| 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. |
- Alfakes, Boulos, et al.
(författare)
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Enhanced photoelectrochemical performance of atomic layer deposited Hf-doped ZnO
- 2020
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 385
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Tidskriftsartikel (refereegranskat)abstract
- Generation of hydrogen using photoelectrochemical (PEC) water splitting has attracted researchers for the last two decades. Several materials have been utilized as a photoanode in a water splitting cell, including ZnO due to its abundance, low production cost and suitable electronic structure. Most research attempts focused on doping ZnO to tailor its properties for a specific application. In this work, atomic layer deposition (ALD) was used to precisely dope ZnO with hafnium (Hf) in order to enhance its PEC performance. The resultant doped materials showed a significant improvement in PEC efficiency compared to pristine ZnO, which is linked directly to Hf introduction revealed by detailed optical, structural and electrical analyses. The photocurrent obtained in the best performing Hf-doped sample (0.75 wt% Hf) was roughly threefold higher compared to the undoped ZnO. Electrochemical impedance spectroscopy (EIS) and open-circuit potential-decay (OCPD) measurements confirmed suppression in photocarriers' surface recombination in the doped films, which led to a more efficient PEC water oxidation. The enhanced PEC performance of Hf-doped ZnO and effectiveness of the used metal dopant are credited to the synergistic optimization of chemical composition, which enhanced the electrical, structural including morphological, and optical properties of the final material, making Hf-doping an attractive candidate for novel PEC electrodes.
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| 3. |
- Antila, Liisa J., et al.
(författare)
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Hunting for the elusive shallow traps in TiO2 anatase
- 2015
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 51:54, s. 10914-10916
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Tidskriftsartikel (refereegranskat)abstract
- Understanding electron mobility on TiO2 is crucial because of its applications in photocatalysis and solar cells. This work shows that shallow traps believed to be involved in electron migration in TiO2 conduction band are formed upon band gap excitation, i.e., are not pre-existing states. The shallow traps in TiO2 results from large polarons and are not restricted to surface.
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| 4. |
- Banin, U., et al.
(författare)
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Nanotechnology for catalysis and solar energy conversion
- 2021
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Ingår i: Nanotechnology. - : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 32:4
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Tidskriftsartikel (refereegranskat)abstract
- This roadmap on Nanotechnology for Catalysis and Solar Energy Conversion focuses on the application of nanotechnology in addressing the current challenges of energy conversion: 'high efficiency, stability, safety, and the potential for low-cost/scalable manufacturing' to quote from the contributed article by Nathan Lewis. This roadmap focuses on solar-to-fuel conversion, solar water splitting, solar photovoltaics and bio-catalysis. It includes dye-sensitized solar cells (DSSCs), perovskite solar cells, and organic photovoltaics. Smart engineering of colloidal quantum materials and nanostructured electrodes will improve solar-to-fuel conversion efficiency, as described in the articles by Waiskopf and Banin and Meyer. Semiconductor nanoparticles will also improve solar energy conversion efficiency, as discussed by Boschloo et al in their article on DSSCs. Perovskite solar cells have advanced rapidly in recent years, including new ideas on 2D and 3D hybrid halide perovskites, as described by Spanopoulos et al 'Next generation' solar cells using multiple exciton generation (MEG) from hot carriers, described in the article by Nozik and Beard, could lead to remarkable improvement in photovoltaic efficiency by using quantization effects in semiconductor nanostructures (quantum dots, wires or wells). These challenges will not be met without simultaneous improvement in nanoscale characterization methods. Terahertz spectroscopy, discussed in the article by Milot et al is one example of a method that is overcoming the difficulties associated with nanoscale materials characterization by avoiding electrical contacts to nanoparticles, allowing characterization during device operation, and enabling characterization of a single nanoparticle. Besides experimental advances, computational science is also meeting the challenges of nanomaterials synthesis. The article by Kohlstedt and Schatz discusses the computational frameworks being used to predict structure-property relationships in materials and devices, including machine learning methods, with an emphasis on organic photovoltaics. The contribution by Megarity and Armstrong presents the 'electrochemical leaf' for improvements in electrochemistry and beyond. In addition, biohybrid approaches can take advantage of efficient and specific enzyme catalysts. These articles present the nanoscience and technology at the forefront of renewable energy development that will have significant benefits to society.
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| 5. |
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| 6. |
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| 7. |
- Bellardita, Marianna, et al.
