| 1. |
- Butorin, Sergei M., et al.
(författare)
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Chemical Reduction of Actinides Probed by Resonant Inelastic X-ray Scattering
- 2013
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 85:23, s. 11196-11200
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Tidskriftsartikel (refereegranskat)abstract
- The study addresses the possibilities of immobilizing the mobile species of actinides in the geosphere using metallic iron. Sorption on corroding iron is well-known, but there have been uncertainties with regard to the possibilities of reducing the actinyl species to sparingly soluble oxides and, thereby, permanently immobilizing them. Resonant inelastic X-ray scattering (RIXS) measurements at the actinide 5d edges on Fe foils exposed to uranium(VI) and neptunium(V) solutions in groundwater unambigiously indicate reduction of actinides to, respectively, uranium(IV) and neptunium(IV) on iron surfaces. The reduction manifests itself in an appearance of distinct specific signatures of uranium(IV) and neptunium(IV) in the RIXS profile of 5f-5f excitations. Such signatures and RIXS intensity/cross-section behavior with varying energy of incident photons can be reproduced by model atomic-multiplet calculations of the RIXS spectra. By normalizing the RIXS signal of corresponding 5f-5f excitations to core-to-core 6p-to-5d characteristic fluorescence transitions of actinides, their reduction rates on Fe samples with different exposure to actinide solutions can be estimated. Observed reduction implies similar processes in the nuclear waste canister thus suggesting reduced probability of nuclear waste release with ground waters from the canister.
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| 2. |
- Butorin, Sergei
(författare)
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Resonant Inelastic Soft X-ray Scattering Spectroscopy of Light-Actinide Materials
- 2011
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Ingår i: Actinide Nanoparticles Research. - Berlin, Heidelberg : Springer-Verlag New York. - 9783642114311 - 9783642114328 ; , s. 63-104
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Bokkapitel (refereegranskat)abstract
- Resonant inelastic X-ray scattering (RIXS) measurements at the actinide 5d threshold provide an opportunity to study elementary excitations in actinide systems in detail. It has turned out that the technique is very sensitive to the valency and the chemical state of actinide in contrast to X-ray absorption spectroscopy, being hampered by the substantial smearing of spectral structures due to a large core-hole lifetime broadening. In this situation, the virtually unlimited resolution (defined by the response function of the instrument) of the RIXS technique and its ability to enhance transitions to low-lying excited states are especially useful. RIXS spectroscopy provides good signatures in terms of new distinct transitions, representing electronic excitations within the 5f shell and having a characteristic profile. This helps to distinguish between actinide species with different oxidation states, especially in the case when one of the species has a much lower concentration than another. Experimental data for systems of light actinides, such as U, Np, and Pu, are presented and discussed along with the results of model calculations.
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| 3. |
- Kadas, Krisztina, et al.
(författare)
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Structural properties of amorphous metal carbides : Theory and experiment
- 2012
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Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 60:12, s. 4720-4728
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Tidskriftsartikel (refereegranskat)abstract
- By means of theoretical modeling and experimental synthesis and characterization, we investigate the structural properties of amorphous Zr-Si-C. Two chemical compositions are selected: Zr0.31Si0.29C0.40 and Zr0.60Si0.33C0.07. Amorphous structures are generated in the theoretical part of our work by the stochastic quenching (SQ) method, and detailed comparison is made regarding the structure and density of the experimentally synthesized films. These films are analyzed experimentally using X-ray absorption spectroscopy, transmission electron microscopy and X-ray diffraction. Our results demonstrate a remarkable agreement between theory and experiment concerning bond distances and atomic coordination of this complex amorphous metal carbide. The demonstrated power of the SQ method opens up avenues for theoretical predictions of amorphous materials in general.
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| 4. |
- Kapaklis, Vassilios, et al.
