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Sample records for near-edge structure xanes

  1. Microanalysis of iron oxidation state in iron oxides using X Ray Absorption Near Edge Structure (XANES)

    NASA Technical Reports Server (NTRS)

    Sutton, S. R.; Delaney, J.; Bajt, S.; Rivers, M. L.; Smith, J. V.

    1993-01-01

    An exploratory application of x ray absorption near edge structure (XANES) analysis using the synchrotron x ray microprobe was undertaken to obtain Fe XANES spectra on individual sub-millimeter grains in conventional polished sections. The experiments concentrated on determinations of Fe valence in a suite of iron oxide minerals for which independent estimates of the iron speciation could be made by electron microprobe analysis and x ray diffraction.

  2. Structural changes of nucleic acid base in aqueous solution as observed in X-ray absorption near edge structure (XANES)

    NASA Astrophysics Data System (ADS)

    Shimada, Hiroyuki; Fukao, Taishi; Minami, Hirotake; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji

    2014-01-01

    X-ray absorption near edge structure (XANES) spectra for adenine-containing nucleotides, adenosine 5‧-monophosphate (AMP) and adenosine 5‧-triphosphate (ATP) in aqueous solutions at the nitrogen K-edge region were measured. The two intense peaks in XANES spectra are assigned to transitions of 1s electrons to the π∗ orbitals of different types of N atoms with particular bonding characteristics. The difference between their spectra is ascribed to protonation of a particular N atom. Similarity observed in XANES spectra of guanosine 5‧-monophosphate (GMP) and ATP is also interpreted as similar bonding characters of the N atoms in the nucleobase moiety.

  3. Anisotropy of Chemical Bonds in Collagen Molecules Studied by X-ray Absorption Near-Edge Structure (XANES) Spectroscopy

    PubMed Central

    Lam, Raymond S.K.; Metzler, Rebecca A.; Gilbert, Pupa U.P.A.; Beniash, Elia

    2012-01-01

    Collagen type I fibrils are the major building blocks of connective tissues. Collagen fibrils are anisotropic supra-molecular structures, and their orientation can be revealed by polarized light microscopy and vibrational microspectroscopy. We hypothesized that the anisotropy of chemical bonds in the collagen molecules, and hence their orientation, might also be detected by X-ray photoemission electron spectromicroscopy (X-PEEM) and X-ray absorption near-edge structure (XANES) spectroscopy, which use linearly polarized synchrotron light. To test this hypothesis, we analyzed sections of rat-tail tendon, composed of parallel arrays of collagen fibrils. The results clearly indicate that XANES-PEEM is sensitive to collagen fibril orientation and, more specifically, to the orientations of carbonyl and amide bonds in collagen molecules. These data suggest that XANES-PEEM is a promising technique for characterizing the chemical composition and structural organization at the nanoscale of collagen-based connective tissues, including tendons, cartilage, and bone. PMID:22148847

  4. Reduced chromium in olivine grains from lunar basalt 15555 - X-ray Absorption Near Edge Structure (XANES)

    NASA Technical Reports Server (NTRS)

    Sutton, S. R.; Jones, K. W.; Gordon, B.; Rivers, M. L.; Bajt, S.; Smith, J. V.

    1993-01-01

    The oxidation state of Cr in 200-micron regions within individual lunar olivine and pyroxene grains from lunar basalt 15555 was inferred using X-ray Absorption Near Edge Structure (XANES). Reference materials had previously been studied by optical absorption spectroscopy and included Cr-bearing borosilicate glasses synthesized under controlled oxygen fugacity and Cr-doped olivines. The energy dependence of XANES spectral features defined by these reference materials indicated that Cr is predominantly divalent in the lunar olivine and trivalent in the pyroxene. These results, coupled with the apparent f(02)-independence of partitioning coefficients for Cr into olivine, imply that the source magma was dominated by divalent Cr at the time of olivine crystallization.

  5. Probing Warm Dense Matter electronic structure using X-ray absorption Near Edge Spectroscopy (XANES)

    NASA Astrophysics Data System (ADS)

    Benuzzi Mounaix, Alessandra

    2011-06-01

    The behavior and physical properties of warm dense matter, fundamental for various branches of physics including planetology and Inertial Confinement Fusion, are non trivial to simulate either theoretically, numerically or experimentally. Despite important progress obtained in the last decade on macroscopic characterization (e.g. equations of state), microscopic studies are today necessary to investigate finely the WDM structure changes, the phase transitions and to test physical hypothesis and approximations commonly used in calculations. In this work, highly compressed aluminum has been investigated with the aim of bringing information on the evolution of its electronic structure by using K-edge shift and XANES. The experiment was performed at LULI laboratory where we used one long pulse (500 ps, IL ~ 8 1013 W/cm2) to create a uniform shock and a second ps beam (IL ~ 1017 W/cm2) to generate an ultra-short broadband X-ray source near the Al K-edge. The spectra were registered by using two conical KAP Bragg crystals. The main target was designed to probe the Aluminum in reshocked conditions allowing us to probe and to test theories in an extreme regime up to now unexplored (ρ ~ 3 ρ0 and T ~ 8 eV). The hydrodynamical Al conditions were measured by using VISARs interferometers and self-emission diagnostics. By increasing the delay between the two beams, we have been able to observe the modification of absorption spectra for unloading Al conditions (ρ >= 0.5 g/cc), and to put in evidence the relocalization of the 3p valence electrons occurring in the metal-non metal transition. All data have been compared to ab initio and dense plasma calculations.

  6. Speciation of sulfur in humic and fulvic acids using X-ray absorption near-edge structure (XANES) spectroscopy

    NASA Astrophysics Data System (ADS)

    Morra, Matthew J.; Fendorf, Scott E.; Brown, Paul D.

    1997-02-01

    Sulfur species in soils and sediments have previously been determined indirectly using destructive techniques. A direct and more accurate method for S speciation would improve our understanding of S biogeochemistry. X-ray absorption near edge structure (XANES) spectroscopy was performed on purified humic and fulvic acids from terrestrial and aquatic environments. This methodology allows direct determination of S species using the relationship that exists with the energy required for core electron transitions and in some cases, correlation with additional spectral features. Soil, peat, and aquatic humic acids were dominated by sulfonates with an oxidation state of +5, but also contained ester-bonded sulfates with an oxidation state of +6. Leonardite humic acid contained ester-bonded sulfate and an unidentified S compound with an oxidation state of +4.0. In contrast, high-valent S in soil, peat, and aquatic fulvic acids was exclusively in the form of sulfonic acids. Reduced S species were also present in both humic and fulvic acids. XANES is a valuable method for the speciation of S in humic materials and of potential use in S speciation of unfractionated soils.

  7. Speciation of sulfur in humic and fulvic acids using X-ray Absorption Near-Edge Structures (XANES) spectroscopy

    SciTech Connect

    Morra, M.J.; Fendorf, S.E.; Brown, P.D.

    1997-02-01

    Sulfur species in soils and sediments have previously been determined indirectly using destructive techniques. A direct and more accurate method for S speciation would improve our understanding of S biogeochemistry. X-ray absorption near edge structure (XANES) spectroscopy was performed on purified humic and fulvic acids from terrestrial and aquatic environments. This methodology allows direct determination of S species using the relationship that exists with the energy required for core electron transitions and in some cases, correlation with additional spectral features. Soil, peat, and aquatic humic acids were dominated by sulfonates with an oxidation state of +5, but also contained ester-bonded sulfates with an oxidation state of +6. Leonardite humic acid contained ester-bonded sulfate and an unidentified S compound with an oxidation state of +4.0. In contrast, high-valent S in soil, peat, and aquatic fulvic acids was exclusively in the form of sulfonic acids. Reduced S species were also present in both humic and fulvic acids. XANES is a valuable method for the speciation of S in humic materials and of potential use in S speciation of unfractionated soils. 27 refs., 4 figs., 3 tabs.

  8. Nitrogen K-edge X-ray absorption near edge structure (XANES) spectra of purine-containing nucleotides in aqueous solution

    NASA Astrophysics Data System (ADS)

    Shimada, Hiroyuki; Fukao, Taishi; Minami, Hirotake; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji

    2014-08-01

    The N K-edge X-ray absorption near edge structure (XANES) spectra of the purine-containing nucleotide, guanosine 5'-monophosphate (GMP), in aqueous solution are measured under various pH conditions. The spectra show characteristic peaks, which originate from resonant excitations of N 1s electrons to π* orbitals inside the guanine moiety of GMP. The relative intensities of these peaks depend on the pH values of the solution. The pH dependence is explained by the core-level shift of N atoms at specific sites caused by protonation and deprotonation. The experimental spectra are compared with theoretical spectra calculated by using density functional theory for GMP and the other purine-containing nucleotides, adenosine 5'-monophosphate, and adenosine 5'-triphosphate. The N K-edge XANES spectra for all of these nucleotides are classified by the numbers of N atoms with particular chemical bonding characteristics in the purine moiety.

  9. X-ray absorption near-edge structure (XANES) spectroscopy study of the interaction of silver ions with Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli.

    PubMed

    Bovenkamp, Gudrun Lisa; Zanzen, Ulrike; Krishna, Katla Sai; Hormes, Josef; Prange, Alexander

    2013-10-01

    Silver ions are widely used as antibacterial agents, but the basic molecular mechanism of this effect is still poorly understood. X-ray absorption near-edge structure (XANES) spectroscopy at the Ag LIII, S K, and P K edges reveals the chemical forms of silver in Staphylococcus aureus and Escherichia coli (Ag(+) treated). The Ag LIII-edge XANES spectra of the bacteria are all slightly different and very different from the spectra of silver ions (silver nitrate and silver acetate), which confirms that a reaction occurs. Death or inactivation of bacteria was observed by plate counting and light microscopy. Silver bonding to sulfhydryl groups (Ag-S) in cysteine and Ag-N or Ag-O bonding in histidine, alanine, and DL-aspartic acid was detected by using synthesized silver-amino acids. Significantly lower silver-cysteine content, coupled with higher silver-histidine content, in Gram-positive S. aureus and Listeria monocytogenes cells indicates that the peptidoglycan multilayer could be buffering the biocidal effect of silver on Gram-positive bacteria, at least in part. Bonding of silver to phosphate groups was not detected. Interaction with DNA or proteins can occur through Ag-N bonding. The formation of silver-cysteine can be confirmed for both bacterial cell types, which supports the hypothesis that enzyme-catalyzed reactions and the electron transport chain within the cell are disrupted. PMID:23934494

  10. Nitrogen K-edge X-ray absorption near edge structure (XANES) spectra of purine-containing nucleotides in aqueous solution

    SciTech Connect

    Shimada, Hiroyuki; Fukao, Taishi; Minami, Hirotake; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji

    2014-08-07

    The N K-edge X-ray absorption near edge structure (XANES) spectra of the purine-containing nucleotide, guanosine 5{sup ′}-monophosphate (GMP), in aqueous solution are measured under various pH conditions. The spectra show characteristic peaks, which originate from resonant excitations of N 1s electrons to π* orbitals inside the guanine moiety of GMP. The relative intensities of these peaks depend on the pH values of the solution. The pH dependence is explained by the core-level shift of N atoms at specific sites caused by protonation and deprotonation. The experimental spectra are compared with theoretical spectra calculated by using density functional theory for GMP and the other purine-containing nucleotides, adenosine 5{sup ′}-monophosphate, and adenosine 5{sup ′}-triphosphate. The N K-edge XANES spectra for all of these nucleotides are classified by the numbers of N atoms with particular chemical bonding characteristics in the purine moiety.

  11. The origin of luminescence from di[4-(4-diphenylaminophenyl)phenyl]sulfone (DAPSF), a blue light emitter: an X-ray excited optical luminescence (XEOL) and X-ray absorption near edge structure (XANES) study.

    PubMed

    Zhang, Duo; Zhang, Hui; Zhang, Xiaohong; Sham, Tsun-Kong; Hu, Yongfeng; Sun, Xuhui

    2016-02-24

    The electronic structure and optical properties of di[4-(4-diphenylaminophenyl)phenyl]sulfone (denoted as DAPSF), a highly efficient fluorophor, have been investigated using X-ray excited optical luminescence (XEOL) and X-ray absorption near edge structure (XANES) spectroscopy at excitation energies across the C, N, O K-edges and the sulfur K-edge. The results indicate that the blue luminescence is mainly related to the sulfur functional group. PMID:26866785

  12. Diurnal Variation and Spatial Distribution Effects on Sulfur Speciation in Aerosol Samples as Assessed by X-Ray Absorption Near-Edge Structure (XANES)

    PubMed Central

    Pongpiachan, Siwatt; Thumanu, Kanjana; Na Pattalung, Warangkana; Hirunyatrakul, Phoosak; Kittikoon, Itthipon; Ho, Kin Fai; Cao, Junji

    2012-01-01

    This paper focuses on providing new results relating to the impacts of Diurnal variation, Vertical distribution, and Emission source on sulfur K-edge XANES spectrum of aerosol samples. All aerosol samples used in the diurnal variation experiment were preserved using anoxic preservation stainless cylinders (APSCs) and pressure-controlled glove boxes (PCGBs), which were specially designed to prevent oxidation of the sulfur states in PM10. Further investigation of sulfur K-edge XANES spectra revealed that PM10 samples were dominated by S(VI), even when preserved in anoxic conditions. The “Emission source effect” on the sulfur oxidation state of PM10 was examined by comparing sulfur K-edge XANES spectra collected from various emission sources in southern Thailand, while “Vertical distribution effects” on the sulfur oxidation state of PM10 were made with samples collected from three different altitudes from rooftops of the highest buildings in three major cities in Thailand. The analytical results have demonstrated that neither “Emission source” nor “Vertical distribution” appreciably contribute to the characteristic fingerprint of sulfur K-edge XANES spectrum in PM10. PMID:22988545

  13. Element distribution and iron speciation in mature wheat grains (Triticum aestivum L.) using synchrotron X-ray fluorescence microscopy mapping and X-ray absorption near-edge structure (XANES) imaging.

    PubMed

    De Brier, Niels; Gomand, Sara V; Donner, Erica; Paterson, David; Smolders, Erik; Delcour, Jan A; Lombi, Enzo

    2016-08-01

    Several studies have suggested that the majority of iron (Fe) and zinc (Zn) in wheat grains are associated with phytate, but a nuanced approach to unravel important tissue-level variation in element speciation within the grain is lacking. Here, we present spatially resolved Fe-speciation data obtained directly from different grain tissues using the newly developed synchrotron-based technique of X-ray absorption near-edge spectroscopy imaging, coupling this with high-definition μ-X-ray fluorescence microscopy to map the co-localization of essential elements. In the aleurone, phosphorus (P) is co-localized with Fe and Zn, and X-ray absorption near-edge structure imaging confirmed that Fe is chelated by phytate in this tissue layer. In the crease tissues, Zn is also positively related to P distribution, albeit less so than in the aleurone. Speciation analysis suggests that Fe is bound to nicotianamine rather than phytate in the nucellar projection, and that more complex Fe structures may also be present. In the embryo, high Zn concentrations are present in the root and shoot primordium, co-occurring with sulfur and presumably bound to thiol groups. Overall, Fe is mainly concentrated in the scutellum and co-localized with P. This high resolution imaging and speciation analysis reveals the complexity of the physiological processes responsible for element accumulation and bioaccessibility. PMID:27038325

  14. Three Dimensional Mapping of Nicle Oxidation States Using Full Field Xray Absorption Near Edge Structure Nanotomography

    SciTech Connect

    Nelson, G.J.; Chu, Y.; Harris, W.M.; Izzo, J.R.; Grew, K.N., Chiu, W.K.S.; Yi, J.; Andrews, J.C.; Liu, Y., Pierro, P.

    2011-04-28

    The reduction-oxidation cycling of the nickel-based oxides in composite solid oxide fuel cells and battery electrodes is directly related to cell performance. A greater understanding of nickel redox mechanisms at the microstructural level can be achieved in part using transmission x-ray microscopy (TXM) to explore material oxidation states. X-ray nanotomography combined with x-ray absorption near edge structure (XANES) spectroscopy has been applied to study samples containing distinct regions of nickel and nickel oxide (NiO) compositions. Digitally processed images obtained using TXM demonstrate the three-dimensional chemical mapping and microstructural distribution capabilities of full-field XANES nanotomography.

  15. Structural analysis of sulfur in natural rubber using X-ray absorption near-edge spectroscopy.

    PubMed

    Pattanasiriwisawa, Wanwisa; Siritapetawee, Jaruwan; Patarapaiboolchai, Orasa; Klysubun, Wantana

    2008-09-01

    X-ray absorption near-edge spectroscopy (XANES) has been applied to natural rubber in order to study the local environment of sulfur atoms in sulfur crosslinking structures introduced in the vulcanization process. Different types of chemical accelerators in conventional, semi-efficient and efficient vulcanization systems were investigated. The experimental results show the good sensitivity and reproducibility of XANES to characterize the local geometry and electronic environment of the sulfur K-shell under various conditions of vulcanization and non-vulcanization of natural rubber. Several applications of XANES in this study demonstrate an alternative way of identifying sulfur crosslinks in treated natural rubber based on differences in their spectra and oxidation states. PMID:18728323

  16. First-principles study of phonon effects in x-ray absorption near-edge structure spectroscopy

    NASA Astrophysics Data System (ADS)

    Nemausat, R.; Brouder, Ch; Gervais, Ch; Cabaret, D.

    2016-05-01

    Usually first-principles x-ray absorption near-edge structure (XANES) calculations are performed in the Born-Oppenheimer approximation assuming a static lattice, whereas the nuclear motion undoubtedly impacts XANES spectra notably at the K pre-edge of light elements in oxides. Here, an efficient method based on density-functional theory to account for quantum thermal fluctuations of nuclei is developed and is successfully applied to the K edge of corundum for temperatures up to 930 K. The zero-point motion influence is estimated. Comparison is made with previous theoretical approaches also developed to account for vibrations in XANES.

  17. Three-dimensional mapping of nickel oxidation states using full field x-ray absorption near edge structure nanotomography

    SciTech Connect

    Nelson, George J.; Harris, William M.; Izzo, John R. Jr.; Grew, Kyle N.; Chiu, Wilson K. S.; Chu, Yong S.; Yi, Jaemock; Andrews, Joy C.; Liu Yijin; Pianetta, Piero

    2011-04-25

    The reduction-oxidation cycling of the nickel-based oxides in composite solid oxide fuel cells and battery electrodes is directly related to cell performance. A greater understanding of nickel redox mechanisms at the microstructural level can be achieved in part using transmission x-ray microscopy (TXM) to explore material oxidation states. X-ray nanotomography combined with x-ray absorption near edge structure (XANES) spectroscopy has been applied to study samples containing distinct regions of nickel and nickel oxide (NiO) compositions. Digitally processed images obtained using TXM demonstrate the three-dimensional chemical mapping and microstructural distribution capabilities of full-field XANES nanotomography.

  18. Three-dimensional mapping of nickel oxidation states using full field x-ray absorption near edge structure nanotomography

    NASA Astrophysics Data System (ADS)

    Nelson, George J.; Harris, William M.; Izzo, John R.; Grew, Kyle N.; Chiu, Wilson K. S.; Chu, Yong S.; Yi, Jaemock; Andrews, Joy C.; Liu, Yijin; Pianetta, Piero

    2011-04-01

    The reduction-oxidation cycling of the nickel-based oxides in composite solid oxide fuel cells and battery electrodes is directly related to cell performance. A greater understanding of nickel redox mechanisms at the microstructural level can be achieved in part using transmission x-ray microscopy (TXM) to explore material oxidation states. X-ray nanotomography combined with x-ray absorption near edge structure (XANES) spectroscopy has been applied to study samples containing distinct regions of nickel and nickel oxide (NiO) compositions. Digitally processed images obtained using TXM demonstrate the three-dimensional chemical mapping and microstructural distribution capabilities of full-field XANES nanotomography.

  19. Angle-resolved x-ray absorption near edge structure study of vertically aligned single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Li, Zhongrui; Zhang, Liang; Resasco, Daniel E.; Mun, Bongjin Simon; Requejo, Félix G.

    2007-03-01

    Vertically aligned single-walled carbon nanotube (SWNT) forest was studied by using angular-dependent C K-edge x-ray absorption near edge structure (XANES) with linearly polarized x-ray beam. The XANES analysis found a crust of entangled nanotubes on top of the forest formed at the first stage of the forest growth, which shapes the morphology of the entire forest and constricts the nanotubes to grow to the same length. It indicates that this type of SWNT forest has a different growth mechanism from the multiwalled carbon nanotube forest.

  20. Solving local structure around dopants in metal nanoparticles with ab initio modeling of X-ray absorption near edge structure

    DOE PAGESBeta

    Timoshenko, J.; Shivhare, A.; Scott, R. W.; Lu, D.; Frenkel, A. I.

    2016-06-30

    We adopted ab-initio X-ray Absorption Near Edge Structure (XANES) modelling for structural refinement of local environments around metal impurities in a large variety of materials. Our method enables both direct modelling, where the candidate structures are known, and the inverse modelling, where the unknown structural motifs are deciphered from the experimental spectra. We present also estimates of systematic errors, and their influence on the stability and accuracy of the obtained results. We illustrate our approach by following the evolution of local environment of palladium atoms in palladium-doped gold thiolate clusters upon chemical and thermal treatments.

  1. Micro-x-ray absorption near-edge structure imaging for detecting metallic Mn in GaN

    NASA Astrophysics Data System (ADS)

    Martínez-Criado, G.; Somogyi, A.; Homs, A.; Tucoulou, R.; Susini, J.

    2005-08-01

    In this study, we report the application of a synchrotron radiation microprobe to the analysis of Mn valencies in GaN. X-ray absorption near-edge structure (XANES) images taken around MnK-edge in fluorescence detection mode reveal the concentration of oxidation states of Mn centers. By fitting the XANES curve for each point of the image, the distributions of the Mn0, Mn2+, and Mn3+ oxidation states are obtained. At low Mn concentrations, there is a homogeneous mixture of Mn2+ and Mn3+ centers, while at high Mn content strong spatial-dependent Mn0 and Mn2+ distributions characterize the XANES maps. In a supplementary way with respect to Mn2+, the Mn0 pattern suggests the presence of specific cluster-like features, indicating surface segregation of metallic Mn centers.

  2. 3D Imaging of Nickel Oxidation States using Full Field X-ray Absorption Near Edge Structure Nanotomography

    SciTech Connect

    Nelson, George; Harris, William; Izzo, John; Grew, Kyle N.

    2012-01-20

    Reduction-oxidation (redox) cycling of the nickel electrocatalyst phase in the solid oxide fuel cell (SOFC) anode can lead to performance degradation and cell failure. A greater understanding of nickel redox mechanisms at the microstructural level is vital to future SOFC development. Transmission x-ray microscopy (TXM) provides several key techniques for exploring oxidation states within SOFC electrode microstructure. Specifically, x-ray nanotomography and x-ray absorption near edge structure (XANES) spectroscopy have been applied to study samples of varying nickel (Ni) and nickel oxide (NiO) compositions. The imaged samples are treated as mock SOFC anodes containing distinct regions of the materials in question. XANES spectra presented for the individual materials provide a basis for the further processing and analysis of mixed samples. Images of composite samples obtained are segmented, and the distinct nickel and nickel oxide phases are uniquely identified using full field XANES spectroscopy. Applications to SOFC analysis are discussed.

  3. An energy and intensity monitor for X-ray absorption near-edge structure measurements

    NASA Astrophysics Data System (ADS)

    de Jonge, Martin D.; Paterson, David; McNulty, Ian; Rau, Christoph; Brandes, Jay A.; Ingall, Ellery

    2010-07-01

    An in-line X-ray beam energy and intensity monitor has been developed for use in focussed X-ray absorption near-edge spectroscopy (XANES) measurements. The monitor uses only the X-ray intensity that would otherwise bypass our zone-plate focussing optic and relies on a measurement of photoemission current. The monitor is inexpensive, easy to align, and provides valuable feedback about the X-ray energy. Operation of the monitor is demonstrated for measurements of phosphorus XANES. The precision of the energy determination is around 0.5 eV.

  4. Nitrogen K-edge x-ray absorption near edge structure of pyrimidine-containing nucleotides in aqueous solution

    SciTech Connect

    Shimada, Hiroyuki Minami, Hirotake; Okuizumi, Naoto; Sakuma, Ichiro; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji

    2015-05-07

    X-ray absorption near edge structure (XANES) was measured at energies around the N K-edge of the pyrimidine-containing nucleotides, cytidine 5′-monophosphate (CMP), 2′-deoxythymidine 5′-monophosphate (dTMP), and uridine 5′-monophosphate (UMP), in aqueous solutions and in dried films under various pH conditions. The features of resonant excitations below the N K-edge in the XANES spectra for CMP, dTMP, and UMP changed depending on the pH of the solutions. The spectral change thus observed is systematically explained by the chemical shift of the core-levels of N atoms in the nucleobase moieties caused by structural changes due to protonation or deprotonation at different proton concentrations. This interpretation is supported by the results of theoretical calculations using density functional theory for the corresponding nucleobases in the neutral and protonated or deprotonated forms.

  5. Nitrogen K-edge x-ray absorption near edge structure of pyrimidine-containing nucleotides in aqueous solution

    NASA Astrophysics Data System (ADS)

    Shimada, Hiroyuki; Minami, Hirotake; Okuizumi, Naoto; Sakuma, Ichiro; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji

    2015-05-01

    X-ray absorption near edge structure (XANES) was measured at energies around the N K-edge of the pyrimidine-containing nucleotides, cytidine 5'-monophosphate (CMP), 2'-deoxythymidine 5'-monophosphate (dTMP), and uridine 5'-monophosphate (UMP), in aqueous solutions and in dried films under various pH conditions. The features of resonant excitations below the N K-edge in the XANES spectra for CMP, dTMP, and UMP changed depending on the pH of the solutions. The spectral change thus observed is systematically explained by the chemical shift of the core-levels of N atoms in the nucleobase moieties caused by structural changes due to protonation or deprotonation at different proton concentrations. This interpretation is supported by the results of theoretical calculations using density functional theory for the corresponding nucleobases in the neutral and protonated or deprotonated forms.

  6. Study on Coloration Mechanism of Chinese Ancient Ceramics by X-ray Absorption Near-edge Structure

    NASA Astrophysics Data System (ADS)

    Peng, Y. H.; Xie, Z.; He, J. F.; Liu, Q. H.; Pan, Z. Y.; Cheng, W. R.; Wei, S. Q.

    2013-04-01

    The Fe K-edge X-ray absorption near-edge structure (XANES) spectra of a series of ceramic shards were measured by fluorescence mode to reveal the color-generating techniques of Chinese porcelain. The analysis disclosed relationships among the chemical form of the iron, the firing conditions and the colors of the ceramics. The results indicate that the coloration for different ceramics depend on the valence states of iron as the main color element in glaze and the proportion of Fe2+ and Fe3+ was attributed to the baking technology. The findings provide important information for archaeologist on the coloration researches.

  7. Tracking Drug Loading Capacities of Calcium Silicate Hydrate Carrier: A Comparative X-ray Absorption Near Edge Structures Study.

    PubMed

    Guo, Xiaoxuan; Wang, Zhiqiang; Wu, Jin; Yiu, Yun-Mui; Hu, Yongfeng; Zhu, Ying-Jie; Sham, Tsun-Kong

    2015-08-01

    Mesoporous spheres of calcium silicate hydrate (MS-CSH) have been prepared by an ultrasonic method. Following an earlier work in which we have revealed the interactions between ibuprofen (IBU) and CSH carriers with different morphologies by X-ray absorption near edge structures (XANES) analysis. In the present investigation, two new drug molecules, alendronate sodium (ALN) and gentamicin sulfate (GS), were incorporated into MS-CSH, and their drug loading capacities (DLCs) were measured using thermogravimetric analysis to establish the relationship between drug-carrier interactions and DLCs. The XANES spectra clearly indicate that acidic functional groups of the drug molecules linked to the active sites (Ca-OH and Si-OH groups) of MS-CSH on the surface by electrostatic interactions. In addition, it is found that the stoichiometric ratio of Ca(2+) ions of CSH carriers and the functional groups of drug molecules may significantly influence the DLCs. PMID:26162602

  8. Characterization of Oxygen Containing Functional Groups on Carbon Materials with Oxygen K-edge X-ray Absorption Near Edge Structure Spectroscopy

    SciTech Connect

    K Kim; P Zhu; L Na; X Ma; Y Chen

    2011-12-31

    Surface functional groups on carbon materials are critical to their surface properties and related applications. Many characterization techniques have been used to identify and quantify the surface functional groups, but none is completely satisfactory especially for quantification. In this work, we used oxygen K-edge X-ray absorption near edge structure (XANES) spectroscopy to identify and quantify the oxygen containing surface functional groups on carbon materials. XANES spectra were collected in fluorescence yield mode to minimize charging effect due to poor sample conductivity which can potentially distort XANES spectra. The surface functional groups are grouped into three types, namely carboxyl-type, carbonyl-type, and hydroxyl-type. XANES spectra of the same type are very similar while spectra of different types are significantly different. Two activated carbon samples were analyzed by XANES. The total oxygen contents of the samples were estimated from the edge step of their XANES spectra, and the identity and abundance of different functional groups were determined by fitting of the sample XANES spectrum to a linear combination of spectra of the reference compounds. It is concluded that oxygen K-edge XANES spectroscopy is a reliable characterization technique for the identification and quantification of surface functional groups on carbon materials.

  9. X-ray absorption near-edge structure micro-spectroscopy study of vanadium speciation in Phycomyces blakesleeanus mycelium.

    PubMed

    Žižić, Milan; Dučić, Tanja; Grolimund, Daniel; Bajuk-Bogdanović, Danica; Nikolic, Miroslav; Stanić, Marina; Križak, Strahinja; Zakrzewska, Joanna

    2015-09-01

    Vanadium speciation in the fungus Phycomyces blakesleeanus was examined by X-ray absorption near-edge structure (XANES) spectroscopy, enabling assessment of oxidation states and related molecular symmetries of this transition element in the fungus. The exposure of P. blakesleeanus to two physiologically important vanadium species (V(5+) and V(4+)) resulted in the accumulation of this metal in central compartments of 24 h old mycelia, most probably in vacuoles. Tetrahedral V(5+), octahedral V(4+), and proposed intracellular complexes of V(5+) were detected simultaneously after addition of a physiologically relevant concentration of V(5+) to the mycelium. A substantial fraction of the externally added V(4+) remained mostly in its original form. However, observable variations in the pre-edge-peak intensities in the XANES spectra indicated intracellular complexation and corresponding changes in the molecular coordination symmetry. Vanadate complexation was confirmed by (51)V NMR and Raman spectroscopy, and potential binding compounds including cell-wall constituents (chitosan and/or chitin), (poly)phosphates, DNA, and proteins are proposed. The evidenced vanadate complexation and reduction could also explain the resistance of P. blakesleeanus to high extracellular concentrations of vanadium. PMID:26253227

  10. Multiple-scattering calculations of the uranium L3-edge x-ray-absorption near-edge structure

    NASA Astrophysics Data System (ADS)

    Hudson, E. A.; Rehr, J. J.; Bucher, J. J.

    1995-11-01

    A theoretical study of the uranium L3-edge x-ray absorption near-edge structure (XANES) is presented for several uranium compounds, including oxides, intermetallics, uranyl fluoride, and α-uranium. Calculations were performed using feff6, an ab initio multiple-scattering (MS) code that includes the most important features of current theories. The results, which account for both the fine structure χ and the atomiclike background μ0 of the absorption coefficient μ, are compared to new and previously measured experimental spectra, reavealing very good agreement for most systems. For several compounds, a more detailed theoretical analysis determined the influence of cluster size and scattering order upon the calculated spectra. Results indicate that MS paths and scattering paths that include rather distant atoms make significant contributions for UO2, whereas XANES for crystals with lower symmetry and density can be modeled using only shorter single-scattering paths. In most cases, assumption of a screened final state in the calculation gives better agreement with experiment than use of an unscreened final state. The successful modeling of spectra for a variety of different uranium compounds, with differing spectral features, indicates that the semirelativistic treatment of XANES used here is adequate even for heavy elements. The well-known resonance, observed experimentally for uranyl (UO2+2) compounds ~=15 eV above the white line, is successfully modeled here for the first time, using multiple-scattering paths within the O-U-O axial bonds. Overlapping muffin-tin spheres were required in the calculation, probably as a result of the short uranyl axial bonds.

  11. Core-hole effects on theoretical electron-energy-loss near-edge structure and near-edge x-ray absorption fine structure of MgO

    NASA Astrophysics Data System (ADS)

    Mizoguchi, Teruyasu; Tanaka, Isao; Yoshiya, Masato; Oba, Fumiyasu; Ogasawara, Kazuyoshi; Adachi, Hirohiko

    2000-01-01

    First-principles molecular orbital calculations using model clusters are made in order to reproduce and interpret experimental electron-energy-loss near-edge structure and near-edge x-ray absorption fine structure of MgO at Mg K, L2,3 and O K edges. Ground-state calculations using a model cluster composed of 125 atoms and by a band-structure method are in good agreement, but they do not reproduce the experimental spectra satisfactory. They are well reproduced only by the cluster calculations for the Slater transition state, where a half-electron is removed from a core orbital and placed into the lowest unoccupied molecular orbital. The core-hole effect is therefore essential for theoretical reproduction of the spectral shapes. A large supercell is required to reproduce the experimental spectra when one uses a band-structure method. The origin of peaks appearing in the experimental spectra is interpreted in terms of orbital interactions using overlap-population diagrams. Some features of the spectra at different edges are pointed out to have common origins. Experimental spectra are aligned accordingly. The transition energies and qualitative features of experimental spectra are found to be reproduced even using a smaller cluster composed of 27 atoms, although some of fine structure is missing.

  12. Photoelectron Experiments and Studies of X-Ray Absorption Near Edge Structure in Alkaline-Earth and Rare - Fluorides.

    NASA Astrophysics Data System (ADS)

    Gao, Yuan

    Alkaline-earth fluorides and rare-earth trifluorides possess technological importance for applications in multi -layer electronic device structures and opto-electronic devices. Interfaces between thin films of YbF _3 and Si(111) substrates were studied by photoelectron spectroscopy and x-ray absorption spectroscopy using synchrotron radiation. Results of YbF_3 /Si(111) were compared with those of TmF _3/Si(111). While electrons in the Si valence band are prevented from occupying the empty 4f levels in TmF_3 at the interface by the on -site Coulomb repulsion energy, the charge transfer from Si to YbF_3 is possible because the totally filled 4f states in Yb still lie below the Si valence band maximum. The theory of x-ray absorption near edge structure (XANES) is incomplete except for a few particularly simple special cases. A Bragg reflection model was developed to qualitatively explain the oscillations in XANES, in terms of the scattering of the photoelectron wave between families of lattice planes as set out by the Bragg condition for backscattering. The model was found to represent the data for systems with nearly free electron like conduction bands reasonably well. High resolution CaF_2 fluorine K edge XANES was used as a prototype to understand XANES in more depth on systems with strong core hole effects. Unlike previous work which involved multiple scattering cluster calculations that include only short range order effects, both the long range order and the symmetry breaking core holes are included in a new bandstructure approach in which the core hole is treated with a supercell technique. A first principles calculation with the use of pseudopotentials successfully reproduced all the main features of the first 15 eV of the fluorine K edge in CaF_2 which had not been explained with the cluster calculations. A comparison of the theoretical and experimental fluorine K edges in CaF_2 and BaF _2 was used to identify the structure related features. The possibility

  13. Sulfur and nitrogen speciation in humic substances by x-ray absorption near-edge structure spectroscopy

    SciTech Connect

    Vairavamurthy, M.A.; Wang, Shenghe; Maletic, D.

    1996-12-31

    Understanding the chemical composition and structure of complex macromolecules in the geosphere, such as humic substances and kerogen, poses a challenging analytical problem. Widely used chromatographic techniques, such as the pyrolysis GC-MS, cause severe changes in structure during preparation and analysis of the sample, and thus, may not give accurate information. An important non-destructive technique that is becoming popular in speciation studies of environmental and geochemical samples is x-ray absorption fine structure spectroscopy. We used the x-ray absorption near-edge structure (XANFS) spectroscopy for examining the speciation of sulfur and nitrogen in humic substances of different origins, including soil and marine sediments. XANES provides information on the characteristics of the functional groups containing these atoms because of its sensitivity to the electronic structure, oxidation state, and the geometry of the neighboring atoms. Organic sulfides, di- and poly-sulfides, sulfonates and organic sulfates are the major forms of sulfur detected in all the humics we examined. The oxidized sulfonate-sulfur dominates the composition of sulfur species in soil humics accounting for more than 60% of the total sulfur. In marine humics, although sulfonates are abundant in near-surface sediments, reduced sulfur species, particularly di-and poly-sulfides, also constitute an important fraction. The nitrogen XANES indicates the dominance of amino and amide groups among nitrogen functionalities, although porphyrinic and pyridinic groups also are present. The significance of these results for the transformations of nitrogen and sulfur in soil and sedimentary systems will be presented.

  14. Assessment of chemical species of lead accumulated in tidemarks of human articular cartilage by X-ray absorption near-edge structure analysis

    PubMed Central

    Meirer, Florian; Pemmer, Bernhard; Pepponi, Giancarlo; Zoeger, Norbert; Wobrauschek, Peter; Sprio, Simone; Tampieri, Anna; Goettlicher, Joerg; Steininger, Ralph; Mangold, Stefan; Roschger, Paul; Berzlanovich, Andrea; Hofstaetter, Jochen G.; Streli, Christina

    2011-01-01

    A highly specific accumulation of the toxic element lead was recently measured in the transition zone between non-calcified and calcified normal human articular cartilage. This transition zone, the so-called ‘tidemark’, is considered to be an active calcification front of great clinical importance. However, little is known about the mechanisms of accumulation and the chemical form of Pb in calcified cartilage and bone. Using spatially resolved X-ray absorption near-edge structure analysis (µ-XANES) at the Pb L 3-edge, the chemical state of Pb in the osteochondral region was investigated. The feasibility of the µ-XANES set-up at the SUL-X beamline (ANKA synchrotron light source) was tested and confirmed by comparing XANES spectra of bulk Pb-reference compounds recorded at both the XAS and the SUL-X beamline at ANKA. The µ-XANES set-up was then used to investigate the tidemark region of human bone (two patella samples and one femoral head sample). The spectra recorded at the tidemark and at the trabecular bone were found to be highly correlated with the spectra of synthetic Pb-doped carbonated hydroxyapatite, suggesting that in both of these very different tissues Pb is incorporated into the hydroxyapatite structure. PMID:21335911

  15. Angular Resolved X-Ray Absorption Near Edge Structure Investigation of Adsorbed Alkanethiol Monolayers on III-V(110) Surfaces

    NASA Astrophysics Data System (ADS)

    Chassé, T.; Zerulla, D.; Hallmeier, K. H.

