Chirped-Pulse Fourier Transform Microwave Spectroscopy of Fluoroiodoacetonitrile and Chloropentafluoroacetone (open access)

Chirped-Pulse Fourier Transform Microwave Spectroscopy of Fluoroiodoacetonitrile and Chloropentafluoroacetone

This work focuses on finding the complete iodine and nitrogen nuclear electric quadrupole coupling tensors for fluoroiodoacetonitrile using chirped-pulse Fourier transform microwave spectroscopy. Fluoroiodoacetonitrile contains two hyperfine nuclei, iodine (I=5/2) and nitrogen (I=1) and the spectra were observed with great resolution. A total of 499 transitions were observed for this molecule. The a, b and c rotational constants were obtained. A study of chloropentafluoroacetone was also done using chirped-pulse Fourier transform microwave spectroscopy. The two chlorine isotopes for this molecule, Cl-35 and Cl-37 were observed and 326 and 170 transitions were recorded, respectively.
Date: December 2010
Creator: Kadiwar, Gautam
System: The UNT Digital Library
Homework versus daily quizzes: The effects on academic performance within high school pre-AP chemistry. (open access)

Homework versus daily quizzes: The effects on academic performance within high school pre-AP chemistry.

This research proposed to evaluate whether homework or daily quizzes were better for academic success within high-school pre-AP chemistry or if differences in the two methods were detectable. The study involved two years of data where homework was assigned and graded and one year of data where homework was suggested but daily quizzes provided the assessment. The mean of each of the unit tests were evaluated and t-tests were calculated. The results showed that over two-thirds of the units had statistically significant data when daily quizzes were utilized.
Date: August 2010
Creator: King, Jo Laurie Marushia
System: The UNT Digital Library
Forensic Science Applications Utilizing Nanomanipulation-Coupled to Nanospray Ionization-Mass Spectrometry for the Analysis of Ultra-Trace Illicit Drugs (open access)

Forensic Science Applications Utilizing Nanomanipulation-Coupled to Nanospray Ionization-Mass Spectrometry for the Analysis of Ultra-Trace Illicit Drugs

Presented in this thesis are two methods that are coupled to the instrumentation for the recovery and analysis of ultra-trace illicit drug residues. The electrostatic dust lifting process is coupled with nanomanipulation-nanospray ionization to retrieve drug particles off of hard surfaces for analysis. For the second method, drug residues from fingerprint impressions are extracted followed by analysis. The methodology of these hyphenated techniques toward forensic science applications is applied as to explore limits of detection, sensitivity, and selectivity of analytes as well as immediacy and efficiency of analysis. The application of nanomanipulation-coupled to nanospray ionization-mass spectrometry toward forensic science based applications is considered as future improvements to trace and ultra-trace analysis.
Date: December 2010
Creator: Wallace, Nicole
System: The UNT Digital Library
Syntheses, X-ray Diffraction Structures, and Kinetics on New Formamidinate-Substituted Triosmium Clusters (open access)

Syntheses, X-ray Diffraction Structures, and Kinetics on New Formamidinate-Substituted Triosmium Clusters

The reaction between the formamidine ligand PriN=CHNHPri and the activated cluster Os3(CO)10(MeCN)2 has been studied. A rapid reaction is observed at room temperature, yielding the hydride clusters HOs3(CO)9[μ-OCNPriC(H)NPri] and HOs3(CO)10[μ-NPriC(H)NPri] as the principal products. The spectroscopic data and X-ray diffraction structures of those formamidinate-substituted clusters will be present. The thermal reactivity of the clusters has been investigated, with the face-capped cluster HOs3(CO)9[μ-NPriC(H)NPri] found as the sole observable product. The relationship between these three clusters has been established by kinetic studies, the results of which will be discussed.
Date: December 2010
Creator: Yang, Li
System: The UNT Digital Library
Soft Landing Ion Mobility Mass Spectrometry: History, Instrumentation and an Ambient Pressure Application (open access)

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

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.
Date: December 2010
Creator: Birdwell, David
System: The UNT Digital Library
Nanoparticles Engineered to Bind Serum Albumin: Microwave Assisted Synthesis, Characterization, and Functionalization of Fluorescently-Labeled, Acrylate-Based, Polymer Nanoparticles (open access)

Nanoparticles Engineered to Bind Serum Albumin: Microwave Assisted Synthesis, Characterization, and Functionalization of Fluorescently-Labeled, Acrylate-Based, Polymer Nanoparticles

The potential use of polymeric, functionalized nanoparticles (NPs) as drug delivery vectors was explored. Covalent conjugation of albumin to the surface of NPs via maleimide chemistry proved problematic. However, microwave assisted synthesis of NPs was not only time efficient, but enabled the exploration of size control by changing the following parameters: temperature, microwave power, reaction time, initiator concentration, and percentage of monomer used. About 1.5 g of fluorescently-labeled, carboxylic acid-functionalized NPs (100 nm diameter) were synthesized for a total cost of less than $1. Future work will address further functionalization of the NPs for the coupling of albumin (or other targeted proteins), and tests for in vivo biodistribution.
Date: August 2010
Creator: Hinojosa, Barbara R.
System: The UNT Digital Library
Synthesis and Screening of a Combinatorial Peptide Library for Ligands to Target Transferrin: Miniaturizing the Library (open access)

