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

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

Detecting, quantifying, and identifying flowing samples is imperative to many applications including pharmaceutical development and manufacturing, diagnostics, forensics, and environmental studies. Surface enhanced Raman spectroscopy (SERS) is a nondestructive, water insensitive, and highly sensitive method that can be applied to these areas. Raman spectroscopy provides information regarding molecular bonds based on the inelastic scattering of light. SERS increases the efficacy of Raman spectroscopy by utilizing plasmonic metal nanostructures to enhance signals by up to 108. Utilizing SERS detection for flowing solutions allows for minimal sample preparation, short analysis time, and sample recovery after analysis. This dissertation focuses on applying SERS in flow to low concentration samples to detect single molecules and analytes that are traditionally difficult to detect and differentiate. Chapter 1 introduces Raman and SERS as analytical tools and describes how these methods can be used for flow through analysis of both single molecules and sugars. Past literature of SERS in flow experiments and single molecule experiments are discussed to support the work shown in later chapters. Additional information regarding sugars, glycosylation, and chemometrics is provided. Chapter 2 focuses on a method for single molecule detection and quantification in flow. By utilizing fast acquisition SERS, a planar silver substrate, and chemometric analysis, the linear dynamic range of this technique is able to be lowered into the stochastic, or “event counting” regime instead of the traditional ensemble or “intensity based” regime. This allows for the limit of detection of Nile Blue A to be lowered by 16 times, and single molecules to be detected and counted. Chapter 3 discusses a method for detecting and differentiating monosaccharides in both flowing and static environments using a simple benchtop conjugation reaction, SERS detection, and chemometric methods for ana (open full item for complete abstract)

Committee: Zachary Schultz (Advisor); Christopher Fang-Yen (Committee Member); Robert Baker (Committee Member); Abraham Badu-Tawiah (Committee Member) Subjects: Analytical Chemistry; Chemistry

Doctor of Philosophy (Ph.D.), Bowling Green State University, 2016, Photochemical Sciences

This dissertation work investigated the parameters affecting the interfacial electron transfer (ET) dynamics in dye–semiconductor nanoparticles (NPs) system by using single-molecule fluorescence spectroscopy and imaging combined with electrochemistry. The influence of the molecule–substrate electronic coupling, the molecular structure, binding geometry on the surface and the molecule-attachment surface chemistry on interfacial charge transfer processes was studied on zinc porphyrin–TiO2 NP systems. The fluorescence blinking measurement on TiO2 NP demonstrated that electronic coupling regulates dynamics of charge transfer processes at the interface depending on the conformation of molecule on the surface. Moreover, semiconductor surface charge induced electronic coupling of molecule which is electrostatically adsorbed on the semiconductor surface also predominantly alters the ET dynamics. Furthermore, interfacial electric field and electron accepting state density dependent ET dynamics has been dissected in zinc porphyrin–TiO2 NP system by observing the single-molecule fluorescence blinking dynamics and fluorescence lifetime with and without applied bias. The significant difference in fluorescence fluctuation and lifetime suggested the modulation of charge transfer dynamics at the interface with external electric field perturbation. Quasi-continuous distribution of fluorescence intensity with applied negative potential was attributed to the faster charge recombination due to reduced density of electron accepting states. The driving force and electron accepting state density ET dependent dynamics has also been probed in zinc porphyrin–TiO2 NP and zinc porphyrin–indium tin oxide (ITO) systems. Study of a molecule adsorbed on two different semiconductors (ITO and TiO2), with large difference in electron densities and distinct driving forces, allows us to observe the changes in rates of back electron transfer process reflected by the suppressed fluorescence blin (open full item for complete abstract)

Committee: H. Peter Lu Dr. (Advisor); Yu Zhou Dr. (Other); Ksenija D. Glusac Dr. (Committee Member); Alexey T. Zayak Dr. (Committee Member) Subjects: Chemistry; Physical Chemistry; Physics