    The structure of alkanethiol monolayers on III-V(110) surfaces was studied by analyzing the X-ray absorption near edge structure (XANES) of the carbon K edge. Pronounced absorption maxima were observed for special orientations of the polarization vector of the radiation as revealed from angular-dependent measurements, suggesting a rather well-defined molecular axis of the alkyl chains. From quantitative evaluations of these angular dependences the chains were found to be tilted from the normal towards the [001] direction of the (110) surfaces by 34° and 15° in the case of hexadecanethiol (HDT) adsorption on InP and GaP, respectively. The similarities as well as the differences in tilt angles between the substrates are dicussed in terms of constraints imposed by the surface structure and lattice constants as well as the space requirements of the van der Waals spheres of the adsorbed thiols. A unique feature observed on these monolayers is the nearly complete alignment of the alkyl chains with respect to the azimuthal orientation. We suggest that this adsorbate system represents the case of a single domain orientation within the organic monolayer.

  16. X-ray absorption near-edge structure and nuclear magnetic resonance study of the lithium-sulfur battery and its components.

    PubMed

    Patel, Manu U M; Arčon, Iztok; Aquilanti, Giuliana; Stievano, Lorenzo; Mali, Gregor; Dominko, Robert

    2014-04-01

    Understanding the mechanism(s) of polysulfide formation and knowledge about the interactions of sulfur and polysulfides with a host matrix and electrolyte are essential for the development of long-cycle-life lithium-sulfur (Li-S) batteries. To achieve this goal, new analytical tools need to be developed. Herein, sulfur K-edge X-ray absorption near-edge structure (XANES) and (6,7) Li magic-angle spinning (MAS) NMR studies on a Li-S battery and its sulfur components are reported. The characterization of different stoichiometric mixtures of sulfur and lithium compounds (polysulfides), synthesized through a chemical route with all-sulfur-based components in the Li-S battery (sulfur and electrolyte), enables the understanding of changes in the batteries measured in postmortem mode and in operando mode. A detailed XANES analysis is performed on different battery components (cathode composite and separator). The relative amounts of each sulfur compound in the cathode and separator are determined precisely, according to the linear combination fit of the XANES spectra, by using reference compounds. Complementary information about the lithium species within the cathode are obtained by using (7) Li MAS NMR spectroscopy. The setup for the in operando XANES measurements can be viewed as a valuable analytical tool that can aid the understanding of the sulfur environment in Li-S batteries. PMID:24497200

  17. Novel Technique for Improving the Signal-to-Background Ratio of X-ray Absorption Near-Edge Structure Spectrum in Fluorescence Mode and Its Application to the Chemical State Analysis of Magnesium Doped in GaN

    NASA Astrophysics Data System (ADS)

    Yonemura, Takumi; Iihara, Junji; Saito, Yoshihiro; Ueno, Masaki

    2013-12-01

    A novel measurement technique for an X-ray absorption near-edge structure (XANES) for magnesium (Mg) doped in gallium nitride (GaN) has been developed. XANES spectra from Mg at very low concentrations of 1 ×1018/cm3 doped in GaN have successfully been obtained by optimizing the region of interest (ROI) and by using highly brilliant synchrotron radiation X-rays of SPring-8. The ROI is the limited energy region from an X-ray fluorescence spectrum to elicit signals of particular atoms. Using this new technique, we have investigated the effect of the annealing process for Mg-doped GaN on the XANES spectra. It has been found that the XANES spectra of Mg significantly changed as the annealing temperature increased. This indicates that the local structure around Mg atoms in GaN was modified by the annealing process.

  18. X-ray absorption near edge structure investigation ofvanadium-doped ZnO thin films

    SciTech Connect

    Faiz, M.; Tabet, N.; Mekki, A.; Mun, B.S.; Hussain, Z.

    2006-05-11

    X-ray absorption near edge structure spectroscopy has beenused to investigate the electronic and atomic structure of vanadium-dopedZnO thin films obtained by reactive plasma. The results show no sign ofmetallic clustering of V atoms, +4 oxidation state of V, 4-foldcoordination of Zn in the films, and a secondary phase (possibly VO2)formation at 15 percent V doping. O K edge spectra show V 3d-O 2p and Zn4d-O 2p hybridization, and suggest that V4+ acts as electron donor thatfills the sigma* band.

  19. Aluminum incorporation in Ti{sub 1-x}Al{sub x}N films studied by x-ray absorption near-edge structure

    SciTech Connect

    Gago, R.; Redondo-Cubero, A.; Endrino, J. L.; Jimenez, I.; Shevchenko, N.

    2009-06-01

    The local bonding structure of titanium aluminum nitride (Ti{sub 1-x}Al{sub x}N) films grown by dc magnetron cosputtering with different AlN molar fractions (x) has been studied by x-ray absorption near-edge structure (XANES) recorded in total electron yield mode. Grazing incidence x-ray diffraction (GIXRD) shows the formation of a ternary solid solution with cubic structure (c-Ti{sub 1-x}Al{sub x}N) that shrinks with the incorporation of Al and that, above a solubility limit of xapprox0.7, segregation of w-AlN and c-Ti{sub 1-x}Al{sub x}N phases occurs. The Al incorporation in the cubic structure and lattice shrinkage can also be observed using XANES spectral features. However, contrary to GIXRD, direct evidence of w-AlN formation is not observed, suggesting a dominance and surface enrichment of cubic environments. For x>0.7, XANES shows the formation of Ti-Al bonds, which could be related to the segregation of w-AlN. This study shows the relevance of local-order information to assess the atomic structure of Ti{sub 1-x}Al{sub x}N solutions.

  20. Near-Edge X-Ray Absorption Fine Structures Revealed in Core Ionization Photoelectron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Nakano, M.; Selles, P.; Lablanquie, P.; Hikosaka, Y.; Penent, F.; Shigemasa, E.; Ito, K.; Carniato, S.

    2013-09-01

    Simultaneous core ionization and core excitation have been observed in the C2H2n (n=1, 2, 3) molecular series using synchrotron radiation and a magnetic bottle time-of-flight electron spectrometer. Rich satellite patterns corresponding to (K-2V) core excited states of the K-1 molecular ions have been identified by detecting in coincidence the photoelectron with the two Auger electrons resulting from the double core hole relaxation. A theoretical model is proposed providing absolute photoionization cross sections and revealing clear signatures of direct (monopolar) and conjugate (dipolar near-edge x-ray absorption fine structure) shakeup lines of comparable magnitude.

  1. Near-edge x-ray absorption fine structures revealed in core ionization photoelectron spectroscopy.

    PubMed

    Nakano, M; Selles, P; Lablanquie, P; Hikosaka, Y; Penent, F; Shigemasa, E; Ito, K; Carniato, S

    2013-09-20

    Simultaneous core ionization and core excitation have been observed in the C(2)H(2n) (n=1, 2, 3) molecular series using synchrotron radiation and a magnetic bottle time-of-flight electron spectrometer. Rich satellite patterns corresponding to (K(-2)V) core excited states of the K(-1) molecular ions have been identified by detecting in coincidence the photoelectron with the two Auger electrons resulting from the double core hole relaxation. A theoretical model is proposed providing absolute photoionization cross sections and revealing clear signatures of direct (monopolar) and conjugate (dipolar near-edge x-ray absorption fine structure) shakeup lines of comparable magnitude. PMID:24093255

  2. Quantitative analysis of deconvolved X-ray absorption near-edge structure spectra: a tool to push the limits of the X-ray absorption spectroscopy technique.

    PubMed

    D'Angelo, Paola; Migliorati, Valentina; Persson, Ingmar; Mancini, Giordano; Della Longa, Stefano

    2014-09-15

    A deconvolution procedure has been applied to K-edge X-ray absorption near-edge structure (XANES) spectra of lanthanoid-containing solid systems, namely, hexakis(dmpu)praseodymium(III) and -gadolinium(III) iodide. The K-edges of lanthanoids cover the energy range 38 (La)-65 (Lu) keV, and the large widths of the core-hole states lead to broadening of spectral features, reducing the content of structural information that can be extracted from the raw X-ray absorption spectra. Here, we demonstrate that deconvolution procedures allow one to remove most of the instrumental and core-hole lifetime broadening in the K-edge XANES spectra of lanthanoid compounds, highlighting structural features that are lost in the raw data. We show that quantitative analysis of the deconvolved K-edge XANES spectra can be profitably used to gain a complete local structural characterization of lanthanoid-containing systems not only for the nearest neighbor atoms but also for higher-distance coordination shells. PMID:25171598

  3. Point defects in hexagonal BN, BC{sub 3} and BC{sub x}N compounds studied by x-ray absorption near-edge structure

    SciTech Connect

    Caretti, Ignacio; Jimenez, Ignacio

    2011-07-15

    The generation of point defects in highly oriented pyrolytic boron nitride (HOPBN) after Ar{sup +} ion bombardment in ultrahigh vacuum and subsequent exposure to air was studied by angle-resolved x-ray absorption near edge structure (XANES). The pristine HOPBN showed well-oriented boron nitride (BN) basal planes parallel to the surface, with a negligible amount of defects. Amorphization of the BN structure took place after Ar{sup +} sputtering, as indicated by the broadening of the XANES spectra and significant decrease of the characteristic {pi}* states. Following air exposure, the XANES analysis revealed a spontaneous reorganization of the sample structure. The appearance of four new B1s {pi}* excitonic peaks indicates an oxygen decoration process of the nitrogen vacancies created by ion bombardment. A core-level shift model is presented to support this statement. This model is successfully extended to the case of oxygen substitutional defects in hexagonal BC{sub 3} and BC{sub x}N (0 < x < 4) materials, which can be applied to any B-based sp{sup 2}-bonded honeycomb structure.

  4. Dynamic study of sub-micro sized LiFePO4 cathodes by in-situ tender X-ray absorption near edge structure

    NASA Astrophysics Data System (ADS)

    Wang, Dongniu; Wang, Huixin; Yang, Jinli; Zhou, Jigang; Hu, Yongfeng; Xiao, Qunfeng; Fang, Haitao; Sham, Tsun-Kong

    2016-01-01

    Olivine-type phosphates (LiMPO4, M = Fe, Mn, Co) are promising cathode materials for lithium-ion batteries that are generally accepted to follow first order equilibrium phase transformations. Herein, the phase transformation dynamics of sub-micro sized LiFePO4 particles with limited rate capability at a low current density of 0.14 C was investigated. An in-situ X-ray Absorption Near Edge Structure (XANES) measurement was conducted at the Fe and P K-edge for the dynamic studies upon lithiation and delithiation. Fe K-edge XANES spectra demonstrate that not only lithium-rich intermediate phase LixFePO4 (x = 0.6-0.75), but also lithium-poor intermediate phase LiyFePO4 (y = 0.1-0.25) exist during the charge and discharge, respectively. Furthermore, during charge and discharge, a fluctuation of the FePO4 and LiFePO4 fractions obtained by liner combination fitting around the imaginary phase fractions followed Faraday's law and the equilibrium first-order two-phase transformation versus reaction time is present, respectively. The charging and discharging process has a reversible phase transformation dynamics with symmetric structural evolution routes. P K-edge XANES spectra reveal an enrichment of PF6-1 anions at the surface of the electrode during charging.

  5. Iron speciation in human cancer cells by K-edge total reflection X-ray fluorescence-X-ray absorption near edge structure analysis

    NASA Astrophysics Data System (ADS)

    Polgári, Zs.; Meirer, F.; Sasamori, S.; Ingerle, D.; Pepponi, G.; Streli, C.; Rickers, K.; Réti, A.; Budai, B.; Szoboszlai, N.; Záray, G.

    2011-03-01

    X-ray absorption near edge structure (XANES) analysis in combination with synchrotron radiation induced total reflection X-ray fluorescence (SR-TXRF) acquisition was used to determine the oxidation state of Fe in human cancer cells and simultaneously their elemental composition by applying a simple sample preparation procedure consisting of pipetting the cell suspension onto the quartz reflectors. XANES spectra of several inorganic and organic iron compounds were recorded and compared to that of different cell lines. The XANES spectra of cells, independently from the phase of cell growth and cell type were very similar to that of ferritin, the main Fe store within the cell. The spectra obtained after CoCl 2 or NiCl 2 treatment, which could mimic a hypoxic state of cells, did not differ noticeably from that of the ferritin standard. After 5-fluorouracil administration, which could also induce an oxidative-stress in cells, the absorption edge position was shifted toward higher energies representing a higher oxidation state of Fe. Intense treatment with antimycin A, which inhibits electron transfer in the respiratory chain, resulted in minor changes in the spectrum, resembling rather the N-donor Fe-α,α'-dipyridyl complex at the oxidation energy of Fe(III), than ferritin. The incorporation of Co and Ni in the cells was followed by SR-TXRF measurements.

  6. A setup for synchrotron-radiation-induced total reflection X-ray fluorescence and X-ray absorption near-edge structure recently commissioned at BESSY II BAMline.

    PubMed

    Fittschen, U; Guilherme, A; Böttger, S; Rosenberg, D; Menzel, M; Jansen, W; Busker, M; Gotlib, Z P; Radtke, M; Riesemeier, H; Wobrauschek, P; Streli, C

    2016-05-01

    An automatic sample changer chamber for total reflection X-ray fluorescence (TXRF) and X-ray absorption near-edge structure (XANES) analysis in TXRF geometry was successfully set up at the BAMline at BESSY II. TXRF and TXRF-XANES are valuable tools for elemental determination and speciation, especially where sample amounts are limited (<1 mg) and concentrations are low (ng ml(-1) to µg ml(-1)). TXRF requires a well defined geometry regarding the reflecting surface of a sample carrier and the synchrotron beam. The newly installed chamber allows for reliable sample positioning, remote sample changing and evacuation of the fluorescence beam path. The chamber was successfully used showing accurate determination of elemental amounts in the certified reference material NIST water 1640. Low limits of detection of less than 100 fg absolute (10 pg ml(-1)) for Ni were found. TXRF-XANES on different Re species was applied. An unknown species of Re was found to be Re in the +7 oxidation state. PMID:27140163

  7. Single shot near edge x-ray absorption fine structure spectroscopy in the laboratory

    NASA Astrophysics Data System (ADS)

    Mantouvalou, I.; Witte, K.; Martyanov, W.; Jonas, A.; Grötzsch, D.; Streeck, C.; Löchel, H.; Rudolph, I.; Erko, A.; Stiel, H.; Kanngießer, B.

    2016-05-01

    With the help of adapted off-axis reflection zone plates, near edge X-ray absorption fine structure spectra at the C and N K-absorption edge have been recorded using a single 1.2 ns long soft X-ray pulse. The transmission experiments were performed with a laser-produced plasma source in the laboratory rendering time resolved measurements feasible independent on large scale facilities. A resolving power of E/ΔE ˜ 950 at the respective edges could be demonstrated. A comparison of single shot spectra with those collected with longer measuring time proves that all features of the used reference samples (silicon nitrate and polyimide) can be resolved in 1.2 ns. Hence, investigations of radiation sensitive biological specimen become possible due to the high efficiency of the optical elements enabling low dose experiments.

  8. Inorganic iodine incorporation into soil organic matter: evidence from iodine K-edge X-ray absorption near-edge structure.

    PubMed

    Yamaguchi, Noriko; Nakano, Masashi; Takamatsu, Rieko; Tanida, Hajime

    2010-06-01

    The transformation of inorganic iodine (I(-) and IO(3)(-)) incubated in soils with varying amounts of organic matter (Andosols from the surface layer of an upland field and forest, as well as Acrisols from surface and subsurface layers of an upland field) was investigated by using the iodine K-edge X-ray absorption near-edge structure (XANES). After 60d of reaction, both I(-) and IO(3)(-) were transformed into organoiodine in surface soils containing sufficient amounts of organic matter, whereas IO(3)(-) remained unchanged in the subsurface soil of Acrisols with low organic matter contents. Transformation of IO(3)(-) into organoiodine was not retarded when the microbial activity in soil was reduced by gamma-ray irradiation, suggesting that microbial activity was not essential for the transformation of inorganic iodine into organoiodine. Soil organic matter has the ability to transform inorganic iodine into organoiodine. PMID:18640749

  9. Local structure of epitaxial GeTe and Ge2Sb2Te5 films grown on InAs and Si substrates with (100) and (111) orientations: An x-ray absorption near-edge structure study

    NASA Astrophysics Data System (ADS)

    Kolobov, A. V.; Fons, P.; Krbal, M.; Tominaga, J.; Giussani, A.; Perumal, K.; Riechert, H.; Calarco, R.; Uruga, T.

    2015-03-01

    GeTe is an end-point of the GeTe-Sb2Te3 quasibinary alloys often referred to as phase-change memory materials. The polycrystalline nature of the crystalline films used in devices and the concomitant presence of grain boundaries complicate detailed structural studies of the local structure. Recent progress in the epitaxial growth of phase-change materials offers unique possibilities for precise structural investigations. In this work, we report on results of x-ray absorption near-edge structure (XANES) studies of GeTe and Ge2Sb2Te5 epitaxial films grown on Si and InAs substrates with (100) and (111) orientations. The results show a strong dependence of the local structure on the substrate material and especially orientation and are discussed in conjunction with polycrystalline samples and ab-initio XANES simulations.

  10. Near-Edge X-ray Absorption Fine Structure Spectroscopy of Diamondoid Thiol Monolayers on Gold

    SciTech Connect

    Willey, T M; Fabbri, J; Lee, J I; Schreiner, P; Fokin, A A; Tkachenko, B A; Fokina, N A; Dahl, J; Carlson, B; Vance, A L; Yang, W; Terminello, L J; van Buuren, T; Melosh, N

    2007-11-27

    Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface-modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications. This paper presents the effects of thiol substitution position and polymantane order on diamondoid SAMs on gold using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS). A framework to determine both molecular tilt and twist through NEXAFS is presented and reveals highly ordered diamondoid SAMs, with the molecular orientation controlled by the thiol location. C 1s and S 2p binding energies are lower in adamantane thiol than alkane thiols on gold by 0.67 {+-} 0.05 eV and 0.16 {+-} 0.04 eV respectively. These binding energies vary with diamondoid monolayer structure and thiol substitution position, consistent with different amounts of steric strain and electronic interaction with the substrate. This work demonstrates control over the assembly, in particular the orientational and electronic structure, providing a flexible design of surface properties with this exciting new class of diamond clusters.

  11. Near-Edge X-Ray Absorption Fine Structure Spectroscopy of Diamondoid Thiol Monolayers on Gold

    SciTech Connect

    Willey, T.M.; Fabbri, J.D.; Lee, J.R.I.; Schreiner, P.R.; Fokin, A.A.; Tkachenko, B.A.; Fokina, N.A.; Dahl, J.E.P.; Carlson, R.M.K.; Vance, A.L.; Yang, W.; Terminello, L.J.; Buuren, T.van; Melosh, N.A.

    2009-05-26

    Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications. This paper presents the effects of thiol substitution position and polymantane order on diamondoid SAMs on gold using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS). A framework to determine both molecular tilt and twist through NEXAFS is presented and reveals highly ordered diamondoid SAMs, with the molecular orientation controlled by the thiol location. C 1s and S 2p binding energies are lower in adamantane thiol than alkane thiols on gold by 0.67 {+-} 0.05 and 0.16 {+-} 0.04 eV, respectively. These binding energies vary with diamondoid monolayer structure and thiol substitution position, consistent with different degrees of steric strain and electronic interaction with the substrate. This work demonstrates control over the assembly, in particular the orientational and electronic structure, providing a flexible design of surface properties with this exciting new class of diamond nanoparticles.

  12. Core-hole effect on XANES and electronic structure of minor actinide dioxides with fluorite structure

    NASA Astrophysics Data System (ADS)

    Suzuki, Chikashi; Nishi, Tsuyoshi; Nakada, Masami; Akabori, Mitsuo; Hirata, Masaru; Kaji, Yoshiyuki

    2012-02-01

    The authors investigated theoretically core-hole effects on X-ray absorption near-edge structures (XANES) of Np and Am LIII in neptunium dioxide (NpO2) and americium dioxide (AmO2) with CaF2-type crystal lattices using the all-electron full-potential linearized augmented plane-wave (FP-LAPW) method. The peak creation mechanism of XANES was shown by examining the electronic structures of these oxides, which indicated that core-hole screening was more marked for AmO2 than for NpO2 because of the difference in the charge transfer between these oxides. Furthermore, the results of charge density analysis suggested that the white line was assigned to the quasi-bound state composed of the localized Np d or Am d components and O components, and that the tail structure was created as a result of delocalized standing waves between the Np or Am atoms.

  13. Multiple-scattering calculations of the uranium {ital L}{sub 3}-edge x-ray-absorption near-edge structure

    SciTech Connect

    Hudson, E.A.; Rehr, J.J.; Bucher, J.J.

    1995-11-15

    A theoretical study of the uranium {ital L}{sub 3}-edge x-ray absorption near-edge structure (XANES) is presented for several uranium compounds, including oxides, intermetallics, uranyl fluoride, and {alpha}-uranium. Calculations were performed using FEFF6, an {ital ab} {ital initio} multiple-scattering (MS) code that includes the most important features of current theories. The results, which account for both the fine structure {chi} and the atomiclike background {mu}{sub 0} of the absorption coefficient {mu}, are compared to new and previously measured experimental spectra, reavealing very good agreement for most systems. For several compounds, a more detailed theoretical analysis determined the influence of cluster size and scattering order upon the calculated spectra. Results indicate that MS paths and scattering paths that include rather distant atoms make significant contributions for UO{sub 2}, whereas XANES for crystals with lower symmetry and density can be modeled using only shorter single-scattering paths. In most cases, assumption of a screened final state in the calculation gives better agreement with experiment than use of an unscreened final state. The successful modeling of spectra for a variety of different uranium compounds, with differing spectral features, indicates that the semirelativistic treatment of XANES used here is adequate even for heavy elements. The well-known resonance, observed experimentally for uranyl (UO{sub 2}{sup 2+}) compounds {approx}15 eV above the white line, is successfully modeled here for the first time, using multiple-scattering paths within the O-U-O axial bonds. Overlapping muffin-tin spheres were required in the calculation, probably as a result of the short uranyl axial bonds.

  14. Structural investigation of lanthanoid coordination: a combined XANES and molecular dynamics study.

    PubMed

    D'Angelo, Paola; Zitolo, Andrea; Migliorati, Valentina; Mancini, Giordano; Persson, Ingmar; Chillemi, Giovanni

    2009-11-01

    This is the first systematic study exploring the potentiality of the X-ray absorption near edge structure (XANES) technique as a structural tool for systems containing lanthanoid(III) ions. A quantitative analysis of the XANES spectra at the K- and L(3)-edges has been carried out for three hydrated lanthanoid(III) ions, namely, Yb, Nd, and Gd, in aqueous solution and in the isostructural trifluoromethanesulfonate salts. The structural and dynamic properties of the hydrated lanthanoid(III) ions in aqueous solution have been investigated by a combined experimental-theoretical approach employing X-ray absorption spectroscopy and molecular dynamics (MD) simulations. This method allows one to perform a quantitative analysis of the XANES spectra of ionic solutions using a proper description of the thermal and structural fluctuations. XANES spectra have been computed starting from the MD trajectory, without carrying out any minimization in the structural parameter space. A comparative K- and L(3)-edge XANES data analysis is presented, demonstrating the clear advantages of the L(3)-edge XANES analysis over the K-edge studies for structural investigations of lanthanoid compounds. The second hydration shells provide a detectable contribution to the L(3)-edge spectra while the K-edge data are insensitive to the more distant coordination spheres because of the strong damping and broadening of the signal caused by the extremely large core hole widths. The XANES technique has been found to be a new valuable tool for the structural characterization of metal complexes both in the solid and in the liquid state, especially in the presence of low symmetry. PMID:19788258

  15. XANES Data on Trace Quantities of Iron in Hydroxyapatite Structures

    NASA Astrophysics Data System (ADS)

    Tabor-Morris, A.; Schaefer, B.

    2003-03-01

    Trace elements such as iron are of interest in both biologically and geologically formed apatites. They are thought to occupy substitutional sites at the concentration of about 200 ppm. Most likely metal atoms replace the calcium atom in one of two non-equivalent calcium sites. The inorganic mineral structure hydroxyapatite (which comprises 30% of human and animal bone) consists of Ca_5(OH)(PO_4)3 in a hexagonal crystal structure designated in Herman-Maugin crystallography notation as P63/m or as Number 176 in the International Tables of Crystallography (ITC). Hydroxyapatite formed under geological conditions has the same crystal structure. Hydroxyapatite can also be fabricated synthetically, but has limitations in terms of crystal growth size. The experimental technique of X-ray Absorption Near Edge Structure (XANES) and X-ray Absorption Fine-structure Spectroscopy (XAFS) were used to evaluate the oxidation state of iron. Data was taken at the X-9B line at the National Synchrotron Light Source at Brookhaven National Laboratory.

  16. Three-dimensional local structure of photoexcited Cu diimine complex refined by quantitative XANES analysis.

    SciTech Connect

    Smolentsev, G.; Soldatov, A. V.; Chen, L. X.; Chemical Sciences and Engineering Division; Southern Federal Univ.; Northwestern Univ.

    2008-05-28

    The structural details of [Cu(dmp){sub 2}]{sup +} (dmp = 2,9-dimethyl-1,10-phenanthroline) at its metal-to-ligand charge-transfer (MLCT) excited-state in acetonitrile were extracted using quantitative analysis of Cu K-edge X-ray adsorption near edge structure (XANES). The study combines two techniques: fitting experimental XANES spectra with a multidimensional interpolation approximation, and calculating theoretical XANES spectra with molecular potentials beyond the muffin-tin approximation. The results of the study show that the best fit of the experimental XANES data must include a solvent molecule binding to the Cu with a short Cu-N distance of 2.00 {angstrom}. This confirms that the formation of an exciplex is responsible for the excited-state quenching in coordinating solvents, such as acetonitrile. Moreover, the calculations suggest that the formation of this exciplex state is accompanied by significant rocking distortions of the dmp ligands resulting in a 108{sup o} angle between the N(solvent)-Cu bond and the C{sub 2} symmetry axis of the dmp ligand. This combined approach allows us to extract molecular configurations that would otherwise be missed in a conventional qualitative XANES analysis.

  17. XANES Data on Metal Ions in Hydroxyapatite Structures

    NASA Astrophysics Data System (ADS)

    Schaefer, Beth; Tabor-Morris, Anne; Simons, Adrian

    2004-03-01

    The experimental technique of X-ray Absorption Near Edge Structure (XANES) was used to compare the absorption edges of different oxidation states of iron, strontium, lead, copper and zinc in the inorganic mineral structure hydroxyapatite and fluoroapatite. Trace elements such as iron, copper, zinc, lead and strontium are of interest in both biologically and geologically formed apatites. They are thought to occupy substitutional sites at the concentration of about 200 ppm. These metal atoms replace the calcium atom in one of two non-equivalent calcium sites. Hydroxyapatite consists of Ca _5 (OH)(PO_4)3 in a hexagonal crystal structure. Hydroxyapatite formed under geological conditions has the same crystal structure. Data was taken at the X-9B line at the National Synchrotron Light Source at Brookhaven National Laboratory. Samples were obtained from Dr. Susan G. Sheridan, at the University of Notre Dame, Dr. Catherine Skinner from Yale University, Dr. John Rakovan at Miami University in Ohio, Dr. Richard Riman at Rutgers University.

  18. Extraction of local coordination structure in a low-concentration uranyl system by XANES.

    PubMed

    Zhang, Linjuan; Zhou, Jing; Zhang, Jianyong; Su, Jing; Zhang, Shuo; Chen, Ning; Jia, Yunpeng; Li, Jiong; Wang, Yu; Wang, Jian Qiang

    2016-05-01

    Obtaining structural information of uranyl species at an atomic/molecular scale is a critical step to control and predict their physical and chemical properties. To obtain such information, experimental and theoretical L3-edge X-ray absorption near-edge structure (XANES) spectra of uranium were studied systematically for uranyl complexes. It was demonstrated that the bond lengths (R) in the uranyl species and relative energy positions (ΔE) of the XANES were determined as follows: ΔE1 = 168.3/R(U-Oax)(2) - 38.5 (for the axial plane) and ΔE2 = 428.4/R(U-Oeq)(2) - 37.1 (for the equatorial plane). These formulae could be used to directly extract the distances between the uranium absorber and oxygen ligand atoms in the axial and equatorial planes of uranyl ions based on the U L3-edge XANES experimental data. In addition, the relative weights were estimated for each configuration derived from the water molecule and nitrate ligand based on the obtained average equatorial coordination bond lengths in a series of uranyl nitrate complexes with progressively varied nitrate concentrations. Results obtained from XANES analysis were identical to that from extended X-ray absorption fine-structure (EXAFS) analysis. XANES analysis is applicable to ubiquitous uranyl-ligand complexes, such as the uranyl-carbonate complex. Most importantly, the XANES research method could be extended to low-concentration uranyl systems, as indicated by the results of the uranyl-amidoximate complex (∼40 p.p.m. uranium). Quantitative XANES analysis, a reliable and straightforward method, provides a simplified approach applied to the structural chemistry of actinides. PMID:27140156

  19. Effects of strain relaxation in Pr0.67Sr0.33MnO3 films probed by polarization dependent X-ray absorption near edge structure

    DOE PAGESBeta

    zhang, Bangmin; Chen, Jingsheng; Venkatesan, T.; Sun, Cheng -Jun; Heald, Steve M.; Chow, Gan Moog; Yang, Ping; Chi, Xiao; Lin, Weinan

    2016-01-28

    In this study, the Mn K edge X-ray absorption near edge structure (XANES) of Pr0.67Sr0.33MnO3 films with different thicknesses on (001) LaAlO3 substrate were measured, and the effects of strain relaxation on film properties were investigated. The films experienced in-plane compressive strain and out-of-plane tensile strain. Strain relaxation evolved with the film thickness. In the polarization dependent XANES measurements, the in-plane (parallel) and out-of-plane (perpendicular) XANES spectrocopies were anisotropic with different absorption energy Er. The resonance energy Er along two directions shifted towards each other with increasing film thickness. Based on the X-ray diffraction results, it was suggested that themore » strain relaxation weakened the difference of the local environment and probability of electronic charge transfer (between Mn 3d and O 2p orbitals) along the in-plane and out-of-plane directions, which was responsible for the change of Er. XANES is a useful tool to probe the electronic structures, of which the effects on magnetic properties with the strain relaxation was also been studied.« less

  20. Temperature dependent electronic structure of Pr{sub 0.67}Sr{sub 0.33}MnO{sub 3} film probed by X-ray absorption near edge structure

    SciTech Connect

    Zhang, Bangmin; Sun, Cheng-Jun E-mail: msecgm@nus.edu.sg; Heald, Steve M.; Chen, Jing-Sheng; Moog Chow, Gan E-mail: msecgm@nus.edu.sg; Venkatesan, T.

    2014-05-07

    The Mn K edge X-ray absorption near edge structures (XANES) of Pr{sub 0.67}Sr{sub 0.33}MnO{sub 3} film (100 nm) on (001) LaAlO{sub 3} substrate was measured at different temperatures to probe the MnO{sub 6} octahedron distortion and corresponding electronic structure. The absorption of high temperature paramagnetic-insulator phase differed from that of the low temperature ferromagnetic-metal phase. The temperature-dependent absorption intensity of Mn K edge XANES was correlated with the relaxation of distorted MnO{sub 6} octahedron, which changed the crystal field acting on the Mn site and the related electronic structure and properties. At low temperature, the splitting of Mn majority e{sub g} orbitals decreased and the density of states above the Fermi level increased in the relaxed MnO{sub 6} octahedron, as reflected by a wider separation between two sub-peaks in the pre-edge XANES spectra.

  1. Local structure of Ge quantum dots determined by combined numerical analysis of EXAFS and XANES data.

    PubMed

    Zhang, Yuanpeng; Ersoy, Osman; Karatutlu, Ali; Little, William; Sapelkin, Andrei

    2016-01-01

    The sensitivity of X-ray absorption near-edge structure (XANES) to the local symmetry has been investigated in small (∼4 nm) matrix-free Ge quantum dots. The FDMNES package was used to calculate the theoretical XANES spectra that were compared with the experimental data of as-prepared and annealed nanoparticles. It was found that XANES data for an as-prepared sample can only be adequately described if the second coordination shell of the diamond-type structural model is included in the FDMNES calculations. This is in contrast to the extended X-ray absorption fine-structure data that show only the first-shell signal. These results suggest that, despite the high degree of disorder and a large surface-to-volume ratio, as-prepared small Ge quantum dots retain the diamond-type symmetry beyond the first shell. Furthermore, we utilized this sensitivity of XANES to the local symmetry to study annealed Ge quantum dots and found evidence for significant structural distortion which we attribute to the existence of surface disorder in the annealed oxygen-free Ge quantum dots. PMID:26698071

  2. Chemical forms of sulfur in geological and archeological asphaltenes from Middle East, France, and Spain determined by sulfur K- and L-edge X-ray absorption near-edge structure spectroscopy

    NASA Astrophysics Data System (ADS)

    Sarret, Géraldine; Connan, Jacques; Kasrai, Masoud; Bancroft, G. Michael; Charrié-Duhaut, Armelle; Lemoine, Sylvie; Adam, Pierre; Albrecht, Pierre; Eybert-Bérard, Laurent

    1999-11-01

    Asphaltene samples extracted from archeological and geological bitumens from the Middle East, France, and Spain were studied by sulfur K- and L-edge X-ray absorption near-edge structure (XANES) spectroscopy in combination with isotopic analyses (δ 13C and δD). Within each series, the samples were genetically related by their δ 13C values. The gross and elemental composition and the δD values were used to characterize the weathering state of the samples. Sulfur K- and L-edge XANES results show that in all the samples, dibenzothiophenes are the dominant forms of sulfur. In the least oxidized asphaltenes, minor species include disulfides, alkyl and aryl sulfides, and sulfoxides. With increasing alteration the proportion of oxidized sulfur (sulfoxides, sulfones, sulfonates and sulfates) increases, whereas the disulfide and sulfide content decreases. This evolution is observed in all the series, regardless of the origin of the asphaltenes. This work illustrates the advantages of XANES spectroscopy as a selective probe for determining sulfur speciation in natural samples. It also shows that S K- and L-edge XANES spectroscopy are complementary for identifying the oxidized and reduced forms of sulfur, respectively.

  3. X-ray absorption near-edge structure study on the configuration of Cu 2+ /histidine complexes at different pH values

    NASA Astrophysics Data System (ADS)

    Mei-Juan, Yu; Yu, Wang; Wei, Xu

    2016-04-01

    The local configurations around metal ions in metalloproteins are of great significance for understanding their biological functions. Cu2+/histidine (His) is a typical complex existing in many metalloproteins and plays an important role in lots of physiological functions. The three-dimensional (3D) structural configurations of Cu2+/His complexes at different pH values (2.5, 6.5, and 8.5) are quantitatively determined by x-ray absorption near-edge structure (XANES). Generally Cu2+/His complex keeps an octahedral configuration consisting of oxygen atoms from water molecules and oxygen or nitrogen atoms from histidine molecules coordinated around Cu2+. It is proved in this work that the oxygen atoms from water molecules, when increasing the pH value from acid to basic value, are gradually substituted by the Ocarboxyl, Nam, and Nim from hisitidine molecules. Furthermore, the symmetries of Cu2+/His complexes at pH 6.5 and pH 8.5 are found to be lower than at pH 2.5. Project supported by the National Natural Science Foundation of China (Grant No. 11205186).

  4. Understanding conversion mechanism of NiO anodic materials for Li-ion battery using in situ X-ray absorption near edge structure spectroscopy

    NASA Astrophysics Data System (ADS)

    Jang, Jue-Hyuk; Chae, Byung-Mok; Oh, Hyun-Jung; Lee, Yong-Kul

    2016-02-01

    Nano-scaled NiO particles (nano-NiO) are prepared by a ligand stabilization method and compared with micron-sized NiO particles (micro-NiO) as anodic material of Li-ion battery. The structural and physical properties are characterized by N2 physisorption, transmission electron microscopy, and X-ray diffraction. The nano-NiO shows uniform spheres with an average particle size of 9 nm with high and stable discharge capacity of 637 mAh g-1, while the micro-NiO forms irregularly shaped particles with an average particle size of 750 nm with low capacity of 431 mAh g-1 at 0.5C. In situ X-ray absorption near edge structure (XANES) analysis reveals that the capacity and reversibility of the NiO anode is highly affected by the particle size of the NiO. The micro-NiO exhibits a low capacity with absence of phase transformation upon the discharge/charge cycles. In contrast, the nano-NiO exhibits a high capacity with reversible phase transformation between NiO and Ni metal upon the cycle test.

  5. Three-dimensional Fe speciation of an inclusion cloud within an ultradeep diamond by confocal μ-X-ray absorption near edge structure: evidence for late stage overprint.

    PubMed

    Silversmit, Geert; Vekemans, Bart; Appel, Karen; Schmitz, Sylvia; Schoonjans, Tom; Brenker, Frank E; Kaminsky, Felix; Vincze, Laszlo

    2011-08-15

    A stream of 1-20 μm sized mineral inclusions having the negative crystal shape of its host within an "ultra-deep" diamond from Rio Soriso (Juina area, Mato Grosso State, Brazil) has been studied with confocal μ-X-ray absorption near edge structureXANES) at the Fe K and Mn K edges. This technique allows the three-dimensional nondestructive speciation of the Fe and Mn containing minerals within the inclusion cloud. The observed Fe-rich inclusions were identified to be ferropericlase (Fe,Mg)O, hematite and a mixture of these two minerals. Confocal μ-X-ray fluorescence (μXRF) further showed that Ca-rich inclusions were present as well, which are spatially separated from or in close contact with the Fe-rich inclusions. The inclusions are aligned along a plane, which most likely represents a primary growth zone. In the close vicinity of the inclusions, carbon coated planar features are visible. The three-dimensional distribution indicates a likely fluid overprint along an open crack. Our results imply that an imposed negative diamond shape of an inclusion alone does not exclude epigenetic formation or intense late stage overprint. PMID:21707095

  6. Sulfur species in source rock bitumen before and after hydrous pyrolysis determined by X-ray absorption near-edge structure

    USGS Publications Warehouse

    Bolin, Trudy B.; Birdwell, Justin E.; Lewan, Michael; Hill, Ronald J.; Grayson, Michael B.; Mitra-Kirtley, Sudipa; Bake, Kyle D.; Craddock, Paul R.; Abdallah, Wael; Pomerantz, Andrew E.

    2016-01-01

    The sulfur speciation of source rock bitumen (chloroform-extractable organic matter in sedimentary rocks) was examined using sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy for a suite of 11 source rocks from around the world. Sulfur speciation was determined for both the native bitumen in thermally immature rocks and the bitumen produced by thermal maturation of kerogen via hydrous pyrolysis (360 °C for 72 h) and retained within the rock matrix. In this study, the immature bitumens had higher sulfur concentrations than those extracted from samples after hydrous pyrolysis. In addition, dramatic and systematic evolution of the bitumen sulfur moiety distributions following artificial thermal maturation was observed consistently for all samples. Specifically, sulfoxide sulfur (sulfur double bonded to oxygen) is abundant in all immature bitumen samples but decreases substantially following hydrous pyrolysis. The loss in sulfoxide sulfur is associated with a relative increase in the fraction of thiophene sulfur (sulfur bonded to aromatic carbon) to the extent that thiophene is the dominant sulfur form in all post-pyrolysis bitumen samples. This suggests that sulfur moiety distributions might be used for estimating thermal maturity in source rocks based on the character of the extractable organic matter.

