| 1. |
- 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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| 2. |
- 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: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185 .- 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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| 3. |
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| 4. |
- 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
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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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| 5. |
- 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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| 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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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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| 9. |
- 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
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Ingår i: Journal of Physical Chemistry Letters. - : AMER CHEMICAL SOC. - 1948-7185 .- 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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| 10. |
- 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
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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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