Physical Sciences and Mathematics Commons^™

Vibrational Imaging At The Nanoscale: Surpassing The Diffraction Limit Using Tip-Enhanced Raman Spectroscopy, Farshid Pashaee

Electronic Thesis and Dissertation Repository

A deep understanding of the chemical composition of surfaces, interfaces or nanoscale structure with a high spatial resolution is an important goal in nanoscience and nanotechnology. Structural information can be collected using a variety of high spatial resolution techniques such as atomic force microscopy (AFM), scanning tunneling microscopy (STM), scanning electron microscopy (SEM), or transmission electron microscopy (TEM). Nevertheless, these methods do not offer molecular information such as vibrational spectroscopy techniques that allow one to collect molecular or lattice vibrations yielding to a precise picture of the molecular interactions in bulk materials as well as in surfaces and interfaces. Unfortunately …

Dynamic Studies Of Guest Molecules In Metal-Organic Frameworks Using Solid-State Nmr, Yuanjun Lu

Electronic Thesis and Dissertation Repository

Metal-organic frameworks (MOFs) are a new class of porous materials that possess large three-dimensional voids in their structures. In this work, Solid-state NMR (SSNMR) is used to examine the dynamics of guest molecules at various temperatures in MOFs that possess different types of channels. Chapter 2 introduces the ¹³CO₂ adsorption behavior in α-Mg formate studied by ¹³C SSNMR in conjunction with molecular dynamic simulation. ¹H-¹³C cross polarization technique has successfully determined the adsorption sites of CO₂ in this type of MOF to be hydrogen atoms. The dynamic analysis detects that at low temperature, …

Design And Fabrication Of Integrated Plasmonic Platforms For Ultra-Sensitive Molecular And Biomolecular Detections, Mohammadali Tabatabaei

Electronic Thesis and Dissertation Repository

One of the major challenges in analytical and biological sciences is to develop a device to obtain unambiguous chemical and structural properties of a material or a probe biomolecule with high reproducibility and ultra-high sensitivity. Moreover, in addition to such a high sensitivity, other cases such as minimum intrusiveness, small amounts of analyte, and short acquisition time and high reproducibility are key parameters that can be valued in any analytical measurements. Among the promising methods to achieve such endeavor, plasmon-mediated surface-enhanced spectroscopic techniques, such as surface-enhanced Raman spectroscopy (SERS), are considered as suitable options. Such techniques take advantage of the …

X-Ray Absorption Fine Structure Studies Of Calcium Silicate Hydrate Biomaterials In Drug Delivery, Xiaoxuan Guo

Electronic Thesis and Dissertation Repository

Calcium silicate hydrate (CSH), a new type of bioceramics, has gained significant attention in hard tissue restoration because of their impressive role in the stimulation of osteoblast proliferation and differentiation in vitro. The further development of mesoporous bioceramics opens up new opportunities for drug delivery in hard tissue therapies. In this thesis, interaction mechanisms of drug molecules with CSH of different morphologies and CSH/polymer composites, imaging of drug distributions in CSH carriers in nanoscale, and the biomineralization mechanisms of CSH in vitro during drug release are extensively investigated using X-ray absorption near edge structure (XANES) and scanning transmission X-ray …

In Situ High-Pressure Study Of Metal-Organic Frameworks And Their Performance For Co2 Storage Probed By Vibrational Spectroscopy, Yue Hu

Electronic Thesis and Dissertation Repository

Metal-organic frameworks (MOFs) are an important class of porous materials, owing to their potential applications in a variety of areas, including gas storage, molecular separations, catalysis, sensors and so on. Most importantly, their extraordinary surface areas, tunable pore properties and potential for industrial scale production have made MOFs a promising material for clean energy applications, such as CO₂ storage. The chemical and mechanical stabilities of MOFs play a crucial role in their CO₂ storage performance, which require extreme loading pressures that are far beyond ambient pressure at times. Application of high external pressure (e.g., in gigapascal range) on …

Computational Studies Of Compressed Diborane And Engineered Narrow-Gap Semiconductors, Amin Torabi

Electronic Thesis and Dissertation Repository

The research contained in this thesis is two-fold: understanding the behavior of diborane under pressure, and engineering wide-gap semiconductors in order to promote their optical eciency. Each of these themes are further explained below.

Diborane (B₂H₆), is a prototypical electron-deficient molecule and has received a great deal of attention in recent years due to its unique and peculiar structure, as well as its potential applications as a hydrogen-storage material. At high pressures, vibrational spectroscopy analysis have revealed several changes in the spectral profile that suggest occurrence of polymorphic transformations; however, the new crystal structures at high …

Complementary Mass Spectrometry Methods For Characterizing Protein Folding, Structure, And Dynamics, Siavash Vahidi

Electronic Thesis and Dissertation Repository

Proteins are involved in virtually every biochemical process. A comprehensive characterization of factors that govern protein function is essential for understanding the biomedical aspects of human health. This dissertation aims to develop complementary mass spectrometry-based methods and apply them to solve problems pertaining to the area of protein structure, folding and dynamics.

‎Chapter 1 uses fast photochemical oxidation of proteins (FPOP) to characterize partially disordered conformers populated under semi-denaturing conditions. In FPOP, ·OH generated by laser photolysis of H₂O₂ introduces oxidative modifications at solvent accessible side chains. By contrast, buried sites are protected from radical attack. Using …

From Solution Into The Gas Phase: Studying Protein Hydrogen Exchange And Electrospray Ionization Using Molecular Dynamics Simulation, Robert G. Mcallister

Electronic Thesis and Dissertation Repository

Here, we apply Molecular Dynamics (MD) simulations to investigate fundamental aspects of structural mass spectrometry (MS). We first examine microscopic phenomena underlying Hydrogen/Deuterium exchange (HDX). HDX interrogates structural dynamics of proteins by measuring the rate of Deuterium uptake into backbone amides. We perform microsecond MD simulations on ubiquitin to investigate this process. We find that HDX protection often cannot be explained by H‑bonding or solvent accessibility considerations. These findings caution against non-critical use of HDX data in structural contexts. We next use MD to examine the Electrospray ionization (ESI) mechanism of proteins. ESI is a soft ionization technique resulting in …

The Influence Of Long-Term Gamma-Radiation And Initially Dissolved Chemicals On Aqueous Kinetics And Interfacial Processes, Pamela A. Yakabuskie

Electronic Thesis and Dissertation Repository

This thesis presents work focusing on the long-term effect of gamma-radiation on aqueous solution kinetics. Ionizing radiation drives the decomposition of water to form both oxidizing (•OH, O₂, H₂O₂) and reducing (•e_aq⁻, •O₂⁻, •H, H₂) chemical species. Over time, these radiolysis products can react with dissolved solutes and participate in interfacial reactions. This can lead to significant changes in the eventual solution redox condition, and gas phase composition, and in certain cases result in the formation of solid species. Understanding the long-term solution kinetics for radiolysis …

Gamma-Radiation Induced Redox Reactions And Colloidal Formation Of Chromium And Cobalt Oxide Nanoparticles, Leena M. Alrehaily

Electronic Thesis and Dissertation Repository

The main goal of this thesis research is to develop a mechanistic understanding of radiation-induced chromium oxide and cobalt oxide nanoparticle formation in aqueous solutions containing initially dissolved metal ions. When exposed to ionizing radiation, water decomposes to form a range of chemically reactive radical and molecular products. This redox agents can readily change the oxidation state of dissolved metal ions. The solubility of a transition metal ion can vary by several orders of magnitude depending on its oxidation state and the solution pH. Thus, reactions that can alter the oxidation state of a dissolved ion can lead to the …