including synchrotron X-ray powder diffraction, X-ray absorption spectroscopy, Raman and infrared spectroscopy, and simultaneous thermal analysis. It was found that crystallization of amorphous precursors begins at 600 °C/3 h and leads to the formation of the monoclinic structure with sp. gr. C12/c1(15) for Ln2(WO4)3 (Ln = Gd, Dy) and with sp. gr. P121/a1(14) for Ln = Yb, whereas crystallization of Ho precursor requires even higher temperature. After annealing at 1000 °C, the P121/a1(14) phase becomes the dominant phase component for all heavy lanthanoid types except for Ln = Gd. It was shown that the Ln (Ln = Dy, Ho, and Yb) tungstates with the P121/a1(14) monoclinic structure correspond to trihydrates Ln2(WO4)3·3H2O formed due to a rapid spontaneous hydration under ambient conditions. It was concluded that the proneness to hydration is due to a specific structure of the P121/a1(14) phase with large voids available to water molecules. Modifications in the local structure of Ln-O coordination shell accompanying the structure type change and hydration are monitored using EXAFS spectroscopy.

Several recent studies have reported a strong association between Sc and goethite (α-FeOOH) in synthetic analogs and natural samples. However, the mechanism of Sc immobilization by goethite and controlling factors remain unclear. This study investigated the adsorption behavior and molecular-scale immobilization mechanisms of Sc at water/goethite interfaces through a combination of batch adsorption and desorption experiments, X-ray absorption fine structure (XAFS) analyses, and density functional theory (DFT) calculations. Results indicate that Sc is preferentially adsorbed on goethite with the formation of bidentate-binuclear inner-sphere complexes at the corner-sharing sites. Bulk Sc K-edge XAFS analyses suggest that Sc is incorporated into the goethite structure by substituting for Fe(III) within the crystal in synthetic Sc-substituted goethite, which is further confirmed in natural goethite particles in the laterite by using micro-focused XAFS (μ-XAFS). Furthermore, we demonstrate that the adsorbed Sc on the goethite surface can be structurally incorporated into the goethite lattice in the presence of aqueous Fe(II) possibly through goethite recrystallization induced by aqueous Fe(II). This process may affect the (re)partitioning of Sc between the goethite surface and the mineral bulk, which could be used to rationally explain disparate Sc speciation in laterites from different regions. Our study elucidates the molecular-scale mechanisms underlying Sc adsorption on and structural incorporation into goethite, providing critical insights into the understanding of geochemical behavior and environmental fates of Sc. [ABSTRACT FROM AUTHOR]

The kinetics of phase transformation in the FeC system during cooling are of great importance for controlling its microstructure and mechanical properties. However, real-time observation of the phase transformation has been a challenging task because of experimental difficulties. Here, we developed an analytical technique for time-resolved observation of the phase transformation of an FeC system during cooling via X-ray absorption spectroscopy with a time resolution of 200 µs. The technique was applied to model specimens: Fe, Fe0.044C, and Fe1.24C. The incubation time before phase transformation and the multiple steps of phase transformation from £-Fe to ¡-Fe (+ Fe3C) could be clearly observed by the proposed technique, and the behaviors were significantly different among the specimens. Through the developed technique, change in atomic structures at a short-range scale was detected, which is complementary to X-ray diffraction that detects atomic structures only in long-range order. The developed technique can detect structure changes at early stage of phase transformations, where structures changes often begin at a short-range scale, and provide inevitable information on the kinetics. [ABSTRACT FROM AUTHOR]

Bimetallic metal-organic frameworks (MOFs) are promising nanomaterials whose reactivity towards biomolecules remains challenging due to issues related to synthesis, stability, control over metal oxidation state, phase purity, and atomic level characterization. Here, these shortcomings are rationally addressed through development of a synthesis of mixed metal Zr/Ce-MOFs in aqueous environment, overcoming significant hurdles in the development of MOF nanozymes, sufficiently stable on biologically relevant conditions. Specifically, a green and safe synthesis of Zr/Ce-MOF-808 is reported in water/acetic acid mixture which affords remarkably water-stable materials with reliable nanozymatic reactivity, including MOFs with a high Ce content previously reported to be unstable in water. The new materials outperform analogous bimetallic MOF nanozymes, showcasing that rational synthesis modifications could impart outstanding improvements. Further, atomic-level characterization by X-ray Absorption Fine Structure (XAFS) and X-ray Diffraction (XRD) confirmed superior nanozymes arise from differences in the synthetic method, which results in aqueous stable materials, and Ce incorporation, which perturbs the ligand exchange dynamics of the material, and could ultimately be used to fine tune the intrinsic MOF reactivity. Similar rational strategies which leverage metals in a synergistic manner should enable other water-stable bimetallic MOF nanozymes able to surpass existing ones, laying the path for varied biotechnological applications., (© 2023 Wiley‐VCH GmbH.)

