{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/87889"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/87889","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Structure and Dynamics in Ligand-Protected and Supported Metal Nanoparticles","abstract":"This dissertation describes the use of x-ray absorption spectroscopy (XAS) and advanced electron microscopy methods to develop fundamental understandings of nanoparticle structure. Analysis of the x-ray absorption spectra provides structural information with 0.001 A precision. Quantitative high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) measurements characterize metal clusters and nanoparticles on the basis of the number of metal atoms they contain. Ligand-protected 13-atom gold clusters serve as a model system to illustrate the capabilities of a correlated use of these techniques. They exhibit a molecular density of electronic states and non-bulk icosahedral structure. These gold clusters are further used as precursor in the preparation of titania-supported gold oxidation catalysts via ligand removal using ozone or thermal treatments. The capability of the quantitative HAADF-STEM analysis for the determination of nanoparticle shape is demonstrated in these studies. X-ray absorption spectroscopy studies of sub-nanometer gamma-alumina-supported platinum nanoparticles revealed unprecedented metal-metal bond contraction with increasing temperature. Both the structural and electronic information obtained in the spectroscopic studies suggest that support-particle charge transfer is responsible for these dynamic effects. Supported bimetallic iridium-platinum nanoparticles were also prepared via reduction of a bimetallic cluster precursor. This preparation allowed excellent control of nanoparticle size and compositional distributions as the stoichiometry of the cluster precursor was retained. This was confirmed analytically using energy dispersive x-ray (EDX) spectroscopy of individual nanoparticles. XAS studies revealed that the bimetallic nanoparticles assumed a core-shell structure with an iridium-rich core and a platinum-rich shell. The implementation of a novel analysis method that accounted for the overlap of the iridium and platinum absorption edges allowed the determination of structural parameters with low uncertainties and a consequently well-characterized structural model.","abstract_html":"This dissertation describes the use of x-ray absorption spectroscopy (XAS) and advanced electron microscopy methods to develop fundamental understandings of nanoparticle structure. Analysis of the x-ray absorption spectra provides structural information with 0.001 A precision. Quantitative high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) measurements characterize metal clusters and nanoparticles on the basis of the number of metal atoms they contain. Ligand-protected 13-atom gold clusters serve as a model system to illustrate the capabilities of a correlated use of these techniques. They exhibit a molecular density of electronic states and non-bulk icosahedral structure. These gold clusters are further used as precursor in the preparation of titania-supported gold oxidation catalysts via ligand removal using ozone or thermal treatments. The capability of the quantitative HAADF-STEM analysis for the determination of nanoparticle shape is demonstrated in these studies. X-ray absorption spectroscopy studies of sub-nanometer gamma-alumina-supported platinum nanoparticles revealed unprecedented metal-metal bond contraction with increasing temperature. Both the structural and electronic information obtained in the spectroscopic studies suggest that support-particle charge transfer is responsible for these dynamic effects. Supported bimetallic iridium-platinum nanoparticles were also prepared via reduction of a bimetallic cluster precursor. This preparation allowed excellent control of nanoparticle size and compositional distributions as the stoichiometry of the cluster precursor was retained. This was confirmed analytically using energy dispersive x-ray (EDX) spectroscopy of individual nanoparticles. XAS studies revealed that the bimetallic nanoparticles assumed a core-shell structure with an iridium-rich core and a platinum-rich shell. The implementation of a novel analysis method that accounted for the overlap of the iridium and platinum absorption edges allowed the determination of structural parameters with low uncertainties and a consequently well-characterized structural model.","abstract_has_math":false,"creators":["Menard, Laurent D., Jr"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Nuzzo, Ralph G."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-09-28T21:57:27Z","date_published":"2015-09-28T21:57:27Z","updated_at":"2026-07-22T22:26:31Z","subjects":["Engineering, Materials Science"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(MiAaPQ)AAI3250290"],"render_values":[{"text":"(MiAaPQ)AAI3250290","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/87889","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Nuzzo, Ralph G."]},{"key":"dc:creator","label":"Author","values":["Menard, Laurent D., Jr"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-09-28T21:57:27Z","10000-01-01","2006"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Engineering, Materials Science"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/87889","(MiAaPQ)AAI3250290"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["This dissertation describes the use of x-ray absorption spectroscopy (XAS) and advanced electron microscopy methods to develop fundamental understandings of nanoparticle structure. 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X-ray absorption spectroscopy studies of sub-nanometer gamma-alumina-supported platinum nanoparticles revealed unprecedented metal-metal bond contraction with increasing temperature. Both the structural and electronic information obtained in the spectroscopic studies suggest that support-particle charge transfer is responsible for these dynamic effects. Supported bimetallic iridium-platinum nanoparticles were also prepared via reduction of a bimetallic cluster precursor. This preparation allowed excellent control of nanoparticle size and compositional distributions as the stoichiometry of the cluster precursor was retained. This was confirmed analytically using energy dispersive x-ray (EDX) spectroscopy of individual nanoparticles. XAS studies revealed that the bimetallic nanoparticles assumed a core-shell structure with an iridium-rich core and a platinum-rich shell. 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X-ray absorption spectroscopy studies of sub-nanometer gamma-alumina-supported platinum nanoparticles revealed unprecedented metal-metal bond contraction with increasing temperature. Both the structural and electronic information obtained in the spectroscopic studies suggest that support-particle charge transfer is responsible for these dynamic effects. Supported bimetallic iridium-platinum nanoparticles were also prepared via reduction of a bimetallic cluster precursor. This preparation allowed excellent control of nanoparticle size and compositional distributions as the stoichiometry of the cluster precursor was retained. This was confirmed analytically using energy dispersive x-ray (EDX) spectroscopy of individual nanoparticles. XAS studies revealed that the bimetallic nanoparticles assumed a core-shell structure with an iridium-rich core and a platinum-rich shell. 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