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Deng, FanPhoton Upconversion Based on Triplet-Triplet Annihilation
Doctor of Philosophy (Ph.D.), Bowling Green State University, 2014, Photochemical Sciences
Upconversion (UC), a process that can convert two or more photons with low energy to a single photon of higher energy, has the potential for overcoming the thermodynamic efficiency limits of sunlight-powered devices and processes, including photovoltaic cells, photocatalytic reactions, and photoelectrosynthetic processes. The UC phenomenon is traditionally synonymous with second-harmonic generation using nonlinear inorganic crystals and the sequential excitation of inorganic host materials doped with rare-earth metals, but also includes sensitized UC relying on the fusion of two energized triplet molecules. Sensitized UC, exhibits several distinctive features making it directly amenable for sunlight powering. Sensitized UC can be accomplished at much higher efficiencies with non-coherent continuous-wave excitation at extremely low power densities (< 1 mW cm-2). In this process, the photon energy absorbed by a sensitizer is transferred to an acceptor through triplet-triplet energy transfer, and two excited acceptor molecules undergo annihilation, producing (upconverted) singlet fluorescence. The first part of my research is kinetic study of triplet-triplet annihilation (TTA) process. The delayed fluorescence kinetic analysis reported by Schmidt and coworkers was used to reveal the maximum possible efficiency from a model red-to-yellow upconverting composition and this treatment was applied to the anthryl triplet absorption decay transients of triplet anthracene measured for the PdOEP/anthracene composition. The resulting parameters were obtained by the fits for various excitation pulse power. From this analysis, approximately 50% of the anthryl triplets that decay by TTA produce singlet fluorescence, consistent with the notion that spin statistics does not impose efficiency limits on upconversion photochemistry. The second part of my research is investigating unconversion compositions for TTA photon upconversion. Upconversion system using the red-light absorbing platinum(II) tetraphenyltetranaphthylporphyrin (PtTPTNP) as a triplet sensitizer with yellow emitter rubrene and PDI as the acceptor in both solution and polymer films was investigated. In deaerated toluene solution, stable and high quantum efficiency (6%) was observed. Apart from that, another Cd (II) texaphyrin (TXP) was used as a new NIR upconversion senstizer with rubrene as the acceptor to upconvert NIR (670-88 nm) incident photons into yellow fluorescence through sensitized triplet-triplet annihilation. The quadratic-to-linear power dependence of the upconverted rubrene fluorescence with respect to 750 nm incident laser power density was observed to conform to two extreme kinetic limits (weak and strong annihilation regimes). In deaerated DCM solution, stable quantum efficiency (1.6%) was observed. The third part of my research is to investigate more host materials for UC apart from organic solvent. Moldable polyurethane materials (Clearflex 50) prepared from their corresponding liquid precursors produce high efficiency, regenerative green-to-blue photochemical upconverting solids when impregnated with benchmark palladium(II) octaethylporphyrin (PdOEP) sensitizers and 9,10-diphenylanthracene (DPA) acceptor/annihilator molecules. The cured rubbery materials promote sufficient diffusion at room temperature to support the sequential bimolecular reactions necessary for both triplet sensitization and triplet-triplet annihilation occurring between the precisely doped chromophores. Similar to photochemical upconversion processes occurring in solution, the newly conceived rubbery upconverting polymers are shown to exhibit quadratic-to-linear incident light power dependence for the first time. Once the linear power regime is achieved, the highest possible quantum efficiencies for photochemical upconversion are realized. Quantum yields of upconversion in current polymer samples measured in this limit exceed 20%, 6 to 7 times greater than the current champion upconverting (nanoparticle) plastic.

Committee:

Felix Castellano (Advisor); H. Lu (Committee Member); Alexander Tarnovsky (Committee Member); John Laird (Other)

Subjects:

Analytical Chemistry; Chemical Engineering; Chemistry; Inorganic Chemistry; Physical Chemistry; Polymer Chemistry

Bludin, Alexey O.Peptide-Porphyrin Self-Assembled Materials
Master of Science (MS), Bowling Green State University, 2011, Chemistry

A 30-residue polypeptide AQPal14 that was designed to form a three-stranded coiled coil in aqueous solution contains a 4-pyridylalanine residue on its solvent-exposed positions. In the previously reported work, it was shown that the AQPal14 peptide can form directional bonds with the cis-positions of the Pt(ethylenediamine) (Pt(en)) linker and as a result form nanoscale globular and fibrillar assemblies. The current work describes how the reaction of the AQPal14 peptide with a linker having coordination preferences different from Pt(en) can affect the size and morphology of formed nanoassemblies. Specifically, a cobalt (III) protoporphyrin IX (CoPPIX) was chosen for this purpose since it can produces a six-coordinated CoPPIX(AQPal14)2 complex upon binding with AQPal14 in which two trimeric coiled coils of AQPal14 are bound to the axial positions of the porphyrin ring. It was found that conditions at which the AQPal14 peptide reacts with CoPPIX can affect the structure of the formed materials as well. Specifically, the self-assembly of AQPal14 and CoPPIX in unbuffered water leads to the formation of nanoscale globular assemblies having the morphology analogous to the AQPal14-Pt(en) structures. However, when AQPal14 reacts with CoPPIX in 20 mM phosphate buffer, pH 7, the millimeter-scale rod-like structures are formed. Formation of the nanoassemblies with similar morphology after the reaction of AQPal14 with either Pt(en) or CoPPIX suggests that the size and shape of the formed assemblies are not likely dictated by the coordination geometry of the linking compounds, but by the oligomerization state of the peptide. However, it was suggested that the formation of the rod-like structures does not depend on these factors and mostly depends on the crystallization of the phosphate ions in the presence of these compounds.

To study the effect of the oligomerization state on the self-assembling properties and structure of the product materials, a new peptide AQPal14N16 whose sequence is based on the sequence of the original AQPal14 peptide was designed and synthesized. It was expected that a single modification in the AQPal14 sequence would not only change the oligomerization state of the new AQPal14N16 peptide from a trimer to a dimer, but also affect the size and shape parameters of the assembled nanostructures as well. As described in this work, it was found that the change in the oligomerization state does affect the morphology of the self-assembled AQPal14N16-CoPPIX nanoassemblies and also enhance the ability of these nanomaterials to further assemble into microscale fibrous systems.

Committee:

Michael Y. Ogawa, PhD (Advisor); Neocles B. Leontis, PhD (Committee Member); John R. Cable, PhD (Committee Member)

Subjects:

Analytical Chemistry; Biochemistry; Biomedical Engineering; Biomedical Research; Biophysics; Chemical Engineering; Chemistry; Inorganic Chemistry; Materials Science; Molecular Chemistry; Molecules; Morphology; Nanoscience; Nanotechnology; Organic Chemistry; Pharmaceutic

Keywords:

peptides; proteins; porphyrins; peptide-porphyrin complexes; coiled-coils; self-assembly; circular-dichroism; light-scattering; nanomaterials; biomaterials; supramolecular structures; nanofibers; atomic force microscopy; scanning electron microscopy

Shandilya, Kaushik K.Characterization, Speciation, and Source Apportionment of Particles inside and from the Exhaust of Public Transit Buses Fueled With Alternative Fuels
Doctor of Philosophy in Engineering, University of Toledo, 2012, College of Engineering

The practical issue of Scanning Electron Microscope/Energy Dispersive X-ray Spectrometry (SEM/EDX) instrumentation compatibility for particle analysis is addressed. The physical and chemical characterization of fine particles is carried out inside a public transit bus fueled with biodiesel (BD) and ultra low sulfur diesel (ULSD).

The three sorts of square surface patterns represented the morphological characteristics of single inhalable particles in the air inside the bus in Toledo. The size and shape distribution results are compared to those obtained for a bus using ULSD and BD respectively.

Only the reproducible results from repeated experiments on ESEM and size distribution obtained by the GRIMM dust monitor are used in this study. The collected filters are analyzed using a computer controlled SEM to obtain aerosol elemental compositions. Factor analysis suggested possible sources of indoor particle levels in public transit bus as motor vehicles, outdoor soil and secondary particle formation. The conclusion is that SEM methodology is a valuable tool for studying the distribution of particulates.

A part of this study examines the toxic nature of these engine exhausts under different idling conditions. The results of the PM emission analysis showed that the PM mean value of emission is dependent on the engine operation conditions and fuel type. It is found that lubricant oil, PM ash content, and storage tanks are the major sources of elemental concentrations in the PM.

Another part of this study looks at the change from ULSD to BD in different idling mode that is investigated with respect to organic carbon (OC) and elemental carbon (EC) for public transit buses in Toledo, Ohio. The carbon source profile for both alternative fuels for eight carbon fractions is developed through real time experiments. The results indicated that the use of BD instead of ULSD is environmentally sustainable for human health and climate change.

A new method for determining kinetic parameters of soot oxidation is applied for exhaust particles collected from public transit buses. The results indicate that the use of BD in public transit buses will result in lower particle formation from the engine. Particle morphology is clearly spherical carbon nano particles with chain-like agglomerates.

