Chemistry Commons^™

Forensic Application Of Chemometric Analysis To Visible Absorption Spectra Collected From Dyed Textile Fibers, Alejandra Flores

Electronic Theses and Dissertations

Forensic analysis of evidence consists of the comparison of physical, spectroscopic, or chemical characteristics of a questioned sample to a set of knowns. Currently, decisions as to whether or not the questioned sample can be associated or grouped with the knowns are left up to the discretion of the forensic analyst. The implications of these outcomes are presented as evidence to a jury in a court of law to determine if a defendant is guilty of committing a crime or not. Leading up to, and since, the publication of the National Academy of Sciences (NAS) report entitled “Strengthening Forensic Science …

Quantitative Assessment Of The Effects Of Microbial Degradation Of A Simple Hydrocarbon Mixture, Jessica Kindell

Electronic Theses and Dissertations

Ignitable liquids consist of either a single organic compound or a complex organic mixture. In regards to fire debris analysis, the analyst is responsible for determining if an ignitable liquid residue is present. However, when extracted from soil-containing fire debris evidence, chemical degradation from microorganisms is observed to result in the loss of compounds based on chemical structure. It can also happen when the evidence container is stored at room temperature before analysis. This can present a challenge to the fire debris analyst when identifying and classifying the ignitable liquid residue based on the criteria established by standard test methods. …

Synthesis, Linear And Nonlinear Photophysical Characterization Of Two Symmetrical Pyrene-Terminated Squaraine Derivatives In Solution, Alfonso Ballestas Barrientos

Electronic Theses and Dissertations

Two indole-based squaraine dyes bonded to two pyrenyl groups through vinyl- and ethynyl- linkers were synthesized with the aim of enhancing the intramolecular charge transfer interaction in addition to improving their optical properties. The absorption and emission properties of these derivatives were determined in order to gain an insight into the intensity of this type of interaction, their aggregation behavior and compare them with results obtained through quantum chemical calculations. Both compounds presented high photochemical stability in THF, and the linear spectroscopic characterization revealed high extinction coefficients, large fluorescence quantum yields and relatively low tendency of forming excimers in several …

Improvements On Instrumentation To Explore The Multidimensionality Of Luminescence Spectroscopy, Anthony Moore

Electronic Theses and Dissertations

This dissertation presents experimental and instrumentation developments that take full advantage of the multidimensional nature of line narrowing spectroscopy at liquid nitrogen (77 K) and liquid helium (4.2 K) temperatures. The inconvenience of sample freezing procedures is eliminated with the aid of cryogenic fiber optic probes. Rapid collection of multidimensional data formats such as wavelength time matrices, excitation emission matrices, time-resolved excitation emission matrices and time resolved excitation emission cubes is made possible with the combination of a pulsed tunable dye laser, a spectrograph and an intensifier-charged coupled device. These data formats provide unique opportunities for processing vibrational luminescence data …

Photogenerated O-Azaxylylenes: Mechanistic Studies And Synthetic Applications, William Cole Cronk

Electronic Theses and Dissertations

This research sets out to build upon excited state o-azaxylylene cycloaddition. The mechanism behind the excitation and cycloaddition process of photogenerated o-azaxylylenes was determined experimentally. Time-correlated single-photon counting, steady-state spectroscopy, triplet quenching experiments, and quantum yield studies provided evidence suggesting that excited state intramolecular proton transfer is followed by intersystem crossing and stepwise addition to the tethered unsaturated pendant.

In keeping with the principles of diversity oriented synthesis, a modular approach was taken to gain access to a diverse array of N,O,S-Polyheterocycles which were modified postphotochemically via Suzuki coupling to yield fused biaryls. Cycloaddition products, outfitted with halogens …

Efficient Utilization Of Solar Energy In Dye-Sensitized Solar Cells And In The Photocatalytic Reduction Of Carbon Dioxide, Aron Joel Huckaba

Electronic Theses and Dissertations

One of the most important questions humanity will face in the next 100 years is going to be "What will happen when oil runs out?" This dissertation describes efforts to utilize solar energy to improve renewable energy technology in two ways: First, through the improvement of dye sensitized solar cells by theimprovement of D-π-A dye subunits, the development of practical sensitizers, and progress towards stable, tunable redox shuttles. A novel indolizine donor subunit was synthesized that was shown to be the strongest reported donor. Dyes made from this novel donor and devices using the Γ-/I 3- reached up to 5.4% …

Fabrication And Study Of Graphene-Based Nanocomposites For Sensing And Energy Storage, Matthew Mcinnis

