Chemistry Commons^™

Gas-Phase Proton Affinities Of Proline- And Pipecolic Acid-Containing Dipeptides, Trinh Ton

Dissertations, Theses, and Masters Projects

Mass spectrometry (MS) is one of the most used techniques in proteomics because it allows for both high-throughput and quantitative analyses. Bottom-up MS-based proteomics involves breaking down proteins into smaller chains of amino acids called peptides, ionizing and fragmenting the peptides, and identifying the fragments using sequencing databases. These databases depend on the random fragmentation at the backbone peptide bond of the peptides, as predicted by the mobile proton model. Research has shown that peptides containing proline or pipecolic acid have selective fragmentations that could lead to incorrect identification in the sequencing algorithms. These selective cleavages are called “the proline …

Characterizing Molecular Environments In Acrylic Paint Via Single-Sided Nmr, Lyndi Kiple

Dissertations, Theses, and Masters Projects

Acrylic paint is a modern artistic material made of colored pigment and polymeric binder. Acrylic binder requires fundamental study at the molecular level to understand its physical properties for purposes of art conservation and general polymer chemistry. The research presented in this thesis uses single-sided nuclear magnetic resonance (NMR) as a non-invasive and non-destructive way to measure relaxation and self-diffusion, which provide insight to molecular mobility and physical properties of proton-containing samples. Specifically, this study relies on T2 relaxation to gain insight to regions within acrylic paint with different molecular mobilities. In both dry and wet paint, relaxometry data revealed …

Exploring The Photophysics Of Brown Carbon Chromophores Using Laser-Based Spectroscopy And Computational Methods, Megan Elizabeth Alfieri

Dissertations, Theses, and Masters Projects

Atmospheric aerosols are made up of suspended liquids and solids in the atmosphere. These aerosols play a very important role in the solar energy exchange in Earth’s atmosphere as well have dramatic impact on human health. Different aerosols have different effects on the atmosphere depending on the physical properties of the aerosols.

The purpose of this research project is to understand how the structure of molecular chromophores impacts the solar absorption properties of aerosols. We propose a series of laboratory studies to investigate the outcomes from solar absorption of brown carbon chromophores: 1-phenylpyrrole, 2-phenyl-1-H-pyrrole, 2-phenylimadazole, as well as water complexes. …

Polyaromatic-Terminated Iron Polypyridyl Complexes For The Functionalization Of Carbon Surfaces And Electrocatalytic Hydrogen Generation, Caroline Marie Margonis

Dissertations, Theses, and Masters Projects

Artificial Photosynthesis (AP) focuses on developing methods for the conversion of solar energy into chemical fuel in the form of H2 and O2. Heterogeneous photocatalytic systems incorporating carbon nanotubes (CNTs) have shown much promise but are currently limited and expensive due to their reliance on noble metals. To that end, this work focuses on the development and synthesis of cheaper naphthalene- and pyrene-terminated iron polypyridyl complexes for use in the simultaneous functionalization of carbon surfaces, electrocatalytic proton reduction, and eventual incorporation in photocatalytic systems. Cyclic voltammetry was used to characterize the adsorption behavior of each complex on the surface of …

Evaluating Epoxy Cure And Adhesion Strength Through Single-Sided Nmr Measurements Of Molecular Mobility, Kayla Copeman

Dissertations, Theses, and Masters Projects

Commonly used in aerospace, automotive, marine, defense, electronic, and manufacturing industries, epoxy adhesives offer advantages over mechanical joints by providing stronger and/or more flexible bonds, more uniform stress distribution, low shrinkage, and lightweight connections between materials. Determination of curing kinetics and properties of interfaces between epoxy and inorganic substrates provides insight that is useful for quality control and defect detection for such applications. Single-sided NMR provides a nondestructive and inexpensive method for probing epoxy materials and spatially resolving the decay of spin-lattice and spin-spin relaxation times (T1 and T2) during and after curing of epoxy resins onto substrates. In this …

Investigating The Electron Transfer Dynamics Of Eosin Y Photosensitizers Using Single Molecule Spectroscopy, Kelly Margaret Kopera

Dissertations, Theses, and Masters Projects

Growing global energy demands have necessitated the search for alternative sources of renewable fuels. Dye-sensitized photocatalysis (DSP) is a promising low cost, sustainable method that directly converts solar energy to readily usable forms of energy such as hydrogen fuel. While DSP is a promising technology, its efficiency is limited by back electron transfer and kinetic redundancy. In order to fully understand these processes, single-molecule spectroscopy (SMS) is used to probe the electron transfer (ET) dynamics of photosensitizers. In particular, eosin Y (EY), a brominated fluorescein derivative that undergoes intersystem crossing prior to injection, is investigated using SMS. In this approach, …

