| 1. |
- Abdala, Paula M, et al.
(författare)
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Scientific opportunities for heterogeneous catalysis research at the SuperXAS and SNBL beam lines.
- 2012
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Ingår i: CHIMIA. - : Swiss Chemical Society. - 0009-4293 .- 2673-2424. ; 66:9, s. 699-705
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Tidskriftsartikel (refereegranskat)abstract
- In this short review, we describe the complementary experimental capabilities for catalysis research at two beam lines available to the Swiss community, SuperXAS at SLS (Swiss Light Source, Villigen) and SNBL (Swiss Norwegian Beam lines) at ESRF (European Synchrotron Radiation Facility, Grenoble). Over the years, these two facilities have been developed to provide powerful techniques for structural studies under in situ and operando conditions. These techniques, X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and X-ray emission spectroscopy (XES) in combination with Raman or infrared spectroscopy provide new avenues for structure-performance studies of catalysts. Several exemplary studies are used to demonstrate the capability of these facilities.
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| 2. |
- Berger, Gilles, et al.
(författare)
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Insights into the structure-activity relationships of chiral 1,2-diaminophenylalkane platinum(II) anticancer derivatives
- 2015
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Ingår i: Journal of Biological Inorganic Chemistry. - : Springer Science and Business Media LLC. - 0949-8257 .- 1432-1327. ; 20:5, s. 841-853
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Tidskriftsartikel (refereegranskat)abstract
- The structure-activity relationships of chiral 1,2-diaminophenylalkane platinum(II) anticancer derivatives are studied, including interactions with telomeric- and genomic-like DNA sequences, the pKa of their diaqua species, structural properties obtained from DFT calculations and resonant X-ray emission spectroscopy. The binding modes of the compounds to telomeric sequences were elucidated, showing no major differences with conventional cis-platinum(II) complexes like cisplatin, supporting that the cis-square planar geometry governs the binding of small Pt(II) complexes to G4 structures. Double-stranded DNA platination kinetics and acid-base constants of the diaqua species of the compounds were measured and compared, highlighting a strong steric dependence of the DNA-binding kinetics, but independent to stereoisomerism. Structural features of the compounds are discussed on the basis of dispersion-corrected DFT, showing that the most active series presents conformers for which the platinum atom is well devoid of steric hindrance. If reactivity indices derived from conceptual DFT do not show evidences for different reactivity between the compounds, RXES experiments provide new insight into the availability of platinum orbitals for binding to nucleophiles.
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| 3. |
- Berger, Gilles, et al.
(författare)
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Reduction Mechanisms of Anticancer Osmium(VI) Complexes Revealed by Atomic Telemetry and Theoretical Calculations
- 2021
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 60:9, s. 6663-6671
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Tidskriftsartikel (refereegranskat)abstract
- Resonant X-ray emission spectroscopy (RXES) has developed in the past decade as a powerful tool to probe the chemical state of a metal center and in situ study chemical reactions. We have used it to monitor spectral changes associated with the reduction of osmium(VI) nitrido complexes to the osmium(III) ammine state by the biologically relevant reducing agent, glutathione. RXES difference maps are consistent with the proposed DFT mechanism and the formation of two stable osmium(IV) intermediates, thereby supporting the overall pathway for the reduction of these high-valent anticancer metal complexes for which reduction by thiols within cells may be essential to the antiproliferative activity.
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| 4. |
- Blachucki, Wojciech, et al.
(författare)
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A laboratory-based double X-ray spectrometer for simultaneous X-ray emission and X-ray absorption studies
- 2019
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry. - 0267-9477 .- 1364-5544. ; 34:7, s. 1409-1415
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Tidskriftsartikel (refereegranskat)abstract
- X-ray spectroscopy studies are usually performed using synchrotron radiation sources, which offer bright, coherent, energy-tuneable and monochromatic light. However, the application of synchrotron-based Xray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) is directly constrained by the limited, infrequent access to central facilities. With the advent of new technological solutions in the field of X-ray sources, optics and detectors, the development of efficient and compact laboratory X-ray spectroscopy systems is possible. A permanent laboratory-based setup offers the advantages of low cost and easy accessibility and, therefore, more flexibility in the preparation and scheduling of measurements. Herein, we report a laboratory X-ray setup allowing simultaneous XES and XAS measurements. The double von Hamos spectrometer performances are demonstrated by concurrent K beta XES and K-edge XAS measurements done for 3d elements.
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| 5. |
- Blachucki, Wojciech, et al.