(författare)
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Highly stable defective TiO2-x with tuned exposed facets induced by fluorine : Impact of surface and bulk properties on selective UV/visible alcohol photo-oxidation
- 2020
-
Ingår i: Applied Surface Science. - : ELSEVIER. - 0169-4332 .- 1873-5584. ; 510
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Tidskriftsartikel (refereegranskat)abstract
- Titanium dioxide samples were prepared in the presence of different amounts of fluorine via hydrothermal method. It has been found that the presence of fluoride influenced the physico-chemical properties of TiO2 in various ways as polymorphic form stability, surface hydroxylation, generation of hydroxyl radicals under irradiation and formation of Ti3+ centers and oxygen vacancies. The generation rate of (OH)-O-center dot radicals was investigated by the photoluminescence technique in the presence of terephthalic acid. X-ray diffractometry indicated that fluorine stabilized the anatase TiO2. X-Ray photoelectron spectroscopy (XPS) revealed the presence of fluorine on the surface and the shift of the valence band edge towards less negative potentials, electron paramagnetic resonance (EPR) confirmed the formation of Ti3+ in the bulk of the photocatalysts, UV-vis spectra showed the extension of the TiO2 photo-response in the visible light region. 2-Propanol degradation and 4-methoxybenzyl alcohol partial oxidation were studied as probe reactions by using the home prepared powders as photocatalysts. Surprisingly, the photocatalytic activity resulted to be mainly affected by (OH)-O-center dot radicals formation ability under irradiation, rather than by the presence of {0 0 1} facets, although it cannot be excluded that the latter could influence the ability to form radicals under irradiation.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- Bericat Vadell, Robert, et al.
(författare)
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Single-electron transfer reactions on surface-modified gold plasmons
- 2023
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Ingår i: Materials Today Chemistry. - : Elsevier. - 2468-5194. ; 34
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Tidskriftsartikel (refereegranskat)abstract
- Photoredox catalysis's relevance in organic synthesis research and innovation will increase in the coming decades. However, the processes rely almost exclusively on expensive noble metal complexes, most notably iridium complexes, to absorb light and transfer a single charge to a substrate or a catalyst to initiate cascade transformations. Light-triggered plasmon resonances generate a non-Fermi-Dirac energy distribution with many hot carriers that decay in similar to 1 ps. Their ultrafast relaxation makes performing single electron transfer (SET) transformations challenging. Herein, a novel photosystem is proposed based on surface-modified gold nanoparticles (aka plasmon "molecularization"), which improved charge separation and, more importantly, enabled SET reactions, expanding the portfolio of photocatalysts available for photoredox catalysis. The photosystem was made into an electrode, permitting its use in photoelectrochemical arrangements that leverage electro- and photo-chemical approaches' benefits and chemical engineering solutions, helping the synthetic chemistry efforts towards greener synthesis and synthesis of more complex structures on a scale.
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| 11. |
- Bhunia, Asamanjoy, et al.
(författare)
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Formal water oxidation turnover frequencies from MIL-101(Cr) anchored Ru(bda) depend on oxidant concentration
- 2018
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Ingår i: Chemical Communications. - : ROYAL SOC CHEMISTRY. - 1359-7345 .- 1364-548X. ; 54, s. 7770-7773
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Tidskriftsartikel (refereegranskat)abstract
- The molecular water oxidation catalyst [Ru(bda)(L)(2)] has been incorporated into pyridine-decorated MIL-101(Cr) metal-organic frameworks. The resulting MIL-101@Ru materials exhibit turnover frequencies (TOFs) up to ten times higher compared to the homogenous reference. An unusual dependence of the formal TOFs on oxidant concentration is observed that ultimately arises from differing amounts of catalysts in the MOF crystals being active.
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| 12. |
- 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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| 13. |
- 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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| 14. |
- 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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| 15. |
- 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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| 16. |
- Blachucki, W., et al.
(författare)
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Inception of electronic damage of matter by photon-driven post-ionization mechanisms
- 2019
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Ingår i: Structural Dynamics. - : AIP Publishing. - 2329-7778. ; 6:2
-
Tidskriftsartikel (refereegranskat)abstract
- "Probe-before-destroy" methodology permitted diffraction and imaging measurements of intact specimens using ultrabright but highly destructive X-ray free-electron laser (XFEL) pulses. The methodology takes advantage of XFEL pulses ultrashort duration to outrun the destructive nature of the X-rays. Atomic movement, generally on the order of >50 fs, regulates the maximum pulse duration for intact specimen measurements. In this contribution, we report the electronic structure damage of a molecule with ultrashort X-ray pulses under preservation of the atoms' positions. A detailed investigation of the X-ray induced processes revealed that X-ray absorption events in the solvent produce a significant number of solvated electrons within attosecond and femtosecond timescales that are capable of coulombic interactions with the probed molecules. The presented findings show a strong influence on the experimental spectra coming from ionization of the probed atoms' surroundings leading to electronic structure modification much faster than direct absorption of photons. This work calls for consideration of this phenomenon in cases focused on samples embedded in, e.g., solutions or in matrices, which in fact concerns most of the experimental studies.
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| 17. |
- 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
-
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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| 18. |
- 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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| 19. |
- Bonarowska, Magdalena, et al.
