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Metal Oxide Surfaces and Nanoparticl...

Somaratne, Dulanga S.

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Metal Oxide Surfaces and Nanoparticles: Electronic Structure and Reactivity.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Metal Oxide Surfaces and Nanoparticles: Electronic Structure and Reactivity./
作者:	Somaratne, Dulanga S.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2020,
面頁冊數:	125 p.
附註:	Source: Dissertations Abstracts International, Volume: 81-09, Section: B.
Contained By:	Dissertations Abstracts International81-09B.
標題:	Chemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=27548964
ISBN:	9781392501900

Metal Oxide Surfaces and Nanoparticles: Electronic Structure and Reactivity.
Somaratne, Dulanga S.

Metal Oxide Surfaces and Nanoparticles: Electronic Structure and Reactivity. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 125 p.

Source: Dissertations Abstracts International, Volume: 81-09, Section: B.

Thesis (Ph.D.)--University of Massachusetts Lowell, 2020.

This item must not be sold to any third party vendors.

Metal oxide surfaces and nanoparticles are important for numerous applications, including gas sensing, catalysis and optoelectronic devices. This thesis is concerned with several topics related to their electronic structure and reactivity. In the first part of this thesis, the changes in the photoluminescence (PL) of ZnO nanospheres were measured upon exposure to gases and vapors at room temperature. The PL spectrum of ZnO nanospheres consists of an ultraviolet (UV) excitonic emission peak and a visible, defect-related peak. The changes in the relative intensities of these two peaks were correlated with adsorption. It was found that surface hydroxyl groups play an important role in reactive adsorption, such as sulfur dioxide and methanethiol (MT). Density functional theory (DFT) calculations provided theoretical insight by examining the energetics of these reactions with a Zn36O36 model Wurtzite cluster.In the second part, thiol adsorption on more than 10 metal oxide nanoparticles, all having average particle sizes in the 30 nm range, was investigated both experimentally and theoretically with DFT calculations. Experimental studies consisted of a rapid screening method developed by our group in which a thiol-terminated fluorophore was adsorbed from solution and monitored using fluorescence and ultrahigh vacuum dosing of the nanoparticles with MT. Between the two methods, adsorption was consistently only observed on ZnO and TiO2 nanoparticles. To understand this, DFT calculations were performed for thiol adsorption on small metal oxide clusters.The third aspect of this thesis consisted of the deposition of gold and lithium on clean, stoichiometric TiO2(110) at ambient surface temperature in ultrahigh vacuum. It was concluded that the first monolayer (ML) of gold grows two-dimensionally, while subsequently deposited gold forms islands. Downward band bending and the formation of an electron accumulation layer for low gold coverage (θ = 0.12 ML) was confirmed by measuring the shifts of the Ti2p peaks and by comparison of the XPS valence region and the UPS spectrum, which have different photoelectron detection depths. X-ray photoelectron spectroscopy (XPS) indicates that initially deposited Li penetrates into the bulk, with a gradual build-up in the near surface region, and UPS shows the formation of a gap state about 1.4 eV below the Fermi level due to a Ti3+ 3d state. However, there is an absence of observed band bending at low Li coverage, apparently due to the pinning of the Fermi level to the gap state and formation of an accumulation layer that is significantly deeper than the XPS and UPS detection depth.

ISBN: 9781392501900Subjects--Topical Terms:

516420
Chemistry.
Subjects--Index Terms:

Metal oxide surfaces

Metal Oxide Surfaces and Nanoparticles: Electronic Structure and Reactivity.
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500 $a Source: Dissertations Abstracts International, Volume: 81-09, Section: B.
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520 $a Metal oxide surfaces and nanoparticles are important for numerous applications, including gas sensing, catalysis and optoelectronic devices. This thesis is concerned with several topics related to their electronic structure and reactivity. In the first part of this thesis, the changes in the photoluminescence (PL) of ZnO nanospheres were measured upon exposure to gases and vapors at room temperature. The PL spectrum of ZnO nanospheres consists of an ultraviolet (UV) excitonic emission peak and a visible, defect-related peak. The changes in the relative intensities of these two peaks were correlated with adsorption. It was found that surface hydroxyl groups play an important role in reactive adsorption, such as sulfur dioxide and methanethiol (MT). Density functional theory (DFT) calculations provided theoretical insight by examining the energetics of these reactions with a Zn36O36 model Wurtzite cluster.In the second part, thiol adsorption on more than 10 metal oxide nanoparticles, all having average particle sizes in the 30 nm range, was investigated both experimentally and theoretically with DFT calculations. Experimental studies consisted of a rapid screening method developed by our group in which a thiol-terminated fluorophore was adsorbed from solution and monitored using fluorescence and ultrahigh vacuum dosing of the nanoparticles with MT. Between the two methods, adsorption was consistently only observed on ZnO and TiO2 nanoparticles. To understand this, DFT calculations were performed for thiol adsorption on small metal oxide clusters.The third aspect of this thesis consisted of the deposition of gold and lithium on clean, stoichiometric TiO2(110) at ambient surface temperature in ultrahigh vacuum. It was concluded that the first monolayer (ML) of gold grows two-dimensionally, while subsequently deposited gold forms islands. Downward band bending and the formation of an electron accumulation layer for low gold coverage (θ = 0.12 ML) was confirmed by measuring the shifts of the Ti2p peaks and by comparison of the XPS valence region and the UPS spectrum, which have different photoelectron detection depths. X-ray photoelectron spectroscopy (XPS) indicates that initially deposited Li penetrates into the bulk, with a gradual build-up in the near surface region, and UPS shows the formation of a gap state about 1.4 eV below the Fermi level due to a Ti3+ 3d state. However, there is an absence of observed band bending at low Li coverage, apparently due to the pinning of the Fermi level to the gap state and formation of an accumulation layer that is significantly deeper than the XPS and UPS detection depth.
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