(författare)
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Approaching the Attosecond Frontier of Dynamics in Matter with the Concept of X-ray Chronoscopy
- 2022
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Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- Featured Application Herein, an innovative methodology, called X-ray chronoscopy, is proposed for exploration of ultrafast processes in matter with attosecond precision using current XFEL sources. The method is based on measuring the change in an X-ray pulse temporal profile induced by interaction with a medium. X-ray free electron lasers (XFELs) have provided scientists opportunities to study matter with unprecedented temporal and spatial resolutions. However, access to the attosecond domain (i.e., below 1 femtosecond) remains elusive. Herein, a time-dependent experimental concept is theorized, allowing us to track ultrafast processes in matter with sub-fs resolution. The proposed X-ray chronoscopy approach exploits the state-of-the-art developments in terahertz streaking to measure the time structure of X-ray pulses with ultrahigh temporal resolution. The sub-femtosecond dynamics of the saturable X-ray absorption process is simulated. The employed rate equation model confirms that the X-ray-induced mechanisms leading to X-ray transparency can be probed via measurement of an X-ray pulse time structure.
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| 6. |
- Błachucki, Wojciech, et al.
(författare)
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High energy resolution off-resonant spectroscopy : A review
- 2017
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier BV. - 0584-8547 .- 1873-3565. ; 136:Supplement C, s. 23-33
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Forskningsöversikt (refereegranskat)abstract
- We review the high energy resolution off-resonant spectroscopy (HEROS) technique. HEROS probes the unoccupied electronic states of matter in a single-shot manner thanks to the combination of off-resonant excitation around atomic core states using wavelength dispersive X-ray detection setups. In this review we provide a general introduction to the field of X-ray spectroscopy together with the specification of the available X-ray techniques and X-ray methodologies. Next, the theoretical description of the HEROS approach is introduced with a special focus on the derivation of the X-ray emission and X-ray absorption correspondence relation at off-resonant excitation conditions. Finally, a number of experimental HEROS reports are reviewed in the field of chemistry and material science. We emphasize the applicability of HEROS to pulsed X-ray sources, like X-ray free electron lasers, and support the review with experimental examples. The review is complemented with perspectives on and possible further applications of the HEROS technique to the field of X-ray science.
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| 7. |
- Blachucki, Wojciech, et al.
(författare)
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In situ high energy resolution off-resonant spectroscopy applied to a time-resolved study of single site Ta catalyst during oxidation
- 2017
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : ELSEVIER SCIENCE BV. - 0168-583X .- 1872-9584. ; 411, s. 63-67
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Tidskriftsartikel (refereegranskat)abstract
- In the present work high energy resolution off-resonant X-ray spectroscopy (HEROS) was employed at a synchrotron to study a silica supported Ta(V) bisalkyl catalyst activated in hydrogen. The Ta L alpha(1) HEROS spectra were measured during oxidation of the starting complex and the relative species' concentration was successfully retrieved as a function of time using the fingerprint HEROS spectra measured for the unoxidized and the oxidized catalyst. Based on the experimental data and theory-based calculations, it was shown that oxidation of the active Ta catalyst leads to the formation of mono- and di-meric species on the SiO2 surface. The obtained results were compared to those of the previously reported time resolved HEROS study on an inactive silica supported Ta(V) bisalkyl catalyst's concentration evolution during its oxidation Blachucki et al. (2015). The study allowed observation of an immediate transition of the active Ta catalyst from its unoxidized form to the oxidized one. This finding is dissimilar to the result of the study on the inactive Ta catalyst, where the oxidation led through an intermediate step.
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| 8. |
- Blachucki, Wojciech, et al.
(författare)
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Resonant X-ray Emission Spectroscopy with a SASE Beam
- 2021
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 11:18
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Tidskriftsartikel (refereegranskat)abstract
- Featured Application In the present work, RXES planes are reconstructed with high energy resolution from the experimental spectra of the X-ray radiation emitted from a sample and of incident X-ray pulses delivered by an XFEL operated in the raw SASE mode. The dependence of the reconstructed RXES planes' quality on the number of recorded XFEL shots is studied. Aqueous iron (III) oxide nanoparticles were irradiated with pure self-amplified spontaneous emission (SASE) X-ray free-electron laser (XFEL) pulses tuned to the energy around the Fe K-edge ionization threshold. For each XFEL shot, the incident X-ray pulse spectrum and Fe K beta emission spectrum were measured synchronously with dedicated spectrometers and processed through a reconstruction algorithm allowing for the determination of Fe K beta resonant X-ray emission spectroscopy (RXES) plane with high energy resolution. The influence of the number of X-ray shots employed in the experiment on the reconstructed data quality was evaluated, enabling the determination of thresholds for good data acquisition and experimental times essential for practical usage of scarce XFEL beam times.
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| 9. |
- Blachucki, Wojciech, et al.