(författare)
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Application of silica-supported Ir and Ir-M (M=Pt, Pd, Au) catalysts for low-temperature hydrodechlorination of tetrachloromethane
- 2018
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Ingår i: Science of the Total Environment. - : ELSEVIER SCIENCE BV. - 0048-9697 .- 1879-1026. ; 644, s. 287-297
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Tidskriftsartikel (refereegranskat)abstract
- Herein, it is presented a catalytic system for gas-phase hydrodechlorination of tetrachloromethane at low temperature and atmospheric pressure, using iridium supported on silica as parent catalyst. Iridium electronic configuration is suitable to catalyse the hydrodechlorination reactions, however, it has been rarely used in this reaction to date. The catalytic abilities were significantly improved when a second transition metal was added. Catalysts' stability and selectivity to the desired products (i.e. C-1-C-4 hydrocarbons) improved compared to conventional activation in hydrogen when catalysts were activated shortly with microwave irradiation. Microwave irradiation of catalysts favourably influences the homogeneity of the metallic active phase, both in terms of the size of metal crystals and the homogeneity of bimetallic systems. Addition of platinumto the 'parent' iridium catalyst improved its catalytic properties and decreased deactivation. Fresh and spent catalysts were comprehensively characterized using several techniques (BET, CO-chemisorption, XRD, XPS, electron microscopy and mass spectrometry) to determine structure-activity relationships and potential causes for catalyst deactivation. No significant changes in crystalline size or bimetallic phase composition were observed for spent catalysts (with the exception of Ir-Pd catalysts which underwent bulk carbide during the reaction).
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| 20. |
- Bonarowska, Magdalena, et al.
(författare)
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Influence of microwave activation on the catalytic behavior of Pd-Au/C catalysts employed in the hydrodechlorination of tetrachloromethane
- 2018
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Ingår i: Reaction Kinetics, Mechanisms and Catalysis. - : Springer Science and Business Media LLC. - 1878-5190 .- 1878-5204. ; 124:1, s. 375-388
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Tidskriftsartikel (refereegranskat)abstract
- This work investigates the influence of activation by microwave irradiation on the catalytic properties of Pd-Au/C-Sibunit catalysts in the hydrodechlorination of CCl4. Pd and Pd-Au samples were thoroughly characterized by CO chemisorption, X-ray diffraction, TPHD and STEM, and used in gas phase hydrodechlorination of tetrachloromethane. The studies showed that homogenous Pd-Au alloys are formed more efficiently if short-time microwave activation is applied instead of conventional activation by H-2 reduction at 380 A degrees C. These catalysts show higher activity, stability and higher selectivity towards the desired products (C1-C5 hydrocarbons) than the catalysts activated by conventional reduction in 10%H-2/Ar flow.
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| 21. |
- Cairns, Marie-Louise, et al.
(författare)
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The potential of electron beam radiation for simultaneous surface modification and bioresorption control of PLLA.
- 2012
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 100:9, s. 2223-9
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Tidskriftsartikel (refereegranskat)abstract
- Bioresorbable polymers have been widely investigated as materials exhibiting significant potential for successful application in the fields of tissue engineering and drug delivery. Further to the ability to control degradation, surface engineering of polymers has been highlighted as a key method central to their development. Previous work has demonstrated the ability of electron beam (e-beam) technology to control the degradation profiles and bioresorption of a number of commercially relevant bioresorbable polymers (poly-l-lactic acid (PLLA), L-lactide/DL-lactide co-polymer (PLDL) and poly(lactic-co-glycolic acid (PLGA)). This work investigates the further potential of e-beam technology to impart added biofunctionality through the manipulation of polymer (PLLA) surface properties. PLLA samples were subjected to e-beam treatments in air, with varying beam energies and doses. Surface characterization was then performed using contact angle analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy. Results demonstrated a significant increase in surface wettability post e-beam treatment. In correlation with this, XPS data showed the introduction of oxygen-containing functional groups to the surface of PLLA. Raman spectroscopy indicated chain scission in the near surface region of PLLA (as predicted). However, e-beam effects on surface properties were not shown to be dependent on beam energy or dose. E-beam irradiation did not seem to affect the surface roughness of PLLA as a direct consequence of the treatment.
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| 22. |
- Campbell, Paul S., et al.
(författare)
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Olefin hydrogenation by ruthenium nanoparticles in ionic liquid media : Does size matter?
- 2010
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Ingår i: Journal of Catalysis. - : Elsevier. - 0021-9517 .- 1090-2694. ; 275:1, s. 99-107
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Tidskriftsartikel (refereegranskat)abstract
- Tailor-made and size-controlled ruthenium nanoparticles, RuNPs, of three distinct sizes between 1 and 3 nm are generated from the decomposition of (η4-1,5-cyclooctadiene)(η6-1,3,5-cyclooctatriene)ruthenium(0) [Ru(COD)(COT)], under H2 in 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl)imide, C1C4ImNTf2, by simply varying experimental conditions. Catalytic hydrogenation of 1,3-cyclohexadiene, CYD, and cyclohexene, CYE, in C1C4ImNTf2, has been used as a probe for the relationship between size and catalytic performance (activity and selectivity) of RuNPs. To allow comparison between different reactions, all catalytic reaction mixtures were diligently prepared in order that the parameters such as substrate/catalyst and substrate/ionic liquid ratio, and therefore, viscosity and mass transport factors remained constant. It was found that the catalytic activity increases with the NP size, while high selectivity is only observed with the smaller NPs. In addition, the studied RuNPs exhibit a high level of recyclability with neither loss of activity nor significant agglomeration.