  7. Full-Field Calcium K-Edge X-ray Absorption Near-Edge Structure Spectroscopy on Cortical Bone at the Micron-Scale: Polarization Effects Reveal Mineral Orientation.

    PubMed

    Hesse, Bernhard; Salome, Murielle; Castillo-Michel, Hiram; Cotte, Marine; Fayard, Barbara; Sahle, Christoph J; De Nolf, Wout; Hradilova, Jana; Masic, Admir; Kanngießer, Birgit; Bohner, Marc; Varga, Peter; Raum, Kay; Schrof, Susanne

    2016-04-01

    Here, we show results on X-ray absorption near edge structure spectroscopy in both transmission and X-ray fluorescence full-field mode (FF-XANES) at the calcium K-edge on human bone tissue in healthy and diseased conditions and for different tissue maturation stages. We observe that the dominating spectral differences originating from different tissue regions, which are well pronounced in the white line and postedge structures are associated with polarization effects. These polarization effects dominate the spectral variance and must be well understood and modeled before analyzing the very subtle spectral variations related to the bone tissue variations itself. However, these modulations in the fine structure of the spectra can potentially be of high interest to quantify orientations of the apatite crystals in highly structured tissue matrices such as bone. Due to the extremely short wavelengths of X-rays, FF-XANES overcomes the limited spatial resolution of other optical and spectroscopic techniques exploiting visible light. Since the field of view in FF-XANES is rather large the acquisition times for analyzing the same region are short compared to, for example, X-ray diffraction techniques. Our results on the angular absorption dependence were verified by both site-matched polarized Raman spectroscopy, which has been shown to be sensitive to the orientation of bone building blocks and by mathematical simulations of the angular absorbance dependence. As an outlook we further demonstrate the polarization based assessment of calcium-containing crystal orientation and specification of calcium in a beta-tricalcium phosphate (β-Ca3(PO4)2 scaffold implanted into ovine bone. Regarding the use of XANES to assess chemical properties of Ca in human bone tissue our data suggest that neither the anatomical site (tibia vs jaw) nor pathology (healthy vs necrotic jaw bone tissue) affected the averaged spectral shape of the XANES spectra. PMID:26959687

  8. X-ray absorption near-edge structures of LiMn2O4 and LiNi0.5Mn1.5O4 spinel oxides for lithium-ion batteries: the first-principles calculation study.

    PubMed

    Okumura, Toyoki; Yamaguchi, Yoichi; Kobayashi, Hironori

    2016-07-21

    Experimental Mn and Ni K-edge X-ray absorption near-edge structure (XANES) spectra were well reproduced for 5 V-class LixNi0.5Mn1.5O4 spinels as well as 4 V-class LixMn2O4 spinels using density functional theory. Local environmental changes around the Mn or Ni centres due to differences in the locations of Li ions and/or phase transitions in the spinel oxides were found to be very important contributors to the XANES shapes, in addition to the valence states of the metal ions. PMID:27333155

  9. Determining Orientational Structure of Diamondoid Thiols Attached to Silver Using Near Edge X-ray Absorption Fine Structure Spectroscopy

    SciTech Connect

    Willey, T M; Lee, J I; Fabbri, J D; Wang, D; Nielsen, M; Randel, J C; Schreiner, P R; Fokin, A A; Tkachenko, B A; Fokina, N A; Dahl, J P; Carlson, R K; Terminello, L J; Melosh, N A; van Buuren, T

    2008-10-07

    Near-edge x-ray absorption fine structure spectroscopy (NEXAFS) is a powerful tool for determination of molecular orientation in self-assembled monolayers and other surface-attached molecules. A general framework for using NEXAFS to simultaneously determine molecular tilt and twist of rigid molecules attached to surfaces is presented. This framework is applied to self-assembled monolayers of higher diamondoid, hydrocarbon molecules with cubic-diamond-cage structures. Diamondoid monolayers chemisorbed on metal substrates are known to exhibit interesting electronic and surface properties. This work compares molecular orientation in monolayers prepared on silver substrates using two different thiol positional isomers of [121]tetramantane, and thiols derived from two different pentamantane structural isomers, [1212]pentamantane and [1(2,3)4]pentamantane. The observed differences in monolayer structure demonstrate the utility and limitations of NEXAFS spectroscopy and the framework. The results also demonstrate the ability to control diamondoid assembly, in particular the molecular orientational structure, providing a flexible platform for the modification of surface properties with this exciting new class of nanodiamond materials.

  10. Electron energy-loss near-edge structures of 3d transition metal oxides recorded at high-energy resolution.

    PubMed

    Mitterbauer, C; Kothleitner, G; Grogger, W; Zandbergen, H; Freitag, B; Tiemeijer, P; Hofer, F

    2003-09-01

    Near-edge fine structures of the metal L(2,3) and O K-edges in transition metal-oxides have been studied with a transmission electron microscope equipped with a monochromator and a high-resolution imaging filter. This system enables the recording of EELS spectra with an energy resolution of 0.1eV thus providing new near-edge fine structure details which could not be observed previously by EELS in conventional TEM instruments. EELS-spectra from well-defined oxides like titanium oxide (TiO(2)), vanadium oxide (V(2)O(5)), chromium oxide (Cr(2)O(3)), iron oxide (Fe(2)O(3)), cobalt oxide (CoO) and nickel oxide (NiO) have been measured with the new system. These spectra are compared with EELS data obtained from a conventional microscope and the main spectral features are interpreted. Additionally, the use of monochromised TEMs is discussed in view of the natural line widths of K and L(2,3) edges. PMID:12871809

  11. Neutralization of calcite in mineral aerosols by acidic sullur species collected in China and Japan studied by ca K-edge X-ray absorption near-edge structure.

    PubMed

    Takahashi, Yoshio; Miyoshi, Takuro; Higashi, Masayuki; Kamioka, Hikari; Kanai, Yutaka

    2009-09-01

    Calcium species in mineral aerosols collected simultaneously in Aksu (near the Taklimakan Desert), Qingdao (eastern China), and Tsukuba (Japan) during dust and nondust periods were determined using Ca K-edge X-ray absorption near-edge structure (XANES). From the fitting of XANES spectra, it was found that (i) calcite and gypsum were the main Ca species in the aerosol samples, and (ii) the gypsum fraction versus total Ca minerals [Gyp]/[Ca2+]t increased progressively in the order Aksu < Qingdao < Tsukuba. Surface-sensitive XANES in the conversion electron yield mode (CEY) showed that the gypsum is formed selectively at the surface of mineral aerosols for all the samples except for that taken in Aksu during the dust period. The decrease of the [Gyp]/[Ca2+]t ratio with an increase in particle size showed that the neutralization effect proceeds from the particle surface. For the Aksu sample in the dust period, however, (i) the [Gyp]/[Ca2+]t ratios obtained by XANES measured in the fluorescence (FL; regarded as bulk analysis) and CEY modes were similar and (ii) size dependence was not found, showing that neutralization is not important for the sample because of the large supply of mineral aerosol with little neutralization effect in Aksu. It was also found that the pH of the aerosol and the ratio of (NH4)2SO4 to gypsum were positively and negatively correlated with the Ca (or calcite) content, respectively. The speciation of Ca by XANES revealed the neutralization processes of acidic sulfur species by calcite during the long-range transport of mineral aerosols. PMID:19764213

  12. Effects of strain relaxation in Pr0.67Sr0.33MnO3 films probed by polarization dependent X-ray absorption near edge structure

    PubMed Central

    Zhang, Bangmin; Chen, Jingsheng; Yang, Ping; Chi, Xiao; Lin, Weinan; Venkatesan, T.; Sun, Cheng-Jun; Heald, Steve M.; Chow, Gan Moog

    2016-01-01

    The Mn K edge X-ray absorption near edge structure (XANES) of Pr0.67Sr0.33MnO3 films with different thicknesses on (001) LaAlO3 substrate was measured, and the effects of strain relaxation on film properties were investigated. The films showed in-plane compressive and out-of-plane tensile strains. Strain relaxation occurred with increasing film thickness, affecting both lattice constant and MnO6 octahedral rotation. In polarization dependent XANES measurements using in-plane (parallel) and out-of-plane (perpendicular) geometries, the different values of absorption resonance energy Er confirmed the film anisotropy. The values of Er along these two directions shifted towards each other with increasing film thickness. Correlating with X-ray diffraction (XRD) results it is suggested that the strain relaxation decreased the local anisotropy and corresponding probability of electronic charge transfer between Mn 3d and O 2p orbitals along the in-plane and out-of-plane directions. The XANES results were used to explain the film-thickness dependent magnetic and transport properties. PMID:26818583

  13. New methodological approach for the vanadium K-edge X-ray absorption near-edge structure interpretation: application to the speciation of vanadium in oxide phases from steel slag.

    PubMed

    Chaurand, Perrine; Rose, Jérôme; Briois, Valérie; Salome, Murielle; Proux, Olivier; Nassif, Vivian; Olivi, Luca; Susini, Jean; Hazemann, Jean-Louis; Bottero, Jean-Yves

    2007-05-17

    This paper presents a comparison between several methods dedicated to the interpretation of V K-edge X-ray absorption near-edge structure (XANES) features. V K-edge XANES spectra of several V-bearing standard compounds were measured in an effort to evaluate advantages and limits of each method. The standard compounds include natural minerals and synthetic compounds containing vanadium at various oxidation state (from +3 to +5) and in different symmetry (octahedral, tetrahedral, and square pyramidal). Correlations between normalized pre-edge peak area and its centroid position have been identified as the most reliable method for determining quantitative and accurate redox and symmetry information for vanadium. This methodology has been previously developed for the Fe K edge. It is also well adapted for the V K edge and is less influenced by the standard choice than other methods. This methodology was applied on an "environmental sample," i.e., a well-crystallized leached steel slag containing vanadium as traces. Micro-XANES measurements allowed elucidating the microdistribution of vanadium speciation in leached steel slag. The vanadium exhibits an important evolution from the unaltered to the altered phases. Its oxidation state increases from +3 to +5 together with the decrease of its symmetry (from octahedral to tetrahedral). PMID:17429991

  14. Effects of strain relaxation in Pr0.67Sr0.33MnO3 films probed by polarization dependent X-ray absorption near edge structure.

    PubMed

    Zhang, Bangmin; Chen, Jingsheng; Yang, Ping; Chi, Xiao; Lin, Weinan; Venkatesan, T; Sun, Cheng-Jun; Heald, Steve M; Chow, Gan Moog

    2016-01-01

    The Mn K edge X-ray absorption near edge structure (XANES) of Pr0.67Sr0.33MnO3 films with different thicknesses on (001) LaAlO3 substrate was measured, and the effects of strain relaxation on film properties were investigated. The films showed in-plane compressive and out-of-plane tensile strains. Strain relaxation occurred with increasing film thickness, affecting both lattice constant and MnO6 octahedral rotation. In polarization dependent XANES measurements using in-plane (parallel) and out-of-plane (perpendicular) geometries, the different values of absorption resonance energy Er confirmed the film anisotropy. The values of Er along these two directions shifted towards each other with increasing film thickness. Correlating with X-ray diffraction (XRD) results it is suggested that the strain relaxation decreased the local anisotropy and corresponding probability of electronic charge transfer between Mn 3d and O 2p orbitals along the in-plane and out-of-plane directions. The XANES results were used to explain the film-thickness dependent magnetic and transport properties. PMID:26818583

  15. Sulfur 1s near-edge x-ray absorption fine structure (NEXAFS) of thiol and thioether compounds

    SciTech Connect

    Beyhan, Shirin; Urquhart, Stephen G.; Hu Yongfeng

    2011-06-28

    The speciation and quantification of sulfur species based on sulfur K-edge x-ray absorption spectroscopy is of wide interest, particularly for biological and petroleum science. These tasks require a firm understanding of the sulfur 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of relevant species. To this end, we have examined the gas phase sulfur 1s NEXAFS spectra of a group of simple thiol and thioether compounds. These high-resolution gas phase spectra are free of solid-state broadening, charging, and saturation effects common in the NEXAFS spectra of solids. These experimental data have been further analyzed with the aid of improved virtual orbital Hartree-Fock ab initio calculations. The experimental sulfur 1s NEXAFS spectra show fine features predicted by calculation, and the combination of experiment and calculation has been used to improve assignment of spectroscopic features relevant for the speciation and quantification of the sulfur compounds.

  16. Near Edge X-Ray Absorption Fine Structure Spectroscopy with X-Ray Free-Electron Lasers

    SciTech Connect

    Bernstein, D.P.; Acremann, Y.; Scherz, A.; Burkhardt, M.; Stohr, J.; Beye, M.; Schlotter, W.F.; Beeck, T.; Sorgenfrei, F.; Pietzsch, A.; Wurth, W.; Fohlisch, A.; /Hamburg U.

    2009-12-11

    We demonstrate the feasibility of Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy on solids by means of femtosecond soft x-ray pulses from a free-electron laser (FEL). Our experiments, carried out at the Free-Electron Laser at Hamburg (FLASH), used a special sample geometry, spectrographic energy dispersion, single shot position-sensitive detection and a data normalization procedure that eliminates the severe fluctuations of the incident intensity in space and photon energy. As an example we recorded the {sup 3}D{sub 1} N{sub 4,5}-edge absorption resonance of La{sup 3+}-ions in LaMnO{sub 3}. Our study opens the door for x-ray absorption measurements on future x-ray FEL facilities.

  17. Local environment of Mn dopant in ZnO by near-edge x-ray absorption fine structure analysis

    NASA Astrophysics Data System (ADS)

    Kunisu, Masahiro; Oba, Fumiyasu; Ikeno, Hidekazu; Tanaka, Isao; Yamamoto, Tomoyuki

    2005-03-01

    High-resolution near-edge x-ray absorption fine structure (NEXAFS) at MnK edge is employed to probe the local environment of Mn dopant in ZnO. First-principles supercell calculations are systematically made to obtain theoretical NEXAFS. Mn is found to substitute for Zn up to 5at. %Mn in polycrystalline samples sintered at 1623K in air. Presence of Mn3O4 is apparent for samples with higher Mn content. The NEXAFS does not change in the range of Mn concentration from 0.01 to 5at.%, indicating the absence of Mn precipitates. The results are confirmed by examining the polarization dependence of the NEXAFS for a 5at.%-doped ZnO thin film.

  18. Geometric Structure Determination of N694C Lipoxygenase: a Comparative Near-Edge X-Ray Absorption Spectroscopy And Extended X-Ray Absorption Fine Structure Study

    SciTech Connect

    Sarangi, R.; Hocking, R.K.; Neidig, M.L.; Benfatto, M.; Holman, T.R.; Solomon, E.I.; Hodgson, K.O.; Hedman, B.

    2009-05-27

    The mononuclear nonheme iron active site of N694C soybean lipoxygenase (sLO1) has been investigated in the resting ferrous form using a combination of Fe-K-pre-edge, near-edge (using the minuit X-ray absorption near-edge full multiple-scattering approach), and extended X-ray absorption fine structure (EXAFS) methods. The results indicate that the active site is six-coordinate (6C) with a large perturbation in the first-shell bond distances in comparison to the more ordered octahedral site in wild-type sLO1. Upon mutation of the asparigine to cystiene, the short Fe-O interaction with asparigine is replaced by a weak Fe-(H{sub 2}O), which leads to a distorted 6C site with an effective 5C ligand field. In addition, it is shown that near-edge multiple scattering analysis can give important three-dimensional structural information, which usually cannot be accessed using EXAFS analysis. It is further shown that, relative to EXAFS, near-edge analysis is more sensitive to partial coordination numbers and can be potentially used as a tool for structure determination in a mixture of chemical species.

  19. XANES spectra of metal phytate compounds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Metal speciation of phosphate and metal-phosphate interactions can be investigated by molecular-scale X-ray absorption near edge structure (XANES) spectroscopic analysis. Much of the effort, however, has been focused on inorganic P speciation (i. e. metal-orthophosphate interactions). Phytate (inosi...

  20. XANES and IR spectroscopy study of the electronic structure and chemical composition of porous silicon on n- and p-type substrates

    SciTech Connect

    Lenshin, A. S. Kashkarov, V. M.; Seredin, P. V.; Spivak, Yu. M.; Moshnikov, V. A.

    2011-09-15

    The differences in the electronic structure and composition of porous silicon samples obtained under identical conditions of electrochemical etching on the most commonly used n- and p-type substrates with different conductivities are demonstrated by X-ray absorption near-edge spectroscopy (XANES) and Fourier transform IR spectroscopy (FTIR) methods. It is shown that significantly higher oxidation and saturation with hydrogen is observed for the porous layer on n-type substrates.

  1. Near-edge X-ray absorption fine-structure spectroscopy of naphthalene diimide-thiophene co-polymers

    SciTech Connect

    Gann, Eliot; McNeill, Christopher R.; Szumilo, Monika; Sirringhaus, Henning; Sommer, Michael; Maniam, Subashani; Langford, Steven J.; Thomsen, Lars

    2014-04-28

    Near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy is an important tool for probing the structure of conjugated polymer films used in organic electronic devices. High-performance conjugated polymers are often donor-acceptor co-polymers which feature a repeat unit with multiple functional groups. To facilitate better application of NEXAFS spectroscopy to the study of such materials, improved understanding of the observed NEXAFS spectral features is required. In order to examine how the NEXAFS spectrum of a donor-acceptor co-polymer relates to the properties of the sub-units, a series of naphthalene diimide-thiophene-based co-polymers have been studied where the nature and length of the donor co-monomer has been systematically varied. The spectra of these materials are compared with that of a thiophene homopolymer and naphthalene diimide monomer enabling peak assignment and the influence of inter-unit electronic coupling to be assessed. We find that while it is possible to attribute peaks within the π* manifold as arising primarily due to the naphthalene diimide or thiophene sub-units, very similar dichroism of these peaks is observed indicating that it may not be possible to separately probe the molecular orientation of the separate sub-units with carbon K-edge NEXAFS spectroscopy.

  2. O K-energy loss near-edge structure change induced by tantalum impurity in monoclinic hafnium oxide

    SciTech Connect

    Yang, Mino; Baik, Hionsuck; Ivanovskaya, Viktoria; Colliex, Christian; Benayad, Anass

    2011-03-01

    The present paper reports the energy loss near-edge structure (ELNES) study of monoclinic HfO{sub 2} (m-HfO{sub 2}) and tantalum doped m-HfO{sub 2} (Ta{sub 0.1}Hf{sub 0.9}O{sub 2}) thin films prepared by radio frequency magnetron co-sputtering method. A change in the O K-ELNES spectra was observed as the amount of dopant increases. In order to precise the common features and the differences as a function of Ta defect nature (substitutional or interstitial) in HfO{sub 2}, the O K-ELNES were commented with respect to density functional theory calculations implemented in Vienna ab initio simulation package code. The calculated Ta doped HfO{sub 2} band structure showed that substitutional tantalum is the dominant defect and the spectral differences between doped and non-doped HfO{sub 2} are mainly originated from the change in the local cation distribution around the oxygen atoms.

  3. Parameters Influencing Sulfur Speciation in Environmental Samples Using Sulfur K-Edge X-Ray Absorption Near-Edge Structure

    PubMed Central

    Pongpiachan, Siwatt; Thumanu, Kanjana; Kositanont, Charnwit; Schwarzer, Klaus; Prietzel, Jörg; Hirunyatrakul, Phoosak; Kittikoon, Itthipon

    2012-01-01

    This paper aims to enhance the credibility of applying the sulfur K-edge XANES spectroscopy as an innovative “fingerprint” for characterizing environmental samples. The sensitivities of sulfur K-edge XANES spectra of ten sulfur compound standards detected by two different detectors, namely, Lytle detector (LyD) and Germanium detector (GeD), were studied and compared. Further investigation on “self-absorption” effect revealed that the maximum sensitivities of sulfur K-edge XANES spectra were achieved when diluting sulfur compound standards with boron nitride (BN) at the mixing ratio of 0.1%. The “particle-size” effect on sulfur K-edge XANES spectrum sensitivities was examined by comparing signal-to-noise ratios of total suspended particles (TSP) and particulate matter of less than 10 millionths of a meter (PM10) collected at three major cities of Thailand. The analytical results have demonstrated that the signal-to-noise ratios of sulfur K-edge XANES spectra were positively correlated with sulfate content in aerosols and negatively connected with particle sizes. The combination of hierarchical cluster analysis (HCA) and principal component analysis (PCA) has proved that sulfur K-edge XANES spectrum can be used to characterize German terrestrial soils and Andaman coastal sediments. In addition, this study highlighted the capability of sulfur K-edge XANES spectra as an innovative “fingerprint” to distinguish tsunami backwash deposits (TBD) from typical marine sediments (TMS). PMID:23193498

  4. Surface and in-depth characterization of lithium-ion battery cathodes at different cycle states using confocal micro-X-ray fluorescence-X-ray absorption near edge structure analysis

    NASA Astrophysics Data System (ADS)

    Menzel, Magnus; Schlifke, Annalena; Falk, Mareike; Janek, Jürgen; Fröba, Michael; Fittschen, Ursula Elisabeth Adriane

    2013-07-01

    The cathode material LiNi0.5Mn1.5O4 for lithium-ion batteries has been studied with confocal micro-X-ray fluorescence (CMXRF) combined with X-ray absorption near edge structure (XANES) at the Mn-K edge and the Ni-K edge. This technique allows for a non-destructive, spatially resolved (x, y and z) investigation of the oxidation states of surface areas and to some extent of deeper layers of the electrode. Until now CMXRF-XANES has been applied to a limited number of applications, mainly geo-science. Here, we introduce this technique to material science applications and show its performance to study a part of a working system. A novel mesoporous LiNi0.5Mn1.5O4 material was cycled (charged and discharged) to investigate the effects on the oxidation states at the cathode/electrolyte interface. With this approach the degradation of Mn3 + to Mn4 + only observable at the surface of the electrode could be directly shown. The spatially resolved non-destructive analysis provides knowledge helpful for further understanding of deterioration and the development of high voltage battery materials, because of its nondestructive nature it will be also suitable to monitor processes during battery cycling.

  5. Quantitative Evaluation of the Carbon Hybridization State by Near Edge X-ray Absorption Fine Structure Spectroscopy.

    PubMed

    Mangolini, Filippo; McClimon, J Brandon; Carpick, Robert W

    2016-03-01

    The characterization of the local bonding configuration of carbon in carbon-based materials is of paramount importance since the properties of such materials strongly depend on the distribution of carbon hybridization states, the local ordering, and the degree of hydrogenation. Carbon 1s near edge X-ray absorption fine structure (NEXAFS) spectroscopy is one of the most powerful techniques for gaining insights into the bonding configuration of near-surface carbon atoms. The common methodology for quantitatively evaluating the carbon hybridization state using C 1s NEXAFS measurements, which is based on the analysis of the sample of interest and of a highly ordered pyrolytic graphite (HOPG) reference sample, was reviewed and critically assessed, noting that inconsistencies are found in the literature in applying this method. A theoretical rationale for the specific experimental conditions to be used for the acquisition of HOPG reference spectra is presented together with the potential sources of uncertainty and errors in the correctly computed fraction of sp(2)-bonded carbon. This provides a specific method for analyzing the distribution of carbon hybridization state using NEXAFS spectroscopy. As an illustrative example, a hydrogenated amorphous carbon film was analyzed using this method and showed good agreement with X-ray photoelectron spectroscopy (which is surface sensitive). Furthermore, the results were consistent with analysis from Raman spectroscopy (which is not surface sensitive), indicating the absence of a structurally different near-surface region in this particular thin film material. The present work can assist surface scientists in the analysis of NEXAFS spectra for the accurate characterization of the structure of carbon-based materials. PMID:26814796

  6. Structure analyses using X-ray photoelectron spectroscopy and X-ray absorption near edge structure for amorphous MS3 (M: Ti, Mo) electrodes in all-solid-state lithium batteries

    NASA Astrophysics Data System (ADS)

    Matsuyama, Takuya; Deguchi, Minako; Mitsuhara, Kei; Ohta, Toshiaki; Mori, Takuya; Orikasa, Yuki; Uchimoto, Yoshiharu; Kowada, Yoshiyuki; Hayashi, Akitoshi; Tatsumisago, Masahiro

    2016-05-01

    Electronic structure changes of sulfurs in amorphous TiS3 and MoS3 for positive electrodes of all-solid-state lithium batteries are examined by X-ray photoelectron spectroscopy (XPS) and the X-ray absorption near edge structure (XANES). The all-solid-state cell with amorphous TiS3 electrode shows the reversible capacity of about 510 mAh g-1 for 10 cycles with sulfur-redox in amorphous TiS3 during charge-discharge process. On the other hand, the cell with amorphous MoS3 shows the 1st reversible capacity of about 720 mAh g-1. The obtained capacity is based on the redox of both sulfur and molybdenum in amorphous MoS3. The irreversible capacity of about 50 mAh g-1 is observed at the 1st cycle, which is attributed to the irreversible electronic structure change of sulfur during the 1st cycle. The electronic structure of sulfur in amorphous MoS3 after the 10th charge is similar to that after the 1st charge. Therefore, the all-solid-state cell with amorphous MoS3 electrode shows relatively good cyclability after the 1st cycle.

  7. Adsorption of dopamine on rutile TiO2 (110): a photoemission and near-edge X-ray absorption fine structure study.

    PubMed

    Jackman, Mark J; Syres, Karen L; Cant, David J H; Hardman, Samantha J O; Thomas, Andrew G

    2014-07-29

    Synchrotron radiation photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) techniques have been used to study the adsorption of dopamine on a rutile TiO2 (110) single crystal. Photoemission results suggest that dopamine bonds through the oxygen molecules in a bidentate fashion. From the data, it is ambiguous whether the oxygens bond to the same 5-fold coordinated surface titanium atom or bridges across two, although based on the bonding of pyrocatechol on rutile TiO2 (110), it is likely that the dopamine bridges two titanium atoms. Using the searchlight effect, the carbon K-edge near-edge X-ray absorption fine structure NEXAFS spectra recorded for dopamine on rutile TiO2 (110) show the phenyl ring to be oriented at 78° ± 5° from the surface and twisted 11 ± 10° relative to the (001) direction. PMID:25003716

  8. Electronic structure of individual hybrid colloid particles studied by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy in the X-ray microscope.

    PubMed

    Henzler, Katja; Guttmann, Peter; Lu, Yan; Polzer, Frank; Schneider, Gerd; Ballauff, Matthias

    2013-02-13

    The electronic structure of individual hybrid particles was studied by nanoscale near-edge X-ray absorption spectromicroscopy. The colloidal particles consist of a solid polystyrene core and a cross-linked poly-N-(isopropylacrylamide) shell with embedded crystalline titanium dioxide (TiO(2)) nanoparticles (d = 6 ± 3 nm). The TiO(2) particles are generated in the carrier network by a sol-gel process at room temperature. The hybrid particles were imaged with photon energy steps of 0.1 eV in their hydrated environment with a cryo transmission X-ray microscope (TXM) at the Ti L(2,3)-edge. By analyzing the image stacks, the obtained near-edge X-ray absorption fine structure (NEXAFS) spectra of our individual hybrid particles show clearly that our synthesis generates TiO(2) in the anastase phase. Additionally, our spectromicroscopy method permits the determination of the density distribution of TiO(2) in single carrier particles. Therefore, NEXAFS spectroscopy combined with TXM presents a unique method to get in-depth insight into the electronic structure of hybrid materials. PMID:23360082

  9. [Distribution and speciation of Pb in Arabidopsis thaliana shoot and rhizosphere soil by in situ synchrotron radiation micro X-ray fluorescence and X-ray absorption near edge structure].

    PubMed

    Shen, Ya-Ting

    2014-03-01

    In order to investigate plant reacting mechanism with heavy metal stress in organ and tissue level, synchrotron radiation micro X-ray fluorescence (micro-SRXRF) was used to determine element distribution characteristics of K, Ca, Mn, Fe, Cu, Zn, Pb in an Arabidopsis thaliana seedling grown in tailing dam soil taken from a lead-zinc mine exploration area. The results showed a regular distribution characters of K, Ca, Fe, Cu and Zn, while Pb appeared not only in root, but also in a leaf bud which was beyond previously understanding that Pb mainly appeared in plant root. Pb competed with Mn in the distribution of the whole seedling. Pb may cause the increase of oxidative stress in root and leaf bud, and restrict Mn absorption and utilization which explained the phenomenon of seedling death in this tailing damp soil. Speciation of Pb in Arabidopsis thaliana and tailing damp rhizosphere soil were also presented after using PbL3 micro X-ray absorption near edge structure (micro-XANES). By comparison of PbL3 XANES peak shape and peak position between standard samples and rhizosphere soil sample, it was demonstrated that the tailing damp soil was mainly formed by amorphous forms like PbO (64.2%), Pb (OH)2 (28.8%) and Pb3O4 (6.3%) rather than mineral or organic Pb speciations. The low plant bioavailability of Pb demonstrated a further research focusing on Pb absorption and speciation conversion is needed, especially the role of dissolve organic matter in soil which may enhance Pb bioavailability. PMID:25208420

  10. Study on the d state of platinum in Pt/SiO sub 2 and Na/Pt/SiO sub 2 catalysts under C double bond C hydrogenation conditions by X-ray absorption near-edge structure spectroscopy

    SciTech Connect

    Yoshitake, Hideaki; Iwasawa, Yasuhiro )

    1991-09-19

    The change in the d-electron density of platinum during D{sub 2} + CH{sub 2}{double bond}CHX reactions on Pt/SiO{sub 2} and Na/Pt/SiO{sub 2} catalysts and its influence on the catalysis were studied by X-ray absorption near-edge structure (XANES) spectroscopy, kinetics and FT-IR. It was demonstrated from the change of the white lines in XANES spectra at Pt L{sub 2} and L{sub 3} edges that CH{sub 2}{double bond}CHX (X = H, CH{sub 3}, COCH{sub 3}, CF{sub 3}, and CN) is adsorbed on the Pt surface and extracts the electrons of the d state. Hence, the deuterogenation rate is reduced as the value of Hammett's {sigma}{sub P} increases. The linear free energy relationship between the reaction rate and {sigma}{sub P} was observed for the deuterogenation of CH{sub 2}{double bond}CHX. The rate of ethene deuterogenation was promoted by Na{sub 2}O addition. The electron density of unoccupied d states of pt under vacuum decreased by Na{sub 2}O addition, indicating the electron donation from Na{sub 2}O addition. The electron density of unoccupied d states of Pt under vacuum decreased by Na{sub 2}O addition, indicating the electron donation from Na{sub 2}O addition. However, most of these additional electrons were observed to move to ethene under reaction conditions. The acceptor of the electrons was suggested by di-{sigma}-ethene by the shift of {upsilon}(C-H). The kinetic parameters are discussed in relation to the change in the d state of Pt as a function of {sigma}{sub P} and Na quantity.

  11. XANES: Solid state mineral analysis

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    Researchers in the field of mineral physics have become aware of new analytical techniques for studying the electronic structure of solids; one such technique is the X ray absorption fine structure (XFAS) method. In this technique the fine structure of the X ray K-edge, for example, can b e employed as a critical probe of t h e intricacies of a crystal structure (P. A. Lee, P. H. Citrin, P. Eisenberger, and B. M. Kincaid, Rev. Mod. Phys., 53, 799, 1981).A similar, related technique, X ray absorption near-edge spectroscopy (XANES), is a relatively unknown method of studying the electronic structure of solids. XANES is new, and due to its complex nature, data on all but very simple solids have not yet been applied rigorously. Among the first XANES results on minerals is the recent study reported by G. Knapp, B. Veal, H. Pan, and T. Klipper (Solid State Comm. 44, 1343, 1982) on perovskites, magnesiowustites, and other 3d oxides in the zircon and spinel groups. The interpretation of these results is still semiquantitative, being based on ground state and basic selection rule considerations. The results show, however, a strong correlation between near-edge spectra and crystal structure.

  12. A microsecond time resolved x-ray absorption near edge structure synchrotron study of phase transitions in Fe undergoing ramp heating at high pressure

    SciTech Connect

    Marini, C.; Mathon, O.; Pascarelli, S.; Occelli, F.; Torchio, R.; Recoules, V.; Loubeyre, P.

    2014-03-07

    We report a microsecond time-resolved x-ray absorption near edge structure study using synchrotron radiation to dynamically detect structural phase transitions in Fe undergoing rapid heating along a quasi-isochoric path. Within a few ms, we observed two structural phase transitions, which transform the ambient bcc phase of Fe into the fcc phase, and then into the liquid phase. This example illustrates the opportunities offered by energy dispersive x-ray absorption spectroscopy in the study of matter under extreme dynamic conditions. Advanced simulations are compared to these data.

  13. Quantitative investigation of two metallohydrolases by X-ray absorption spectroscopy near-edge spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhao, W.; Chu, W. S.; Yang, F. F.; Yu, M. J.; Chen, D. L.; Guo, X. Y.; Zhou, D. W.; Shi, N.; Marcelli, A.; Niu, L. W.; Teng, M. K.; Gong, W. M.; Benfatto, M.; Wu, Z. Y.

    2007-09-01

    The last several years have witnessed a tremendous increase in biological applications using X-ray absorption spectroscopy (BioXAS), thanks to continuous advancements in synchrotron radiation (SR) sources and detector technology. However, XAS applications in many biological systems have been limited by the intrinsic limitations of the Extended X-ray Absorption Fine Structure (EXAFS) technique e.g., the lack of sensitivity to bond angles. As a consequence, the application of the X-ray absorption near-edge structure (XANES) spectroscopy changed this scenario that is now continuously changing with the introduction of the first quantitative XANES packages such as Minut XANES (MXAN). Here we present and discuss the XANES code MXAN, a novel XANES-fitting package that allows a quantitative analysis of experimental data applied to Zn K-edge spectra of two metalloproteins: Leptospira interrogans Peptide deformylase ( LiPDF) and acutolysin-C, a representative of snake venom metalloproteinases (SVMPs) from Agkistrodon acutus venom. The analysis on these two metallohydrolases reveals that proteolytic activities are correlated to subtle conformation changes around the zinc ion. In particular, this quantitative study clarifies the occurrence of the LiPDF catalytic mechanism via a two-water-molecules model, whereas in the acutolysin-C we have observed a different proteolytic activity correlated to structural changes around the zinc ion induced by pH variations.

  14. Effect of heat treatment on the activity and stability of PtCo/C catalyst and application of in-situ X-ray absorption near edge structure for proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Lin, Rui; Zhao, Tiantian; Shang, Mingfeng; Wang, Jianqiang; Tang, Wenchao; Guterman, Vladimir E.; Ma, Jianxin

    2015-10-01

    For the purpose of reducing the cost and improving the performance of the proton exchange membrane fuel cell (PEMFC), some low-Pt or non-Pt catalysts have been studied in recent years. PtCo/C electrocatalysts are synthesized by a two-step reduction approach followed by the heat treatment. PtCo metal particles are uniformly dispersed on the surface of XC-72 carbon support, with a uniform particle size distribution. The PtCo/C catalyst after 400 °C heat treatment has the best electrochemical performance among the as-prepared catalysts, even superior to the commercial Pt/C catalyst. In the durability test, PtCo/C-400 also shows excellent stability with only 6.9% decline of electrochemical surface area (ECSA) after 1000 cyclic voltammetry (CV) cycles. In-situ X-ray absorption near edge structure (XANES) technique is conducted to explore the nanostructure change of Pt during the PEMFC operation. For PtCo/C catalyst, with the fuel cell operation potential decreasing from open circuit voltage (OCV) to 0.3 V, the Pt L3 white line intensity decreases continuously, indicating the decline of Pt 5d-vacancy due to the adsorption of oxygenated species.

  15. Near edge X-ray absorption fine structure spectroscopy as a tool to probe electronic and structural properties of thin organic films and liquids.

    PubMed

    Hähner, Georg

    2006-12-01

    Synchrotron-based spectroscopic techniques have contributed significantly to a better understanding of the properties of materials on the macroscopic and microscopic scale over the last decades. They can be applied to samples from a diversity of fields, including Biology, Life Sciences, Chemistry and Materials. One of these techniques is Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy, revealing electronic structure and information on the orientation of adsorbed molecules. The present article describes the basics of the technique and the progress it has made over the last three decades, and summarizes some of its more recent developments and applications. This tutorial review article should be accessible for novices to the field from Physics, Chemistry, Biology, Materials, and the Life Sciences, interested in thin organic films and liquid systems. PMID:17225886

  16. Vanadium speciation by XANES spectroscopy: a three-dimensional approach.

    PubMed

    Levina, Aviva; McLeod, Andrew I; Lay, Peter A

    2014-09-15

    A library of X-ray absorption near-edge structure (XANES) spectroscopic data for V(V), V(IV) and V(III) complexes with a broad range of biologically relevant ligand has been used to demonstrate that three-dimensional plots of key XANES parameters (pre-edge and edge energies; pre-edge and white line intensities) can be used for the prediction of V oxidation states and coordination numbers in biological or environmental matrices. The reliability of the technique has been demonstrated by re-analysis of the published XANES data for a V(V)-dependent bromoperoxidase. PMID:25088743

  17. Mechanism of the CO oxidation reaction on O-precovered Pt(111) surfaces studied with near-edge x-ray absorption fine structure spectroscopy

    SciTech Connect

    Nakai, I.; Kondoh, H.; Amemiya, K.; Nagasaka, M.; Shimada, T.; Yokota, R.; Nambu, A.; Ohta, T.

    2005-04-01

    The mechanism of CO oxidation reaction on oxygen-precovered Pt(111) surfaces has been studied by using time-resolved near-edge x-ray absorption fine structure spectroscopy. The whole reaction process is composed of two distinct paths: (1) a reaction of isolated oxygen atoms with adsorbed CO, and (2) a reaction of island-periphery oxygen atoms after the CO saturation. CO coadsorption plays a role to induce the dynamic change in spatial distribution of O atoms, which switches over the two reaction paths. These mechanisms were confirmed by kinetic Monte Carlo simulations. The effect of coadsorbed water in the reaction mechanism was also examined.

  18. C 1s Near Edge X-ray Absorption Fine Structure (NEXAFS) of substituted benzoic acids: a theoretical and experimental study

    SciTech Connect

    Baldea,I.; Schimmelpfennig, B.; Plaschke, M.; Rothe, J.; Schirmer, J.; Trofimov, A.; Fanghaenel, T.

    2007-01-01

    Ab initio calculations are performed to explain the discrete transitions in experimental C 1s-NEXAFS (near edge X-ray absorption fine structure) spectra of various benzoic acid derivates. Transition energies and oscillator strengths of the contributing C 1s-{pi}* excitations are computed using the ADC(2) (second-order algebraic-diagrammatic construction) method. This method is demonstrated to be well suited for the finite electronic systems represented by these simple organic acids. There is good agreement between experiment and theory reproducing all the relevant spectral features. Some transitions can only be assigned based on a theoretical foundation. Remaining discrepancies between experimental and computed spectra are discussed.

