Doctor of Philosophy, Miami University, 2013, Chemistry and Biochemistry

This dissertation describes the development and application of methods and instrumentation for qualitative and quantitative sample analyses by infrared and Raman spectroscopies. An introduction to the concepts and methods utilized is provided in Chapter 1. A comparative evaluation of solid-core silver halide fiber optics and hollow silica waveguides was performed on the basis of the transmission of mid-infrared radiation using a fiber optic coupling accessory and an infrared microscope is presented in Chapter 2. Increased transmission was reproducibly observed between two identical hollow waveguides due to minimization of insertion and scattering losses resulting from the hollow core. Chapter 3 presents an evaluation of a mid-infrared, attenuated total (internal) reflection (ATR) probe accessory utilizing hollow waveguides based on transmission and signal-to-noise. Quantitative analyses of aqueous succinylcholine chloride and ethanol solutions were also performed. An in situ Raman study of nitrogen incorporation in thin films of zinc oxide using a temperature-controlled reaction cell is discussed in Chapter 4. Monitoring nitrogen incorporation in thin films of zinc oxide at elevated temperatures in the presence of nitrogen-containing precursor reagents proved inconclusive using the proposed method. Chapter 5 presents an evaluation of dispersive and Fourier transform (FT-) Raman spectroscopies for on-line process control in the bottling industry. FT-Raman was determined to be more applicable for on-line determinations of poly(ethylene terephthalate) bottle thickness due to the availabilities of such benefits as increased laser power and fluorescence rejection. Preliminary data from the development of an inverted ATR imaging microscope are discussed in Chapter 6. The inverted optical design of the microscope permits simultaneous viewing of the sample with white light and the collection of infrared spectral images. Summaries of the presented research are pro (open full item for complete abstract)

Committee: André Sommer PhD (Advisor); Neil Danielson PhD (Committee Chair); Jonathan Scaffidi PhD (Committee Member); David Oertel PhD (Committee Member); Lei Kerr PhD (Committee Member) Subjects: Analytical Chemistry; Chemistry

Master of Science, University of Akron, 2006, Physics

Metal oxide nanofibers have potential applications in filtration, catalysis, energy conversion, and other areas. The most popular techniques for the characterization of nanofibers are X-ray diffraction (XRD) and scanning electron microscopy (SEM). However, these methods need to be supplemented with surface sensitive spectroscopies for more complete characterization. In several metal oxide nanofiber systems, unexpected impurities were found which may have a significant influence on the structure and surface chemistry. These impurities are not usually detectable with XRD and SEM. The main spectroscopic methods used here for materials characterization are X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Additionally, two relatively uncommon yet powerful techniques, photoacoustic FTIR and infrared emission spectroscopy are also used. These spectroscopic methods have provided insight into some of the unusual properties of metal oxide nanofibers. With the aid of surface sensitive spectroscopies, further development of these interesting materials will be enabled.

Committee: Rex Ramsier (Advisor) Subjects:

Master of Science, The Ohio State University, 2008, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2008, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2008, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, The Ohio State University, 2024, Chemistry

Understanding the fundamental interactions within and at the surface of atmospheric aerosol is of the utmost importance as they drive the properties of aerosol that influence global climate and public health. The first work presented herein explores the highly perturbed structure of water within systems inspired by phase separated organic aerosol. An approach is taken that combines polarized Raman spectroscopy and molecular dynamics to reveal the structural changes that occur as water is added incrementally to propylene carbonate (PC), a polar, aprotic solvent that is relevant in the environment and in electrochemical systems. Polarized Raman spectra of PC solutions were collected for water mole fractions 0.003 ≤ Χwater ≤ 0.296, which encompasses the solubility range of water in PC. The novel approach taken to the study of water-in-PC mixtures herein provides additional hydrogen bond and solvation characterization of this system that has not been achieveable in previous studies. Analysis of the polarized carbonyl Raman band in conjunction with simulations demonstrated that the bulk structure of the solvent remained unperturbed upon the addition of water. Experimental spectra in the O-H stretching region were decomposed through Gaussian fitting into sub-bands and studies on dilute HOD in H2O. With the aid of simulations, we identified these different bands as water arrangements having different degrees of hydrogen bonding. The observed water structure within PC indicates that water tends to self-aggregate, forming a hydrogen bond network that is distinctly different from the bulk and dependent on concentration. For example, at moderate concentrations, the most likely aggregate structures are chains of water molecules, each with two hydrogen bonds on average. The interaction of NO2 with organic interfaces is critical in atmospheric processing of marine and continental aerosol as well as in the development of NO2 sensing and trapping technologies. Recen (open full item for complete abstract)