(författare)
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Temperature dependence of the electrical resistivity and electronic structure of amorphous Fe100-xZrx films and multilayers
- 2012
-
Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 24:49, s. 495402-
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Tidskriftsartikel (refereegranskat)abstract
- The electrical resistivity of amorphous Fe100-xZrx metal alloy films and multilayers has been investigated in a wide temperature and composition range. The overall behavior of the resistivity is consistent with bulk measurements, exhibiting prominent semiconductor-like changes at low temperatures. The transition from positive (metallic) to negative temperature coefficient of resistivity behavior is accompanied by minute changes in magnetoresistance and we can therefore rule out magnetic phase changes as being the cause for the observed changes in the resistivity. Using x-ray absorption and emission spectroscopies we are able to probe the unoccupied and occupied electronic densities of states. The corresponding spectra are found to significantly overlap, as expected for a metallic-like electronic structure and the absence of a band gap. Besides a broadening of the x-ray emission lines expected from an amorphous material, remarkably small differences are observed in the electronic structures when changing the amount of Zr. The resistivity data were modeled and agreement with the Mott variable range hopping model was found, indicating localized electronic states due the disordered structure of the Fe100-xZrx alloys.
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| 5. |
- Kotani, A., et al.
(författare)
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A new method of directly determining the core-hole effect in the Ce L-3 XAS of mixed valence Ce compounds : An application of resonant X-ray emission spectroscopy
- 2011
-
Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 184:3-6, s. 210-215
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Tidskriftsartikel (refereegranskat)abstract
- Using a simplified model, we calculate resonant X-ray emission (RXE) spectra with Ce 2p to 5d excitation and Ce nl to 2p de-excitation for mixed valence Ce compounds, where nl is 3d or valence states. If the core-hole effect is large to play an important role in the Ce L-3 XAS, the RXE spectral features for nl = 3d and valence states are significantly different, but if it is negligibly small, they are essentially the same. Therefore, these RXE spectra are useful as a new powerful method of directly determining the core-hole effect in the L-3 XAS. More detailed theoretical calculations of these RXE spectra are made for CeO2, and compared with new experimental data, indicating the importance of the core-hole effect. Similar investigations are desirable for some metallic mixed valence Ce compounds in which the core-hole effect is controversial. Finally, we point out that for nl = 5d we can observe the resonant inelastic X-ray scattering spectra corresponding to the charge-transfer excitations or Kondo resonance excitations.
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| 6. |
- Kotani, A., et al.
(författare)
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Spectator and participator processes in the resonant photon-in and photon-out spectra at the Ce L-3 edge of CeO2
- 2012
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Ingår i: European Physical Journal B. - : Springer Science and Business Media LLC. - 1434-6028 .- 1434-6036. ; 85:8, s. 257-
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Tidskriftsartikel (refereegranskat)abstract
- We study both theoretically and experimentally the photon-in and photon-out spectra of CeO2, which are caused by the Ce 2p to Ce 5d excitation followed by the three different de-excitation channels: (i) Ce 3d to Ce 2p (denoted by 3d-RXES), (ii) O 2p to Ce 2p (v-RXES), and (iii) Ce 5d to Ce 2p (RIXS). In 3d- and v-RXES, the 5d electron plays a role of a spectator, but in RIXS it is a participator. By extending our single impurity Anderson model (SIAM), which was used recently for our calculations of v-and 3d-RXES spectra of CeO2, we study the polarization dependence in the spectator and participator spectra, and we perform more detailed calculations for 3d- and v-RXES spectral features, as well as new calculations for the RIXS spectrum with charge transfer excitations. The polarization dependence is different for the spectator and participator spectra; we have no polarization correlation between the incident and emitted photons for the spectator spectra but a strong polarization correlation for the participator spectrum. The theoretical calculations predict that the charge transfer excitations in RIXS occur in the transfer-energy range overlapped with v-RXES, but the RIXS and v-RXES spectra can be discriminated by taking advantage of the different polarization dependence. The overlapped RIXS and v-RXES spectra are observed successfully by our experiments and well reproduced by our SIAM calculations.
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| 7. |
- Kurian, R., et al.
(författare)
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Intrinsic deviations in fluorescence yield detected x-ray absorption spectroscopy : The case of the transition metal L 2,3 edges
- 2012
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 24:45, s. 452201-
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescence yield (FY) detected x-ray absorption spectra (XAS) of 3d transition metal ions are calculated from the integrated 2p3d resonant x-ray emission spectra. The resulting FY-XAS spectra are compared with the normal XAS spectra corresponding to the absorption cross section and significant deviations between the two spectra are found. This implies that the assumption that the FY-XAS spectrum identifies with the XAS spectrum is disproved. Especially for the early transition metal systems the differences between the FY-XAS and XAS are large, due to the opening of inelastic decay channels from selected x-ray absorption final states. The theoretical calculations show that the difference between FY detection and XAS is largest for the detection in depolarized geometry. The calculations are compared with experimental spectra for oxides and coordination compounds for Fe 2+, Co 2+ and Ni 2+ systems. The implications for the sum rules in XAS and magnetic circular dichroism experiments are discussed.