(författare)
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Study of the reactivity of silica supported tantalum catalysts with oxygen followed by in situ HEROS
- 2015
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 17:28, s. 18262-18264
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Tidskriftsartikel (refereegranskat)abstract
- We report on the reactivity of grafted tantalum organometallic catalysts with molecular oxygen. The changes in the local Ta electronic structure were followed by in situ high-energy resolution off-resonant spectroscopy (HEROS). The results revealed agglomeration and formation of Ta dimers, which cannot be reversed. The process occurs independently of starting grafted complex.
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| 10. |
- Czapla-Masztafiak, Joanna, et al.
(författare)
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Direct Determination of Metal Complexes' Interaction with DNA by Atomic Telemetry and Multiscale Molecular Dynamics
- 2017
-
Ingår i: The Journal of Physical Chemistry Letters. - : AMER CHEMICAL SOC. - 1948-7185. ; 8:4, s. 805-811
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Tidskriftsartikel (refereegranskat)abstract
- The lack of molecular mechanistic understanding of the interaction between metal complexes and biomolecules hampers their potential medical use. Herein we present a robust procedure combining resonant X-ray emission spectroscopy and multiscale molecular dynamics simulations, which allows for straightforward elucidation of the precise interaction mechanism at the atomic level. The report unveils an unforeseen hydrolysis process and DNA binding of [Pt{N(p-HC6F4)CH2}(2)py(2)] (Pt103), which showed potential cytotoxic activity in the past. Pt103 preferentially coordinates to adjacent adenine sites, instead of guanine sites as in cisplatin, because of its hydrogen bond ability. Comparison with previous research on cisplatin suggests that selective binding to guanine or adenine may be achieved by controlling the acidity of the compound.
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| 11. |
- Czapla-Masztafiak, Joanna, et al.
(författare)
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Investigating DNA Radiation Damage Using X-Ray Absorption Spectroscopy
- 2016
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Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 110:6, s. 1304-1311
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Tidskriftsartikel (refereegranskat)abstract
- The biological influence of radiation on living matter has been studied for years; however, several questions about the detailed mechanism of radiation damage formation remain largely unanswered. Among all biomolecules exposed to radiation, DNA plays an important role because any damage to its molecular structure can affect the whole cell and may lead to chromosomal rearrangements resulting in genomic instability or cell death. To identify and characterize damage induced in the DNA sugar-phosphate backbone, in this work we performed x-ray absorption spectroscopy at the P K-edge on DNA irradiated with either UVA light or protons. By combining the experimental results with theoretical calculations, we were able to establish the types and relative ratio of lesions produced by both UVA and protons around the phosphorus atoms in DNA.
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| 12. |
- Czapla-Masztafiak, Joanna, et al.
(författare)
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Mechanism of hydrolysis of a platinum(IV) complex discovered by atomic telemetry
- 2018
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Ingår i: Journal of Inorganic Biochemistry. - : ELSEVIER SCIENCE INC. - 0162-0134 .- 1873-3344. ; 187, s. 56-61
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Tidskriftsartikel (refereegranskat)abstract
- Herein we report on the hydrolysis mechanism of [Pt{N(p-HC6F4)CH2}(2)(NC5H5)(2)(OH)(2)], a platinum(IV) complex that exhibits anti-cancer properties. Atomic telemetry, an in situ technique based on electron structure sensitive X-ray spectroscopy, revealed that hydrolysis preceded any reduction of the metal center. The obtained results are complemented with F-19 NMR measurements and theoretical calculations and support the observation that this Pt-II complex does not reduce spontaneously to Ptll in HEPES buffer solution at pH 7.4 and after 24 h incubation. These results are of importance for the design of novel Pt-based coordination complexes as well as understanding their behavior under physiological conditions.
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| 13. |
- Garlisi, Corrado, et al.
(författare)
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E-beam evaporated TiO2 and Cu-TiO2 on glass : Performance in the discoloration of methylene blue and 2-propanol oxidation
- 2016
-
Ingår i: Applied Catalysis A. - : Elsevier BV. - 0926-860X .- 1873-3875. ; 526, s. 191-199
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Tidskriftsartikel (refereegranskat)abstract
- TiO2 and Cu-TiO2 thin films were deposited by e-beam evaporation and then annealed at 350 and 500 degrees C. Their structure, surface morphology and optical properties were studied by X-ray diffraction, scanning electron microscopy, cross-sectional TEM, UV-vis, FT-IR spectroscopy and X-ray absorption spectroscopy. A single-phase source material was used for the first time in the deposition process, thus avoiding preferential evaporation of Cu with respect to TiO2, and resulting in an even concentration of Cu in the doped films. The photocatalytic activity was evaluated by degradation of pre-adsorbed methylene blue (MB) in dry conditions and gaseous 2-propanol in oxygen atmosphere under visible and simulated solar light, respectively. Results suggested that high surface hydroxylation of the as-deposited films is an important factor for MB oxidation occurring through a dye-sensitized mechanism activated by visible light absorption. Conversely, the rate of photodegradation of 2-propanol is enhanced in annealed samples due to the greater crystallinity and less electron-hole recombination, with the TiO2 annealed at 500 degrees C being the most efficient photocatalyst. However, Cu-doped samples resulted the most active samples during the degradation of MB under visible radiation. Finally, the performance at increasing thickness (250, 500, 1000, up to 2000 nm) was tested for the most reactive films revealing a marked rise in photocatalytic activity up to 1000 nm.
