Chemistry Commons^™

Positron Emission Tomography In Oncology And Environmental Science, Samantha Delaney

Dissertations, Theses, and Capstone Projects

The last half century has played witness to the onset of molecular imaging for the clinical assessment of physiological targets. While several medical imaging modalities allow for the visualization of the functional and anatomical properties of humans and living systems, few offer accurate quantitation and the ability to detect biochemical processes with low-administered drug mass doses. This limits how physicians and scientists may diagnose and treat medical issues, such as cancer, disease, and foreign agents.

A promising alternative to extant invasive procedures and suboptimal imaging modalities to assess the nature of a biological environment is the use of positron emission …

Quantifying Temperature-, Pressure-, And Nuclear Quantum Effects On Hydrophobic And Hydrophilic Water-Mediated Interactions, Justin T. Engstler

Dissertations, Theses, and Capstone Projects

Water-mediated interactions (WMIs) are responsible for diverse processes in aqueous solutions, including protein folding and nanoparticle aggregation. WMI may be affected by changes in temperature and pressure, and hence, they can alter chemical/physical processes that occur in aqueous environments. Traditionally, attention has been focused on hydrophobic interactions while, in comparison, the role of hydrophilic and hybrid (hydrophobic–hydrophilic) interactions have been mostly overlooked. Here, we study the role of T and P on the WMI between nanoscale (i) hydrophobic–hydrophobic, (ii) hydrophilic–hydrophilic, and (iii) hydrophilic–hydrophobic pairs of (hydroxylated/non-hydroxylated) graphene-based surfaces. We find that hydrophobic, hydrophilic, and hybrid interactions are all sensitive to …

Engineering Rare-Earth Based Color Centers In Wide Bandgap Semiconductors For Quantum And Nanoscale Applications, Gabriel I. López-Morales

Dissertations, Theses, and Capstone Projects

For many years, atomic point-defects have been readily used to tune the bulk properties of solid-state crystalline materials, for instance, through the inclusion of elemental impurities (doping) during growth, or post-processing treatments such as ion bombardment or high-energy irradiation. Such atomic point-defects introduce local ‘incompatible’ chemical interactions with the periodic atomic arrangement that makes up the crystal, resulting for example in localized electronic states due to dangling bonds or excess of electrons. When present in sufficient concentrations, the defects interact collectively to alter the overall bulk properties of the host material. In the low concentration limit, however, point-defects can serve …

The Interaction Of Different Primary Producers And Physical And Chemical Dynamics Of An Urban Shallow Lake, Majid Sahin

Dissertations, Theses, and Capstone Projects

An artificial urban shallow lake, Prospect Park Lake (PPL), is situated on a terminal moraine in Brooklyn New York, and supplied with municipal water treated with ortho-phosphates. The constant input of the phosphate nutrient is the primary source of eutrophication in the lake. The numerous pools along the water course houses various aquatic phototrophs, which influence the water quality and the state of the system, driving conditions into favoring the survival of their species. In the first half of the dissertation, the focus of the project is on analyzing how the different primary producers in different regions of PPL affect …

Molecular Dynamics Simulations Of Self-Assemblies In Nature And Nanotechnology, Phu Khanh Tang

Dissertations, Theses, and Capstone Projects

Nature usually divides complex systems into smaller building blocks specializing in a few tasks since one entity cannot achieve everything. Therefore, self-assembly is a robust tool exploited by Nature to build hierarchical systems that accomplish unique functions. The cell membrane distinguishes itself as an example of Nature’s self-assembly, defining and protecting the cell. By mimicking Nature’s designs using synthetically designed self-assemblies, researchers with advanced nanotechnological comprehension can manipulate these synthetic self-assemblies to improve many aspects of modern medicine and materials science. Understanding the competing underlying molecular interactions in self-assembly is always of interest to the academic scientific community and industry. …

Using The Marcus Inverted Region And Artificial Cofactors To Create A Charge Separated State In De Novo Designed Proteins, Eskil Me Andersen

Dissertations, Theses, and Capstone Projects

To create an efficient de novo photosynthetic protein it is important to create long lived charge separated states. Achieving stable charge separation leads to an increase in the efficiency of the photosynthetic reaction which in turn leads to higher yields of end products, such as biofuels, electrical charge, or synthetic chemicals. In an attempt to create charge separated states in de novo proteins we hypothesized that we could engineer the free energy gaps in the proteins from excited primary donor (PD) to acceptor (A), and A back to ground state PD such that the forward electron transfer (ET) would be …

Interactions Of Organic Fluorophores With Plasmonic Surface Lattice Resonances, Robert J. Collison

Dissertations, Theses, and Capstone Projects

It is common knowledge that metals, alloys and pure elements alike, are lustrous and reflective, the more so when a metal surface is flat, polished, and free from oxidation and surface fouling. However, some metals reflect visible light, in the 380 nm to 740 nm range of wavelengths, much more strongly than others. In particular, some metals reflect wavelengths in certain portions of the ultraviolet (UV), visible, and near-infrared (NIR) regime, let us say 200 nm to 2000 nm, while absorbing light strongly in other segments of this range. There are several factors that account for this difference between various …

Mechanism Of Action Of Dihydropteridine Reductase, Gabriela Arias De La Rosa

Dissertations, Theses, and Capstone Projects

Human dihydropteridine reductase is an enzyme that transfers a hydride from NADH to reduce quinonoid 7,8-dihydropterin (qBH₂) to 5,6,7,8-tetrahydropterin (BH₄), which is a cofactor important in the production of neurotransmitters.DHPR deficiency causes a drastic form of the neurological genetic disease phenylketonuria (PKU) that does not benefit from a phenylalanine-free diet.From site-directed mutagenesis studies, mostly on Rat DHPR, we know that certain residues are important for cofactor binding, substrate binding, and hydride transfer; however, there are still some questions about how DHPR works, particularly, because there is not a crystal structure of the tertiary complex: What is …