Electronic Effects In A Cyclization Cascade To Diversified, Polycyclic, Helical Molecules, Caleb Lee Burns

Dissertations, Theses, and Masters Projects

Heterocyclic aromatic compounds and their derivatives are ubiquitous in the pharmaceutical and photochemical industries. Naphthochromene derivatives in particular have garnered great interest for their photochemical properties and biological activity. Herein, the effects of electronics on a three-step cascade reaction between aryl substituted 2-(4-aryl-3-((triethylsilyl)oxy)but-1-yn-1-yl)phenols and structurally diverse aldehydes is explored. The cascade is initiated by alkynyl substrate addition to BF3-activated aldehydes. The aldehyde undergoes condensation with the substrate phenol moiety forming an oxocarbenium ion, this initiates the alkynyl-Prins cyclization forming a new six-membered heterocyclic ring with an internal alkenyl cation. The cation is subsequently trapped by a Friedel-Crafts (FC) reaction by …

Mass Spectrometry-Based Proteomics: An Experimental Study Of Differential Bacteriophage Protein Expression And A Computational Investigation Of The Effects Of Proton Affinity On The Fragmentation Of Proline-Containing Dipeptides, Hao Qian

Dissertations, Theses, and Masters Projects

After decades with the development of genetics study, the next step of molecular biology had already been moved onto proteomics. The proteomics study provides an innovative aspect to deduct the relationship between genes and proteins. Meanwhile, research that focuses on the mechanism of protein interactions and intrinsic properties of proteins never cease. The mass spectrometry-based proteomics approaches have already shown their versatile and superior in studying the whole proteome of complicated organisms. This study focuses on practicing bottom-up method in determining and characterizing the expressed proteome of two mycobacteriophages, CrimD and Larva. The expressed proteins of CrimD and Larva in …

Indoor Chemistry: Development Of An Indoor Surface Extractor, Hannah Rose Przelomski

Dissertations, Theses, and Masters Projects

People spend around 90% of their time indoors. This means that indoor air can have an impact on human health. One of the main factors that makes indoor air differ from outdoor air is indoor areas have a higher surface area to volume ratio than outdoor areas. Surfaces give aerosol particles a place to deposit where they can stick or react. Some of this material can leave the surface and reenter the air. Being able to analyze the material on different indoor surfaces will help further the understanding of indoor surfaces’ impact on indoor air. A surface extractor was developed …

Copper(I) Iodide-Based Chemical Sensor Materials In Gaseous And Aqueous Media, Matthew D. Kessler

Dissertations, Theses, and Masters Projects

Chemical detection is an area of great importance in the shift to more green approaches to industry. Some of the chemical species produced by assorted industries can be harmful, long lived, and challenging to differentiate. Copper(I) iodide (CuI) is a material that readily forms complexes of multiple colors, both under visible and ultraviolet (UV) light. The process of CuI reacting with dimethyl sulfide vapor to produce a color change (vapochromism) has been analyzed to propose mechanistic information about the process. Using the information obtained, a series of potential sensor materials were developed with CuI as the base. The complexes were …

Structural And Dosage Dependence Of Electron Transfer From Conjugated Polymer Nanoparticles, Jaclyn Rebstock

Dissertations, Theses, and Masters Projects

Conjugated polymer nanoparticles (CPNs or Pdots) have become popular fluorophores for a variety of fluorescence imaging applications due to their brightness, photostability, and aqueous compatibility. Recently, their ability to generate charged species has begun to be exploited in applications ranging from photocatalysis to photovoltaic cells. Upon excitation, CPNs can eject an electron via photoinduced electron transfer (PET) to oxygen or other acceptors. The competition between fluorescence and PET is undesirable in redox-based applications. However, CPNs are capable of the simultaneous generation and detection of reactive oxygen species, expanding their use in photodynamic therapy (PDT). We seek to determine the dependence …

Unravelling The Aggregation Of Eosin Y Photosensitisers For Solar Energy Conversion, Huw Richards

Dissertations, Theses, and Masters Projects

The impact of molecular aggregation on the photophysics of eosin y adsorbed to TiO₂ was investigated using diffuse reflectance spectroscopy, steady-state fluorescence and time correlated single photon counting (TCSPC) measurements. Deconvolution of the diffuse reflectance spectra of eosin y on TiO₂ revealed the formation of H-aggregates, with the extent of H-aggregation increasing with increasing dye-loading concentration. The resultant bathochromic shift from the monomer diffuse reflectance maximum is due to Charge-transfermediated H-aggregates The fluorescent maximum also shifts with increasing dye loading concentration starting at 537.5 nm at a dye loading concentration of 7.5x10^-7 M and shifting to 585 …