Electronic Theses and Dissertations

Graphite is an allotrope of carbon made up of atomically thin sheets, each covalently bound together, forming a π-conjugated network. An individual layer, called graphene, has extraordinary electrical, thermal and physical properties that provide the opportunity for innovating new functional composites. Graphene can be produced directly on a metallic substrate by chemical vapor deposition or by chemical oxidation of graphite, forming a stable aqueous suspension of graphene oxide (GO), which allows for convenient solution processing techniques. For the latter, after thermal or chemical reduction, much of the properties of the starting graphene re-emerge due to the reestablishment of π-conjugation. The …

Progress Toward The Total Synthesis Of The Natural Product Herbicide Ascaulitoxin Aglycone, Jeffery Brian Morgan

Electronic Theses and Dissertations

Ascaulitoxin aglycone is a structurally unique bis-amino acid isolated from the fungal species Ascochyta caulina, with herbicidal activity against Chenopodium album. Ascaulitoxin aglycone's potent herbicidal activity coupled with an unknown but novel mechanism of action makes it a perfect candidate for further study in the pursuit of new natural product herbicides. This dissertation research will illustrate three synthetic strategies towards the total synthesis of ascaulitoxin aglycone from chiral pool building blocks. Strategy 1 invokes the use of the Henry reaction as a key step for the construction of the central C4-C5 cis-aminohydroxy group, which was moderately successful, but abandoned in …

Accurate Computation Of Molecular Properties From Novel Applications Of Quantum Mechanical Wavefunction Methods, James Coleman Howard

Electronic Theses and Dissertations

High-accuracy quantum mechanical (qm) wavefunction methods have been applied to compute molecular properties of weakly-bound clusters. This work focuses on both extending the applicability of robust theoretical methods to larger systems and also determining the inherent accuracy of ab initio methods when compared to experimentally measured properties. Described here is the development of an efficient many-body approach that offers the ability to reduce both the time and the computational resources normally required to compute these properties reliably. The n-body:many-body qm:qm technique has been extended to compute harmonic vibrational frequencies of clusters. Applying this methodology to small hydrogen-bonded clusters demonstrates that …

Method Development For Mass Spectrometric Characterization Of Ultra-Small Nanomolecules And Mass Spectrometry Imaging Of Selected Biomolecules, Nuwan K. Kothalawala

Electronic Theses and Dissertations

High sensitivity, selectivity and remarkable identification capabilities facilitate the applicability of mass spectrometry (MS) in diverse fields. This dissertation outlines how this cutting edge technology is used to determine the chemical composition of the ultra-small nanomolecules (NMs) to atomic precision and obtain spatial resolution of selected biomolecules using mass spectrometry imaging (MSI). Chapter I includes introduction to electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) MS used in my PhD research. Chapter II explains how high resolution ESI-MS methods were developed to analyze the polar water-soluble NMs. These new methods express how ESI-MS parameters need to be optimized …

Effective Tuning Of Bimetallic Composition Of Gold-Copper Nanomolecules And The Emergence Of Plasmon-Like Feature In Optical Spectra, Asantha Champika Dharmaratne

Electronic Theses and Dissertations

Au144-xCux(SR)60 alloy nanomolecules were synthesized and characterized by using ESI-MS to atomic precision. A maximum of 23 copper atoms replace the gold atoms; when the number of copper atoms is higher than eight, a surface plasmon-like peak appears at ∼520 nm. Based on the fundamental, elemental properties of Au and Cu, we predict a mixed atomic ordering and incorporation into the Au12 and Au 42 shells of the proposed icosahedral structured model. Alloy nanomolecules reported here could have potential applications in the field of catalysis and optical sensors.

Mass Spectral Studies To Investigate Butylbenzene Fragmentation Pathway And Pyrolysis Products., Balasubramaniam Lingam

Electronic Theses and Dissertations

In this dissertation research, two fundamental studies involving gas chromatography mass spectrometry of n-butylbenzene and pyrolysis products are presented. In the first study, fragmentation pathways of n-butylbenzene in quadrupole ion trap have been investigated. At low energy, product ion corresponding to m/z 92 and m/z 91 are formed via competitive parallel dissociation. Studies have also shown that at higher energy m/z 92 has sufficient internal energy to undergo further fragmentation yielding m/z 91 via consecutive dissociation. Thus in order to discern the fragmentation pathways of n-butylbenzene, the technique of two-dimensional correlation spectroscopy (2DCOS) was applied to the mass spectral data. …

Development Of A Nano-Sensing Approach And A Portable Prototype For Real-Time Detection And Quantification Of Free Mercury In Stream-Flow: Combining Science And Engineering In Pro Of The Environment, Warinya Chemnasiri