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| 23. |
- Cieslak, Anna M., et al.
(författare)
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Ultra long-lived electron-hole separation within water-soluble colloidal ZnO nanocrystals : Prospective Applications For Solar Energy Production
- 2016
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Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855. ; 30, s. 187-192
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Tidskriftsartikel (refereegranskat)abstract
- Zinc oxide was one of the first semiconductors used in dye-sensitized solar cells but its instability in aqueous media precludes its use for large-scale applications. Herein, we report on a novel ZnO nanocrystal material derived by an organometallic approach that is simultaneously stable and soluble in water due to its carboxylate oligoethylene glycol shell strongly anchored to the inorganic core by the head groups. The resulting unique inorganic core-organic shell interface also stabilizes the photo-generated hole, leading to a dramatic slowing down of charge recombination, which otherwise is a major hurdle in using nanostructured ZnO.
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| 24. |
- Clarizia, Laura, et al.
(författare)
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Effect of Synthesis Method on Reaction Mechanism for Hydrogen Evolution over CuxOy/TiO2 Photocatalysts : A Kinetic Analysis
- 2023
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Ingår i: International Journal of Molecular Sciences. - : MDPI. - 1661-6596 .- 1422-0067. ; 24:3
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Tidskriftsartikel (refereegranskat)abstract
- The existing literature survey reports rare and conflicting studies on the effect of the preparation method of metal-based semiconductor photocatalysts on structural/morphological features, electronic properties, and kinetics regulating the photocatalytic H-2 generation reaction. In this investigation, we compare the different copper/titania-based photocatalysts for H-2 generation synthesized via distinct methods (i.e., photodeposition and impregnation). Our study aims to establish a stringent correlation between physicochemical/electronic properties and photocatalytic performances for H-2 generation based on material characterization and kinetic modeling of the experimental outcomes. Estimating unknown kinetic parameters, such as charge recombination rate and quantum yield, suggests a mechanism regulating charge carrier lifetime depending on copper distribution on the TiO2 surface. We demonstrate that H-2 generation photoefficiency recorded over impregnated CuxOy/TiO2 is related to an even distribution of Cu(0)/Cu(I) on TiO2, and the formation of an Ohmic junction concertedly extended charge carrier lifetime and separation. The outcomes of the kinetic analysis and the related modeling investigation underpin photocatalyst physicochemical and electronic properties. Overall, the present study lays the groundwork for the future design of metal-based semiconductor photocatalysts with high photoefficiencies for H-2 evolution.
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| 25. |
- 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: 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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| 26. |
- 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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| 27. |
- Czapla-Masztafiak, Joanna, et al.
(författare)
-
Mechanism of hydrolysis of a platinum(IV) complex discovered by atomic telemetry
- 2018
-
Ingår i: Journal of Inorganic Biochemistry. - : ELSEVIER SCIENCE INC. - 0162-0134 .- 1873-3344. ; 187, s. 56-61
-
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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| 28. |
- Dey, Ananta, et al.
(författare)
-
Exploiting hot electrons from a plasmon nanohybrid system for the photoelectroreduction of CO2
- 2024
-
Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- Plasmonic materials convert light into hot carriers and heat to mediate catalytic transformation. The participation of hot carriers (photocatalysis) remains a subject of vigorous debate, often argued on the basis that carriers have ultrashort lifetime incompatible with drive photochemical processes. This study utilises plasmon hot electrons directly in the photoelectrocatalytic reduction of CO2 to CO via a Ppasmonic nanohybrid. Through the deliberate construction of a plasmonic nanohybrid system comprising NiO/Au/ReI(phen-NH2)(CO)3Cl (phen-NH2 = 1,10-Phenanthrolin-5-amine) that is unstable above 580 K; it was possible to demonstrate hot electrons are the main culprit in CO2 reduction. The engagement of hot electrons in the catalytic process is derived from many approaches that cover the processes in real-time, from ultrafast charge generation and separation to catalysis occurring on the minute scale. Unbiased in situ FTIR spectroscopy confirmed the stepwise reduction of the catalytic system. This, coupled with the low thermal stability of the ReI(phen-NH2)(CO)3Cl complex, explicitly establishes plasmonic hot carriers as the primary contributors to the process. Therefore, mediating catalytic reactions by plasmon hot carriers is feasible and holds promise for further exploration. Plasmonic nanohybrid systems can leverage plasmon’s unique photophysics and capabilities because they expedite the carrier’s lifetime.
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| 29. |
- Dey, Ananta, et al.