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| 14. |
- Garlisi, Corrado, et al.
(författare)
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N-TiO2/Cu-TiO2 double-layer films : Impact of stacking order on photocatalytic properties
- 2017
-
Ingår i: Journal of Catalysis. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0021-9517 .- 1090-2694. ; 353, s. 116-122
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we report for the first time a unique configuration of N-doped and Cu-doped TiO2 bilayer. The activity of TiO2 was improved by combining Cu- and N-doping in a layered thin-film structure. The impact of the stacking order was studied, pointing out how the best arrangement is by far the one with Cu-TiO2 as the top layer. The results reveal a unique and simple way to enhance the photocatalytic response of TiO2 in the visible domain.
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| 15. |
- Gizinski, Damian, et al.
(författare)
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On-the-fly Catalyst Accretion and Screening in Chemoselective Flow Hydrogenation
- 2018
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Ingår i: ChemCatChem. - : WILEY-V C H VERLAG GMBH. - 1867-3880 .- 1867-3899. ; 10:17, s. 3641-3646
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Tidskriftsartikel (refereegranskat)abstract
- Herein, it is reported an on-the-fly accretion/reaction protocol to evaluate the structure-performance relationship in the chemoselective flow citral hydrogenation over Ni-based catalysts. Based on the methodology one was able to determine Ni nanoparticles ideal average size (ca. 9nm), in a rapid and facile manner. The methodology offers a simple workflow, cost-effective and adaptable strategy for process intensification and optimization.
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| 16. |
- Goszewska, Ilona, et al.
(författare)
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Boosting the Performance of Nano-Ni Catalysts by Palladium Doping in Flow Hydrogenation of Sulcatone
- 2020
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Ingår i: Catalysts. - : MDPI. - 2073-4344. ; 10:11
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of Pd doping on nano-Ni catalyst hydrogenation aptitude in sulcatone (6-methyl-5-hepten-2-one) hydrogenation was investigated. Obtained results demonstrated that the addition of non-catalytic amounts of Pd to the surface of parent Ni catalyst improves the activity to the extent that it surpassed the activity of 2.16 wt% Pd catalyst (model catalyst) at optimal reaction conditions in the flow hydrogenation of an unsaturated ketone. Pd doping improves hydrogen activation on the catalyst, which was found to be a rate-limiting step using kinetic isotopic measurements and theoretical calculations.
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| 17. |
- Hartfelder, Urs, et al.
(författare)
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Determination of catalytic reaction mechanisms by isotopic frequency response.
- 2012
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 137:22, s. 5374-81
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Tidskriftsartikel (refereegranskat)abstract
- Efficient catalysts are of extraordinary importance for the development of efficient chemical processes as well as applications such as energy storage. Rational development of catalysts requires a mechanistic understanding of the catalytic reaction. Since steady-state investigations are insufficient to gain mechanistic understanding, transient methods such as SSITKA and frequency response have been developed. In this paper we provide a theoretical basis for a frequency response method based on variations in the isotopic composition of the reactant. This approach is particularly useful, since it permits transient investigations under quasi-steady state conditions and because the response is linear.
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| 18. |
- Kayser, Yves, et al.
(författare)
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Depth-Resolved X-ray Absorption Spectroscopy by Means of Grazing Emission X-ray Fluorescence
- 2015
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 87:21, s. 10815-10821
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Tidskriftsartikel (refereegranskat)abstract
- Grazing emission X-ray fluorescence (GEXRF) is well suited for nondestructive elemental-sensitive depth-profiling measurements on samples with nanometer-sized features. By varying the grazing emission angle under which the X-ray fluorescence signal is detected, the probed depth range can be tuned from a few to several hundred nanometers. The dependence of the XRF intensity on the grazing emission angle can be assessed in a sequence of measurements or in a scanning-free approach using a position-sensitive area detector. Hereafter, we will show that the combination of scanning-free GEXRF and fluorescence detected X-ray absorption spectroscopy (XAS) allows for depth-resolved chemical speciation measurements with nanometer-scale accuracy. While the conventional grazing emission geometry is advantageous to minimize self-absorption effects, the use of a scanning-free setup makes the sequential scanning of the grazing emission angles obsolete and paves the way toward time-resolved depth-sensitive XAS measurements. The presented experimental approach was applied to study the surface oxidation of an Fe layer on the top of bulk Si and of a Ge bulk sample. Thanks to the penetrating properties and the insensitivity toward the electric conduction properties of the incident and emitted X-rays, the presented experimental approach is well suited for in situ sample surface studies in the nanometer regime.
