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Time-Resolved Phosphorescence Spectroscopy at Cryogenic Temperatures for the Environmental Analysis of Polycyclic Aromatic Sulfur Heterocycles in Oil Contaminated Sites.
Title
Time-Resolved Phosphorescence Spectroscopy at Cryogenic Temperatures for the Environmental Analysis of Polycyclic Aromatic Sulfur Heterocycles in Oil Contaminated Sites.
Creator
Al Tameemi, Maha, Campiglia, Andres, Zou, Shengli, Harper, James, Heider, Emily, Coffey, Kevin, University of Central Florida
Abstract / Description
The large volume of crude oil released into the Gulf of Mexico by the Deepwater Horizon (DWH) accident has raised considerable concerns over potential ecosystem impacts. The dispersion of harmful oil components into the ocean waters could pose long term risks to flora and fauna. Due to the complexity of oil contaminated sites, the unambiguous identification and quantitation of environmental pollutants often requires the sequence of high-performance liquid chromatography (HPLC) and gas...
Show moreThe large volume of crude oil released into the Gulf of Mexico by the Deepwater Horizon (DWH) accident has raised considerable concerns over potential ecosystem impacts. The dispersion of harmful oil components into the ocean waters could pose long term risks to flora and fauna. Due to the complexity of oil contaminated sites, the unambiguous identification and quantitation of environmental pollutants often requires the sequence of high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). A classic example is the analysis of the sixteen polycyclic aromatic hydrocarbons included in the priority pollutants list of the U.S. Environmental Protection Agency (EPA-PAHs).This dissertation tackles a different aspect of environmental analysis as is focuses on the photoluminescence spectroscopy of polycyclic aromatic sulfur heterocycles (PASHs). Since considering the EPA-PAHs alone can lead to drastic underestimations of potential toxic effects of oil spills, a strong case can be made for including hetero-aromatic compounds in risk assessments of contaminated sites. PASHs exist in an even greater variety of chemical structures than PAHs and, because of the asymmetry imposed by the heteroatom, the number of PASHs isomers is usually large. The existence of numerous isomers of the same molecular weight increases the difficulty of separation and identification by chromatographic methods.This dissertation demonstrates the capability to differentiate individual PASHs isomers of MW 234 g mol-1 via vibrational spectroscopy at liquid nitrogen (77 K) and liquid helium (4.2K) temperatures. Fluorescence and phosphorescence spectra are presented for isomer determination at the parts-per-billion (ng. mL-1) concentration levels. It is demonstrated that the relatively long phosphorescence decays of PASHs facilitate the time discrimination of strong fluorescence.interference from PAHs and methylated-PAHs often present in Normal-Phase HPLC fractions. The spectral and lifetime databases compiled in this dissertation have paved the road to explore the full dimensionality of photoluminescence spectroscopy.
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Date Issued
2017
Identifier
CFE0007275, ucf:52183
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007275
Detection of Mercury Through Surface Plasmon Resonance of Immobilized Gold Nanorods
Title
Detection of Mercury Through Surface Plasmon Resonance of Immobilized Gold Nanorods.
Creator
Trieu, Khang, Campiglia, Andres, Rex, Matthew, Heider, Emily, Frazer, Andrew, Harper, James, Bhattacharya, Aniket, University of Central Florida
Abstract / Description
Mercury is a known environmental pollutant that can damage the brain, heart, kidney and lungs upon exposure. Emissions from fossil fuel plants can release mercury into the air, where it can settle into the water supply and be exposed to human and aquatic life. The use of gold nanorods functionalized on solid substrates as a mercury sensor in tap water samples is investigated herein. The functionalization of the substrates involves the physical immobilization of the nanorods onto the solid...
Show moreMercury is a known environmental pollutant that can damage the brain, heart, kidney and lungs upon exposure. Emissions from fossil fuel plants can release mercury into the air, where it can settle into the water supply and be exposed to human and aquatic life. The use of gold nanorods functionalized on solid substrates as a mercury sensor in tap water samples is investigated herein. The functionalization of the substrates involves the physical immobilization of the nanorods onto the solid surface through the use of (3-mercaptopropyl)trimethoxysilane (MPTMS). The immobilization of the nanorods drastically increases their stability, allowing for use in complicated sample matrices. When gold nanorods are exposed to mercury in aqueous samples, their amalgamation to mercury metal causes a reduction of the effective aspect ratio of the nanoparticles and a blue shift of their maximum longitudinal surface plasmon resonance (SPR) absorption wavelength. Quantitative analysis is made possible due to the linear correlation that exists between the concentration of mercury and the wavelength shift of the maximum SPR absorption wavelength. In order to achieve the quantitative amalgamation of Hg (II) with the nanorods, it is necessary to reduce the mercury ions to mercury metal, which is accomplished herein via chemical or electrochemical processes. Chemical reduction of mercury was been carried out with a strong reducing agent, specifically sodium borohydride. Electrochemical reduction has been accomplished with gold nanorods immobilized on Indium Tin Oxide (ITO) substrates. Mercury determination in tap water using the immobilized gold nanorods was successfully conducted, with further experiments on improving selectivity with potential control, and improving sensitivity through flow injection analysis.
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Date Issued
2019
Identifier
CFE0007544, ucf:52604
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007544
The Schr(&)#246;dinger Equation with Coulomb Potential Admits no Exact Solutions
Title
The Schr(&)#246;dinger Equation with Coulomb Potential Admits no Exact Solutions.
Creator
Toli, Ilia, Zou, Shengli, Harper, James, Heider, Emily, Chen, Gang, Schulte, Alfons, University of Central Florida
Abstract / Description
We prove that the Schr(&)#246;dinger equation with the electrostatic potential energy expressed by the Coulomb potential does not admit exact solutions for three or more bodies. It follows that the exact solutions proposed by Fock are flawed. The Coulomb potential is the problem. Based on the classical (non-quantum) principle of superposition, the Coulomb potential of a system of many particles is assumed to be the sum of all the pairwise Coulomb potentials. We prove that this is not accurate...