(författare)
-
Hydrogen evolution with hot electrons on a plasmonic-molecular catalyst hybrid system
- 2024
-
Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 15
-
Tidskriftsartikel (refereegranskat)abstract
- Plasmonic systems convert light into electrical charges and heat, mediating catalytic transformations. However, there is ongoing controversy regarding the involvement of hot carriers in the catalytic process. In this study, we demonstrate the direct utilisation of plasmon hot electrons in the hydrogen evolution reaction with visible light. We intentionally assemble a plasmonic nanohybrid system comprising NiO/Au/[Co(1,10-Phenanthrolin-5-amine)2(H2O)2], which is unstable at water thermolysis temperatures. This assembly limits the plasmon thermal contribution while ensuring that hot carriers are the primary contributors to the catalytic process. By combining photoelectrocatalysis with advanced in situ spectroscopies, we can substantiate a reaction mechanism in which plasmon-induced hot electrons play a crucial role. These plasmonic hot electrons are directed into phenanthroline ligands, facilitating the rapid, concerted proton-electron transfer steps essential for hydrogen generation. The catalytic response to light modulation aligns with the distinctive profile of a hot carrier-mediated process, featuring a positive, though non-essential, heat contribution. Direct participation of plasmon-induced hot electrons in the photoelectrocatalytic synthesis of hydrogen. This report solves a long-lasting contentious issue surrounding plasmonic materials on catalytic applications.
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| 30. |
- Fernandes, Arthur B., et al.
(författare)
-
Recoverable and Reusable Polymer Microbead-Supported Metal Nanocatalysts for Redox Chemical Transformations
- 2020
-
Ingår i: ACS APPLIED NANO MATERIALS. - : AMER CHEMICAL SOC. - 2574-0970. ; 3:2, s. 1722-1730
-
Tidskriftsartikel (refereegranskat)abstract
- Metal nanoparticles have been widely exploited in catalysis, but their full impact on the environment and human health is still under debate. Here we describe the one-step fabrication of recoverable and reusable polymer microbead-supported metal and metal oxide nanocatalysts for application in batch reactions and flow systems. Au, Ag, and Fe3O4 nanoparticles were prepared directly at the surface of commercial benzylamine-coated spherical polymer beads in water by using low-energy microwave radiation for 5 min. The functionalization of microbead surface with betalamic acid, an antioxidant from plant origin, before irradiation changes the morphology and catalytic properties of the grafted nanoparticles. No leaching of the active phase was observed during the application of these effective and ready-to-use nanocatalysts on the reduction of 4-nitrophenol and oxidation of dihydrorhodamine 123. The supported nanocatalysts were recovered by filtration and/or magnetic separation and reused up to three times without significant drop in catalytic performance. These results can stimulate the controlled and facile synthesis of recoverable microbead-supported magnetic and nonmagnetic nanocatalysts that can be applied under myriad reaction conditions and reused multiple times.
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| 31. |
- Fernandes, Daniel L. A., et al.
(författare)
-
A 3D printed microliquid jet with an adjustable nozzle diameter
- 2015
-
Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 140:18, s. 6234-6238
-
Tidskriftsartikel (refereegranskat)abstract
- Microliquid jets have many applications, in particular in the fields of spectroscopy/analysis of samples susceptible to beam damage. Herein, we report a microliquid jet, manufactured with 3D printing technology, with a tuneable nozzle diameter output. This strategy increases the breadth of techniques that can be covered with a single microliquid jet.
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| 32. |
- Fernandes, Daniel L. A., et al.
(författare)
-
Green microfluidic synthesis of monodisperse silver nanoparticles via genetic algorithm optimization
- 2016
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:98, s. 95693-95697
-
Tidskriftsartikel (refereegranskat)abstract
- A scalable and green procedure for the microfluidic flow synthesis of monodisperse silver nanoparticles is reported. Beetroot extract is used both as a reducing and growth-regulating agent. A multi-objective genetic algorithm was used to automate the optimization of the reaction and reduce sample polydispersity observed in previous reports. The proposed methodology ensures high-quality nanoparticles in a rapidly manner and devoid of human skill or intuition, essential for method standardization and implementation.
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| 33. |
- Fernandes, Daniel L. A., et al.
(författare)
-
Novel photo-reactor for fast screening of photo-catalytic systems
- 2017
-
Ingår i: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 335, s. 36-39
-
Tidskriftsartikel (refereegranskat)abstract
- Photo-catalysis is an emerging technology for clean energy production, organic synthesis and environmental protection, etc. While there is a hydrogen of systems and schemes to attain these objectives, there is a paucity of photo-reactors capable of determine catalytic abilities in real time with reduce amounts of samples, i.e., fast-screening of catalyst and reaction parameters. Herein, we report a novel photo-reactor for simultaneous online monitoring of gaseous products with quadrupole mass spectrometry and photo-physics with fibre optic UV/Vis with millisecond time resolution on 4 mL cuvettes.
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| 34. |
- Friedli, Peter, et al.
(författare)
-
Dye-injected electron trapping in TiO2 determined by broadband transient infrared spectroscopy.