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| 8. |
- Kvashnina, K. O., et al.
(författare)
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Chemical State of Complex Uranium Oxides
- 2013
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 111:25, s. 253002-
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Tidskriftsartikel (refereegranskat)abstract
- We report here the first direct observation of U(V) in uranium binary oxides and analyze the gradual conversion of the U oxidation state in the mixed uranium systems. Our finding clarifies previous contradicting results and provides important input for the geological disposal of spent fuel, recycling applications, and chemistry of uranium species.
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| 9. |
- Kvashnina, Kristina O., et al.
(författare)
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Direct study of the f-electron configuration in lanthanide systems
- 2011
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 26:6, s. 1265-1272
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Tidskriftsartikel (refereegranskat)abstract
- The valence shell electron configurations within a few electron volts above the Fermi level in cerium, ytterbium, europium and samarium compounds were probed by resonant X-ray emission spectroscopy (RXES) at the L-3 absorption pre-edge. The rare earth systems show distinct spectral signatures depending on the f-electron configuration. The high energy resolution experimental results reported here are well reproduced by atomic multiplet calculations confirming the localized character of the 4f electrons. The magnitude of the electron-electron interactions within the 4f shell and between 3d and 4f electrons is analyzed. The present technique is a powerful tool for the study of the 4f valence electron configuration that, unlike L-3 absorption spectroscopy at the main edge, is little influenced by valence electron relaxation following core hole creation.
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| 10. |
- Kvashnina, K. O., et al.
(författare)
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Role of resonant inelastic X-ray scattering in high-resolution core-level spectroscopy of actinide materials
- 2014
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 194, s. 27-36
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Tidskriftsartikel (refereegranskat)abstract
- This paper provides a brief overview of applications of advanced X-ray spectroscopic techniques that take advantage of the resonant inelastic X-ray scattering (RIXS) in the hard and tender X-ray range and have recently become available for studying the electronic structure of actinides. We focus here on the high-energy-resolution X-ray absorption near edge structure (XANES) and core-to-core and core-to-valence RIXS spectroscopies at the U L and M edges of uranium compounds. The spectral features are analyzed using a number of theoretical methods, such as the Anderson impurity model, density functional theory in the local density approximation with an added Coulomb interaction (LDA + U), and full multiple scattering (FEFF) and ab initio finite difference method near-edge structure (FDMNES) codes. In connection with presented results, the capabilities and limitations of the experimental techniques and theoretical methods are discussed. (C) 2014 Elsevier B.V. All rights reserved.
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| 11. |
- Modin, Anders, et al.
(författare)
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Indication of single-crystal PuO2 oxidation from O 1s x-ray absorption spectra
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 83:7, s. 075113-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of single-crystal PuO2 is studied using O 1s x-ray absorption (XA) and x-ray emission. Interpretation of the experimental data is supported by extensive first-principles calculations on the basis of the density functional theory + U approach. The measured XA spectra show a significant difference in intensity for the first two peaks between different spots or areas on the single crystal. Our theoretical simulations show that the first peak, at similar to 531 eV, can be attributed to O 2p-Pu 5f hybridization, while the second peak, at similar to 533.4 eV, is due to hybridization of O 2p with Pu d states. The reasons for the observed differences in the O 1s XA spectra are explored by calculating a number of defect structures PuO2+x as well as by simulating the existence of Pu(V) sites. Our results indicate the presence of oxidation states higher than Pu(IV) in some areas of the single crystal. The findings also suggest that plutonium oxide with a Pu fraction in an oxidation state higher than Pu(IV) consists of inequivalent Pu sites with (PuO2)-O-(IV) and (PuO2)-O-(V) rather than representing a system where the Pu oxidation state is constantly fluctuating between Pu(IV) and Pu(V).
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| 12. |
- Rothe, J., et al.
