Energy-transfer, electron-transfer, and atom/group-transfer resulting from low-energy ion-surface collisions characterize hydrocarbon, fluorocarbon, and mixed self-assembled monolayers

Persistent Link:
http://hdl.handle.net/10150/280208
Title:
Energy-transfer, electron-transfer, and atom/group-transfer resulting from low-energy ion-surface collisions characterize hydrocarbon, fluorocarbon, and mixed self-assembled monolayers
Author:
Smith, Darrin Lee
Issue Date:
2002
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Organic thin films (alkanethiolates chemisorbed on gold) were employed in low-energy (eV) ion-surface collisions to validate the technique as a surface analysis tool and to further investigate processes associated with ion-surface interactions. Low-energy ion surface collisions of small polyatomic and atomic ions with self-assembled monolayers (SAMs) ascertain the chemical composition, structure, and quality of SAMs utilizing four processes: energy transfer (fragmentation of projectile ions: surface-induced dissociation (SID)), electron transfer (neutralization of the projectile ions), atom/group transfer (reaction between the projectile ion and atom/groups from SAMs), and chemical sputtering. Low-energy ion-surface collisions were used to investigate newly synthesized fluorinated compounds where the degree of fluorination of the thiolate tail group increases. Data indicate that substitution of CH₃ with CF₃ as the terminal group has a substantial influence on energy transfer, electron transfer, and atom/group transfer. Slight penetration into a depth of SAM films is illustrated by the formation of certain ion-surface reaction products (a result not observed for previously characterized Langmuir-Blodgett (L-B) films). A novel neutralization mechanism for reaction between methyl cation and hydrocarbon and fluorocarbon SAMs was established. Ion neutralization (besides direct electron transfer) results from a hydride ion transfer, methyl anion transfer, or fluoride transfer between hydrocarbon and fluorocarbon SAMs and incoming methyl cations. Experimental ion-surface and ion-molecule data support the ion neutralization mechanism originally proposed by ab initio and thermochemical calculations. Ion-surface processes were also used to characterize three mixed SAM systems (system 1: hydroxyl/hydrocarbon mixed SAMs and systems 2 and 3: fluorocarbon/hydrocarbon mixed SAMs). The mixed SAMs were prepared from binary thiol solutions and uniform solutions of asymmetrical disulfides. These ion-surface data can be useful for qualitative (identification of the sample's chemical composition) and quantitative analysis (calculation of the surface concentration of a chemical species for a mixed SAM). An in-line Sector-Time-of-Flight (TOF) tandem mass spectrometer with low-energy ion-surface collisions was characterized. Research involved testing the versatility of the instrument in terms of effective ion activation (peptide fragmentation) and surface analysis of organic thin films. This prototype will aid further implementation of SID into commercial TOF instruments for efficient ion activation and surface analysis capabilities.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Chemistry, Analytical.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Chemistry
Degree Grantor:
University of Arizona
Advisor:
Wysocki, Vicki H.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleEnergy-transfer, electron-transfer, and atom/group-transfer resulting from low-energy ion-surface collisions characterize hydrocarbon, fluorocarbon, and mixed self-assembled monolayersen_US
dc.creatorSmith, Darrin Leeen_US
dc.contributor.authorSmith, Darrin Leeen_US
dc.date.issued2002en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractOrganic thin films (alkanethiolates chemisorbed on gold) were employed in low-energy (eV) ion-surface collisions to validate the technique as a surface analysis tool and to further investigate processes associated with ion-surface interactions. Low-energy ion surface collisions of small polyatomic and atomic ions with self-assembled monolayers (SAMs) ascertain the chemical composition, structure, and quality of SAMs utilizing four processes: energy transfer (fragmentation of projectile ions: surface-induced dissociation (SID)), electron transfer (neutralization of the projectile ions), atom/group transfer (reaction between the projectile ion and atom/groups from SAMs), and chemical sputtering. Low-energy ion-surface collisions were used to investigate newly synthesized fluorinated compounds where the degree of fluorination of the thiolate tail group increases. Data indicate that substitution of CH₃ with CF₃ as the terminal group has a substantial influence on energy transfer, electron transfer, and atom/group transfer. Slight penetration into a depth of SAM films is illustrated by the formation of certain ion-surface reaction products (a result not observed for previously characterized Langmuir-Blodgett (L-B) films). A novel neutralization mechanism for reaction between methyl cation and hydrocarbon and fluorocarbon SAMs was established. Ion neutralization (besides direct electron transfer) results from a hydride ion transfer, methyl anion transfer, or fluoride transfer between hydrocarbon and fluorocarbon SAMs and incoming methyl cations. Experimental ion-surface and ion-molecule data support the ion neutralization mechanism originally proposed by ab initio and thermochemical calculations. Ion-surface processes were also used to characterize three mixed SAM systems (system 1: hydroxyl/hydrocarbon mixed SAMs and systems 2 and 3: fluorocarbon/hydrocarbon mixed SAMs). The mixed SAMs were prepared from binary thiol solutions and uniform solutions of asymmetrical disulfides. These ion-surface data can be useful for qualitative (identification of the sample's chemical composition) and quantitative analysis (calculation of the surface concentration of a chemical species for a mixed SAM). An in-line Sector-Time-of-Flight (TOF) tandem mass spectrometer with low-energy ion-surface collisions was characterized. Research involved testing the versatility of the instrument in terms of effective ion activation (peptide fragmentation) and surface analysis of organic thin films. This prototype will aid further implementation of SID into commercial TOF instruments for efficient ion activation and surface analysis capabilities.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectChemistry, Analytical.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorWysocki, Vicki H.en_US
dc.identifier.proquest3073257en_US
dc.identifier.bibrecord.b4347603xen_US
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