Physical Sciences and Mathematics Commons^™

The Effect Of Ionization Density In Applications Of Radiation Detection, Dosimetry, And Therapy, Daniel Mulrow

Arts & Sciences Electronic Theses and Dissertations

This dissertation covers a wide range of topics but is linked by the common theme of radiation interacting with materials and studying the result of those interactions. The introduction describes the fundamentals of how radiation interacts with material and how we are able to detect that radiation and the application of how we use those interactions in radiation oncology. The thesis starts with a chapter detailing the temperature dependence of the photophysics in two organic scintillators. This chapter is the foundation for a future study that will look the degree to which these scintillators can distinguish between gammas and neutrons …

Functionalized Plasmonic Nanostructures For Ultrasensitive Single Cell Analysis, Priya Rathi

Arts & Sciences Electronic Theses and Dissertations

Ultrasensitive detection and quantification of soluble, secreted and cell surface-bound proteins is critical for advancing our understanding of cellular systems, enabling effective drug development, novel therapies, and bio-diagnostics. However, exiting technologies are largely limited by their sensitivity, making the detection and quantification of low-abundant proteins extremely challenging. This forms a major barrier in various fields of biology and biomedical sciences. In this work, we introduce novel cellular analysis methodologies based on plasmon-enhanced fluorescence for analyzing cell structure and probing surface and secreted proteins from cells. In the first part, we introduce plasmon-enhanced expansion microscopy and demonstrate the effectiveness of employing …

Metal Salt Hydrolysis For Electrochemically Active Conducting Polymer Nanocomposites, Hongmin Wang

Arts & Sciences Electronic Theses and Dissertations

The diversity of nanostructures obtained from organic polymerization is limited when compared to the vast amount of inorganic nanostructures. This dissertation will focus on a synergistic mechanism between organic polymerization and in situ inorganic salt hydrolysis for developing electrochemically active organic-inorganic hybrid nanostructures. The degree of polymerization, crystallinity and doping level of the conjugated polymer backbone is controlled using oxidative radical vapor-phase polymerization resulting in organic semiconductors featuring high crystallinity and superior electrical conductivity. An aqueous metal salt solution of iron (III) chloride serves as an oxidant for initiating the polymerization and interestingly, this inorganic salt hydrolyzes in situ producing …

Computational Design Of Two-Dimensional Transition Metal Dichalcogenide Alloys And Their Applications, John Douglas Cavin

Arts & Sciences Electronic Theses and Dissertations

The discovery of bronze as an alloy of copper and tin is arguably the earliest form of material design, dating back thousands of years. In contrast, two-dimensional materials are new to the 21st century. The research presented in this dissertation is at the intersection of alloying and two-dimensional materials. I specifically study a class of two-dimensional materials known as transition metal dichalcogenides (TMDCs). Because of the large number of transition metals, there are many combinations of TMDCs that can be alloyed, making experimental exploration of the phase space of possible alloys unwieldly. Instead, I have applied first-principles methods to study …

Surface Modification Of Ii-Vi Semiconducting Nanocrystals, Calynn Morrison

Arts & Sciences Electronic Theses and Dissertations

This dissertation presents the compositional analysis of semiconductor materials by inductively coupled plasma optical emission spectroscopy (ICP-OES), a novel low-temperature shell growth precursor and installation pathway, and L-type for Z-type ligand exchange experiments conducted with four metal dithiocarbamate ligands. The techniques employed in the compositional analysis of semiconductor materials by inductively coupled plasma optical emission spectroscopy (ICP-OES) have a profound influence on the accuracy and reproducibility of the results. In Chapter 3, we describe methods for sample preparation, calibration, standard selection, and data collection. Specific protocols are suggested for the analysis of II-VI compounds and nanocrystals containing the elements Zn, …

Production Of Medical Radioisotopes Using Titanium Accelerator Targets, Christopher Shaun Loveless

Arts & Sciences Electronic Theses and Dissertations

Theranostic radiopharmaceuticals enable diagnostic imaging and radionuclide therapy in patients using a single molecular agent labeled with a diagnostic-therapeutic pair (e.g., 68Ga/177Lu) or a theranostic radionuclide (e.g., 131I). This theranostic approach can help inform patient-specific treatment plans and improve clinical outcomes. Radionuclide pairs used in theranostic agents fall into two categories: pseudo matched-pairs (e.g., 68Ga/177Lu) and matched-pairs (e.g., 124I/131I). Pseudo matched-pair radionuclides have similar chemistries and pharmacokinetics when bound to the same bioconjugate molecule. In contrast, identical chemistries and pharmacokinetics can be obtained by using the matched-pair radionuclides.