  19. How water molecules affect the catalytic activity of hydrolases - A XANES study of the local structures of peptide deformylase

    NASA Astrophysics Data System (ADS)

    Cui, Peixin; Wang, Yu; Chu, Wangsheng; Guo, Xiaoyun; Yang, Feifei; Yu, Meijuan; Zhao, Haifeng; Dong, Yuhui; Xie, Yaning; Gong, Weimin; Wu, Ziyu

    2014-12-01

    Peptide deformylase (PDF) is a prokaryotic enzyme that catalyzes the deformylation of nascent peptides generated during protein synthesis and water molecules play a key role in these hydrolases. Using X-ray absorption near edge spectroscopy (XANES) and ab initio calculations we accurately probe the local atomic environment of the metal ion binding in the active site of PDF at different pH values and with different metal ions. This new approach is an effective way to monitor existing correlations among functions and structural changes. We show for the first time that the enzymatic activity depends on pH values and metal ions via the bond length of the nearest coordinating water (Wat1) to the metal ion. Combining experimental and theoretical data we may claim that PDF exhibits an enhanced enzymatic activity only when the distance of the Wat1 molecule with the metal ion falls in the limited range from 2.15 to 2.55 Å.

  20. Effect of gas residence time on near-edge X-ray absorption fine structures of hydrogenated amorphous carbon films grown by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Jia, Lingyun; Sugiura, Hirotsugu; Kondo, Hiroki; Takeda, Keigo; Ishikawa, Kenji; Oda, Osamu; Sekine, Makoto; Hiramatsu, Mineo; Hori, Masaru

    2016-04-01

    In hydrogenated amorphous carbon films, deposited using a radical-injection plasma-enhanced chemical vapor deposition system, the chemical bonding structure was analyzed by near-edge X-ray absorption fine-structure spectroscopy. With a change in the residence times of source gases in a reactor, whereby total gas flow rates of H2/CH4 increased from 50 to 400 sccm, sp2-C fractions showed the minimum value at 150 sccm, while H concentration negligibly changed according to the results of secondary ion mass spectroscopy. On the other hand, widths of σ* C-C peaks increased with decreasing gas residence time, which indicates an increase in the fluctuation of bonding structures.

  1. Near-edge study of gold-substituted YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Ruckman, Mark W.; Hepp, Aloysius F.

    1991-01-01

    The valence of Cu and Au in YBa2Au0.3Cu2.7O7-delta was investigated using x-ray absorption near edge structure (XANES). X-ray and neutron diffraction studies indicate that Au goes on the Cu(1) site and Cu K-edge XANES shows that this has little effect on the oxidation state of the remaining copper. The Au L3 edge develops a white line feature whose position lies between that of trivalent gold oxide and monovalent potassium gold cyanide, and whose height relative to the edge step is smaller than in the two reference compounds. The appearance of the Au L3 edge suggests that fewer Au 3d states are involved in forming the Au-O bond in YBa2Au0.3Cu2.7O7-delta than in trivalent gold oxide.

  2. Near-edge study of gold-substituted YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Ruckman, Mark W.; Hepp, Aloysius F.

    1991-01-01

    The valence of Cu and Au in YBa2Au0.3Cu2.7O7-delta was investigated using X-ray absorption near edge structure (XANES). X-ray and neutron diffraction studies indicate that Au goes on the Cu(1) site and Cu K-edge XANES shows that this has little effect on the oxidation state of the remaining copper. The Au L3 edge develops a white line feature whose position lies between that of trivalent gold oxide and monovalent potassium gold cyanide, and whose height relative to the edge step is smaller than in the two reference compounds. The appearance of the Au L3 edge suggests that fewer Au 3d states are involved in forming the Au-O bond in YBa2Au0.3Cu2.7O7-delta than in trivalent gold oxide.

  3. Percolative superconductivity in La{sub 2}CuO{sub 4.06} by lattice granularity patterns with scanning micro x-ray absorption near edge structure

    SciTech Connect

    Poccia, Nicola; Chorro, Matthieu; Ricci, Alessandro; Xu, Wei; Marcelli, Augusto; Campi, Gaetano; Bianconi, Antonio

    2014-06-02

    The simplest cuprate superconductor La{sub 2}CuO{sub 4+y} with mobile oxygen interstitials exhibits a clear phase separation. It is known that oxygen interstitials enter into the rocksalt La{sub 2}O{sub 2+y} spacer layers forming oxygen interstitials rich puddles and poor puddles but only recently a bulk multiscale structural phase separation has been observed by using scanning micro X-ray diffraction. Here we get further information on their spatial distribution, using scanning La L{sub 3}-edge micro X-ray absorption near edge structure. Percolating networks of oxygen rich puddles are observed in different micrometer size portions of the crystals. Moreover, the complex surface resistivity shows two jumps associated to the onset of intra-puddle and inter-puddles percolative superconductivity. The similarity of oxygen doped La{sub 2}CuO{sub 4+y}, with the well established phase separation in iron selenide superconductors is also discussed.

  4. Composition analysis of a polymer electrolyte membrane fuel cell microporous layer using scanning transmission X-ray microscopy and near edge X-ray absorption fine structure analysis

    NASA Astrophysics Data System (ADS)

    George, Michael G.; Wang, Jian; Banerjee, Rupak; Bazylak, Aimy

    2016-03-01

    The novel application of scanning transmission X-ray microscopy (STXM) to the microporous layer (MPL) of a polymer electrolyte membrane fuel cell is investigated. A spatially resolved chemical component distribution map is obtained for the MPL of a commercially available SGL 25 BC sample. This is achieved with near edge X-ray absorption fine structure spectroscopic analysis. Prior to analysis the sample is embedded in non-reactive epoxy and ultra-microtomed to a thickness of 100 nm. Polytetrafluoroethylene (PTFE), carbon particle agglomerates, and supporting epoxy resin distributions are identified and reconstructed for a scanning area of 6 μm × 6 μm. It is observed that the spatial distribution of PTFE is strongly correlated to the carbon particle agglomerations. Additionally, agglomerate structures of PTFE are identified, possibly indicating the presence of a unique mesostructure in the MPL. STXM analysis is presented as a useful technique for the investigation of chemical species distributions in the MPL.

  5. Time-resolved near-edge x-ray absorption fine structure spectroscopy on photo-induced phase transitions using a tabletop soft-x-ray spectrometer

    NASA Astrophysics Data System (ADS)

    Grossmann, P.; Rajkovic, I.; Moré, R.; Norpoth, J.; Techert, S.; Jooss, C.; Mann, Klaus

    2012-05-01

    We present a table-top soft-x-ray spectrometer for the wavelength range λ = 1-5 nm based on a stable laser-driven x-ray source, making use of a gas-puff target. With this setup, optical light-pump/soft-x-ray probe near-edge x-ray absorption fine structure (NEXAFS) experiments with a temporal resolution of about 230 ps are feasible. Pump-probe NEXAFS measurements were carried out in the "water-window" region (2.28 nm-4.36 nm) on the manganite Pr0.7Ca0.3MnO3, investigating diminutive changes of the oxygen K edge that derive from an optically induced phase transition. The results show the practicability of the table-top soft-x-ray spectrometer on demanding investigations so far exclusively conducted at synchrotron radiation sources.

  6. Study of hard disk and slider surfaces using X-ray photoemission electron microscopy and near-edge X-ray absorption fine structure spectroscopy

    SciTech Connect

    Anders, S.; Stammler, T.; Bhatia, C.S.; Fong, W.; Chen, C.Y.; Bogy, D.B.

    1998-04-01

    X-ray Photo Emission Electron Microscopy (X-PEEM) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy were applied to study the properties of amorphous hard carbon overcoats on disks and sliders, and the properties of the lubricant. The modification of lubricants after performing thermal desorption studies was measured by NEXAFS, and the results are compared to the thermal desorption data. The study of lubricant degradation in wear tracks is described. Sliders were investigated before and after wear test, and the modification of the slider coating as well as the transfer of lubricant to the slider was studied. The studies show that the lubricant is altered chemically during the wear. Fluorine is removed and carboxyl groups are formed.

  7. Liquid crystal alignment on ion-beam-treated polyimide with a long alkyl side chain: near edge X-ray absorption fine structure spectroscopy analysis.

    PubMed

    Seo, Joo-Hong; Hwang, Soo Won; Song, Dong Han; Shin, Jae Hoon; Yoon, Tae-Hoon; Kim, Jae Chang; Yi, Mi Hye

    2009-02-19

    Liquid crystal alignment on ion-beam-treated polyimides with a long alkyl side chain was investigated using near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The long alkyl side chains and the asymmetric distribution and orientational order of the pi-bonds of the polyimide surface can be determined by analyzing the angular dependent resonance intensities of the NEXAFS measurements. Herein, we demonstrate that the pretilt angle of the LC cell made by our method decreases as more long alkyl side chains are destroyed. Additionally, the tilt direction of the LC molecules can be determined from the asymmetric distribution of pi-bonds of the polyimide created by the ion beam irradiation. PMID:19161281

  8. Particle Formation from Pulsed Laser Irradiation of SootAggregates studied with scanning mobility particle sizer, transmissionelectron microscope and near-edge x-ray absorption fine structure.

    SciTech Connect

    Michelsen, Hope A.; Tivanski, Alexei V.; Gilles, Mary K.; vanPoppel, Laura H.; Dansson, Mark A.; Buseck, Peter R.; Buseck, Peter R.

    2007-02-20

    We investigated the physical and chemical changes induced in soot aggregates exposed to laser radiation using a scanning mobility particle sizer, a transmission electron microscope, and a scanning transmission x-ray microscope to perform near-edge x-ray absorption fine structure spectroscopy. Laser-induced nanoparticle production was observed at fluences above 0.12 J/cm(2) at 532 nm and 0.22 J/cm(2) at 1064 nm. Our results indicate that new particle formation proceeds via (1) vaporization of small carbon clusters by thermal or photolytic mechanisms, followed by homogeneous nucleation, (2) heterogeneous nucleation of vaporized carbon clusters onto material ablated from primary particles, or (3) both processes.

  9. Investigation of Pb species in soils, celery and duckweed by synchrotron radiation X-ray absorption near-edge structure spectrometry

    NASA Astrophysics Data System (ADS)

    Luo, Liqiang; Shen, Yating; Liu, Jian; Zeng, Yuan

    2016-08-01

    The Pb species play a key role in its translocation in biogeochemical cycles. Soils, sediments and plants were collected from farmlands around Pb mines, and the Pb species in them was identified by X-ray absorption near-edge structure spectrometry. In soils, Pb5(PO4)3Cl and Pb3(PO4)2 were detected, and in sediments, Pb-fulvic acids (FAs) complex was identified. A Pb complex with FA fragments was also detected in celery samples. We found that (1) different Pb species were present in soils and sediments; (2) the Pb species in celery, which was grown in sediments, was different from the species present in duckweed, which grew in water; and (3) a Pb-FA-like compound was present in celery roots. The newly identified Pb species, the Pb-FA-like compound, may play a key role in Pb tolerance and translocation within plants.

  10. φXANES: In vivo imaging of metal-protein coordination environments

    PubMed Central

    James, Simon A.; Hare, Dominic J.; Jenkins, Nicole L.; de Jonge, Martin D.; Bush, Ashley I.; McColl, Gawain

    2016-01-01

    We have developed an X-ray absorption near edge structure spectroscopy method using fluorescence detection for visualizing in vivo coordination environments of metals in biological specimens. This approach, which we term fluorescence imaging XANESXANES), allows us to spatially depict metal-protein associations in a native, hydrated state whilst avoiding intrinsic chemical damage from radiation. This method was validated using iron-challenged Caenorhabditis elegans to observe marked alterations in redox environment. PMID:26861174

  11. φXANES: In vivo imaging of metal-protein coordination environments.

    PubMed

    James, Simon A; Hare, Dominic J; Jenkins, Nicole L; de Jonge, Martin D; Bush, Ashley I; McColl, Gawain

    2016-01-01

    We have developed an X-ray absorption near edge structure spectroscopy method using fluorescence detection for visualizing in vivo coordination environments of metals in biological specimens. This approach, which we term fluorescence imaging XANESXANES), allows us to spatially depict metal-protein associations in a native, hydrated state whilst avoiding intrinsic chemical damage from radiation. This method was validated using iron-challenged Caenorhabditis elegans to observe marked alterations in redox environment. PMID:26861174

  12. φXANES: In vivo imaging of metal-protein coordination environments

    NASA Astrophysics Data System (ADS)

    James, Simon A.; Hare, Dominic J.; Jenkins, Nicole L.; de Jonge, Martin D.; Bush, Ashley I.; McColl, Gawain

    2016-02-01

    We have developed an X-ray absorption near edge structure spectroscopy method using fluorescence detection for visualizing in vivo coordination environments of metals in biological specimens. This approach, which we term fluorescence imaging XANESXANES), allows us to spatially depict metal-protein associations in a native, hydrated state whilst avoiding intrinsic chemical damage from radiation. This method was validated using iron-challenged Caenorhabditis elegans to observe marked alterations in redox environment.

  13. Effect of metal ion on the structure and function of LiPDF: The study of the fine structure around the metal site using XANES

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Chu, Wangsheng; Yang, Feifei; Yu, Meijuan; Zhao, Haifeng; Gong, Weimin; Dong, Yuhui; Xie, Yaning; Wu, Ziyu

    2010-07-01

    We used X-ray absorption near edge structure (XANES) spectroscopy to investigate the metal-dependent enzymatic activity of the peptide deformylase from Leptospira interrogans ( LiPDF). Ab initio full multiple scattering calculations performed by MXAN are applied to obtain the local structure of the cobalt-containing LiPDF (Co- LiPDF) and zinc-containing LiPDF (Zn- LiPDF) around the metal sites in pH9.0 buffer solution. The result shows the cobalt-wat1 (the bond water molecule) distance of Co- LiPDF is 1.89 Å, much shorter than that of Zn- LiPDF, 2.50 Å. That is an essential factor for its low catalytic activity.

  14. Surface Structure and Chemical Switching of Thioctic Acid Adsorbed on Au(111) as Observed Using Near-Edge X-ray Absorption Fine Structure

    SciTech Connect

    Meulenberg, R W; van Buuren, T; Vance, A L; Terminello, L J; Willey, T M; Bostedt, C; Fadley, C S

    2004-01-06

    Thioctic acid (alpha-lipoic acid) is a molecule with a large disulfide-containing base, a short alkyl-chain with four CH{sub 2} units, and a carboxyl termination. Self-assembled monolayer (SAM) films of thioctic acid adsorbed on Au(111) have been investigated with near-edge x-ray absorption fine structure (NEXAFS) spectroscopy and x-ray photoelectron spectroscopy (XPS) to determine film quality, bonding and morphology. Using standard preparation protocols for SAMs, that is, dissolving thioctic acid in ethanol and exposing gold to the solution, results in poor films. These films are highly disordered, contain a mixture of carboxyl and carboxylate terminations, have more than monolayer coverage, and exhibit unbound disulfide. Conversely, forming films by dissolving 1 mmol thioctic acid into 5% acetic acid in ethanol (as previously reported with carboxyl-terminated alkyl-thiols) forms ordered monolayers with small amounts of unbound sulfur. NEXAFS indicates tilted over endgroups with the carboxyl group normal on average 38{sup o} from the surface normal. Slight dichroism in other features indicates alkyl chains statistically more upright than prostrate on the surface. Reflection-absorption Fourier transform infrared (RA-FTIR) spectra indicate hydrogen bonding between neighboring molecules. In such well-formed monolayers, a stark reorientation occurs upon deprotonation of the endgroup by rinsing in a KOH solution. The carboxylate plane normal is now about 66{sup o} from sample normal, a much more upright orientation. Data indicate this reorientation may also cause a more upright orientation to the alkyl portion of the molecules.

  15. The iron-site structure of [Fe]-hydrogenase and model systems: an X-ray absorption near edge spectroscopy study†‡

    PubMed Central

    Salomone-Stagni, Marco; Stellato, Francesco; Whaley, C. Matthew; Vogt, Sonja; Morante, Silvia; Shima, Seigo; Rauchfuss, Thomas B.; Meyer-Klaucke, Wolfram

    2012-01-01

    The [Fe]-hydrogenase is an ideal system for studying the electronic properties of the low spin iron site that is common to the catalytic centres of all hydrogenases. Because they have no auxiliary iron-sulfur clusters and possess a cofactor containing a single iron centre, the [Fe]-hydrogenases are well suited for spectroscopic analysis of those factors required for the activation of molecular hydrogen. Specifically, in this study we shed light on the electronic and molecular structure of the iron centre by XAS analysis of [Fe]-hydrogenase from Methanocaldococcus jannashii and five model complexes (Fe(ethanedithiolate)-(CO)2(PMe3)2, [K(18-crown-6)]2[Fe(CN)2(CO)3], K[Fe(CN)(CO)4], K3[Fe(iii)(CN)6], K4[Fe(ii)(CN)6]). The different electron donors have a strong influence on the iron absorption K-edge energy position, which is frequently used to determine the metal oxidation state. Our results demonstrate that the K-edges of Fe(ii) complexes, achieved with low-spin ferrous thiolates, are consistent with a ferrous centre in the [Fe]-hydrogenase from Methanocaldococcus jannashii. The metal geometry also strongly influences the XANES and thus the electronic structure. Using in silico simulation, we were able to reproduce the main features of the XANES spectra and describe the effects of individual donor contributions on the spectra. Thereby, we reveal the essential role of an unusual carbon donor coming from an acyl group of the cofactor in the determination of the electronic structure required for the activity of the enzyme. PMID:20221540

  16. Towards atomic resolution in sodium titanate nanotubes using near-edge X-ray-absorption fine-structure spectromicroscopy combined with multichannel multiple-scattering calculations

    PubMed Central

    Krüger, Peter; Lagos, Maureen J; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Ewels, Chris; Umek, Polona; Guttmann, Peter

    2012-01-01

    Summary Recent advances in near-edge X-ray-absorption fine-structure spectroscopy coupled with transmission X-ray microscopy (NEXAFS–TXM) allow large-area mapping investigations of individual nano-objects with spectral resolution up to E/ΔE = 104 and spatial resolution approaching 10 nm. While the state-of-the-art spatial resolution of X-ray microscopy is limited by nanostructuring process constrains of the objective zone plate, we show here that it is possible to overcome this through close coupling with high-level theoretical modelling. Taking the example of isolated bundles of hydrothermally prepared sodium titanate nanotubes ((Na,H)TiNTs) we are able to unravel the complex nanoscale structure from the NEXAFS–TXM data using multichannel multiple-scattering calculations, to the extent of being able to associate specific spectral features in the O K-edge and Ti L-edge with oxygen atoms in distinct sites within the lattice. These can even be distinguished from the contribution of different hydroxyl groups to the electronic structure of the (Na,H)TiNTs. PMID:23213642

  17. Towards atomic resolution in sodium titanate nanotubes using near-edge X-ray-absorption fine-structure spectromicroscopy combined with multichannel multiple-scattering calculations.

    PubMed

    Bittencourt, Carla; Krüger, Peter; Lagos, Maureen J; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Ewels, Chris; Umek, Polona; Guttmann, Peter

    2012-01-01

    Recent advances in near-edge X-ray-absorption fine-structure spectroscopy coupled with transmission X-ray microscopy (NEXAFS-TXM) allow large-area mapping investigations of individual nano-objects with spectral resolution up to E/ΔE = 10(4) and spatial resolution approaching 10 nm. While the state-of-the-art spatial resolution of X-ray microscopy is limited by nanostructuring process constrains of the objective zone plate, we show here that it is possible to overcome this through close coupling with high-level theoretical modelling. Taking the example of isolated bundles of hydrothermally prepared sodium titanate nanotubes ((Na,H)TiNTs) we are able to unravel the complex nanoscale structure from the NEXAFS-TXM data using multichannel multiple-scattering calculations, to the extent of being able to associate specific spectral features in the O K-edge and Ti L-edge with oxygen atoms in distinct sites within the lattice. These can even be distinguished from the contribution of different hydroxyl groups to the electronic structure of the (Na,H)TiNTs. PMID:23213642

  18. The Ti environment in natural hibonite: XANES spectroscopy and computer modelling

    NASA Astrophysics Data System (ADS)

    Kravtsova, Antonina N.; Soldatov, Alexander V.; Walker, Andrew M.; Berry, Andrew J.

    2016-05-01

    The local atomic structure around Ti in Ti-bearing hibonite (CaAl12O19) was studied using X-ray absorption near-edge structure (XANES) spectroscopy and computer modelling. Structural models of the direct substitution of Al by Ti3+, Al by Ti4+ charge balanced by the coupled substitution of Mg2+ for Al, and small Ti clusters were considered. The Ti K-XANES spectra of natural hibonite with different Ti concentration were recorded. Theoretical Ti K- XANES spectra for structural models of hibonite were calculated. It was shown that the theoretical Ti K-XANES spectra for a model with Ti at the five-coordinated M2 site are in agreement with the experimental XANES spectra of hibonite with low concentrations of Ti, while the theoretical spectra for a structural model of clustered Ti are in agreement with the experimental spectra of hibonite with higher Ti contents.

  19. Structural Properties and Charge Distribution of the Sodium Uranium, Neptunium, and Plutonium Ternary Oxides: A Combined X-ray Diffraction and XANES Study.

    PubMed

    Smith, Anna L; Martin, Philippe; Prieur, Damien; Scheinost, Andreas C; Raison, Philippe E; Cheetham, Anthony K; Konings, Rudy J M

    2016-02-15

    The charge distributions in α-Na2UO4, Na3NpO4, α-Na2NpO4, Na4NpO5, Na5NpO6, Na2PuO3, Na4PuO5, and Na5PuO6 are investigated in this work using X-ray absorption near-edge structure (XANES) spectroscopy at the U-L3, Np-L3, and Pu-L3 edges. In addition, a Rietveld refinement of monoclinic Na2PuO3, in space group C2/c, is reported for the first time, and the existence of the isostructural Na2NpO3 phase is revealed. In contrast to measurements in solution, the number of published XANES data for neptunium and plutonium solid phases with a valence state higher than IV is very limited. The present results cover a wide range of oxidation states, namely, IV to VII, and can serve as reference for future investigations. The sodium actinide series show a variety of local coordination geometries, and correlations between the shape of the XANES spectra and the local structural environments are discussed herein. PMID:26835549

  20. Near-Edge X-ray Absorption Fine Structure Studies of Electrospun Poly(dimethylsiloxane)/Poly (methyl methacrylate)/Multiwall Carbon Nanotube Composites

    PubMed Central

    Winter, A. Douglas; Larios, Eduardo; Alamgir, Faisal M.; Jaye, Cherno; Fischer, Daniel; Campo, Eva M.

    2014-01-01

    This work describes the near conduction band edge structure of electrospun mats of MWCNT-PDMS-PMMA by near edge X-Ray absorption fine structure (NEXAFS) spectroscopy. Effects of adding nanofillers of different sizes were addressed. Despite observed morphological variations and inhomogeneous carbon nanotube distribution, spun mats appeared homogeneous under NEXAFS analysis. Spectra revealed differences in emissions from glancing and normal spectra; which may evidence phase separation within the bulk of the micron-size fibers. Further, dichroic ratios show polymer chains did not align, even in the presence of nanofillers. Addition of nanofillers affected emissions in the C-H, C=O and C-C regimes, suggesting their involvement in interfacial matrix-carbon nanotube bonding. Spectral differences at glancing angles between pristine and composite mats suggest that geometric conformational configurations are taking place between polymeric chains and carbon nanotubes. These differences appear to be carbon nanotube-dimension dependent, and are promoted upon room temperature mixing and shear flow during electrospinning. CH-π bonding between polymer chains and graphitic walls, as well as H-bonds between impurities in the as-grown CNTs and polymer pendant groups are proposed bonding mechanisms promoting matrix conformation. PMID:24308286

  1. Identification of B-K near edge x-ray absorption fine structure peaks of boron nitride thin films prepared by sputtering deposition

    SciTech Connect

    Niibe, Masahito; Miyamoto, Kazuyoshi; Mitamura, Tohru; Mochiji, Kozo

    2010-09-15

    Four {pi}{sup *} resonance peaks were observed in the B-K near edge x-ray absorption fine structure spectra of boron nitride thin films prepared by magnetron sputtering. In the past, these peaks have been explained as the K-absorption of boron atoms, which are present in environment containing nitrogen vacancies, the number of which is 1-3 corresponding to the three peaks at higher photon energy. However, the authors found that there was a strong correlation between the intensities of these three peaks and that of O-K absorption after wide range scanning and simultaneous measurement of nitrogen and oxygen K-absorptions of the BN films. Therefore, the authors conclude that these three peaks at the higher energy side correspond to boron atoms bound to one-to-three oxygen atoms instead of three nitrogen atoms surrounding the boron atom in the h-BN structure. The result of the first-principles calculation with a simple cluster model supported the validity of this explanation.

  2. Low-temperature adsorption of H2S on Ni(001) studied by near-edge- and surface-extended-x-ray-absorption fine structure

    NASA Astrophysics Data System (ADS)

    McGrath, R.; MacDowell, A. A.; Hashizume, T.; Sette, F.; Citrin, P. H.

    1989-11-01

    The adsorption of H2S on Ni(001) has been studied with surface-extended x-ray-absorption fine structure and near-edge x-ray-absorption fine structure (NEXAFS) using the AT&T Bell Laboratories X15B beamline at the National Synchrotron Light Source. At 95 K and full saturation coverage, ~0.45 monolayer (ML) of S atoms in fourfold-hollow sites are produced, characteristic of room-temperature adsorption, accompanied by ~0.05 ML of oriented molecular H2S. Both these atomic and molecular chemisorbed species are buried under ~0.9 ML of disordered physisorbed H2S. No evidence for HS is found. Above 190 K the two molecular H2S phases desorb, leaving only dissociated S. These findings differ from previously reported interpretations of data obtained with high-resolution electron-energy-loss spectroscopy. They also exemplify the utility of NEXAFS for identifying and quantifying atomic and molecular surface species even when their difference involves only H and the two species coexist.

  3. Probing the Ordering of Semiconducting Fluorene-Thiophene Copolymer Surfaces on Rubbed Polyimide Substrates by Near-Edge X-ray Absorption Fine Structure

    SciTech Connect

    Pattison,L.; Hexemer, A.; Kramer, E.; Krishnan, S.; Petroff, P.; Fischer, D.

    2006-01-01

    The temperature-dependent alignment of semiconducting liquid crystalline fluorene-thiophene copolymer (F8T2) thin film surfaces was investigated using the near-edge X-ray absorption fine structure (NEXAFS) technique. Partial electron yield spectra were recorded over a range of temperatures in order to observe directly the surface orientation as the polymer is heated and cooled through glass, crystal, and liquid crystal phases. In addition, samples annealed under varying processing conditions and quenched to room temperature were analyzed. The NEXAFS data show that (a) in thin F8T2 films at all temperatures the polymer backbone lies in the plane of the substrate, (b) the fluorene and thiophene rings are rotated randomly about the molecular axis, (c) orientation of the polymer backbone can be controlled using a rubbed polyimide alignment layer as a template for liquid crystal orientation, and (d) under proper annealing conditions there is strong temperature-dependent alignment of the copolymer main-chain axis to the rubbing direction which extends from the polyimide/F8T2 interface all the way to the F8T2 surface. The surface alignment does not disappear after annealing at temperatures {approx}30 K above the bulk nematic to isotropic transition.

  4. Assignment of near-edge x-ray absorption fine structure spectra of metalloporphyrins by means of time-dependent density-functional calculations.

    PubMed

    Schmidt, Norman; Fink, Rainer; Hieringer, Wolfgang

    2010-08-01

    The C 1s and N 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of three prototype tetraphenyl porphyrin (TPP) molecules are discussed in the framework of a combined experimental and theoretical study. We employ time-dependent density-functional theory (TDDFT) to compute the NEXAFS spectra of the open- and closed-shell metalloporphyrins CoTPP and ZnTPP as well as the free-base 2HTPP in realistic nonplanar conformations. Using Becke's well-known half-and-half hybrid functional, the computed core excitation spectra are mostly in good agreement with the experimental data in the low-energy region below the appropriate ionization threshold. To make these calculations feasible, we apply a new, simple scheme based on TDDFT using a modified single-particle input spectrum. This scheme is very easy to implement in standard codes and allows one to compute core excitation spectra at a similar cost as ordinary UV/vis spectra even for larger molecules. We employ these calculations for a detailed assignment of the NEXAFS spectra including subtle shifts in certain peaks of the N 1s spectra, which depend on the central coordination of the TPP ligand. We furthermore assign the observed NEXAFS resonances to the individual molecular subunits of the investigated TPP molecules. PMID:20707545

  5. Assignment of near-edge x-ray absorption fine structure spectra of metalloporphyrins by means of time-dependent density-functional calculations

    NASA Astrophysics Data System (ADS)

    Schmidt, Norman; Fink, Rainer; Hieringer, Wolfgang

    2010-08-01

    The C 1s and N 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of three prototype tetraphenyl porphyrin (TPP) molecules are discussed in the framework of a combined experimental and theoretical study. We employ time-dependent density-functional theory (TDDFT) to compute the NEXAFS spectra of the open- and closed-shell metalloporphyrins CoTPP and ZnTPP as well as the free-base 2HTPP in realistic nonplanar conformations. Using Becke's well-known half-and-half hybrid functional, the computed core excitation spectra are mostly in good agreement with the experimental data in the low-energy region below the appropriate ionization threshold. To make these calculations feasible, we apply a new, simple scheme based on TDDFT using a modified single-particle input spectrum. This scheme is very easy to implement in standard codes and allows one to compute core excitation spectra at a similar cost as ordinary UV/vis spectra even for larger molecules. We employ these calculations for a detailed assignment of the NEXAFS spectra including subtle shifts in certain peaks of the N 1s spectra, which depend on the central coordination of the TPP ligand. We furthermore assign the observed NEXAFS resonances to the individual molecular subunits of the investigated TPP molecules.

  6. A laboratory-based hard x-ray monochromator for high-resolution x-ray emission spectroscopy and x-ray absorption near edge structure measurements

    SciTech Connect

    Seidler, G. T. Mortensen, D. R.; Remesnik, A. J.; Pacold, J. I.; Ball, N. A.; Barry, N.; Styczinski, M.; Hoidn, O. R.

    2014-11-15

    We report the development of a laboratory-based Rowland-circle monochromator that incorporates a low power x-ray (bremsstrahlung) tube source, a spherically bent crystal analyzer, and an energy-resolving solid-state detector. This relatively inexpensive, introductory level instrument achieves 1-eV energy resolution for photon energies of ∼5 keV to ∼10 keV while also demonstrating a net efficiency previously seen only in laboratory monochromators having much coarser energy resolution. Despite the use of only a compact, air-cooled 10 W x-ray tube, we find count rates for nonresonant x-ray emission spectroscopy comparable to those achieved at monochromatized spectroscopy beamlines at synchrotron light sources. For x-ray absorption near edge structure, the monochromatized flux is small (due to the use of a low-powered x-ray generator) but still useful for routine transmission-mode studies of concentrated samples. These results indicate that upgrading to a standard commercial high-power line-focused x-ray tube or rotating anode x-ray generator would result in monochromatized fluxes of order 10{sup 6}–10{sup 7} photons/s with no loss in energy resolution. This work establishes core technical capabilities for a rejuvenation of laboratory-based hard x-ray spectroscopies that could have special relevance for contemporary research on catalytic or electrical energy storage systems using transition-metal, lanthanide, or noble-metal active species.

  7. A laboratory-based hard x-ray monochromator for high-resolution x-ray emission spectroscopy and x-ray absorption near edge structure measurements.

    PubMed

    Seidler, G T; Mortensen, D R; Remesnik, A J; Pacold, J I; Ball, N A; Barry, N; Styczinski, M; Hoidn, O R

    2014-11-01

    We report the development of a laboratory-based Rowland-circle monochromator that incorporates a low power x-ray (bremsstrahlung) tube source, a spherically bent crystal analyzer, and an energy-resolving solid-state detector. This relatively inexpensive, introductory level instrument achieves 1-eV energy resolution for photon energies of ∼5 keV to ∼10 keV while also demonstrating a net efficiency previously seen only in laboratory monochromators having much coarser energy resolution. Despite the use of only a compact, air-cooled 10 W x-ray tube, we find count rates for nonresonant x-ray emission spectroscopy comparable to those achieved at monochromatized spectroscopy beamlines at synchrotron light sources. For x-ray absorption near edge structure, the monochromatized flux is small (due to the use of a low-powered x-ray generator) but still useful for routine transmission-mode studies of concentrated samples. These results indicate that upgrading to a standard commercial high-power line-focused x-ray tube or rotating anode x-ray generator would result in monochromatized fluxes of order 10(6)-10(7) photons/s with no loss in energy resolution. This work establishes core technical capabilities for a rejuvenation of laboratory-based hard x-ray spectroscopies that could have special relevance for contemporary research on catalytic or electrical energy storage systems using transition-metal, lanthanide, or noble-metal active species. PMID:25430123

  8. Interaction of Isophorone with Pd(111): A Combination of Infrared Reflection–Absorption Spectroscopy, Near-Edge X-ray Absorption Fine Structure, and Density Functional Theory Studies

    PubMed Central

    2014-01-01

    Atomistic level understanding of interaction of α,β-unsaturated carbonyls with late transition metals is a key prerequisite for rational design of new catalytic materials with the desired selectivity toward C=C or C=O bond hydrogenation. The interaction of this class of compounds with transition metals was investigated on α,β-unsaturated ketone isophorone on Pd(111) as a prototypical system. In this study, infrared reflection–absorption spectroscopy (IRAS), near-edge X-ray absorption fine structure (NEXAFS) experiments, and density functional theory calculations including van der Waals interactions (DFT+vdW) were combined to obtain detailed information on the binding of isophorone to palladium at different coverages and on the effect of preadsorbed hydrogen on the binding and adsorption geometry. According to these experimental observations and the results of theoretical calculations, isophorone adsorbs on Pd(111) in a flat-lying geometry at low coverages. With increasing coverage, both C=C and C=O bonds of isophorone tilt with respect to the surface plane. The tilting is considerably more pronounced for the C=C bond on the pristine Pd(111) surface, indicating a prominent perturbation and structural distortion of the conjugated π system upon interaction with Pd. Preadsorbed hydrogen leads to higher tilting angles of both π bonds, which points to much weaker interaction of isophorone with hydrogen-precovered Pd and suggests the conservation of the in-plane geometry of the conjugated π system. The results of the DFT+vdW calculations provide further insights into the perturbation of the molecular structure of isophorone on Pd(111). PMID:26089998

  9. XANES of Chromium in Sludges Used as Soil Ameliorants

    SciTech Connect

    Naftel, S.J.; Martin, R.R.; Sham, T.K.; Hart, B.; Powell, M.A.

    2010-12-01

    Samples of sewage sludges proposed for use as soil ameliorants in an Indo-Canadian project were tested for chromium content. Standard aqua regia extractions found one sludge to have excessive amounts of Cr. X-ray absorption near-edge structure (XANES) spectroscopy, however, indicated that the Cr was present in the relatively benign Cr(III) oxidation state in all the sludge samples.

  10. Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy for mapping nano-scale distribution of organic carbon forms in soil: Application to black carbon particles

    NASA Astrophysics Data System (ADS)

    Lehmann, Johannes; Liang, Biqing; Solomon, Dawit; Lerotic, Mirna; LuizãO, Flavio; Kinyangi, James; SchäFer, Thorsten; Wirick, Sue; Jacobsen, Chris

    2005-03-01

    Small-scale heterogeneity of organic carbon (C) forms in soils is poorly quantified since appropriate analytical techniques were not available up to now. Specifically, tools for the identification of functional groups on the surface of micrometer-sized black C particles were not available up to now. Scanning Transmission X-ray Microscopy (STXM) using synchrotron radiation was used in conjunction with Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy to investigate nano-scale distribution (50-nm resolution) of C forms in black C particles and compared to synchrotron-based FTIR spectroscopy. A new embedding technique was developed that did not build on a C-based embedding medium and did not pose the risk of heat damage to the sample. Elemental sulfur (S) was melted to 220°C until it polymerized and quenched with liquid N2 to obtain a very viscous plastic S in which the black C could be embedded until it hardened to a noncrystalline state and was ultrasectioned. Principal component and cluster analysis followed by singular value decomposition was able to resolve distinct areas in a black carbon particle. The core of the studied biomass-derived black C particles was highly aromatic even after thousands of years of exposure in soil and resembled the spectral characteristics of fresh charcoal. Surrounding this core and on the surface of the black C particle, however, much larger proportions of carboxylic and phenolic C forms were identified that were spatially and structurally distinct from the core of the particle. Cluster analysis provided evidence for both oxidation of the black C particle itself as well as adsorption of non-black C. NEXAFS spectroscopy has great potential to allow new insight into black C properties with important implications for biogeochemical cycles such as mineralization of black C in soils and sediments, and adsorption of C, nutrients, and pollutants as well as transport in the geosphere, hydrosphere, and atmosphere.

  11. Near-Edge X-ray Absorption Fine Structure Imaging of Spherical and Flat Counterfaces of Ultrananocrystalline Diamond Tribological Contacts: A Correlation of Surface Chemistry and Friction

    SciTech Connect

    A Konicek; C Jaye; M Hamilton; W Sawyer; D Fischer; R Carpick

    2011-12-31

    A recently installed synchrotron radiation near-edge X-ray absorption fine structure (NEXAFS) full field imaging electron spectrometer was used to spatially resolve the chemical changes of both counterfaces from an ultra-nanocrystalline diamond (UNCD) tribological contact. A silicon flat and Si{sub 3}N{sub 4} sphere were both coated with UNCD, and employed to form two wear tracks on the flat in a linear reciprocating tribometer. The first wear track was produced using a new, unconditioned sphere whose surface was thus conditioned during this first experiment. This led to faster run-in and lower friction when producing a second wear track using the conditioned sphere. The large depth of field of the magnetically guided NEXAFS imaging detector enabled rapid, large area spectromicroscopic imaging of both the spherical and flat surfaces. Laterally resolved NEXAFS data from the tribological contact area revealed that both substrates had an as-grown surface layer that contained a higher fraction of sp{sup 2}-bonded carbon and oxygen which was mechanically removed. Unlike the flat, the film on the sphere showed evidence of having graphitic character, both before and after sliding. These results show that the graphitic character of the sphere is not solely responsible for low friction and short run-in. Rather, conditioning the sphere, likely by removing asperities and passivating dangling bonds, leads to lower friction with less chemical modification of the substrate in subsequent tests. The new NEXAFS imaging spectroscopy detector enabled a more complete understanding of the tribological phenomena by imaging, for the first time, the surface chemistry of the spherical counterface which had been in continual contact during wear track formation.

  12. Spectroscopic analysis of small organic molecules: A comprehensive near-edge x-ray-absorption fine-structure study of C{sub 6}-ring-containing molecules

    SciTech Connect

    Kolczewski, C.; Puettner, R.; Martins, M.; Schlachter, A.S.; Snell, G.; Sant'Anna, M.M.; Hermann, K.; Kaindl, G.