Complex Mixtures: Identifying And Characterizing Secondary Organic Aerosols, Emma Quinn Walhout

Dissertations, Theses, and Masters Projects

Complex organic mixtures in the environment can contain hundreds to thousands of different organic molecules, and their composition and reactivity can have important environmental implications. In addition to gases, the atmosphere is made of a variety of small liquids and solids called aerosols. These aerosols have large impacts on human health, climate, and atmospheric chemical reactions. Here, secondary organic aerosol (SOA) from the ozonolysis of α-pinene is characterized. The atmospheric lifetime of SOA is very uncertain, but recent laboratory and modeling studies have demonstrated that photolysis is potentially an important process for organic mass loss from aerosol particles.1-5 Photolysis modifies …

Investigating The Molecular Choreography Of Atmospherically Relevant Molecules: A Dynamics Study, Kenneth Jacob Blackshaw

Dissertations, Theses, and Masters Projects

Investigating and understanding the chemistry of the atmosphere has historically been an important research topic. This importance has only strengthened in the recent decades as technological advancements have drastically increased anthropogenic emissions of hydrocarbons and nitroaromatic compounds. Indeed, we are in an era of unprecedented change of the chemical composition of the troposphere and never before has an in-depth understanding of atmospheric chemical properties been more sought-after. This study seeks to fill that need by probing the molecular dynamics of atmospherically relevant molecules through the use of velocity map imaging (VMI). In particular, we utilize VMI to study the photolysis …

Computational Investigations Of The Structure And Spectroscopy Of Small Biomolecules In The Gas Phase, Zachary Michael Smith

Dissertations, Theses, and Masters Projects

Small biomolecule systems were interrogated using infrared multiple photon dissociation (IRMPD) action spectroscopy and corresponding quantum chemical calculations with a particular focus on peptide fragmentation and protonation site preference. b2+ and b3+ fragment ions with a terminal lysine homolog residue were investigated using IRMPD in the fingerprint region (1000 cm-1 – 2000 cm-1) and a variety of computational methods. We present the first spectroscopic confirmation of b-ion formation with a lactam structure. Infrared spectra for b2+ fragment system indicate the presence of a mixture of structures, though final determination will require further investigation. The b3+ fragment ion infrared spectra show …

Surface-Enhanced Raman Spectroscopy Studies Of Organic Dyes For Art Conservation And Ph Sensing Applications, Shelle Nicholle Butler

Dissertations, Theses, and Masters Projects

Surface-enhanced Raman scattering (SERS) spectroscopy is a powerful analytical technique with widespread applications. In this work, SERS applications in the realms of art conservation and biosensing are reviewed. First, the theory of this unambiguous and ultrasensitive technique is explained. Next, a review of the pedagogical journey in art conservation research through the lenses of undergraduates is offered in Chapter 2, a chapter recently submitted to the American Chemical Society. Finally, an investigation in biosensing SERS is explored with developing a SERS pH sensitive probe while offering new insight into SERS capabilities and the relationship between analyte and nanoparticle.

Iron Polypyridyl Catalysts Assembled On Metal Oxide Semiconductors For Heterogeneous Photocatalytic Hydrogen Generation, Nicholas Race

Dissertations, Theses, and Masters Projects

Artificial Photosynthesis (AP) provides a promising method for the conversion of solar energy to chemical fuel in the form of H2 and O2. Development of heterogeneous systems in which H2 evolution catalysts are immobilized on metal oxide semiconductors is imperative for the large-scale implementation of AP systems. This research focuses on the immobilization of an active H2 evolution catalyst on large band gap semiconductors for the development and optimization of a highly active photocatalytic H2 generation system.

Ratiometric Fluorescent Sensors In Aqueous Environments, Matthew August Mccarron

Dissertations, Theses, and Masters Projects

Conjugated polymer nanoparticles (CPN) doped with a mercury sensitive dye are able to detect ion concentrations as low as a parts-per-billion within an aqueous environment. Select forms of spirolatam rhodamine dye are capable of selectively undergoing a ring-opening reaction in response to Hg2+ ions. The initial closed form presents as a colorless, non-fluorescent, compound while the opened form results in a colored and highly fluorescent form. The CPNs are also fluorescent, yet at a lower wavelength and can transfer of their energy into the dye molecules via Förster resonance energy transfer. The dye’s reaction with Hg2+ goes unhindered by the …