Committee: Heather Allen (Advisor); Zachary Schultz (Committee Member); Bern Kohler (Committee Member) Subjects: Chemistry; Physical Chemistry

Doctor of Philosophy, The Ohio State University, 2024, Chemistry

Damaging UV radiation from the sun can lead to the formation of mutagenic photoproducts. The fate of initial electronic excited states in both DNA nucleobases and double-stranded DNA has been of considerable interest over the last few decades. Despite the progress that has been made in understanding the mechanisms for electronic deactivation, there has been considerably less effort placed on understanding the mechanisms for vibrational cooling following ultrafast electronic deactivation, in large part due to complex and competing pathways for vibrational relaxation. In this thesis, I present the ultrafast vibrational relaxation dynamics of a series of methylated nucleobase derivatives. By systematically varying the number of hydrogen bond donor and acceptor groups, the role of both the chemical modification and the solvent dependent relaxation dynamics were uncovered. In all of the molecules studied, the nearly isoenergetic carbonyl and ring modes decay were found to decay with very different initial dynamics. This discrepancy was attributed to differences in intramolecular relaxation pathways due to differences in mode-specific couplings, rather than differences in the density of accessible states. Despite very different initial dynamics, both the ring and carbonyl modes thermalized with a shared, global time constant. One of the most intriguing observations is that this rate limiting relaxation step mirrors that found following electronic deactivation, despite more than an order of magnitude difference in excitation energies. In combination with experimental studies, theoretical modeling was used to resolve spectroscopic signatures of vibrational relaxation. Together, these results should play an important role in the development of future studies of vibrational relaxation dynamics.

Committee: Bern Kohler (Advisor); Alexander Sokolov (Committee Member); Christopher Jaroniec (Committee Member) Subjects: Physical Chemistry

Doctor of Philosophy (PhD), Wright State University, 2021, Engineering PhD

Measuring cerebral blood flow (CBF) is a crucial element in monitoring a vast variety of human brain disorders. Current imaging modalities used for measuring CBF has various limitations that restricts its usefulness especially in the neuroscience intensive care unit (NSICU). Here, the use of Time-gated DCS (TG-DCS) which has significant advantages compared to its predecessor, CW-DCS, was proposed as the solution. However, this technology is still in its infancy and its clinical capability has yet to be established. To show the feasibility of deploying TG-DCS in NSICU settings, the time-domain analytical model for TG-DCS was expanded for multi-layered cases. Next, CW-DCS was validated in humans and in NSICU settings on patients suffering from Traumatic Brain Injury (TBI). A prototype 1064nm TG-DCS system was built and validated on several in-vivo experiments. Finally, the feasibility of the system was shown by deploying it in NSICU settings for measuring CBF in TBI patients. Lastly, deep learning was used to show the feasibility of obtaining real-time results.

