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Publications (10 of 137) Show all publications
Mikkelä, M.-H., Marnauza, M., Hetherington, C. J., Wallenberg, R., Mårsell, E., Liu, Y.-P., . . . Tchaplyguine, M. (2024). Bismuth-oxide nanoparticles: study in a beam and as deposited. Physical Chemistry, Chemical Physics - PCCP, 26(13), 10369-10381
Open this publication in new window or tab >>Bismuth-oxide nanoparticles: study in a beam and as deposited
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2024 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 26, no 13, p. 10369-10381Article in journal (Refereed) Published
Abstract [en]

Bi2O3 is a promising material for solid-oxide fuel cells (SOFC) due to the high ionic conductivity of some phases. The largest value is reached for its δ-phase, but it is normally stable at temperatures too high for SOFC operation, while nanostructured oxide is believed to have more suitable stabilization temperature. However, to manufacture such a material with a controlled chemical composition is a challenging task. In this work, we investigated the fabrication of nanostructured Bi2O3 films formed by deposition of free Bi-oxide nanoparticles created in situ. The particle-production method was based on reactive sputtering and vapour aggregation. Depending on the fabrication conditions, the nanoparticles contained either a combination of Bi–metal and Bi-oxide, or only Bi-oxide. Prior to deposition, the free particles were probed in the beam – by synchrotron-based photoelectron spectroscopy (PES), which allowed assessing their composition "on the-fly". The nanoparticle films obtained after deposition were studied by PES, scanning electron microscopy, transmission electron microscopy, and electron diffraction. The films' chemical composition, grain dimensions, and crystal structure were probed. Our analysis suggests that our method produced Bi-oxide films in more than one polymorph of Bi2O3.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2024
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-530040 (URN)10.1039/d4cp00376d (DOI)001186875800001 ()38502136 (PubMedID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationEU, FP7, Seventh Framework Programme, 226716Carl Tryggers foundation Lund University
Available from: 2024-06-03 Created: 2024-06-03 Last updated: 2024-06-03Bibliographically approved
Mosaferi, M., Ceolin, D., Rueff, J.-P., Selles, P., Odelius, M., Björneholm, O., . . . Carniato, S. (2024). Fingerprint of Dipole Moment Orientation of Water Molecules in Cu2+ Aqueous Solution Probed by X-ray Photoelectron Spectroscopy. Journal of the American Chemical Society, 146(14), 9836-9850
Open this publication in new window or tab >>Fingerprint of Dipole Moment Orientation of Water Molecules in Cu2+ Aqueous Solution Probed by X-ray Photoelectron Spectroscopy
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2024 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 146, no 14, p. 9836-9850Article in journal (Refereed) Published
Abstract [en]

The electronic structure and geometrical organization of aqueous Cu2+ have been investigated by using X-ray photoelectron spectroscopy (XPS) at the Cu L-edge combined with state-of-the-art ab initio molecular dynamics and a quantum molecular approach designed to simulate the Cu 2p X-ray photoelectron spectrum. The calculations offer a comprehensive insight into the origin of the main peak and satellite features. It is illustrated how the energy drop of the Cu 3d levels (≈7 eV) following the creation of the Cu 2p core hole switches the nature of the highest singly occupied molecular orbitals (MOs) from the dominant metal to the dominant MO nature of water. It is particularly revealed how the repositioning of the Cu 3d levels induces the formation of new bonding (B) and antibonding (AB) orbitals, from which shakeup mechanisms toward the relaxed H-SOMO operate. As highlighted in this study, the appearance of the shoulder near the main peak corresponds to the characteristic signature of shakeup intraligand (1a1 → H-SOMO(1b1)) excitations in water, providing insights into the average dipole moment distribution (≈36°) of the first-shell water molecules surrounding the metal ion and its direct impact on the broadening of the satellite. It is also revealed that the main satellite at 8 eV from the main peak corresponds to (metal/1b2 → H-SOMO(1b1) of water) excitations due to a bonding/antibonding (B/AB) interaction of Cu 3d levels with the deepest valence O2p/H1s 1b2 orbitals of water. This finding underscores the sensitivity of XPS to the electronic structure and orientation of the nearest water molecules around the central ion.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2024
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-530041 (URN)10.1021/jacs.3c14570 (DOI)001193912900001 ()38545903 (PubMedID)
Available from: 2024-06-04 Created: 2024-06-04 Last updated: 2024-06-04Bibliographically approved
Svensson, P., Schwob, L., Grånäs, O., Unger, I., Björneholm, O., Timneanu, N., . . . Berholts, M. (2024). Heavy element incorporation in nitroimidazole radiosensitizers: molecular-level insights into fragmentation dynamics. Physical Chemistry, Chemical Physics - PCCP, 26(2), 770-779
Open this publication in new window or tab >>Heavy element incorporation in nitroimidazole radiosensitizers: molecular-level insights into fragmentation dynamics
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2024 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 26, no 2, p. 770-779Article in journal (Refereed) Published
Abstract [en]