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

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

My dissertation research develops Raman spectroscopy-based sensors to measure aspects of human and plant health or disease states at the point of need, specifically in areas where current sensing methods are insufficient. The first main project area involves monitoring plant health, specifically soil ecology, in real time without harvesting the plant. Sensors are needed to non-invasively observe chemical changes expressed in plant leaves which result from nutrition conditions in the soil. These sensors would be especially useful to inform fertilization practices, increasing efficiency and sustainability. The second major project area focuses on developing a rapid and accurate diagnostic assay for COVID-19. The limitations of established testing methods, such as at-home antigen tests and polymerase chain reaction (PCR) assays, motivate the exploration of alternative techniques that do not sacrifice accuracy for speed. To tackle these sensing challenges, my research employs Raman spectroscopy, which uses light to probe the molecular composition of a sample. Each molecule has a unique Raman signature, and Raman signal is proportional to the concentration of molecules present in the sample, making the technique highly advantageous for identification and quantification. Raman signals can be collected quickly and non-destructively with minimal sample preparation. To detect low concentrations of analytes or poorly scattering analytes, we use surface enhanced Raman spectroscopy (SERS), a technique in which metal nanostructures amplify the Raman signals of the molecules near the nanostructures. Overall, this dissertation work focuses on optimizing portable Raman and SERS methods to non-invasively assess plant health and to detect COVID, all in a matter of seconds. Chapter 1 introduces the background and motivation for these projects, as well as the analytical techniques used to address them. Chapter 2 describes the development of handheld Raman techniques to monitor th (open full item for complete abstract)

Committee: Zachary Schultz (Advisor) Subjects: Analytical Chemistry; Chemistry

Doctor of Philosophy, The Ohio State University, 2020, Chemistry

We discuss the development and application of multiple methodologies which will either make the traditional electronic structure methods more efficient or reveal the structural insight of condensed or gas-phase systems. The main idea revolves around the development and application of \textit{ab initio} resonance-Raman (RR) spectroscopy and how to achieve the efficiency to simulate the resonance-Raman spectra for biomolecules. To tackle this, the first step was the development of new quadrature grids for high precision integration of modern density functionals, as the choice of density functional for RR simulation stems from the former's accuracy and cost-effectiveness. Our pruned integration grids, SG-2 and SG-3 work well for modern difficult-to-integrate functionals alongside finding a balance between accuracy and computational cost. To calculate the vibrational spectra for a biomolecule, getting the optimized structure is important as normal mode analysis can be erroneous at a non-stationary point. All quantum-mechanical optimization of enzyme active sites can be tricky geometric constraints that need to be introduced to prevent the structural collapse of the model system during geometry optimizations that do not contain a full protein backbone. We introduce a simple alternative in which terminal atoms of the model system are placed in soft harmonic confining potentials rather than being rigidly constrained. The new approach is more efficient for optimizing minima and transition states, as compared to the use of fixed-atom constraints, and also more robust against unwanted imaginary frequencies. To calculate the RR intensities using all-electron quantum chemistry, we used the excited state gradient method under the independent mode displaced harmonic oscillator (IMDHO) approximation. Using the RR spectroscopy we get insightful information about the structure of the hydrated electron, which caused a decade long debate. Furthermore, we have integrated the (open full item for complete abstract)

Committee: John Herbert Dr. (Advisor); Alexander Sokolov Dr. (Committee Member); Hannah Shafaat Dr. (Committee Member) Subjects: Chemistry; Physical Chemistry