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| 19. |
- Kayser, Yves, et al.
(författare)
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Nanoparticle characterization by means of scanning free grazing emission X-ray fluorescence.
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 7:20, s. 9320-9330
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Tidskriftsartikel (refereegranskat)abstract
- Nanoparticles are considered for applications in domains as various as medical and pharmaceutical sciences, opto- and microelectronics, catalysis, photovoltaics, spintronics or nano- and biotechnology. The applications realized with nanocrystals depend strongly on the physical dimensions (shape and size) and elemental constitution. We demonstrate here that grazing emission X-ray fluorescence (GEXRF) is an element sensitive technique that presents the potential for a reliable and accurate determination of the morphology of nanoparticles deposited on a flat substrate (ready-to-use devices). Thanks to the scanning-free approach of the used GEXRF setup, the composition, shape and average size of nanoparticles are determined in short time intervals, minimizing the exposure to radiation. The (scanning-free) GEXRF technique allows for in situ investigations of the nanoparticulate systems thanks to the penetration properties of both the probe X-ray beam and the emitted X-ray fluorescence signal.
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| 20. |
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| 21. |
- Lipiec, Ewelina, et al.
(författare)
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Novel in situ methodology to observe the interactions of chemotherapeutical Pt drugs with DNA under physiological conditions.
- 2014
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43:37, s. 13839-44
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Tidskriftsartikel (refereegranskat)abstract
- The binding of the antitumor drug cisplatin with DNA was determined by means of in situ resonant inelastic X-ray scattering (RIXS) spectroscopy. Because of the penetrating properties of hard X-rays, we could determine, under physiological conditions, the identity and number of platinum complexes present. In situ RIXS revealed that under physiological conditions, water molecules replace chloride ligands owing to drug hydration. The subsequent interaction with DNA, led to the bonding of the aqua complexes into the DNA structure with simultaneous loss of the coordinating water and chloride ion. The data analysis reveals that Pt is coordinated by two adjacent guanines giving cis-[Pt(NH3)2{d(GpG)-N7(1),-N7(2)}] upon losing its coordinating water or chloride ligands.
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| 22. |
- Makosch, Martin, et al.
(författare)
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HERFD XAS/ATR-FTIR batch reactor cell.
- 2012
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 14:7, s. 2164-70
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Tidskriftsartikel (refereegranskat)abstract
- An autoclave reactor was modified to perform simultaneously high energy resolution fluorescence detected X-ray absorption spectroscopy (HERFD XAS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy measurements without altering the reactor design. This operando cell allows one to follow changes in the electronic and geometric structure of the catalyst with HERFD XAS and relate them to the simultaneously detected activity and reaction species with ATR-FTIR formed during the reaction in the liquid phase. The capability of the cell is demonstrated by two studies. The first shows the reduction of Au/CeO(2) precursors in different solvents. The second shows that mainly Au(0) is present in the hydrogenation of nitrobenzene over Au/CeO(2).
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| 23. |
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| 24. |
- Milne, Christopher J., et al.
(författare)
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Disentangling the evolution of electrons and holes in photoexcited ZnO nanoparticles
- 2023
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Ingår i: Structural Dynamics. - : American Institute of Physics (AIP). - 2329-7778. ; 10:6
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of charge carriers in photoexcited room temperature ZnO nanoparticles in solution is investigated using ultrafast ultraviolet photoluminescence spectroscopy, ultrafast Zn K-edge absorption spectroscopy, and ab initio molecular dynamics (MD) simulations. The photoluminescence is excited at 4.66 eV, well above the band edge, and shows that electron cooling in the conduction band and exciton formation occur in <500 fs, in excellent agreement with theoretical predictions. The x-ray absorption measurements, obtained upon excitation close to the band edge at 3.49 eV, are sensitive to the migration and trapping of holes. They reveal that the 2 ps transient largely reproduces the previously reported transient obtained at 100 ps time delay in synchrotron studies. In addition, the x-ray absorption signal is found to rise in similar to 1.4 ps, which we attribute to the diffusion of holes through the lattice prior to their trapping at singly charged oxygen vacancies. Indeed, the MD simulations show that impulsive trapping of holes induces an ultrafast expansion of the cage of Zn atoms in <200 fs, followed by an oscillatory response at a frequency of similar to 100 cm-1, which corresponds to a phonon mode of the system involving the Zn sub-lattice.