Show moreWe prove that the Schr(&)#246;dinger equation with the electrostatic potential energy expressed by the Coulomb potential does not admit exact solutions for three or more bodies. It follows that the exact solutions proposed by Fock are flawed. The Coulomb potential is the problem. Based on the classical (non-quantum) principle of superposition, the Coulomb potential of a system of many particles is assumed to be the sum of all the pairwise Coulomb potentials. We prove that this is not accurate. The Coulomb potential being a hyperbolic (not linear) function, the superposition principle does not apply.The Schr(&)#246;dinger equation as studied in this PhD dissertation is a linear partial differential equation with variable coefficients. The only exception is the Schr(&)#246;dinger equation for the hydrogen atom, which is a linear ordinary differential equation with variable coefficients. No account is kept of the spin or the effects of the relativity.New electrostatic potentials are proposed for which the exact solutions of the Schr(&)#246;dinger equation exist. These new potentials obviate the need for the three-body force interpretations of the electrostatic potential.Novel methods for finding the exact solutions of the differential equations are proposed. Novel proof techniques are proposed for the nonexistence of the exact solutions of the differential equations, be they ordinary or partial, with constant or variable coefficients. Few novel applications of the established approximate methods of the quantum chemistry are reported. They are simple from the viewpoint of the quantum chemistry, but have some important aerospace engineering applications.
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Date Issued
2019
Identifier
CFE0007733, ucf:52422
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007733
Quantum Chemical Studies for the Engineering of Metal Organic Materials
Title
Quantum Chemical Studies for the Engineering of Metal Organic Materials.
Creator
Rivera Jacquez, Hector, Masunov, Artem, Balaeff, Alexander, Harper, James, Heider, Emily, Zou, Shengli, Kaden, William, University of Central Florida
Abstract / Description
Metal Organic Materials (MOM) are composed of transition metal ions as connectors and organic ligands as linkers. MOMs have been found to have high porosity, catalytic, and optical properties. Here we study the gas adsorption, color change, and non-linear optical properties of MOMs. These properties can be predicted using theoretical methods, and the results may provide experimentalists with guidance for rational design and engineering of novel MOMs. The theory levels used include semi...
Show moreMetal Organic Materials (MOM) are composed of transition metal ions as connectors and organic ligands as linkers. MOMs have been found to have high porosity, catalytic, and optical properties. Here we study the gas adsorption, color change, and non-linear optical properties of MOMs. These properties can be predicted using theoretical methods, and the results may provide experimentalists with guidance for rational design and engineering of novel MOMs. The theory levels used include semi-empirical quantum mechanical calculations with the PM7 Hamiltonian and, Density Functional Theory (DFT) to predict the geometry and electronic structure of the ground state, and Time Dependent DFT (TD-DFT) to predict the excited states and the optical properties.The molecular absorption capacity of aldoxime coordinated Zn(II) based MOMs (previously measured experimentally) is predicted by using PM7 Theory level. The 3D structures were optimized with and without host molecules inside the pores. The absorption capacity of these crystals was predicted to be 8H2 or 3N2 per unit cell. When going beyond this limit, the structural integrity of the bulk material becomes fractured and microcrystals are observed both experimentally and theoretically.The linear absorption properties of Co(II) based complexes are known to change color when the coordination number is altered. In order to understand the mechanism of this color change TD-DFT methods are employed. The chromic behavior of the Co(II) based complexes studied was confirmed to be due to a chain in coordination number that resulted in lower metal to ligand distances. These distances destabilize the occupied metal d orbitals, and as a consequence of this, the metal to ligand transition energy is lowered enough to allow the crystals to absorb light at longer wavelengths.Covalent organic frameworks (COFs) present an extension of MOM principles to the main group elements. The synthesis of ordered COFs is possible by using predesigned structures andcarefully selecting the building blocks and their conditions for assembly. The crystals formed by these systems often possess non-linear optical (NLO) properties. Second Harmonic Generation (SHG) is one of the most used optical processes. Currently, there is a great demand for materials with NLO optical properties to be used for optoelectronic, imaging, sensing, among other applications. DFT calculations can predict the second order hyperpolarizability ?2 and tensor components necessary to estimate NLO. These calculations for the ?2 were done with the use of the Berry's finite field approach. An efficient material with high ?2 was designed and the resulting material was predicted to be nearly fivefold higher than the urea standard.Two-photon absorption (2PA) is another NLO effect. Unlike SHG, it is not limited to acentric material and can be used development of in vivo bio-imaging agents for the brain. Pt(II) complexes with porphyrin derivatives are theoretically studied for that purpose. The mechanism of 2PA enhancement was identified. For the most efficient porphyrin, the large 2PA cross-section was found to be caused by a HOMO-LUMO+2 transition. This transition is strongly coupled to 1PA allowed Q-band HOMO-LUMO states by large transition dipoles. Alkyl carboxyl substituents delocalize the LUMO+2 orbital due to their strong ?-acceptor effect, enhancing transition dipoles and lowering the 2PA transition to the desirable wavelengths range.The mechanism 2PA cross-section enhancement of aminoxime and aldoxime ligands upon metal addition of is studied with TD-DFT methods. This mechanism of enhancement is found to be caused by the polarization of the ligand orbitals by the metal cation. After polarization an increase in ligand to ligand transition dipole moment. This enhancement of dipole moment is related to the increase in 2PA cross-sections.
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Date Issued
2015
Identifier
CFE0005990, ucf:50777
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005990