Abstract The effects of ion irradiation on the atomic local structure of GH3535, a nickel based alloy and candidate of pressure vessel material for molten salt reactor, were investigated by X-ray absorption fine structure (XAFS). We investigated the local structure of the three major solid solution atoms: Mo, Cr, and Fe under the irradiation of two species of ions: He+ and Ni13+. The changes to the coordination number of these atoms after irradiation were determined from XAFS data. The results reveal that ion irradiation causes selective damage to the elements in alloy. No matter for He+ and Ni13+, Cr is the most vulnerable atom in the alloy to the irradiation with the most decrease in its local coordination number. Mo, on the contrary, changes little under either type of ion irradiation. The irradiation damage to Fe lies in between. The degree of ion damage, however, is closely related to the ion species and energy. XRD results show slight increase of lattice constant in the alloy after irradiation with Ni13+, while the lattice remains unchanged after irradiation with He+. The MD simulation in pure nickel system suggests the lattice expanse effect by the competition between interstitials and vacancies. [ABSTRACT FROM AUTHOR]

Abstract The oxidation of antimony (III) in soils was studied using X-ray absorption fine structure (XAFS) spectra. An andosol soil sample and artificial soil samples (SiO 2 blended with iron (III) hydroxide and manganese (IV) oxide) were used herein. After adding antimony (III) oxide to all soil samples, the oxidation process was observed by recording the XAFS spectra of Sb K-edge, Fe K-edge, and Mn K-edge. The results indicated that manganese (IV) oxide played an important role in the oxidation of Sb(III); however iron (III) hydroxide was not directly related to the reaction. During a 2-hr continuous Sb K-edge X-ray absorption near edge structure (XANES) measurement with an interval of 1 min of one of the artificial soil samples (SiO 2 + MnO 2 + Sb 2 O 3), a pseudo-first-order reaction was determined with an average estimated rate of 0.52 ± 0.04 hr− 1. Compared to the lower oxidation rate of andosol, it is suggested that because of the low concentration of Mn(IV) in natural soils, the oxidation process of Sb(III) might be relatively slow and require more time to convert Sb(III) to Sb(V). Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Two-dimensional spectral images, as opposed to one-dimensional spectra, are crucial for both recognizing the presence and verifying the removal of photoemission features in Auger-yield NEXAFS. We present a procedure for removing such photoemission features, which relies on describing the measured Auger-yield NEXAFS image as three simple, one-dimensional spectra: NEXAFS, Auger, and XPS. This allows for a very successful and fast removal of even extreme photoemission features, as illustrated by four examples. The procedure requires no additional reference measurements other than photon flux, and provides a significant amount of additional information, such as NEXAFS, Auger and XPS spectra and images, which can be used to verify the validity of the underlying assumptions and success of the cleanup process. [ABSTRACT FROM AUTHOR]