The isotopes of Sc include two diagnostic radioisotopes, 43Sc & 44Sc, and …

Separating Signal From Noise In High-Density Diffuse Optical Tomography, Arefeh Sherafati

Arts & Sciences Electronic Theses and Dissertations

High-density diffuse optical tomography (HD-DOT) is a relatively new neuroimaging technique that detects the changes in hemoglobin concentrations following neuronal activity through the measurement of near-infrared light intensities. Thus, it has the potential to be a surrogate for functional MRI (fMRI) as a more naturalistic, portable, and cost-effective neuroimaging system. As in other neuroimaging modalities, head motion is the most common source of noise in HD-DOT data that results in spurious effects in the functional brain images. Unlike other neuroimaging modalities, data quality assessment methods are still underdeveloped for HD-DOT. Therefore, developing robust motion detection and motion removal methods in …

Spectroscopic Investigations Of Excited Charge Carriers In Ii-Vi Nanoparticles, William Matthew Sanderson

Arts & Sciences Electronic Theses and Dissertations

The large absorption cross sections and the tunability of the energetic spacings between the states in the conduction (CB) and valence band (VB) within a semiconductor nanoparticle (NP) make them promising media for capturing electromagnetic radiation and converting it into charge carriers, or electricity. In photovoltaic devices that incorporate semiconductor NPs, it would be ideal if every photon could be absorbed by a NP and the carriers could be collected with perfect efficiency and without loss of energy. The relaxation pathways of the carriers within the NPs down to the band edge and their fate at the band edge contribute …

Phantoms To Placentas: Mr Methods For Oxygen Quantification, Kelsey Meinerz

Arts & Sciences Electronic Theses and Dissertations

Molecular oxygen (O2) is vital for efficient energy production and improper oxygenation is a hallmark of disease or metabolic dysfunction. In many pathologies, knowledge of tissue oxygen levels (pO2) could aid in diagnosis and treatment planning. The gold standard for pO2 measures in tissue are implantable probes, which are invasive, require surgery for placement, and are inaccessible to certain regions of the body. Methods for determining pO2 both non-invasively and quantitatively are lacking. The slight paramagnetic nature of O2 provides opportunities to non-invasively characterize pO2 in tissue via magnetic resonance (MR) techniques. As such, O2 can be treated as a …

Instrumentation For Dynamic Nuclear Polarization And Application Of Electron Decoupling For Electron Relaxation Measurement, Nicholas Howard Alaniva

Arts & Sciences Electronic Theses and Dissertations

Dynamic nuclear polarization nuclear magnetic resonance (DNP NMR) exploits internal electron spin and nuclear spin interactions to increase sensitivity and uncover valuable information regarding structure and dynamics of a system. To manipulate these interactions, instrumentation is developed to combine high-power microwave and radiofrequency irradiation with the ability to spin samples at the magic angle (MAS) at temperatures from 90 K to 4.2 K. Electron decoupling uses frequency-modulated microwaves to mitigate the electron-nuclear dipolar interaction, improving signal intensity and resolution in DNP NMR experiments. Electron decoupling is combined with short DNP periods to encode electron spin information in polarized nuclear signal. …

Self-Assembly Of Conducting Polymer Nano- And Microstructures For Energy Storage, Luciano Matteo Santino

Arts & Sciences Electronic Theses and Dissertations

Plastics are materials composed of many long chains of molecules with repeating subunits; strong interactions between neighboring molecules lead to the material used throughout the world. Plastics are commonly thought to be insulating, in stark contrast to the conductivity of metals. However, certain polymer structures were discovered to exhibit semiconducting properties, the subject of the Nobel Prize in Chemistry in 2000. Conducting polymers have a unique molecular structure with an electronically conjugated backbone, allowing electrons to freely travel both across the chain and in between chains. This work focuses on controlling the kinetics of the reaction between the vapors of …