The present study investigates the photofragmentation behavior of iodine-enhanced nitroimidazole-based radiosensitizer model compounds in their protonated form using near-edge X-ray absorption mass spectrometry and quantum mechanical calculations. These molecules possess dual functionality: improved photoabsorption capabilities and the ability to generate species that are relevant to cancer sensitization upon photofragmentation. Four samples were investigated by scanning the generated fragments in the energy regions around C 1s, N 1s, O 1s, and I 3d-edges with a particular focus on NO2+ production. The experimental summed ion yield spectra are explained using the theoretical near-edge X-ray absorption fine structure spectrum based on density functional theory. Born-Oppenheimer-based molecular dynamics simulations were performed to investigate the fragmentation processes.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2024
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-522697 (URN)10.1039/d3cp03800a (DOI)001090175100001 ()37888897 (PubMedID)
Funder
Swedish Research Council, 2019-03935Swedish Research Council, 2017-05128Swedish Research Council, 2018-00740Swedish Foundation for Strategic ResearchSwedish National Infrastructure for Computing (SNIC), 2022/1-36Swedish National Infrastructure for Computing (SNIC), 2022/22-597
Available from: 2024-02-08 Created: 2024-02-08 Last updated: 2024-02-08Bibliographically approved
Pihlava, L., Svensson, P., Kukk, E., Kooser, K., De Santis, E., Tonisoo, A., . . . Berholts, M. (2024). Shell-dependent photofragmentation dynamics of a heavy-atom-containing bifunctional nitroimidazole radiosensitizer. Physical Chemistry, Chemical Physics - PCCP, 26(11), 8879-8890
Open this publication in new window or tab >>Shell-dependent photofragmentation dynamics of a heavy-atom-containing bifunctional nitroimidazole radiosensitizer
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2024 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 26, no 11, p. 8879-8890Article in journal (Refereed) Published
Abstract [en]

Radiation therapy uses ionizing radiation to break chemical bonds in cancer cells, thereby causing DNA damage and leading to cell death. The therapeutic effectiveness can be further increased by making the tumor cells more sensitive to radiation. Here, we investigate the role of the initial halogen atom core hole on the photofragmentation dynamics of 2-bromo-5-iodo-4-nitroimidazole, a potential bifunctional radiosensitizer. Bromine and iodine atoms were included in the molecule to increase the photoionization cross-section of the radiosensitizer at higher photon energies. The fragmentation dynamics of the molecule was studied experimentally in the gas phase using photoelectron-photoion-photoion coincidence spectroscopy and computationally using Born-Oppenheimer molecular dynamics. We observed significant changes between shallow core (I 4d, Br 3d) and deep core (I 3d) ionization in fragment formation and their kinetic energies. Despite the fact, that the ions ejected after deep core ionization have higher kinetic energies, we show that in a cellular environment, the ion spread is not much larger, keeping the damage well-localized. A study on photodissociation dynamics of 2-bromo-5-iodo-nitroimidazole - a model radiosensitizer - using coincidence spectroscopy and computational methods.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2024
National Category
Atom and Molecular Physics and Optics Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-528495 (URN)10.1039/d4cp00367e (DOI)001175892400001 ()38426309 (PubMedID)
Funder
Swedish Research Council, 2023-04346Swedish Research Council, 2018-00740
Available from: 2024-05-22 Created: 2024-05-22 Last updated: 2024-05-22Bibliographically approved
Walz, M.-M., Signorelli, M. R., Caleman, C., Costa, L. T. & Björneholm, O. (2024). The Surface of Ionic Liquids in Water: From an Ionic Tug of War to a Quasi-Ordered Two-Dimensional Layer. ChemPhysChem, 25(1), Article ID e202300551.
Open this publication in new window or tab >>The Surface of Ionic Liquids in Water: From an Ionic Tug of War to a Quasi-Ordered Two-Dimensional Layer
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2024 (English)In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 25, no 1, article id e202300551Article in journal (Refereed) Published
Abstract [en]

