Amorphous MoO2-wrapped Mo supported low-crystalline Co nanosheets for enhanced OH bond cleavage: synergistic effect of abundant active sites and robust interfaces.

“A spectroscopic picture paints 1000 words” mapping iron speciation in brain tissue with “full spectrum per pixel” X-ray absorption near-edge structure spectroscopy

ABSTRACTSulfur K-edge X-ray absorption near-edge structure spectroscopy and chemical sequential extraction was respectively used to study the speciation of sulfur in two sulfur-rich soils samples. Sulfur K-edge X-ray absorption near-edge structure spectroscopy analysis obtained a variety of spectra. Spectral fitting of the X-ray absorption near-edge structure spectra utilizing a large set of model compounds showed great differences between these two sulfur-rich soil samples. It was found that both of the soil samples had high sulfur content (8.40 and 11.57 g kg−1, respectively). Chemical extraction results suggested that sulfur mainly existed as organic in the ancient paddy soil (7.37 g kg−1) and more reduced sulfur was identified in it. X-ray absorption near-edge structure spectroscopy also got similar results. These organic forms of sulfur existed in organic matter across a range of oxidation states. There was high proportion of oxidized sulfur in the sulfuric acid plant that mainly existed as sulfate.

The microstructure and composition, including chemical speciation of sulphur (S), of two mollusc shells were investigated using a combination of scanning electron microscopy, X-ray absorption near-edge structure spectroscopy (XANES) and electron probe microanalysis (EPMA). The shell of Pinna is composed of monocrystalline, and Pinctada, of polycrystalline, calcite prisms separated by organic-rich walls. Sulphur speciation information from XANES spectra using a scanning X-ray microscope showed that the protein S content of the interprismatic walls is higher than the SO4 content, whereas the reverse is true for the intraprismatic structures. High-spatial-resolution XANES maps for the different S species across adjacent calcite prisms confirm their distinctive distributions in the molluscan shells and illustrate the presence of narrow, submicron transverse growth features. On a larger scale, a series of wider growth zones, incorporating the submicron zones, are aligned parallel to each other and cross-cut many calcite prisms. EPMA element maps for magnesium (Mg) and S demonstrate that these growth increments are compositionally zoned, comprising alternating layers of high mineral (Mg-rich) and high organic (S-rich) components. Additionally, these maps confirm that the organic interprismatic walls have lower Mg and higher S than the intraprismatic structures.

Investigating binary oil additive systems containing P and S using X-ray absorption near-edge structure spectroscopy

Iron local structure in tektites and impact glasses by extended X-ray absorption fine structure and high-resolution X-ray absorption near-edge structure spectroscopy

The role of interface charge transfer on Pt based catalysts for water splitting

The palladium (Pd)-catalyzed Suzuki reaction is widely applied in the pharmaceutical industry, where constructing highly active and low-cost Pd sites are impendent. Here, we report the fabrication ...

X-ray absorption near-edge structure (XANES) spectroscopy is a new method for the characterization of active pharmaceutical ingredients. XANES spectra show unique features depending on the electronic states of the X-ray absorbing elements and provide information about the chemical environment that affects the electronic states. In this study, six bisphosphonate hydrate crystals were used to investigate, for the first time, how the phosphorus K-edge XANES spectra are affected by the interatomic interactions and charged states of phosphonate moieties. Phosphorus K-edge XANES spectra showed several differences among the bisphosphonates. In particular, the chlorine atoms covalently bonded near the phosphonate and the number of electric charges of the phosphonate moieties seemed to have large effects on peak shape in XANES spectra. Unique shapes of the XANES spectra demonstrated that differences in interactions at the oxygen atoms of the phosphonate moieties could change the shapes of the XANES spectrum peaks to the extent that each material was distinguished based on the spectra. Since slight differences in interatomic interactions and charged states lead to variations in the spectra, XANES spectroscopy could be widely applied as the fingerprint method to evaluate active pharmaceutical ingredients.

X-ray absorption near-edge structure (XANES) spectroscopy of fullerenes: inner-shell excitonic effects in fullerenes and the XANES spectrum of a higher fullerene C 76

Structural evolution of fluorinated graphene upon molten-alkali treatment probed by X-ray absorption near-edge structure spectroscopy

X-ray absorption near-edge structure (XANES) spectroscopy is used to study the features of occupation sites of Mn dopants in the Ga1−xMnxN dilute magnetic semiconductors (DMSs) with zinc-blende structure. Theoretical XANES spectra are calculated for representative structure models of Mn atoms in the GaN lattice. It is shown that the substitutional Mn in GaN is characterized by a preedge peak at 2.0eV and a postedge multiple-scattering peak at 29.1eV. The peaks shift in position and drop in intensity dramatically for the interstitial MnI and MnGa–MnI dimer, and then disappear completely for Mn clusters. The experimental spectrum of Ga0.990Mn0.010N is almost reproduced by the calculated XANES spectrum of GaMnN with substitutional Mn.

Two-dimensional molybdenum boride coordinating with ruthenium nanoparticles to boost hydrogen generation from hydrolytic dehydrogenation of ammonia borane

Efficient Electronic Modulation of g-C ₃ N ₄ Photocatalyst by Implanting Atomically Dispersed Ag ₁ -N ₃ for Extremely High Hydrogen Evolution Rates

The local structure of Nb3Ge intermetallic superconductor has been studiedby Ge K-edge absorption spectroscopy. Extended x-ray absorption finestructure (EXAFS) experiments show two Ge–Nb distances. In additionto the crystallographic distance of ∼2.87 Å, there exists a second Ge–Nbdistance, shorter than the first by ∼0.2 Å, assigned to a phase with short-rangesymmetry related to local displacements in the Nb–Nb chains. The x-rayabsorption near-edge structure (XANES) spectrum has been simulated by fullmultiple-scattering calculations considering the local displacements determined bythe EXAFS analysis. The XANES spectrum has been well reproducedby considering a cluster of 99 atoms within a radius of about 7 Å fromthe central Ge atom and introducing determined local displacements.

Deuterium, solvent, and (15)N kinetic isotope effects have been used to probe the mechanisms by which flavoproteins oxidize carbon-oxygen and carbon-nitrogen bonds in amines, hydroxy acids, and alcohols. For the amine oxidases d-amino acid oxidase, N-methyltryptophan oxidase, and tryptophan monooxygenase, d-serine, sarcosine, and alanine are slow substrates for which CH bond cleavage is fully rate limiting. Inverse isotope effects for each of 0.992-0.996 are consistent with a common mechanism involving hydride transfer from the uncharged amine. Computational analyses of possible mechanisms support this conclusion. Deuterium and solvent isotope effects with wild-type and mutant variants of the lactate dehydrogenase flavocytochrome b(2) show that OH and CH bond cleavage are not concerted, but become so in the Y254F enzyme. This is consistent with a highly asynchronous reaction in which OH bond cleavage precedes hydride transfer. The results of Hammett analyses and solvent and deuterium isotope effects support a similar mechanism for alcohol oxidase.