Committee:

Ashok Kumar, PhD (Advisor); Cyndee Gruden, PhD (Committee Member); Farhang Akbar, PhD (Committee Member); Defne Apul, PhD (Committee Member); Dong-Shik Kim, PhD (Committee Member)

Subjects:

Alternative Energy; Analytical Chemistry; Atmosphere; Atmospheric Chemistry; Atmospheric Sciences; Chemical Engineering; Chemistry; Civil Engineering; Climate Change; Energy; Environmental Engineering; Environmental Health; Environmental Science; Environmental Studies; Experiments; Health; Health Sciences; Inorganic Chemistry; Morphology; Nanoscience; Particle Physics; Physical Chemistry; Public Health

Keywords:

Public Transit buses; Alternative Fuel; Scanning Electron Microscope; Carbon Speciation; Heavy Metals and elements; Factor Analysis; Physical Characterization; Shape and Size Analysis; Kinetics

Shcherbakova, Elena G.Implementation of High Throughput Screening Strategies in Optical Sensing for Pharmaceutical Engineering
Doctor of Philosophy (Ph.D.), Bowling Green State University, 2017, Photochemical Sciences
Modern molecular sensors are essential parts of many emerging medical technologies and have been utilized in reducing healthcare costs in developed countries, environmental monitoring, disease diagnosis, and in increasing the response of the world to pandemics or bioterrorism. Due to the rapidly developing fields of supramolecular chemistry and optical detection, new sensing approaches have been developed for the recognition of many essential molecules in aqueous solutions and biologicals fluids. Particularly, the emergence of fluorescent molecular sensors has opened up a direction for the evolution of differential sensing in the nanometric scale, something of which traditional electronic sensors were not capable. In this dissertation, we present the development and application of sensing approaches aimed at two types of chemical problems. Part of this dissertation focuses on the development of a high-throughput protocol using molecular self-assemblies for the recognition of chiral drugs and drug-related compounds that play an important role in pharmacology, toxicology, and pharmacokinetics. Chiral drug separation is now a central subject for pharmaceutical development and clinical therapeutics due to the advancement of asymmetric synthesis in the production of single enantiomer drugs or precursors with greater therapeutic benefits and low toxicity. The second topic describes the development of an optical assay aimed at detecting opioids in complex biological environments. Opioids and their synthetic analogues have been the cause of many accidental deaths across the world. We develop an optical assay that is simple, computationally robust, efficient and can detect low concentrations of opioids in complex media. This high-throughput sensor array is capable of sensing opiates and their metabolites in urine when mixed with other chemical agents. Moreover, it is capable via machine learning techniques of recognizing new opiate-related compounds, which opens opportunities in the development of new treatments for the opioid epidemic. Our work is a scientific contribution, merging concepts of chemistry and chemical engineering to balance molecular sensor development and minimal resource utilization.

Committee:

Pavel Anzenbacher, Jr., Ph.D. (Advisor); Alexis Dee Ostrowski, Ph.D. (Committee Member); R. Marshall Wilson, Ph.D. (Committee Member); Ernesto E. Delgado, Ph.D. (Committee Member)

Subjects:

Analytical Chemistry; Chemical Engineering; Chemistry; Health Care; Molecular Chemistry; Molecules; Organic Chemistry; Pharmaceuticals; Pharmacology; Physical Chemistry

Keywords:

Molecular Sensor; Molecular Self-Assembly; High-Throughput Screening; Pharmaceutical Engineering; Fluorescence Spectroscopy; Chiral Drugs; Enantiomeric Excess; Asymmetric Reaction Characterization; Supramolecular Sensors for Opiates;

de Leon, Al CaimolDevelopment, Fabrication, and Application of Hierarchically-Structured Polymer Systems
Doctor of Philosophy, Case Western Reserve University, 2016, Macromolecular Science and Engineering
Introducing surface features on polymer systems can lead to enhancement of an existing property, improvement of structural functionality, and can even introduce a new property that is not originally present to the bulk polymer. There are a number of fabrication approaches and list of possible applications available. However, existing systems can still be improved in terms of efficiency, freedom, and application. The dissertation focuses on unconventional fabrication methods for hierarchical coatings and particles, and on some studies, their application. Hierarchical coating can be efficiently fabricated by assembly of polystyrene microparticles and subsequent electropolymerization of hydrophobic conducting polymer. The resulting coating showed superhydrophobic property and effective protection against corrosion of the underlying metal substrate. Alternative to electropolymerization is the combined layer-by-layer assembly and subsequent surface-initiated polymerization on structured polymer coating. It has been demonstrated that the above method is a very efficient method of fabricating temperature-responsive coating that can switch from being superhydrophilic to superhydrophobic. Efficient method was developed to simultaneously functionalize both sides of free-standing film by surface-initiated polymerization. Investigation of the solvent response of layer-by-layered assembled polymer film led to the development of self-folding particles. Lastly, it has been demonstrated that the combined multilayer extrusion and reactive ion etching extends the limits of current systems for hierarchical particles.

Committee:

Rigoberto Advincula (Committee Chair); Stuart Rowan (Committee Member); David Schiraldi (Committee Member); Christian Zorman (Committee Member)

Subjects:

Chemistry; Experiments; Materials Science; Organic Chemistry; Physical Chemistry; Polymer Chemistry; Polymers

Keywords:

Hierarchical, Polymer, Superhydrophobic, Corrosion, Particles, Anisotropic, Polymer Brush

Silvestri, DominicThe Gas Phase Ligand Exchange of Cadmium ß-diketonate Complexes
Master of Science in Chemistry, Youngstown State University, 2014, Department of Chemistry
A series of gas-phase ligand exchange reactions involving Cadmium trifluorotrimethylacetylacetonate (Cd(tftm)2) were examined using a triple quadrupole mass spectrometer. Multiple co-sublimation experiments were explored with various metal ß-diketonates where several partial and complete ligand exchange processes were observed and are reported herein for the first time. In an attempt to elucidate possible mechanisms leading to the formation of the mixed ligand complex, select ion-neutral experiments were conducted within the collision cell of the triple quadrupole mass spectrometer.

Committee:

Brian Leskiw, PhD (Advisor); Howard Mettee, PhD (Committee Member); Ganesaratnam Balendiran, PhD (Committee Member)

Subjects:

Analytical Chemistry; Chemistry; Inorganic Chemistry; Physical Chemistry

Keywords:

Gas Phase Reaction; Ligand Exchange; Beta-diketonates; Cadmium complexes

Fernando, Juwanmandadige RoshanTuning the Opto-Electronic Properties of Core-Substituted Naphthalenediimides through Imide Substitution
Doctor of Philosophy, Case Western Reserve University, 2014, Chemistry
Core-substituted naphthalenediimides (core-substituted NDIs) were incorporated into rod-like molecules and oligomers through reaction at the imide nitrogen positions. N,N’-Di(4-bromophenyl)-2,6-di(N-alkylamino)-1,4,5,8-naphthalenetetracarboxydiimide was synthesized in only three steps, and used as a versatile platform to prepare extended structures by reaction with thiophene substrates using Suzuki-coupling conditions. The optoelectronic properties of the new compounds were examined by UV/vis absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry and theoretical calculations. The imide substituents had little effect on the optical and electrochemical properties of core-substituted NDIs in solution. A bathochromic shift of the absorption was observed upon film formation, accompanied by quenching of fluorescence. These observations are consistent with increased inter-molecular interactions between core-substituted NDI moieties in the solid state. All compounds were tested in organic solar cells by blending with poly(3-hexylthiophene) (P3HT), and several showed a photovoltaic effect, demonstrating their potential as electron acceptors in organic solar cell. The best solar cell was observed for core-substituted NDI with 4-(thiophen-2-yl)phenyl imide substituents (5a), showing a power conversion efficiency of 0.57% and a large open circuit voltage of 0.87 V. This approach allows new structure-property relationship studies of non-fullerene acceptors in organic solar cells, where one can vary the imide substituent to optimize photovoltaic parameters while keeping the optical and electrochemical properties constant. To study the structure-property relationships of core-substituted NDIs as acceptors for organic solar cells, a series of 2,6-dialkylamino NDI compounds with various substituents were synthesized, characterized and tested in bulk heterojunction solar cells by blending with P3HT. The imide substituents consisted of a linker connected to a thiophene group, where the linker was phenyl, methyl or ethyl. The core substituents were cyclohexylamino or 2-ethylhexylamino. While the various substituents had little effect on the opto-electronic properties in solution, they strongly affected device performance and blend morphology. Under the conditions studied, the best performance was obtained with the methyl linker combined with the cyclohexylamino core substituent, with a power conversion efficiency of 0.48% and a high open circuit voltage of 0.97V. For blends of P3HT with modified NDI non-fullerene acceptors, the methyl linker promoted larger phase separated domains than the ethyl or phenyl linkers. DFT calculations showed that the linker determines the orientation of the thiophene conjugated plane with respect to the NDI conjugated plane. That angle was 114°, 45°-61°, and 8° for the methyl, phenyl and ethyl linkers, respectively. Using thiophene at the end of the imide substituent adds a unique dimension to tune morphology and influence the molecular heterojunction between donor and acceptor. The effect of vinylphenyl imide substitution on opto-electronic properties of core-substituted NDIs were examined by synthesizing a series of NDI molecules. 2-Ethylhexylamino (RF8 series and RF6) and 5-(2-ethylhexyl)thiophene (RF7 series) groups were used as core substitutions. The optical properties in solution and thin films, and the electrochemical properties in solution of vinylphenyl imide substituted compounds (RF7b and RF8b) were compared with other imide substitutions: Hydrogen (RF7H and RF8H), 2-ethylhexyl (RF7a and RF8a), and phenylthiophene (RF6). The low energy absorption band maximum of RF7H, RF7a and RF7b in dichloromethane was 534 nm, 524 nm and 531 nm, respectively, indicating a small effect from the imide substituents. The low absorption band maximum of 2-ethyhexylamino core substituted compounds of RF8H, RF8a and RF8b in dichloromethane were 627, 625 and 627 nm, respectively, suggesting that the optical property of the RF8 series had little dependence on the imide group and were governed by the alkylamino core substituents. The optical absorption of thin films were similar to the solution absorptions, except for RF8b with vinylphenyl imide substituents. The absorption onset of RF8b red shifted by 104 nm going from solution (659 nm) to film (763 nm). In thin films, RF8b showed intense absorption in the range of 300 – 800 nm. These results suggest that opt-electronic properties can be tuned using core substituents, and that low band gap organic small molecule materials can be designed with the right choice of core/imide substitutions using NDI.