The sustainable development encompasses the search for new materials for energy storage, gas capture, separation, and solvents in industrial processes that can substitute conventional ones in an efficient and clean manner. Ionic liquids (ILs) emerged and have been advanced as alternative materials for such applications, but an obstacle is their hygroscopicity and the effects on their physical properties in the presence of humidity. Several industrial processes depend on the aqueous interfacial properties, and the main focus of this work is the water/IL interface. The behavior of the aqueous ionic liquids at the water-vacuum interface is representative for their water interfacial properties. Using X-ray photoelectron spectroscopy in combination with molecular dynamics simulations we investigate four aqueous IL systems, and provide molecular level insight on the interfacial behaviour of the ionic liquids, such as ion-pair formation, orientation and surface concentration. We find that ionic liquids containing a chloride anion have a lowered surface enrichment due to the low surface propensity of chloride. In contrast, the ionic liquids containing a bistriflimide anion are extremely surface-enriched due to cooperative surface propensity between the cations and anions, forming a two-dimensional ionic liquid on the water surface at low concentrations. Ionic liquids are interesting materials for many applications related to sustainable development, but the effects of water on their properties are insufficiently known. Using X-ray photoelectron spectroscopy and molecular dynamics simulations, we show how the surface propensity of four ionic liquids in aqueous solution vary with the molecular structure of the ions, and discuss the underlying driving forces.+image

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2024
Keywords
ionic liquids, molecular dynamics, water-IL interface, water surface, XPS
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-528473 (URN)10.1002/cphc.202300551 (DOI)001105563800001 ()37991256 (PubMedID)
Funder
Swedish Research Council, VR 2017-04162
Available from: 2024-05-23 Created: 2024-05-23 Last updated: 2024-05-23Bibliographically approved
Tzomos, E., Mikkela, M.-H. -., Ohrwall, G., Björneholm, O. & Tchaplyguine, M. (2023). Ag-oxide signature in Ag 3d photoelectron spectra: A study on free nanoparticles. Surface Science, 733, Article ID 122307.
Open this publication in new window or tab >>Ag-oxide signature in Ag 3d photoelectron spectra: A study on free nanoparticles
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2023 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 733, article id 122307Article in journal (Refereed) Published
Abstract [en]

Over decades the Ag 3d-level binding energy has been puzzling researchers with its unusual sign and value in silver oxides. For the absolute majority of metals, the metal-to-oxide binding energy shifts are positive and depend significantly on the oxidation state, while in Ag-oxides the oxide shift was time after time reported negative, small, and close for the two very different Ag(I) and Ag(III) oxidation states. In the current work, a photoelectron spectroscopy (PES) investigation on the in -situ created free nanoparticles simultaneously containing both metallic silver and silver-oxide parts provided the grounds to reconsider the old consensus on the Ag-oxide shifts. The Ag 3d energies for the metallic and the oxide parts established in the current experimental work allowed estimating a approximate to 1.2 eV positive shift for the realized oxidation state. This estimate was made possible by using a beam of free nanoparticles with finely controlled composition. The PES experiments on such a beam allowed for a continuous and fast renewal of the poorly conducting sample and for a reliable and accurate calibration relative to vacuum. The constant oxide shift observed at several different oxidation conditions, as well as the relatively narrow and symmetric oxide peaks, point to one dominating oxidation state being present in the particles.