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, 2022, Chemistry

The utilization of enzymes as bioelectrocatalysts is of increasing interest due to their advantages in chemical specificity and catalytic rates. Emphasis has been placed on hydrogen producing biocatalysts to overcome drawbacks of current heterogeneous catalysts, including limited availability and poor selectivity. Native enzymes, such as the [NiFe] hydrogenase, have demonstrated extreme proficiency as bi-directional catalysts for proton reduction and hydrogen oxidation, inspiring a variety of small molecule and protein mimics. The utilization of a robust and stable protein scaffold with a similar primary coordination environment as the native enzyme can result in similar activity. Previous reports have demonstrated that nickel-substituted rubredoxin (NiRd) serves as a structural, functional and mechanistic model of the [NiFe] hydrogenase, active towards proton reduction electrochemically and in solution, with an identical primary coordination sphere at the nickel center as the native enzyme. While the mechanism of proton reduction has been experimentally and computationally modeled to be similar to that of the native enzyme, key catalytic intermediates have not yet been isolated and characterized. This project aims to address some of the limitations of this current model, such as significant overpotential and lack of spectroscopic characterization of catalytically competent intermediates. Further, correlation between redox activity and protein structure are investigated by modification of the protein primary sphere coordination site. Primary sphere mutants demonstrate changes in the redox and catalytic behavior dependent on the cysteine site being modified. Drastic changes to the primary coordination sphere are explored using electrochemistry along with optical, multiwavelength resonance Raman, X-ray and electron paramagnetic resonance spectroscopies. This study demonstrates the ability to keep and shut off catalysis, aiding in the understanding of enzyme selectivit (open full item for complete abstract)

Committee: Hannah Shafaat (Advisor); Yiying Wu (Committee Member); Shiyu Zhang (Committee Member); Anne Co (Committee Member) Subjects: Chemistry

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 in Clinical-Bioanalytical Chemistry, Cleveland State University, 2019, College of Sciences and Health Professions

To better understand adaptive materials that respond to biological stimuli and to design synthetic systems that biomimetic, non-destructive and non-invasive approaches to monitor both the chemical and mechanical dynamics of the system are needed. Raman spectroscopy provides a chemical fingerprint spectrum with diffraction limited spatial resolution. Similarly, Brillouin spectroscopy can reveal properties of the sample's elasticity tensor allowing for the determination of a range of mechanical properties including the Young's modulus and Poisson's ratio. Brillouin scattered light undergoes a very small shift relative to Raman scattered light and requires a different wavelength discrimination device capable to spectrally resolve the subtle shifts typical of Brillouin spectra. Historically, this has been achieved using multiple Fabry-Perot interferometers either in tandem or cascaded which limits the optical throughput. Recently, the virtually imaged phased array (VIPA) spectral discriminator has been used to resolve the Brillouin spectrum in biological samples. The VIPA has a higher throughput than Fabry-Perot interferometers and accepts a line of incident illumination, thereby extending the Brillouin imaging possibilities to the line scanning modality. In the work presented here, a theoretical framework for VIPAs has been developed. In addition, a fully generalized dispersion equation has been developed using geometrical optics, which relates the input optical field to the VIPA response for both isotropic and anisotropic dielectrics. Hence, the dispersion relation is well suited for designing tunable VIPA elements that would enable high spectral resolution in a fixed image plane. In addition to the full theoretical description, two VIPA devices, one commercially produced and the other fabricated as part of this work, were characterized. A comparison between the theoretical predictions and the observed VIPA performance are presented.

Committee: John Turner II/Ph.D. (Committee Chair); Mekki Bayachou Ph.D. (Committee Member); Baochuan Guo Ph.D. (Committee Member); Xue-Long Sun Ph.D. (Committee Member); Andrew Resnick Ph.D. (Committee Member) Subjects: Analytical Chemistry; Optics; Polymer Chemistry; Scientific Imaging

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

Doctor of Philosophy (PhD), Ohio University, 2019, Physics and Astronomy (Arts and Sciences)

Quantum confinement of charge carriers in semiconductor nanostructures have garnered considerable attention in the past few decades. With new materials being discovered and advanced growth techniques allowing them to be engineered into nanoscale devices with atomic precision, the localization of charge carriers is becoming easier to control. The focus of this dissertation is to highlight the employed growth techniques and the characterization of the device structures studied in our lab.In the first project of the dissertation we examined the temporal dynamics of the Optically Generated Electric Field (OGEF) within a CQD device. We demonstrated the potential of using the interdot transition as a sensitive probe to measure electric fields by using photovoltaic band flattening in a Schottky diode structure. A modulated high energy laser was used to create the OGEF leading to photovoltaic band flattening. A CW laser with energy required to create the interdot transition was used to monitor the electric field in the device and characterize the temporal behavior of the field to determine rise time and decay time as well as to show how they depend on different variables.In the Second project we report on monolayer TMD metal semiconductor metal photodetectors produced using a CVD process. The photodetectors showed maximum responsivity of up to 15 A/W. The response time of the devices is found to be on the order of 1 µs, an order of magnitude faster than previous reports. The main project in this dissertation involved using the CVD growth technique employed in developing TMD devices to create deterministic single photon emitters (SPEs) by carrying out the growth on etched substrates. While we have seen successful growth with TMDs growing over perturbations, SPEs are yet to be found. However, in the process of developing these devices we were able to address several challenges in our technique.As highlighted in previous work in the group while the growth technique employed do (open full item for complete abstract)