The electrical conductivity of porous graphene is increased more than 3000 times via introducing Cu NPs. The fine structure of Cu-graphene interface is characterized by X-ray Absorption Fine Structure (XAFS) spectroscopy, based on which, DFT calculations are further adopted to reveal the influence of interface structure on electrical conductivity. The results reveal that large amounts of electrons can be transferred from Cu nanoparticles to graphene through the stable Cu C bonds. [Display omitted] • Highly conductive graphene@Cu composite film is developed by laser irradiation. • Free electrons are transferred from Cu to graphene, leading to high carrier density. • The conductivity of composite film reaches 0.37 × 107 S/m. • The fine structure of Cu-graphene interface is characterized by XAFS. • DFT calculations reveal the influence of interface structure on electron transfer. Electrical conductivity of graphene is one of the most important factors to dominate its applications, which is much lower than conventional good conductors including cooper in spite of its excellent electron mobility, limited by its low carrier density. In this work, a general way to improve electrical conductivity of graphene is proposed via introducing Cu NPs, which are rich in free electrons, into the well-crystalized laser-induced graphene (LIG). The LIG/Cu composite films, with an average diameter of 10 nm of Cu NPs evenly dispersed, were prepared in a laser induction process. It is worth mentioning that the electrical conductivity of porous graphene composited with Cu NPs is increased up to 0.37 × 107 S m−1, which is 3000 times that of pure LIG. To make clear mechanism of this notable phenomenon, the fine structure of Cu-graphene interface is characterized by X-ray Absorption Fine Structure (XAFS) spectroscopy, based on which, Density Function Theory (DFT) calculations are further adopted to reveal the influence of interface structure on electrical conductivity. It is revealed that Cu NPs with surface oxidation state (Cu2+) are most conducive to forming stable bonds with graphene, which will facilitate the electrons transfer from Cu to graphene. As a result, high carrier density and mobility are simultaneously realized in the graphene film, which finally leads to significant electrical conductivity enhancement. The results are of great significance in manipulating electrical conductivity of graphene with respect to various applications. [ABSTRACT FROM AUTHOR]

With the advent of ambient pressure X-ray excited electron spectroscopy, near-edge X-ray absorption fine structure spectroscopy is widely used to investigate the hydrogen-bonding environment in aqueous solutions, ice, and adsorbed water. When Auger-Meitner electrons are detected, the method becomes inherently surface-sensitive because of the limited escape depth of electrons. In such X-ray absorption experiments with aqueous samples, gas-phase water is inevitably present. It impacts the acquired spectra in two ways: (1) Absorption along the X-ray path upstream of the sample reduces the photon flux reaching the condensed phase. (2) Spectra originating from gas-phase water in front of the analyzer contribute to the recorded spectra. Here, we develop and discuss a procedure to disentangle the gas-phase and condensed-phase contribution in the acquired spectra. A novel approach to quantify and remove the gas-phase contribution allows receiving condensed-phase near-edge X-ray absorption fine structure spectra at high water vapor pressure free of gas-phase artifacts. • X-ray absorption data probing ice are impacted by the elevated partial pressure of water present. • First, photon flux reaching the sample is reduced by X-ray absorption of gas-phase water. • Second, X-ray spectra show the contribution of gas-phase water. • Both artifacts can be removed with high precision. [ABSTRACT FROM AUTHOR]

To meet the demand for smart windows, element doping is widely used as a powerful tool to customize the thermochromic properties of vanadium dioxide (VO 2). Here, Mo-doped and F/Mo co-doped VO 2 nanoparticles (NPs) are synthesized by the supercritical hydrothermal method. Doped VO 2 films show excellent thermochromic properties including the reduced phase transition temperature (T c = 47.4 °C), enhanced luminous transmittance (T lum = 59.7%), and high solar energy modulation (ΔT sol = 13.7%). Both X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS) are utilized to study the local structure and chemical valence of the vanadium and molybdenum in the VO 2 lattice. Combined Mott's with Peierls's models, the phase transition behavior of the doped VO 2 is revealed deeply, i.e., depending on the octahedral symmetry and charge transfer. Additional electron injection seems to play a more important role than structural distortion in decreasing T c , and F atoms exhibit a higher modulation ability of T c. In addition, reduced reflectance by doping is responsible for the significantly improved T lum , while ΔT sol is found to be more sensitive to the film structure. This work uncovers the mechanism behind the phase transition of Mo-doped and F/Mo co-doped VO 2 NPs, which is expected to inspire the optimization strategy of element-doped VO 2 films served as smart windows. • Mo-doped and F/Mo co-doped VO 2 nanoparticles (NPs) are hydrothermally synthesized. • Doped VO 2 films possess excellent thermochromic properties. • Phase transition behavior is depended on octahedral symmetry and charge transfer. • Increased T lum is attributed to the reduction of film reflectance. [ABSTRACT FROM AUTHOR]