Committee: Ulas Sunar Ph.D. (Advisor); Sherif Elbasiouny Ph.D. (Committee Member); Robert Lober M.D., Ph.D. (Committee Member); Brandon Foreman M.D. (Committee Member); Jonathan Lovell Ph.D. (Committee Member) Subjects: Artificial Intelligence; Biomedical Engineering; Biomedical Research; Biophysics; Medical Imaging; Neurosciences; Optics

Master of Science, The Ohio State University, 2020, Aero/Astro Engineering

Non-self-sustained hybrid plasmas are formed by the overlap of two separate voltage waveforms with significantly different reduced electric field values (E/N), one of them below the ionization threshold, to produce excited species and radicals selectively. In this work, a stable, capacitively coupled ns pulse – RF waveform hybrid discharge is operated in nitrogen and mixtures of nitrogen with other molecular gases at 50 – 100 Torr pressure, using a single pair of electrodes mounted externally to the reactor cell. The purpose of the ns pulse discharge is to generate ionization and electronic excitation of the mixture components, while the below-breakdown RF voltage couples additional energy to the vibrational modes of the mixture components. Based on the broadband plasma emission imaging, the plasma volume appears to be enhanced by the RF waveform, compared to ns pulse discharge, due to the drift oscillations of electrons induced by the RF waveform. Coherent Anti-Stokes Raman Spectroscopy (CARS) measurements in the hybrid discharge operated in nitrogen show that the RF waveform significantly enhances the vibrational excitation of N2 in the ground electronic state, populating vibrational levels up to at least v=3, and increasing the vibrational temperature of N2 from TV = 1210 ± 110 K in the ns pulse train plasma to TV = 1810 ± 170 K in the ns-RF hybrid discharge. The translational- rotational temperature at these conditions remains low, TR = 315 ± 15 K. To evaluate the potential of this plasma to operate in other gas mixtures, 1% of H2 is added to nitrogen. CARS measurements reveal a moderate N2 vibrational relaxation by hydrogen, reducing the vibrational temperature in the hybrid plasma to TV = 1700 ± 150 K and increasing in the translational-rotational temperature to TR = 396 ± 10 K. Time-resolved measurements of the number density of the first electronically excited state of nitrogen, N2(A3Σ), obtained using Tunable Diode Laser Absorption Spectroscopy (TDLAS) in n (open full item for complete abstract)

Committee: Igor Adamovich (Advisor); Jeffrey Sutton (Committee Member) Subjects: Chemistry; Energy; Engineering; Environmental Engineering

Doctor of Philosophy, University of Toledo, 2020, Physics

We present the results of two near-infrared spectroscopic studies of ultracool dwarfs. The first utilizes low-resolution spectroscopy to follow-up discoveries from an all-sky proper motion survey conducted using multi-epoch data from the Wide-field Infrared Survey Explorer. Using the data from NEOWISE, along with the AllWISE catalog, Schneider et al. 2016 conducted an all-sky proper motion survey to search for nearby objects with high proper motions. We present follow-up spectra of 65 of their discoveries, focusing on potentially nearby objects (d < 25 pc), candidate late-type brown dwarfs (> L7), and subdwarf candidates. We found 31 new M dwarfs, 18 new L dwarfs, and 11 new T dwarfs. Of these, 13 are subdwarfs, including one new sdL1 and two new sdL7s. Eleven of these discoveries, with spectral types ranging from M7 to T7 (including one subdwarf) are predicted to be within 25 pc, adding to the number of known objects in the solar neighborhood. The second project presents the first high-resolution (R ~ 45,000) H- and K-band spectral sequence of ultracool dwarfs with spectral types ranging from M1.5 V to T6, including known low-gravity objects at six spectral types (M9, L0, L1, L2, L3, L5). All spectra were obtained using the Immersion Grating INfrared Spectrometer (IGRINS) at a resolving power of R ~ 45,000. We compared 22 of our objects to synthetic spectra created from the atmospheric models of Saumon and Marley 2008, fitting both the whole K-band (2.05--2.35 μm) and the CO band (2.27--2.35 μm) and obtained values of Teff, log g, vsini, vrad, and fsed for each of our objects from both sets of fits. When comparing these values with expected trends from the literature, we find some agreement, and some discrepancies. In particular we find that our Teff values are high compared to values calculated using bolometric luminosities, and our vsini values are high compared to previously published values for the same objects. Comparing the log g values for our field and low (open full item for complete abstract)

