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Multicomponent Clusters/Nanoparticles: An Investigation of Electronic and Geometric Properties by Photoelectron Spectroscopy
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. (Svante Svensson)
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Clusters/nanoparticles are aggregates of a “small” number of building blocks, atoms or molecules, ranging from two up to millions of atoms. Two main groups of clusters have been studied using photoelectron spectroscopy based on synchrotron radiation. They are dry/wet alkali-halide clusters, including pure water clusters, and metal-based nanoparticles.

For the dry alkali halide clusters, analysis of the data and theoretical modeling has allowed us insights into the local electronic properties at nanoscale: a change of polarizability of ions in the alkali-halide clusters due to the varying environment has been suggested. The study of the wet salt clusters shows that the alkali-halides are already solvated at the nanoscale reached by water clusters doped with salt vapor.

The photoelectron angular distribution of water cluster shows lower anisotropy parameters as compared to the separate monomers. A model based on intracluster scattering has been built to partly explain the reduction.

In the last part of the thesis, metal-based multi-component nanoparticles have been produced by self-assembly processes using reactive magnetron sputtering. Depending on the specific metal element, oxidation processes have been applied before or after the aggregation. Clearly radial distributions such as core-shell and “sandwich-like” structures have unambiguously determined by photoelectron spectroscopy.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , 92 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1065
Keyword [en]
Clusters, Nanoparticles, Alloy, Atmospheric chemistry, Alkali halide, Transition metals, X-ray Photoelectron spectroscopy, Polarizability, Core-shell, Sandwich structure, MAX-lab, BESSY II
National Category
Condensed Matter Physics Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:uu:diva-205651ISBN: 978-91-554-8730-0 (print)OAI: oai:DiVA.org:uu-205651DiVA: diva2:642352
Public defence
2013-10-03, Room 80101, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2013-09-12 Created: 2013-08-21 Last updated: 2014-01-22
List of papers
1. Ionic bonding in free nanoscale NaCl clusters as seen by photoelectron spectroscopy
Open this publication in new window or tab >>Ionic bonding in free nanoscale NaCl clusters as seen by photoelectron spectroscopy
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2011 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 134, no 12, 124507- p.Article in journal (Refereed) Published
Abstract [en]

The free neutral nanoscale NaCl clusters have been produced in a beam and studied with x-ray photoelectron spectroscopy. High resolution spectra simultaneously containing cluster and molecular-monomer, featuring in both the valence and core-level Na 2p and Cl 2p regions, have been obtained. Cluster-level energy shifts of around 3 eV toward lower binding energy for Na 2p and approximate to 1 eV toward higher binding energy for Cl 2p relative to the monomer levels have been unambiguously established. To rationalize the core-level energy shifts of the nanoscale NaCl clusters, the ionic model taking into account all charge-charge and polarization interactions has been developed and implemented. A satisfactory agreement between the experimental and model results has been obtained. The model calculations have also shed additional light on the size-and site-specific cluster responses.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-152787 (URN)10.1063/1.3570576 (DOI)000289151400043 ()
Available from: 2011-05-02 Created: 2011-05-02 Last updated: 2017-12-11Bibliographically approved
2. Holding onto Electrons in Alkali Metal Halide Clusters: Decreasing Polarizability with Increasing Coordination
Open this publication in new window or tab >>Holding onto Electrons in Alkali Metal Halide Clusters: Decreasing Polarizability with Increasing Coordination
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2012 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 116, no 49, 12104-12111 p.Article in journal (Refereed) Published
Abstract [en]

The connection between the electronic polarizability and the decrease of the system size from macroscopic solid to nanoscale clusters has been addressed in a combined experimental and model-calculation study. A beam of free neutral potassium chloride clusters has been probed using synchrotron-radiation-based photoelectron spectroscopy. The introduction of "effective" polarizability for chlorine, lower than that in molecules and dimers and decreasing with increasing coordination, has allowed us to significantly improve the agreement between the experimental electron binding energies and the electrostatic model predictions. Using the calculated site-specific binding energies, we have been able to assign the spectral details of the cluster response to the ionizing X-ray radiation, and to explain its change with cluster size. From our assignments we find that the higher-coordination face-atom responses in the K 3p spectra increase significantly with increasing cluster size relative to that of the edge atoms. The reasons behind the decrease of polarizability predicted earlier by ab initio calculations are discussed in terms of the limited mobility of the electron clouds caused by the interaction with the neighboring ions.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-191769 (URN)10.1021/jp307786z (DOI)000312175900014 ()
Available from: 2013-01-15 Created: 2013-01-14 Last updated: 2017-12-06Bibliographically approved
3. Solvation at nanoscale: alkali halides in water clusters
Open this publication in new window or tab >>Solvation at nanoscale: alkali halides in water clusters
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2013 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, no 4, 044301- p.Article in journal (Refereed) Published
Abstract [en]