(författare)
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The INE-Beamline for actinide science at ANKA
- 2012
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 83:4, s. 043105-
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Tidskriftsartikel (refereegranskat)abstract
- Since its inauguration in 2005, the INE-Beamline for actinide research at the synchrotron source ANKA (KIT North Campus) provides dedicated instrumentation for x-ray spectroscopic characterization of actinide samples and other radioactive materials. R&D work at the beamline focuses on various aspects of nuclear waste disposal within INE's mission to provide the scientific basis for assessing long-term safety of a final nuclear waste repository. The INE-Beamline is accessible for the actinide and radiochemistry community through the ANKA proposal system and the European Union Integrated Infrastructure Initiative ACTINET-I3. Experiments with activities up to 1 x 10(+6) times the European exemption limit are feasible within a safe but flexible containment concept. Measurements with monochromatic radiation are performed at photon energies varying between similar to 2.1 keV (P K-edge) and similar to 25 keV (Pd K-edge), including the lanthanide L-edges and the actinide M-and L3-edges up to Cf. The close proximity of the INE-Beamline to INE controlled area labs offers infrastructure unique in Europe for the spectroscopic and microscopic characterization of actinide samples. The modular beamline design enables sufficient flexibility to adapt sample environments and detection systems to many scientific questions. The well-established bulk techniques x-ray absorption fine structure (XAFS) spectroscopy in transmission and fluorescence mode have been augmented by advanced methods using a microfocused beam, including (confocal) XAFS/x-ray fluorescence detection and a combination of (micro-)XAFS and (micro-)x-ray diffraction. Additional instrumentation for high energy-resolution x-ray emission spectroscopy has been successfully developed and tested.
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| 13. |
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| 14. |
- Soroka, Inna L., et al.
(författare)
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Structural stability and oxidation resistance of amorphous Zr-Al alloys
- 2010
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 401:1-3, s. 38-45
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the structural stability and oxidation resistance of Zr-Al films upon annealing in air. The concentration of Zr was varied from 0 to 100 at.%, with a step of 10 at.%. The films were fabricated using ultra-high vacuum based magnetron sputtering. The as-deposited films with Zr content from 17.3 at.% to 70.7 at.% were found to be X-ray amorphous at room temperature. When exposed to air a thin oxide layer, typically less than 6 nm, is formed. The thickness of the oxide layers increases when the samples are annealed in air and most of these are found to be fully oxidized at 700 degrees C with the formation of crystalline and amorphous oxides on the top of crystalline and amorphous metal films, respectively. The amorphous oxide layers are found to be dense, with well defined thicknesses. An experimental non-equilibrium phase diagram is provided, covering the whole concentration range of the Zr-Al system. (C) 2010 Elsevier B.V. All rights reserved.
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| 15. |
- Vegelius, Johan, et al.
(författare)
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Atomic and electronic structure of amorphous Al-Zr alloy films
- 2011
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 23:26, s. 265503-
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Tidskriftsartikel (refereegranskat)abstract
- Amorphous Al73Zr27 alloy film, grown and then subjected to heat treatments at 400 and 700 degrees C, was studied using a combination of x-ray diffraction and soft x-ray spectroscopic techniques. The Al L-2,L-3 and Al K x-ray absorption spectroscopy (XAS) and Al L-2,L-3 x-ray emission spectroscopy (XES) used allowed probing the unoccupied and occupied Al 3s, d states and unoccupied Al 3p states in the sample studied. An irreversible transition from amorphous alloy to a mixture of polycrystalline alloy and amorphous alloy, and then to an amorphous oxide phase was observed. After the annealing at 400 degrees C the Al L-2,L-3 spectra obtained by XAS could be explained as sums of spectra from amorphous Al73Zr27 alloy and (poly) crystalline Al. This indicates that the sample consists of a mixture of Al-rich crystalline and Zr-enhanced amorphous alloys, as compared to the stoichiometry of the as-deposited Al73Zr27 sample, and that the electronic wavefunctions in the crystalline and amorphous regions can be considered to be confined within the respective regions. The relative amounts of Al atoms were found to be around 1: 3 in the crystalline and amorphous phases, respectively, as deduced from the analysis of changes in the electronic structure using Al L-2,L-3 XAS data. The interpretation was confirmed by the Al K XAS and Al L-2,L-3 XES. Upon further annealing at 700 degrees C the polycrystalline phase transformed into amorphous oxide, while the amorphous alloy phase underwent gradual oxidation. The important finding was that the greater part of the sample remained in the amorphous state throughout the temperature regimes described.
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| 16. |
- Vegelius, Johan, 1981-, et al.