Committee:

Geneviève Sauvé (Advisor); John Protasiewicz (Committee Chair); Thomas Gray (Committee Member); Carlos Crespo (Committee Member)

Subjects:

Alternative Energy; Chemistry; Energy; Materials Science; Molecular Chemistry; Molecules; Morphology; Organic Chemistry; Physical Chemistry

Keywords:

organic electronics; electron acceptors; naphthalenediimide; photovoltaic cells; solar cells; n-type organic semiconductors; vinylphenyl; non-fullerene acceptors; core-substituted NDI

Knapp, Amanda R.Antimicrobial and Antitumor Properties of Free and Poly(Ethylene Glycol)-Poly(Lactic Acid) Encapsulated Silver N-Heterocyclic Carbene Complexes
Doctor of Philosophy, University of Akron, 2011, Chemistry
Since the development of the first metal N-heterocyclic carbenes (NHC) by Ofele and Wanzlick in the 1960s, investigation into this area has grown dramatically, especially after the synthesis of the first stable free metal carbene in 1991 by Arduengo. Since that time, metal carbenes have been synthesized for applications related to catalysis and more recently therapeutics. Research in the Youngs group has focused on applying the synthetic routes of Lin to make a variety of silver NHCs for medicinal purposes. More recently, encapsulation of the silver NHCs into nanoparticles have been investigated for sustained release and systemic delivery of the therapeutics. This dissertation will focus on both the synthesis of some new silver NHCs as well as their encapsulation into biodegradable nanoparticles. Chapter 1 discusses the advantage of using silver as an antimicrobial and anticancer agent, as well as why NHCs were chosen. It will also provide an overview of research in the area of nanoparticles that are relavent to encapsulation of our silver NHC complexes. Chapter 2 details the synthesis of two new silver NHCs with methylbenzoate substituents attached, as well as the antimicrobial activity of these compounds. Chapter 3 describes a series of mono-halogenated compounds that were synthesized in order to determine their water-stability using 1H NMR spectroscopy. Chapter 4 will discuss the synthesis of one of our most active compounds to date as well as its encapsulation into the biodegradable, FDA approved nanoparticle poly(ethylene glycol)-poly(lactic acid) (PEG-PLA). The efficacy of the silver NHC-encapsulated nanoparticle on a small-cell lung cancer line is also presented. Finally, Chapter 5 will describe the in vivo toxicity results of the same nanoparticle system performed on two different strains of mice utilizing two different delivery methods, including nebulization and intravenous injection, to demonstrate the potential of this silver NHC-nanoparticle for antimicrobial and anticancer applications.

Committee:

Wiley J. Youngs, Dr. (Advisor); Claire A. Tessier, Dr. (Committee Member); Peter L. Rinaldi, Dr. (Committee Member); Michael J. Taschner, Dr. (Committee Member); Amy Milsted, Dr. (Committee Member)

Subjects:

Biomedical Research; Chemistry; Experiments; Inorganic Chemistry; Nanoscience; Nanotechnology; Organic Chemistry; Pharmaceuticals; Polymer Chemistry; Polymers

Keywords:

silver; N-heterocyclic carbenes; nanoparticles; PEG-PLA; toxicity study; antimicrobial; anticancer

Muizzi Casanas, Dayana AndreinaLight Activated Nitric Oxide Releasing Materials
Master of Science (MS), Bowling Green State University, 2015, Chemistry
The ability to control the location and dosage of biologically active molecules inside the human body can be critical to maximizing effective treatment of cardiovascular diseases like angina. The current standard of treatment relies on the metabolism of organonitrate drugs into nitric oxide (NO), which are not specific, and also show problems with densitization with long-term use. There is a need then to create a treatment method that gives targeted release of NO. Metal-nitrosyl (M-NO) complexes can be used for delivery of NO since the release of NO can be controlled with light. However, the NO-releasing drug must be activated with red light to ensure maximum penetration of light through tissue. However, the release of NO from M-NO complexes with red-light activation is a significant challenge since the energy required to break the metal-NO bond is usually larger than the energy provided by red light. The goal of this project was to create red- sensitive, NO-releasing materials based on Ru-salen-nitrosyl compounds. Our approach was to first modify Ru salen complexes to sensitize the photochemistry for release of NO after red light irradiation. Next, we pursued polymerization of the Ru-salen complexes. We report the synthesis and quantitative photochemical characterization of a series of ruthenium salen nitrosyl complexes. These complexes were modified by incorporating electron donating groups in the salen ligand structure at key locations to increase electron density on the Ru. Complexes with either an –OH or –OCH3 substituent showed an improvement in the quantum yield of release of NO upon blue light irradiation compared to the unmodified salen. These –OH and –OCH3 complexes were also sensitized for NO release after red light activation, however the red-sensitive complexes were unstable and showed ligand substitution on the order of minutes. The substituted complexes remained sensitive for NO release, but only after blue light irradiation. The Ru-nitrosyl complexes could be regenerated by treatment of the complex with solutions of nitrite. Treatment of the exhaustively irradiated solutions with excess NO2- led to generation of a Ru-NO complex that was sensitive to blue light. Preliminary work on creating metallopolymers of Ru-salen-NO is also discussed.

Committee:

Alexis Ostrowski, PhD. (Advisor); George Bullerjahn , PhD. (Committee Member); Jeremy Klosterman , PhD. (Committee Member)

Subjects:

Chemistry; Inorganic Chemistry; Materials Science; Organic Chemistry; Polymer Chemistry

Keywords:

nitric oxide release; ruthenium salen complexes; photochemistry; red light activation

Yaman, GülşahChemistry of a new trispyrazolylborate ligand with some group 1 group 2 ions
Doctor of Philosophy, The Ohio State University, 2008, Chemistry

Single-site metal alkoxides are used to catalyze the controlled ring-opening polymerization (ROP) of lactides and other cyclic esters. In this study, a new trispyrazolylborate ligand, Tp*, containing a 3-substituted pyrazole with ─CMe2CH2OMe group has been synthesized. By synthesizing this new ligand we aimed that this ligand can form a pocket around Ca2+ in order to protect the metal center against ligand scrambling, transesterification, or deactivation by impurities, such as water.

First, the synthesis of 3-(2-methoxy-1,1-dimethylethyl)pyrazole, pz*H is described together with its reactions with the borohydrides MBH4, where M = Li, Na, and K, under melt conditions. At 180°C, this procedure leads to a mixture of products for M = Li, and at higher temperatures, a derivative LiTp'pz*H is isolated, wherein a B-H bond and a methyl group have been eliminated and a B-O bond has been formed. For M = Na, the reaction proceeds to give NaTp* but at higher temperatures NaB(pz*)4 is obtained. The reactions involving KBH4 and pz*H yield the dinuclear complex K2(Tp*)2pz*H. The reaction between NaTp* and TlOAc in dichloromethane at room temperature gives TlTp* along with NaOAc. TlTp* reacts with methyllitium in diethylether to give LiTp* and thallium metal, and, similarly, TlTp*and KH react in THF to give KTp* and Tl(0). In addition, the heavier alkaline earth metal iodides (Tp*MI where M = Ca, Sr and Ba) were synthesized by using TlTp* and the corresponding metal diiodide, MI2 in THF. However, Tp*MgI and Tp*ZnI were obtained from the reaction of MI2 and NaTp* in THF and dichloromethane, respectively.