The solvation of alkali-halides in water clusters at nanoscale is studied by photoelectron spectroscopy using synchrotron radiation. The Na 2p, K 3p, Cl 2p, Br 3d, and I 4d core level binding energies have been measured for salt-containing water clusters. The results have been compared to those of alkali halide clusters and the dilute aqueous salt solutions. It is found that the alkali halides dissolve in small water clusters as ions.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2013
National Category
Natural Sciences Atom and Molecular Physics and Optics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-196354 (URN)10.1063/1.4775586 (DOI)000314725900018 ()
Projects
Olle Björneholm
Funder
Swedish Research Council
Available from: 2013-03-08 Created: 2013-03-08 Last updated: 2017-12-06Bibliographically approved
4. The photoelectron angular distribution of water clusters
Open this publication in new window or tab >>The photoelectron angular distribution of water clusters
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2013 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, no 23, 234306- p.Article in journal (Refereed) Published
Abstract [en]

The angular distribution of photoelectrons emitted from water clusters has been measured by linearly polarized synchrotron radiation of 40 and 60 eV photon energy. Results are given for the three outermost valence orbitals. The emission patterns are found more isotropic than for isolated molecules. While a simple scattering model is able to explain most of the deviation from molecular behavior, some of our data also suggest an intrinsic change of the angular distribution parameter. The angular distribution function was mapped by rotating the axis of linear polarization of the synchrotron radiation.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-205013 (URN)10.1063/1.4809748 (DOI)000321012400015 ()
Available from: 2013-08-13 Created: 2013-08-13 Last updated: 2017-12-06Bibliographically approved
5. Core-shell structure in self-assembled lead/lead-oxide nanoclusters revealed by photoelectron spectroscopy
Open this publication in new window or tab >>Core-shell structure in self-assembled lead/lead-oxide nanoclusters revealed by photoelectron spectroscopy
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2013 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 3, 035402- p.Article in journal (Refereed) Published
Abstract [en]

Nanoclusters containing metallic lead and lead oxide have been produced by self-assembly out of a primary mixture of lead atoms and oxygen in a reactive sputtering-based cluster source. Comparison of the valence and core-level responses in the photoelectron spectra shows that clusters have a core-shell structure with a lead-oxide core coated by an outer shell of metallic lead. This core-shell order is opposite to that typical for most microscopic and macroscopic materials. We explain this by the peculiarities of the cluster production kinetics and by the system's energy minimization striving due to what lead oxide is placed in the core of the mixed cluster.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2013
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-193490 (URN)10.1103/PhysRevB.87.035402 (DOI)000312999300005 ()
Funder
TrenOp, Transport Research Environment with Novel PerspectivesEU, European Research Council
Available from: 2013-02-05 Created: 2013-02-04 Last updated: 2017-12-06
6. Radial Structure of Free Yb/YbO Nanoparticles Created by Oxidation Before or After Aggregation with Divalent Instead of Trivalent Oxide
Open this publication in new window or tab >>Radial Structure of Free Yb/YbO Nanoparticles Created by Oxidation Before or After Aggregation with Divalent Instead of Trivalent Oxide
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2013 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 27, 14390-14397 p.Article in journal (Refereed) Published
Abstract [en]

Nanoparticles consisting of Yb and its divalent oxide YbO have been created by two different oxidation approaches based on the gas-aggregation method with magnetron sputtering. In one type of nanoparticles, the Yb oxide molecules, created by reactive sputtering before the aggregation, agglomerate predominantly in the interior of mixed-composition nanoparticles. In the other type, the oxide is formed by exposing the preformed metallic Yb nanoparticles to oxygen, which at certain conditions is believed to oxidize primarily the surface of such nanoparticles. Such segregated stoichiometry has been disclosed using Yb 4f core-level photoelectron spectroscopy at a series of oxidation conditions for each type of production. In contrast to a typical macroscopic case where Yb is trivalent, in both production cases, Yb is divalent in the oxide. By using the production methods suggested, it becomes possible to tailor the electronic and thus the physical and chemical properties of such nanoparticles, which are discussed in the literature as building blocks for photonic, electronic, and magnetic nanoscale devices.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-205567 (URN)10.1021/jp4037556 (DOI)000321883600074 ()
Available from: 2013-08-21 Created: 2013-08-20 Last updated: 2017-12-06Bibliographically approved
7. Alloying and oxidation of free core-shell Al@Yb nanoparticles – an “on-the-fly” study
Open this publication in new window or tab >>Alloying and oxidation of free core-shell Al@Yb nanoparticles – an “on-the-fly” study
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-205650 (URN)
Available from: 2013-08-21 Created: 2013-08-21 Last updated: 2014-01-22Bibliographically approved

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