    2006-01-21

    We report high-resolution C 1s near-edge x-ray-absorption fine-structure (NEXAFS) spectra of the C{sub 6}-ring-containing molecules benzene (C{sub 6}H{sub 6}), 1,3- and 1,4-cyclohexadiene (C{sub 6}H{sub 8}), cyclohexene (C{sub 6}H{sub 10}), cyclohexane (C{sub 6}H{sub 12}), styrene (C{sub 8}H{sub 8}), and ethylbenzene (C{sub 8}H{sub 10}) which allow us to examine the gradual development of delocalization of the corresponding {pi} electron systems. Due to the high experimental resolution, vibrational progressions can be partly resolved in the spectra. The experimental spectra are compared with theoretical NEXAFS spectra obtained from density-functional theory calculations where electronic final-state relaxation is accounted for. The comparison yields very good agreement between theoretical spectra and experimental results. In all cases, the spectra can be described by excitations to {pi}*- and {sigma}*-type final-state orbitals with valence character, while final-state orbitals of Rydberg character make only minor contributions. The lowest C 1s{yields}1{pi}* excitation energy is found to agree in the (experimental and theoretical) spectra of all molecules except for 1,3-cyclohexadiene (C{sub 6}H{sub 8}) where an energy smaller by about 0.6 eV is obtained. The theoretical analysis can explain this result by different binding properties of this molecule compared to the others.

  13. Systematic Oxidation of Polystyrene by Ultraviolet-Ozone, Characterized by Near-Edge X-ray Absorption Fine Structure and Contact Angle

    SciTech Connect

    Klein,R.; Fischer, D.; Lenhart, J.

    2008-01-01

    The process of implanting oxygen in polystyrene (PS) via exposure to ultraviolet-ozone (UV-O) was systematically investigated using the characterization technique of near-edge X-ray absorption fine structure (NEXAFS). Samples of PS exposed to UV-O for 10-300 s and washed with isopropanol were analyzed using the carbon and oxygen K-edge NEXAFS partial electron yields, using various retarding bias voltages to depth-profile the oxygen penetration into the surface. Evaluation of reference polymers provided a scale to quantify the oxygen concentration implanted by UV-O treatment. We find that ozone initially reacts with the double bonds on the phenyl rings, forming carbonyl groups, but within 1 min of exposure, the ratio of double to single oxygen bonds stabilizes at a lower value. Oxygen penetrates the film with relative ease, creating a fairly uniform distribution of oxygen within at least the first 4 nm (the effective depth probed by NEXAFS here). Before oxygen accumulates in large concentrations, however, it preferentially degrades the uppermost layer of the film by removing oxygenated low-molecular-weight oligomers. The failure to accumulate high concentrations of oxygen is seen in the nearly constant carbon edge jump, the low concentration of oxygen even at 5 min exposure (58% of that in poly(4-acetoxystyrene), the polymer with the most similarities to UV-O-treated PS), and the relatively high contact angles. At 5 min exposure the oxygen concentration contains ca. 7 atomic % oxygen. The oxygen species that are implanted consist predominantly of single O-C bonds and double OC bonds but also include a small fraction of O-H. UV-O treatment leads a plateau after 2 min exposure in the water contact angle hysteresis, at a value of 67 {+-} 2, due primarily to chemical heterogeneity. Annealing above Tg allows oxygenated species to move short distances away from the surface but not diffuse further than 1-2 nm.

  14. The C 1s and N 1s near edge x-ray absorption fine structure spectra of five azabenzenes in the gas phase.

    PubMed

    Vall-llosera, G; Gao, B; Kivimäki, A; Coreno, M; Alvarez Ruiz, J; de Simone, M; Agren, H; Rachlew, E

    2008-01-28

    Near edge x-ray absorption fine structure spectra have been measured and interpreted by means of density functional theory for five different azabenzenes (pyridine, pyridazine, pyrimidine, pyrazine, and s-triazine) in the gas phase. The experimental and theoretical spectra at the N 1s and C 1s edges show a strong resonance assigned to the transition of the 1s electron in the respective N or C atoms to the lowest unoccupied molecular orbital with pi(*) symmetry. As opposed to the N 1s edge, at the C 1s edge this resonance is split due to the different environments of the core hole atom in the molecule. The shift in atomic core-level energy due to a specific chemical environment is explained with the higher electronegativity of the N atom compared to the C atom. The remaining resonances below the ionization potential (IP) are assigned to sigma or pi [corrected] orbitals with mixed valence/Rydberg [corrected] character. Upon N addition, a reduction of intensity is observed in the Rydberg region at both edges as compared to the intensity in the continuum. Above the IP one or more resonances are seen and ascribed here to transitions to sigma(*) orbitals. Calculating the experimental and theoretical Delta(pi) term values at both edges, we observe that they are almost the same within +/-1 eV as expected for isoelectronic bonded pairs. The term values of the pi(*) and sigma(*) resonances are discussed in terms of the total Z number of the atoms participating in the bond. PMID:18247958

  15. Characterization of Functionalized Self-Assembled Monolayers and Surface-Attached Interlocking Molecules Using Near-Edge X-ray Absorption Fine Structure Spectroscopy

    SciTech Connect

    Willey, T; Willey, T

    2004-03-24

    Quantitative knowledge of the fundamental structure and substrate binding, as well as the direct measurement of conformational changes, are essential to the development of self-assembled monolayers (SAMs) and surface-attached interlocking molecules, catenanes and rotaxanes. These monolayers are vital to development of nano-mechanical, molecular electronic, and biological/chemical sensor applications. This dissertation investigates properties of functionalized SAMs in sulfur-gold based adsorbed molecular monolayers using quantitative spectroscopic techniques including near-edge x-ray absorption fine structure spectroscopy (NEXAFS) and x-ray photoelectron spectroscopy (XPS). The stability of the gold-thiolate interface is addressed. A simple model SAM consisting of dodecanethiol adsorbed on Au(111) degrades significantly in less than 24 hours under ambient laboratory air. S 2p and O 1s XPS show the gold-bound thiolates oxidize to sulfinates and sulfonates. A reduction of organic material on the surface and a decrease in order are observed as the layer degrades. The effect of the carboxyl vs. carboxylate functionalization on SAM structure is investigated. Carboxyl-terminated layers consisting of long alkyl-chain thiols vs. thioctic acid with short, sterically separated, alkyl groups are compared and contrasted. NEXAFS shows a conformational change, or chemical switchability, with carboxyl groups tilted over and carboxylate endgroups more upright. Surface-attached loops and simple surface-attached rotaxanes are quantitatively characterized, and preparation conditions that lead to desired films are outlined. A dithiol is often insufficient to form a molecular species bound at each end to the substrate, while a structurally related disulfide-containing polymer yields surface-attached loops. Similarly, spectroscopic techniques show the successful production of a simple, surface-attached rotaxane that requires a ''molecular riveting'' step to hold the mechanically attached

  16. Characterization of functionalized self-assembled monolayers and surface-attached interlocking molecules using near-edge X-ray absorption fine structure spectroscopy

    NASA Astrophysics Data System (ADS)

    Willey, Trevor Michael

    Quantitative knowledge of the fundamental structure and substrate binding, as well as the direct measurement of conformational changes, are essential to the development of self-assembled monolayers (SAMs) and surface-attached interlocking molecules, catenanes and rotaxanes. These monolayers are vital to development of nano-mechanical, molecular electronic, and biological/chemical sensor applications. This dissertation investigates properties of functionalized SAMs in sulfur-gold based adsorbed molecular monolayers using quantitative spectroscopic techniques including near-edge x-ray absorption fine structure spectroscopy (NEXAFS) and x-ray photoelectron spectroscopy (XPS). The stability of the gold-thiolate interface is addressed. A simple model SAM consisting of dodecanethiol adsorbed on Au(111) degrades significantly in less than 24 hours under ambient laboratory air. S 2p and O 1s XPS show the gold-bound thiolates oxidize to sulfinates and sulfonates. A reduction of organic material on the surface and a decrease in order are observed as the layer degrades. The effect of the carboxyl vs. carboxylate functionalization on SAM structure is investigated. Carboxyl-terminated layers consisting of long alkyl-chain thiols vs. thioctic acid with short, sterically separated, alkyl groups are compared and contrasted. NEXAFS shows a conformational change, or chemical switchability, with carboxyl groups tilted over and carboxylate endgroups more upright. Surface-attached loops and simple surface-attached rotaxanes are quantitatively characterized, and preparation conditions that lead to desired films are outlined. A dithiol is often insufficient to form a molecular species bound at each end to the substrate, while a structurally related disulfide-containing polymer yields surface-attached loops. Similarly, spectroscopic techniques show the successful production of a simple, surface-attached rotaxane that requires a "molecular riveting" step to hold the mechanically attached

  17. How water molecules affect the catalytic activity of hydrolases--a XANES study of the local structures of peptide deformylase.

    PubMed

    Cui, Peixin; Wang, Yu; Chu, Wangsheng; Guo, Xiaoyun; Yang, Feifei; Yu, Meijuan; Zhao, Haifeng; Dong, Yuhui; Xie, Yaning; Gong, Weimin; Wu, Ziyu

    2014-01-01

    Peptide deformylase (PDF) is a prokaryotic enzyme that catalyzes the deformylation of nascent peptides generated during protein synthesis and water molecules play a key role in these hydrolases. Using X-ray absorption near edge spectroscopy (XANES) and ab initio calculations we accurately probe the local atomic environment of the metal ion binding in the active site of PDF at different pH values and with different metal ions. This new approach is an effective way to monitor existing correlations among functions and structural changes. We show for the first time that the enzymatic activity depends on pH values and metal ions via the bond length of the nearest coordinating water (Wat1) to the metal ion. Combining experimental and theoretical data we may claim that PDF exhibits an enhanced enzymatic activity only when the distance of the Wat1 molecule with the metal ion falls in the limited range from 2.15 to 2.55 Å. PMID:25503313

  18. Composition-dependent structure of polycrystalline magnetron-sputtered V-Al-C-N hard coatings studied by XRD, XPS, XANES and EXAFS.

    PubMed

    Krause, Bärbel; Darma, Susan; Kaufholz, Marthe; Mangold, Stefan; Doyle, Stephen; Ulrich, Sven; Leiste, Harald; Stüber, Michael; Baumbach, Tilo

    2013-08-01

    V-Al-C-N hard coatings with high carbon content were deposited by reactive radio-frequency magnetron sputtering using an experimental combinatorial approach, deposition from a segmented sputter target. The composition-dependent coexisting phases within the coating were analysed using the complementary methods of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption fine-structure spectroscopy (EXAFS). For the analysis of the X-ray absorption near-edge spectra, a new approach for evaluation of the pre-edge peak was developed, taking into account the self-absorption effects in thin films. Within the studied composition range, a mixed face-centred cubic (V,Al)(C,N) phase coexisting with a C-C-containing phase was observed. No indication of hexagonal (V,Al)(N,C) was found. The example of V-Al-C-N demonstrates how important a combination of complementary methods is for the detection of coexisting phases in complex multi-element coatings. PMID:24046506

  19. Composition-dependent structure of polycrystalline magnetron-sputtered V–Al–C–N hard coatings studied by XRD, XPS, XANES and EXAFS

    PubMed Central

    Krause, Bärbel; Darma, Susan; Kaufholz, Marthe; Mangold, Stefan; Doyle, Stephen; Ulrich, Sven; Leiste, Harald; Stüber, Michael; Baumbach, Tilo

    2013-01-01

    V–Al–C–N hard coatings with high carbon content were deposited by reactive radio-frequency magnetron sputtering using an experimental combinatorial approach, deposition from a segmented sputter target. The composition-dependent coexisting phases within the coating were analysed using the complementary methods of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption fine-structure spectroscopy (EXAFS). For the analysis of the X-ray absorption near-edge spectra, a new approach for evaluation of the pre-edge peak was developed, taking into account the self-absorption effects in thin films. Within the studied composition range, a mixed face-centred cubic (V,Al)(C,N) phase coexisting with a C–C-containing phase was observed. No indication of hexagonal (V,Al)(N,C) was found. The example of V–Al–C–N demonstrates how important a combination of complementary methods is for the detection of coexisting phases in complex multi-element coatings. PMID:24046506

  20. Thermo-Active Behavior of Ethylene-Vinyl Acetate | Multiwall Carbon Nanotube Composites Examined by in Situ near-Edge X-ray Absorption Fine-Structure Spectroscopy

    PubMed Central

    2015-01-01

    NEXAFS spectroscopy was used to investigate the temperature dependence of thermally active ethylene-vinyl acetate | multiwall carbon nanotube (EVA|MWCNT) films. The data shows systematic variations of intensities with increasing temperature. Molecular orbital assignment of interplaying intensities identified the 1s → π*C=C and 1s → π*C=O transitions as the main actors during temperature variation. Furthermore, enhanced near-edge interplay was observed in prestrained composites. Because macroscopic observations confirmed enhanced thermal-mechanical actuation in prestrained composites, our findings suggest that the interplay of C=C and C=O π orbitals may be instrumental to actuation. PMID:24803975

  1. Temperature and density dependence of XANES spectra in warm dense aluminum plasmas

    SciTech Connect

    Recoules, V.; Mazevet, S.

    2009-08-01

    Using ab initio molecular-dynamics simulations combined with linear-response theory, we calculate the density and temperature dependence of the x-ray absorption near-edge structure (XANES) of a dense aluminum plasma. At solid density and for temperatures increasing up to 6 eV, we see that the XANES spectrum loses its well-known room-temperature structure, first due to melting and second due to loss of correlation in the liquid. Similarly, as the density decreases and the system evolves from a liquid to a plasma, the XANES spectrum becomes less structured. As the density is further lowered and the system turns into an atomic fluid, a pre-edge forms as the 3p state becomes bound. We suggest that direct measurements of the XANES spectra in this density region is a unique opportunity to validate pressure ionization models routinely used in plasma physics modeling.

  2. Electronic structure and optical properties of CdS{sub x}Se{sub 1−x} solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations

    SciTech Connect

    Murphy, M. W.; Yiu, Y. M. Sham, T. K.; Ward, M. J.; Liu, L.; Hu, Y.; Zapien, J. A.; Liu, Yingkai

    2014-11-21

    The electronic structure and optical properties of a series of iso-electronic and iso-structural CdS{sub x}Se{sub 1−x} solid solution nanostructures have been investigated using X-ray absorption near edge structure, extended X-ray absorption fine structure, and X-ray excited optical luminescence at various absorption edges of Cd, S, and Se. It is found that the system exhibits compositions, with variable local structure in-between that of CdS and CdSe accompanied by tunable optical band gap between that of CdS and CdSe. Theoretical calculation using density functional theory has been carried out to elucidate the observations. It is also found that luminescence induced by X-ray excitation shows new optical channels not observed previously with laser excitation. The implications of these observations are discussed.

  3. Overlap population diagram for ELNES and XANES: peak assignment and interpretation

    NASA Astrophysics Data System (ADS)

    Mizoguchi, Teruyasu

    2009-03-01

    This article reviews overlap population (OP) diagrams for electron energy loss near-edge structure (ELNES) and x-ray absorption near-edge structure (XANES). By using the OP diagrams, peaks in ELNES and XANES of MgO, ZnO, AlN, GaN, InN, and YBa2Cu3O7-x are interpreted in terms of cation-anion and cation-cation interactions. Common features are found in the OP diagrams for different edges. A reconstruction of the unoccupied electronic structure is demonstrated by aligning the different edges with the common features in the OP diagrams. The OP diagram is also applied to the Cu/Al2O3 hetero-interface to find the relationships among ELNES, atomic and electronic structures, and properties.

  4. Speciation and Long- and Short-term Molecular-level Dynamics of Soil Organic Sulfur Studied by X-ray Absorption Near-Edge Structure Spectroscopy

    SciTech Connect

    D Solomon; J Lehmann; K Knoth de Zarruk; J Dathe; J Kinyangi; B Liang; S Machado

    2011-12-31

    We investigated speciation, oxidative state changes, and long- and short-term molecular-level dynamics of organic S after 365 d of aerobic incubation with and without the addition of sugarcane residue using XANES spectroscopy. Soil samples were collected from the upper 15 cm of undisturbed grasslands since 1880, from undisturbed grasslands since 1931, and from cultivated fields since 1880 in the western United States. We found three distinct groups of organosulfur compounds in these grassland-derived soils: (i) strongly reduced (S{sup 0} to S{sup 1+}) organic S that encompasses thiols, monosulfides, disulfides, polysulfides, and thiophenes; (ii) organic S in intermediate oxidation (S{sup 2+} to S{sup 5+}) states, which include sulfoxides and sulfonates; and (iii) strongly oxidized (S{sup 6+}) organic S, which comprises ester-SO{sub 4}-S. The first two groups represent S directly linked to C and accounted for 80% of the total organic S detected by XANES from the undisturbed soils. Aerobic incubation without the addition of sugarcane residue led to a 21% decline in organanosulfur compounds directly linked to C and to up to an 82% increase inorganic S directly bonded to O. Among the C-bonded S compounds, low-valence thiols, sulfides, thiophenic S, and intermediate-valence sulfoxide S seem to be highly susceptible to microbial attack and may represent the most reactive components of organic S pool in these grassland soils. Sulfonate S exhibited a much lower short-term reactivity. The incorporation of sugarcane residue resulted in an increase in organosulfur compounds directly bonded to C at the early stage of incubation. However, similar to soils incubated without residue addition, the proportion of organic S directly linked to C continued to decline with increasing duration of aerobic incubation, whereas the proportion of organic S directly bonded to O showed a steady rise.

  5. Unraveling the Solid-Liquid-Vapor Phase Transition Dynamics at the Atomic Level with Ultrafast X-Ray Absorption Near-Edge Spectroscopy

    NASA Astrophysics Data System (ADS)

    Dorchies, F.; Lévy, A.; Goyon, C.; Combis, P.; Descamps, D.; Fourment, C.; Harmand, M.; Hulin, S.; Leguay, P. M.; Petit, S.; Peyrusse, O.; Santos, J. J.

    2011-12-01

    X-ray absorption near-edge spectroscopy (XANES) is a powerful probe of electronic and atomic structures in various media, ranging from molecules to condensed matter. We show how ultrafast time resolution opens new possibilities to investigate highly nonequilibrium states of matter including phase transitions. Based on a tabletop laser-plasma ultrafast x-ray source, we have performed a time-resolved (˜3ps) XANES experiment that reveals the evolution of an aluminum foil at the atomic level, when undergoing ultrafast laser heating and ablation. X-ray absorption spectra highlight an ultrafast transition from the crystalline solid to the disordered liquid followed by a progressive transition of the delocalized valence electronic structure (metal) down to localized atomic orbitals (nonmetal—vapor), as the average distance between atoms increases.

  6. Biogeochemical reductive release of soil embedded arsenate around a crater area (Guandu) in northern Taiwan using X-ray absorption near-edge spectroscopy.

    PubMed

    Chiang, Kai-Ying; Chen, Tsan-Yao; Lee, Chih-Hao; Lin, Tsang-Lang; Wang, Ming-Kuang; Jang, Ling-Yun; Lee, Jyh-Fu

    2013-03-01

    This study investigates biogeochemical reductive release of arsenate from beudantite into solution in a crater area in northern Taiwan, using a combination of X-ray absorption near-edge structure (XANES) and atomic absorption spectrometry. Total arsenic (As) concentrations in the soil were more than 200 mg/kg. Over four months of laboratory experiments, less than 0.8% As was released into solution after reduction experiments. The 71% to 83% As was chemically reduced into arsenite (As(III)) and partially weathering into the soluble phase. The kinetic dissolution and re-precipitation of As, Fe, Pb and sulfate in this area of paddy soils merits further study. PMID:23923437

  7. Organic carbon and sulphur compounds in wetland soils: insights on structure and transformation processes using K-edge XANES and NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Jokic, Aleksander; Cutler, Jeffrey N.; Ponomarenko, Elena; van der Kamp, Garth; Anderson, Darwin W.

    2003-07-01

    X-ray absorption near-edge structure (XANES) and nuclear magnetic resonance (NMR) spectroscopy were used in combination to characterize organic carbon structures in a series of wetland soils in Saskatchewan, and XANES spectroscopy was also used to examine sulphur speciation in the soils. The organic C contents of most of the wetland soils are consistently higher by a factor of two to five times compared to adjacent well-drained soils. NMR analyses indicate that the organic matter in the wetland soils consists of predominantly aliphatic structures such as carbohydrates and long chain poly(methylene) units which are refractory structures found in plant waxes. The poly(methylene) structures have a significant capacity to sorb nonpolar organic molecules. The phenolic OH and carboxyl group content of the wetland soils studied is an additional significant factor in their sequestering ability for heavy metals or pesticides. Carbon XANES spectroscopy shows that the surface (˜10 nm) layer of particulate organic matter has a structure dominated by aromatic, carbohydrate and carboxylic acid-like material apparently derived from partially degraded lignin and cellulose polymers which are adsorbed onto clay minerals. The aliphatic structures remaining in this surface layer are probably recalcitrant (poly)methylene units. At a depth of ˜100 nm, the aliphatic content significantly increases suggesting the presence of more labile structures. The presence of these more labile aliphatic compounds may be due to slow decomposition rates in the wet, often cool environments present and to the protective action of the more refractory components in the surface ˜10 nm of the organic matter. Drying of the wetlands, either by draining or as a result of climate change, is likely to result in the rapid decomposition of these labile organic structures releasing carbon dioxide. Our data indicate that the preservation of the organic carbon compounds in these soils is a result of their presence

  8. Structural investigations of PuIII phosphate by X-ray diffraction, MAS-NMR and XANES spectroscopy

    NASA Astrophysics Data System (ADS)

    Popa, Karin; Raison, Philippe E.; Martel, Laura; Martin, Philippe M.; Prieur, Damien; Solari, Pier L.; Bouëxière, Daniel; Konings, Rudy J. M.; Somers, Joseph

    2015-10-01

    PuPO4 was prepared by a solid state reaction method and its crystal structure at room temperature was solved by powder X-ray diffraction combined with Rietveld refinement. High resolution XANES measurements confirm the +III valence state of plutonium, in agreement with valence bond derivation. The presence of the americium (as β- decay product of plutonium) in the +III oxidation state was determined based on XANES spectroscopy. High resolution solid state 31P NMR agrees with the XANES results and the presence of a solid-solution.

  9. XANES Reveals the Flexible Nature of Hydrated Strontium in Aqueous Solution.

    PubMed

    D'Angelo, Paola; Migliorati, Valentina; Sessa, Francesco; Mancini, Giordano; Persson, Ingmar

    2016-05-01

    X-ray absorption near-edge structure (XANES) spectroscopy has been used to determine the structure of the hydrated strontium in aqueous solution. The XANES analysis has been carried out using solid [Sr(H2O)8](OH)2 as reference model. Classical and Car-Parrinello molecular dynamics (MD) simulations have been carried out and in the former case two different sets of Lennard-Jones parameters have been used for the Sr(2+) ion. The best performing theoretical approach has been chosen on the basis of the experimental results. XANES spectra have been calculated starting from MD trajectories, without carrying out any minimization of the structural parameters. This procedure allowed us to properly account for thermal and structural fluctuations occurring in the aqueous solution in the analysis of the experimental spectrum. A deconvolution procedure has been applied to the raw absorption data thus increasing the sensitivity of XANES spectroscopy. One of the classical MD simulations has been found to provide a XANES theoretical spectrum in better agreement with the experimental data. An 8-fold hydration complex with a Sr-O distance of 2.60 Å has been found to be compatible with the XANES data, in agreement with previous findings. However, the hydration shells of the strontium ions have been found to have a flexible nature with a fast ligand exchange rate between the first and second hydration shell occurring in the picosecond time scale. PMID:27065305

  10. Thin Film Structure of Tetraceno[2,3-B]thiophene Characterized By Grazing Incidence X-Ray Scattering And Near-Edge X-Ray Absorption Fine Structure Analysis

    SciTech Connect

    Yuan, Q.; Mannsfeld, S.C.B.; Tang, M.L.; Toney, M.F.; Luening, J.; Bao, Z.A.; /Stanford U., Chem. Eng. /SLAC, SSRL

    2009-05-11

    Understanding the structure-property relationship for organic semiconductors is crucial in rational molecular design and organic thin film process control. Charge carrier transport in organic field-effect transistors predominantly occurs in a few semiconductor layers close to the interface in contact with the dielectric layer, and the transport properties depend sensitively on the precise molecular packing. Therefore, a better understanding of the impact of molecular packing and thin film morphology in the first few monolayers above the dielectric layer on charge transport is needed to improve the transistor performance. In this Article, we show that the detailed molecular packing in thin organic semiconductor films can be solved through a combination of grazing incidence X-ray diffraction (GIXD), near-edge X-ray absorption spectra fine structure (NEXAFS) spectroscopy, energy minimization packing calculations, and structure refinement of the diffraction data. We solve the thin film structure for 2 and 20 nm thick films of tetraceno[2,3-b]thiophene and detect only a single phase for these thicknesses. The GIXD yields accurate unit cell dimensions, while the precise molecular arrangement in the unit cell was found from the energy minimization and structure refinement; the NEXAFS yields a consistent molecular tilt. For the 20 nm film, the unit cell is triclinic with a = 5.96 A, b = 7.71 A, c = 15.16 A, alpha = 97.30 degrees, beta = 95.63 degrees, gamma = 90 degrees; there are two molecules per unit cell with herringbone packing (49-59 degree angle) and tilted about 7 degrees from the substrate normal. The thin film structure is significantly different from the bulk single-crystal structure, indicating the importance of characterizing thin film to correlate with thin film device performance. The results are compared to the corresponding data for the chemically similar and widely used pentacene. Possible effects of the observed thin film structure and morphology on

  11. X-ray absorption near edge spectroscopy with a superconducting detector for nitrogen dopants in SiC

    PubMed Central

    Ohkubo, M.; Shiki, S.; Ukibe, M.; Matsubayashi, N.; Kitajima, Y.; Nagamachi, S.

    2012-01-01

    Fluorescence-yield X-ray absorption fine structure (FY-XAFS) is extensively used for investigating atomic-scale local structures around specific elements in functional materials. However, conventional FY-XAFS instruments frequently cannot cover trace light elements, for example dopants in wide gap semiconductors, because of insufficient energy resolution of semiconductor X-ray detectors. Here we introduce a superconducting XAFS (SC-XAFS) apparatus to measure X-ray absorption near-edge structure (XANES) of n-type dopant N atoms (4 ×1019 cm−3) implanted at 500°C into 4H-SiC substrates annealed subsequently. The XANES spectra and ab initio multiple scattering calculations indicate that the N atoms almost completely substitute for the C sites, associated with a possible existence of local CN regions, in the as-implanted state. This is a reason why hot implantation is necessary for dopant activation in ion implantation. The SC-XAFS apparatus may play an important role in improving doping processes for energy-saving wide-gap semiconductors and other functional materials. PMID:23152937

  12. Determining the Sulfur species in the dispersants Corexit 9500A and 9527A applying S K-edge XANES spectroscopy

    NASA Astrophysics Data System (ADS)

    Bovenkamp-Langlois, Lisa; Roy, Amitava

    2016-05-01

    The dispersants Corexit 9500A and 9527A were used extensively during the Deepwater Horizon oil spill in the Gulf of Mexico. Sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy was used to investigate the dispersants for the sulfur based components. The main sulfur containing component should be dioctyl sodium sulfosuccinate (DOSS). S K-edge XANES analysis shows that indeed the major sulfur species in both kinds of Corexit (9500A and 9527A) is sulfonic acid which is a part of DOSS. In addition some fraction of sulfone was detected.

  13. The effect of zirconia content on the structure of zirconia-silica xerogels as determined by x-ray and neutron diffraction and Zr K-edge EXAFS and XANES

    NASA Astrophysics Data System (ADS)

    Mountjoy, G.; Anderson, R.; Newport, R. J.; Smith, M. E.

    2000-04-01

    We present combined x-ray and neutron diffraction, and extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) results on a single set of (ZrO2 )x (SiO2 )1-x xerogel samples. In these samples, there is improved homogeneity of Zr compared to our previous study, due to greater dilution of the precursor Zr n-propoxide in propan-1-ol. Structural parameters obtained from model fitting of the diffraction and EXAFS data are compared with those in reference compounds. A qualitative comparison of XANES spectra is also made. The results show that for xicons/Journals/Common/geq" ALT="geq" ALIGN="TOP"/> 0.3 there is phase separation of ZrO2 and the Zr environment is similar to that in monoclinic ZrO2 and Zr hydroxide. For xicons/Journals/Common/leq" ALT="leq" ALIGN="TOP"/> 0.2 there is no phase separation, the SiO2 network is distorted and the Zr coordination is similar to that in Zr n-propoxide, with some Zr-Zr clustering.

  14. The competitive growth of cubic domains in Ti(1-x)AlxN films studied by diffraction anomalous near-edge structure spectroscopy.

    PubMed

    Pinot, Y; Tuilier, M-H; Pac, M-J; Rousselot, C; Thiaudière, D

    2015-11-01

    Titanium and aluminium nitride films deposited by magnetron sputtering generally grow as columnar domains made of oriented nanocrystallites with cubic or hexagonal symmetry depending on Al content, which are embedded in more disordered grain boundaries. The substitution of Al atoms for Ti in the cubic lattice of the films improves their resistance to wear and oxidation, allowing their use as protective coatings. Ti K-edge X-ray absorption spectroscopy, which probes both crystallized and more disordered grain boundaries, and X-ray diffraction anomalous fine structure, which is sensitive to short- and long-range order within a given crystallized domain, are carried out on a set of Ti(1-x)AlxN films deposited by magnetron sputtering on Si substrates. Attention is paid to the shape of the pre-edge region, which is sensitive to the symmetry of the site occupied by Ti atoms, either octahedral in face-centred-cubic Ti-rich (TiN, Ti0.54Al0.46N) samples or tetrahedral in hexagonal-close-packed Al-rich (Ti0.32Al0.68N) films. In order to obain information on the titanium environment in the well crystallized areas, subtraction of the smooth part of the energy-dependent structure factor for the Bragg reflections is applied to the pre-edge region of the diffraction anomalous data in order to restore their spectroscopic appearance. A flat pre-edge is related to the typical octahedral environment of Ti atoms for cubic reflections. The difference observed between pre-edge spectra associated with face-centred-cubic 200 and 111 Bragg reflections of Ti0.54Al0.46N is assigned to Ti enrichment of 111 large well ordered domains compared with the more disordered 200 ones. The sharp peak observed in the spectrum recorded from the hexagonal 002 peak of Ti0.32Al0.68N can be regarded as a standard for the pure tetrahedral Ti environment in hexagonal-close-packed nitride. PMID:26524309

  15. Catalyst Chemical State during CO Oxidation Reaction on Cu(111) Studied with Ambient-Pressure X-ray Photoelectron Spectroscopy and Near Edge X-ray Adsorption Fine Structure Spectroscopy.

    PubMed

    Eren, Baran; Heine, Christian; Bluhm, Hendrik; Somorjai, Gabor A; Salmeron, Miquel

    2015-09-01

    The chemical structure of a Cu(111) model catalyst during the CO oxidation reaction in the CO+O2 pressure range of 10-300 mTorr at 298-413 K was studied in situ using surface sensitive X-ray photoelectron and adsorption spectroscopy techniques [X-ray photoelectron spectroscopy (XPS) and near edge X-ray adsorption fine structure spectroscopy (NEXAFS)]. For O2:CO partial pressure ratios below 1:3, the surface is covered by chemisorbed O and by a thin (∼1 nm) Cu2O layer, which covers completely the surface for ratios above 1:3 between 333 and 413 K. The Cu2O film increases in thickness and exceeds the escape depth (∼3-4 nm) of the XPS and NEXAFS photoelectrons used for analysis at 413 K. No CuO formation was detected under the reaction conditions used in this work. The main reaction intermediate was found to be CO2(δ-), with a coverage that correlates with the amount of Cu2O, suggesting that this phase is the most active for CO oxidation. PMID:26275662

  16. Interrogation of Surface, Skin, and Core Orientation in Thermotropic Liquid-Crystalline Copolyester Moldings by Near-Edge X-ray Absorption Fine Structure and Wide-Angle X-ray Scattering

    SciTech Connect

    Rendon,S.; Bubeck, R.; Thomas, L.; Burghardt, W.; Hexemer, A.; Fischer, D.

    2007-01-01

    Injection molding thermotropic liquid-crystalline polymers (TLCPs) usually results in the fabrication of molded articles that possess complex states of orientation that vary greatly as a function of thickness. 'Skin-core' morphologies are often observed in TLCP moldings. Given that both 'core' and 'skin' orientation states may often differ both in magnitude and direction, deconvolution of these complex orientation states requires a method to separately characterize molecular orientation in the surface region. A combination of two-dimensional wide-angle X-ray scattering (WAXS) in transmission and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is used to probe the molecular orientation in injection molded plaques fabricated from a 4,4'-dihydroxy-{alpha}-methylstilbene (DH{alpha}MS)-based thermotropic liquid crystalline copolyester. Partial electron yield (PEY) mode NEXAFS is a noninvasive ex situ characterization tool with exquisite surface sensitivity that samples to a depth of 2 nm. The effects of plaque geometry and injection molding processing conditions on surface orientation in the regions on- and off- axis to the centerline of injection molded plaques are presented and discussed. Quantitative comparisons are made between orientation parameters obtained by NEXAFS and those from 2D WAXS in transmission, which are dominated by the microstructure in the skin and core regions. Some qualitative comparisons are also made with 2D WAXS results from the literature.

  17. Existence of Fe{sup 4+} ions in Co{sub 2.25}Fe{sub 0.75}O{sub 4} spinel ferrite confirmed from SXRD and XANES spectroscopy

    SciTech Connect

    Panda, Manas Ranjan Bhowmik, R. N.; Sinha, A. K.

    2015-06-24

    The Co{sub 2.25}Fe{sub 0.75}O{sub 4} ferrite composition has been prepared by chemical co-precipitation route. The as-prepared sample after annealing at 900°C in air formed single phase cubic spinel structure. Synchrotron X-ray diffraction and X-ray absorption near edge structure (XANES) measurements were used to study charge states of the cations in octahedral and tetrahedral sites of the cubic spinel structure. Raman spectra indicated normal cubic spinel structure. XANES data suggested the existence of Fe{sup 4+} ions in the spinel structure.

  18. Structural investigations of Pu{sup III} phosphate by X-ray diffraction, MAS-NMR and XANES spectroscopy

    SciTech Connect

    Popa, Karin; Raison, Philippe E.; Martel, Laura; Martin, Philippe M.; Solari, Pier L.; Bouëxière, Daniel; Konings, Rudy J.M.; Somers, Joseph

    2015-10-15

    PuPO{sub 4} was prepared by a solid state reaction method and its crystal structure at room temperature was solved by powder X-ray diffraction combined with Rietveld refinement. High resolution XANES measurements confirm the +III valence state of plutonium, in agreement with valence bond derivation. The presence of the americium (as β{sup −} decay product of plutonium) in the +III oxidation state was determined based on XANES spectroscopy. High resolution solid state {sup 31}P NMR agrees with the XANES results and the presence of a solid-solution. - Graphical abstract: A full structural analysis of PuPO{sub 4} based on Rietveld analysis of room temperature X-ray diffraction data, XANES and MAS NMR measurements was performed. - Highlights: • The crystal structure of PuPO{sub 4} monazite is solved. • In PuPO{sub 4} plutonium is strictly trivalent. • The presence of a minute amount of Am{sup III} is highlighted. • We propose PuPO{sub 4} as a potential reference material for spectroscopic and microscopic studies.

  19. Phosphorus K-edge XANES spectroscopy of mineral standards

    PubMed Central

    Ingall, Ellery D.; Brandes, Jay A.; Diaz, Julia M.; de Jonge, Martin D.; Paterson, David; McNulty, Ian; Elliott, W. Crawford; Northrup, Paul

    2011-01-01

    Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was performed on phosphate mineral specimens including (a) twelve specimens from the apatite group covering a range of compositional variation and crystallinity; (b) six non-apatite calcium-rich phosphate minerals; (c) 15 aluminium-rich phosphate minerals; (d) ten phosphate minerals rich in either reduced iron or manganese; (e) four phosphate minerals rich in either oxidized iron or manganese; (f) eight phosphate minerals rich in either magnesium, copper, lead, zinc or rare-earth elements; and (g) four uranium phosphate minerals. The identity of all minerals examined in this study was independently confirmed using X-ray powder diffraction. Minerals were distinguished using XANES spectra with a combination of pre-edge features, edge position, peak shapes and post-edge features. Shared spectral features were observed in minerals with compositions dominated by the same specific cation. Analyses of apatite-group minerals indicate that XANES spectral patterns are not strongly affected by variations in composition and crystallinity typical of natural mineral specimens. PMID:21335905

  20. Phosphorus K-edge XANES Spectroscopy of Mineral Standards

    SciTech Connect

    E Ingall; J Brandes; J Diaz; M de Jonge; D Paterson; I McNulty; C Elliott; P Northrup

    2011-12-31

    Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was performed on phosphate mineral specimens including (a) twelve specimens from the apatite group covering a range of compositional variation and crystallinity; (b) six non-apatite calcium-rich phosphate minerals; (c) 15 aluminium-rich phosphate minerals; (d) ten phosphate minerals rich in either reduced iron or manganese; (e) four phosphate minerals rich in either oxidized iron or manganese; (f) eight phosphate minerals rich in either magnesium, copper, lead, zinc or rare-earth elements; and (g) four uranium phosphate minerals. The identity of all minerals examined in this study was independently confirmed using X-ray powder diffraction. Minerals were distinguished using XANES spectra with a combination of pre-edge features, edge position, peak shapes and post-edge features. Shared spectral features were observed in minerals with compositions dominated by the same specific cation. Analyses of apatite-group minerals indicate that XANES spectral patterns are not strongly affected by variations in composition and crystallinity typical of natural mineral specimens.

  1. Phosphorus K-edge XANES spectroscopy of mineral standards.

    PubMed

    Ingall, Ellery D; Brandes, Jay A; Diaz, Julia M; de Jonge, Martin D; Paterson, David; McNulty, Ian; Elliott, W Crawford; Northrup, Paul

    2011-03-01

    Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was performed on phosphate mineral specimens including (a) twelve specimens from the apatite group covering a range of compositional variation and crystallinity; (b) six non-apatite calcium-rich phosphate minerals; (c) 15 aluminium-rich phosphate minerals; (d) ten phosphate minerals rich in either reduced iron or manganese; (e) four phosphate minerals rich in either oxidized iron or manganese; (f) eight phosphate minerals rich in either magnesium, copper, lead, zinc or rare-earth elements; and (g) four uranium phosphate minerals. The identity of all minerals examined in this study was independently confirmed using X-ray powder diffraction. Minerals were distinguished using XANES spectra with a combination of pre-edge features, edge position, peak shapes and post-edge features. Shared spectral features were observed in minerals with compositions dominated by the same specific cation. Analyses of apatite-group minerals indicate that XANES spectral patterns are not strongly affected by variations in composition and crystallinity typical of natural mineral specimens. PMID:21335905

  2. Electrosynthesis of ZnO nanorods and nanotowers: Morphology and X-ray Absorption Near Edge Spectroscopy studies

    NASA Astrophysics Data System (ADS)

    Sigircik, Gokmen; Erken, Ozge; Tuken, Tunc; Gumus, Cebrail; Ozkendir, Osman M.; Ufuktepe, Yuksel

    2015-06-01

    Deposition mechanism of nano-structured ZnO films has been investigated in the absence and presence of chloride ions from aqueous solution. The resulting opto-electronic properties were interpreted extensively, using X-ray diffraction (XRD), X-ray Absorption Near Edge Spectroscopy (XANES), field emission scanning electron microscopy (FE-SEM), UV-Visible spectroscopy and four probe techniques. The ZnO deposition is mass transport controlled process and the interaction of chloride ions with the surface has great influence on diffusion kinetics, considering the substantial species (Zn2+ and OH-) involved in the construction of ZnO film. This effect does not change major lattice parameters, as shown with detailed analysis of XRD data. However, the texture coefficient (Tc) (0 0 2) value is higher in presence of chloride ions containing synthesis solution which gave vertically aligned, well defined and uniformly dispersed nanorods structure. The calculated Eg values are in the range 3.28-3.41 eV and 3.22-3.31 eV for ZnO nanorods and nanotowers synthesized at different deposition periods, respectively. Furthermore, the charge mobility values regarding the deposition periods were measured to be in the ranges from 130.4 to 449.2 cm2 V-1 s-1 and 126.2 to 204.7 cm2 V-1 s-1 for nanorods and nanotowers, respectively. From XANES results, it was shown that the Zn K-edge spectrum is dominated by the transition of Zn 1s core electrons into the unoccupied Zn 4p states of the conduction band. Comparing the rod and tower nano-structured ZnO thin films, the excitation behavior of valence band electrons is different. Moreover, the density states of Zn 4p are higher for ZnO nanorods.