Electronic Theses and Dissertations

Mercury (Hg) is a well-known hazardous environmental contaminant existing in several forms, but all are toxic to human in one way or the others. Since Hg usually settles into water polluting the environment and accumulating in living organisms, it is crucial to monitor Hg levels in the aquatic ecosystem. Although there are many well established techniques currently used to detect Hg, most of them require elaborate and time-consuming sample preparation and pre-concentration procedures, as well as costly and bulky equipment that limit their practical application in the field. In order to overcome the existent limitations in Hg determination methods, Hernandez …

Investigating New Guaiazulenes And Diketopyrropyrroles For Photonic Applications, Ebrahim Ghazvini Zadeh

Electronic Theses and Dissertations

?-Conjugated systems have been the focus of study in recent years in order to understand their charge transport and optical properties for use in organic electronic devices, fluorescence bioimaging, sensors, and 3D optical data storage (ODS), among others. As a result, several molecular building blocks have been designed, allowing new frontiers to be realized. While various successful building blocks have been fine-tuned at both the electronic and molecular structure level to provide advanced photophysical and optoelectronic characteristics, the azulene framework has been under-appreciated despite its unique electronic and optical properties. Among several attributes, azulenes are vibrant blue naturally occurring hydrocarbons …

Optimization Of Molecular Beacon-Based Multicomponent Probes For Analysis Of Nucleic Acids, Maria Stancescu

Electronic Theses and Dissertations

Detection of single nucleotide substitutions (SNS) in DNA and RNA has a growing importance in biology and medicine. One traditional approach for recognition of SNS takes advantage of hybridization probes that bind target nucleic acids followed by measuring ?Tm, the difference in melting temperatures of matched and mismatched hybrids. The approach enables SNS differentiation at elevated temperatures (usually 40-65oC) often only in a narrow range of < 10oC and requires high-resolution melting devices. Here we demonstrate that a specially designed DNA probe (X sensor) can broaden ?Tm from ~10oC to ~16oC and distinguish SNS in the interval of ~5-40oC. Therefore, there is no need for heating or measuring Tm for accurate SNS differentiation. Our data indicate that this wide differentiation range is in part due to the non-equilibrium hybridization conditions. Further we explored the idea that it is possible to improve the performance of an X sensor operable in close to equilibrium conditions by shifting its operability to non-equilibrium conditions. One way to achieve this is to introduce as many as possible structured ligands in analyte's dissociated state. Here we show that by introducing the maximum possible conformational constraints in X probe it is possible to shift its operation to non-equilibrium conditions and to improve its selectivity at temperatures < 15oC. Thus, this work points towards a new strategy for the design of highly selective hybridization sensors which operate in non-equilibrium conditions at close to room temperature. The X sensors could be utilized in qPCR, microarrays, as well as RNA analysis in living cells and for ambient temperature point-of-care diagnostics. In the last part of this work, X sensors were used in real time detection of PCR products. The sensors were optimized to operate in PCR buffer with optimal Mg2+ concentration. They were able to detect the target amplicon together with nonspecific products. The results presented here suggest that X sensors might be adopted for real time PCR format.

Strategies For Enhanced Genetic Analysis Of Trace Dna From Touch Dna Evidence And Household Dust, Katherine Farash

Electronic Theses and Dissertations

In forensic casework it is often necessary to obtain genetic profiles from crime scene samples that contain increasingly smaller amounts of genetic material, called Low Template DNA (LTDNA). Two examples of LTDNA sources are touch DNA evidence and dust bunnies. Touch DNA refers to DNA that is left behind through casual contact of a donor with an object or another person. Touch DNA can be used to prove a suspect was present at a crime scene. Dust bunnies, or dust conglomerates, typically contain trapped shed skin cells of anyone in the vicinity along with fibers, dirt, hair, and other trace …

Photophysics Of Organic Probes And Their Applications In Bioimaging & Photodynamic Therapy, Bosung Kim

Electronic Theses and Dissertations

Over the past several decades the phenomenon of luminescence (divided into fluorescence and phosphorescence) has received great attention in the field of biological science. This quest has motivated scientists for a variety of applications, including fluorescence imaging. Fluorescence microscopy techniques that provide unique advantages, such as high spatial resolution and superior sensitivity, have been regarded as attractive tools in biophotonics. With the progress of ultrafast laser sources, two-photon absorption (2PA), in which a molecule absorbs two photons simultaneously, has opened possibilities of using it for various applications. Two-photon fluorescence microscopy (2PFM), which affords deeper tissue penetration and excellent three-dimensional (3D) …