Committee: Eric Stinaff Ph.D. (Advisor); Sergio Ulloa Ph.D. (Committee Member); David Tees Ph.D. (Committee Member); Wojciech Jadwisienczak Ph.D. (Committee Member) Subjects: Condensed Matter Physics; Physics; Solid State Physics

Doctor of Philosophy, The Ohio State University, 2017, Biophysics

Metalloproteins are essential to life, with roles in cellular signaling, metabolism, gas cycles, and gene regulation, among others. One group of metalloproteins is the ferritin-like superfamily, which contains a wide variety of members ranging from iron-trafficking proteins (ferritin) to enzymes that can perform 2-electron chemistry on hydrocarbons (bacterial multicomponent monooxygenases or BMMs). Ribonucleotide reductases (RNRs), one of the members of the ferritin-like superfamily, are enzymes that catalyze the only known de novo reduction of ribonucleotides to deoxyribonucleotides and are found is nearly every organism on earth. Recently, a novel protein was discovered in Mycobacterium tuberculosis called R2lox, because of its sequence similarity to the R2 subunit of RNR, whose function remains unknown. However, it does not possess any RNR activity and is more similar in active site structure and proposed function to the BMMs. This protein is very important from a basic science standpoint as well as a health science standpoint because of its unique metal-binding capabilities and because it is upregulated in the virulent H37rv strain of M. tuberculosis. To study the active site structure and oxygen activation reaction of this protein, a custom resonance Raman spectroscopic system was designed and built. This system is very versatile in that it can access many different wavelengths with a single laser, which is useful for resonance Raman, which relies on tuning the Raman excitation beam to an electronic absorption to enhance the scattering efficiency of Raman light. In addition to R2lox, this custom resonance Raman system has been used on numerous bioinorganic molecules to great effect. This work describes the design and construction of the custom resonance Raman system and its use in studying R2lox and other bioinorganic systems. Additionally, experiments were performed to lay the groundwork for studying electron transfer in R2lox via ruthenium modification.

Committee: Hannah Shafaat PhD (Advisor); James Cowan PhD (Committee Member); Terry Gustafson PhD (Committee Member); Marcos Sotomayor PhD (Committee Member) Subjects: Chemistry

Master of Science (MS), Wright State University, 2016, Chemistry

Vespucci is a software application developed for imaging and analysis of hyperspectral datasets. Vespucci offers several advantages over other software packages, including a simple user interface, no cost, and less restrictive licensing. Vespucci incorporates several analysis techniques including univariate imaging, principal components analysis, partial-least-squares regression, vertex components analysis and k- means clustering. Additionally, Vespucci can perform a number of useful data-processing operations, including filtering, normalization, baseline correction, and background subtraction. Datasets that consist of spatial or temporal data with a corresponding digital signal, including spectroscopic images, mass spectrometric images, and X-ray diffraction data can be processed in this software. The use of Vespucci in Raman and surface- enhanced Raman spectroscopies has been successfully demonstrated to examine the interaction of silver nanoparticles with corundum and Dengue virus virions. A manuscript detailing Vespucci has been published in the Journal of Open Research Software (http://openresearchsoftware.metajnl.com/articles/10.5334/jors.91/). More information about Vespucci will be available at http://vespucciproject.org.