Effect Of Pigment Volume Concentration On Physical And Chemical Properties Of Acrylic Emulsion Paints Assessed Using Single-Sided Nmr, Mary Therese Rooney

Dissertations, Theses, and Masters Projects

Acrylic emulsion paint is one of the most common media employed by 20th century painters. Since early acrylic paintings have begun to require the attention of conservators, scientists are working to characterize the properties of these paints to facilitate conservation efforts. In this study, we report an investigation of the physical and chemical properties of acrylic emulsion paints using single-sided NMR in conjunction with gloss measurements and scanning electron microscopy coupled with energy dispersive spectrometry. Combining the data from these techniques gives insight into pigment-binder interactions and the acrylic curing process, showing that as pigment concentration is increased in paints, …

Radiation Shielding Bricks For Mars Using Martian Regolith Simulant And Hydrogen-Rich Polymers, Sara Sargent

Dissertations, Theses, and Masters Projects

Radiation shielding materials are an essential component of long-term space travel and habitation. The mission to Mars will require a radiation shielding material that can be produced on Mars through energy and cost-efficient means. in this study, Martian regolith simulant and hydrogen-rich polymers are used to create a radiation shielding material in the form of bricks. The bricks are capable of shielding against galactic cosmic radiation on Mars. There are three methods in which the bricks were formed: 1) a heated press, 2) a microwave oven in a CO2 atmosphere, and 3) a vacuum oven with a low CO2 pressure. …

Monitoring Infection Of E. Coli By Bacteriophage T7 Through Mass Spectrometry-Based Proteomics, Amy Swayne Schienschang

Dissertations, Theses, and Masters Projects

Mass spectrometry-based proteomics has become an important and versatile tool in analytical chemistry, making sense of complex biological samples and shedding light on the intricate proteomes of living organisms. Bottom-up proteomics studies are used to elucidate the changes in gene expression of bacteriophage T7 over the course of infection of Escherichia coli. E. coli cultures were infected with T7, sampled over time, and proteins were isolated and enzymatically digested. Nanoflow liquid chromatography combined with tandem mass spectrometry was used to detect proteolytic peptides and identify host and phage proteins. Generally, phage proteins were detected on a time scale fitting the …

Development Of A One Pot [4+2]/R[4+2] 2-Pyridone Synthesis And The Fluorescence Of 2-Pyridone Azafluorenones, Nicholas Angello

Dissertations, Theses, and Masters Projects

We report the concise synthesis of several tricyclic 2-pyridones via a one pot sequence involving an aldol condensation, alkene isomerization, intramolecular Diels-Alder cycloaddition, and selective retro-Diels-Alder cycloreversion. The starting materials are synthesized in one step from cheap and commercially available precursors. The intermediate [2.2.2]diazabicycloalkene cycloadducts can be isolated. The retro-Diels-Alder occurs at easily accessible temperatures due to base acceleration. Simple derivatization of the tricyclic products afforded azafluorenones with unprecedented fluorescent activity due to the pyridone motif.

Investigating The Charge-Transfer Dynamics Of Single-Molecule Sensitizers, Jenna Tan

Dissertations, Theses, and Masters Projects

Dye-sensitized solar cells (DSSCs) can reduce the cost of photovoltaic electricity generation to meet global energy needs. Optimizing DSSC efficiency requires a detailed understanding of the underlying charge transfer processes at the dye-semiconductor interface. By modifying the sensitizer structure, we gain insight into these charge transfer mechanisms. In this thesis, two hydroxyanthraquinone dyes are compared to investigate the impact of structure on charge-transfer and photobleaching dynamics. A combination of ensemble-averaged and single-molecule spectroscopy approaches are used to interpret the underlying ET kinetics.

Parsing The Aggregation- And Photodegradation-Induced Effects Of Rhodamine-Sensitized Tio2 And Zro2 Films, James Cassidy

Dissertations, Theses, and Masters Projects

The impact of rhodamine aggregates on the photophysical properties of rhodamine dyes adsorbed to TiO2 were investigated using diffuse reflectance spectroscopy, steady-state fluorescence, and time-correlated single photon counting (TCSPC). Photocatalyzed de-alkylation of rhodamine dyes containing tertiary amine groups (5-ROX, R101, and RB) was observed on TiO2, which resulted in a ~50 nm hypsochromic shift. Therefore, concentration dependent diffuse reflectance spectra of R560/TiO2 samples, which contained primary amines, demonstrated the formation of H- and J-aggregates at the expense of the monomers. The formation of J-aggregates resulted in FRET between monomers and J-aggregates which yielded a bathochromic shifted fluorescence spectra as a …

