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Quantitative Methods for Examining Ligand Reaction Mechanisms at Semiconductor Nanocrystal Surfaces.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Quantitative Methods for Examining Ligand Reaction Mechanisms at Semiconductor Nanocrystal Surfaces./
作者:	Kessler, Melody L.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
面頁冊數:	257 p.
附註:	Source: Dissertations Abstracts International, Volume: 83-03, Section: B.
Contained By:	Dissertations Abstracts International83-03B.
標題:	Physical chemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28646130
ISBN:	9798538118069

Quantitative Methods for Examining Ligand Reaction Mechanisms at Semiconductor Nanocrystal Surfaces.
Kessler, Melody L.

Quantitative Methods for Examining Ligand Reaction Mechanisms at Semiconductor Nanocrystal Surfaces. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 257 p.

Source: Dissertations Abstracts International, Volume: 83-03, Section: B.

Thesis (Ph.D.)--The University of North Carolina at Chapel Hill, 2021.

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

Semiconductor nanocrystals exhibit optical properties that originate from the quantum confinement of charge carriers when one or more dimensions of the material decreases below the exciton Bohr radius; these properties are attractive for implementation in optoelectronic and photovoltaic device architectures. Quasi-spherical semiconductor nanocrystals called quantum dots experience quantum confinement in three dimensions and are commonly less than five nanometers in diameter. Due to their small size, the semiconductor lattice core accounts for a relatively low proportion of the nanocrystal-chemical reactivity and tunability are primarily governed by the molecular ligand shell which passivates the inorganic ions of the terminating lattice planes.Interrogation of the molecular-level surface structure and reactivity of the semiconductor crystal is difficult to obtain directly by microscopy, necessitating use of a combination of spectroscopic and chemical methods. To gain insight into the structure and reactivity of the ligand-lattice interface, quantitative titrations with chemical probes which undergo predicable reactivity were first employed to elucidate unknown surface topology. Conversely, chemical probes which proceed through unknown and convoluted reaction mechanisms were next interpreted in light of new understanding of the surface structure advanced within this dissertation. To further extend this work, both chemical and redox probes were combined to investigate the thermodynamic potential of metal-based charge carrier trap states at nanocrystal surfaces.The semiconductor nanocrystals studied herein are passivated by oleate ligands, which contain spectroscopic handles ideal for quantification by nuclear magnetic resonance spectroscopic titrations. Ligand-based chemical probes investigated during this work include thiols and carboxylic acids with spectroscopic handles distinct from those of the native oleate ligands. Peak area, peak shifting, and peak broadening of each resonance yield information about the quantity of bound and free ligands as well as qualitative insight into ligand exchange equilibria. The reaction mechanisms examined during this research include L-type binding, X-type exchange, and Z-type displacement coupled with L-type binding to either the nanocrystal surface or the liberated Z-type ligand. Aided by inductively coupled plasma mass spectrometry, novel insight into Z-type ligand displacement mechanisms and associated equilibria envisaged a site-specific map of chemical reactivity.

ISBN: 9798538118069Subjects--Topical Terms:

1981412
Physical chemistry.
Subjects--Index Terms:

Lead sulfide

Quantitative Methods for Examining Ligand Reaction Mechanisms at Semiconductor Nanocrystal Surfaces.
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245 1 0 $a Quantitative Methods for Examining Ligand Reaction Mechanisms at Semiconductor Nanocrystal Surfaces.
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300 $a 257 p.
500 $a Source: Dissertations Abstracts International, Volume: 83-03, Section: B.
500 $a Advisor: Dempsey, Jillian L.
502 $a Thesis (Ph.D.)--The University of North Carolina at Chapel Hill, 2021.
506 $a This item must not be sold to any third party vendors.
520 $a Semiconductor nanocrystals exhibit optical properties that originate from the quantum confinement of charge carriers when one or more dimensions of the material decreases below the exciton Bohr radius; these properties are attractive for implementation in optoelectronic and photovoltaic device architectures. Quasi-spherical semiconductor nanocrystals called quantum dots experience quantum confinement in three dimensions and are commonly less than five nanometers in diameter. Due to their small size, the semiconductor lattice core accounts for a relatively low proportion of the nanocrystal-chemical reactivity and tunability are primarily governed by the molecular ligand shell which passivates the inorganic ions of the terminating lattice planes.Interrogation of the molecular-level surface structure and reactivity of the semiconductor crystal is difficult to obtain directly by microscopy, necessitating use of a combination of spectroscopic and chemical methods. To gain insight into the structure and reactivity of the ligand-lattice interface, quantitative titrations with chemical probes which undergo predicable reactivity were first employed to elucidate unknown surface topology. Conversely, chemical probes which proceed through unknown and convoluted reaction mechanisms were next interpreted in light of new understanding of the surface structure advanced within this dissertation. To further extend this work, both chemical and redox probes were combined to investigate the thermodynamic potential of metal-based charge carrier trap states at nanocrystal surfaces.The semiconductor nanocrystals studied herein are passivated by oleate ligands, which contain spectroscopic handles ideal for quantification by nuclear magnetic resonance spectroscopic titrations. Ligand-based chemical probes investigated during this work include thiols and carboxylic acids with spectroscopic handles distinct from those of the native oleate ligands. Peak area, peak shifting, and peak broadening of each resonance yield information about the quantity of bound and free ligands as well as qualitative insight into ligand exchange equilibria. The reaction mechanisms examined during this research include L-type binding, X-type exchange, and Z-type displacement coupled with L-type binding to either the nanocrystal surface or the liberated Z-type ligand. Aided by inductively coupled plasma mass spectrometry, novel insight into Z-type ligand displacement mechanisms and associated equilibria envisaged a site-specific map of chemical reactivity.
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650 4 $a Morphology. $3 591167
650 4 $a Chemistry. $3 516420
650 4 $a Nanoscience. $3 587832
653 $a Lead sulfide
653 $a Ligands
653 $a Nanocrystals
653 $a Quantum dots
653 $a Semiconductors
653 $a Surface chemistry
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690 $a 0287
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690 $a 0485
710 2 $a The University of North Carolina at Chapel Hill. $b Chemistry. $3 1021872
773 0 $t Dissertations Abstracts International $g 83-03B.
790 $a 0153
791 $a Ph.D.
792 $a 2021
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28646130