Committee: Michael C Cushing (Committee Chair); Jon Bjorkman (Committee Member); Rupali Chandar (Committee Member); Kathy Shan (Committee Member); Michael Line (Committee Member) Subjects: Astronomy; Astrophysics; Physics

Doctor of Philosophy, The Ohio State University, 2019, Food Science and Technology

Tomatoes are one of the most consumed vegetables throughout the world delivering important nutrients as a widely available and cost-effective option. When 2010 Dietary guidelines were released with an effort to increase vegetable consumption, tomatoes were moved from “other vegetables” subgroup to the newly created “red-orange vegetables” subgroup as a nutritionally dense, widely available and affordable vegetable option for a healthy diet. Domestication and breeding for yield, size, disease resistance caused unexpected negative consequences, and the lack of aroma and taste has become a major complaint among consumers of modern tomato varieties. The overall objective of this research was to develop rapid and effective methods based on vibrational spectroscopy to improve tomato breeding selections in terms of improving tomato taste and flavor as well as color and nutritionally important components of tomatoes. In the first chapter, a background and literature review are given on tomatoes and breeding. A comprehensive review is given on vibrational spectroscopy and applications in food industry, and two independent experimental studies are presented. The first study focused on development of a rapid technique based on infrared spectroscopy to use in field applications in order to improve the selection of new tomato varieties with desired levels of chemical traits which are related to tomato flavor and aroma. In this part of the study, predictive regression algorithms were developed using portable FTIR devices with different sampling approaches to find the best application to utilize in breeding industry. Multiple quality traits were simultaneously determined by using a single drop of sample providing fast (<1 min) measurements and minimal sample preparation based on unique spectral fingerprints. The prediction models were then validated successfully with external set of samples. The second part of study investigated the identification of major tomato carotenoids non (open full item for complete abstract)

Committee: Luis Rodriguez-Saona Dr (Advisor); Christopher Simons Dr (Committee Member); Monica Giusti Dr (Committee Member); Rafael Jimenez-Flores Dr (Committee Member); Jeff Hattey Dr (Other) Subjects: Food Science

BA, Oberlin College, 2017, Physics and Astronomy

In this thesis we provide an introduction to the use of Metal-Organic Frameworks (MOFs) for hydrogen storage and for the separation of hydrogen isotopologues, H2 and D2. MOFs are a class of materials comprised of `building-block' metal-oxide clusters connected by organic ligands, which have the capacity to adsorb molecules such as hydrogen through weak, physisorptive mechanisms. We provide some background on the quantum mechanical structure of hydrogen isotopologues, the structure of a few state-of-the-art MOFs, the quantum mechanics of infrared spectroscopy, and the desorption dynamics of adsorbates generally. We provide a description of the experimental apparatus and procedure used in this work to acquire thermal desorption (TD) and simultaneous, in situ infrared (IR) spectra. Notably, this apparatus makes use of a pressure gauge to record TD spectra—to the best of the author's knowledge, this is the first time such an apparatus has been created and shown to produce reproducible, physically-informative TD spectra. We demonstrate the potential of this novel spectroscopic technique on three MOFs, as we report their respective TDS and IR signatures. The agreement between our TDS and IR techniques is remarkable, as is the amount of information apparent in the TD spectra, and the agreement of our TD spectra with those in the literature. With our simple technique we are able to clearly distinguish the TD spectra of H2 and D2, allowing for the evaluation of MOFs with respect to their isotopologue separating ability. In addition to a proof of concept as to the proficiency of the experimental apparatus, this work presents two main findings: that the desorption of hydrogen isotopologues from MOFs does not follow the coverage-independent Polanyi-Wigner equation, and that stronger binding MOFs exhibit diminishing returns with respect to their ability to separate hydrogen isotopologues via temperature programming. As we argue on several occasions in this thesis, the TD s (open full item for complete abstract)

Committee: Stephen FitzGerald (Advisor) Subjects: Materials Science; Physical Chemistry; Physics; Quantum Physics