The influence exerted by specific synthesis protocol conditions on the crystal, local atomic and electronic structures of various types of Ce chromates/chromites prepared by the coprecipitation is studied using synchrotron X-ray diffraction, X-ray absorption fine structure (XAFS), Raman and Fourier transform infrared (FT-IR) spectroscopies, and simultaneous thermal analysis. Cerium chromate heptahydrate [Ce 2 + 3 (Cr + 6 O 4) 3 (H 2 O) 5 ] ⋅ 2H 2 O with the monoclinic structure (sp. gr. P 2 1 / c) has been synthesized and characterized structurally for the first time. It has been established that calcination of all types of precursors in air at a temperature ≥ 450 ° C leads to the formation of a mixture of CeO 2 and Cr 2 O 3 phases. The calcination in vacuum at 1200 ° C affords CeCrO 3 (with the orthorhombic structure, sp. gr. Pnma (62)), which upon repeated heating to above 650–700 ° C in air tends to decompose into CeO 2 and Cr 2 O 3 phases. Long-range XRD data correlate well with the results of techniques sensitive to the local structure parameters, such as XAFS, Raman and FT-IR. XANES spectra measured at the Cr K- and Ce L 3 - edges strongly imply that the synthesis procedures are accompanied by concerted redox transformations Cr 6 + → Cr3＋ and Ce 3 + ⟷ Ce 4 +. [Display omitted] • The crystal, local and electronic structures of Ce chromates/chromites are studied. • A combination of s-XRD, XANES, Raman and FT-IR, STA techniques is applied. • Ce 2 + 3 (Cr + 6 O 4) 3 ⋅ 7H 2 O (monoclinic, P 2 1 / c) has been synthesized for the first time. • Vacuum calcination at 1200 °C affords CeCrO 3 (orthorhombic, P nma). • The synthesis is accompanied by concerted redox reactions Cr6+ → Cr3+ and Ce 3 + ⟷ Ce 4 +. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel measurement method is proposed and verified using copper. • The spectrum is unaffected by the self-absorption effect and is not distorted. • The spectral oscillation is obtained over a wide energy range. • The analysis depth is comparable to that of the common l -edge measurement. A novel measurement method that addresses the self-absorption effect, which is a significant disadvantage in X-ray absorption spectroscopy in fluorescence yield mode for surface analysis, is proposed. The validity and features were experimentally verified using copper. This method uses the l -line fluorescence that cascades from the KLL Auger process caused by K-shell absorption. The obtained spectrum is unaffected by the self-absorption effect and is not distorted. The confirmed features are that the spectral oscillation with a wide energy range is obtained, and the analysis depth is comparable to that of the l -edge measurement. In addition, the proposed method theoretically applies to samples with uneven surfaces, that is, various actual materials. [ABSTRACT FROM AUTHOR]

Several recent studies have reported a strong association between Pt and iron-bearing minerals in marine ferromanganese oxides. However, due to the low Pt abundance (hundreds of ppb) in these ferromanganese oxides, the mechanism and controlling factors of Pt enrichment in ferromanganese oxides are not clear. Feroxyhyte is an important constituent of marine ferromanganese oxides and is thought to play an important role in Pt enrichment. Here, we used feroxyhyte as the representative of Fe minerals in the marine ferromanganese oxides to study the adsorption behavior and molecular scale adsorption mechanisms of Pt at the water-feroxyhyte interface. The study employed a combination of Pt adsorption/desorption experiments with the participation of various ionic salts, and X-ray absorption fine structure (XAFS) analyses. The adsorption/desorption experimental results showed that the presence of phosphate, ammonium and low pH environment would inhibit Pt enrichment on feroxyhyte. Pt L III -edge XAFS analysis shows that Pt is oxidized on the feroxyhyte surface, transforming Pt (II) to Pt (IV) (OH) 6 2−. According to the experiment results, this study proposed a hypothesis of the mechanism of Pt enrichment by feroxyhyte. Pt (II) Cl 4 2−is considered to be the main form of Pt in seawater. [ PtCl n (OH) 4− n ]2− produced by the hydrolysis of [ PtCl 4 ]2− is adsorbed to the feroxyhyte surface through dehydration condensation, and then oxidized to Pt (IV) (OH) 6 2−. Our results clarify the molecular-scale mechanism of Pt adsorption and fixation on feroxyhyte, and provide insights on the geochemical behavior of Pt. [Display omitted] • Feroxyhyte is an important host of Pt in deep-sea ferromanganese crusts. • The chemical state of Pt on the surface of feroxyhyte was studied by XAFS • The enrichment process of Pt by feroxyhyte is studied by various adsorption/desorption experiments. • A complete mechanism for the enrichment of dissolved Pt in seawater by feroxyhyte is proposed. [ABSTRACT FROM AUTHOR]