(författare)
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Cu Kβ2,5 X-ray emission spectroscopy as a tool for characterization of monovalent copper compounds
- 2012
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Ingår i: Journal of Analytical Atomic Spectrometry. - 0267-9477 .- 1364-5544. ; 27:11, s. 1882-1888
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Tidskriftsartikel (refereegranskat)abstract
- Cu Kβ 2,5 X-ray emission and resonant inelastic X-ray scattering measurements were performed on monovalent and divalent copper compounds. The data were compared with the results of local-density- approximation calculations. The methods were found to be efficient tools for studies of Cu 4p states in the valence band and for distinguishing between different monovalent copper compounds. This is of particular importance for the debate concerning copper corrosion in oxygen-free water.
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| 17. |
- Vegelius, J. R., et al.
(författare)
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X-ray Spectroscopic Study of Cu2S, CuS, and Copper Films Exposed to Na2S Solutions
- 2012
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:42, s. 22293-22300
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of copper sulfides was studied using X-ray absorption at Cu K and L-2,L-3 and S L-2,L-3 edges and X-ray emission spectroscopy at S L-2,L-3 thresholds. The experimental data were compared with results of local density approximation calculations taking into account the calculated valence band contributions and core-level chemical shifts between inequivalent sites. The presence of divalent Cu was detected in CuS with X-ray absorption spectroscopy in the high-energy-resolution fluorescence detection (HERFD) mode. The S L-2,L-3 emission spectrum of CuS was found to be significantly broader than that of Cu2S due to contributions from inequivalent S sites. This difference in the spectral width was used to distinguish between sulfide species formed on the Cu foil exposed to Na2S solutions. The Cu-S interaction processes for Cu films of different thicknesses exposed to Na2S solutions were monitored in situ using X-ray absorption spectroscopy in the HERFD mode at the Cu K edge. It was found that Cu ions were diffusing in the sulfide and entering the solution. The rate at which Cu ions enter the solution via diffusion was estimated on the basis of the results for a 1000 angstrom thick film.
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| 18. |
- Vegelius, Johan, 1981-
(författare)
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X-ray Spectroscopic Studies of Materials for Nuclear Technology
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- X-ray spectroscopic experiments, including X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS), were performed in a large energy range (60-9000 eV) on a variety of systems, probing different elements and orbitals. The systems can preferably be divided into three groups: Actinides, copper systems and amorphous materials. We studied oxidation states of Pu in PuO2 using a closed-source experimental setup, developed by us, to lower the safety restrictions associated with such experiments. The presence of Pu with higher oxidation state than Pu(IV) was found in polycrystalline PuO2. This is an important finding since Pu with higher oxidation states has higher solubility affecting the safety of a proposed undeground repository of spent nuclear fuel which can eventually be infiltrated by groundwater. In the proposed underground repository the molecular oxygen will vanish at some point due to microbial activity and mineral oxidation. At this stage sulfur is the most important candidate for causing copper corrosion. We studied Cu films and foils exposed to sulfide solutions at both Cu L2,3, Cu K and S L2,3 edges and found for example that S L2,3 XES is useful for distinguishing between different copper sulfides and Cu Kβ XES can be used to identify monovalent Cu compounds. Amorphous, zirconium containing alloys are potentially useful materials for future nuclear reactors. The electronic structure of such materials was also investigated.
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| 19. |
- Vitova, T., et al.
(författare)
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High energy resolution x-ray absorption spectroscopy study of uranium in varying valence states
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 82:23, s. 235118-
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Tidskriftsartikel (refereegranskat)abstract
- A high energy resolution x-ray absorption near-edge structure (XANES) spectroscopy study on U4+ (UO2), U5+ ([UO2Py5][KI2Py2]), and U6+ [UO2(NO3)(2)(H2O)(6)] demonstrates the potential of this experimental technique for qualitative/semiqualitative and quantitative actinide speciation investigations. We observe a pre-edge feature with quadrupole nature in a U L-3 edge partial fluorescence yield-XANES spectrum. This feature is a tool for characterizing the participation of 5f orbitals in U-O bonding. The feature origin is explained by performing calculations with the finite difference method near-edge structure code based on the multiple-scattering theory and the finite difference method.
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| 20. |
- Wang, Hongxin, et al.