Doctor of Philosophy, The Ohio State University, 1986, Graduate School

Committee: Not Provided (Other) Subjects: Physics

Doctor of Philosophy, The Ohio State University, 2016, Chemistry

Sea spray aerosols (SSA) impact Earth's climate directly and indirectly by scattering and absorbing solar radiation and influencing cloud formation, respectively. SSA are formed through the wind-drive wave action at the ocean surface, and their chemical composition is impacted by the biological activity in the sea surface microlayer (SSML), the thin organic layer present at the air-ocean interface. Physical and optical properties of SSA are influenced by the structure and organization of their surfaces. Organic films are known to form at the surface of SSA, and therefore a molecular-level understanding of the organic species that make up these films and their subsequent impact on interfacial properties is necessary to gain insight into climate change. In this dissertation Langmuir monolayers are utilized as proxies for organic-coated SSA. Phase behavior, rigidity, and stability of monolayers are assessed with surface pressure-area isotherms. Surface morphology of monolayers was imaged with Brewster angle microscopy (BAM). Infrared reflection-absorption spectroscopy (IRRAS) and vibrational sum frequency generation (VSFG) spectroscopy were used to examine the molecular-level structure and intermolecular interactions of the monolayers. VSFG was additionally used to probe the organization and structure of water molecules in the interfacial region. As SSA are chemically complex, several different types of atmospherically-relevant lipid-aqueous interfaces are investigated. The effect of ion enrichment for marine-relevant cations (Na+, Mg2+, Ca2+, and K+) on the interfacial properties of the phospholipid dipalmitoylphosphatidylcholine (DPPC) was investigated. All cations were found to impact monolayer properties, with divalent cations having a greater effect than monovalent ions. Refractive index of the monolayer was found to decrease with increasing cation concentration. In the case of Ca2+, significant dehydration of the phosphate headgroup was observed. Bindin (open full item for complete abstract)

Committee: Heather Allen (Advisor) Subjects: Chemistry

PhD, University of Cincinnati, 2001, Engineering : Materials Science

The molecular structures of the adhesive/a-SiO 2 and a-SiO 2 /metal interfaces were investigated for plasma polymerized a-SiO 2 films that were used as adhesive primers on metal substrates. Since these interfaces were buried and difficult to observe it was necessary to develop special sample preparation techniques. For the adhesive/primer interface, a low molecular weight molecule that modeled the chemical properties of epoxy adhesives was applied to the surface of the primer film for chemical interaction. The chemical interactions between the adsorbed model compound and the a-SiO 2 film were monitored using surface analytical techniques. It was determined that chemical adsorption of the model adhesive occurred via amine protonation by acidic silanol groups on the a-SiO 2 primer surface. The interaction strength was tested by heating the adsorbate in ultra-high vacuum beyond the temperature necessary to desorb molecules that had adsorbed by hydrogen bonding. It was found that desorption did not occur, in support of chemisorption by forming the strongly bonded protonated amine. This indicated that reactions between the amine groups of the epoxy and the silanol groups of a-SiO 2 primer film impeded destabilization of the interface by moisture. In order to study the a-SiO 2 /metal interface, a-SiO 2 films were deposited onto metal substrates by plasma polymerization using novel plasma reactors designed for in-situ characterization with X-ray photoelectron spectroscopy and reflection-absorption infrared spectroscopy. These complimentary analytical techniques were used to analyze ultra-thin films without contamination from atmospheric exposure. By analyzing successively thinner films, the intensity of signals due to the bulk were reduced and the signals due to the interface were analyzed. This work showed that during the creation of the a-SiO 2 /metal-oxide interface, specific chemical bonds were formed, which promoted the overall mechanical strength and durability of th (open full item for complete abstract)

Committee: Dr. F. James Boerio (Advisor) Subjects: Engineering, Materials Science