The reaction between Ca[N(SiMe33)](THF)2 and TlTp*yieldsTp*Ca[N(SiMe3)]2-via [CaTp*]+{Ca[N(SiMe3)2)3]}-.-Heating-Tp*CaN(SiMe3)2-gives-CaTp*2-by disproportionation. Whereas MgTp*2 is prepared from MgBu2 and TlTp* in THF. Both CaTp*3 and MgTp*2 exist as salts in the solid state: [Tp*M]+[Tp*], but in solution the CaTp*3 undergoes dynamic Tp* exchange on the NMR time-scale. Slower ligand exchange in MgTp*2 is studied by variable temperature 13C{1H}-NMR spin saturation transfer experiments.

The reaction between Tp*CaN(SiMe3)2 and p-cresol in benzene gives Tp*CaOC6H*4-p-Me which can initiate the ROP of L-LA, rac-LA, trimethylene carbonate (TMC) and ε-caprolactone (ε-CL) in benzene-d6.

Committee:

Malcolm Chisholm (Advisor); James Cowan (Other); T. RajanBabu (Other)

Subjects:

Chemistry, General; Chemistry, General; Chemistry, Inorganic; Chemistry, Polymer

Keywords:

trispyrazolylborate; hemilabile ether appendages; group 1 and group 2 ions; thallium(I); zinc(II); ring-opening polymerization

Malone, MarvinPlasmonic Sensing And Spectroscopy of Subwavelength Particles with an Infrared Microscope
Doctor of Philosophy, The Ohio State University, 2012, Chemistry
Sensing and spectral measurements of subwavelength particles have been accomplished using an infrared microscope by placing particles in the subwavelength holes of a patterned thin metal film, i.e. a plasmonic mesh. When particles are the same size as the wavelength of light, they scatter light very efficiently and exhibit other unusual spectral effects. Spectroscopic results are presented of polystyrene microspheres, yeast cells, and previously airborne dust particles. Although the transmission spectrum of mesh under a microscope is a good background for studying subwavelength particles, it is bad for studying the plasmonics of mesh. Light incident on the mesh under an infrared microscope is from a ring of off-axis angles (17-37°) which differs greatly from the perpendicular incidence of a benchtop FTIR. Since surface plasmon polariton mediated resonances disperse with angle as a result of a change in the wavevector, k, the microscope was modified with the addition of an aperture to reduce the range of angles. Results are presented on the study of the plasmonics of Ni mesh under a modified infrared microscope. The results characterize fundamental aspects of surface plasmon mediated resonances on mesh including: an effective refractive index characterizing the strength of the interaction of infrared light with the metal’s conducting electrons, the strength of the coupling between the front and back surfaces of mesh, and the interaction strength between two resonances, the (-1,0) and (0,-1), by means of the bandgap which results from an avoided crossing.

Committee:

James Coe (Advisor); Heather Allen (Committee Member); Sherwin Singer (Committee Member)

Subjects:

Atmospheric Chemistry; Chemistry; Electromagnetics; Environmental Science; Molecular Chemistry; Physical Chemistry

Keywords:

plasmonics; surface plasmon polariton; infrared; microscope; single particle; sensing; spectroscopy

Guo, JunhongPart I: Biological Activities and Cellular Metabolism of 4-Hydroxy-7-oxohept-5-enoate and 5-Hydroxy-8-oxo-6-octenoate Lactones Part II: Carboxyalkylpyrrole, Pentylpyrrole and 4-Oxo-heptanedioic Amide Derivatives of Ethanolamine Phospholipids and Proteins
Doctor of Philosophy, Case Western Reserve University, 2016, Chemistry
Under oxidative stress, phospholipids (PLs) containing polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA), arachidonic acid (AA) and linoleic acid (LA), undergo oxidation and truncation to generate a multitude of reactive aldehydes including ¿-hydroxy-a,ß-unsaturated aldehyde-PLs such as 4-hydroxy-7-oxo-hept-5-enoyl phospholipids (HOHA-PLs), 5-hydroxy-8-oxooct-6-enoyl phospholipids (HOOA-PLs) and 9-hydroxy-12-oxododec-10-enoyl phospholipids (HODA-PLs), and the corresponding ¿-oxo-a,ß- unsaturated aldehyde-PLs such as 4-keto-7-oxohept-5-enoyl phospholipids (KOHA-PLs), 5-keto-8-oxooct-6-enoyl phospholipids (KOOA-PLs) and 9-keto-12-oxododec-10-enoyl phospholipids (KODA-PLs) from DHA-PLs, AA-PLs and LA-PLs, respectively. Recently, HOHA-PLs and HOOA-PLs were found to undergo spontaneous deacylation via an intramolecular transesterification mechanism to generate the corresponding HOHA-lactone and HOOA-lactone under physiological conditions. More recently, HOHA-lactone was found to be a precursor for the generation of 2-(¿-carboxyethyl)pyrrole (CEP) derivatives of proteins and ethanolamine phospholipids. The present thesis documents that CEP derivatives accumulate in RPE cells either by exogenous addition of HOHA-lactone or by HOHA-lactone generated endogenously in RPE cells exposed to oxidative or inflammatory insults. In addition, HOHA-lactone was found to exhibit hermetic effects on RPE cellular activity: low levels of HOHA-lactone induce proliferation and cell growth of RPEs while high levels of HOHA-lactone induce apoptosis. At high concentrations, HOHA-lactone induces RPE cell death by activating caspase-3 apoptotic signaling, where p53 may be involved in this apoptotic process, indicated by the induction and phosphorylation of p53, nuclear accumulation of p53, and the degradation of MDM2. Moreover, it has also been confirmed that HOHA-lactone can readily diffuse into RPE cells where it is detoxified by conjugation with GSH in the cytosol, forming an aldehyde adduct HOHA-lactone-GSH (=O) and an alcohol HOHA-lactone-GSH (-OH), which are then transported from cytosol to extracellular medium. At low levels, HOHA-lactone induces the secretion of VEGF in ARPE-19 cells, which correlates well with an increase in intracellular ROS and a decrease in intracellular GSH. VEGF secreted into the media showed angiogenic properties as indicated by increased migration and tube formation of HUVECs in matrigel when grown in media from ARPE-19 cells treated with HOHA-lactone. Wound healing and tube formation assays showed that HOHA-lactone-GSH conjugates have pro-angiogenic effects. The results of these studies show for the first time, that HOHA-lactone causes angiogenesis in HUVECs by more than one molecular pathway. In an indirect mechanism, HOHA-lactone induces the secretion of VEGF by RPE cells and VEGF can promote angiogenesis. In two other molecular mechanisms HOHA-lactone reacts with GSH or with the primary amino groups of biomolecules to form the corresponding GSH conjugates or CEPs that, in turn, also promote angiogenesis. A fourth angiogenesis pathway induced by HOHA-lactone may involve the formation of HOHA-lactone-GSH (=O), which then produces CEP derivatives by reaction with primary amino groups of biomolecules and CEP then promotes angiogenesis. In analogy with the generation of CEP from HOHA-lactone, HOOA-lactone was found to serve as a precursor of CPP modifications both in vitro and in vivo. In analogy with the biological activity of HOHA-lactone, HOOA-lactone was demonstrated to be capable of inducing intracellular oxidative stress and of causing apoptosis of ARPE-19 cells at high concentrations via activation of caspase-3. In view of the toxic potential of HOOA-lactone to ARPE-19 cells, the detoxification of HOOA-lactone in this cell type was also studied and the results showed that HOOA-lactone can easily diffuse through the cell membrane into ARPE-19 cells where it is detoxified by conjugation with GSH to form HOOA-lactone-GSH (=O) and HOOA-lactone-GSH (-OH). Recently, KODA-PLs, one of the LPO products from LA-PLs, were found to form the 4-ketoamide derivatives of the Lys residues of proteins. KOHA-PLs were expected to modify biomolecules to give similar stable 4-ketoamide adducts: 4-oxo-heptanedioic amide (OHdiA) derivatives. Using LC-MS/MS, KOHA-PL was found not only modify the primary e-amino group of protein Lys residues but also those of the ethanolamine headgroup of ethanolamine phospholipids (EPs) to produce OHdiA derivatives in vitro. In addition, OHdiA derivatives were also detected in vivo, evident by the presence of OHdiA derivatives in blood from both SCD patients and healthy individuals. Moreover, OHdiA adducts were shown to have pro-angiogenic effects and this OHdiA-driven angiogenesis was shown to be TLR2 dependent similar to angiogenesis promoted by CEP but different from VEGF promoted angiogenesis. Furthermore, anti-OHdiA antibody was found to exhibit significant cross-reactivity with CEP-HSA while anti-CEP antibody showed high structural specificity and did not show cross-reactivity with OHdiA-HSA. While ¿-hydroxy-a,ß-unsaturated aldehyde-PLs like HOHA-PLs, HOOA-PLs and HODA-PLs were previously shown to react with primary amino groups of proteins to produce the corresponding carboxyethylpyrroles (CEPs), carboxypropylpyrroles (CPPs) and carboxyheptylpyrroles (CHPs), respectively, the extent of the formation of analogous derivatives of the primary amino groups of EPs in vivo and the biological activities of those modified EPs remain poorly characterized. In the current study, an LC-MS/MS assay that allows simultaneous quantification of global CAP- and PP-modified EPs was developed by measuring levels of CAP-and PP-ETN released through hydrolysis of lipid extracts under catalysis by PLD from Strdptomyces chromofuscus. The presence of CAP-EPs and PP-EPs in vivo was established. A small pilot study revealed that levels of CAP-EPs and PP-EPs, except CHP-EPs, are significantly elevated in plasma samples from clinical SCD patients compared to those of hospitalized SCD patients.