(författare)
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Nickel Oxidation States and Spin States of Bioinorganic Complexes from Nickel L-edge X-ray Absorption and Resonant Inelastic X-ray Scattering
- 2013
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:47, s. 24767-24772
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Tidskriftsartikel (refereegranskat)abstract
- Soft X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) have been performed on several nickel-containing bioinorganic complexes. RIXS spectral features are shown to be informative and diagnostic for the different oxidation states (Ni-II vs Ni-III) and spin states (high spin Ni-II vs low spin Ni-II) in these bioinorganic systems. In addition to the experimental results, multiplet simulation has also been performed to assist in understanding the observed XAS and RIXS features. These results demonstrate the power and complementarity of RIXS in identifying the electronic states for covalent and biorelevant complexes for the first time and pave the way for potential RIXS application to real biological systems.
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| 21. |
- Werme, Lars, et al.
(författare)
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The Role of the Actinides in a Performance Assessment of a Nuclear Waste Repository. SKB's Supporting Actinide Research
- 2010
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Ingår i: MRS Proceedings. ; 1265, s. AA01-07-
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Tidskriftsartikel (refereegranskat)abstract
- After a few hundred years, the actinides will dominate the radiotoxicity of spent nuclear fuel. This does not necessarily mean that the actinides will dominate the dose to organisms at the surface above a geologic repository. Quite the contrary, in most performance assessments this dose is dominated by long-lived fission products, activation products and, in the very long perspective, actinide daughters.This makes the far-field migration properties of the actinides less interesting for further research. There are, however, other aspects of the presence of actinides in spent nuclear fuel and some of these and SKB's research in these fields is presented and discussed here.
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| 22. |
- Wilkinson, Kai, et al.
(författare)
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Visualization of custom-tailored iron oxide nanoparticles chemistry, uptake, and toxicity
- 2012
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 4:23, s. 7383-7393
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Tidskriftsartikel (refereegranskat)abstract
- Nanoparticles of iron oxide generated by wearing of vehicles have been modelled with a tailored solution of size-uniform engineered magnetite particles produced by the Bradley reaction, a solvothermal metal-organic approach rendering hydrophilic particles. The latter does not bear any pronounced surface charge in analogy with that originating from anthropogenic sources in the environment. Physicochemical properties of the nanoparticles were thoroughly characterized by a wide range of methods, including XPD, TEM, SEM, DLS and spectroscopic techniques. The magnetite nanoparticles were found to be sensitive for transformation into maghemite under ambient conditions. This process was clearly revealed by Raman spectroscopy for high surface energy magnetite particles containing minor impurities of the hydromaghemite phase and was followed by quantitative measurements with EXAFS spectroscopy. In order to assess the toxicological effects of the produced nanoparticles in humans, with and without surface modification with ATP (a model of bio-corona formed in alveolar liquid), a pathway of potential uptake and clearance was modelled with a sequence of in vitro studies using A549 lung epithelial cells, lymphocyte 221-B cells, and 293T embryonal kidney cells, respectively. Raman microscopy unambiguously showed that magnetite nanoparticles are internalized within the A549 cells after 24 h co-incubation, and that the ATP ligand is retained on the nanoparticles throughout the uptake process. The toxicity of the nanoparticles was estimated using confocal fluorescence microscopy and indicated no principal difference for unmodified and modified particles, but revealed considerably different biochemical responses. The IL-8 cytokine response was found to be significantly lower for the magnetite nanoparticles compared to TiO2, while an enhancement of ROS was observed, which was further increased for the ATP-modified nanoparticles, implicating involvement of the ATP signalling pathway in the epithelium.
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| 23. |
- Zhang, Liang, et al.
(författare)
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Probing substrate-induced perturbations on the band structure of graphene on Ni(111) by soft X-ray emission spectroscopy
- 2013
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 580, s. 43-47
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Tidskriftsartikel (refereegranskat)abstract
- The influence of substrate-induced perturbations on the band structure of graphene has been investigated by soft X-ray emission spectroscopy (XES) for graphene on Ni(111). The band-dispersion features of graphene on Ni(111) are different from those of HOPG and 'quasi-freestanding' graphene (graphene/Cu) because of the strong interfacial interaction. By comparing the XES spectra excited with energy at the pi* resonance of HOPG, graphene/Cu and graphene/Ni in detail, we find that the spectral shape change can be directly related to the different electronic states hybridization strength of graphene on metal substrates, supplying a feasible way for investigating the graphene-metal bonding strength. (C) 2013 Elsevier B.V. All rights reserved.
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