MS, University of Cincinnati, 2005, Engineering : Materials Science

Interactions occurring at the interface between injection molded poly (vinyl chloride) (PVC) and steel substrates that were coated with thin films of aminosilanes were investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The silane films were formed by adsorption of γ-aminopropyltriethoxysilane (γ-APS) or N-(2-aminoethyl-3-aminopropyl) trimethoxysilane (γ-AEAPS) from 2% aqueous solutions onto polished steel substrates. PVC was injection molded onto the silane primed steel substrates and annealed at temperatures up to 170°C for times as long as 30 minutes. PVC was peeled off of the primed steel substrates using a 90° peel test and the substrate failure surfaces were thoroughly rinsed with tetrahydrofuran (THF) and distilled water to remove PVC and other compounds that were not strongly bonded to the substrates. The PVC failure surfaces were characterized by attenuated total reflection infrared spectroscopy (ATR) while PVC rinsed off of the substrate failure surfaces was characterized by transmission infrared spectroscopy. The resulting transmission and ATR spectra showed an absorption band near 1650 cm-1 that was attributed to unsaturation in PVC. The substrate failure surfaces were characterized by XPS; curve-fitting of N(1s) and Cl(2p) high resolution spectra showed the formation of amine hydrochloride complexes by protonation of amino groups of the silanes with HCl that was liberated from PVC during the onset of thermal dehydrochlorination. Furthermore, quaternization or nucleophilic substitution of labile pendent allylic chloride groups by amino groups on the silanes took place, thus grafting PVC onto the aminosilanes. It was determined that PVC having β-chloroallyl groupings along its chains showed better adhesion with steel primed with aminosilanes and that generation of allylic chloride groups in PVC chains was the rate limiting step in the reaction between PVC and aminosilane. The effect of crosslinking of (open full item for complete abstract)

Committee: Dr. James Boerio (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2011, Chemistry

Molecule based electronics and devices are an increasingly popular area of research in chemistry. These molecular-based devices largely rely on the separation of charge from (solar cell, LED) or movement of charge through (wires) a molecular unit. Largely, it is desirable for these materials to be easily fabricated, absorb throughout the visible/NIR spectrum or emit certain wavelengths. Organic systems generally provide good fabrication properties while the incorporation of metals can provide more easily tunable physical properties. Metallo-organic paddlewheel compounds involving quadruple bonds have previously been made into soluble, linear polymers with tunable absorption and have been incorporated into an LED to show electroluminescence. In terms of device performance, it is important to know how well charge can be expected to flow through the material. In devices that rely upon photon absorption, charge transport ability is dependent on charge delocalization and rates of transport. As a first step in these regards a series of complexes which represent simple monomeric analogs to the individual repeating units of the polymer have been studied. They serve as model complexes to the polymeric and a better understanding of their fundamental properties should relate to better design of polymeric materials. This dissertation uses both electronic and vibrational spectroscopies to characterize photoexcited states, determine their lifetimes, and evaluate the electronic delocalization within these states. Theoretical calculations also supported the results. Four molecules constitute limiting cases across a wide set of properties and are the focus of this work. Chapters 2 describes the molecules M2(O2CTiPB)2(O2C-C6H4-C≡N)2 (2a and 2b) and 3 describes the molecules M2(O2CCH3)2(NiPr)2C-C≡C-C6H5]2 (3a and 3b), where M = Mo (a) or W (b), each focusing on results from electronic spectroscopy. In particular, assignments for the photophysical excited states were made as well as s (open full item for complete abstract)

Committee: Malcolm Chiholm Prof. (Advisor); Terry Gustafson Prof. (Advisor); Claudia Turro Prof. (Committee Member) Subjects: Chemistry