  3. XANES and EXAFS study of Au-substituted YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Ruckman, Mark W.; Hepp, Aloysius F.

    1990-01-01

    The near-edge structure (XANES) of the Au L3 and Cu K edges of YBa2Au(0.3)Cu(2.7)O(7-delta) was studied. X ray diffraction suggests that Au goes on the Cu(1) site and XANES shows that this has little effect on the oxidation state of the remaining copper. The gold L3 edge develops a white line feature whose position lies between that of trivalent gold oxide (Au2O3) and monovalent potassium gold cyanide (KAu(CN)2) and whose intensity relative to the edge step is smaller than in the two reference compounds. The L3 EXAFS for Au in the superconductor resembles that of Au2O3. However, differences in the envelope of the Fourier filtered component for the first shell suggest that the local structure of the Au in the superconductor is not equivalent to Au2O3.

  4. K-edge XANES investigation of octakis(DMSO)lanthanoid(III) complexes in DMSO solution and solid iodides

    PubMed Central

    D’Angelo, Paola; Migliorati, Valentina; Spezia, Riccardo; De Panfilis, Simone; Persson, Ingmar; Zitolo, Andrea

    2014-01-01

    The potentiality of high energy XANES (X-ray absorption near edge structure) as a structural tool for lanthanoid-containing systems has been explored. The K-edge XANES spectra of La3+, Gd3+, and Lu3+ ions both in DMSO solution and solid octakis(DMSO) lanthanoid(III) iodides have been analysed. Although the K-edges of lanthanoids cover the energy range 38 (La) to 65 (Lu) keV, the large widths of the core hole states do not appreciably reduce the potential structural information of XANES data. We show that, for lanthanoid compounds, accurate structural parameters are obtained from the analysis of K-edge XANES signal if a deconvolution procedure is carried out. We found that in solid octakis(DMSO) lanthanoid(III) iodides the Ln3+ ions are coordinated by eight DMSO ligands arranged in a quite symmetric fashion. In DMSO solution the Ln3+ ions retain a regular eight-coordination structure and the coordination number does not change along the series. At variance with water the second coordination shell has been found to provide a negligible contribution to the XANES spectra of Ln3+ ions in DMSO solution. PMID:23657739

  5. K-edge XANES investigation of octakis(DMSO)lanthanoid(III) complexes in DMSO solution and solid iodides.

    PubMed

    D'Angelo, Paola; Migliorati, Valentina; Spezia, Riccardo; De Panfilis, Simone; Persson, Ingmar; Zitolo, Andrea

    2013-06-14

    The potential of high energy XANES (X-ray absorption near edge structure) as a tool for the structural analysis of lanthanoid-containing systems has been explored. The K-edge XANES spectra of La(3+), Gd(3+), and Lu(3+) ions both in DMSO solution and solid octakis(DMSO)lanthanoid(III) iodides have been analysed. Although the K-edges of lanthanoids cover the energy range of 38 (La) to 65 (Lu) keV, the large widths of the core hole states do not appreciably reduce the potential structural information of the XANES data. We show that, for lanthanoid compounds, accurate structural parameters are obtained from the analysis of K-edge XANES signals if a deconvolution procedure is carried out. We found that in solid octakis(DMSO)lanthanoid(III) iodides the Ln(3+) ions are coordinated by eight DMSO ligands arranged in a quite symmetric fashion. In DMSO solution the Ln(3+) ions retain a regular eight-coordination structure and the coordination number does not change along the series. In contrast to when in water the second coordination shell has been found to provide a negligible contribution to the XANES spectra of Ln(3+) ions in DMSO solution. PMID:23657739

  6. Probing the Orientation of Electrostatically Immobilized Protein G B1 by Time of Flight Secondary Ion Spectrometry, Sum Frequency Generation and Near-edge X-Ray Adsorption Fine Structure Spectroscopy

    PubMed Central

    Baio, Joe E.; Weidner, Tobias; Baugh, Loren; Gamble, Lara J.; Stayton, Patrick S.; Castner, David G.

    2011-01-01

    To fully develop techniques that provide an accurate description of protein structure at a surface, we must start with a relatively simple model system before moving on to increasingly complex systems. In this study, x-ray photoelectron spectroscopy (XPS), sum frequency generation spectroscopy (SFG), near-edge x-ray adsorption fine structure (NEXAFS) spectroscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to probe the orientation of Protein G B1 (6 kDa) immobilized onto both amine (NH3+) and carboxyl (COO−) functionalized gold. Previously, we have shown that we could successful control orientation of a similar Protein G fragment via a cysteine-maleimide bond. In this investigation, to induce opposite end-on orientations, a charge distribution was created within the Protein G B1 fragment by first substituting specific negatively charged amino acids with neutral amino acids and then immobilizing the protein onto two oppositely charged self-assembled monolayer (SAM) surfaces (NH3+ and COO−). Protein coverage, on both surfaces, was monitored by the change in the atomic % N, as determined by XPS. Spectral features within the SFG spectra, acquired for the protein adsorbed onto a NH3+-SAM surface, indicates that this electrostatic interaction does induce the protein to form an oriented monolayer on the SAM substrate. This corresponded to the polarization dependence of the spectral feature related to the NEXAFS N1s to π* transition of the β-sheet peptide bonds within the protein layer. ToF-SIMS data demonstrated a clear separation between the two samples based on the intensity differences of secondary ions stemming from amino acids located asymmetrically within Protein G B1 (Methionine: 62 and 105 m/z; Tyrosine: 107 and 137 m/z; Leucine: 86 m/z). For a more quantitative examination of orientation, we developed a ratio comparing the sum of the intensities of secondary-ions stemming from the amino acid residues at either end of the protein

  7. EXAFS and XANES analysis of plutonium and cerium edges from titanate ceramics for fissile materials disposal.

    SciTech Connect

    Fortner, J. A.; Kropf, A. J.; Bakel, A. J.; Hash, M. C.; Aase, S. B.; Buck, E. C.; Chamerlain, D. B.

    1999-11-16

    We report x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) spectra from the plutonium L{sub III} edge and XANES from the cerium L{sub II} edge in prototype titanate ceramic hosts. The titanate ceramics studied are based upon the hafnium-pyrochlore and zirconolite mineral structures and will serve as an immobilization host for surplus fissile materials, containing as much as 10 weight % fissile plutonium and 20 weight % (natural or depleted) uranium. Three ceramic formulations were studied: one employed cerium as a ''surrogate'' element, replacing both plutonium and uranium in the ceramic matrix, another formulation contained plutonium in a ''baseline'' ceramic formulation, and a third contained plutonium in a formulation representing a high-impurity plutonium stream. The cerium XANES from the surrogate ceramic clearly indicates a mixed III-IV oxidation state for the cerium. In contrast, XANES analysis of the two plutonium-bearing ceramics shows that the plutonium is present almost entirely as Pu(IV) and occupies the calcium site in the zirconolite and pyrochlore phases. The plutonium EXAFS real-space structure shows a strong second-shell peak, clearly distinct from that of PuO{sub 2}, with remarkably little difference in the plutonium crystal chemistry indicated between the baseline and high-impurity formulations.

  8. Multiple Scattering Approach to Polarization Dependence of F K-Edge XANES Spectra for Highly Oriented Polytetrafluoroethylene (PTFE) Thin Film

    SciTech Connect

    Nagamatsu, S.; Ono, M.; Kera, S.; Okudaira, K. K.; Fujikawa, T.; Ueno, N.

    2007-02-02

    The polarization dependence of F K-edge X-ray absorption near edge structure (XANES) spectra of highly-oriented thin-film of polytetrafluoroethylene (PTFE) has been analyzed by using multiple scattering theory. The spectra show clear polarization dependence due to the highly-oriented structure. The multiple scattering calculations reflects a local structure around an absorbing atom. The calculated results obtained by considering intermolecular-interactions are in good agreement with the observed polarization-dependence. We have also analyzed structural models of the radiation damaged PTFE films.

  9. B K-Edge XANES of Superstructural Units in Borate Glasses

    SciTech Connect

    Sipr, O.; Simunek, A.; Rocca, F.

    2007-02-02

    The potential of x-ray absorption near-edge structure (XANES) spectroscopy for studying medium range order in borate glasses is assessed by theoretical modelling of the spectra. B K edge XANES is calculated in case that B atoms are located in isolated BO3 and BO4 units and in case that B atom are located in superstructural units of 9-15 atoms. It is found that boroxol ring and diborate and ditriborate superstructural units give rise to spectra which differ from spectra obtained by a mere superposition of spectra of isolated BO3 and BO4 units. On the other hand, spectra of pentaborate and triborate units do not differ significantly from spectra of isolated BO3 and BO4.

  10. Spectral Analysis by XANES Reveals that GPNMB Influences the Chemical Composition of Intact Melanosomes

    SciTech Connect

    T Haraszti; C Trantow; A Hedberg-Buenz; M Grunze; M Anderson

    2011-12-31

    GPNMB is a unique melanosomal protein. Unlike many melanosomal proteins, GPNMB has not been associated with any forms of albinism, and it is unclear whether GPNMB has any direct influence on melanosomes. Here, melanosomes from congenic strains of C57BL/6J mice mutant for Gpnmb are compared to strain-matched controls using standard transmission electron microscopy and synchrotron-based X-ray absorption near-edge structure analysis (XANES). Whereas electron microscopy did not detect any ultrastructural changes in melanosomes lacking functional GPNMB, XANES uncovered multiple spectral phenotypes. These results directly demonstrate that GPNMB influences the chemical composition of melanosomes and more broadly illustrate the potential for using genetic approaches in combination with nano-imaging technologies to study organelle biology.

  11. The determination of dopant ion valence distributions in insulating crystals using XANES measurements.

    PubMed

    Hughes-Currie, Rosa B; Ivanovskikh, Konstantin V; R Wells, Jon-Paul; Reid, Michael F; Gordon, Robert A

    2016-04-01

    Ytterbium-doped wide-bandgap fluoride crystals CaF2, SrF2 and NaMgF3 have been measured using x-ray absorption near edge structure (XANES) on the L3 edge to determine the ratio of trivalent to divalent Yb ions present in the crystals. This study improves upon previous XANES measurements of dopant ion valency by taking into account the x-ray emission transition probabilities for the divalent and trivalent species instead of simply assuming that the relative concentrations may be determined by the ratio of the x-ray excitation band areas. Trivalent to divalent ratios as high as 5 are inferred even at low total dopant ion concentrations of 0.05 mol% Yb. PMID:26941175

  12. The determination of dopant ion valence distributions in insulating crystals using XANES measurements

    NASA Astrophysics Data System (ADS)

    Hughes-Currie, Rosa B.; Ivanovskikh, Konstantin V.; Wells, Jon-Paul R.; Reid, Michael F.; Gordon, Robert A.

    2016-04-01

    Ytterbium-doped wide-bandgap fluoride crystals CaF2, SrF2 and NaMgF3 have been measured using x-ray absorption near edge structure (XANES) on the L3 edge to determine the ratio of trivalent to divalent Yb ions present in the crystals. This study improves upon previous XANES measurements of dopant ion valency by taking into account the x-ray emission transition probabilities for the divalent and trivalent species instead of simply assuming that the relative concentrations may be determined by the ratio of the x-ray excitation band areas. Trivalent to divalent ratios as high as 5 are inferred even at low total dopant ion concentrations of 0.05 mol% Yb.

  13. The Atomic AXAFS and XANES Techniques as Applied to Heterogeneous Catalysis and Electrocatalysis

    SciTech Connect

    Ramaker, D.; Koningsberger, D

    2010-01-01

    X-Ray absorption spectroscopy (XAFS) is an attractive in situ and in operando technique. In recent years, the more conventional extended X-ray absorption fine structure (EXAFS) data analysis technique has been complemented by two newer analysis methods: the 'atomic' XAFS (AXAFS) technique, which analyzes the scattering from the absorber atom itself, and the {Delta}{mu} XANES technique, which uses a difference method to isolate the changes in the X-ray absorption near edge structure (XANES) due to adsorbates on a metal surface. With AXAFS it is possible to follow the electronic effect a support has on a metal particle; with {Delta}{mu} XANES it is possible to determine the adsorbate, the specific adsorption sites and adsorbate coverage on a metal catalyst. This unprecedented new information helps a great deal to unravel the complex kinetic mechanisms operating in working reactors or fuelcell systems. The fundamental principles and methodology for applying the AXAFS and {Delta}{mu} XANES techniques are given here, and then specific applications are summarized, including H adsorption on supported Pt in the gas phase, wateractivation at a Pt cathode and methanol oxidation at a Pt anode in an electrochemical cell, sulfur oxidation on Pt, and oxygenreduction on a Au/SnO{sub x} cathode. Finally, the future outlook for time and/or space resolved applications of these techniques is contemplated.

  14. Analyzing organic sulfur in coal/char: Integrated mild gasification/XANES methods. Technical report, 1 March--31 May 1994

    SciTech Connect

    Palmer, S.R.; Huffman, G.P.

    1994-09-01

    The overall goal of this study is to improve the understanding of sulfur in coals/chars via the use of combined advanced non-destructive and advanced destructive methods of sulfur analysis. This study combines selective oxidation, analytical pyrolysis, and sulfur X-ray Absorption Near Edge Structure Spectroscopy (XANES) analysis. Samples with a wide variety of sulfur contents, (0.63% to 4.40%) have been prepared for use in this study. This includes steam gasification chars, oxidized coals and desulfurized coals as well of the original unaltered coals. Mild pyrolysis and preliminary XANES data shows that the sulfur chemistry of gasification chars is significantly different from that of the original coals. Mild pyrolysis of the samples that were oxidized with peroxyacetic acid showed that the level of simple thiophene structures observed in the pyrolysis products declines with increasing levels of oxidation. Sulfur XANES spectra of treated samples showed various effects depending on the treatment severity. For the less severely treated samples (demineralization and solvent extraction), the XANES spectra were similar, although not identical, to the untreated coal spectra, whereas the more severe treatments (steam at 450 C; peroxyacetic acid at 25 C) showed preferential oxidation of one or more sulfur-bearing phases in the original coal. Additional samples have recently been examined by XANES and W-band EPR and the data is currently being processed and evaluated.

  15. Effect of particle size and adsorbates on the L{sub 3}, L{sub 2} and L{sub 1} x-ray absorption near edge structure of supported Pt nanoparaticles.

    SciTech Connect

    Lei, Y.; Jelic, J.; Nitsche, L. C.; Meyer, R.; Miller, J.

    2011-04-01

    Pt nano-particles from about 1 to 10 nm have been prepared on silica, alkali-silica, alumina, silica-alumina, carbon and SBA-15 supports. EXAFS spectra of the reduced catalysts in He show a contraction of the Pt-Pt bond distance as particle size is decreased below 3 nm. The bond length decreased as much as 0.13 {angstrom} for 1 nm Pt particles. Adsorption of CO and H{sub 2} lead to a increase in Pt-Pt bond distance to that near Pt foil, e.g., 2.77 {angstrom}. In addition to changes in the Pt bond distance with size, as the particle size decreases below about 5 nm there is a shift in the XANES to higher energy at the L{sub 3} edge, a decrease in intensity near the edge and an increase in intensity beyond the edge. We suggest these features correspond to effects of coordination (the decrease at the edge) and lattice contraction (the increase beyond the edge). At the L{sub 2} edge, there are only small shifts to higher energy at the edge. However, beyond the edge, there are large increases in intensity with decreasing particle size. At the L{sub 1} edge there are no changes in position or shape of the XANES spectra. Adsorption of CO and H{sub 2} also lead to changes in the L{sub 3} and L{sub 2} edges, however, no changes are observed at the L1 edge. Density Functional Theory and XANES calculations show that the trends in the experimental XANES can be explained in terms of the states available near the edge. Both CO and H{sub 2} adsorption result in a depletion of states at the Fermi level but the creation of anti-bonding states above the Fermi level which give rise to intensity increases beyond the edge.

  16. XANES studies of oxidation states of sulfur in aquatic and soil humic substances

    SciTech Connect

    Xia, K.; Weesner, F.; Bleam, W.F.; Helmke, P.A.; Bloom, P.R.; Skyllberg, U.L.

    1998-09-01

    Sulfur K-edge x-ray absorption near-edge structure spectroscopy (XANES) was used to identify multiple organic S oxidation states in aquatic and soil humic substances. The XANES results suggest that S in humic substances exists in four major oxidation groups similar to sulfate ester, sulfonate, sulfoxide, and thiol-sulfide. Thiol S cannot be separated from sulfide X and must be considered as a single thiol-sulfide peak. The second derivative spectra suggest the existence of thiophene and sulfone S. The relative quantities of each major S form in humic samples were estimated based on the integrated cross section of each s {r_arrow} p transition peak corresponding to different S oxidation states in the S K-edge XANES spectra. The XANES results of the four humic samples used in this study appear to reflect the environmental settings where the humic substances originally formed. The percentage of the most reduced organic S (thiol-sulfide and possibly thiophene) in humic substances follows the sequence:aquatic samples > organic soil sample > mineral soil sample. The percentage of most oxidized S (sulfate group) was the greatest in the humic substance from a mineral soil and the lowest in the aquatic humic substances.

  17. Combined Carbon, Nitrogen, and Oxygen XANES Spectroscopy on Hydrated and Anhydrous Interplanetary Dust Particles

    NASA Technical Reports Server (NTRS)

    Feser, M.; Wirick, S.; Flynn, G. J.; Keller, L. P.

    2003-01-01

    Interplanetary dust particles (IDPs) collected from the Earth s stratosphere generally contain percent-level concentrations of organic matter. This organic matter in IDPs is important for several reasons: 1) some IDPs contain interstellar organic matter, identified by high D/H or N-15, providing the opportunity to characterize this interstellar material, 2) comparison of the organic matter in anhydrous IDPs to that in hydrated IDPs can help establish the effects of parent body aqueous alteration, and, 3) IDPs are believed to have delivered to the surface of the early Earth pre-biotic organic matter important for the origin of life. X-Ray Absorption Near-Edge Structure (XANES) spectroscopy provides information on the functional groups present in a sample, and XANES can be performed on the nano-scale, comparable to the size of some of the sub-units of the IDPs. The energies of the XANES transitions are diagnostic of the type of bonding of the C, N, and O, allowing identification of the functional groups present in the sample. As part of our ongoing effort to characterize the organic matter in the IDPs, we have performed carbon- and oxygen- and the first nitrogen-XANES spectroscopy on two IDPs and acid-insoluble residue from the CM2 meteorite Murchison.

  18. Arsenic speciation and phytoavailability in contaminated soils using a sequential extraction procedure and XANES spectroscopy.

    PubMed

    Niazi, Nabeel K; Singh, Balwant; Shah, Pushan

    2011-09-01

    In this study, a sequential extraction procedure (SEP) and X-ray absorption near edge structure (XANES) spectroscopy were used to determine the solid-phase speciation and phytoavailability of arsenic (As) of historically contaminated soils from As containing pesticides and herbicides and soils spiked with As in the laboratory. Brassica juncea was grown in the contaminated soils to measure plant available As in a glasshouse experiment. Arsenic associated with amorphous Fe oxides was found to be the dominant phase using both SEP and XANES spectroscopy. Arsenic predominantly existed in arsenate (As(V)) form in the soils; in a few samples As was also present in arsenite (As(III)) form or in scorodite mineral. Arsenic concentration in shoots showed significant (p < 0.001-0.05) correlations with the exchangeable As (r = 0.85), and amorphous Fe oxides associated As evaluated by the SEP (r = 0.67), and As associated with amorphous Fe oxides as determined by XANES spectroscopy (r = 0.51). The results show that As in both fractions was readily available for plant uptake and may pose a potential risk to the environment. The combination of SEP and XANES spectroscopy allowed us the quantitative speciation of As in the contaminated soils and the identification of valence and mineral forms of As. Such detailed knowledge on As speciation and availability is vital for management and rehabilitation of As-contaminated soils. PMID:21797214

  19. Characterization of Phosphorus Species in Biosolids and Manures Using XANES Spectroscopy

    SciTech Connect

    Shober,A.; Hesterberg, D.; Sims, J.; Gardner, S.

    2006-01-01

    Received for publication March 10, 2006. Identification of the chemical P species in biosolids or manures will improve our understanding of the long-term potential for P loss when these materials are land applied. The objectives of this study were to determine the P species in dairy manures, poultry litters, and biosolids using X-ray absorption near-edge structure (XANES) spectroscopy and to determine if chemical fractionation techniques can provide useful information when interpreted based on the results of more definitive P speciation studies. Our XANES fitting results indicated that the predominant forms of P in organic P sources included hydroxylapatite, PO{sub 4} sorbed to Al hydroxides, and phytic acid in lime-stabilized biosolids and manures; hydroxylapatite, PO{sub 4} sorbed on ferrihydrite, and phytic acid in lime- and Fe-treated biosolids; and PO{sub 4} sorbed on ferrihydrite, hydroxylapatite, {beta}-tricalcium phosphate ({beta}-TCP), and often PO{sub 4} sorbed to Al hydroxides in Fe-treated and digested biosolids. Strong relationships existed between the proportions of XANES PO{sub 4} sorbed to Al hydroxides and NH{sub 4}Cl- + NH{sub 4}F-extractable P, XANES PO{sub 4} sorbed to ferrihydrite + phytic acid and NaOH-extractable P, and XANES hydroxylapatite + {beta}-TCP and dithionite-citrate-bicarbonate (DCB)- + H{sub 2}SO{sub 4}-extractable P ({gamma}{sup 2} = 0.67 [P = 0.01], 0.78 [P = 0.01], and 0.89 [P = 0.001], respectively). Our XANES fitting results can be used to make predictions about long-term solubility of P when biosolids and manures are land applied. Fractionation techniques indicate that there are differences in the forms of P in these materials but should be interpreted based on P speciation data obtained using more advanced analytical tools.

  20. The Electronic Properties and L3 XANES of Au and Nano-Au

    SciTech Connect

    Yiu, Y.M.; Zhang, P.; Sham, T.K.

    2004-04-20

    The electronic properties of Au crystal and nano Au have been investigated by theory and experiment. Molecularly capped nano-Au was synthesized using the two-phase method. Au nano-particles have been characterized by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). They retain the fcc crystal structure. Their sizes have been determined to be in a range from 5.5 nm to 1.7 nm. The L3 X-ray Absorption Near Edge Structure (XANES) of nano-Au and Au foil have been recorded using synchrotron radiation, and examined by theoretical calculation based on the first principles. Both theory and experiment show that the nano-Au particles have essentially all the Au L3 XANES features of bulk Au in the near edge region with less pronounced resonance peaks. It is also shown that nano Au exhibits lower 4f binding energy than bulk Au in good agreement with quantum confined Au systems reported previously.

  1. XANES study of Fe-implanted strontium titanate

    SciTech Connect

    Lobacheva, O.; Goncharova, L. V.; Chavarha, M.; Sham, T. K.

    2014-03-31

    Properties of strontium titanate SrTiO{sub 3} (STO) depend to a great extent on the substitutional dopants and defects of crystal structure. The ion beam implantation method was used for doping STO (001) crystals with Fe at different doses. Implanted samples were then annealed at 350°C in oxygen to induce recrystallization and remove oxygen vacancies produced during ion implantation process. The effect of Fe doping and post-implantation annealing was studied by X-ray Absorption Near Edge Spectroscopy (XANES) method and Superconducting Quantum Interference Device (SQUID). XANES allowed to monitor the change in structure of STO crystals and in the local environment of Fe following the implantation and annealing steps. SQUID measurements revealed correlation between magnetic moment and Fe implantation dose. Ferromagnetic hysteresis was observed on selected Fe-implanted STO at 5 K. The observed magnetic properties can be correlated with the several Fe oxide phases in addition to the presence of O/Ti vacancies.

  2. In Situ XANES Study of CuO/TiO2 Thin Films During Photodegradation of Methylene Blue

    SciTech Connect

    Hsiung Tungli; Wang, H. Paul; Wei Yuling

    2007-02-02

    Speciation of copper in the CuO/TiO2 thin film (synthesized by the doctor-blade deposition method) during photocatalytic decomposition of methylene blue has been studied by in situ X-ray absorption near-edge structural (XANES) spectroscopy. During the UV/VIS radiation (90 min), in the presence of methylene blue, a decrease of Cu(II) and an increases of Cu(0) and Cu(I) fractions in the CuO/TiO2 thin film are observed by in situ XANES. The r-space Fourier transformation EXAFS (extend X-ray absorption fine structural) spectra also show that the bond distance of Cu-O in the thin film is decreased by 0.03 A during photocatalytic degradation of methylene blue.

  3. Synchrotron x-ray fluorescence microprobe: Quantification and mapping of mixed valence state samples using micro-XANES

    SciTech Connect

    Sutton, S.R. ); Bajt, S. Department of Applied Science, Brookhaven National Laboratory, Upton, New York 11973 ); Delaney, J. ); Schulze, D. ); Tokunaga, T. )

    1995-02-01

    The synchrotron x-ray fluorescence microprobe is a valuable instrument for quantification and mapping of mixed valence state samples with high spatial resolution and elemental sensitivity. A method has been developed for quantifying the proportions of Fe[sup 2+] and Fe[sup 3+] with 100 [mu]m spatial resolution and better than 100 ppm sensitivity using x-ray absorption near-edge structure (XANES). Applications of valence state mapping have been made to selenium in water-saturated sediments and manganese associated with wheat roots attacked by the take-all fungus.

  4. XANES mapping of organic sulfate in three scleractinian coral skeletons

    NASA Astrophysics Data System (ADS)

    Cuif, Jean-Pierre; Dauphin, Yannicke; Doucet, Jean; Salome, Murielle; Susini, Jean

    2003-01-01

    The presence and localization of organic sulfate within coral skeletons are studied by using X-ray absorption near edge structure spectroscopy (XANES) fluorescence. XANES spectra are recorded from four reference sulfur-bearing organic molecules: three amino acids (H-S-C bonds in cysteine; C-S-C bonds in methionine; one disulfide bond C-S-S-C bonds in cystine) and a sulfated sugar (C-SO 4 bonds in chondroitin sulfate). Spectral responses of three coral skeletons show that the sulfated form is extremely dominant in coral aragonite, and practically exclusive within both centres of calcification and the surrounding fibrous tissues of coral septa. Mapping of S-sulfate concentrations in centres and fibres gives us direct evidence of high concentration of organic sulfate in centres of calcification. Additionally, a banding pattern of S-sulfate is visible in fibrous part of the coral septa, evidencing a biochemical zonation that corresponds to the step-by-step growth of fibres.

  5. Experimental station for laser-based picosecond time-resolved x-ray absorption near-edge spectroscopy

    NASA Astrophysics Data System (ADS)

    Dorchies, F.; Fedorov, N.; Lecherbourg, L.

    2015-07-01

    We present an experimental station designed for time-resolved X-ray Absorption Near-Edge Spectroscopy (XANES). It is based on ultrashort laser-plasma x-ray pulses generated from a table-top 100 mJ-class laser at 10 Hz repetition rate. A high transmission (10%-20%) x-ray beam line transport using polycapillary optics allows us to set the sample in an independent vacuum chamber, providing high flexibility over a wide spectral range from 0.5 up to 4 keV. Some XANES spectra are presented, demonstrating 1% noise level in only ˜1 mn and ˜100 cumulated laser shots. Time-resolved measurements are reported, indicating that the time resolution of the entire experimental station is 3.3 ± 0.6 ps rms.

  6. Experimental station for laser-based picosecond time-resolved x-ray absorption near-edge spectroscopy

    SciTech Connect

    Dorchies, F. Fedorov, N.; Lecherbourg, L.

    2015-07-15

    We present an experimental station designed for time-resolved X-ray Absorption Near-Edge Spectroscopy (XANES). It is based on ultrashort laser-plasma x-ray pulses generated from a table-top 100 mJ-class laser at 10 Hz repetition rate. A high transmission (10%–20%) x-ray beam line transport using polycapillary optics allows us to set the sample in an independent vacuum chamber, providing high flexibility over a wide spectral range from 0.5 up to 4 keV. Some XANES spectra are presented, demonstrating 1% noise level in only ∼1 mn and ∼100 cumulated laser shots. Time-resolved measurements are reported, indicating that the time resolution of the entire experimental station is 3.3 ± 0.6 ps rms.

  7. Real Time Observation of X-ray-Induced Surface Modification Using Simultaneous XANES and XEOL-XANES

    PubMed Central

    2013-01-01

    In experiments preliminary to the design of an X-ray-excited optical luminescence (XEOL)-based chemical mapping tool we have used X-ray micro (4.5 × 5.2 μm) and macro (1 × 6 mm) beams with similar total fluxes to assess the effects of a high flux density beam of X-rays at energies close to an absorption edge on inorganic surfaces in air. The near surface composition of corroded cupreous alloys was analyzed using parallel X-ray and optical photoemission channels to collect X-ray absorption near-edge structure (XANES) data at the Cu K edge. The X-ray fluorescence channel is characteristic of the composition averages over several micrometers into the surface, whereas the optical channel is surface specific to about 200 nm. While the X-ray fluorescence data were mostly insensitive to the X-ray dose, the XEOL-XANES data from the microbeam showed significant dose-dependent changes to the superficial region, including surface cleaning, changes in the oxidation state of the copper, and destruction of surface compounds responsible for pre-edge fluorescence or phosphorescence in the visible. In one case, there was evidence that the lead phase in a bronze had melted. Conversely, data from the macrobeam were stable over several hours. Apart from localized heating effects, the microbeam damage is probably associated with the O3 loading of the surface and increased reaction rate with atmospheric water vapor. PMID:24044633

  8. PROCEEDINGS ON SYNCHROTRON RADIATION: Transfer characterization of sulfur from coal-burning emission to plant leaves by PIXE and XANES

    NASA Astrophysics Data System (ADS)

    Bao, Liang-Man; Zhang, Gui-Lin; Zhang, Yuan-Xim; Li, Yan; Lin, Jun; Liu, Wei; Cao, Qing-Chen; Zhao, Yi-Dong; Ma, Chen-Yan; Han, Yong

    2009-11-01

    The impact of coal-burning emission on sulfur in camphor leaves was investigated using Proton Induced X-ray Emission (PIXE) and synchrotron radiation technique X-ray Absorption Near-Edge Structure (XANES) spectroscopy. The PIXE results show that the sulfur concentrations in the leaves collected at the polluted site are significantly higher than those in controls. The Sulfur XANES spectra show the presence of organic (disulfides, thiols, thioethers, sulfonates and sulfoxides) and inorganic sulfur (sulfates) in the leaves. The inorganic sulfur in the leaves of camphor tree polluted by coal combustion is 15% more than that of the control site. The results suggest that the long-term coal-burning pollution resulted in an enhanced content of the total sulfur and sulfate in the leaves, and the uptake of sulfur by leaves had exceeded the metabolic requirement of plants and the excess of sulfur was stored as SO2-4. It can monitor the sulfur pollution in atmosphere.

  9. Diamond xenolith and matrix organic matter in the Sutter's Mill meteorite measured by C-XANES

    NASA Astrophysics Data System (ADS)

    Kebukawa, Yoko; Zolensky, Michael E.; Kilcoyne, A. L. David; Rahman, Zia; Jenniskens, Peter; Cody, George D.

    2014-11-01

    The Sutter's Mill (SM) meteorite fell in El Dorado County, California, on April 22, 2012. This meteorite is a regolith breccia composed of CM chondrite material and at least one xenolithic phase: oldhamite. The meteorite studied here, SM2 (subsample 5), was one of three meteorites collected before it rained extensively on the debris site, thus preserving the original asteroid regolith mineralogy. Two relatively large (10 μm sized) possible diamond grains were observed in SM2-5 surrounded by fine-grained matrix. In the present work, we analyzed a focused ion beam (FIB) milled thin section that transected a region containing these two potential diamond grains as well as the surrounding fine-grained matrix employing carbon and nitrogen X-ray absorption near-edge structure (C-XANES and N-XANES) spectroscopy using a scanning transmission X-ray microscope (STXM) (Beamline 5.3.2 at the Advanced Light Source, Lawrence Berkeley National Laboratory). The STXM analysis revealed that the matrix of SM2-5 contains C-rich grains, possibly organic nanoglobules. A single carbonate grain was also detected. The C-XANES spectrum of the matrix is similar to that of insoluble organic matter (IOM) found in other CM chondrites. However, no significant nitrogen-bearing functional groups were observed with N-XANES. One of the possible diamond grains contains a Ca-bearing inclusion that is not carbonate. C-XANES features of the diamond-edges suggest that the diamond might have formed by the CVD process, or in a high-temperature and -pressure environment in the interior of a much larger parent body.

  10. Determination of Chemical States of Mercury on Activated Carbon Using XANES

    SciTech Connect

    Takaoka, Masaki; Takeda, Nobuo; Oshita, Kazuyuki; Yamamoto, Takashi; Tanaka, Tsunehiro; Uruga, Tomoya

    2007-02-02

    Although the adsorption of mercury vapor onto activated carbon is a widely used technology to prevent environmental release, the adsorption mechanism is not clearly understood. In this study, we determined the chemical states of mercury on two kinds of activated carbon using X-ray absorption near-edge spectroscopy (XANES) to elucidate the adsorption mechanism. The adsorption experiments of elemental mercury onto activated carbon were conducted under air and nitrogen atmospheres at temperatures of 20 and 160 deg. C. Two types of activated carbon were prepared. X-ray absorption fine structure (XAFS) measurements were carried out on beamline BL01B1 at SPring-8. Hg-LIII edge XANES spectra suggested that chemical adsorption of elemental mercury on the activated carbon occurred in the 20-160 deg. C temperature range. According to the XANES spectra, a difference occurred in the chemical states of mercury between AC no. 1 and AC no. 2. The Hg XANES spectra on AC no. 1 were similar to those of Hg2Cl2 and HgS, and the Hg XANES spectra on AC no. 2 were similar to that of HgO, which suggested that nitric acid treatment removed sulfur from AC no. 1 and functional groups that were strong oxidizers on the surface of AC no. 2 created HgO. According to the EXAFS oscillation, a difference occurred in the chemical states of mercury on AC no. 1 between 20 and 160 deg. C. We found that impurities and oxidant functional groups on activated carbon play key roles in mercury adsorption.

  11. Characterization of extracellular polymeric substances in the biofilms of typical bacteria by the sulfur K-edge XANES spectroscopy.

    PubMed

    Lin, Huirong; Ye, Chengsong; Lv, Lu; Zheng, Clark Renjun; Zhang, Shenghua; Zheng, Lei; Zhao, Yidong; Yu, Xin

    2014-08-01

    A combined approach of physicochemical extraction and sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy was applied to characterize the extracellular polymeric substances (EPS) of typical bacterial biofilms in this study. Physicochemical analysis showed variation of the contents of DNA, polysaccharide and protein in different fractions of EPS in different mediums. The sulfur K-edge XANES analysis yielded a variety of spectra. Spectral fitting of the XANES spectra utilizing a large set of model compounds showed that there was more reduced sulfur in both LB-EPS (loosely bound EPS) and TB-EPS (tightly bound EPS) of all the biofilms in LB medium than in R2A medium. More oxidized sulfur was identified in LB-EPS than that in TB-EPS, suggesting different niches and physiological heterogeneity in the biofilms. Our results suggested that the sulfur K-edge XANES can be a useful tool to analyze the sulfur speciation in EPS of biofilms. PMID:25108733

  12. XANES Identification of Plutonium Speciation in RFETS Samples

    SciTech Connect

    LoPresti, V.; Conradson, S.D.; Clark, D.L.

    2009-06-03

    Using primarily X-ray absorption near edge spectroscopy (XANES) with standards run in tandem with samples, probable plutonium speciation was determined for 13 samples from contaminated soil, acid-splash or fire-deposition building interior surfaces, or asphalt pads from the Rocky Flats Environmental Technology Site (RFETS). Save for extreme oxidizing situations, all other samples were found to be of Pu(IV) speciation, supporting the supposition that such contamination is less likely to show mobility off site. EXAFS analysis conducted on two of the 13 samples supported the validity of the XANES features employed as determinants of the plutonium valence.

  13. Ge L{sub 3}-edge x-ray absorption near-edge structure study of structural changes accompanying conductivity drift in the amorphous phase of Ge{sub 2}Sb{sub 2}Te{sub 5}

    SciTech Connect

    Mitrofanov, K. V.; Kolobov, A. V. Fons, P.; Wang, X.; Tominaga, J.; Tamenori, Y.; Uruga, T.; Ciocchini, N.; Ielmini, D.

    2014-05-07

    A gradual uncontrollable increase in the resistivity of the amorphous phase of phase-change alloys, such as Ge{sub 2}Sb{sub 2}Te{sub 5}, known as drift, is a serious technological issue for application of phase-change memory. While it has been proposed that drift is related to structural relaxation, no direct structural results have been reported so far. Here, we report the results of Ge L{sub 3}-edge x-ray absorption measurements that suggest that the drift in electrical conductivity is associated with the gradual conversion of tetrahedrally coordinated Ge sites into pyramidal sites, while the system still remains in the amorphous phase. Based on electronic configuration arguments, we propose that during this process, which is governed by the existence of lone-pair electrons, the concentration of free carriers in the system decreases resulting in an increase in resistance despite the structural relaxation towards the crystalline phase.

  14. XANES analysis of organic residues produced from the UV irradiation of astrophysical ice analogs

    NASA Astrophysics Data System (ADS)

    Nuevo, M.; Milam, S. N.; Sandford, S. A.; De Gregorio, B. T.; Cody, G. D.; Kilcoyne, A. L. D.