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| 25. |
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| 26. |
- Pavliuk, Mariia V., et al.
(författare)
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Hydrated Electron Generation by Excitation of Copper Localized Surface Plasmon Resonance
- 2019
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 10:8, s. 1743-1749
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Tidskriftsartikel (refereegranskat)abstract
- Hydrated electrons are important in radiation chemistry and charge transfer reactions, with applications that include chemical damage of DNA, catalysis, and signaling. Conventionally, hydrated electrons are produced by pulsed radiolysis, sonolysis, two-ultraviolet-photon laser excitation of liquid water, or photodetachment of suitable electron donors. Here we report a method for the generation of hydrated electrons via single-visible-photon excitation of localized surface plasmon resonances (LSPRs) of supported sub-3 nm copper nanoparticles in contact with water. Only excitations at the LSPR maximum resulted in the formation of hydrated electrons, suggesting that plasmon excitation plays a crucial role in promoting electron transfer from the nanoparticle into the solution. The reactivity of the hydrated electrons was confirmed via proton reduction and concomitant H-2 evolution in the presence of a Ru/TiO2 catalyst.
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| 27. |
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| 28. |
- Sá, Jacinto, et al.
(författare)
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Controlling dark catalysis with quasi half-cycle terahertz pulses
- 2017
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Ingår i: Catalysis Science & Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 7:5, s. 1050-1054
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Tidskriftsartikel (refereegranskat)abstract
- This study reports the changes in the platinum electronic structure induced by a strong electric field originated from quasi half-cycle THz pulses, which forces the C-O molecule to dissociate. The changes could be rationalized via a simple analysis of the local density-of-states and easily characterised via high resolution X-ray absorption spectroscopy (HR-XAS). Thus, conferring half-cycle THz pulses the capability of triggering dark catalytic processes required to follow real time catalytic bond rupture or formation, i.e., time-resolved measurements using THz as the pump and HR-XAS as the probe.
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| 29. |
- Sá, Jacinto, et al.
(författare)
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Differences between bulk and surface electronic structure of doped TiO2 with soft-elements (C, N and S)
- 2018
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Ingår i: Materials Chemistry and Physics. - : ELSEVIER SCIENCE SA. - 0254-0584 .- 1879-3312. ; 208, s. 281-288
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we report a systematic study on the electronic structure of surface and bulk TiO2 doped with C, N or S. The results were attained with a semi-empirical method consisting of a combination between resonant X-ray emission spectroscopy (RXES) measurements and localized density of states (LDOS) simulations. Experimental TiO2 RXES data was used to fit FEFF code empirical parameters, and subsequently frozen for the theoretical analysis of LDOS of TiO2 doped materials. The results show significant electronic structure differences between bulk and surface doping, as well as in the nearest Ti atom electronic structure if it is located at the surface or sub-surface, with potential consequences to the photo-catalytic process. The methodology can be adapted to study other dopants, morphologies, structures and surface terminations and as well as other inorganic semiconductors.
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| 30. |
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| 31. |
- Sá, Jacinto, et al.
(författare)
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Evaluation of Pt and Re oxidation state in a pressurized reactor : difference in reduction between gas and liquid phase.
- 2011
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 47:23, s. 6590-2
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Tidskriftsartikel (refereegranskat)abstract
- Determination of metal oxidation state under relevant working conditions is crucial to understand catalytic behaviour. The reduction behaviour of Pt and Re was evaluated simultaneously as a function of support and solvent in a pressurized reactor (autoclave). The bimetallic catalysts are used in selective hydrogenation of carboxylic acids and amides. Gas phase reduction reduced the metals more efficiently, in particular Pt.
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| 32. |
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| 33. |
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| 34. |
- Sá, Jacinto, et al.
(författare)
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Magnetic manipulation of molecules on a non-magnetic catalytic surface.
- 2013
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 5:18, s. 8462-5
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Tidskriftsartikel (refereegranskat)abstract
- Non-magnetic Pt catalysts, supported on carbon coated magnetic Co nanoparticles, changed catalytic performance in the presence of an external magnetic field. This behavior relates to an electronic change of Pt induced by a localized magnetic field, which modifies the CO adsorption geometry. In situ resonant inelastic X-ray scattering (RIXS) experiments and theory reveal the change of atop CO adsorption geometry on the Pt catalyst to bridged geometry under an external magnetic field. This observation opens the possibility of catalytic control by means of an external magnetic field.
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| 35. |
- Sa, Jacinto, et al.