Synthesis Of [2.2.2]-Diazabicyclic Alkaloids: I: Diels-Alder Reactions Of A C2-Carboxy Pyrazinone & Ii: Intermolecular Diels-Alder Reaction Of A Proline Derived Pyrazinone With Symmetric Dienophiles, Jonathan Clarence Perkins

Dissertations, Theses, and Masters Projects

[2.2.2]-Diazabicyclic alkaloids are a natural product family with diverse biological activities. The development of a synthetic methods towards the synthesis of [2.2.2]-diazabicyclic alkaloids is described. I: Diels-Alder Reactions of a C2-Carboxy Pyrazinone Using an N-heterocyclic carbene catalyzed aroylation of a proline 3,5-dichloropyrazinone, a synthetic route to C2-carboxy pyrazinones was developed to study the intermolecular and intramolecular Diels-Alder reactions of these compounds to form the bicyclo[2.2.2]diazaoctane core. Studies showed that having oxidation present α to the pyrazinone ring did not provide any significant increase in reactivity or selectivity as compared to pyrazinones without oxidation α to the ring. In some cases, …

Physical Properties Of Traditional And Water-Miscible Oil Paints As Assessed By Single-Sided Nmr, Nicholas Anthony Sanchez Udell

Dissertations, Theses, and Masters Projects

Single-sided NMR has been demonstrated as a useful technique for the inexpensive and non-invasive study of cultural heritage objects, including numerous different painting and paint samples. The relatively recent invention of water-miscible oil paints – a new form of environmentally friendly oil paint that can be thinned and cleaned by water – provides a need for analysis of the physical properties of the cured paint films. Single-sided NMR offers an excellent analytical tool to study the structural effects of the emulsifying agent present in water-miscible oil paints on the paint linoxyn network by measuring the transverse (T2) relaxation times for …

Synthesis, Structure And Optical Memory Properties Of Copper (I) Thiocyanate Networks With Aromatic Amines, Diimines And Alkyl Sulfides, Gerardo Ayala

Dissertations, Theses, and Masters Projects

A series of CuSCN compounds were synthesized. Ligands included the alkyl sulfides methyl sulfide (Me2S), ethyl sulfide (Et2S), isopropyl sulfide (Pri2S) and tetrahydrothiophene (THT); diimine ligands pyrazine (Pyz), 2,3-dimethylpyrazine (2,3- Me2Pyz), 2,5-dimethylpyrazine (2,5-Me2Pyz), 2-aminopyrazine (2-NH2Pyz) and 2- methoxypyrazine (2-MeOPyz); two-ring diimines quinoxaline (Qox), quinazoline (Qnz), phthalazine (Ptz); and 3-halopyridines 3-chloropyridine (3-ClPy), 3-bromopyridine (3- BrPy), 3-iodopyridine (3-IPy). Crystal structures were solved for twelve products. With the exception of one Cu(II) compound, all could be classified in the common motifs of chains, ladders or sheets. Alkyl sulfides formed either 1:2 (CuSCN)L2 1-D chains (L = Me2S, 1a and THT, 4) or 1:1 …

Dye-Sensitized Tio2 Modified With Iron Polypyridyl Catalyst For Photocatalytic Hydrogen Evolution, Wanji Zhang

Dissertations, Theses, and Masters Projects

Artificial Photosynthesis (AP) focuses on finding a way to harness solar energy to generate a chemical fuel. TiO2 semiconductors are of interest to AP research due to its relatively low cost and widespread use as an efficient charge-separating support. This research focuses on the development of a device for photocatalytic hydrogen generation. Our approach utilizes the immobilization of iron polypyridyl catalysts and ruthenium chromophores on TiO2 through stable phosphonic acid anchoring groups.

Expanding The Scope Of Terminal Alkynes In Chemical Biology, Johnathan Charles Maza

Dissertations, Theses, and Masters Projects

The terminal alkyne is one of the most widely used chemical moieties in chemical biology. Thanks to the relative absence of this functional group in biology, it has become a widespread functional handle for a plethora of biorthogonal chemistries. Our group has extended the scope of this functionality by developing a biological variant of the Glaser-Hay coupling, which brings together two terminal alkynes to form a diyne linkage. However, our initial findings revealed that the chemistry is plagued by protein degradation due to a deleterious copper(II) hydroxyl intermediate. Herein we extend the scope of the terimanl alkyne be developing a …

Gas-Phase Thermochemical Properties Of Proline-Containing Dipeptides And Fluorinated Alcohols Using The Extended Kinetic Method, Kathy Tang Huynh

Dissertations, Theses, and Masters Projects

No abstract provided.