Committee: Ioana Sizemore Ph.D. (Advisor); David Dolson Ph.D. (Committee Member); Michael Raymer Ph.D. (Committee Member) Subjects: Biology; Biomedical Engineering; Biomedical Research; Chemical Engineering; Chemistry; Environmental Science; Materials Science; Medical Imaging; Molecular Biology; Nanotechnology; Pharmacology; Physics; Physiology; Polymer Chemistry; Polymers; Remote Sensing; Scientific Imaging; Statistics; Toxicology; Virology

PhD, University of Cincinnati, 2016, Arts and Sciences: Physics

Strain distribution in the core and the shell of a semiconductor nanowire (NW) and its effect on band structures including carrier recombination dynamics of individual Wurtzite (WZ) In1-xGaxAs/InP and Zincblende (ZB) GaAs1-xSbx/InP strained core-shell NWs are investigated using room temperature Raman scattering and transient Rayleigh scattering (TRS) optical spectroscopy techniques. In addition, the electrical transport properties of individual ZB InP NWs are explored using gate-dependent current-voltage (I-V) measurements. Micro-Raman scattering from individual In1-xGaxAs NWs show InAs like TO and GaAs like TO modes with frequencies which are consistent with the 35% Ga concentration determined from the growth parameters. Calculations showed that the In0.65Ga0.35As core is under compressive strain of 0.26% while the InP shell is in tensile strain of 0.42% in In0.65Ga0.35As/InP NWs. TRS measurements of single NWs show clear evidence for a strong band resonance in the WZ In0.65Ga0.35As NW at 0.819 eV which is estimated to be a ~186 meV blue-shift with respect to bulk ZB In0.65Ga0.35As. Furthermore, both Raman scattering and TRS measurements are on excellent agreement with the band gap shift of In0.65Ga0.35As/InP core-shell NWs with respect to the core only NW by 46~48 meV which experimentally confirmed the InP shell induced compression of the core. The time decays of the resonance are observed to be long (~125 ps) for core-shell NWs while it is short (~31 ps) for core only NWs consistent with a larger nonradiative recombination rate. Optical phonon modes of GaAs1-xSbx are observed to be red-shifted with increasing Antimony fraction in GaAs1-xSbx NWs which can be expected in an alloy with increasing concentration of a heavier atom in the lattice. Using TRS measurements, the GaAs0.71Sb0.29 band gap for the core-shell NW is observed to be reduced by 0.04 eV with respect to the core only NW because of the tensile strain in the core. Raman experiments show a blue-shi (open full item for complete abstract)

Committee: Leigh Smith Ph.D. (Committee Chair); Carlos Bolech Ph.D. (Committee Member); Howard Everett Jackson Ph.D. (Committee Member); L.C.R. Wijewardhana Ph.D. (Committee Member) Subjects: Materials Science

PhD, University of Cincinnati, 2016, Arts and Sciences: Chemistry

This dissertation covers three areas which I have worked on while pursuing my degree. The first chapter includes an introduction of the work presented. The second and third chapters are devoted to design and synthesis a new class of nanoparticles and the related Surface-enhanced Raman Spectroscopy (SERS) and Surface-enhanced Fluorescence (SEF) investigation. Chapter two reported a new strategy to prepare a class of SERS-active nanoparticles with reporters embedded between Au-core/Ag-shell. These core-shell nanoparticles can find use as SERS-tags for Raman-based assay with strong SERS signals and good stability. In chapter three, by adjusting the spacing and the dye position between the core and the shell, we have successfully observed the simultaneous SEF and SERS from our Au-core/Ag-shell nanoparticles. The combination of SEF and SERS onto single nanoparticles is highly desirable to improve the accuracy and sensitivity in detection applications, which has drawn increasing attention in recent years to study the two effects on the same nanostructures. The chapter four covers the applications of previously developed SERS-active nanomaterials. Using the metal core-shell nanoparticles as the SERS substrates, we have successfully performed quantitative SERS measurements of three different types of analytes by embedding an internal reference between the Au core and Ag shell. This strategy provides great flexibility in the choice of the internal references and analytes, and also allows quantitative SERS measurements of the analytes in the solution.