    2011-09-01

    Organic residues formed in the laboratory from the ultraviolet (UV) photo-irradiation or ion bombardment of astrophysical ice analogs have been extensively studied for the last 15 years with a broad suite of techniques, including infrared (IR) and UV spectroscopies, as well as mass spectrometry. Analyses of these materials show that they consist of complex mixtures of organic compounds stable at room temperature, mostly soluble, that have not been fully characterized. However, the hydrolysis products of these residues have been partly identified using chromatography techniques, which indicate that they contain molecular precursors of prebiotic interest such as amino acids, nitrile-bearing compounds, and amphiphilic compounds. In this study, we present the first X-ray absorption near-edge structure (XANES) spectroscopy measurements of three organic residues made from the UV irradiation of ices having different starting compositions. XANES spectra confirm the presence of different chemical functions in these residues, and indicate that they are rich in nitrogen- and oxygen-bearing species. These data can be compared with XANES measurements of extraterrestrial materials. Finally, this study also shows how soft X rays can alter the chemical composition of samples.

  15. XANES Analysis of Organic Residues Produced from the UV Irradiation of Astrophysical Ice Analogs

    NASA Technical Reports Server (NTRS)

    Nuevo, M.; Milam, S N.; Sandford, S A.; De Gregorio, B T.; Cody, G D.; Kilcoyne, A L.

    2011-01-01

    Organic residues formed in the laboratory from the ultraviolet (UV) photo-irradiation or ion bombardment of astrophysical ice analogs have been extensively studied for the last 15 years with a broad suite of techniques, including infrared (IR) and UV spectroscopies, as well as mass spectrometry. Analyses of these materials show that they consist of complex mixtures of organic compounds stable at room temperature, mostly soluble, that have not been fully characterized. However, the hydrolysis products of these residues have been partly identified using chromatography techniques, which indicate that they contain molecular precursors of prebiotic interest such as amino acids, nitrile-bearing compounds, and amphiphilic compounds. In this study, we present the first X-ray absorption near-edge structure (XANES) spectroscopy measurements of three organic residues made from the UV irradiation of ices having different starting compositions. XANES spectra confirm the presence of different chemical functions in these residues, and indicate that they are rich in nitrogenand oxygen-bearing species. These data can be compared with XANES measurements of extraterrestrial materials. Finally, this study also shows how soft X rays can alter the chemical composition of samples.

  16. General Method for Determination of the Surface Composition in Bimetallic Nanoparticle Catalysts from the L Edge X-ray Absorption Near-Edge Spectra

    SciTech Connect

    Wu, Tiapin; Childers, David; Gomez, Carolina; Karim, Ayman M.; Schweitzer, Neil; Kropf, Arthur; Wang, Hui; Bolin, Trudy B.; Hu, Yongfeng; Kovarik, Libor; Meyer, Randall; Miller, Jeffrey T.

    2012-10-08

    Bimetallic PtPd on silica nano-particle catalysts have been synthesized and their average structure determined by Pt L3 and Pd K-edge extended X-ray absorption finestructure (EXAFS) spectroscopy. The bimetallic structure is confirmed from elemental line scans by STEM for the individual 1-2 nm sized particles. A general method is described to determine the surface composition in bimetallic nanoparticles even when both metals adsorb, for example, CO. By measuring the change in the L3 X-ray absorption near-edge structure (XANES) spectra with and without CO in bimetallic particles and comparing these changes to those in monometallic particles of known size the fraction of surface atoms can be determined. The turnover rates (TOR) and neopentane hydrogenolysis and isomerization selectivities based on the surface composition suggest that the catalytic and spectroscopic properties are different from those in monometallic nano-particle catalysts. At the same neo-pentane conversion, the isomerization selectivity is higher for the PtPd catalyst while the TOR is lower than that of both Pt and Pd. As with the catalytic performance, the infrared spectra of adsorbed CO are not a linear combination of the spectra on monometallic catalysts. Density functional theory calculations indicate that the Pt-CO adsorption enthalpy increases while the Pd-CO bond energy decreases. The ability to determine the surface composition allows for a better understanding of the spectroscopic and catalytic properties of bimetallic nanoparticle catalysts.

  17. Using Fluorescence XANES Measurement to Correct the Content of Hexavalent Chromium in Chromate Conversion Coatings Determined by Diphenyl Carbazide Color Test

    SciTech Connect

    Nishino, Junichi; Ofuchi, Hironori; Taniguchi, Yosuke; Honma, Tetsuo; Sekikawa, Toshikazu; Otani, Haruka; Bando, Akio

    2007-01-19

    The Restriction of the use of certain Hazardous Substances (RoHS) directive will take effect on July 1 of this year. From that date, the use of chromate conversion coatings containing hexavalent chromium will not be permitted. By comparing the concentration of Cr6+ determined by the diphenyl carbazide color test and by fluorescence XANES (X-Ray Absorption Near Edge Structure) measurement, we can correct for the Cr6+ content of the color test. This will enable the use of the diphenyl carbazide color test to check product shipments in compliance with the RoHS directive.

  18. Experimental and theoretical XANES of CdS{sub x}Se{sub 1−x} nanostructures

    SciTech Connect

    Yiu, Y. M.; Sham, T. K.; Murphy, M. W.; Liu, L.; Hu, Y.

    2014-03-31

    The morphology and electronic properties of the CdS{sub x}Se{sub 1−x} nanostructures with varying alloy compositions have been acquired experimentally by X-ray Absorption Near-Edge Structures (XANES) at the Cd, Se and S K-edge and L{sub 3,2}-edges. The theoretical XANES spectra have been calculated using the density functional approach. It is found that the optical band-gap emission of these CdS{sub x}Se{sub 1−x} nano-ribbons can be tuned to the range between that of pure CdS (2.43 eV) and CdSe (1.74 eV) by changing the S and Se ratio. This gradual shift in (optical and structural) properties from CdS character to CdSe character is also seen in the electronic structures. The densities of states and band structures show that with the addition of Se replacing S in CdS, the band gap shrinks. The K and L{sub 3,2} edges of Cd, Se, and S of the XANES structures of both the CdS and CdSe in B4 (wurtzite) and B3 (cubic zinc-blende) structures have been calculated and compared.

  19. XANES: observation of quantum confinement in the conduction band of colloidal PbS quantum dots

    NASA Astrophysics Data System (ADS)

    Demchenko, I. N.; Chernyshova, M.; He, X.; Minikayev, R.; Syryanyy, Y.; Derkachova, A.; Derkachov, G.; Stolte, W. C.; Piskorska-Hommel, E.; Reszka, A.; Liang, H.

    2013-04-01

    The presented investigations aimed at development of inexpensive method for synthesized materials suitable for utilization of solar energy. This important issue was addressed by focusing, mainly, on electronic local structure studies with supporting x-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis of colloidal galena nano-particles (NPs) and quantum dots (QDs) synthesized using wet chemistry under microwave irradiation. Performed x-ray absorption near edge structure (XANES) analysis revealed an evidence of quantum confinement for the sample with QDs, where the bottom of the conduction band was shifted to higher energy. The QDs were found to be passivated with oxides at the surface. Existence of sulfate/sulfite and thiosulfate species in pure PbS and QDs, respectively, was identified.

  20. Structure and Composition of Cu Doped CdSe Nanocrystals Using Soft X-ray Absorption Spectroscopy

    SciTech Connect

    Meulenberg, R W; van Buuren, T; Hanif, K M; Willey, T M; Strouse, G F; Terminello, L J

    2004-06-04

    The local structure and composition of Cu ions dispersed in CdSe nanocrystals is examined using soft x-ray absorption near edge spectroscopy (XANES). Using Cu L-edge XANES and X-ray photoelectron measurements (XPS), we find that the Cu ions exist in the Cu(I) oxidation state. We also find that the observed Cu L-edge XANES signal is directly proportional to the molar percent of Cu present in our final material. Se L-edge XANES indicates changes in the Se density of states with Cu doping, due to a chemical bonding effect, and supports a statistical doping mechanism. Photoluminescence (PL) measurements indicate the Cu ions may act as deep electron traps. We show that XANES, XPS, and PL are a powerful combination of methods to study the electronic and chemical structure of dopants in nanostructured materials.

  1. Combining µXANES and µXRD mapping to analyse the heterogeneity in calcium carbonate granules excreted by the earthworm Lumbricus terrestris.

    PubMed

    Brinza, Loredana; Schofield, Paul F; Hodson, Mark E; Weller, Sophie; Ignatyev, Konstantin; Geraki, Kalotina; Quinn, Paul D; Mosselmans, J Frederick W

    2014-01-01

    The use of fluorescence full spectral micro-X-ray absorption near-edge structureXANES) mapping is becoming more widespread in the hard energy regime. This experimental method using the Ca K-edge combined with micro-X-ray diffraction (µXRD) mapping of the same sample has been enabled on beamline I18 at Diamond Light Source. This combined approach has been used to probe both long- and short-range order in calcium carbonate granules produced by the earthworm Lumbricus terrestris. In granules produced by earthworms cultured in a control artificial soil, calcite and vaterite are observed in the granules. However, granules produced by earthworms cultivated in the same artificial soil amended with 500 p.p.m. Mg also contain an aragonite. The two techniques, µXRD and µXANES, probe different sample volumes but there is good agreement in the phase maps produced. PMID:24365942

  2. µ-XANES AND µ-XRF INVESTIGATIONS OF METAL BINDING MECHANISMS IN BIOSOLIDS

    EPA Science Inventory

    Micro-X-ray fluorescence (µ-XRF) microprobe analysis and micro-X-ray absorption near edge spectroscopy (µ-XANES) were employed to identify Fe and Mn phases and their association with selected toxic elements in two biosolids (limed composted and Nu-Earth) containing low ...

  3. Evaluation of iron-containing carbon nanotubes by near edge X-ray absorption technique

    NASA Astrophysics Data System (ADS)

    Osorio, A. G.; Bergmann, C. P.

    2015-10-01

    The synthesis of carbon nanotubes (CNTs) via Chemical Vapor Deposition method with ferrocene results in CNTs filled with Fe-containing nanoparticles. The present work proposes a novel route to characterize the Fe phases in CNTs inherent to the synthesis process. CNTs were synthesized and, afterwards, the CNTs were heat treated at 1000 °C for 20 min in an inert atmosphere during a thermogravimetric experiment. X-Ray Absorption Spectroscopy (XAS) experiments were performed on the CNTs before and after the heat treatment and, also, during the heat treatment, e.g., in situ tests were performed while several Near-Edge X-Ray Absorption (XANES) spectra were collected during the heating of the samples. The XAS technique was successfully applied to evaluate the phases encapsulated by CNTs. Phase transformations of the Fe-based nanoparticles were also observed from iron carbide to metallic iron when the in situ experiments were performed. Results also indicated that the applied synthesis method guarantees that Fe phases are not oxidize. In addition, the results show that heat treatment under inert atmosphere can control which phase remains encapsulated by the CNTs.

  4. Analyzing organic sulfur in coal/char: Integrated mild degradation/XANES methods. Final technical report, September 1, 1993--November 30, 1994

    SciTech Connect

    Palmer, S.R.; Huffman, G.P.

    1994-12-31

    The overall goal of this study is to improve the understanding of sulfur in coals/chars via the use of combined advanced nondestructive and advanced destructive methods of sulfur analysis. This study combines selective oxidation, analytical pyrolysis, and sulfur X-ray Absorption Near Edge Structure Spectroscopy (XANES) analysis. Samples with a wide variety of sulfur contents, (0.63%--4.40%) have been prepared for use in this study. This includes steam gasification chars, oxidized coals and desulfurized coals as well of the original unaltered coals. Mild pyrolysis and XANES data shows that the sulfur chemistry of gasification chars is significantly different from that of the original coals. Mild pyrolysis of the samples that were oxidized with peroxyacetic acid showed that the level of simple thiophene structures observed in the pyrolysis products declines with increasing levels of oxidation. Sulfur XANES spectra of treated samples showed various effects depending on the treatment severity. The XANES spectra of less severely treated samples were similar, although not identical, to the untreated coal spectra. XANES of gasification chars indicated conversion of pyrite to pyrrhotite, removal of organic sulfide sulfur and dissolution of soluble inorganic sulfur species during gasification. Mild oxidation with peroxyacetic acid results in preferential oxidation of sulfide forms before thiophene forms but increasing oxidation severity leads to virtually all sulfur species being oxidized. Good agreement between W-band EPR and XANES data for aromatic sulfur contents were obtained. The TPR analysis of coal indicated that organic sulfur was present as alkyl-aryl sulfide, aryl-aryl sulfides, simple thiophenes and condensed thiophenes. TPR shows that non-thiophenic compounds are removed by PAA oxidation, and that the longer the oxidation is performed the greater is the removal of non-thiophenic sulfur structures.

  5. Determination of phosphorus speciation in dairy manure using XRD and XANES spectroscopy.

    PubMed

    Güngör, Kerem; Jürgensen, Astrid; Karthikeyan, K G

    2007-01-01

    Intensive manure application is an important source of diffuse phosphorus (P) pollution. Phosphorus availability from animal manure is influenced by its chemical speciation. The major objective of this study was to investigate the P speciation in raw and anaerobically digested dairy manure with an emphasis on the calcium (Ca) and magnesium (Mg) phosphate phases. Influent and effluent from an on-farm digester in Wisconsin were sampled and sieved, and the 25 to 53 microm size fraction was dried for X-ray powder diffraction (XRD) and P K-edge X-ray absorption near edge structure (XANES) analyses. Struvite (MgNH4PO4.6H2O) was identified in both the raw (influent) and anaerobically digested (effluent) manure using XRD. Qualitative analysis of P K-edge XANES spectra indicated that the Ca orthophosphate phases, except dicalcium phosphate anhydrous (DCPA) or monetite (CaHPO4), were not abundant in dairy manure. Linear combination fitting (LCF) of the P standard compounds showed that 57.0 and 43.0% of P was associated with DCPA and struvite, respectively, in the raw manure. In the anaerobically digested sample, 78.2% of P was present as struvite and 21.8% of P was associated with hydroxylapatite (HAp). The P speciation shifted toward Mg orthophosphates and least soluble Ca orthophosphates following anaerobic digestion. Similarity between the aqueous orthophosphate (aq-PO4), newberyite (MgHPO4.3H2O), and struvite spectra can cause inaccurate P speciation determination when dairy manure is analyzed solely using P K-edge XANES spectroscopy; however, XANES can be used in conjunction with XRD to quantify the distribution of inorganic P species in animal manure. PMID:17965388

  6. XAF/XANES studies of plutonium-loaded sodalite/glass composite waste forms.

    SciTech Connect

    Aase, S. B.; Kropf, A. J.; Lewis, M. A.; Reed, D. T.; Richmann, M. K.

    1999-07-14

    A sodalite/glass ceramic waste form has been developed to immobilize highly radioactive nuclear wastes in chloride form, as part of an electrochemical cleanup process. Simulated waste forms have been fabricated which contain plutonium and are representative of the salt from the electrometallurgical process to recover uranium from spent nuclear fuel. X-ray absorption fine structure spectroscopy (XAFS) and x-ray absorption near-edge spectroscopy (XANES) studies were performed to determine the location, oxidation state and form of the plutonium within these waste forms. Plutonium, in the non-fission-element case, was found to segregate as plutonium(IV) oxide with a crystallite size of at least 20 nm. With fission elements present, the crystallite size was about 2 nm. No plutonium was observed within the sodalite or glass in the waste form.

  7. X-ray fluorescence mapping and micro-XANES spectroscopic characterization of exhaust particulates emitted from auto engines burning MMT-added gasoline.

    PubMed

    Mölders, N; Schilling, P J; Wong, J; Roos, J W; Smith, I L

    2001-08-01

    The elemental distribution and compositional homogeneity in auto exhaust particulates emitted from methylcyclopentadienyl manganese tricarbonyl-(MMT-)added gasoline engines have been investigated using a newly installed synchrotron X-ray microprobe. Two representative groups of exhaust particulate matter, as defined in a recent bulk X-ray absorption fine structure (XAFS) spectroscopic study at the Mn K-edge, were studied. The micro-X-ray absorption near-edge structure (XANES) spectra indicate a relatively homogeneous distribution of phases within a given particulate sample, down to a spatial extent of 40 microm (the resolution of microprobe). The micro-XANES also enabled analysis of several areas which displayed compositions different from the bulk sample, supporting the general theory describing manganese species formation in the exhaust. The ability to evaluate small regions also enabled direct verification of manganese sulfate from the S XANES despite the vast excess of sulfur present in other forms. The presence of a chloride compound, introduced through the sample dilution air and engine intake air, was also revealed. The study demonstrates the value of the combined X-ray microfluorescence with excitation by polychromatic radiation for elemental mapping and micro-XANES spectroscopy for chemical speciation in the study of dilute environmental materials containing low-Z constituents such as Cl, S, and P. PMID:11505987

  8. EXAFS and XANES analysis of oxides at the nanoscale

    PubMed Central

    Kuzmin, Alexei; Chaboy, Jesús

    2014-01-01

    Worldwide research activity at the nanoscale is triggering the appearance of new, and frequently surprising, materials properties in which the increasing importance of surface and interface effects plays a fundamental role. This opens further possibilities in the development of new multifunctional materials with tuned physical properties that do not arise together at the bulk scale. Unfortunately, the standard methods currently available for solving the atomic structure of bulk crystals fail for nanomaterials due to nanoscale effects (very small crystallite sizes, large surface-to-volume ratio, near-surface relaxation, local lattice distortions etc.). As a consequence, a critical reexamination of the available local-structure characterization methods is needed. This work discusses the real possibilities and limits of X-ray absorption spectroscopy (XAS) analysis at the nanoscale. To this end, the present state of the art for the interpretation of extended X-ray absorption fine structure (EXAFS) is described, including an advanced approach based on the use of classical molecular dynamics and its application to nickel oxide nanoparticles. The limits and possibilities of X-ray absorption near-edge spectroscopy (XANES) to determine several effects associated with the nanocrystalline nature of materials are discussed in connection with the development of ZnO-based dilute magnetic semiconductors (DMSs) and iron oxide nanoparticles. PMID:25485137

  9. Ca L2,3-edge XANES and Sr K-edge EXAFS study of hydroxyapatite and fossil bone apatite.

    PubMed

    Zougrou, I M; Katsikini, M; Brzhezinskaya, M; Pinakidou, F; Papadopoulou, L; Tsoukala, E; Paloura, E C

    2016-08-01

    Upon burial, the organic and inorganic components of hard tissues such as bone, teeth, and tusks are subjected to various alterations as a result of interactions with the chemical milieu of soil, groundwater, and presence of microorganisms. In this study, simulation of the Ca L 2,3-edge X-ray absorption near edge structure (XANES) spectrum of hydroxyapatite, using the CTM4XAS code, reveals that the different symmetry of the two nonequivalent Ca(1) and Ca(2) sites in the unit cell gives rise to specific spectral features. Moreover, Ca L 2,3-edge XANES spectroscopy is applied in order to assess variations in fossil bone apatite crystallinity due to heavy bacterial alteration and catastrophic mineral dissolution, compared to well-preserved fossil apatite, fresh bone, and geologic apatite reference samples. Fossilization-induced chemical alterations are investigated by means of Ca L 2,3-edge XANES and scanning electron microscopy (SEM) and are related to histological evaluation using optical microscopy images. Finally, the variations in the bonding environment of Sr and its preference for substitution in the Ca(1) or Ca(2) sites upon increasing the Sr/Ca ratio is assessed by Sr K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. PMID:27379398

  10. Ca L2,3-edge XANES and Sr K-edge EXAFS study of hydroxyapatite and fossil bone apatite

    NASA Astrophysics Data System (ADS)

    Zougrou, I. M.; Katsikini, M.; Brzhezinskaya, M.; Pinakidou, F.; Papadopoulou, L.; Tsoukala, E.; Paloura, E. C.

    2016-08-01

    Upon burial, the organic and inorganic components of hard tissues such as bone, teeth, and tusks are subjected to various alterations as a result of interactions with the chemical milieu of soil, groundwater, and presence of microorganisms. In this study, simulation of the Ca L 2,3-edge X-ray absorption near edge structure (XANES) spectrum of hydroxyapatite, using the CTM4XAS code, reveals that the different symmetry of the two nonequivalent Ca(1) and Ca(2) sites in the unit cell gives rise to specific spectral features. Moreover, Ca L 2,3-edge XANES spectroscopy is applied in order to assess variations in fossil bone apatite crystallinity due to heavy bacterial alteration and catastrophic mineral dissolution, compared to well-preserved fossil apatite, fresh bone, and geologic apatite reference samples. Fossilization-induced chemical alterations are investigated by means of Ca L 2,3-edge XANES and scanning electron microscopy (SEM) and are related to histological evaluation using optical microscopy images. Finally, the variations in the bonding environment of Sr and its preference for substitution in the Ca(1) or Ca(2) sites upon increasing the Sr/Ca ratio is assessed by Sr K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy.

  11. Diversity in C-Xanes Spectra Obtained from Carbonaceous Solid Inclusions from Monahans Halite

    NASA Technical Reports Server (NTRS)

    Kebukawa, Y.; Zolensky, M. E.; Fries, M.; Kilcoyne, A. L. D.; Rahman, Z.; Cody, G. D.

    2014-01-01

    Monahans meteorite (H5) contains fluid inclusion- bearing halite (NaCl) crystals [1]. Microthermometry and Raman spectroscopy showed that the fluid in the inclusions is an aqueous brine and they were trapped near 25degC [1]. Their continued presence in the halite grains requires that their incorporation into the H chondrite asteroid was post metamorphism [2]. Abundant solid inclusions are also present in the halites. The solid inclusions include abundant and widely variable organics [2]. Analyses by Raman microprobe, SEM/EDX, synchrotron X-ray diffraction and TEM reveal that these grains include macromolecular carbon similar in structure to CV3 chondrite matrix carbon, aliphatic carbon compounds, olivine (Fo99-59), high- and low-Ca pyroxene, feldspars, magnetite, sulfides, lepidocrocite, carbonates, diamond, apatite and possibly the zeolite phillipsite [3]. Here we report organic analyses of these carbonaceous residues in Monahans halite using C-, N-, and O- X-ray absorption near edge structure (XANES). Samples and Methods: Approximately 100 nm-thick sections were extracted with a focused ion beam (FIB) at JSC from solid inclusions from Monahans halite. The sections were analyzed using the scanning transmission X-ray microscope (STXM) on beamline 5.3.2.2 at the Advanced Light Source, Lawrence Berkeley National Laboratory for XANES spectroscopy. Results and Discussion: C-XANES spectra of the solid inclusions show micrometer-scale heterogeneity, indicating that the macromolecular carbon in the inclusions have complex chemical variations. C-XANES features include 284.7 eV assigned to aromatic C=C, 288.4-288.8 eV assigned to carboxyl, and 290.6 eV assigned to carbonate. The carbonyl features obtained by CXANES might have been caused by the FIB used in sample preparation. No specific N-XANES features are observed. The CXANES spectra obtained from several areas in the FIB sections include type 1&2 chondritic IOM like, type 3 chondritic IOM like, and none of the above

  12. 279 - Xanes Studies on UV-Irradiated Interstellar Ice Analogs: A Comparison to STARDUST Samples

    NASA Technical Reports Server (NTRS)

    Milam, Stefanie N.; Cody, George D.; Kilcoyne, A. L. David; Nuevo, Michel; Sandford, Scott A.; Stroud, Rhonda M.; DeGregorio, Bradley T.

    2010-01-01

    We present C-, N-, and O-XANES (X-ray Absorption Near-Edge Spectroscopy) results of organic residues produced in the laboratory from the UV irradiation of astrophysical ice analogs containing H20, CO, CH30H, NH31 in order to mimic processes that may occur in cold icy bodies of the outer Solar System, particularly in comets, Such analyses showed that laboratory-formed organic residues mainly consist of a solid phase and an oily phase. C-XANES analysis of the solid phase suggests a rich distribution of organic functionalities, among which carbonyl groups, C=C bonds, and alcohols are present. Results from N-XANES indicate the possible presence of amide, amine, and nitrile groups, The O-XANES spectra confirmed the a-bearing groups, These results are compared with the XANES spectra obtained from STARDUST cometary samples,

  13. Investigation of soil legacy phosphorus transformation in long-term agricultural fields using sequential fractionation, P K-edge XANES and solution P NMR spectroscopy.

    PubMed

    Liu, Jin; Hu, Yongfeng; Yang, Jianjun; Abdi, Dalel; Cade-Menun, Barbara J

    2015-01-01

    Understanding legacy phosphorus (P) build-up and draw-down from long-term fertilization is essential for effective P management. Using replicated plots from Saskatchewan, Canada, with P fertilization from 1967 to 1995 followed by either P fertilization or P cessation (1995-2010), soil P was characterized in surface and subsurface layers using sequential fractionation, P K-edge X-ray absorption near-edge structure (XANES) and solution (31)P nuclear magnetic resonance (P NMR) spectroscopy. Legacy P from a 28-year build-up was sufficient for 15 years of wheat cultivation, resulting in no significant differences in crop yield in 2010. In surface soils, soil test (Olsen) P decreased significantly in unfertilized plots compared with 1995, which was reflected in declining aluminum (hydr)oxide-associated inorganic P by fractionation and XANES. Furthermore, XANES analysis revealed a decrease of calcium-associated P in 2010-unfertilized soils at both depths and an increase of Fe (hydr)oxides-associated P in the 2010-fertilized and -unfertilized surface soils relative to the 1995 soils. Increased total organic P and orthophosphate diesters by P NMR and accumulated inositol hexaphosphate by XANES were observed in surface soils with P fertilization cessation. In subsurface soils, few legacy P transformations were detected. These results provide important information about legacy P to improve agricultural sustainability while mitigating water quality deterioration. PMID:25426546

  14. The electronic structure of homogeneous ferromagnetic (Ga, Mn)N epitaxial films

    SciTech Connect

    Piskorska-Hommel, E.; Winiarski, M. J.; Kunert, G.; Falta, J.; Demchenko, I. N.; Roshchupkina, O. D.; Grenzer, J.; Hommel, D.; Holý, V.

    2015-02-14

    X-ray Absorption Fine Structure (XAFS) techniques, namely, X-ray Near Edge Structure (XANES), Extended XAFS (EXAFS), and Anomalous X-ray Diffraction (AXRD) were used to investigate the local atomic and electronic structure of (Ga, Mn)N magnetic layers with Mn concentrations of up to 10% grown by Molecular Beam Epitaxy. The XANES and AXRD analysis prove the Mn incorporation on substitutional GaN lattice sites. EXAFS results indicate the good quality of the structure under examination, although 0.5 nitride atom vacancies were found. The Wien2k code was applied to interpret the XANES spectra quantitatively, i.e., to determine the electronic structure of the Mn atoms. It was shown that accounting for the core-hole effect is necessary to reconstruct effectively the XANES spectra. Conducted charge density analysis based on DFT calculations identified the valency of Mn atom to be of 2.4+.

  15. Structure of assemblies of metal nanowires in mesoporous alumina membranes studied by EXAFS, XANES, X-ray diffraction and SAXS.

    PubMed

    Benfield, Robert E; Grandjean, Didier; Dore, John C; Esfahanian, Hamid; Wu, Zhonghua; Kröll, Michael; Geerkens, Marcus; Schmid, Günter

    2004-01-01

    Mesoporous alumina membranes ("anodic aluminium oxide", or "AAO") are made by anodic oxidation of aluminium metal. These membranes contain hexagonal arrays of parallel non-intersecting cylindrical pores perpendicular to the membrane surface. By varying the anodisation voltage, the pore diameters are controllable within the range 5-250 nm. We have used AAO membranes as templates for the electrochemical deposition of metals within the pores to produce nanowires. These represent assemblies of one-dimensional quantum wires with prospective applications in electronic, optoelectronic and magnetic devices. Detailed characterisation of the structures of these nanowire assemblies on a variety of length scales is essential to understand their physical properties and evaluate their possible applications. We have used EXAFS, XANES, WAXS, high energy X-ray diffraction and SAXS to study their structure and bonding. In this paper we report the results of our studies of four different nanowire systems supported in AAO membranes. These are the ferromagnetic metals iron and cobalt, the superconducting metal tin, and the semiconductor gallium nitride. Iron nanowires in pores of diameter over the range 12 nm-72 nm are structurally very similar to bcc bulk iron. They have a strong preferred orientation within the alumina pores. Their XANES shows significant differences from that of bulk iron, showing that the electronic structure of the iron nanowires depends systematically on their diameter. Cobalt nanowires are composed of a mixture of hcp and fcc phases, but the ratio of the two phases does not depend in a simple way on the pore diameter or preparation conditions. In bulk cobalt, the fcc beta-phase is normally stable only at high temperatures. Strong preferred orientation of the c-axis in the pores was found. Tin nanowires in alumina membranes with pores diameters between 12 nm and 72 nm have a tetragonal beta-structure at ambient temperature and also at 80 K. Magnetic

  16. XANES Speciation of P in Environmental Samples: An Assessment of Filter Media for on-Site Wastewater Treatment

    SciTech Connect

    Eveborn, D.; Gustafsson, J; Hesterberg, D; Hillier, S

    2009-01-01

    X-ray absorption near edge structure (XANES) spectroscopy is a useful technique for characterization of chemical species of phosphorus in complex environmental samples. To develop and evaluate bed filters as sustainable on-site wastewater treatment solutions, our objective in this study was to determine the chemical forms of accumulated phosphorus in a selection of promising filter materials: Filtralite P, Filtra P, Polonite, Absol, blast furnace slag, and wollastonite. Full-scale operational wastewater-treatment systems were sampled and in addition, filter samples collected from laboratory studies provided access to additional media and complementary samples. Phosphorus species were characterized using phosphorus K-edge XANES spectroscopy, complemented by X-ray powder diffraction (XRPD) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). No systematic differences could be seen in the results between laboratory- and full-scale samples. All six filter media contained significant amounts of crystalline calcium phosphates. Some samples also contained amorphous calcium phosphate (>60% of total P in Absol). In Filtralite P and blast furnace slag, more than 35% of the accumulated phosphorus was associated with Fe or Al. Both the power and shortcomings of XANES analysis for characterizing P species in these filter media are discussed.

  17. Aqueous U(VI) interaction with magnetite nanoparticles in a mixed flow reactor system: HR-XANES study

    NASA Astrophysics Data System (ADS)

    Pidchenko, I.; Heberling, F.; Kvashnina, KO; Finck, N.; Schild, D.; Bohnert, E.; Schäfer, T.; Rothe, J.; Geckeis, H.; Vitova, T.

    2016-05-01

    The redox variations and changes in local atomic environment of uranium (U) interacted with the magnetite nanoparticles were studied in a proof of principle experiment by the U L3 and M4 edges high energy resolution X-ray absorption near edge structure (HR-XANES) technique. We designed and applied a mixed flow reactor (MFR) set-up to maintain dynamic flow conditions during U-magnetite interactions. Formation of hydrolyzed, bi- and poly-nuclear U species were excluded by slow continuous injection of U(VI) (10-6 M) and pH control integrated in the MFR set-up. The applied U HR-XANES technique is more sensitive to minor changes in the U redox states and bonding compared to the conventional XANES method. Major U(VI) contribution in uranyl type of bonding is found in the magnetite nanoparticles after three days operation time of the MFR. Indications for shortening of the U-Oaxial bond length for the magnetite compared to the maghemite system are present too.

  18. Optimizing experimental design, overcoming challenges, and gaining valuable information from the Sb K-edge XANES region

    SciTech Connect

    Fawcett, Skya E.; Gordon, Robert A.; Jamieson, Heather E.

    2009-10-05

    There are many challenges associated with collecting, processing, and interpreting high-energy XAS data. The most significant of these are broad spectra, minimal separation of edge positions, and high background owing to the Compton tail. Studies of the Sb system are a particular challenge owing to its complex bonding character and formation of mixed oxidation-state minerals. Furthermore, in environmental samples such as stream sediment containing mine waste, different Sb phases may coexist. Ways to overcome these challenges and achieve accurate and useful information are presented. Our investigations used Sb K-edge X-ray absorption near-edge spectroscopy (XANES) to elucidate Sb geochemical behavior. Several Sb mineral spectra are presented, including Sb sulfosalts, and contrasted based on the different hosting and coordination environments around the Sb atom in the crystal structure. These comparisons lead to the recognition of how the different hosting and coordination environments are manifested in the shape of the Sb mineral spectra. In fact from the shape of the spectra, the occupation of the Sb atom in a single or in multiple crystallographic sites, regardless of whether multiple phases are present in the sample, is discernible. Furthermore, we demonstrate that quantitative information can be derived from the XANES region using linear combination fitting of the derivative spectra, rather than the energy spectra. Particularly useful to the advancement of Sb research is the demonstration that a significant amount of information can be gained from the Sb K-edge XANES region.

  19. Ru L[subscript 2,3] XANES theoretical simulation with DFT: A test of the core-hole treatment

    SciTech Connect

    Alperovich, Igor; Moonshiram, Dooshaye; Soldatov, Alexander; Pushkar, Yulia

    2012-10-09

    Density functional theory (DFT)-based relativistic calculations were performed to model the Ru L-edge X-ray absorption near edge structure (XANES) spectra of the hexaammineruthenium complex [Ru(NH{sub 3}){sub 6}]{sup 3+} and 'blue dimer' water oxidation catalyst, cis,cis- [(bpy){sub 2}(H{sub 2}O)Ru{sup III}ORu{sup III}(OH{sub 2})(bpy){sub 2}]{sup 4+} (bpy is 2,2-bipyridine). Two computational approaches were compared: simulations without the core-hole and by modeling of the core-hole within the Z+1 approximation. Good agreement between calculated and experimental XANES spectra is achieved without including the core-hole. Simulations with algorithms beyond the Z+1 approximation were only possible in a framework of the scalar relativistic treatment. Time-dependent DFT (TD-DFT) was used to compute the Ru L-edge spectrum for [Ru(NH{sub 3}){sub 6}]{sup 3+} model compound. Three different core-hole treatments were compared in a real-space full multiple scattering XANES modeling within the Green function formalism (implemented in the FEFF9.5 package) for the [Ru(Mebimpy)(bpm)(H{sub 2}O)]{sup 2+} complex. The latter approaches worked well in cases where spin-orbit treatment of relativistic effects is not required.

  20. C-C bond unsaturation degree in monosubstituted ferrocenes for molecular electronics investigated by a combined near-edge x-ray absorption fine structure, x-ray photoemission spectroscopy, and density functional theory approach

    NASA Astrophysics Data System (ADS)

    Boccia, A.; Lanzilotto, V.; Marrani, A. G.; Stranges, S.; Zanoni, R.; Alagia, M.; Fronzoni, G.; Decleva, P.

    2012-04-01

    We present the results of an experimental and theoretical investigation of monosubstituted ethyl-, vinyl-, and ethynyl-ferrocene (EtFC, VFC, and EFC) free molecules, obtained by means of synchrotron-radiation based C 1s photoabsorption (NEXAFS) and photoemission (C 1s XPS) spectroscopies, and density functional theory (DFT) calculations. Such a combined study is aimed at elucidating the role played by the C-C bond unsaturation degree of the substituent on the electronic structure of the ferrocene derivatives. Such substituents are required for molecular chemical anchoring onto relevant surfaces when ferrocenes are used for molecular electronics hybrid devices. The high resolution C 1s NEXAFS spectra exhibit distinctive features that depend on the degree of unsaturation of the hydrocarbon substituent. The theoretical approach to consider the NEXAFS spectrum made of three parts allowed to disentangle the specific contribution of the substituent group to the experimental spectrum as a function of its unsaturation degree. C 1s IEs were derived from the experimental data analysis based on the DFT calculated IE values for the different carbon atoms of the substituent and cyclopentadienyl (Cp) rings. Distinctive trends of chemical shifts were observed for the substituent carbon atoms and the substituted atom of the Cp ring along the series of ferrocenes. The calculated IE pattern was rationalized in terms of initial and final state effects influencing the IE value, with special regard to the different mechanism of electron conjugation between the Cp ring and the substituent, namely the σ/π hyperconjugation in EtFC and the π-conjugation in VFC and EFC.

  1. C-C bond unsaturation degree in monosubstituted ferrocenes for molecular electronics investigated by a combined near-edge x-ray absorption fine structure, x-ray photoemission spectroscopy, and density functional theory approach

    SciTech Connect

    Boccia, A.; Lanzilotto, V.; Marrani, A. G.; Zanoni, R.; Stranges, S.; Alagia, M.; Fronzoni, G.; Decleva, P.

    2012-04-07

    We present the results of an experimental and theoretical investigation of monosubstituted ethyl-, vinyl-, and ethynyl-ferrocene (EtFC, VFC, and EFC) free molecules, obtained by means of synchrotron-radiation based C 1s photoabsorption (NEXAFS) and photoemission (C 1s XPS) spectroscopies, and density functional theory (DFT) calculations. Such a combined study is aimed at elucidating the role played by the C-C bond unsaturation degree of the substituent on the electronic structure of the ferrocene derivatives. Such substituents are required for molecular chemical anchoring onto relevant surfaces when ferrocenes are used for molecular electronics hybrid devices. The high resolution C 1s NEXAFS spectra exhibit distinctive features that depend on the degree of unsaturation of the hydrocarbon substituent. The theoretical approach to consider the NEXAFS spectrum made of three parts allowed to disentangle the specific contribution of the substituent group to the experimental spectrum as a function of its unsaturation degree. C 1s IEs were derived from the experimental data analysis based on the DFT calculated IE values for the different carbon atoms of the substituent and cyclopentadienyl (Cp) rings. Distinctive trends of chemical shifts were observed for the substituent carbon atoms and the substituted atom of the Cp ring along the series of ferrocenes. The calculated IE pattern was rationalized in terms of initial and final state effects influencing the IE value, with special regard to the different mechanism of electron conjugation between the Cp ring and the substituent, namely the {sigma}/{pi} hyperconjugation in EtFC and the {pi}-conjugation in VFC and EFC.

  2. Surface complexation and precipitate geometry for aqueous Zn(II) sorption on ferrihydrite: II. XANES analysis and simulation

    USGS Publications Warehouse

    Waychunas, G.A.; Fuller, C.C.; Davis, J.A.; Rehr, J.J.

    2003-01-01

    X-ray absorption near-edge spectroscopy (XANES) analysis of sorption complexes has the advantages of high sensitivity (10- to 20-fold greater than extended X-ray absorption fine structure [EXAFS] analysis) and relative ease and speed of data collection (because of the short k-space range). It is thus a potentially powerful tool for characterization of environmentally significant surface complexes and precipitates at very low surface coverages. However, quantitative analysis has been limited largely to "fingerprint" comparison with model spectra because of the difficulty of obtaining accurate multiple-scattering amplitudes for small clusters with high confidence. In the present work, calculations of the XANES for 50- to 200-atom clusters of structure from Zn model compounds using the full multiple-scattering code Feff 8.0 accurately replicate experimental spectra and display features characteristic of specific first-neighbor anion coordination geometry and second-neighbor cation geometry and number. Analogous calculations of the XANES for small molecular clusters indicative of precipitation and sorption geometries for aqueous Zn on ferrihydrite, and suggested by EXAFS analysis, are in good agreement with observed spectral trends with sample composition, with Zn-oxygen coordination and with changes in second-neighbor cation coordination as a function of sorption coverage. Empirical analysis of experimental XANES features further verifies the validity of the calculations. The findings agree well with a complete EXAFS analysis previously reported for the same sample set, namely, that octahedrally coordinated aqueous Zn2+ species sorb as a tetrahedral complex on ferrihydrite with varying local geometry depending on sorption density. At significantly higher densities but below those at which Zn hydroxide is expected to precipitate, a mainly octahedral coordinated Zn2+ precipitate is observed. An analysis of the multiple scattering paths contributing to the XANES

  3. Intracellular nanoparticles mass quantification by near-edge absorption soft X-ray nanotomography

    NASA Astrophysics Data System (ADS)

    Conesa, Jose Javier; Otón, Joaquín; Chiappi, Michele; Carazo, Jose María; Pereiro, Eva; Chichón, Francisco Javier; Carrascosa, José L.