Place, publisher, year, edition, pages
ELSEVIER, 2023
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-503204 (URN)10.1016/j.susc.2023.122307 (DOI)000986208900001 ()
Available from: 2023-06-30 Created: 2023-06-30 Last updated: 2023-06-30Bibliographically approved
Björneholm, O. & Muchova, E. (2023). Hot spots of radiation damage from extensive water ionization around metal ions. Nature Chemistry, 15(10), 1338-1339
Open this publication in new window or tab >>Hot spots of radiation damage from extensive water ionization around metal ions
2023 (English)In: Nature Chemistry, ISSN 1755-4330, E-ISSN 1755-4349, Vol. 15, no 10, p. 1338-1339Article in journal, Editorial material (Other academic) Published
Abstract [en]

Radiation damage in biological systems by radicals and low-energy electrons formed from water ionization is a consequence of ultrafast processes that follow core-level ionization of hydrated metal ions. More details of the complex pathway are now revealed from the study of aluminium-ion relaxation through sequential electron-transfer-mediated decay.

Place, publisher, year, edition, pages
Springer Nature, 2023
National Category
Biochemistry and Molecular Biology Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-520974 (URN)10.1038/s41557-023-01332-9 (DOI)001060587700001 ()37644123 (PubMedID)
Available from: 2024-01-19 Created: 2024-01-19 Last updated: 2024-01-19Bibliographically approved
Gopakumar, G., Unger, I., Slavicek, P., Hergenhahn, U., Oehrwall, G., Malerz, S., . . . Björneholm, O. (2023). Radiation damage by extensive local water ionization from two-step electron-transfer-mediated decay of solvated ions. Nature Chemistry, 15(10), 1408-+
Open this publication in new window or tab >>Radiation damage by extensive local water ionization from two-step electron-transfer-mediated decay of solvated ions
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2023 (English)In: Nature Chemistry, ISSN 1755-4330, E-ISSN 1755-4349, Vol. 15, no 10, p. 1408-+Article in journal (Refereed) Published
Abstract [en]

Biomolecular radiation damage is largely mediated by radicals and low-energy electrons formed by water ionization rather than by direct ionization of biomolecules. It was speculated that such an extensive, localized water ionization can be caused by ultrafast processes following excitation by core-level ionization of hydrated metal ions. In this model, ions relax via a cascade of local Auger-Meitner and, importantly, non-local charge- and energy-transfer processes involving the water environment. Here, we experimentally and theoretically show that, for solvated paradigmatic intermediate-mass Al3+ ions, electronic relaxation involves two sequential solute-solvent electron transfer-mediated decay processes. The electron transfer-mediated decay steps correspond to sequential relaxation from Al5+ to Al3+ accompanied by formation of four ionized water molecules and two low-energy electrons. Such charge multiplication and the generated highly reactive species are expected to initiate cascades of radical reactions.

Place, publisher, year, edition, pages
Nature Publishing Group, 2023
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-526069 (URN)10.1038/s41557-023-01302-1 (DOI)001188164500001 ()37620544 (PubMedID)
Available from: 2024-04-05 Created: 2024-04-05 Last updated: 2024-04-05Bibliographically approved
Carravetta, V., de Abreu Gomes, A. H., Teixeira Marinho, R. d., Ohrwall, G., Ågren, H., Björneholm, O. & de Brito, A. N. (2022). An atomistic explanation of the ethanol-water azeotrope. Physical Chemistry, Chemical Physics - PCCP, 24(42), 26037-26045
Open this publication in new window or tab >>An atomistic explanation of the ethanol-water azeotrope
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2022 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, no 42, p. 26037-26045Article in journal (Refereed) Published
Abstract [en]

Ethanol and water form an azeotropic mixture at an ethanol molecular percentage of similar to 91% (similar to 96% by volume), which prohibits ethanol from being further purified via distillation. Aqueous solutions at different concentrations in ethanol have been studied both experimentally and theoretically. We performed cylindrical micro-jet photoelectron spectroscopy, excited by synchrotron radiation, 70 eV above C1s ionization threshold, providing optimal atomic-scale surface-probing. Large model systems have been employed to simulate, by molecular dynamics, slabs of the aqueous solutions and obtain an atomistic description of both bulk and surface regions. We show how the azeotropic behaviour results from an unexpected concentration-dependence of the surface composition. While ethanol strongly dominates the surface and water is almost completely depleted from the surface for most mixing ratios, the different intermolecular bonding patterns of the two components cause water to penetrate to the surface region at high ethanol concentrations. The addition of surface water increases its relative vapour pressure, giving rise to the azeotropic behaviour.

