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  Partner: UNT Libraries
 Department: Department of Chemistry
 Collection: UNT Theses and Dissertations
Soft Landing Ion Mobility Mass Spectrometry: History, Instrumentation and an Ambient Pressure Application

Soft Landing Ion Mobility Mass Spectrometry: History, Instrumentation and an Ambient Pressure Application

Date: December 2010
Creator: Birdwell, David
Description: Preparative mass spectrometry is an important method for the synthesis of new materials. Recently, soft landing mass spectrometry has been used to land ions on surfaces to coat or otherwise alter them. Commercial soft landing instruments do not yet exist, and the physical phenomenon of soft landing has not yet been fully described. For future ion mobility soft landing research, the theory of ion mobility, ion optics and soft landing is discussed, and 2 soft landing instruments have been built and described, along with proof of concept experiments for both instruments. Simulations of the process of ion mobility and ion optics for use in these instruments, as well as some preliminary results for the optics are included. Surfaces described include copper on mica and iron on silicon. Self assembly of soft landed ions is observed on the surfaces. The instruments constructed will be useful for future soft landing research, and soft landing can be used for future materials research with special attention focused on the self-assembly of the landed ions.
Contributing Partner: UNT Libraries
Surface Chemical Deposition of Advanced Electronic Materials

Surface Chemical Deposition of Advanced Electronic Materials

Date: December 2010
Creator: Bjelkevig, Cameron
Description: The focus of this work was to examine the direct plating of Cu on Ru diffusion barriers for use in interconnect technology and the substrate mediated growth of graphene on boron nitride for use in advanced electronic applications. The electrodeposition of Cu on Ru(0001) and polycrystalline substrates (with and without pretreatment in an iodine containing solution) has been studied by cyclic voltammetry (CV), current-time transient measurements (CTT), in situ electrochemical atomic force microscopy (EC-AFM), and X-ray photoelectron spectroscopy (XPS). The EC-AFM data show that at potentials near the OPD/UPD threshold, Cu crystallites exhibit pronounced growth anisotropy, with lateral dimensions greatly exceeding vertical dimensions. XPS measurements confirmed the presence and stability of adsorbed I on the Ru surface following pre-treatment in a KI/H2SO4 solution and following polarization to at least −200 mV vs. Ag/AgCl. CV data of samples pre-reduced in I-containing electrolyte exhibited a narrow Cu deposition peak in the overpotential region and a UPD peak. The kinetics of the electrodeposited Cu films was investigated by CTT measurements and applied to theoretical models of nucleation. The data indicated that a protective I adlayer may be deposited on an air-exposed Ru electrode as the oxide surface is electrochemically reduced, and that this ...
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A Qualitative Analysis of the Products of the Reaction Between Chlorosulfonic Acid and 2, 2, 4-Trimethylpentane

A Qualitative Analysis of the Products of the Reaction Between Chlorosulfonic Acid and 2, 2, 4-Trimethylpentane

Date: 1941
Creator: Black, Harry
Description: This study was made in an attempt to analyze qualitatively the reaction products formed when chlorosulfonic acid reacts with 2, 2, 4-trimethylpentane.
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Photophysical properties of pyrene, 2,7 diazapyrene and 1,3-bis(β-naphthyl)propane.

Photophysical properties of pyrene, 2,7 diazapyrene and 1,3-bis(β-naphthyl)propane.

Date: August 2007
Creator: Boateng, Stephen
Description: The luminescence properties of Van Der Waals' dimers and clusters of pyrene and diazapyrene have been investigated. Excimers, dimeric species which are associative in an excited electronic state and dissociative in their ground state, have long been established and play an important role in many areas of photochemistry. My work here focuses on the luminescence and absorption properties of ground state dimers/aggregates, which are less understood, and allows further characterization of the ground state and excited state association of these aromatic molecules.
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Thermodynamic and Structural Studies of Layered Double Hydroxides

Thermodynamic and Structural Studies of Layered Double Hydroxides

Date: May 1998
Creator: Boclair, Joseph W. (Joseph Walter)
Description: The preparation of layered double hydroxides via titration with sodium hydroxide was thoroughly investigated for a number of M(II)/M(III) combinations. These titration curves were examined and used to calculate nominal solubility product constants and other thermodynamic quantities for the various LDH chloride systems.
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Synthesis and Electron Transfer Studies of Supramolecular Triads