Role Of Protonation State Changes And Hydrogen Bonding Around The Oxygen Evolving Complex Of Photosystem Ii, Divya Matta

Dissertations, Theses, and Capstone Projects

The mechanism of natural photosynthesis involves the use of solar energy to produce O₂ we breathe and food and fuel we intake. This process results in the biological oxidation of water that takes place at room temperature, neutral pH using earth abundant elements Ca and Mn. Understanding how this challenging chemical reaction occurs in photosynthesis can be useful for designing better artificial photosynthetic complexes that can be used as biofuels. My doctoral work is to study the deprotonation and oxidation events elucidating the mechanistic details of proton coupled electron transfer reaction in a photosynthetic protein.

The O₂ evolution …

Computational Modeling Of Charge And Excitation Energy Transfer Dynamics In Complex Environments, Ning Chen

Dissertations, Theses, and Capstone Projects

This thesis describes computational simulations of charge and exciton dynamics and quantum calculations of organic conjugated oligomers. A comprehensive computational study of charge hopping dynamics was conducted for a model of disordered chain of sites coupled to quantum environments. Time-dependent mean square displacement, diffusion constant, and mobility were calculated by three different computational methods for solving the master equation, which validate the accuracy of calculations. Approximate rate kernels were also tested to understand the effects of approximations in representing quantum environments. In addition to the effects of temperature and disorder, different values of the gradient in the site energy were …

Nmr Characterizations Of Candidate Battery Electrolytes, Stephen A. Munoz

Dissertations, Theses, and Capstone Projects

Enormous strides have been made in next-generation power sources to build a more sustainable society. Energy storage has become a limiting factor in our progress, and there are huge environmental and financial incentives to find the next step forward in battery technology. This work discusses NMR methods for characterizing materials for use in battery application, with a special focus on relaxometry and diffusometry. Examples are provided of various recent investigations involving novel candidate electrolyte materials with different collaborators. Works discussed in this thesis include: the characterization of a new disruptive solid polymer electrolyte technology, investigations of the dynamics of super …

Investigation Of Novel Electrolytes For Use In Lithium-Ion Batteries And Direct Methanol Fuel Cells, Kartik Pilar

Dissertations, Theses, and Capstone Projects

Energy storage and conversion plays a critical role in the efficient use of available energy and is crucial for the utilization of renewable energy sources. To achieve maximum efficiency of renewable energy sources, improvements to energy storage materials must be developed. In this work, novel electrolytes for secondary batteries and fuel cells have been studied using nuclear magnetic resonance and high pressure x-ray scattering techniques to form a better understanding of dynamic and structural properties of these materials. Ionic liquids have been studied due to their potential as a safer alternative to organic solvent-based electrolytes in lithium-ion batteries and composite …

Ultrafast Spectroscopy And Energy Transfer In An Organic/Inorganic Composite Of Zinc Oxide And Graphite Oxide, Jeff A. Secor

Dissertations, Theses, and Capstone Projects

The energy transfers and nature of defect levels of an organic/inorganic composite of Zinc Oxide and Graphite are studied with multidimensional spectroscopy. The edge and surface states of each composite are uncovered using excitation emission experiments showing which defect states are mediating the energy transfer from the metal oxide to the graphite oxide. Multidimensional time resolved spectroscopy further describes the effect of the carbon phase on the energy transfer pathways in the material.

Wigner High-Electron-Correlation Regime Of Non-Uniform Density Systems: A Quantal-Density-Functional-Theory Study, Douglas Mortimer Achan

Dissertations, Theses, and Capstone Projects

The Wigner regime of a system of electrons in an external field is characterized by a low electron density and a high electron-interaction energy relative to the kinetic energy. The low correlation regime is in turn described by a high electron density and an electron-interaction energy smaller than the kinetic energy. The Wigner regime of a nonuniform electron density system is investigated via quantal density functional theory (QDFT). Within QDFT, the contributions of electron correlations due to the Pauli exclusion principle, Coulomb repulsion, and correlation-kinetic effects are separately delineated and explicitly defined. The nonuniform electron density system studied is that …

Variable Pressure Nuclear Magnetic Resonance Studies Of Ionic Liquids And Electrophoretic Probe Design, Armando Julio Rua

Dissertations, Theses, and Capstone Projects

Energy storage materials play a key role in, efficient, clean, and versatile use of energy, and are crucial for the exploitation of renewable energy. The improve efficiency of energy use stimulates the development of energy storage such as batteries or super capacitors, toward higher power and energy density, which significantly depends upon the advancement of new materials used in these devices. The new materials need better understanding and description in the electrochemical properties. Nuclear Magnetic Resonance (NMR) has been an important tool in the characterization of ionic liquids and solids. The measurements of the relaxation times and the diffusion coefficient …

Quantum Crystallography Of Hydronium Cations, Sonjae Sycoria Wallace

Dissertations, Theses, and Capstone Projects

Cationic hydronium clusters of the form [HaOb]^c,(c>0), have been investigated. After investigating over 2000 crystal structures containing hydronium cations found in the Cambridge Structural Database. The hydronium cationic compounds that were most unusual, mischaracterized, or those of apparent aggregates, were investigated further by geometry optimization and in some cases with the Quantum Theory of Atoms in Molecules (QTAIM). The results of our investigations yielded the first reports of stable conformations of cyclic dihydronium cationic clusters. In a second investigation we reported the first theoretically confirmed transition state of a H7O3+conformer captured within a crystal. A third product from our …