Place, publisher, year, edition, pages
Royal Society of Chemistry (RSC), 2022
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-495784 (URN)10.1039/d2cp03145k (DOI)000870768900001 ()36268753 (PubMedID)
Funder
Swedish Research Council, 2017-04162Swedish Research Council, 2016-03619Swedish Research Council, 2018-07152Vinnova, 2018-04969Swedish Research Council Formas, 2019-02496
Available from: 2023-02-08 Created: 2023-02-08 Last updated: 2023-02-08Bibliographically approved
Ågren, H., Björneholm, O., Ohrwall, G., Carravetta, V. & de Brito, A. N. (2022). Ethanol in Aqueous Solution Studied by Microjet Photoelectron Spectroscopy and Theory. Accounts of Chemical Research, 55(21), 3080-3087
Open this publication in new window or tab >>Ethanol in Aqueous Solution Studied by Microjet Photoelectron Spectroscopy and Theory
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2022 (English)In: Accounts of Chemical Research, ISSN 0001-4842, E-ISSN 1520-4898, Vol. 55, no 21, p. 3080-3087Article, review/survey (Refereed) Published
Abstract [en]

By combining results and analysis from cylindrical microjet photoelectron spectroscopy (cMJ-PES) and theoretical simulations, we unravel the microscopic properties of ethanol-water solutions with respect to structure and intermolecular bonding patterns following the full concentration scale from 0 to 100% ethanol content. In particular, we highlight the salient differences between bulk and surface. Like for the pure water and alcohol constituents, alcohol-water mixtures have attracted much interest in applications of X-ray spectroscopies owing to their potential of combining electronic and geometric structure probing. The water mixtures of the two simplest alcohols, methanol and ethanol, have generated particular attention due to their delicate hydrogen bonding networks that underlie their structural and thermodynamic properties. Macroscopically ethanol-water seems to mix very well, however microscopically this is not true. The aberrant thermodynamics of water-alcohol mixtures have been suggested to be caused by energy differences of hydrogen bonding between water-water, alcohol- alcohol and alcohol-water molecules. These networks may perturb the local character of the interaction between X-rays and matter, calling for analysis that go beyond the normally applied local selection and building block rules and that can combine the effects of light-matter, intra-and intermolecular interactions. However, despite decades of ongoing research there are still controversies of the precise nature of hydrogen bonding networks that underlie the mixing of these simple molecules. Our combined analysis indicates that at low concentration ethanol molecules form a film at the surface since ethanol at the surface can expose its hydrophobic part to the vacuum retaining its two (or three) possible hydrogen bonds, while water at the surface cannot retain all its four possible hydrogen bonds. Thus, ethanol at the surface becomes energetically favorable. Ethanol molecules show a tilting angle variation of the C-C axis with respect to the surface normal as large as 60 degrees at very low concentration. In bulk, around ca. ten %, the ethanol oxygen atoms tend to make a third acceptor hydrogen bond to water molecules. At ca. 20 %, there is a U-shaped change in the CH3 to CH2OH binding energy (BE) shift indicating the presence of ring-like agglomerates called clathrate structures. At the surface, between 5 and 25%, ethanol forms a closely packed layer with the smallest C-C tilting angle variation down to similar to 20 degrees. Above 25% and below the azeotrope at the surface, ethanol shows an increase in the tilting angle variation, while at very high ethanol concentrations water tends to move to the surface so giving a microscopic explanation of the azeotrope effect. This migration is connected to the presence of longer (shorter) ethanol chains in the bulk (surface). A brief comparison with discussions and predictions from other spectroscopic techniques is also given. We emphasize the execution of an integrated approach that combines molecular structural dynamics with quantum predictions of the core electronic chemical shift, so establishing a protocol with considerable interpretative as well as predictive power for cMJ-PES measurements. We believe that this protocol can valorize cMJPES for studies of properties of other alcohol mixtures as well as of binary solutions in general.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2022
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-497513 (URN)10.1021/acs.accounts.2c00471 (DOI)000874736200001 ()36251058 (PubMedID)
Funder
Swedish Research Council, 2017-04162Swedish Research Council, 2016- 03619
Available from: 2023-03-01 Created: 2023-03-01 Last updated: 2023-03-01Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-7307-5404

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