- 2014
-
Ingår i: Photochemical and Photobiological Sciences. - : Springer. - 1474-905X .- 1474-9092. ; 13:10, s. 1393-6
-
Tidskriftsartikel (refereegranskat)abstract
- We report the dynamics of electrons injected into TiO2 due to the excitation of Ru-N719 dye at 532 nm. The synchrotron based broadband transient mid-IR spectroscopy revealed that the injected electrons are quickly confined to a trap state with an average energy of ca. 240 meV below the conduction band. The average energy of the trapping states did not change with the increase of the delay time, suggesting a singular electronic identity of the trap states.
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| 35. |
- Ganguli, Sagar, et al.
(författare)
-
Nano-Impact Single-Entity Electrochemistry Enables Plasmon-Enhanced Electrocatalysis
- 2023
-
Ingår i: Angewandte Chemie International Edition. - : Wiley-VCH Verlagsgesellschaft. - 1433-7851 .- 1521-3773. ; 62:25
-
Tidskriftsartikel (refereegranskat)abstract
- Plasmon-enhanced electrocatalysis (PEEC), based on a combination of localized surface plasmon resonance excitation and an electrochemical bias applied to a plasmonic material, can result in improved electrical-to-chemical energy conversion compared to conventional electrocatalysis. Here, we demonstrate the advantages of nano-impact single-entity electrochemistry (SEE) for investigating the intrinsic activity of plasmonic catalysts at the single-particle level using glucose electrooxidation and oxygen reduction on gold nanoparticles as model reactions. We show that in conventional ensemble measurements, plasmonic effects have minimal impact on photocurrents. We suggest that this is due to the continuous equilibration of the Fermi level (EF) of the deposited gold nanoparticles with the EF of the working electrode, leading to fast neutralization of hot carriers by the measuring circuit. The photocurrents detected in the ensemble measurements are primarily caused by photo-induced heating of the supporting electrode material. In SEE, the EF of suspended gold nanoparticles is unaffected by the working electrode potential. As a result, plasmonic effects are the dominant source of photocurrents under SEE experimental conditions.
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| 36. |
- Garlisi, Corrado, et al.
(författare)
-
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
-
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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| 37. |
- Garlisi, Corrado, et al.
(författare)
-
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
-
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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| 38. |
- Geng, Xinjian, et al.
(författare)
-
Can photoluminescence quenching be a predictor for perovskite solar cell efficiencies?
- 2023
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 25:34, s. 22607-22613
-
Tidskriftsartikel (refereegranskat)abstract
- Bromide-based perovskites have large bandgaps, making them attractive for tandem solar cells developed to overcome the Shockley–Queisser limit. A perovskite solar cell architecture employs transporting layers to improve charge extraction and transport. Due to the wide variety of materials and preparation methods, it is critical to devise fast screening methods to rank transporting layers. Herein, we evaluate perovskite fluorescence quenching followed by time- and energy-resolved photoluminescence (TER-PL) and analyse the intensity dependence as a potential method to qualify charge-transporting layers rapidly. The capability of the technique was evaluated with TiO2/FAPbBr3 and SnO2/FAPbBr3, the most commonly used electron transporting layers, which were prepared using standard protocols to make best-performing devices. The results revealed that TiO2 is the most effective quencher due to the higher density of states in the conduction band, consistent with Marcus-Gerischer's theory. However, record-performance devices use SnO2 as the electron transport layer. This shows that the relationship between photoluminescence quenching and device performance is not bidirectional. Therefore, additional measurements like conductivity are also needed to provide reliable feedback for device performance.
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| 39. |
- Geng, Xinjian, et al.
(författare)
-
Direct Plasmonic Solar Cell Efficiency Dependence on Spiro-OMeTAD Li-TFSI Content
- 2021
-
Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 11:12
-
Tidskriftsartikel (refereegranskat)abstract
- The proliferation of the internet of things (IoT) and other low-power devices demands the development of energy harvesting solutions to alleviate IoT hardware dependence on single-use batteries, making their deployment more sustainable. The propagation of energy harvesting solutions is strongly associated with technical performance, cost and aesthetics, with the latter often being the driver of adoption. The general abundance of light in the vicinity of IoT devices under their main operation window enables the use of indoor and outdoor photovoltaics as energy harvesters. From those, highly transparent solar cells allow an increased possibility to place a sustainable power source close to the sensors without significant visual appearance. Herein, we report the effect of hole transport layer Li-TFSI dopant content on semi-transparent, direct plasmonic solar cells (DPSC) with a transparency of more than 80% in the 450-800 nm region. The findings revealed that the amount of oxidized spiro-OMeTAD (spiro(+)TFSI(-)) significantly modulates the transparency, effective conductance and conditions of device performance, with an optimal performance reached at around 33% relative concentration of Li-TFSI concerning spiro-OMeTAD. The Li-TFSI content did not affect the immediate charge extraction, as revealed by an analysis of electron-phonon lifetime. Hot electrons and holes were injected into the respective layers within 150 fs, suggesting simultaneous injection, as supported by the absence of hysteresis in the I-V curves. The spiro-OMeTAD layer reduces the Au nanoparticles' reflection/backscattering, which improves the overall cell transparency. The results show that the system can be made highly transparent by precise tuning of the doping level of the spiro-OMeTAD layer with retained plasmonics, large optical cross-sections and the ultrathin nature of the devices.