(författare)
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Resonant X-ray emission spectroscopy of platinum(II) anticancer complexes
- 2016
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 141:4, s. 1226-1232
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Tidskriftsartikel (refereegranskat)abstract
- Platinum-based drugs are commonly used in cancer treatment. The biological activity of a metallodrug is obviously closely related to its chemical and stereochemical characteristics. An overlooked aspect is the effect of the ligand to the electronic structure of the metal atom (coordinated atom). We report herein a Resonant X-ray Emission Spectroscopy (RXES) study on the chemical speciation of chiral platinum complexes in which diastereomers are distinguished on the basis of their metal electronic configuration. This demonstrates RXES high chemical speciation capabilities, a necessary property to further investigate the reactivity of the Pt atom towards nucleophiles or bionucleophiles, and an important complement the previously reported RXES abilities, namely that it can be employed for in situ studies at physiological concentrations.
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| 36. |
- Sá, Jacinto, et al.
(författare)
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Temperature-programmed reduction of NiO nanoparticles followed by time-resolved RIXS.
- 2014
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 16:17, s. 7692-6
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of nano-NiO was determined using resonant inelastic X-ray scattering (RIXS) spectroscopy. The nanosized NiO particles were reduced in situ, leading to the formation of metallic Ni in a single step. Time-resolved RIXS elucidated in real time the changes on the occupied and unoccupied electronic structure of the material, which are dramatically affected by the reduction process.
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| 37. |
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| 38. |
- Sá, Jacinto, et al.
(författare)
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The use of Resonant X-ray Emission Spectroscopy (RXES) for the electronic analysis of metal complexes and their interactions with biomolecules.
- 2015
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Ingår i: Drug Discovery Today. - : Elsevier BV. - 1740-6749. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- This review presents a new application of Resonant X-ray Emission Spectroscopy (RXES) to study the mechanism of action of metal containing anticancer derivatives and in particular platinum in situ and in vivo. The technique is an example of a photon-in photon-out X-ray spectroscopic approach, which enables chemical speciation of drugs to be determined and therefore to derive action mechanisms, and to determine drug binding rates under physiological conditions and therapeutic concentrations. This is made feasible due to the atomic specificity and high penetration depth of RXES. The review presents examples of the three main types of information that can be obtained by RXES and establishes an experimental protocol to perfect the measurements within cells.
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| 39. |
- Sá, Jacinto, et al.
(författare)
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Transient mid-IR study of electron dynamics in TiO2 conduction band.
- 2013
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 138:7, s. 1966-70
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of TiO2 conduction band electrons were followed with a novel broadband synchrotron-based transient mid-IR spectroscopy setup. The lifetime of conduction band electrons was found to be dependent on the injection method used. Direct band gap excitation results in a lifetime of 2.5 ns, whereas indirect excitation at 532 nm via Ru-N719 dye followed by injection from the dye into TiO2 results in a lifetime of 5.9 ns.
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| 40. |
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| 41. |
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| 42. |
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| 43. |
- Szlachetko, Jakub, et al.
(författare)
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Establishing nonlinearity thresholds with ultraintense X-ray pulses
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- X-ray techniques have evolved over decades to become highly refined tools for a broad range of investigations. Importantly, these approaches rely on X-ray measurements that depend linearly on the number of incident X-ray photons. The advent of X-ray free electron lasers (XFELs) is opening the ability to reach extremely high photon numbers within ultrashort X-ray pulse durations and is leading to a paradigm shift in our ability to explore nonlinear X-ray signals. However, the enormous increase in X-ray peak power is a double-edged sword with new and exciting methods being developed but at the same time well-established techniques proving unreliable. Consequently, accurate knowledge about the threshold for nonlinear X-ray signals is essential. Herein we report an X-ray spectroscopic study that reveals important details on the thresholds for nonlinear X-ray interactions. By varying both the incident X-ray intensity and photon energy, we establish the regimes at which the simplest nonlinear process, two-photon X-ray absorption (TPA), can be observed. From these measurements we can extract the probability of this process as a function of photon energy and confirm both the nature and sub-femtosecond lifetime of the virtual intermediate electronic state.
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| 44. |
- Szlachetko, Jakub, et al.
