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

MS, Kent State University, 2022, College of Arts and Sciences / Department of Chemistry and Biochemistry

Heterogeneous catalysts play an important role in modern society for fossil fuel processes, pollutant removals, biomass conversion, fertilizer products, etc. Nanoparticles are among the most important heterogeneous catalysts for many different chemical reactions due to their nanometer size and high surface-area-to-volume ratio. In this study, we use the single-molecule fluorescence microscopy (SMFM) approach to monitor and deepen our understanding of the catalytic behaviors of a widely used semiconductor, titanium dioxide, on gold nanorods (TiO2@AuNRs) at the single-molecule level. A fluorogenic reaction of the oxidation of a non-fluorescent reactant amplex red (AR) to a fluorescent product resorufin (RF) was used to probe and quantify the reactivity of the nanocatalysts. We have observed that the addition of TiO2 on AuNRs induced the light-dependent activity for the complexed catalyst. Single-molecule analyses revealed detailed reaction kinetics and reaction mechanisms that are usually hidden in conventional averaged ensemble methods. Our work here uncovers the structure-performance correlation and guides the development of efficient photochemical catalysts.

Committee: Hao Shen (Advisor); Arkaprabha Konar (Committee Member); Hanbin Mao (Committee Member) Subjects: Analytical Chemistry; Chemistry

Doctor of Philosophy, The Ohio State University, 2021, Chemistry

The purpose of this dissertation is to develop new synthetic routes built upon addressing green chemistry concepts such as energy efficient designs, use of renewable energy, use of renewable material, recyclable/reusability catalysts and develop biodegradable products. In this dissertation chapter 2, we describe the first report on complete aerobic oxidative dehydrogenation of any derivative of tetrahydroisoquinoline. This photocatalytic platform is achieved using off-the-shelf Ru(bpy)3Cl2 photosensitizer, sunlight, atmospheric oxygen/air and ambient temperature. The discovery of this new photocatalytic pathway was made possible through the combination theoretical calculations and droplet-based photoreaction screening platform that employs mass spectrometry for quantitative and qualitative monitoring of reaction intermediates and products in real-time. The optimized conditions were transferred to solution-phase isoquinoline synthesis, where 71.7% total yield could be produced in less than 4 h of reaction time using sun energy. Chapter 3 in this dissertation focusses on development of a new photocatalytic screening system based on catalytic oxygenation of small molecules using recyclable/reusable fullerene-C60. Here we developed a catalytic system for small molecules using interfacial reactivity of heterogeneous fullerene-C60 ¬catalyst – single component system. Fullerene-C60 is significant in photochemistry and is widely studied. In the work, we used characteristics of fullerene to develop a heterogeneous catalyst by binding the fullerene to a surface (e.g., thread or paper), which can be reused and/or recycled. Combination of this capability along with electrospray-based reaction screening enabled the discovery of easy, fast, green, and sustainable chemistry reaction processes such as photo-oxygenation and photo dehydro-dimerization. Chapter 4 features biodegradable Polylactide polymer catalytic synthesis from renewable material and the use of mass spectromet (open full item for complete abstract)

Committee: Abraham Badu-Tawiah (Advisor); Martin Haesemeyer (Committee Member); Anne Co (Committee Member); Vicki Wysocki (Committee Member) Subjects: Chemistry

Master of Science (M.S.), University of Dayton, 2020, Chemistry

Biochar can be made through the combustion of any biomass in an oxygen deprived environment. In this study, fluorescent, carbon-based particles were hydrothermally synthesized in a efficient manner from 3 different biomass sources. The particles were subsequently characterized with Infrared, Dynamic Light Scattering, Ultraviolet-Visible, Fluorescence, and Nuclear Magnetic Resonance spectroscopic methods. The spectroscopic results indicated that the particles are composed of a conjugated carbon lattice with nitrogen and carbon-oxygen functional groups. The use of an economical synthesis makes this compelling as a research focus. All 3 biochar-based carbon particles exhibit similar strong fluorescent behavior when excited by light in the ultra-violet to near visible range, with light emission occurring in the visible region approximately 400-600nm with an emission maximum in the 430-450nm region. The physical and fluorescence characteristics of these particles makes them an excellent candidate for future research into a safe, green, cost-effective medical or pollutant sensor.

Committee: Garry Crosson Dr. (Advisor); Mark Masthay Dr. (Committee Member); Justin Biffinger Dr. (Committee Member) Subjects: Chemistry

Doctor of Philosophy, The Ohio State University, 2019, Chemical Engineering

The importance of increasing the sustainability of chemical production processes has become a top priority for chemical manufacturing companies. Some of the target areas that are key to achieving more sustainable processes are the following: utilizing renewable carbon feedstocks, decreasing energy costs, decreasing waste via selective catalysis, and utilizing environmentally benign solvents. Heterogeneous catalyst design has the potential to address several of these target areas. The main focus of this work involves conducting rational design of heterogeneous catalysts that incorporate solvent-like molecules to perform selective biomass conversion and C-C bond reactions in more sustainable solvents. Sustainable conversion of biomass remains a challenge, including fructose dehydration to 5-hydroxymethylfurfural (HMF). Fructose can be selectively dehydrated to HMF in dimethyl sulfoxide (DMSO) without addition of an acid catalyst. The role of DMSO is examined starting with either fructose or HMF in DMSO/water. With increasing DMSO content, it is observed that fructose conversion, HMF selectivity, and post-reaction solution acidity increase. While DMSO degradation to sulfuric acid is a potential source of acidity and reactivity, a barium chloride precipitation test demonstrates that sulfate ions are not detectable after reaction. Additionally, an adsorption test in presence of a basic polymer determined that methane sulfonic acid, another DMSO degradation product, is also not detectable post reaction suggesting that DMSO is stable during reaction at 120°C and 150°C with oxygen present. Instead, the majority of the acidic species produced are formic acid, levulinic acid, and humins. These acids have a minimal effect on fructose conversion in DMSO. These results suggest that DMSO promotes fructose conversion mainly through solvation effects and not as an origin of acid catalysis. For HMF stabilization, the optimal molar fraction of DMSO in water is 0.20 to 0.43. Overall (open full item for complete abstract)

Committee: Nicholas Brunelli (Advisor); Umit Ozkan (Committee Member); Li-Chiang Lin (Committee Member); Andrew Michel (Committee Member) Subjects: Chemical Engineering