Structure-Property Relationship Of The Two-Photon Circular Dichroism Of Compounds With Axial And Helical Chirality, Carlos Diaz

Electronic Theses and Dissertations

Back in 1894 Lord Kelvin coined the term "chiral" in order to refer to molecules whose mirror images were not superimposable with themselves. Over the years, research has demonstrated the important role that chiral molecules play in life, chemistry, and biology as well as their importance in the development of new drugs and technologies. The efforts to understand chiral systems have been mainly driven by spectroscopic methods that leverage on the opposite responses that enantiomers have to linear or circularly polarized light of both handedness. More specifically, Electronic Circular Dichroism (ECD) which measures the differences in linear absorption of left …

The Spectroscopic Characterization Of Newly Developed Emissive Materials And The Effects Of Environment On Their Photophysical Properties, Louis Edward Mcnamara

Electronic Theses and Dissertations

The development of new materials capable of efficient charge transfer and energy storage has become increasingly important in many areas of modern chemical research. This is especially true for the development of emissive optoelectronic devices and in the field of solar to electric energy conversion. The characterization of the photophysical properties of new molecular systems for these applications has become critical in the design and development of these materials. Many molecular building blocks have been developed and understanding the properties of these molecules at a fundamental level is essential for their successful implementation and future engineering. This dissertation focuses on …

Gold Nanomolecules : Developing Synthetic Protocols, Characterization And Investigation Of Ligand Effects On Structure And Properties, Praneeth Reddy Nimmala

Electronic Theses and Dissertations

The term "Nano" in chemistry refers to particles/molecules in the size range 1 to 100 nm. Gold nanoparticles were used in ancient times in making decorative glass as they produce vibrant, size dependent, colors upon interaction with light. Gold is a preferred choice of metal for the synthesis of nanoparticles mainly due to its inertness to atmospheric conditions and most chemicals. Gold thiolate nanomolecules, which is the primary focus of this dissertation research, are chemical molecules with a fixed number of gold atoms and organo-thiolate ligands. They are of the form Aux(SR)y and possess molecule-like properties as a result of …

Synthetic Study Of Karlotoxins And Investigation Of Alpha-Diaminoboryl Carbanion Chemistry, Yusuke Takahashi

Electronic Theses and Dissertations

Karlotoxins (KmTxs), produced by a toxic marine/estuarine phytoplankton, the dinoflagellate Karlodinium veneficum, are known to be ichthyotoxic, thus being associated with numerous fish deaths events worldwide. They have also been reported to show a variety of biological activities such as hemolytic, cytotoxic, and anti-fungal activities. Recently, the Hamann group successfully assigned the absolute configurations of KmTx2, the first complete structure elucidation among the congeners. In a structural sense, karlotoxins are a family of linear polyketides with three distinctive regions; a bis-tetrahydropyran core fragment, a long, highly oxygenated carbon chain, and a lipophilic chlorodiene unit. Such potent biological activities as well …

Mercury Methylation Potentials In Sediments An Ancient Cypress Wetland Using Species-Specific Isotope Dilution-Gc-Icp-Ms: Analytical Method Development And The Effect Of Sorbent Amendments, Derek Davin Bussan

Electronic Theses and Dissertations

A novel method was developed to measure mercury (Hg) directly in environmental solids using inductively coupled plasma mass spectrometry (ICP-MS) with online sample ashing. The method combines a direct mercury analyzer (DMA) that is based on sample combustion, Hg pre-concentration by amalgamation with gold, and atomic absorption spectrometry (AAS), with a high resolution ICP-MS. Unlike AAS, the ICP-MS is capable of individual isotope measurements allowing for accurate quantitation by isotope dilution mass spectrometry (IDMS) and for isotope tracer experiments. The method was validated using certified reference materials including sediment (NIST 2709), leaves (NIST 1547), and fish-muscle (DORM-3), with recoveries within …

Exploration Of Novel Synthetic Utility Of Lithioacetonitirile, Rambabu Sankranti

Electronic Theses and Dissertations

No abstract provided.