Wave Function Engineering In Cdse/Pbs Core/Shell Nanocrystal Heterostructures, Brian Matthew Wieliczka

Arts & Sciences Electronic Theses and Dissertations

Colloidal semiconducting nanocrystals hold significant potential for third generation photovoltaics as solution processable materials that can surpass the Shockley-Queisser limit through multiexciton generation. In pursuit of this goal, the synthesis and optical characterization of CdSe/PbS core/shell quantum dots is reported. The spectroscopic behavior of these particles demonstrates their potential for use in optoelectronic devices, taking advantage of wave function engineering of the electron and hole. The rock salt PbS shell grows on all sides of the underlying zinc blende CdSe quantum dot, creating a core/shell structure. With increasing shell thickness, the band edge absorption and photoluminescence transitions decrease in energy …

Magic Angle Spinning Spheres And Improved Microwave Coupling For Magnetic Resonance, Pin-Hui Chen

Arts & Sciences Electronic Theses and Dissertations

Nuclear magnetic resonance (NMR) is a nondestructive technique used to characterize molecular structure and dynamics with atomic resolution. In solid-state NMR, magic angle spinning (MAS) is commonly implemented to improve spectral resolution by partially averaging anisotropic interactions. To further improve NMR sensitivity, dynamic nuclear polarization (DNP) is utilized to transfer the polarization from electron spins to nuclei of interest using microwaves. Advanced MAS DNP NMR instrumentation, such as spherical rotors for stable and fast spinning, dielectric lenses to effectively couple the microwaves into the sample, and the separation of receiving and transmitting circuits to decrease measurement noise, are developed to …

Electronic Transport Behavior Of Adatom- And Nanoparticle-Decorated Graphene, Jamie Anne Elias

Arts & Sciences Electronic Theses and Dissertations

To induce a non-negligible spin-orbit coupling in monolayer graphene, for the purposes of realizing the Kane-Mele Hamiltonian, transition metal adatoms have been deposited in dilute amounts by thermal evaporation in situ while holding the device temperature near 4K. Electronic transport studies including measurements such as gate voltage dependent conductivity and mobility, weak localization, high field magnetoresistance (Shubnikov de Haas oscillations), quantum Hall, and nonlocal voltage were performed at low temperature before and after sequential evaporations. Studies of tungsten adatoms are consistent with literature regarding other metal adatoms on graphene but were unsuccessful in producing a spin-orbit signature, at least partially …

Isotopically-Resolved Neutron Cross Sections As Probe Of The Nuclear Optical Potential, Cole Davis Pruitt

Arts & Sciences Electronic Theses and Dissertations

Neutron scattering experiments provide direct access to the forces experienced by nucleons in the nuclear environment. Due to the experimental difficulty of cross section measurements with neutrons, isotopically-resolved neutron scattering cross sections are sorely needed as inputs for many nuclear models. This dissertation presents the results from a campaign of isotope-specific neutron total cross section measurements on 16,18O, 58,64Ni, 112,124Sn, and 103Rh from 3-450 MeV and elastic scattering differential cross section measurements on 112,nat,124Sn at 11 and 17 MeV. Equipped with these new data and with computational improvements to the Dispersive Optical Model (DOM), we present DOM treatments of 16,18O, …

Radiolabeled Nanohydroxyapatite As A Platform For The Development Of New Pet Imaging Agents, Stacy Lee Queern

Arts & Sciences Electronic Theses and Dissertations

Positron emission tomography (PET) imaging utilizes drugs labeled with positron emitters to target and evaluate different biological processes occurring in the body. Tailoring medicine to the individual allows for higher quality of care with better diagnosis and treatment and is a key purpose for advancing research into developing new platforms for PET imaging agents. A PET nuclide of high interest for the development of these agents is 89Zr. This can be attributed to the long half-life of 3.27 days and low positron energy of 89Zr.