Committee:

Robert Salomon (Advisor); Michael Zagorski (Committee Chair); Gregory Tochtrop (Committee Member); Witold Surewicz (Committee Member); Henri Brunengraber (Committee Member)

Subjects:

Analytical Chemistry; Biochemistry; Cellular Biology; Chemistry; Molecular Chemistry; Organic Chemistry; Toxicology

Keywords:

Lipid oxidation; Ethanolamine phospholipids; PUFAs; HOHA-lactone; Apoptosis; Oxidative stress; Retinal pigmented epithelial; Angiogenesis; HOOA-lactone; Glutathione; Sickle cell disease; AMD; OHdiA adducts; LC-MRM; Carboxyalkylpyrrole; Pentylpyrrole

Boulos, Victoria MarieThe Gas-Phase Ligand Exchange of Select Metal Bis-diisopropylacetylacetonate Complexes
Master of Science in Chemistry, Youngstown State University, 2017, Department of Chemistry
A series of gas-phase reactions were performed via co-sublimation within a triple quadrupole electron impact mass spectrometer. Novel alkaline earth and transition metal bis-diisopropylacetylacetonate coordination complexes were synthesized and observed to undergo gas-phase ligand exchange with select alkaline earth and transition metal bis-acetylacetonate and bis-trifluorotrimethylacetylacetonate complexes, and are reported herein for the first time. Also, novel alkaline earth and transition metal coordination compounds were characterized via x-ray crystallography. The results from these gas-phase experiments further establish the foundation of ligand exchange for this class of compounds.

Committee:

Brian Leskiw, PhD (Advisor); Howard Mettee, PhD (Committee Member); Sherri Lovelace-Cameron, PhD (Committee Member)

Subjects:

Analytical Chemistry; Chemistry; Inorganic Chemistry; Physical Chemistry

Keywords:

gas-phase; ligand exchange; beta-diketonate complexes

Senevirathna, WasanaAzadipyrromethene-based Metal Complexes as 3D Conjugated Electron Acceptors for Organic Solar Cells
Doctor of Philosophy, Case Western Reserve University, 2014, Chemistry
Organic photovoltaic is a promising technology for solar energy harvesting. The power conversion efficiency (PCE) of solution-processed bulk heterojunction (BHJ) cells has reached over ~10%. Fullerene and its derivatives have been the most investigated acceptor. However, fullerene derivatives have disadvantages: (i) weak absorption in visible and near-IR range, (ii) limited energy tunability. Promising alternative non-fullerene acceptors are limited, and the best efficiency achieved so far is ~5%. In this study, we used azadipyrromethene (ADP) as the building block to synthesize a series of electron acceptors. ADP derivatives are strong chromophores with strong absorption around ~ 600 nm. They are electro-active materials with two reduction peaks. Their optoelectronic properties can be tuned upon structural modifications. In this work, we synthesized a series of 3-dimensional (3D) conjugated homoleptic Zn(II) complexes of ADP dyes. The degree of conjugation in ADP was extended by installing phenylacetylene, ethynylthiophene and thiophene groups at the pyrrolic positions of the ADP core using Stille coupling. 3D structures of these molecules were synthesized by chelating with Zn(II). These new molecules showed broad intense red to near-IR absorption with onsets around 800 nm. The estimated LUMO energy level of Zn(II) complexes ranged from -3.60 to -3.85 eV. Their strong acceptor properties were demonstrated by fluorescence quenching experiments using poly(3-hexylthiophene) as the donor. These metal complexes quenched the fluorescence efficiently in both solutions and film. DFT calculations showed that all the metal complexes have distorted tetrahedral structures, with additional conjugated `arms’ extending in 3 dimensions. A unique feature of these complexes is that the two ADP ligands are p-stacked with each other, with frontier molecular orbitals delocalized over the two ligands. These complexes can therefore easily accept electrons, delocalize the negative charge over a large conjugated structure and have the potential of transporting charges in 3D, making them alternatives to fullerene derivatives as acceptors in organic solar cells, photo-detectors and other optoelectronic applications. Small internal reorganization energy is very desirable for high-performance optoelectronic materials, as it facilitates both charge separation and charge transport. DFT calculations were performed for a series of model molecules to gain better understanding on the energy level tuning, electron affinity, and the internal reorganizations of the electron transfer process. ADP-based compounds were more stable in their anionic state than cationic or neutral states and had high electron affinity, indicating their potential as n-type electron accepting material. The internal reorganization energy of ADPs were relatively low due its conjugated structure, and decreased by extending the conjugation via phenylethylene and ethylenethiophene substitutions, or by coordinating with BF2+. The largest decrease in reorganization energy was obtained when coordinating two azadipyrromethenes with zinc(II) to form a three-dimensional homoleptic zinc(II) complex, with calculated internal reorganization energies below 0.1 eV. These low reorganization energies are mainly due to the large rigid conjugated ¿ system. This work suggests that Zn(II) complexation is a novel strategy for obtaining materials that combine low internal reorganization energy with high electron affinity for the development of novel n-type optoelectronic materials. To further demonstrate their potential as electron acceptor, we made solar cells by blending the ADP-based molecules with a common electron donor, poly(3-hexylthiophene). All solar cells using Zn(II) complexes showed a photovoltaic effect, with a power conversion efficiency as high as 4.1%. Structure-property studies suggest that the 3D nature of these Zn(II) complexes prevents crystallization and promotes a favorable nanoscale morphology. The acceptor also significantly contributed to photocurrent generation by harvesting light between 600 nm and 800 nm. These results demonstrate a new paradigm to designing acceptors with tunable properties that can overcome the limitations of fullerenes.

Committee:

Geneviève Sauvé (Advisor); Anna Samia (Committee Chair); Clemens Burda (Committee Member); Robert Dunbar (Committee Member)

Subjects:

Alternative Energy; Chemistry; Energy; Molecular Chemistry; Molecular Physics; Molecules; Morphology; Organic Chemistry; Physical Chemistry

Keywords:

Photovoltaic, organic solar cells, electron acceptors, non-fullerene acceptors, 3D molecules, organic semiconductors, n-type organic semiconductors, Inverted solar cells, azadipyrromethene, metal complexes, bulk hetero junction solar cells

Guttman, JeremyPolymer-based Tunnel Diodes Fabricated using Ultra-thin, ALD Deposited, Interfacial Films
Master of Science, The Ohio State University, 2016, Electrical and Computer Engineering
Conjugated p-p bonded polymers offer a wide range of new electronic devices which have developed as a unique niche in the marketplace with an ever-growing need for integration. In particular, polymer-based tunnel diodes (PTDs) which exhibit negative differential resistance (NDR) at room temperature can be integrated with other novel components to realize memory and logic cells for highly manufacturable, roll-to-roll (R2R) printed electronics. The research presented here focuses primarily on the fabrication and operating principles behind PTDs. By incorporating an ultra-thin TiO2 interfacial tunneling barrier into a modified organic light emitting diode (OLED) structure, reproducible NDR can be realized. By varying the properties of the interfacial tunneling oxide, characteristics of NDR such as the peak-valley-current-ratio (PVCR), peak current density (J_peak), and the voltage at the peak density (V_peak) can be improved for memory and logic. This work successfully demonstrates room temperature NDR in PTDs using ultra-thin TiO2 interfacial tunneling barriers grown via atomic layer deposition (ALD). The intention of this work is to present a viable prototype PTD using ALD to deposit the tunneling barrier. By taking a look at the physical and electrical behavior behind the ALD deposited films, a better understanding can be gained on the nature of interfacial layer. It is suggested that localized defect states caused by oxygen vacancies induced during oxide growth is behind the tunneling behavior observed in the PTDs. By controlling the oxide growth, the crystal structure can be altered in order modify the oxygen vacancy concentration and therefore improve PVCR. Therefore, a key aspect of this thesis will be to observe how morphology, realized through varying temperature of ALD growth, can affect device characteristics. Additionally, to fully classify these devices, the physics behind the electrical operation needs to be further evaluated. Mapping the properties of the various materials through experimentation and modeling will serve as the starting place for future work to come. Finally, this thesis is part of an ongoing exploration for low-power, low-cost printed electronics. Therefore, a key aspect of this work is to present an argument for a printable process on a flexible, plastic substrate, and as such the requirement for a low temperature deposition is imperative. Low temperature ALD can come in the form of alternative precursors or alternative tunneling oxides. Moreover, by choosing to use alternative oxides, lower power NDR appearing at lower voltages may be realized. This study begins the work on finding alternative tunneling oxides that demonstrate similar oxygen vacancies observed in TiO2 films. In this case, Ta2O5 replaces TiO2 as the tunneling barrier. The initial data is promising, demonstrating a drop in the NDR voltage by approximately half compared to its TiO2 counterpart. Moreover, this work bolsters the claim that NDR is the result of a trap-based tunneling event through a defined defect band in the ALD deposited tunneling oxides. Though this thesis focuses solely on PTDs, the materials and processes demonstrated can be applied towards research interested in the conductivity properties of metal-oxides in addition to being useful for further work performed in the field of plastic electronics.