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| 40. |
- Geng, Xinjian, 1992-
(författare)
-
Interfacial Analysis and Charge Transfer in Solar Cells
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Harnessing sunlight through solar cells is vital for sustainable energy production. The conventional architecture of a solar cell consists of multilayers of materials, each serving a particular function. The absorbing layer converts the solar energy into valuable electricity by the photovoltaic effect. Positioned on either side of the absorbing layer are charge transport layers, which collect the generated electricity. Charge transfer and recombination occur at interfaces, affecting the solar cells' open-circuit voltage (Voc). This doctoral thesis focuses on the analysis of the perovskite/n-type semiconductor interface and plasmonic/p-type semiconductor interface, provides an understanding of the charge generation and transfer in solar cells, and helps to establish a selection of the ideal charge transport layer for efficient charge extraction.Initially, photogenerated charge carriers were investigated by time- and energy-resolved photoluminescence (TER-PL) from the thin formamidinium lead-bromide (FAPbBr3) perovskite absorber film. Both exciton and free charge dynamics under various excitation power intensities were taken into consideration. Following studies on the charge transfer at interfaces were performed by incorporating n-type semiconductors (TiO2 and SnO2) as the charge transport layer. The results revealed that the TiO2 is more efficient as a fluorescence quencher due to the higher density of states in its conduction band. While conductivity measurements suggested that SnO2 was better for avoiding the accumulation of charges. Thus, solely charge extraction efficiency is not sufficient for determining the solar cell performance.To alleviate the energy losses in solar cells, extraction of hot electrons would be a viable way. Then, hot carriers generated through plasmon excitation in metal nanoparticles, which is different from semiconductors, were collected in the solid-state direct plasmonic solar cell (DPSC). Also, plasmonics show high absorption across the visible–infrared spectrum. Early progress mainly focused on hot electron transfer. The second part of the thesis investigated the effect of Li-TFSI dopant concentration in the hole transport layer (spiro-OMeTAD) on solar cell performance. 33% oxidised species (spiro+TFSI-) gave the optimal efficiency. By using transient absorption spectroscopy, the injection of hot electrons and holes was verified in a complete solar cell device as well.
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| 41. |
- Geng, Xinjian, et al.
(författare)
-
Transient Energy-Resolved Photoluminescence Study of Excitons and Free Carriers on FAPbBr3 and FAPbBr3/SnO2 Interfaces
- 2023
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 127:6, s. 3085-3092
-
Tidskriftsartikel (refereegranskat)abstract
- Lead bromide perovskites have a larger band gap and are significantly more stable than their iodine counterparts, offering the perspective for higher voltage, tandem photovoltaics exceeding the Shockley-Queisser limit, and shorter time to deployment of photovoltaics. However, their efficiencies still need to be rivaling the iodine ones. Herein, the photophysics of FAPbBr(3) and the ones behind electron transfer from FAPbBr(3) to SnO2, one of the most effective electron transporting materials (ETMs), are reported. Time- and energy-resolved photoluminescence studies revealed the existence of two emitting states in the perovskite, which were assigned to bounded excitons and free carriers. SnO2 extracted electrons from excitons and free carriers, with a selectivity related to the SnO2 surface treatment. This new insight helps explain SnO2's unique qualities as an ETM to produce photovoltaics with reduced voltage losses. Furthermore, this study illustrates the importance of performing time- and energy-resolved photoluminescence to capture the intricacies of the photophysical process.
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| 42. |
- Gizinski, Damian, et al.
(författare)
-
Chemoselective flow hydrogenation of alpha,beta - Unsaturated aldehyde with nano-nickel
- 2017
-
Ingår i: Catalysis communications. - : ELSEVIER SCIENCE BV. - 1566-7367 .- 1873-3905. ; 98, s. 17-21
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, it is presented a novel catalytic system for the continuous flow chemoselective hydrogenation of a,alpha,beta- unsaturated aldehydes used in the production of high value cosmetics and pharmaceuticals precursors. The reaction was catalyzed by nano nickel particles grafted on polymeric support, synthesized via a simple, adaptable and green methodology. The system was highly active and very selective to C=C bond saturation.
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| 43. |
- Gizinski, Damian, et al.
(författare)
-
Hydrogenation by Copper Catalysts
- 2016
-
Ingår i: Hydrogenation With Low-Cost Transition Metals. - : CRC PRESS-TAYLOR & FRANCIS GROUP. ; , s. 79-117
-
Bokkapitel (refereegranskat)abstract
- This chapter deals with hydrogenation mediated by copper metal present as supported and unsupported nanoparticles. In the chapter, we highlight synthetic procedures for the preparation of metallic copper nanoparticles and their applications in catalysis. The main target is reactions carried out for fine and pharmaceutical chemicals' production.