In this work, we developed a production method for 89Zr using Y sputtered coins that …

Tunable Electronic And Optical Properties Of Low-Dimensional Materials, Shiyuan Gao

Arts & Sciences Electronic Theses and Dissertations

Two-dimensional (2D) materials with single or a few atomic layers, such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs), and the heterostructures or one-dimensional (1D) nanostructures they form, have attracted much attention recently as unique platforms for studying many condensed-matter phenomena and holds great potentials for nanoelectronics and optoelectronic applications. Apart from their unique intrinsic properties which has been intensively studied for over a decade by now, they also allow external control of many degrees of freedom, such as electrical gating, doping and layer stacking. In this thesis, I present a theoretical study of the electronic and …

Linking Structure And Dynamics In Metallic Liquids: A Combined Experimental And Molecular Dynamics Approach, Robert Ashcraft

Arts & Sciences Electronic Theses and Dissertations

A major outstanding problem in condensed matter physics is the nature of the glass transition, in which a rapidly cooled liquid can bypass the transition into a crystalline state and the liquid structure is "frozen-in" due to kinetic arrest. To characterize the fundamental features behind this transition the liquid, both in the high temperature (equilibrium) and supercooled state, needs to be better understood. By examining the relationship between structure and dynamics a better characterization of the liquid state and a determination of the mechanisms that are ultimately important for the formation of the glass can be gained. In this dissertation, …

Spin Alignment Generated In Inelastic Nuclear Reactions, Daniel Hoff

Arts & Sciences Electronic Theses and Dissertations

The spin alignment of inelastically excited 7Li projectiles, when the target remains in its ground state, was determined through angular-correlation measurements between the breakup fragments of 7Li_ (_ + t). It was found that 7Li_ is largely aligned along the beam axis (longitudinal) in this type of inelastic reaction, regardless of the target. This longitudinal alignment is well described by DWBA calculations, which can be explained by an angular-momentum-excitation-energy mismatch condition. These calculations also explain the longitudinal spin alignment of excited nuclei in several other systems, showing the phenomenon is more general. The experiment involving 7Li was performed at the …

Instrumentation For Cryogenic Dynamic Nuclear Polarization And Electron Decoupling In Rotating Solids, Faith Joellen Scott

Arts & Sciences Electronic Theses and Dissertations

Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) using the higher polarization of electron radical spins compared to nuclear spins. The addition of electron radicals for DNP to the sample can cause hyperfine broadening, which decreases the resolution of the NMR resonances due to hyperfine interactions between electron and nuclear spins. Electron decoupling has been shown to attenuate the effects of hyperfine coupling in rotating solids. Magic angle spinning (MAS) DNP with electron decoupling requires a high electron Rabi frequency provided by a high-power microwave source such as a frequency-agile gyrotron. This dissertation describes the development …

Synthesis, Characterization, And Biological Activity Of Spherical Nucleic Acid (Sna) Constructs For Cancer Therapy And Imaging, Colin Calabrese

Arts & Sciences Electronic Theses and Dissertations

This dissertation focuses on the development of biocompatible oligonucleotide-based nanomaterials, known as spherical nucleic acids (SNAs), as therapeutic and diagnostic agents for intracellular gene regulation and in vivo cancer imaging by positron emission tomography (PET). SNAs consist of a nanoparticle core functionalized with a dense shell of oligonucleotides such as deoxyribonucleic acid (DNA). Detailed synthetic procedures and characterization of novel SNAs with purpose-built biocompatible core materials are described. The SNAs exhibit comparable chemical, physical and biological properties regardless of core composition. The functionalities of the SNAs were further tailored by deliberate design and chemical modification of their oligonucleotide sequences.

The …

Dynamic Pricing And Inventory Management: Theory And Applications, Renyu Zhang

Arts & Sciences Electronic Theses and Dissertations

We develop the models and methods to study the impact of some emerging trends in technology, marketplace, and society upon the pricing and inventory policy of a firm. We focus on the situation where the firm is in a dynamic, uncertain, and (possibly) competitive market environment. The market trends of particular interest to us are: (a) social networks, (b) sustainability concerns, and (c) customer behaviors. The two main running questions this dissertation aims to address are: (a) How these emerging market trends would influence the operations decisions and profitability of a firm; and (b) What pricing and inventory strategies a …