Committee:

Paul Berger (Advisor); George Valco (Committee Member)

Subjects:

Chemistry; Electrical Engineering; Engineering; Nanoscience; Nanotechnology; Organic Chemistry; Physical Chemistry; Physics; Plastics; Polymer Chemistry; Solid State Physics; Technology

Keywords:

polymer; organic; NDR; Negative Differential Resistance; Tunneling; IoT; Internet of Things; ALD; Atomic Layer Deposition; TiO2; Ta2O5; Memory; Logic; Low-power; flexible; printable; disposable; thin-film; oxygen vacancy; metal-oxide; defect; solid-state

Baughman, Jessi AlanSolid-State NMR Characterization of the Structure and Morphology of Bulk Heterojunction Solar Cells
Master of Science, University of Akron, 2012, Chemistry
A bulk heterojunction, organic solar cell, composed of a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was studied to determine the structure at the interface of the two compounds. Films of neat P3HT and the P3HT:PCBM composite where cast and annealed at elevated temperatures in order to determine the impact of sample annealing on the interface structure and interface volume of the blend. The films were characterized with 1D 13C solid-state NMR and 2D 1H-13C heteronuclear correlation (HETCOR) NMR. HETCOR NMR, with Lee-Goldburg cross polarization, was used to observe discrete intermolecular interactions between the alkyl side chain of P3HT and the C60, phenyl ring, and alkyl groups of PCBM. From these intermolecular interactions, a model of the structure at the P3HT:PCBM interface was constructed, which reveals the presence of stabilizing π- stacking between the thiophene ring of the P3HT and the phenyl ring of PCBM. Also, the C60 species interacts extensively with the alkyl groups of P3HT. The data indicates a phase separation after annealing that reduces the volume of the interface without disturbing the interface structure. A HETCOR NMR method using tangent cross polarization was used to confirm the phase separation of the P3HT and PCBM layers after thermal annealing.

Committee:

David Modarelli, Dr. (Advisor); Matthew Espe, Dr. (Committee Member); Kim Calvo, Dr. (Committee Chair)

Subjects:

Alternative Energy; Analytical Chemistry; Chemistry; Energy; Materials Science; Molecular Chemistry; Morphology; Polymer Chemistry; Polymers

Keywords:

bulk heterojunction; organic; solar cells; P3HT; PCBM; solid-state NMR; MAS; HETCOR; interface; electron transfer; power conversion efficiency; phase separation;

Viggiano, Rocco PInvestigations into High Surface Area and Hierarchical Phase Segregated Network Structures
Doctor of Philosophy, Case Western Reserve University, 2015, Macromolecular Science and Engineering
Aerogels are an interesting class of materials that possess many exotic and extreme properties. These properties are developed as the gel network is produced from solution. As the gel develops, it builds a hierarchical structure, possessing architectures at different size scales through molecular and macro-scale interactions. Once the solvent is removed, and the resultant aerogel is produced, the hierarchical nature of the material produces many desirable properties including: extremely high porosities (greater than 90% pore volume)[1], extremely low thermal conductivities (10-30 mW/m-k)[1], very low densities (as low as 0.002 g/cm3)[2], low refractive indices (as low as 1.01),[3] low dielectric constants (between 1.0 and 1.5),[4] high surface areas,[5,6] and the slowest speed of sound through a solid material. The first chapter of this thesis deals with the structure/property relationships of polymer/clay aerogels interfused with uniformly distributed air bubbles were examined. Through the incorporation of a polyelectrolyte in a montmorillonite (MMT) clay solution, the viscosity was systematically changed by the addition of ions with different charges. The bubbles were achieved via high speed mixing and were stabilized through the use of the surfactant sodium dodecyl sulfate (SDS). As the charge of the ion increased from +1 (Na+ ions) to +2 (Ca2+ ions) to finally +3 (Al3+ ions), the modulus of the resultant aerogels increased. The foamed polymer/clay aerogels showed a reduction in thermal conductivity while retaining similar mechanical properties to unfoamed polymer/clay aerogels. The most promising composition was one which contained 5% MMT clay/5% poly(vinyl alcohol)/0.5% xanthum gum/0.5% SDS/0.2% Al2(SO4)3·6(H2O) possessing a density of 0.083 g/cm3, an average modulus of 3.0 MPa, and a thermal conductivity of 41 mW/m·K. The second project investigated the feasibility of incorporating ground recycled polyurethane (PU) foam into clay/polymer aerogels. This was demonstrated and a range of compositions were prepared and characterized to determine the effect of variation in the formulations on density and mechanical properties of the resulting materials. The study followed a modified combinatorial approach. Initially, experiments were performed in water using either sodium exchanged montmorillonite or laponite clay, poly(vinyl alcohol) (PVOH) solution as the polymer binder, and the recycled PU foam. Freezing and freeze-drying the aqueous gels produced aerogels, which were characterized through density and mechanical testing, scanning electron microscopy, and thermal gravimetric analysis. The study was expanded by exploring alternative binder chemistries, including the use of an alginate polymer in place of the PVOH, or adding a polyisocyanate as across-linking agent for PVOH. The effect of recycled PU foam content, clay type and level, and binder type and level on mechanical properties of the aerogels were determined. The goal of the third project was to determine if lignin could be converted into foam-like aerogels using a well-established and environmentally benign freeze drying process. Interest in lignin as a bio-resource has been gaining popularity in recent years, as it is currently viewed by most industries as a waste product that in most cases is simply burned as a fuel source. The use of lignin in a polymer/clay aerogel offers the potential for a high value-added foam-like material potentially usurping the use of traditional petroleum derived foams in some applications. The present work demonstrates that lignin/clay and lignin/alginate aerogel samples can possess compressive moduli as high as 36.0 MPa. The final project addresses a fundamental material property concern associated with polyimide aerogels. Polyimide aerogels possess low dielectric constants, low thermal conductivities, high porosity, flexibility and low densities with outstanding mechanical properties. However, polyimide aerogels will undergo thermally induced shrinkage at temperatures far below their glass transition temperatures (Tg) or their onset of decomposition temperatures. Attempts to minimize thermal shrinkage were successful when a rigid filler, such as cellulose nanocrystals (CNCs), were introduced into the polyimide backbone. As an alternative to using rigid fillers, it was proposed that the incorporation of bulky, space filling moieties into the polymer backbone would also provide an effective route to reduce thermal shrinkage. An array of 20 polyimide aerogels were synthesized from 3,3’4,4’-biphenyltetracarboxylic dianhydride (BPDA) and 4,4’-oxydianiline (ODA) and in some cases BPDA and a combination of ODA and 9,9’-bis(4-aminophenyl) fluorene (BAPF). The aerogels were cross-linked with 1,3,5-benzenetricarbonyl trichloride (BTC). The polymer concentration, n-value and molar concentration of ODA and BAPF were varied. The resultant aerogels were fully characterized and were subjected to isothermal heating at 150 °C and 200 °C for up to 500 hours. It was observed that the samples containing BAPF possessed the lowest thermal shrinkages. Reductions in thermal shrinkage of around 20% were observed in samples containing the highest molar concentrations of BAPF.

Committee:

David Schiraldi, Ph.D. (Advisor); Mary Ann Meador, Ph.D. (Advisor); Gary Wnek, Ph.D. (Committee Member); Eric Baer, Ph.D. (Committee Member)

Subjects:

Aerospace Materials; Automotive Materials; Chemistry; Engineering; Experiments; Inorganic Chemistry; Materials Science; Organic Chemistry; Polymer Chemistry; Polymers

Keywords:

Aerogel, High Surface Area, Low Thermal Conductivity, Montmorillonite Clay, Polyvinyl alcohol, Polyurethane Foam, Lignin, Polyimide, Gel, Network, Cross-Linking, Ice Templating, Freeze-Drying, Lyophilization, Supercritical Fluid Extraction

Gasior, James KoleThe Gas-Phase Ligand Exchange of Trivalent Metal ß-Diketonates
Master of Science in Chemistry, Youngstown State University, 2017, Department of Chemistry
The gas-phase ligand exchange reactions incorporating main group and transition metal ß-diketonate complexes were investigated using a Finnigan TSQ 7000 triple quadrupole electron impact mass spectrometer. Specifically, trivalent iron and aluminum complexes were reacted with a variety of other metal ß-diketonates during mass spectrometric analysis, and the ensuing gas-phase reactions were shown to generate a variety of products. Relative peak heights of parent ions in the resultant cosublimation spectra were compared to the reactants’ baseline spectra to discern the relative reactivity of each parent ion, and subsequently, propose reaction mechanisms accounting for the production of mixed ligand products. To attain a more complete understanding of certain gas-phase reactions, tandem mass spectrometry was implemented to study selective reactions between specific parent ions and a neutral gas species. Analysis and interpretation of the resulting spectra allowed for the formulation of specific reaction mechanisms for each product detected. Finally, for the first time, the mechanism of partial ligand exchange was proposed and modeled using the PM3 semiempirical method to elucidate general features thought to be employed during the simultaneous mass analysis of homo-metal ß-diketonates.