It has been said that the end of Moore’s law will be reached in 10 to 20 years. Three dimensional integration technology is expected to be a possible solution in the post-Moore era. The bonding of the metal electrode and insulator hybrid interfaces is one of key technique in three dimensional technology. The hybrid bonding technique is highly challenging issue. Surface activated bonding (SAB), which is a bonding method carried out at room or low temperatures, is expected to solve various problems which caused by heating process. Metal materials such as Cu or Al are easy to directly bond by SAB method at room temperature, but insulator materials such as SiO2 or SiN is very difficult. First, we investigated the bonding interface of Cu/Cu by transmission electron microscopy (TEM) observations. No intermediate layers or voids were visible at the bonding interface. The bonded specimen fractured not at the interface of the bonded Cu/Cu, but at the interface between the thermal oxide layer and Ti film by tensile test. The current-voltage characteristic of the bonding interface was linear. Secondly, we proposed a new bonding technique for bonding of SiO2/SiO2 using Si ultra-thin films by applying the SAB method. The amorphous Si layer with the thickness of about 7 nm was observed at the bonding interface by TEM observation. The bonded specimen fractured at the glue interface and not the bonded interface by tensile test. The bonding strength is estimated to be higher than the adhesive glue for tensile test. We have shown that the SAB method at room temperature is a bonding technique that can fulfill requirements for hybrid bonding, which serves as both mechanical bonding and electrical connection, in 3D integration technology.

A unique X-ray absorption spectroscopy (XAS) method is proposed for depth profiling of chemical states in material surfaces. Partial electron yield mode detecting energy-loss Auger electrons, called the inelastic electron yield (IEY) mode, enables a variation in the probe depth. As an example, Si K-edge XAS spectra for a well-defined multilayer sample (Si 3 N 4 /SiO 2 /Si) have been investigated using this method at various kinetic energies. We found that the peaks assigned to the layers from the top layer to the substrate appeared in the spectra in the order of increasing energy loss relative to the Auger electrons. Thus, the probe depth can be changed by the selection of the kinetic energy of the energy loss electrons in IEY-XAS. [ABSTRACT FROM AUTHOR]

The effect of solvent on the polymerization of 3 ‐ hexylthiophene with FeCl3 was evaluated using time ‐ dependent partial fluorescence yield X ‐ ray absorption fine structure measurements. FeCl3 acts as a catalyst when the reaction is performed in CHCl3, whereas it behaves as an oxidant in hexane. [ABSTRACT FROM AUTHOR]

A positively-charged pillared bentonite (Al-bent) was used as the carrier of nanoscale zerovalent iron (NZVI) particles for accelerating the reductive removal of anionic Se(VI) from water by NZVI. A synergetic effect on Se(VI) removal by this NZVI/Al-bent composite was observed, with removal efficiency (95.7%) much higher than the sum (72.0%) of NZVI reduction (62.1%) and Al-bent adsorption (9.86%). The multiple roles of Al-bent in the reaction system of Se(VI) with NZVI were comprehensively investigated using XAFS techniques, XRD analysis, kinetic studies and pH monitoring. The results indicate that the positively-charged Al-bent as a good adsorbent to anionic Se(VI) accelerated the reductive transformation of Se(VI) into less soluble Se(-II). Al-bent also acted as a pH buffering agent, and contributed to the enhanced stability and reusability of NZVI. In addition, Al-bent could transfer the insoluble reduction products away from the iron surface according to EXAFS studies. Particularly, Al-bent could activate Fe(II) ions generated in the reaction system through an appropriate bonding at pH 8.0, and provide NZVI with an extra reduction capacity. The results indicate the significance of correct matching of bentonite support to target contaminant for developing novel remediation technique based on this natural mineral. [ABSTRACT FROM AUTHOR]