Doctor of Philosophy, The Ohio State University, 2008, Chemistry

Exposure to UV light, particularly from the sun, is the primary controllable risk factor for the development of skin cancer. The damaging effects of UV photons results from their ability to induced photochemistry in DNA bases. While the many possible photoproducts of DNA are well known, the formation mechanisms for these photoproducts are not. In order to better understand these processes, we seek to better understand the events that occur between photon absorption and photoproduct formation - the photophysics of DNA. Femtosecond UV pump/UV probe transient absorption spectroscopy was used to study the ground-state vibrational cooling of the DNA base derivative 9-methyladenine (9MA) in solution. Photoexcitation of 9MA to the lowest bright electronic excited state at 267 nm is followed by rapid (τ ≈ 0.4 ps) internal conversion to the electronic ground state, generating more than 30 000 1/cm of excess vibrational energy. Transfer of this excess vibrational energy to the solvent was monitored via changes in the ground-state electronic absorption band at 250 and 285 nm. The vibrational cooling time increases in H2O (2.4 ps), D2O (4.2 ps), methanol (4.5 ps) and acetonitrile (13.1 ps) solvents. The studies show that the initial vibrational energy transfer from the hot solute molecule to the first solvent shell determined the thermalization rate. The studies also suggest that energy transfer between high-frequency solute and solvent modes play a more important role in vibrational cooling than expected. While the majority of excitation lead to ultrafast internal conversion, in pyrimidine bases additional decay pathways exist involving long-lived, intermediate, 1nπ* and 3ππ* states. The 1nπ*, 1ππ*, 3ππ* and S0 states of single pyrimidine bases have strongly-overlapping electronic absorption spectra which complicates study of their dynamics with conventional UV and visible techniques. A UV-pump/mid-IR-probe femtosecond transient absorption spectrometer was constructed for the (open full item for complete abstract)

Committee: Bern Kohler PhD (Advisor) Subjects: Chemistry; Physics

Master of Science (MS), Ohio University, 2007, Chemistry (Arts and Sciences)

The effect of singled-stranded DNA concentration, single-walled carbon nanotube (SWNT) concentration, DNA base pair length, and pH on SWNT dispersion was investigated to gain a better understanding of how DNA binds to SWNTs. Changes in the near-infrared absorbance and fluorescence spectra were used to determine these effects. At low DNA concentration, very little DNA was bound to the SWNTs leading to poor SWNT dispersion. At higher DNA concentration, more DNA was bound to the SWNTs achieving better dispersion. Increasing the DNA concentration and base pair length resulted in better SWNT dispersion as observed from the increasing structure and intensity in the near-infrared spectra. The opposite effect was observed by increasing the SWNT concentration. An equilibrium binding constant was calculated using the Langmuir model but resulted in an implausible value. Varying the pH of DNA/SWNT samples showed DNA to act similar to SDS as a surfactant except under very basic conditions where the fluorescence intensity diminished above pH 11 for the DNA dispersed samples.

Committee: Liwei Chen (Advisor) Subjects:

Doctor of Philosophy, Miami University, 2013, Chemistry and Biochemistry

The goal of the research performed for this thesis was to further develop and evaluate vibrational spectroscopic techniques, specifically infrared and Raman spectroscopies, in challenging sampling situations. Some experiments focused on analyzing samples with techniques that had limited to no previous research while others focused on modifying current techniques providing alternate and possibly improved methods of detection and analysis. Chapter 1 provides background into the fundamentals of infrared and Raman spectroscopy and briefly covers sampling techniques available. Chapter 2 demonstrates that a commercial Raman microscope can be externally modified to sample using attenuated total internal reflectance (ATR). This modification allowed the collection of nanometer thin films without spectral contamination from sub-layers and demonstrated improved collection parameters. Chapter 3 evaluated a constructed dispersive Raman spectrometer operating with near–infrared (NIR) wavelengths to determine polyethylene terephthalate film thickness for process monitoring purposes. Chapter 4 demonstrated the potential capabilities of NIR-diffuse reflectance spectroscopy for the detection of high energy materials to provide alternative methods of detection and increase safety in the battlefield. Chapter 5 was an investigation of a planar array spectrograph employed as a real-time detector for liquid chromatography separations.

Committee: André Sommer Dr. (Advisor); Neil Danielson Dr. (Committee Chair); Shouzhong Zou Dr. (Committee Member); David Oertel Dr. (Committee Member); Paul James Dr. (Committee Member) Subjects: Chemistry