Committee: Peng Zhang Ph.D. (Committee Chair); Bruce Ault Ph.D. (Committee Member); Hairong Guan Ph.D. (Committee Member) Subjects: Analytical Chemistry

Doctor of Philosophy, Miami University, 2015, Chemistry and Biochemistry

This dissertation describes five unique projects which advance spectroscopy in terms of education, technology and applications. Project goals were designed so the end results would assist with solving educational, military and industrial challenges through the use of spectroscopy. These goals were accomplished through the use of new, existing and adaptations of existing spectroscopic instrumentation. New spectroscopic instruments were developed and built for use in educational teaching laboratories at Miami University. These instruments included a low-cost Raman spectrograph and a low-cost flame atomic emission spectrometer. Both instruments have economic and educational benefits over commercial instruments and the flame emission instrument has already demonstrated its value in the classroom. The next project, driven by military interest, involved using near-infrared diffuse reflectance spectroscopy for the standoff detection of explosive materials on common surfaces. Projects included coating substrates with high energy materials and acquiring spectra from those coated substrates. Results showed differences in the detection limits for ammonium nitrate on various substrates, and these limits were directly dependent on the characteristics of the substrate. Another project was completed in collaboration with the United States Food and Drug Administration's Forensic Chemistry Center. This project's goal was to identify counterfeit goods based on their packaging materials. By taking a cross section of a packaging material and acquiring a high resolution attenuated total internal reflection (ATR) Fourier transform infrared (FTIR) image, differences could be revealed which showed variances between the authentic and counterfeit packaging materials. Finally, an adaptation of an ATR-FTIR microscope was used in an attempt to improve the spatial resolution of an ATR-FTIR image by working in a non-contact type sampling configuration. Improvements in spatial resolution have n (open full item for complete abstract)

Committee: Andre Sommer (Advisor); Neil Danielson (Committee Chair); Jonathan Scaffidi (Committee Member); Tom Cambron (Committee Member); Paul Urayama (Committee Member) Subjects: Chemistry

Doctor of Philosophy, University of Akron, 2014, Polymer Science

This study demonstrates the development of a stable anode for electrochemical oxidation of hydrocarbons in solid oxide fuel cell (SOFC) and a highly active TiO2 based catalyst for photocatalytic reactions. The Ni/YSZ anode of SOFC was modified by Cu electroless plating. The catalytic activity toward H2 and CH4 oxidation were compared by the Faraday resistance (RF) obtained from the impedance spectroscopy. The RF ratio of Cu-Ni/YSZ in CH4 to H2 was greater than that of Ni/YSZ, indicating low catalytic activity of Cu-Ni/YSZ toward CH4 oxidation. The addition of Cu decreased the catalytic activity, but increased stability to 138 h in dry CH4. Characterization of the carbon type with Raman spectroscopy and temperature programmed oxidation showed that Cu formed disordered carbon rather than graphitic carbon which is the precursor to coking. Addition of CO2 to CH4 was studied as another approach to prevent coking. Electrochemical performance and mass spectrometry of the reactor effluent showed that the CH4-CO2 SOFC generated electricity from CO and H2, products of dry reforming reaction, with CO as the major contributor to current generation. CH4-CO2 decreased the activation polarization but showed a limiting current due to the fuel depletion at the interlayer-electrolyte interface. Anode interlayer was modified by reducing the particle size to 2 µm. The fine microstructure increased the three phase boundary length and reduced the activation polarization. The pore loss in the fine microstructure resulted in diffusion limitation and a limiting current in CH4 which was eliminated by adding 4 wt% of pore former at interlayer. Further addition of pore former lowered the performance by creating discontinuity at electrolyte-interlayer interface. The photocatalytic oxidation of ethanol on TiO2 and TiO2 modified with Ag and Au nanoparticles was studied by in-situ IR spectroscopy. Au and Ag increased the surface hydroxyl groups, which further served as active specie (open full item for complete abstract)

Committee: Steven Chuang Dr (Advisor); Darrell Reneker Dr (Committee Member); Yu Zhu Dr (Committee Member); Xiong Gong Dr (Committee Member); Homero Castaneda-Lopez Dr (Committee Member) Subjects: Chemical Engineering; Energy