The influence exerted by the specific type of the lanthanide cation and calcination temperature on the crystal and local structures of Ln 2 (WO 4) 3 tungstates (Ln = La–Dy) prepared by a coprecipitation is studied using synchrotron X-ray diffraction, X-ray absorption fine structure (XAFS) spectroscopy, Fourier transform infrared (FT-IR) and Raman spectroscopies, photoluminescence, simultaneous thermal analysis, and inductively coupled plasma atomic emission spectroscopy. The combination of these experimental techniques enabled a structural insight into Ln tungstates at multiple characteristic scales, i.e. short-range of metal atom coordination (XAFS), medium-range of the network of chemical bonds (FT-IR and Raman spectroscopies), and long-range or 3D periodicity within crystallites (XRD). It is found that the onset of amorphous precursor crystallization is observed at 575–600 ∘C/3 h and leads to the formation of Ln 2 (WO 4) 3 nanocrystalline powders with a monoclinic (sp. gr. C 12/ c 1 (15)) structure. An increase in the calcination temperature leads to the growth of crystallite size and a decrease in microstrains. In the case of Dy 2 (WO 4) 3 an additional orthorhombic phase emerges (sp. gr. Pbcn (60)) at 1000 ∘C. It is shown that the local structure of all well-crystallized compounds being studied contains lanthanide ions in the form of Ln 3+ and tungsten ions in the form of WO 4 2 − tetrahedra. The local structure in the monoclinic phase can be represented as a superposition of two non-equivalent tungstate tetrahedra: W(1)O 4 (C 2 site symmetry) and W(2)O 4 (C 1 site symmetry). The Ln O 8 polyhedra are strongly irregular, and the Ln 3+ cations occupy low-symmetry sites. [Display omitted] • Formation and evolution of the crystal and local structure in Ln 2 (WO 4) 3 were studied. • A combination of s-XRD, XAFS, Raman and IR, PL, STA, ICP-AES methods were used. • The ordering of both cationic and anionic sublattices in the Ln 2 (WO 4) 3 was observed. • The local structure of all Ln tungstates contains Ln3+ cations and WO 4 2- tetrahedra. • The Ln3 + cations are located in sites with low point group symmetry (distorted LnO 8). [ABSTRACT FROM AUTHOR]

Highlights: [•] The electronic structural of Co–CeO2 nanoparticles is investigated using XAFS. [•] Ce , Ce L 3 and O K edge NEXAFS reveal that the Ce-ions are in +4 valence state. [•] The NEXAFS spectrum performed at Co L3,2-edge confirms Co-ion in 2+ state. [•] The EXAFS analysis also show that Co ions are occupying Ce position in doped CeO2. [•] The distances between Ce–O and Ce–Ce/Co in all shells decreases with Co doping. [ABSTRACT FROM AUTHOR]

Abstract: The Carnian pluvial event (CPE) is considered as the drastic environmental change that occurred in the western Tethys during the Carnian (Late Triassic). Although some studies have suggested that the CPE was a global event, no studies have referred to pelagic environment related to the CPE. To reveal the pelagic environment during the Carnian, X-ray absorption fine structure (XAFS) analysis was used to determine the iron (Fe) species in chert samples collected from the Ladinian–Carnian strata in the Tamba–Mino–Ashio Belt, Japan. The X-ray absorption near-edge structure (XANES) analysis shows that all the red cherts contain hematite with a combination of clay minerals, such as illite, chlorite, and smectite. The existence of these minerals is identified using extended XAFS (EXAFS). The XANES analysis of the green and the white cherts does not show any hematite signatures, while the EXAFS analysis indicated increasing amounts of chlorite. The stratigraphic change in the Fe-bearing compositions observed in this study can be divided into three stages: (i) a stage where a relatively stable mineral composition (chlorite+illite+hematite) is observed in cherts deposited during the early Carnian (Julian), (ii) the abrupt change in mineral composition (lack of chlorite and appearance of smectite) observed in the middle area in the studied section and corresponding to the middle part of Carnian (late Julian–early Tuvalian), and (iii) the recovery of the previous stable mineral composition during the late Carnian (Tuvalian). These variations in the mineralogical composition of pelagic cherts can be interpreted to mean that the continental climate conditions changed during the Carnian, and different clay fractions were delivered to the pelagic region. These data, combined with the results of previous studies performed around the continental realm, can be interpreted as follows: (i) there was a relatively stable dry climate before the CPE, (ii) there were increasing amounts of precipitation owing to the CPE, and (iii) the climate returned to dry conditions similar to those prior to the CPE. [Copyright &y& Elsevier]

Abstract: Deactivation mechanisms of copper chromite (CuCr2O4⋅CuO) catalyst for vapor-phase selective hydrogenation for furfuryl alcohol have been investigated using ex situ and in situ X-ray absorption fine structure (XAFS), X-ray photon spectroscopy (XPS), and Auger Electron Spectroscopy (AES). At 200°C, the catalyst steadily deactivated. One of the dominant origins of catalyst deactivation is poisoning due to strong adsorption of polymeric species formed from the reactant and/or products. Metallic Cu is identified as the active site, while loss of active Cu(I) sites due to hydrogenation is not a deactivation cause, as opposed to previous literature reported. The copper chromite catalyst showed low activity at 300°C process temperature. Under this condition, the Cu particle size does not change, but Cr/Cu ratio increases by 50%, suggesting that Cr coverage of Cu sites becomes an additional cause of catalyst deactivation at this temperature, along with the poisoning deactivation mechanism at 200°C. [Copyright &y& Elsevier]

Abstract: Metal binding to microbial extracellular polymeric substances (EPS) greatly influences the distribution of heavy metals in microbial aggregates, soil and aquatic systems in nature. In this work, the thermodynamic characteristics of the binding between aqueous metals (with copper ion as an example) and EPS of activated sludge were investigated. Isothermal titration calorimetry was employed to estimate the thermodynamic parameters for the binding of Cu2+ onto EPS, while three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy with parallel factor analysis was used for quantifying the complexation of Cu2+ with the EPS. The binding mechanisms were further explored by X-ray absorption fine structure (XAFS) and Fourier transform infrared (FTIR) spectroscopy analysis. The results show that the proteins and humic substances in EPS were both strong ligands for Cu2+. The binding capacity N, binding constant K, binding enthalpy ΔH were calculated as 5.74 × 10−2 mmol/g, 2.18 × 105 L/mol, and −11.30 kJ/mol, respectively, implying that such a binding process was exothermic and thermodynamically favorable. The binding process was found to be driven mainly by the entropy change of the reaction. A further investigation shows that Cu2+ bound with the oxygen atom in the carboxyl groups in the EPS molecules of activated sludge. This study facilitates a better understanding about the roles of EPS in protecting microbes against heavy metals. [Copyright &y& Elsevier]

Local atomic and electronic structure with magnetic properties, especially Griffiths phase, of polycrystalline samples LaCaMnCuO ( x=0, 0.03, 0.06, 0.1) have been studied. The X-ray absorption spectra (XAS) of Cu 2 p core level prove that the valence state of Cu ions exhibits trivalent state when doping content x≤0.06 and divalent Cu ions begin to show for x=0.1. For the valence states of Mn ions, the X-ray photoelectron spectroscopy data show that they are in mixed states of Mn and Mn, and a shift to lower binding energy is observed, which is not attributed to the variation of valence states of Mn ions but the change of crystallographic surroundings, because there is no obvious change detected by X-ray absorption fine structure spectroscopy (XAFS). The Debye-Waller factor ( σ) of x=0.1 sample is only slightly larger compared to x=0, which may be the origin of enhancement of Griffiths phase observed in the inverse-susceptibility as a function of temperature ( H/ M∼ T). The H/ M∼ T curves of Cu doped samples indicate coexistence of FM, AFM and PM phase above Curie temperature T, which may be related to the strong hybridization of O 2 p and Mn 3 d reflected by O 1 s XAS spectra. [ABSTRACT FROM AUTHOR]

The Griffiths phase has been investigated in terms of oxygen vacancy in polycrystalline samples LaCaMnO (LCMO-1) and LaCaMnO (LCMO-2). The latter of the two samples is prepared by annealing the former (with existence of Griffiths phase) in N atmosphere. Experimental results demonstrate that for the latter sample Griffith's phase disappears (according to its obeying Curie-Weiss law in the temperature dependence of inverse susceptibility) due to redistribution of magnetic disorder between Mn and Mn ions induced by the increment of crystal lattice structure parameters. XRD patterns of the two samples show an increase of crystal lattice structure parameters. X-ray absorption fine structure data manifest that the degree of structural disorder in LCMO-2 sample is higher than that of LCMO-1, indicating that local structural disorder in this system is not the key role to affect the existence of Griffiths phase, while magnetic distribution/disorder is an important character. [ABSTRACT FROM AUTHOR]