Committee:

Brian Leskiw, PhD (Advisor); Howard Mettee, PhD (Committee Member); Sherri Lovelace-Cameron, PhD (Committee Member)

Subjects:

Analytical Chemistry; Chemistry; Inorganic Chemistry; Physical Chemistry

Keywords:

gas-phase; ligand exchange; diketonates; mass spectrometry

Elbatal, HanyTerpyridine-Based Metallo-Supramolecular Architectures: From Structure to Function
Doctor of Philosophy, University of Akron, 2013, Polymer Science
The research and applications of functional materials continue to grow rapidly in order to match the materials and energy needs of an increasing population. In this regard, perylene is a stable, organic material that possesses a rich chemistry and unique chemical, physical, and electronic properties. The molecular organization into predesigned geometries such as: cages, dendrimers, macrocycles and polymers, can add a profound enhancement to the material functional characteristics. At the heart of metallosupramolecular chemistry, tpy-M-tpy binding is a pivotal tool to construct complex and functional architectures. This dissertation reviews the chemical, structural, physical, and electrochemical properties of perylene with an emphasize on its metallosupramolecular chemistry. The synthesis of perylene-containing bis-, tetrakis-, and hexakis-terpyridine ligands along with their corresponding heteroleptic tpyRuIItpy complexes was achieved. These high molecular weight nano-dendritic architectures were characterized using 1H NMR, 13C NMR, COSY, and ESI-MS. These complexes exhibit broad absorption spectra (250-625 nm) and high molar absorption coefficients that are proportional to the number of photoactive units. The synthesis of supramolecular dyes based on tpy-RuII-tpy motifs connected to perylene-core either in bay- or peri-positions was demonastrated. The structures of these materials were confirmed using a combination of 1H NMR, 13C NMR, COSY, ESI-MS, and their electrochemical properties were studied via Cyclic Voltametry. These dyes were utilized as active ingredients for DSSCs, of which the photovoltaic properties were described. Fluorescent cyclic metallosupramolecular architectures were obtained via tpyZnIItpy mediated self-assembly of two aminobisterpyridine containing perylene ligands that were synthesized in a multistep procedure, the chemical structure and purity of both ligands and complexes were assured using a combination of 1H NMR, 13C NMR, COSY, and ESI-MS. DOSY was utilized to investigate the dimensions of the metallocycles that were compared to the values obtained from the energy minimized molecular modeling. The photophysical properties of these macrocycles showed strong fluorescence suggesting their potential use in LED. The formation of novel cyclic complexes including trimer and heteroleptic tetramers was achieved. The UV-Vis absorption and emission spectra of these materials were studied, and their chemical structures were illucidated via a combination of spectroscopic techniques including 1H NMR, ESI-MS, and MALDI-TOF-MS. Molecular modeling simulation of these nanosized complexes revealed cavities that can be used for host-guest chemistry.

Committee:

George Newkome, Dr. (Advisor); Steven Cheng, Dr. (Committee Member); Chrys Wesdemiotis, Dr. (Committee Member); Matthew Becker, Dr. (Committee Member); Alamgir Karim, Dr. (Committee Member)

Subjects:

Chemistry; Energy; Inorganic Chemistry; Materials Science; Nanotechnology; Organic Chemistry; Polymer Chemistry

Keywords:

Perylene Terpyridine Ru Zn Supramolecular Chemistry Macrocycles Derndrimer DSSCs Metallocomplexes

Pekar, Jennifer ChristinaThe Gas-Phase Ligand Exchange of Palladium Beta-diketonate Complexes
Master of Science in Chemistry, Youngstown State University, 2014, Department of Chemistry
A series of gas-phase reactions were performed via co-sublimation using a triple quadrupole electron impact mass spectrometer. Novel palladium ß-diketonate complexes, along with several other species containing different metals and ligands were synthesized and observed to readily undergo ligand exchange in the gas phase and are reported herein for the first time. Selective reactions were also conducted involving Pd and Ni complexes utilizing the collision cell of the mass spectrometer as a reaction vessel. Results from these gas-phase reactions shed light on the mechanism of ligand exchange for this class of metal ß-diketonate complexes.

Committee:

Brian Leskiw, Ph.D. (Advisor); Howard Mettee, Ph.D. (Committee Member); Ganesaratnam Balendiran, Ph.D. (Committee Member)

Subjects:

Analytical Chemistry; Chemistry; Gases; Inorganic Chemistry; Physical Chemistry

Keywords:

gas-phase, mass spectrometry, physical, analytical, inorganic, ligand, exchange, palladium, beta-diketonate

Hua, WeiInterfacial Water Organization and Ion Distributions Investigated with Vibrational Sum Frequency Spectroscopy: Answering Fundamental Questions for Environmental Chemistry
Doctor of Philosophy, The Ohio State University, 2013, Environmental Science
Knowledge of interfacial water organization and ion distributions is necessary to elucidate questions regarding atmospheric aerosol chemistry, thundercloud electrification, geochemistry, and ocean surface processes, among others. Water organization at air/aqueous interfaces is strongly influenced by inorganic ions, specifically, ion distributions that exist in the interfacial region, where the molecular environment changes from three-dimensions to two-dimensions. Over the past century, the study of water has been a major focus of experimental and theoretical work. Although much progress has been made, interfacial water behavior and ion distributions are still incompletely understood. Here, interface-specific nonlinear optical spectroscopies, conventional vibrational sum frequency generation (VSFG) and heterodyne-detected vibrational sum frequency generation (HD-VSFG), are employed to probe interfacial water molecules at the molecular level. HD-VSFG spectroscopy allows for direct interrogation of the average orientation of the transition dipole moment of interfacial water molecules that is intrinsically contained in the sign of the second-order nonlinear susceptibility, X(2). The water organization and ion distributions at air/aqueous interfaces of inorganic salt solutions are inferred from Im X(2) spectra obtained by HD-VSFG spectroscopy. It is shown here that salt purity grade and/or pretreatment have a tremendous impact on the interfacial water spectrum of aqueous salt solutions. It is determined that the presence of trace organic contamination is primarily responsible for spectral distortion for the bare air/ aqueous interfaces of salt solutions while the presence of trace polyvalent cations proves to be critical in exploring the alkali cation-carboxylate binding and comparing relative binding affinity of different cations at the air/aqueous surfactant interfaces. A standard pretreatment procedure for inorganic salts and their solutions is established for VSFG spectroscopy via a series of systematic studies. Results indicate that the ion-induced interfacial electric field is in the opposite direction for solutions containing sulfate and carbonate salts relative to solutions of chloride, nitrate and perchlorate salts. It is found that bicarbonate and its counterion do not significantly perturb the interfacial water organization. These findings are attributed to charge separation, or lack thereof, arising from ion distributions within the air/aqueous interfaces tested. It is also suggested that the cation identity (lithium, sodium, ammonium, magnesium) as well as the concentration changes result in the partial reversal of the net direction of the interfacial electric field in the nitrate salt solutions. These findings have great significance for understanding the differences observed in aerosol reactivity as a function of aerosol salt composition. In addition, we now have a better understanding of cloud droplet electrification and ocean surface properties. Moreover, a fundamental appreciation of ions at aqueous surfaces has been gained such that we now know that monovalent anions exist in the interfacial region and on average above their counterions. However, high valency anions exist below their counter cations, causing a reversal in electric field direction. Although various specific ion properties such as polarizability, size, charge (surface charge density), geometry (shape) have been suggested to account for interfacial ion distribution, it is indicated here that charge effect exerts a greater impact than the other factors in the case of oxyanions.

Committee:

Heather Allen (Advisor); Barbara Wyslouzil (Committee Member); Anne Carey (Committee Member); Lingying Zhao (Committee Member)

Subjects:

Analytical Chemistry; Atmospheric Chemistry; Chemistry; Environmental Science; Physical Chemistry

Ducay, Rey Nann Mark AbaqueDirect Detection of Aggregates in Turbid Colloidal Suspensions
Master of Science, Miami University, 2015, Physics
This thesis presents the application of an empirical model of total internal reflection (TIR) we recently developed in conjunction with a home-built sensor to detect nanoaggregates in highly scattering opaque polystyrene colloidal suspensions. The nanoaggregates are detected directly without any sample dilution or special sample preparation. Additional results on nanoaggregate detection in gold nanoparticle suspensions are presented. Preliminary tests of our model and sensor in an absorbing dye solution are also presented.