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| 44. |
- Gizinski, Damian, et al.
(författare)
-
On-the-fly Catalyst Accretion and Screening in Chemoselective Flow Hydrogenation
- 2018
-
Ingår i: ChemCatChem. - : WILEY-V C H VERLAG GMBH. - 1867-3880 .- 1867-3899. ; 10:17, s. 3641-3646
-
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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| 45. |
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| 46. |
- Goguet, Alexandre, et al.
(författare)
-
Increased dispersion of supported gold during methanol carbonylation conditions.
- 2009
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 131:20, s. 6973-5
-
Tidskriftsartikel (refereegranskat)abstract
- The active site in supported gold catalysts for the carbonylation of methanol has been identified as dimers/trimers of gold which are formed from large gold particles >10 nm in diameter. Methyl iodide was found to be critical for this dispersion process and to maintain the catalyst in the active form. This study also shows that it may be possible to redisperse gold catalysts, in general, after reaction.
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| 47. |
- Goguet, Alexandre, et al.
(författare)
-
Remarkable stability of ionic gold supported on sulfated lanthanum oxide.
- 2009
-
Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; :32, s. 4889-91
-
Tidskriftsartikel (refereegranskat)abstract
- Isolated cationic gold deposited on sulfated lanthanum oxide has been shown to exhibit remarkable stability opening a promising way of stabilising ionic gold for catalytic reactions.
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| 48. |
- Goncalves, Leticia C. P., et al.
(författare)
-
Boosting photobioredox catalysis by morpholine electron donors under aerobic conditions
- 2019
-
Ingår i: Catalysis Science & Technology. - : Royal Society of Chemistry. - 2044-4753 .- 2044-4761. ; 9:10, s. 2682-2688
-
Tidskriftsartikel (refereegranskat)abstract
- Light-driven reduction of flavins, e.g. FAD or FMN, by sacrificial electron donors emerged as a convenient method to promote biocatalytic transformations. However, flavin activation has been restricted to oxygen-free conditions to prevent enzyme deactivation caused by reactive oxygen species (ROS). Herein, we show that the photoreduction of FMN by morpholines, including 3-(N-morpholino)propanesulfonic acid (MOPS), lessens the deactivation of the enoate reductase XenB from Pseudomonas sp. during the stereoselective asymmetric enzymatic reduction of a model ,-unsaturated diketone under aerobic conditions, leading to a 91% GC-yield and a stereoselectivity greater than 94%. The kinetic stability of the thermolabile XenB was increased by more than 20-fold in MOPS buffer compared to that in Tris-HCl buffer, and a pronounced positive effect on the transition midpoint temperature was observed. The reactive form of the FMN photocatalyst is stabilized by the formation of a (3)[FMN--MOPS+] ensemble, which reduces the formation of hydrogen peroxide and other ROS in the presence of oxygen. These results contribute to broaden the application of photobiocatalytic transformations using flavin-dependent reductases.
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| 49. |
- Goncalves, Leticia C. P., et al.
(författare)
-
Morpholine-based buffers activate aerobic photobiocatalysis via spin correlated ion pair formation
- 2019
-
Ingår i: Catalysis Science & Technology. - : ROYAL SOC CHEMISTRY. - 2044-4753 .- 2044-4761. ; 9:6, s. 1365-1371
-
Tidskriftsartikel (refereegranskat)abstract
- The use of enzymes for synthetic applications is a powerful and environmentally-benign approach to increase molecular complexity. Oxidoreductases selectively introduce oxygen and hydrogen atoms into myriad substrates, catalyzing the synthesis of chemical and pharmaceutical building blocks for chemical production. However, broader application of this class of enzymes is limited by the requirements of expensive cofactors and low operational stability. Herein, we show that morpholine-based buffers, especially 3-(N-morpholino)propanesulfonic acid (MOPS), promote photoinduced flavoenzyme-catalyzed asymmetric redox transformations by regenerating the flavin cofactor via sacrificial electron donation and by increasing the operational stability of flavin-dependent oxidoreductases. The stabilization of the active forms of flavin by MOPS via formation of the spin correlated ion pair (3)[flavin(-)-MOPS+] ensemble reduces the formation of hydrogen peroxide, circumventing the oxygen dilemma under aerobic conditions detrimental to fragile enzymes.
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| 50. |
- Goszewska, Ilona, et al.
(författare)
-
A novel nano-palladium catalyst for continuous-flow chemoselective hydrogenation reactions
- 2017
-
Ingår i: Catalysis communications. - : Elsevier BV. - 1566-7367 .- 1873-3905. ; 94, s. 65-68
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, we report a catalyst composed of palladium nanoparticles immobilized on polymeric resin for chemoselective hydrogenation reactions under flow conditions. The catalyst exhibits high activity and selectivity towards hydrogenation of C=C double bond, as confirmed in the hydrogenation of 2-heptene and 6-methyl-5-hepten-2-one.
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