Abstract: NZVI was supported on a pillared bentonite (Al-bent) to enhance the reactivity of NZVI and prevent its aggregation. The performance and mechanisms of the combined NZVI/Al-bent on removing hexavalent chromium (Cr(VI)) was investigated by batch and XAFS experiments. The batch investigations indicated that Cr(VI) could be almost completely removed by NZVI/Al-bent after 120min. The efficiency was not only much higher than that by NZVI (63.0%), but also superior to the sum of NZVI reduction and Al-bent adsorption (12.4%). Besides, NZVI/Al-bent exhibited good stability and reusability, and Al-bent could reduce the amount of iron ions released into the solution. XANES results provided evidence that NZVI/Al-bent could reduce Cr(VI) entirely into Cr(III), while NZVI reduced Cr(VI) partly into Cr(III) with a trace of Cr(VI) adsorbed on the corrosion products. The structure of Cr(VI)-treated NZVI/Al-bent determined with EXAFS revealed the formation of Cr–Al/Si bond, suggesting that some insoluble Cr(III) species might be transferred to the surface of Al-bent, therefore the precipitates on iron surface could be greatly reduced. The results demonstrated that Al-bent plays a significant role in enhanced reactivity and stability of NZVI, and may shed new light on design and fabrication of supported NZVI for environmental remediation. [Copyright &y& Elsevier]

In this paper, the existence of Griffiths phase and variation of ferromagnetism have been studied for LaCaMnO nanoparticles annealed at different temperatures. It is detected by x-ray diffraction patterns that the increasing of annealing temperature induces the increment of grain size. The magnetization as a function of temperature demonstrates that magnitude of magnetization at low temperature is decreased as the annealing temperature increases, which is explained by the core-shell model. The temperature dependence of inverse susceptibility of those samples manifests that the Griffiths phase occurs for the samples annealed at temperatures 900 °C and 1150 °C and it disappears for the sample annealed at 1350 °C. The reduction of Griffiths phase with increasing of annealing temperature indicates the suppression of quenched disorder after annealing, which may be related to the lower degree of disorder, redistribution of magnetic ions, and weaker hybridization of O 2p states with its near-neighbor atoms. As to the disappearance of Griffiths phase, competition between paramagnetic, ferromagnetic, and antiferromagnetic phases plays a very important role. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen sulfide is highly toxic to benthic organisms and may cause blue tide with depletion of dissolved oxygen in water column due to its oxidation. The purpose of this study is to reveal the combined adsorption and oxidation mechanisms of hydrogen sulfide on granulated coal ash that is a byproduct from coal electric power stations to apply the material as an adsorbent for hydrogen sulfide in natural fields. Sulfur species were identified in both liquid and solid phases to discuss removal mechanisms of the hydrogen sulfide with the granulated coal ash. Batch experiments revealed that hydrogen sulfide decreased significantly by addition of the granulated coal ash and simultaneously the sulfate ion concentration increased. X-ray absorption fine structure analyses showed hydrogen sulfide was adsorbed onto the granulated coal ash and successively oxidized by manganese oxide (III) contained in the material. The oxidation reaction of hydrogen sulfide was coupling with reduction of manganese oxide. On the other hand, iron containing in the granulated coal ash was not involved in hydrogen sulfide oxidation, because the major species of iron in the granulated coal ash was ferrous iron that is not easily reduced by hydrogen sulfide. [Copyright &y& Elsevier]

Abstract: Physical or chemical properties of hydrated ions confined in solid nanospaces are not substantially understood, although they are indispensable for the development of new science and technology. We study the local structure around a Cu2+ of copper acetate restricted in slit-shaped micropore of two kinds of activated carbon fibers (ACFs) by X-ray absorption fine structure (XAFS) technique. The results indicate that the highly dispersed copper acetate on the surface of ACFs can be partially dissolved after the adsorption of water. Also, when we adsorb water to copper acetate-deposited ACFs, the Cu–Cu distance of the dinuclear species of copper acetate becomes longer with the ordering of the Cu–Cu bond because of the reduction of the number of the bridging carboxylate inside the micropore. In addition, the results of EXAFS spectra suggest that water molecules can play an important role for the ordering of the specific dinuclear complex of copper acetate formed in the micropore even though the number of bridging carboxylate which can stabilize the dinuclear structure is decreased by the adsorption of water. [Copyright &y& Elsevier]