Synthesis and Screening of a Combinatorial Peptide Library for Ligands to Target Transferrin: Miniaturizing the Library

Combinatorial libraries are used in the search for ligands that bind to target proteins. Fmoc solid-phase peptide synthesis is routinely used to generate such libraries. Microwave-assisted peptide synthesis was employed here to decrease reaction times by 80-90%. Two One-Bead-One-Compound combinatorial libraries were synthesized on 130μm beads (one containing 750 members and the other 16, 807). The use of smaller solid supports would have many important practical advantages including; increased library diversity per unit mass, smaller quantities of library needed to generate hits, and screening could be conducted by using a standard flow cytometer. To this end, a miniaturized peptide library was synthesized on 20 μm beads to demonstrate proof of principle. A small sample from the 16,807-member library was screened against transferrin-AlexaFluro 647, a protein responsible for iron transport in vivo. A number of hits were identified and sequenced using techniques coupling nanomanipulation with nanoelectrospray mass spectrometry.
Date: August 2010
Creator: Brown, Jennifer Marie
System: The UNT Digital Library
The Pure Rotational Spectra of Diatomics and Halogen-Addition Benzene Measured by Microwave and Radio Frequency Spectrometers (open access)

The Pure Rotational Spectra of Diatomics and Halogen-Addition Benzene Measured by Microwave and Radio Frequency Spectrometers

Two aluminum spherical mirrors with radii of 203.2 mm and radii of curvature also of 203.2 mm have been used to construct a tunable Fabry-Perót type resonator operational at frequencies as low as 500 MHz. The resonator has been incorporated into a pulsed nozzle, Fourier transform, Balle-Flygare spectrometer. The spectrometer is of use in recording low J transitions of large asymmetric molecules where the spectra are often greatly simplified compared to higher frequency regions. The resonators use is illustrated by recording the rotational spectra of bromobenzene and iodobenzene. In related experiments, using similar equipment, the pure rotational spectra of four isotopomers of SrS and all three naturally occurring isotopomers of the actinide-containing compound thorium monoxide have been recorded between 6 and 26 GHz. The data have been thoroughly analyzed to produce information pertaining to bond lengths and electronic structures.
Date: August 2010
Creator: Etchison, Kerry C.
System: The UNT Digital Library
Effect of Fluorine and Hydrogen Radical Species on Modified Oxidized Ni(pt)si (open access)

Effect of Fluorine and Hydrogen Radical Species on Modified Oxidized Ni(pt)si

NiSi is an attractive material in the production of CMOS devices. The problem with the utilization of NiSi, is that there is no proper method of cleaning the oxide on the surface. Sputtering is the most common method used for the cleaning, but it has its own complications. Dry cleaning methods include the reactions with radicals and these processes are not well understood and are the focus of the project. Dissociated NF3 and NH3 were used as an alternative and XPS is the technique to analyze the reactions of atomic fluorine and nitrogen with the oxide on the surface. A thermal cracker was used to dissociate the NF3 and NH3 into NFx+F and NHx+H. There was a formation of a NiF2 layer on top of the oxide and there was no evidence of nitrogen on the surface indicating that the fluorine and hydrogen are the reacting species. XPS spectra, however, indicate that the substrate SiO2 layer is not removed by the dissociated NF3 and NiF2 growth process. The NiF2 over layer can be reduced to metallic Ni by reacting with dissociated NH3 at room temperature. The atomic hydrogen from dissociated ammonia reduces the NiF2 but it was determined that the …
Date: May 2010
Creator: Gaddam, Sneha Sen
System: The UNT Digital Library
Microwave-Assisted Synthesis, Characterization, and Photophysical Properties of New Rhenium(I) Pyrazolyl-Triazine Complexes (open access)

Microwave-Assisted Synthesis, Characterization, and Photophysical Properties of New Rhenium(I) Pyrazolyl-Triazine Complexes

The reaction of the chelating ligand 4-[4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazin-2-yl]-N,N-diethyl-benzenamine, L, with pentacarbonylchlororhenium by conventional heating method produces the complexes fac-[ReL(CO)3Cl2] and fac-[Re2L(CO)6Cl2] in a period of 48 hours. The use of microwaves as the source of heat and the increase in the equivalents of one of the reactants leads to a more selective reaction and also decreases the reaction time to 1 hour. After proper purification, the photophysical properties of fac-[ReL(CO)3Cl] were analyzed. The solid-state photoluminescence analysis showed an emission band at 628 nm independent of temperature. However, in the solution studies, the emission band shifted from 550 nm in frozen media to 610 nm when the matrix became fluid. These results confirm that this complex possess a phenomenon known as rigidochromism.
Date: May 2010
Creator: Salazar Garza, Gustavo Adolfo
System: The UNT Digital Library