(författare)
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Hidden gapless states during thermal transformations of preorganized zinc alkoxides to zinc oxide nanocrystals
- 2018
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Ingår i: Materials Horizons. - : Royal Society of Chemistry (RSC). - 2051-6347 .- 2051-6355. ; 5:5, s. 905-911
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Tidskriftsartikel (refereegranskat)abstract
- Zinc oxide (ZnO) is one of the most versatile semiconductor materials with multifarious potential applications. Easily accessible alkylzinc alkoxides have been widely exploited as single-source precursors of ZnO-based nanomaterials but their multi-step decomposition pathways have not been understood in detail. Herein, the formation mechanism of ZnO nanocrystals via solid-state thermal decomposition of a model pre-organised alkylzinc alkoxide precursor, i.e. [tBuZn(mu(3)-OtBu)](4), is elucidated using in situ valence-to-core X-ray emission (v2c-XES) and high energy resolution off-resonant spectroscopy (HEROS) in conjunction with theoretical calculations. Combination of in situ spectroscopic measurements and theoretical simulations indicates that the precursor structural evolution is initiated by the homolytic cleavage of the R-Zn bond, which leads to the formation of a transient radical ([center dot Zn(mu(3)-OR)][RZn(mu(3)-OR)](3)) species, which is responsible for the initial decomposition process. The ensuing multistep transformations involve the formation of intermediate radical zinc oxo-alkoxide clusters with gapless electronic states. Hitherto, the formation of clusters of this type has not been considered either as intermediate structures en route to a semiconductor ZnO phase or as potential species accounting for various defect states of ZnO NCs, particularly the singly charged oxygen vacancy, V-o(+).
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| 45. |
- Szlachetko, Jakub, et al.
(författare)
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High energy resolution off-resonant spectroscopy at sub-second time resolution : (Pt(acac)2) decomposition.
- 2012
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 48:88, s. 10898-900
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Tidskriftsartikel (refereegranskat)abstract
- We report on the decomposition of platinum acetylacetonate (Pt(acac)(2)) in hydrogen induced by flash heating. The changes in the local Pt structure were followed by high energy resolution off-resonant spectroscopy uniquely performed with sub-second time resolution. The decomposition consists of a two-step reduction process of the Pt(II) species.
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| 46. |
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| 47. |
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| 48. |
- Szlachetko, Jakub, et al.
(författare)
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Subsecond and in situ chemical speciation of Pt/Al(2)O(3) during oxidation-reduction cycles monitored by high-energy resolution off-resonant X-ray spectroscopy.
- 2013
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 135:51, s. 19071-4
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Tidskriftsartikel (refereegranskat)abstract
- We report an in situ time-resolved high-energy resolution off-resonant spectroscopy study with subsecond resolution providing insight into the oxidation and reduction steps of a Pt catalyst during CO oxidation. The study shows that the slow oxidation step is composed of two characteristic stages, namely, dissociative adsorption of oxygen followed by partial oxidation of Pt subsurface. By comparing the experimental spectra with theoretical calculations, we found that the intermediate chemisorbed O on Pt is adsorbed on atop position, which suggests surface poisoning by CO or surface reconstruction.
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| 49. |
- Tyrala, Krzysztof, et al.
(författare)
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State-Population Narrowing Effect in Two-Photon Absorption for Intense Hard X-ray Pulses
- 2017
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Ingår i: Applied Sciences. - : MDPI AG. - 1454-5101 .- 2076-3417. ; 7:7
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Tidskriftsartikel (refereegranskat)abstract
- We report on studies of state-populations during the two-photon absorption process using intense X-ray pulses. The calculations were performed in a time-dependent manner using a simple three-level model expressed by coupled rate equations. We show that the proposed approach describes well the measured rates of X-rays excited in the one-photon and two-photon absorption processes, and allows detailed investigation of the state population dynamics during the course of the incident X-ray pulse. Finally, we demonstrate that the nonlinear interaction of X-ray pulses with atoms leads to a time-narrowing of state populations. This narrowing-effect is attributed to a quadratic incidence X-ray intensity dependence characteristic for nonlinear interactions of photons with matter.
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| 50. |
- Wach, Anna, et al.
(författare)
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Comparative study of the around-Fermi electronic structure of 5d metals and metal-oxides by means of high-resolution X-ray emission and absorption spectroscopies
- 2020
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Ingår i: Journal of Synchrotron Radiation. - : INT UNION CRYSTALLOGRAPHY. - 0909-0495 .- 1600-5775. ; 27, s. 689-694
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Tidskriftsartikel (refereegranskat)abstract
- The composition of occupied and unoccupied electronic states in the vicinity of Fermi energies is vital for all materials and relates to their physical, chemical and mechanical properties. This work demonstrates how the combination of resonant and non-resonant X-ray emission spectroscopies supplemented with theoretical modelling allows for quantitative analysis of electronic states in 5d transition metal and metal-oxide materials. Application of X-rays provides element selectivity that, in combination with the penetrating properties of hard X-rays, allows determination of the composition of electronic states under working conditions, i.e. non-vacuum environment. Tungsten metal and tungsten oxide are evaluated to show the capability to simultaneously assess composition of around-band-gap electronic states as well as the character and magnitude of the crystal field splitting.
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