Synthesis and Electron Transfer Studies of Supramolecular Triads

Date: 2016-5
Creator: Bodenstedt, Kurt
Description: This study expands the role of polythiophenes as an electron donating chromophore within energy harvesting milti-modular donor-acceptor systems. The polythiophene moiety would act as an electron donating spacer group between the donor and acceptor entities, viz., phenothiazine and fulleropyrrolidine, respectively, in the newly synthesized supramolecular triads. The triads 10-{[2,2';5',2"] terthiophene-5-fulleropyrrolidine} phenothiazine and 10-{[2,2'] bithiophene-5-fulleropyrrolidine} phenothiazine were synthesized and characterized through electrochemical and spectroscopic methods to ascertain their structural integrity. the componets of the triads were selected for their established redox parameters. Phenothiazine would act as a secondary donor and would facilitate hole-transfer from the polythiophene primary electron donor, due to its ease of oxidation and yield a long-lived charge separated state. Fulleropyrrolidine would act as an acceptor for ease of reductive capabilities and its ability to hold multiple charges. Finally, occurrence of photoinduced electron transferleading to the anticipated charge separated states is established from advanced transient spectroscopic techniques on these novel supramolecular systems.
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The Determination of the Constants in the System of Methyl Alcohol, Acetic Acid, and Water

The Determination of the Constants in the System of Methyl Alcohol, Acetic Acid, and Water

Date: 1940
Creator: Bonner, Virginia Ruth
Description: The purpose of this study is to determine the specific reaction or velocity constants and the equilibrium constant in a system of methyl alcohol and acetic acid, a bimolecular reaction of the second order.
Contributing Partner: UNT Libraries
Knowledge Discovery of Nanotube Mechanical Properties With an Informatics-Molecular Dynamics Approach

Knowledge Discovery of Nanotube Mechanical Properties With an Informatics-Molecular Dynamics Approach

Date: May 2012
Creator: Borders, Tammie L.
Description: Carbon nanotubes (CNT) have unparalleled mechanical properties, spanning several orders of magnitude over both length and time scales. Computational and experimental results vary greatly, partly due to the multitude of variables. Coupling physics-based molecular dynamics (MD) with informatics methodologies is proposed to navigate the large problem space. The adaptive intermolecular reactive empirical bond order (AIREBO) is used to model short range, long range and torsional interactions. A powerful approach that has not been used to study CNT mechanical properties is the derivation of descriptors and quantitative structure property relationships (QSPRs). For the study of defected single-walled CNTs (SWCNT), two descriptors were identified as critical: the density of non-sp2 hybridized carbons and the density of methyl groups functionalizing the surface. It is believed that both of these descriptors can be experimentally measured, paving the way for closed-loop computational-experimental development. Informatics can facilitate discovery of hidden knowledge. Further evaluation of the critical descriptors selected for Poisson’s ratio lead to the discovery that Poisson’s ratio has strain-varying nonlinear elastic behavior. CNT effectiveness in composites is based both on intrinsic mechanical properties and interfacial load transfer. In double-walled CNTs, inter-wall bonds are surface defects that decrease the intrinsic properties but also improve load transfer. ...
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Lipidomic Analysis of Single Cells and Organelles Using Nanomanipulation Coupled to Mass Spectrometry

Lipidomic Analysis of Single Cells and Organelles Using Nanomanipulation Coupled to Mass Spectrometry

Access: Use of this item is restricted to the UNT Community.
Date: 2016-5
Creator: Bowman, Amanda
Description: The capability to characterize disease states by way of determining novel biomarkers has led to a high demand of single cell and organelle analytical methodologies due to the unexpected heterogeneity present in cells of the same type. Lipids are of particular interest in the search for biomarkers due to their active roles in cellular metabolism and energy storage. Analyzing localized lipid chemistry from individual cells and organelles is challenging however, due to low analyte volume, limited discriminate instrumentation, and common requirements of separation procedures and expenditure of cell sample. Using nanomanipulation in combination with mass spectrometry, individual cells and organelles can be extracted from tissues and cultures in vitro to determine if heterogeneity at the cellular level is present. The discriminate extraction of a single cell or organelle allows the remainder of cell culture or tissue to remain intact, while the high sensitivity and chemical specificity of mass spectrometry provides structural information for limited volumes without the need for chromatographic separation. Mass analysis of lipids extracted from individual cells can be carried out in multiple mass spectrometry platforms through direct-inject mass spectrometry using nanoelectrospray-ionization and through matrix-assisted laser/desorption ionization.
Contributing Partner: UNT Libraries
Mercury-sensitized Photochemical Reactions of Isopropyl Alcohol

Mercury-sensitized Photochemical Reactions of Isopropyl Alcohol

Date: 1956
Creator: Brady, William Thomas
Description: The nature and scope of this problem is to determine from the irradiation of isopropyl alcohol with 2537 A, the behavior and mechanism of the reaction, since it is known that a reaction does occur.
Contributing Partner: UNT Libraries