    2016-03-01

    We used soft X-ray three-dimensional imaging to quantify the mass of superparamagnetic iron oxide nanoparticles (SPION) within whole cells, by exploiting the iron oxide differential absorption contrast. Near-edge absorption soft X-ray nanotomography (NEASXT) combines whole-cell 3D structure determination at 50 nm resolution, with 3D elemental mapping and high throughput. We detected three-dimensional distribution of SPIONs within cells with 0.3 g/cm3 sensitivity, sufficient for detecting the density corresponding to a single nanoparticle.

  4. Intracellular nanoparticles mass quantification by near-edge absorption soft X-ray nanotomography

    PubMed Central

    Conesa, Jose Javier; Otón, Joaquín; Chiappi, Michele; Carazo, Jose María; Pereiro, Eva; Chichón, Francisco Javier; Carrascosa, José L.

    2016-01-01

    We used soft X-ray three-dimensional imaging to quantify the mass of superparamagnetic iron oxide nanoparticles (SPION) within whole cells, by exploiting the iron oxide differential absorption contrast. Near-edge absorption soft X-ray nanotomography (NEASXT) combines whole-cell 3D structure determination at 50 nm resolution, with 3D elemental mapping and high throughput. We detected three-dimensional distribution of SPIONs within cells with 0.3 g/cm3 sensitivity, sufficient for detecting the density corresponding to a single nanoparticle. PMID:26960695

  5. Intracellular nanoparticles mass quantification by near-edge absorption soft X-ray nanotomography.

    PubMed

    Conesa, Jose Javier; Otón, Joaquín; Chiappi, Michele; Carazo, Jose María; Pereiro, Eva; Chichón, Francisco Javier; Carrascosa, José L

    2016-01-01

    We used soft X-ray three-dimensional imaging to quantify the mass of superparamagnetic iron oxide nanoparticles (SPION) within whole cells, by exploiting the iron oxide differential absorption contrast. Near-edge absorption soft X-ray nanotomography (NEASXT) combines whole-cell 3D structure determination at 50 nm resolution, with 3D elemental mapping and high throughput. We detected three-dimensional distribution of SPIONs within cells with 0.3 g/cm(3) sensitivity, sufficient for detecting the density corresponding to a single nanoparticle. PMID:26960695

  6. High Pressure XANES studies on Mn dopeHigh Pressure XANES studies on Mn doped Bi2 Te3

    NASA Astrophysics Data System (ADS)

    Light, Brian; Kumar, Ravhi; Baker, Jason; Dharmalingam, Prabhakaran; Park, Changyong; Unlv Team; Hpcat; Carnegie Institute Of Washington Collaboration

    Bi2Te3, Bi2Se3, and Sb2Te3 are narrow band-gap semiconductors have been extensively studied along with their alloys due to their promising technological applications as thermoelectric materials. More recently pressure induced superconductivity and structural transition have been observed in these materials around 7 GPa [1, 2]. Here we have performed high pressure x-ray near edge spectroscopy (XANES) measurements at Bi L-III edge on Mn (0.1) doped Bi2Te3 samples to understand the variation of the Bi valence across the pressure induced superconductivity regime. We have inferred notable changes in the Bi valence at high pressure conditions. The results will be discussed in detail. Work at the University of Nevada Las Vegas (ALC) is funded by U.S. Department of Energy Award DE-SC0001928. Portions of this work were performed at HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory. HPCAT is supported by DOE-BES, DOE-NNSA, NSF, and the W.M. Keck Foundation. APS is supported by DOE-BES, under Contract No. DE-AC02-06CH1135.

  7. XANES study of hydrogen incorporation in a Pd-capped Nb thin film

    SciTech Connect

    Ruckman, M.W.; Reisfeld, G.; Jisrawi, N.M.; Weinert, M.; Strongin, M.; Wiesmann, H.; Croft, M.; Sahiner, A.; Sills, D.; Ansari, P.

    1998-02-01

    X-ray absorption near-edge structure (XANES) measurements were used to probe the H-charging-induced electronic structure changes of a 2400 {Angstrom} Nb film capped with Pd. These results are discussed in terms of {ital ab initio} linear augmented plane-wave (LAPW) band-structure calculations for this material. The Pd-L{sub 3}-edge XANES clearly manifested the spectral (Pd-d state related) changes expected for Pd-hydride formation, a white line feature degradation, and the appearance of a Pd-H antibonding feature at 6 eV above the threshold. The Nb-L{sub 2,3} edge changes with H charging show a distinct enhancement of the white line strength; a feature 6 eV above the edges, associated with Nb-H antibonding states in analogy with the Pd results; the suppression of a threshold-onset feature of Nb metal; and a shift of the centrum of the white line feature towards the threshold. Comparison of the Nb sphere projection of the d{sub 3/2} component of the LAPW density of states (DOS) to the Nb-L{sub 2}-edge spectra yields good basic agreement with the observed spectral changes. In particular, the substantial theoretical reduction in the DOS at, and just above, the Fermi energy (E{sub f}) is directly related to the near threshold Nb-L{sub 2,3} spectral changes. The more modest white line enhancement in the theoretical DOS is noted and discussed. Nb-K-edge XANES are also discussed in terms of the Nb-site p-state projected LAPW DOS. This last comparison indicates a p-state reduction near E{sub f} upon H charging of the Nb. {copyright} {ital 1998} {ital The American Physical Society}

  8. A XANES study of Cu speciation in high-temperature brines using synthetic fluid inclusions

    SciTech Connect

    Berry, Andrew J.; Hack, Alistair C.; Mavrogenes, John A.; Newville, Matthew; Sutton, Stephen R.

    2010-12-03

    Cu K-edge X-ray absorption near edge structure (XANES) spectra were recorded from individual synthetic brine fluid inclusions as a function of temperature up to 500 C. The inclusions serve as sample cells for high-temperature spectroscopic studies of aqueous Cu-Cl speciation. Cu{sup +} and Cu{sup 2+} can both be identified from characteristic pre-edge features. Mixed oxidation states can be deconvoluted using linear combinations of Cu{sup +} and Cu{sup 2+} spectra. This work illustrates how complex Cu XANES spectra can be interpreted successfully. Cu{sup 2+} is the stable oxidation state in solution at room temperature and Cu{sup +} at high temperatures. The change in oxidation state with temperature was completely reversible. Cu{sup +} was found to occur exclusively as the linear species [CuCl{sub 2}]{sup -} in solutions containing KCl with Cu:Cl ratios up to 1:6. In the absence of K{sup +}, there is evidence for higher order coordination of Cu{sup +}, in particular the tetrahedral complex [CuCl{sub 4}]{sup 3-}. The importance of such complexes in natural ore-forming fluids is yet to be determined, but may explain the vapor-phase partitioning of Cu as a Cl complex from a Cl-rich brine.

  9. The blue of iron in mineral pigments: a Fe K-edge XANES study of vivianite

    NASA Astrophysics Data System (ADS)

    Figueiredo, M. O.; Silva, T. P.; Veiga, J. P.

    2010-05-01

    Iron is a powerful chromophore element whose pigmenting properties were the first to be recognized among transition metals. The interest in blue iron minerals as pigments for painting was enhanced with the use of vivianite—a natural hydrated ferrous phosphate, Fe3(PO4)2ṡ8H2O—which in medieval Europe became an alternative to the expensive lapis lazuli, (Na, Ca)4(AlSiO4)3(SO4, Cl, S), a member of the ultramarines whose appreciated blue tone is due to the presence of sulfur polyanions. Conversely, vivianite coloring is attributed to the intervalence charge transfer (IVCT) Fe2+-Fe3+ that in later decades was studied by optical techniques and Mössbauer spectroscopy. However, the aging of blue vivianite pigments in old paintings has become a serious concern for conservators, but the aging process still awaits a satisfactory explanation. As an input to this problem, an X-ray absorption near-edge structure (XANES) study at the Fe K-edge of vivianite with different colors and origins was undertaken at the European Synchrotron Radiation Facility using the instrumental facilities of beamline ID-21. The analysis of pre-edge features corroborates previous data on the origin of vivianite color and emphasizes the need for a precautious assessment of iron speciation on the exclusive basis of XANES data. Actual results are discussed and further work is outlined.

  10. XANES studies of photocatalytic active species in nano TiO 2-SiO 2

    NASA Astrophysics Data System (ADS)

    Li Hsiung, Tung; Paul Wang, H.; Wang, H. C.

    2006-11-01

    Combined post-edge XANES (X-ray absorption near-edge structural) and 29Si magic angle spinning solid-state nuclear magnetic resonance (MAS SSNMR) observations show that Ti was dispersed in the frameworks of nano SiO 2 (synthesized with the sol-gel method). In addition, the nano TiO 2-SiO 2 photocatalyst have features such as A1 (4969 eV), A2 (4970.5 eV) and A3 (4972 eV) that can be attributed to 1s-to-3d transitions for four- (TiO 4), five- ((Ti=O)O 4), and six- (TiO 6) coordinated Ti species, respectively. The A2 ((Ti=O)O 4) in TiO 2-SiO 2 may be the main active species, for instance, in the photocatalytic decomposition of trace 2-chlorophenol in H 2O. This work exemplifies the utilization of XANES to reveal the active species in nano photocatalysts in detail.

  11. Spectral analysis by XANES reveals that GPNMB influences the chemical composition of intact melanosomes

    PubMed Central

    Haraszti, Tamas; Trantow, Colleen M.; Hedberg-Buenz, Adam; Grunze, Michael; Anderson, Michael G.

    2010-01-01

    Summary GPNMB is a unique melanosomal protein. Unlike many melanosomal proteins, GPNMB has not been associated with any forms of albinism and it is unclear whether GPNMB has any direct influence on melanosomes. Here, melanosomes from congenic strains of C57BL/6J mice mutant for Gpnmb are compared to strain-matched controls using standard transmission electron microscopy and synchrotron-based X-ray absorption near-edge structure analysis (XANES). Whereas electron microscopy did not detect any ultrastructural changes to melanosomes lacking functional GPNMB, XANES uncovered multiple spectral phenotypes. These results directly demonstrate that GPNMB influences the chemical composition of melanosomes, and more broadly illustrate the potential for using genetic approaches in combination with nano-imaging technologies to study organelle biology. Significance Of the large number of proteins known to be present in melanosomes, the majority are not known to visibly influence melanosome appearance. It remains largely unknown what role, if any, most of these proteins may have in pigment cell biology. This work demonstrates an approach for discovering previously undetectable melanosomal phenotypes through a combined use of synchrotron-based spectromicroscopy and genetics. Specifically, we demonstrate that GPNMB influences the carbon absorption spectra of melanosomes. A similar strategy might also be applied to discover new features of a wide range of additional organelles important to human health and disease. PMID:21029394

  12. Trichroism in energy-loss near-edge structure spectroscopy: Polarization dependence of near-edge fine structures

    SciTech Connect

    Le Bosse, Jean-Claude; Epicier, Thierry; Chermette, Henry

    2007-08-15

    The goal of this paper is to relate the current of inelastically scattered electrons collected in a transmission electron microscope (TEM) to the double differential electron energy-loss cross section. Up to now, this relationship, which depends on the point symmetry around the probed atom site, has been essentially studied in a situation called dichroism. This situation can be encountered when a principal threefold, fourfold, or sixfold rotation axis through the probed atom site exists. The electron energy-loss cross section is then a linear combination of longitudinal and transversal cross sections, and the weights of these components are cos{sup 2} {theta}{sub q} and sin{sup 2} {theta}{sub q}, where {theta}{sub q} is the angle between the scattering wave vector q and the principal rotation axis. The first aim of this paper is to find the dependence on q of the cross section in all other cases, that is to say, when the symmetry around the probed atom site is described with one of the eight low symmetry point groups C{sub 1}, S{sub 2}, C{sub 1h}, C{sub 2}, C{sub 2h}, C{sub 2v}, D{sub 2}, and D{sub 2h}. In these eight cases of low symmetry, three distinct situations called trichroism can be distinguished. In these situations, the cross section is expressed in terms of the cross sections obtained for six, four, or three particular orientations of the scattering wave vector. The second aim of this paper is to provide an expression of the inelastically scattered electron current collected in a TEM for these three situations of trichroism. This current is expressed in terms of experimental parameters, such as the incident beam convergence, the collector acceptance, the electron beam kinetic energy, and the sample orientation. As in the case of dichroism, magic conditions can be found, for which the collected current becomes independent of the single-crystal sample orientation. The case of the C K edge in the nonstoichiometric V{sub 6}C{sub 5} metallic carbide with a trigonal symmetry is given as an illustration.

  13. Local structure of indium oxynitride from x-ray absorption spectroscopy

    SciTech Connect

    T-Thienprasert, J.; Onkaw, D.; Rujirawat, S.; Limpijumnong, S.; Nukeaw, J.; Sungthong, A.; Porntheeraphat, S.; Singkarat, S.

    2008-08-04

    Synchrotron x-ray absorption near edge structures (XANES) measurements of In L{sub 3} edge is used in conjunction with first principles calculations to characterize rf magnetron sputtered indium oxynitride at different O contents. Good agreement between the measured and the independently calculated spectra are obtained. Calculations show that the XANES spectra of this alloy are sensitive to the coordination numbers of the In atoms, i.e., fourfold for indium nitride-like structures and sixfold for indium oxide-like structures, but not to the substitution of nearest neighbor N by O or vice versa.

  14. Substitution behavior of x(Na0.5K0.5)NbO3-(1 - x)BaTiO3 ceramics for multilayer ceramic capacitors by a near edge x-ray absorption fine structure analysis

    NASA Astrophysics Data System (ADS)

    Ha, Jooyeon; Ryu, Jiseung; Lee, Heesoo

    2014-06-01

    The doping effect of (Na0.5K0.5)NbO3 (NKN) as alternatives for rare-earth elements on the electrical properties of BaTiO3 has been investigated, in terms of their substitution behavior. The dielectric constant of a specimen with x = 0.05 was about 79% higher than that of pure BaTiO3, and the temperature coefficient of capacitance was satisfied by the X7R specification. The specimen with x = 0.05 showed the lowest tetragonality among the four compositions and had a fine grain size of <2 μm. Although the addition of NKN decreased the specimen's tetragonality, the electrical properties were enhanced by the formation of defect dipoles and conduction electrons, which resulted from an acceptor and donor substitution behavior. Through O K-edge near edge x-ray absorption fine structure spectroscopy, the practical substitution behavior was defined by the change in Ti 3d orbital states. The energy separation of the Ti 3d orbitals was more apparent with the specimen of x = 0.05, which is related to the donor level from the donor substitution of Nb5+ ion for Ti-sites. Therefore, the simultaneous substitution of Na+/K+ and Nb5+ ions into BaTiO3 can improve dielectric properties, based on the charge-transfer process.

  15. The status of strontium in biological apatites: an XANES investigation.

    PubMed

    Bazin, D; Daudon, M; Chappard, Ch; Rehr, J J; Thiaudière, D; Reguer, S

    2011-11-01

    Osteoporosis represents a major public health problem and increases patient morbidity through its association with fragility fractures. Among the different treatments proposed, strontium-based drugs have been shown to increase bone mass in postmenopausal osteoporosis patients and to reduce fracture risk. While the localization of Sr(2+) cations in the bone matrix has been extensively studied, little is known regarding the status of Sr(2+) cations in natural biological apatite. In this investigation the local environment of Sr(2+) cations has been investigated through XANES (X-ray absorption near-edge structure) spectroscopy in a set of pathological and physiological apatites. To assess the localization of Sr(2+) cations in these biological apatites, numerical simulations using the ab initio FEFF9 X-ray spectroscopy program have been performed. The complete set of data show that the XANES part of the absorption spectra may be used as a fingerprint to determine the localization of Sr(2+) cations versus the mineral part of calcifications. More precisely, it appears that a relationship exists between some features present in the XANES part and a Sr(2+)/Ca(2+) substitution process in site (I) of crystal apatite. Regarding the data, further experiments are needed to confirm a possible link between the relationship between the preparation mode of the calcification (cellular activity for physiological calcification and precipitation for the pathological one) and the adsorption mode of Sr(2+) cations (simple adsorption or insertion). Is it possible to draw a line between life and chemistry through the localization of Sr in apatite? The question is open for discussion. A better structural description of these physiological and pathological calcifications will help to develop specific therapies targeting the demineralization process in the case of osteoporosis. PMID:21997917

  16. Use of micro-XANES to speciate chromium in airborne fine particles in the Sacramento Valley

    SciTech Connect

    Michelle L. Werner; Peter S. Nico; Matthew A. Marcus; Cort Anastasio

    2007-07-15

    While particulate matter (PM) in the atmosphere can lead to a wide array of negative health effects, the cause of toxicity is largely unknown. One aspect of PM that likely affects health is the chemical composition, in particular the transition metals within the particles. Chromium is one transition metal of interest due to its two major oxidation states, with Cr(III) being much less toxic compared to Cr(VI). Using microfocused X-ray absorption near edge structure (micro-XANES), we analyzed the Cr speciation in fine particles (diameters {le} 2.5 {mu}m) collected at three sites in the Sacramento Valley of northern California: Sacramento, a large urban area, Davis, a small city, and Placerville, a rural area. These are several major stationary sources of Cr within 24 km of the site including chrome-plating plants, power plants and incinerators. The microfocused X-ray beam enables us to look at very small areas on the filter with a resolution of typically 5-7 micrometers. With XANES we are able to not only distinguish between Cr(VI) and Cr(III), but also to identify different types of Cr(III) and more reduced Cr species. At all of our sampling sites the main Cr species were Cr(III), with Cr(OH){sub 3} or a Cr-Fe, chromite-like, phase being the dominant species. Cr(VI)-containing particles were found only in the most urban site. All three sites contained some reduced Cr species, either Cr(0) or Cr{sub 3}C{sub 2}, although these were minor components. This work demonstrates that micro-XANES can be used as a minimally invasive analytical tool to investigate the composition of ambient PM. 32 refs., 6 figs.

  17. Analyzing organic sulfur in coal/char: Integrated mild degradation/XANES methods. [Quarterly] technical report, December 1, 1993--February 28, 1994

    SciTech Connect

    Palmer, S.R.; Huffman, G.P.

    1994-06-01

    The cost effective removal of sulfur from coal has been very difficult to accomplish. Perhaps the single most important reason for this is the fact that the organic sulfur in coal remains very poorly characterized. The overall goal of this study is to improve our understanding of sulfur in coals/chars via the use of combined advanced non-destructive and advanced destructive methods of sulfur analysis. This study combines selective oxidation, analytical pyrolysis, and sulfur X-ray Absorption Near Edge Structure Spectroscopy (XANES) analysis. Examination of samples that were oxidized with peroxyacetic acid using the analytical pyrolysis technique showed that the level of simple thiophene structures observed in the pyrolysis products declines with increasing levels of oxidation. Sulfur XANES spectra of treated samples showed various effects depending on the treatment severity. For the less severely treated samples (demineralization and solvent extraction), the XANES spectra were similar, although not identical, to the untreated coal spectra, whereas the more severe treatments (steam at 450{degree}C; peroxyacetic acid at 25{degree}C) showed preferential oxidation of one or more sulfur-bearing phases in the original coal.

  18. Understanding the Zr and Si interdispersion in Zr1-xSixO2 mesoporous thin films by using FTIR and XANES spectroscopy.

    PubMed

    Andrini, Leandro; Angelomé, Paula C; Soler-Illia, Galo J A A; Requejo, Félix G

    2016-06-14

    Zr-Si mixed mesoporous oxides were obtained in a wide range of proportions, from 0 to 30% and from 70 to 100% of Si, using Si(OEt)4 and ZrCl4 as precursors and Pluronic F127 as a template. The oxide mesostructure was characterized by transmission electron microscopy and 2D-small angle X-ray scattering. Fourier transform infrared spectroscopy measurements suggested a local homogeneous interdispersion of both cations. Further selective studies using X-ray Absorption Near Edge Structure (XANES) spectroscopy for separately Zr and Si local environments, allowed for demonstrating that the Zr coordination varies from close to 7 to 6, when its concentration in the mixed oxide is reduced. In addition, it was possible to determine that in mixed oxides with low Zr concentrations, Zr can fit into the spaces occupied by Si in SiO2 pure oxide. An equivalent XANES result was obtained for Si, which is also compatible with the information obtained by FTIR. Furthermore, the Zr-O distance varied from close to 2.2 Å to 1.7 Å when the Zr concentration decreased. Finally, our study also demonstrates the usefulness of XANES to selectively assess the local structure (coordination, symmetry and chemical state) of specific atoms in nanostructured systems. PMID:27001695

  19. Structure, Bonding, and Stability of Mercury Complexes with Thiolate and Thioether Ligands from High-Resolution XANES Spectroscopy and First-Principles Calculations.

    PubMed

    Manceau, Alain; Lemouchi, Cyprien; Rovezzi, Mauro; Lanson, Martine; Glatzel, Pieter; Nagy, Kathryn L; Gautier-Luneau, Isabelle; Joly, Yves; Enescu, Mironel

    2015-12-21

    We present results obtained from high energy-resolution L3-edge XANES spectroscopy and first-principles calculations for the structure, bonding, and stability of mercury(II) complexes with thiolate and thioether ligands in crystalline compounds, aqueous solution, and macromolecular natural organic matter (NOM). Core-to-valence XANES features that vary in intensity differentiate with unprecedented sensitivity the number and identity of Hg ligands and the geometry of the ligand environment. Post-Hartree-Fock XANES calculations, coupled with natural population analysis, performed on MP2-optimized Hg[(SR)2···(RSR)n] complexes show that the shape, position, and number of electronic transitions observed at high energy-resolution are directly correlated to the Hg and S (l,m)-projected empty densities of states and occupations of the hybridized Hg 6s and 5d valence orbitals. Linear two-coordination, the most common coordination geometry in mercury chemistry, yields a sharp 2p to 6s + 5d electronic transition. This transition varies in intensity for Hg bonded to thiol groups in macromolecular NOM. The intensity variation is explained by contributions from next-nearest, low-charge, thioether-type RSR ligands at 3.0-3.3 Å from Hg. Thus, Hg in NOM has two strong bonds to thiol S and k additional weak Hg···S contacts, or 2 + k coordination. The calculated stabilization energy is -5 kcal/mol per RSR ligand. Detection of distant ligands beyond the first coordination shell requires precise measurement of, and comparison to, spectra of reference compounds as well as accurate calculation of spectra for representative molecular models. The combined experimental and theoretical approaches described here for Hg can be applied to other closed-shell atoms, such as Ag(I) and Au(I). To facilitate further calculation of XANES spectra, experimental data, a new crystallographic structure of a key mercury thioether complex, Cartesian coordinates of the computed models, and examples of

  20. Substitution behavior of x(Na{sub 0.5}K{sub 0.5})NbO{sub 3}-(1 − x)BaTiO{sub 3} ceramics for multilayer ceramic capacitors by a near edge x-ray absorption fine structure analysis

    SciTech Connect

    Ha, Jooyeon; Ryu, Jiseung; Lee, Heesoo

    2014-06-30

    The doping effect of (Na{sub 0.5}K{sub 0.5})NbO{sub 3} (NKN) as alternatives for rare-earth elements on the electrical properties of BaTiO{sub 3} has been investigated, in terms of their substitution behavior. The dielectric constant of a specimen with x = 0.05 was about 79% higher than that of pure BaTiO{sub 3}, and the temperature coefficient of capacitance was satisfied by the X7R specification. The specimen with x = 0.05 showed the lowest tetragonality among the four compositions and had a fine grain size of <2 μm. Although the addition of NKN decreased the specimen's tetragonality, the electrical properties were enhanced by the formation of defect dipoles and conduction electrons, which resulted from an acceptor and donor substitution behavior. Through O K-edge near edge x-ray absorption fine structure spectroscopy, the practical substitution behavior was defined by the change in Ti 3d orbital states. The energy separation of the Ti 3d orbitals was more apparent with the specimen of x = 0.05, which is related to the donor level from the donor substitution of Nb{sup 5+} ion for Ti-sites. Therefore, the simultaneous substitution of Na{sup +}/K{sup +} and Nb{sup 5+} ions into BaTiO{sub 3} can improve dielectric properties, based on the charge-transfer process.

  1. Sulfur K-edge XANES and acid volatile sulfide analyses of changes in chemical speciation of S and Fe during sequential extraction of trace metals in anoxic sludge from biogas reactors.

    PubMed

    Shakeri Yekta, Sepehr; Gustavsson, Jenny; Svensson, Bo H; Skyllberg, Ulf

    2012-01-30

    The effect of sequential extraction of trace metals on sulfur (S) speciation in anoxic sludge samples from two lab-scale biogas reactors augmented with Fe was investigated. Analyses of sulfur K-edge X-ray absorption near edge structure (S XANES) spectroscopy and acid volatile sulfide (AVS) were conducted on the residues from each step of the sequential extraction. The S speciation in sludge samples after AVS analysis was also determined by S XANES. Sulfur was mainly present as FeS (≈ 60% of total S) and reduced organic S (≈ 30% of total S), such as organic sulfide and thiol groups, in the anoxic solid phase. Sulfur XANES and AVS analyses showed that during first step of the extraction procedure (the removal of exchangeable cations), a part of the FeS fraction corresponding to 20% of total S was transformed to zero-valent S, whereas Fe was not released into the solution during this transformation. After the last extraction step (organic/sulfide fraction) a secondary Fe phase was formed. The change in chemical speciation of S and Fe occurring during sequential extraction procedure suggests indirect effects on trace metals associated to the FeS fraction that may lead to incorrect results. Furthermore, by S XANES it was verified that the AVS analysis effectively removed the FeS fraction. The present results identified critical limitations for the application of sequential extraction for trace metal speciation analysis outside the framework for which the methods were developed. PMID:22284519

  2. Electronic structure of ZnO nanorods studied by angle-dependent x-ray absorption spectroscopy and scanning photoelectron microscopy

    NASA Astrophysics Data System (ADS)

    Chiou, J. W.; Jan, J. C.; Tsai, H. M.; Bao, C. W.; Pong, W. F.; Tsai, M.-H.; Hong, I.-H.; Klauser, R.; Lee, J. F.; Wu, J. J.; Liu, S. C.

    2004-05-01

    Angle-dependent x-ray absorption near-edge structure (XANES) and scanning photoelectron microscopy measurements were performed to differentiate local electronic structures at the tips and sidewalls of highly aligned ZnO nanorods. The overall intensity of the O K-edge XANES spectra is greatly enhanced for small photon incident angles. In contrast, the overall intensity of the Zn K-edge XANES is much less sensitive to the photon incident angle. Both valence-band photoemission and O K-edge XANES spectra show substantial enhancement of O 2p derived states near the valence band maximum and conduction band minimum, respectively. The spatially resolved Zn 3d core level spectra from tip and sidewall regions show the lack of chemical shift. All the results consistently suggest that the tip surfaces of the highly aligned ZnO nanorods are terminated by O ions and the nanorods are oriented in the [0001¯] direction.

  3. In-situ reflection-XANES study of ZDDP and MoDTC lubricant films formed on steel and diamond like carbon (DLC) surfaces

    NASA Astrophysics Data System (ADS)

    Morina, Ardian; Zhao, Hongyuan; Mosselmans, J. Fred W.

    2014-04-01

    Chemical characterisation of boundary lubricated interfaces is essential for developing mechanistic models that describe lubricant additive interactions with the surface and their effect on tribological performance. In this study the potential for using the synchrotron-based reflection mode X-ray absorption spectroscopy (XAS) technique for in-situ chemical characterisation of lubricant films has been studied. Thermal films formed from zinc dialkyl dithio phosphate (ZDDP) and molybdenum dialkyl dithio carbamate (MoDTC) lubricant additives have been formed and analysed in-situ using the X-ray absorption near edge structure (XANES) spectroscopy technique. The surface sensitivity of this approach was improved by doing the analysis in reflection mode, enabling analysis of only top layer (up to around 10 nm) of the solid surface. In addition, in-lubro analysis of pre-formed tribofilms from the same additives was done using non-vacuum conditions. The results are discussed in conjunction with XANES and X-ray photoelectron spectroscopy (XPS) analysis of similar additives published in the literature. The results obtained are consistent with the existing ZDDP and MoDTC literature and provide some new insight into intermediate species not reported before. The advantages and disadvantages of the developed XANES methodology for in-situ surface chemical analysis of lubricated conditions are discussed.

  4. Comparison of Nickel XANES Spectra and Elemental Maps from a Ureilite, a LL3.8 Ordinary Chondrite, Two Carbonaceous Chondrites and Two Large Cluster IDPs

    NASA Technical Reports Server (NTRS)

    Wirick, S.; Flynn, G. J.; Sutton, S.; Zolensky, M. E.

    2014-01-01

    Nickel in the extraterrestrial world is commonly found in both Fe-Ni sulfide and Fe-Ni met-al forms [1] and in the pure metal state in the interior of iron meteorites where it is not easily oxidized. Ni is also found in olivine, pyroxene and glasses and in some melts the partitioning of Ni between the olivines and glass is controlled by the amount of S in the melt [2]. Its most common valence state is Ni(2+) but Ni also occurs as Ni(0), Ni(+), and Ni(3+) and rarely as Ni(2-), Ni(1-) and Ni(4+) [3]. It's valence state in olivines is Ni(2+) in octa-hedral coordination on the M1 site and rarely on the M2 site.[4]. The chemical sensitivity of X-ray absorp-tion near-edge structure (XANES) spectroscopy is well established and can be used to determine not only va-lence states but also coordination sites [5]. We report here Ni XANES spectroscopy and elemental maps collected from 2 carbonaceous chondrites, 2 large clus-ter IDPs, 1 ureilite and 1 LL3 orginary chondrite.Using XANES it may be possible to find a common trait in the large cluster IDPs that will also be found in mete-orite samples.

  5. New quaternary arsenide oxides with square planar coordination of gold(I) - structure, (197)Au Mössbauer spectroscopic, XANES and XPS characterization of Nd10Au3As8O10 and Sm10Au3As8O10.

    PubMed

    Bartsch, Timo; Niehaus, Oliver; Johrendt, Dirk; Kobayashi, Yasuhiro; Seto, Makoto; Abdala, Paula M; Bartsch, Manfred; Zacharias, Helmut; Hoffmann, Rolf-Dieter; Gerke, Birgit; Rodewald, Ute Ch; Pöttgen, Rainer

    2015-03-28

    The quaternary gold(I) arsenide oxides Nd10Au3As8O10 and Sm10Au3As8O10 were synthesized in sealed quartz ampoules from the rare earth (RE) elements, their appropriate sesquioxides, arsenic, arsenic(III) oxide and finely dispersed gold at maximum annealing temperatures of 1223 K. Both structures were refined from X-ray single crystal diffractometer data at room temperature and at 90 K. Nd10Au3As8O10 and Sm10Au3As8O10 crystallize with a new structure type that derives from the BaAl4 structure through distortions and formation of ordered vacancies. The structures consist of stacked polycationic [RE10O10](10+) layers with oxygen in tetrahedral rare earth coordination and polyanionic [Au(I)3(As2)4](10-) layers with gold in square planar or rectangular planar coordination of four arsenic dumbbells (255 pm As1-As2). In contrast to the well known ionic rare earth oxide layers, the gold arsenide layers rather show covalent bonding and account for the metallic nature of these two new arsenide oxides. This is confirmed by electronic structure calculations and resistivity measurements. The oxidation state of gold was investigated by (197)Au Mössbauer, X-ray absorption near edge structure (XANES) and photoelectron (XPS) spectroscopy. Due to missing comparative gold arsenide compounds, the monovalent gold phosphide oxides RE2AuP2O were measured for comparison. The XANES measurements additionally comprise monovalent gold arsenides REAuAs2. The XPS study contains BaAuAs as reference compound instead. Combination of all data clearly indicates Au(I), which was not observed in square planar coordination up to now. Temperature dependent magnetic susceptibility data show Curie-Weiss paramagnetism for Nd10Au3As8O10 and no magnetic ordering down to 2.5 K. Sm10Au3As8O10 shows the typical Van Vleck type paramagnetism for samarium compounds along with a transition to an antiferromagnetically ordered state at TN = 8.6 K. PMID:25716906

  6. The irradiation of ammonia ice studied by near edge x-ray absorption spectroscopy

    SciTech Connect

    Parent, Ph.; Bournel, F.; Lasne, J.; Laffon, C.; Carniato, S.; Lacombe, S.; Strazzulla, G.; Gardonio, S.; Lizzit, S.; Kappler, J.-P.; Joly, L.

    2009-10-21

    A vapor-deposited NH{sub 3} ice film irradiated at 20 K with 150 eV photons has been studied with near-edge x-ray absorption fine structure (NEXAFS) spectroscopy at the nitrogen K-edge. Irradiation leads to the formation of high amounts (12%) of molecular nitrogen N{sub 2}, whose concentration as a function of the absorbed energy has been quantified to 0.13 molecule/eV. The stability of N{sub 2} in solid NH{sub 3} has been also studied, showing that N{sub 2} continuously desorbs between 20 and 95 K from the irradiated ammonia ice film. Weak concentrations (<1%) of other photoproducts are also detected. Our NEXAFS simulations show that these features own to NH{sub 2}, N{sub 2}H{sub 2}, and N{sub 3}{sup -}.

  7. XANES evidence of arsenate removal from water with magnetic ferrite.

    PubMed

    Tu, Yao-Jen; You, Chen-Feng; Chang, Chien-Kuei; Wang, Shan-Li

    2013-05-15

    Arsenic (As) in groundwater and surface water is a worldwide problem possessing a serious threat to public health. In this study, a magnetic ferrite, was synthesized and investigated for its As(V) removal efficiency. The adsorption of As(V) by magnetic ferrite exhibited an L-shaped nonlinear isotherm, suggesting limiting binding sites on the adsorbent surface. The As K-edge X-Ray Absorption Near-Edge Structure (XANES) revealed that the adsorbed As(V) on ferrite was not reduced to more toxic As(III) by Fe(2+) in the ferrite structure. The maximum As adsorption capacity of ferrite was 14 mg/g at pH 3 and decreased with increasing pH due to enhanced electrostatic repulsion between As(V) and the adsorbent surface. Desorption of As(V) using six different acid and salt solutions showed that the desorption rate decreased in an order of H3PO4 > Na3PO4 > H2SO4 > Na2SO4 > HCl > HNO3. These results suggest that magnetic ferrite without surface modification is an effective adsorbent for removing As(V) from water, which was confirmed by the effective removal of As(V) from contaminated groundwater using this material. The used material can then be recovered using a magnet because of its paramagnetism; the adsorbed As(V) on the material can be recovered using H3PO4 or Na3PO4 solutions. PMID:23507250

  8. Chemical imaging of single catalyst particles with scanning μ-XANES-CT and μ-XRF-CT.

    PubMed

    Price, S W T; Ignatyev, K; Geraki, K; Basham, M; Filik, J; Vo, N T; Witte, P T; Beale, A M; Mosselmans, J F W

    2015-01-01

    The physicochemical state of a catalyst is a key factor in determining both activity and selectivity; however these materials are often not structurally or compositionally homogeneous. Here we report on the 3-dimensional imaging of an industrial catalyst, Mo-promoted colloidal Pt supported on carbon. The distribution of both the active Pt species and Mo promoter have been mapped over a single particle of catalyst using microfocus X-ray fluorescence computed tomography. X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure revealed a mixed local coordination environment, including the presence of both metallic Pt clusters and Pt chloride species, but also no direct interaction between the catalyst and Mo promoter. We also report on the benefits of scanning μ-XANES computed tomography for chemical imaging, allowing for 2- and 3-dimensional mapping of the local electronic and geometric environment, in this instance for both the Pt catalyst and Mo promoter throughout the catalyst particle. PMID:25407850

  9. Humic sulfur in eutrophic bay sediments: Characterization by sulfur stable isotopes and K-edge XANES spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhu, Mao-Xu; Chen, Liang-Jin; Yang, Gui-Peng; Huang, Xiang-Li; Ma, Chen-Yan

    2014-02-01

    Organic sulfur (OS) is an important sedimentary sulfur pool in marine sediments and chemical extractions are often used for quantification of various OS pools, however, OS sources and mechanisms of OS formation are not well understood. In this study, sulfur stable isotope and sulfur X-ray absorption near edge structure (XANES) spectroscopy were combined to investigate the sources and speciation of humic-acid sulfur (HA-S) and fulvic-acid sulfur (FA-S) in sediments of eutrophic Jiaozhou Bay. Whilst there may be some indication that eutrophication has enhanced FA-S burial in the sediment, this has not substantially modified the characteristically low humic sulfur (i.e., HA-S + FA-S) contents of the sediments. Sulfur isotopic compositions indicate that both HA-S and FA-S are mixtures of diagenetic and biosynthetic OS in origin; HA-S is dominated by biosynthetic sulfur and FA-S by diagenetic source. Sulfur isotopic compositions and contents of pyrite and diagenetic OS indicate that inhibition of sulfurization by pyrite formation, if any, appears insignificant. XANES analysis suggests that the contents of high oxidized OS (i.e., sulfones and ester-sulfates) and strongly reduced OS species are comparable in the HA-S, whereas the FA-S is dominated by strongly reduced OS as a result of enhanced sulfurization.

  10. 3D local structure around copper site of rabbit prion-related protein: Quantitative determination by XANES spectroscopy combined with multiple-scattering calculations

    NASA Astrophysics Data System (ADS)

    Cui, P. X.; Lian, F. L.; Wang, Y.; Wen, Yi; Chu, W. S.; Zhao, H. F.; Zhang, S.; Li, J.; Lin, D. H.; Wu, Z. Y.

    2014-02-01

    Prion-related protein (PrP), a cell-surface copper-binding glycoprotein, is considered to be responsible for a number of transmissible spongiform encephalopathies (TSEs). The structural conversion of PrP from the normal cellular isoform (PrPC) to the post-translationally modified form (PrPSc) is thought to be relevant to Cu2+ binding to histidine residues. Rabbits are one of the few mammalian species that appear to be resistant to TSEs, because of the structural characteristics of the rabbit prion protein (RaPrPC) itself. Here we determined the three-dimensional local structure around the C-terminal high-affinity copper-binding sites using X-ray absorption near-edge structure combined with ab initio calculations in the framework of the multiple-scattering (MS) theory. Result shows that two amino acid resides, Gln97 and Met108, and two histidine residues, His95 and His110, are involved in binding this copper(II) ion. It might help us understand the roles of copper in prion conformation conversions, and the molecular mechanisms of prion-involved diseases.