Aggregation Of Squaraine Dye Derivatives In Solid State Spin-Coated Thin Films, Mohammed Daoudi

Electronic Theses and Dissertations

Squaraine dyes have been the subject of intensive studies due their unusual electronic properties that make them good candidates for a wide range of applications in various technological fields. They are particularly promising in nonlinear optics, bioimaging for labeling and sensing of biomolecules, as sensitizers for solar energy harvesting in solar cells and organic photovoltaics, two-photon absorbing materials, near-infrared (NIR) emitting fluorescent probes, second harmonic generation organic dyes, and sensitizers for photodynamic therapy among others. In this dissertation, the aggregation behaviors and features of several squaraine dye derivatives in solid state thin films were studied and reported. In the first …

Chemical Analysis, Databasing, And Statistical Analysis Of Smokeless Powders For Forensic Application, Dana-Marie Dennis

Electronic Theses and Dissertations

Smokeless powders are a set of energetic materials, known as low explosives, which are typically utilized for reloading ammunition. There are three types which differ in their primary energetic materials; where single base powders contain nitrocellulose as their primary energetic material, double and triple base powders contain nitroglycerin in addition to nitrocellulose, and triple base powders also contain nitroguanidine. Additional organic compounds, while not proprietary to specific manufacturers, are added to the powders in varied ratios during the manufacturing process to optimize the ballistic performance of the powders. The additional compounds function as stabilizers, plasticizers, flash suppressants, deterrents, and opacifiers. …

Synthesis Of Fluorene-Based Derivatives, Characterization Of Optical Properties And Their Applications In Two-Photon Fluorescence Imaging And Photocatalysis, Grace Githaiga

Electronic Theses and Dissertations

The two-photon absorption (2PA) phenomenon has attracted attention from various fields ranging from chemistry and biology to optics and engineering. Two of the common NLO applications in which organic materials have been used are three-dimensional (3D) fluorescence imaging and optical power limiting. Two-photon absorbing materials are, therefore, in great demand to meet the needs of emerging technologies. Organic molecules show great promise to meet this need as they can be customized through molecular engineering, and as the development of two-photon materials that suit practical application intensifies, so does research to meet this need. However, there remains some uncertainty in the …

Quantum Chemical Studies For The Engineering Of Metal Organic Materials, Hector Javier Rivera Jacquez

Electronic Theses and Dissertations

Metal Organic Materials (MOM) are composed of transition metal ions as connectors and organic ligands as linkers. MOMs have been found to have high porosity, catalytic, and optical properties. Here we study the gas adsorption, color change, and non-linear optical properties of MOMs. These properties can be predicted using theoretical methods, and the results may provide experimentalists with guidance for rational design and engineering of novel MOMs. The theory levels used include semi-empirical quantum mechanical calculations with the PM7 Hamiltonian and, Density Functional Theory (DFT) to predict the geometry and electronic structure of the ground state, and Time Dependent DFT …

Folate Conjugated Hyperbranched Polyester Nanoparticles For Prostate Tumor-Targeted Delivery Of A Cytotoxic Peptide Via Prostate Specific Membrane Antigen, Orielyz Flores-Fernandez

Electronic Theses and Dissertations

Prostate Cancer is the second most deadly cancer in men, after lung cancer. The need for new and effective therapeutics that can constrain prostate cancer progression are challenged by the lack of suitable delivery strategies that target prostate cancer tissue. To study CT20p as potential chemotherapeutic agent in the treatment of prostate cancer we proposed the use of targetable hyperbranched polyester (HBPE) based nanoparticles as delivery system. Folic acid was conjugated to the nanocarrier to improve the selectivity of the nanoparticle towards specific cell surface targets in prostate cancer cell lines. Specifically we evaluated LNCaP that up-regulated the PSMA receptor. …

Aminooxy Reagents In Nanomedicine And Bioanalysis., Stephanie Mattingly

Electronic Theses and Dissertations

The development of nanomaterials as medical diagnostic and therapeutic agents is a rapidly expanding field. A brief search of the literature revealed that roughly half of all articles related to nanoparticle-based drug delivery were published after the onset of this thesis research, over the past 4 years. A few nano-based formulations have entered into clinical use, including liposomal drug formulations, protein-linked drugs, and nanoparticle-based MRI contrast agents. The chemistry that enables conjugation of a functional cargo, whether a drug, a targeting element, or a radionucleotide, to a nanocarrier is thus a critical component for development. Oximation is one of the …

Triggered Release Of Small Molecules From Solid Supports Using Heat Or An Applied Magnetic Field., Ralph Jacob Knipp

Electronic Theses and Dissertations

The reaction of an aminooxy moiety (RONH2) with an aldehyde or ketone carbonyl, an oximation reaction, results in the formation of robust oxime ether linkages. Oximation is a form of click chemistry and is chemoselective, occurs in a variety of solvents including water, and produces high yields with little to no purification. We were inspired to exploit the advantages of oximation reactions by attaching aminooxy-functionalized molecules to solid supports, thus allowing us to employ aminooxy chemistry in ways that cannot be achieved using solution phase. Chapter 1 provides a review of aminooxy chemistry, its advantages over similar reactions and its …