Committee:

Samir Bali, PhD (Advisor); Lalit Bali, PhD (Advisor); Jason Berberich, PhD (Advisor); Jon Scaffidi, PhD (Advisor); James Clemens, PhD (Committee Member); Karthik Vishwanath, PhD (Committee Member)

Subjects:

Analytical Chemistry; Biochemistry; Biomedical Engineering; Biomedical Research; Biophysics; Chemical Engineering; Chemistry; Experiments; Materials Science; Medical Imaging; Molecular Physics; Molecules; Nanoscience; Nanotechnology; Optics; Organic Chemistry; Physics; Polymer Chemistry; Polymers; Scientific Imaging

Keywords:

Nanoparticles; nanoparticle aggregation; empirical model; gold nanoparticles; polystyrene nanoparticles; microspheres; turbid media; TIR; total internal reflection; biosensors; highly-scattering; nanoaggregation sensing; DLS; UV-Vis; DLVO; Zeta potential

Lin, Wei-ChunIN-SITU SOLAR CELL STUDIES OF PEROVSKITE FORMATION AND DEGRADATION
Doctor of Philosophy, Case Western Reserve University, 2017, Macromolecular Science and Engineering
Since CH3NH3PbI3 based perovskites were discovered as viable active materials for the next generation photovoltaic devices, their instability in different environmental conditions has been a constant challenge. In pursuit of a better understanding of the degradation mechanisms, perovskite solar cells have been fabricated and investigated by scientists in order to find correlations between the solar cell characteristics/performance and the interface variation. In this thesis, the perovskite reactivity to humidity is studied by exposing samples to D2O environment for different durations. The degradation process of CH3NH3PbI3 perovskite is examined in-situ by using time-of-flight secondary ion mass spectrometry (ToF-SIMS). 3D images are constructed through the layer-by-layer spatially resolved elemental distribution analysis and the D2O moisture penetration through the sample. The intermediate products of interaction with moisture are analyzed by ToF-SIMS and X-ray photoelectron spectroscopy (XPS). We also investigated the electrical operation-induced degradation on CH3NH3PbI3 perovskite solar cells. Upon exposure to electrical current, the structure and composition were examined by combining depth-resolved imaging with ToF-SIMS, XPS and field-emission scanning electron microscopy (FE-SEM). The results show that the interface of the perovskite and the meso-porous TiO2 intermix into each other during the initial operations of solar cell. This intermixing turns the efficiency upward and improves the power conversion efficiency (PCE) up to ~50%. Both depth profiles and SEM images proved that operating devices undergo irreversible changes in thickness, which results in a dramatic performance loss eventually. In addition to studying the degradation process of the perovskite, a new formation method was developed to achieve complete conversion of PbI2 to CH3NH3I3 on FTO/Compact TiO2 substrate by employing a quaternary ammonium salt as an additive in the PbI2 solution. This complete conversion improves perovskite solar cell efficiency up to ~45 % compared to devices made without additive (from 11% to 16% in PCE).

Committee:

Clemens Burda (Advisor); David Schiraldi (Committee Chair); Alex Jamieson (Committee Member); Chung-Chiun Liu (Committee Member); Xuan Gao (Committee Member)

Subjects:

Chemistry; Materials Science; Molecular Chemistry; Organic Chemistry; Polymer Chemistry

Keywords:

Perovskite solar cells, ToF-SIMS, XPS, Depth profile, 3D image, Degradation, Degradation mechanism, Surface analysis, Elemental analysis, Humidity-induced degradation

Akdeniz, Ali Sensing of Enantiomeric Excess in Chiral Carboxylates
Doctor of Philosophy (Ph.D.), Bowling Green State University, 2016, Photochemical Sciences
Chirality of organic compounds plays a crucial role in human and veterinary medicine. More specifically, chiral carboxylates are extensively utilized in drug development processes, and a number of them are commercialized as drugs. Due to distinct pharmacological properties of enantiomers of chiral drugs, asymmetric synthesis became an essential tool to synthesize enantiopure compounds. While combinatorial libraries enable to screen catalysts, auxiliaries, and conditions rapidly, the enormous amount of resulting samples cannot be tested simultaneously. In this dissertation, we have reported two optical methods to determine the ee values of the chiral carboxylates in a high-throughput fashion. In the first method, we have employed cinchona alkaloids, known as Corey-Lygo catalysts, as chemosensors for ee analysis of chiral carboxylates. N-alkylated 9-chloromethylanthracenyl cinchona alkaloids form complexes with carboxylates by means of electrostatic interactions and hydrogen bonds. Using characteristic changes in fluorescence intensities of the chemosensors upon addition of analytes, we were able to perform the successful qualitative and quantitative ee analysis of enantiomers of chiral carboxylates in aqueous media. Using the sensor array comprising four N-alkylated cinchona alkaloids, we were able to achieve 100 % correct classification of chiral carboxylates, including several enantiomers of non-steroidal anti-inflammatory drugs (NSAIDs) successfully. Furthermore, quantitative ee analysis of (S)-Ibuprofen, (S)-Naproxen, and (S)-Ketoprofen shows prediction errors as low as 3%. The second method involves fluorescent macrocyclic sensors containing the chiral BINOL moiety, and H-bond donors in the pocket to form complexes with carboxylates. The intrinsic structure of the pocket of macrocycles displays an enantioselective behavior for chiral carboxylates, while the substituents at the 3,3’-positions of the BINOL moiety allow for tuning the shape and size of the cavity to enhance the recognition performance of the macrocycles. The resulting macrocycles show distinct responses for a number of carboxylates, including the enantiomers of ibuprofen, ketoprofen, 2-phenylpropanoate, mandelate, and phenylalanine. The fingerprint-like responses of the macrocycles, for structurally similar analytes, enabled to perform a qualitative analysis of 12 carboxylates with 100 % correct classification. Quantitative ee analysis of ibuprofen, ketoprofen, and phenylalanine shows that the sensors correctly identify the ee values of the unknown samples with an error of prediction < 3% even in the presence of impurities.

Committee:

Pavel Anzenbacher, Jr., Ph.D. (Advisor); Carol Heckman, Ph.D. (Committee Member); H. Peter Lu, Ph.D. (Committee Member); Andrew T. Torelli, Ph.D. (Committee Member)

Subjects:

Analytical Chemistry; Chemistry; Organic Chemistry; Physical Chemistry

Keywords:

Chemosensors; Anion detection; Sensor Arrays; Pattern Recognition; Fluorescence

Casiano-Maldonado, MadalisMass Spectrometry Techniques for the Characterization of Synthetic Polymers, Biopolymers, Biodegradation Products and Their Interactions
Doctor of Philosophy, University of Akron, 2012, Chemistry

The characterization of synthetic polymers and complex oligomeric mixtures by a combination of different mass spectrometry (MS) techniques is the main topic of this dissertation. Ion mobility (IM) separation and/or tandem mass spectrometry (MS2) were interfaced with single stage mass spectrometry for the fast, complete, precise and accurate characterization of different polymers, biopolymers, and biodegradation products. Additionally, the development of a mass spectrometry protocol for the quantitation of proteins adsorbed on different polymer surfaces was accomplished in this dissertation.

Over the passed years, synthetic routes for the creation of PEGs have been modified by the elimination of organic catalysts and solvents and the application of green chemistry for the generation of new polymers. In Chapter 4 of this dissertation, MS and MS2 were employed, as the main analytical techniques, for the structural elucidation of enzyme-catalyzed, functionalized PEG and tetraethylene glycol (TEG) biomaterials. The samples analyzed were synthesized by two different processes, transesterification and Michael addition reactions, both of them using CALB as the catalyst.

In Chapter 5 of this dissertation, polylactide was degraded using Proteinase K and its biodegradation products were analyzed by MS and MS2. Elucidation of its degradation products is important to the biomedical community; knowledge of these products helps to see any toxicity problems with the use of this polymer. The MS and MS2 results showed that the degradation products are short polylactide chains, down to the monomer. No other, potentially dangerous organics were detected.

In the following chapter of this dissertation (Chapter 6), the adsorption of three model proteins onto two different surfaces was evaluated over a pH range. The results were explained on terms of polymer chemistry, surface morphology, proteins¿¿¿¿¿¿¿ isoelectricpoints and molecular dimensions.

Finally, Chapter 7 reports how derivatization, degradation, or chromatographic separation can be avoided for the analysis of complex systems, if multidimensional mass spectrometry methods combining ion mobility separation and different ionization techniques are employed. Using this new approach complex poly(α-peptoid) samples were characterized. The results showed that the main product in the system contained the N-heterocyclic carbene (NHC) moiety that served as ring-opening polymerization catalyst. Furthermore, it was demonstrated that elimination of the NHC segment leads to cyclic poly(α-peptoid)s that have very similar conformations with comparably sized polypeptides

Committee:

Chrys Wesdemiotis, Dr. (Advisor); Abraham Joy, Dr. (Committee Member); David Perry, Dr. (Committee Member); Peter Rinaldi, Dr. (Committee Member); Michael Taschner, Dr, (Committee Member)

Subjects:

Analytical Chemistry; Chemistry; Materials Science; Organic Chemistry; Polymer Chemistry; Polymers

Keywords:

MASS SPECTROMETRY; CHARACTERIZATION; SYNTHETIC POLYMERS; BIOPOLYMERS; BIODEGRADATION

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