MS, University of Cincinnati, 2003, Engineering : Environmental Engineering

Room Temperature Ionic Liquids (RTILs) comprise a new generation of solvents, and their exceptional properties (i.e., non-volatility, non-flammability) promote them as alternative solvents in applications dominated by the well-known volatile organic compounds (VOCs). Although extensive literature exists for ionic liquid behavior as solvents and catalysts for numerous organic and inorganic reactions, their use for environmental applications is an unexplored area. Water immiscible RTILs were selected for investigation of ILs in environmental applications. Specifically, ILs were used as solvents for extracting organic contaminants from aqueous solutions. The higher affinity of the contaminants for ILs, instead of water, contributed to their removal from water and the minimization of the volume of the contaminated stream. Two ILs, 1-ethyl-3-methylimidazolium fluoroethylsulfonyl)imide, [emim]Beti, and 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim]PF 6 , were investigated as solvents for the extraction of chlorophenols from aqueous solutions. Partitioning of phenol, monochlorophenols, dichlorophenols, trichlorophenols, tetrachlorophenols, and pentachlorophenol was measured in both aqueous and ionic liquid phase using High Pressure Liquid Chromatography (HPLC) analysis. Extraction efficiency was found to be higher when [bmim]PF 6 was used and when the pH of the aqueous solution was at least one unit below the value of the dissociation constants (pK a ). In addition, partitioning, for both ILs, was increased as the number of chlorine atoms in the chlorophenol increased, displaying the same behavior as 1-octanol-water partition coefficient. Correlation between the distribution ratio of [emim]Beti-water or [bmim]PF 6 -water and the 1-octanol-water partition coefficient was calculated at 0.950 or 0.938, respectively. The effect of ionic strength on partitioning was also investigated, and showed no impact on the distribution ratio. Finally, the distribution ratio was n (open full item for complete abstract)

Committee: Dr. Dionysios Dionysiou (Advisor) Subjects: Engineering, Environmental

Doctor of Philosophy, The Ohio State University, 2007, Chemistry

The uptake and reaction of methanol at the air-liquid interface of 0-96.5 wt% sulfuric acid (SA) solutions has been observed directly using vibrational sum frequency generation spectroscopy (VSFG) and Raman spectroscopy. Evidence for the formation of methyl hydrogen sulfate (MHS) was obtained by the presence of a new peak in the 800 cm-1 region, not present in either the neat methanol or concentrated sulfuric acid spectra. This peak is attributed to the singly bonded OSO symmetric stretch of MHS. The maximum yield of MHS with a large SA excess is shown to be (95±5)% at –(15±2)°C. No evidence was found to suggest formation of dimethyl sulfate. As the concentration of SA increases from 0–96.5 wt%, the SFG spectra shift from that of methanol to that of methyl hydrogen sulfate. The surface is saturated with a mixture of the three methyl compounds after 15 minutes, although the relative amounts of MeOH, MeOH2+, and MHS vary with SA concentration. Uptake occurred on a much longer timescale, suggesting that uptake of methanol by sulfuric acid solutions is diffusion-limited. The diffusion coefficients for methanol into 0–96.5 wt% sulfuric acid solutions were measured by passing MeOH vapor in N2over the SA solutions and monitoring the uptake using Raman spectroscopy. The value obtained for methanol into water, D = (0.7±0.2) x 10-5cm2/s, is in agreement with values found in the literature. The values of D in 39.2-96.5 wt% SA range from (1–2.7) x 10-6cm2/s with the maximum value occurring for the 59.5 wt% SA solution. This may be due to the speciation of MeOH in the SA solutions or to speciation of the SA solutions. The organization of 1-butanol and 1-hexanol, at air-liquid interfaces was investigated using VSFG. There is evidence for centrosymmetric structures at the surface of pure butanol and hexanol. At most solution surfaces, butanol molecules organize in all-trans conformations. In contrast, the spectrum of 0.052 M butanol in 59.5 wt% sulfuric acid solution possesses a s (open full item for complete abstract)

Committee: Heather Allen (Advisor) Subjects: