Chemistry Commons^™

The Development Of Fundamental Insights Into The Electronic Behaviors Of Next-Generation Materials, Sydney Lavan

Wayne State University Dissertations

We develop the fundamental mechanistic understanding of the microscopic behavior of three next generation materials: antiferroelectrics, hybrid perovskites and metal organic frameworks. These materials have the potential to be used in energy and light related applications which could provide a solution for the energy efficiency challenges we face in todays society. Ideally we need to begin to bridge the gap of developing candidate materials that possess high power density and high energy density. The first step in bridging this gap is understanding how the material influ- ences its structure and thus the properties and performance. We leverage vibrational spectroscopy and …

Electrochemical Gelation Of Metal Chalcogenide Quantum Dots, Chathuranga Chinthana Hewa Rahinduwage

Wayne State University Dissertations

Quantum dots (QDs) are attractive because of their unique size-dependent optical and electronic properties and high surface area. They are tested in research for diverse applications, including energy conversion, catalysis, and sensing. Assembling QDs into functional solid-state devices while preserving their attractive properties is a challenge. Methods currently under the research are not effective in directly fabricating QDs onto devices, making large area assemblies, maintaining the high surface area by forming 3D porous structures, and conducting electricity for applications such as sensing. QD gels are an example of QD assemblies that consist of a 3D porous interconnected QD network. They …

Parahydrogen Hyperpolarized Multi-Nuclear Contrast Agents For Potential Mri Applications, Nuwandi Maduranga Ariyasingha Uragoda Wiyannalage

Wayne State University Dissertations

ABSTRACT

PARAHYDROGEN HYPERPOLARIZED MULTI-NUCLEAR CONTRAST AGENTS FOR POTENTIAL MRI APPLICATIONS

by

NUWANDI M. ARIYASINGHA

December 2020

Advisor: Dr. Eduard Chekmenev

Major: Chemistry (Physical)

Degree: Doctor of Philosophy

There have been numerous studies to develop fast, cost effective hyperpolaried (HP) contrast agents with higher polarization values that can be potentially employed for magnetic resonance clinical imaging. Some of the currently used contrast agents are based on 129Xe hyperpolarized nucleus. However, one of the problems associated with this approach, is the high cost of the produced hyperpolarized contrast agents. In addition, the other important practical problem is that the currently used clinical …

Solvent Effects And Charge Transfer States In Organic Photovoltaics, Kangmin Liu

Wayne State University Dissertations

Due to their various advantages, including lightweight, flexible, and cheap manufacturing, organic photovoltaic materials have gained enormous research interest. Over nearly two decades, the power conversion efficiency of organic solar devices has increased dramatically. However, it is still low compared to traditional inorganic semiconductors. In order to improve efficiency, a better understanding of the basic thermodynamic properties of the light-to-electricity power conversion process is needed. One nontrivial aspect of organic solar cells is the low dielectric constant, which leads to tightly-bound excitons upon vertical excitations. The separation of electron-hole pairs requires a larger driving force to overcome the Coulombic binding …

Applications Of Molecular And Quantum Mechanical Methods For Studying The Chemical Reactions Of Inorganic And Organic Systems, Yi-Jung Tu

Wayne State University Dissertations

Computational studies can assist chemists to interpret experimental observations and to predict the properties and behaviors of molecules. The work presented in this dissertation applies different computational methods to study the molecular properties and reaction paths for various inorganic and organic systems. The second and third chapters discuss the force field development using “Gaussian Electrostatic Model (GEM)” and its amenability for use in the AMOEBA force field. The forth and fifth chapters discuss the density functional theory (DFT) studies of photodissociation behaviors for inorganic molecules. The sixth chapter explores the oxidation mechanisms of ascorbic acid and its antioxidant properties in …

3d Momentum Imaging Spectroscopy Probing Of Strong-Field Molecular And Surface Dynamics, Lin Fan

Wayne State University Dissertations

Electron-ion coincidence measurements in combination with 3-dimensional (3D) momentum imaging can provide comprehensive 3D-momentum information to unravel multichannel photoionization/dissociation processes, and thus is an effective tool to investigate atomic/molecular dynamics. A camera-based 3D coincidence momentum imaging system and the velocity mapping imaging (VMI) based machine were introduced in Chapter 2. Studies of strong field dissociative single and double ionization of relatively large molecules camphor and 2-phenylethyl-N, N-dimethylamine (PENNA) were carried out and illustrated in Chapter 3. We demonstrated the main products of double ionization of PENNA were singlet diradicals. In Chapter 4, a novel angle resolved-photoemission spectroscopy based on VMI …

Computational Study Of Transition Metal Complexes For Solar Energy Conversion And Molecular Interaction With Strong Laser Fields, Xuetao Shi

Wayne State University Dissertations

There are two topics in this dissertation: ground state and excited state modeling of a few series of transition metal complexes that facilitate solar energy conversion, and Born-Oppenheimer Molecular Dynamics (BOMD) simulations of molecular cations interacting with intense mid-infrared laser light.

In Chapter 2 and 3, a few series of transition metal complexes that facilitate solar energy conversion are studied computationally. Metal-to-ligand charge-transfer (MLCT) excited states of several (ruthenium) (monodentate aromatic ligand, MDA) chromophore complexes are modeled by using time-dependent density function theory (TD-DFT). The calculated MLCT states correlate closely with the heretofore unknown emission properties that were observed experimentally. …

Gas-Phase Ion Spectroscopy Of Nucleobases And Mononucleotides: Models For Higher Order Nucleic Acids, Yuan-Wei Nei

Wayne State University Dissertations

Experiments examining the structures and stabilities of protonated and sodium cationized nucleobases, and deprotonated DNA and RNA mononucleotides are presented and discussed in this dissertation. These studies were carried out using the infrared multiple photon dissociation (IRMPD) action spectroscopy technique that utilizes a Fourier transform ion cyclotron mass spectrometer (FT-ICR MS) coupled to a free electron laser (FEL) located at the Radboud University Nijmegen. Ionic species of these biologically important complexes were generated using an electrospray ionization source and then mass isolated to have their infrared (IR) spectra measured by the experimental apparatus. Detailed analysis of the IR spectra measured …

Exploring Potential Energy Surfaces Of Chemical Reactions Using Electronic Structure Methods, Bishnu Thapa

Wayne State University Dissertations

This dissertation includes three topics: molecular dynamics in strong laser fields, pKa’s and redox potential calculations of bio–organic molecules, and oxidative damage of the nucleobases. Electronic structure calculations are used to provide a deeper understanding of experimental observations as well as to predict new results.

Chapters 2, 3 and 4 investigate the fragmentation and isomerization reactions of small monocations in the presence of strong laser fields. In the presence of intense laser pulses with 800 nm wavelengths, Born-Oppenheimer classical trajectory simulations were performed to investigate the dynamics of methanol monocation on the ground state potential energy surface (Chapter 2). With …

Attosecond Spectroscopy Probing Electron Correlation Dynamics, Alexander Heinecke Winney

Wayne State University Dissertations

Electrons are the driving force behind every chemical reaction. The exchange, ionization, or even relaxation of electrons is behind every bond broken or formed. According to the Bohr model of the atom, it takes an electron 150 as to orbit a proton[6]. With this as a unit time scale for an electron, it is clear that a pulse duration of several femtoseconds will not be sufficient to understanding electron dynamics. Our work demonstrates both technical and scientific achievements that push the boundaries of attosecond dynamics. TDSE studies show that amplification the yield of high harmonic generation (HHG) may be possible …

How Geometric Distortions Scatter Electronic Excitations In Conjugated Macromolecules: Towards Photoinduced Relaxation And Energy Transfer, Tian Shi

Wayne State University Dissertations

The exciton scattering (ES) approach has been developed to study electronic excitations in large branched conjugated molecules. It attributes excited states to standing waves in the quasi-one-dimensional system by assuming a quasi-particle picture of optical excitations. Tight binding models extend capability of the ES approach to investigate the exciton-phonon coupling.

The topological counting method plays a substantial role in constructing tight binding models. It depicts the ES equations as a topological intersection problem. Then, by applying the index theorem, we can get the total number of excited states, which is equal to the number of repeat units plus topological charges …

State Resolved Sliced Imaging Of Infrared Multiphoton Dissociation, Ravin Lakshitha Fernando

Wayne State University Dissertations

This dissertation focuses on unimolecular dissociations of molecules under colissionless conditions with IRMPD. IRMPD was used as the dissociation technique in these studies since roaming type dissociations predominates from the ground electronic state. DC slice imaging was used with REMPI as the detection technique to study the products in a state selective manner to understand the nano scale dynamics of unimolecular dissociations. In the investigation of photodissociation dynamics of nitromethane and methyl nitrite with IRMPD, nitromethane show very low translational energy release of the photofragments and resemble the “roaming” pathway in the dissociation of nitromethane. The difference in the intensities …

Noncovalent Interactions Between Alkali Metal Cation And Aza/Thia-Crown Macrocycles: Mass Spectrometric Techniques And Theoretical Studies, Calvin A. Austin

Wayne State University Dissertations

Macrocyclic complexes have been useful in understanding many systems encountered in biology, along with having widespread use in analytical, pharmaceutical, and synthetic chemistry. My goal was to provide a quantitative experimental and theoretical description of cation-aza-crown and thia-crown ether interactions with alkali metal cations. Infrared multiple photon dissociation (IRMPD) action spectroscopy and energy-resolved collision-induced dissociation (CID) techniques were used in conjunction with theoretical electronic structure calculations to characterize the structures, binding interactions, and stability of cation-aza-crown ether interactions. Quantum chemical calculations at several levels of theory were employed to characterize the structures and stabilities of the isolated cations and aza-crown …

Classical And Ab Initio Qm/Mm Simulations Of Bacterial Enzymes, Sajeewa Walimuni Dewage

Wayne State University Dissertations

This thesis describes analyses performed on three enzyme systems. Chapter 2, 3, and 4 involve studies carried out on the GatCAB enzyme of H. pylori and S. aureus. Since information at the electronic level was not required for these studies, sampling of the configuration space carried out at the molecular mechanics level was adequate. In Chapter 2, the snapshots sampled using MD were used as input for average correlation difference calculations and average RMSD difference calculations to ascertain the existence of a communication pathway between two subunits of GatCAB. Experimental and computational results obtained, suggest the existence of a communication …

Rydberg Time-Of-Flight And Imaging Probes Of The Velocity-Dependent Hydrogen Atom Spin Polarization, Bernadette Michlewicz Broderick

Wayne State University Dissertations

Insights into electron spin and nuclei are central to the field of chemical reaction dynamics. Of particular note is the study of spin-polarized hydrogen (SPH) atoms, which result from photodissociation of molecules. Examination of the detailed H-atom spin polarization is achieved by determining the projection of the electron spin onto the probe laser direction. In doing so, its angular distribution, complex dissociation pathways, and coherent excitation mechanisms may be revealed. Approaches to detect SPH atoms are experimentally challenging due to the difficulty associated with probing ground-state H atoms through isolated fine structure levels, which is the only direct way to …

Exploring Molecular Systems From Chemical Physics To Biochemistry Using Classical And Quantum Mechanics, Brian Thomas Psciuk

Wayne State University Dissertations

Six topic are considered in this dissertation. Chapter 2 is an investigation into the role of ultra-fast hydrogen dynamics in determining fragmentation products of C3H4 following exposure to intense laser fields. Classical dynamics simulations were performed starting from C3H4 isomers with 190 - 240 kcal/mol excess energy distributed randomly as nuclear momenta. Deprotonation events were seen in ca. 50 - 75 % of all trajectories. Roughly one third of all trajectories showed fragmentation involving internal isomerization prior to dissociation. Chapter 3 is a survey of currently popular density functional methods and their ability to calculate accurate excitation energies and intensities …

Fundamental Studies And Applications Of Strong Field Ionization, Lu Yan

Wayne State University Dissertations

In an intense laser field, atoms and molecules experience tunneling ionization directly to the continuum. We used this method to study several aspects and applications of strong field ionization (SFI) in atoms and molecules. One study used SFI to probe the photofragments produced by photodissociation using DC sliced imaging. The photodissociation mechanism of two polyatomic molecules (sulfur dioxide and nitromethane) were investigated. In a second study, we show the strong field ionization rate depends on the sign of the magnetic number distribution. We detect the signal of sequential double ionization of argon dications by a pump-probe method to investigate the …

Applications Of Electronic Structure Theory To Problems In Strong-Field Chemistry, Inorganic Chemistry, And Nanomaterial Systems, Jason Anthony Sonk

Wayne State University Dissertations

This dissertation covers research performed on applications of electronic structure theory to various fields of chemistry and is divided into eight chapters. Chapters 2 through 4 describe a series of related works which explore applications of excited state electronic structure methods to problems in strong field chemistry. Chapters 5, 6, and 7 discuss the application of electronic structure theory methods to solving problems in inorganic chemistry. Finally, Chapter 8 looks at an application of electronic structure theory to nanomaterials.

Chapter 2 covers the modeling of electron dynamics of butadiene interacting with a short, intense laser pulse in the absence of …

State-Resolved Slice Imaging Of Photochemical Dynamics, Herath Mudiyans Nuradhika Herath

Wayne State University Dissertations

This dissertation focuses on the understanding the unimolecular photochemistry and dynamics

utilizing state-resolved slice imaging approach combined with the quantum-state selective

spectroscopy technique called resonance enhanced multi photon ionization (REMPI)

method. This powerful technique allows selecting the initial quantum states of the reactants

and determining the nal quantum states, energy, the orientation and alignments of

the products. In the investigations of photodissociation dynamics of acetone at 230 nm,

a bimodal distribution for the resulting CO photoproduct is identied. This observation

indicated the presence of unimolecular dissociation mechanism analogues to the roaming

dynamics reported in formaldehyde photodissociation. Moreover, another type of …

Probing The Dynamics Of Radical Reactions With Polyatomic Hydrocarbons By Crossed-Beam Dc Slice Imaging, Armando Dura Estillore

Wayne State University Dissertations

This work presents results of crossed molecular beam imaging studies on the reaction of radicals (Cl and CN) with polyatomic hydrocarbons of different functionalities such as pentane isomers, deuterated alkanes, alkenes, and alcohols. The reactively scattered alkyl radicals are probed as a function of collision energy using single photon ionization. The scattering results for pentane are quite similar for all reactants, suggesting that the nature of the abstraction site has surprisingly little influence on the dynamics studied at ~5 and ~9 kcal/mol. The angular distributions are broad with a backscattered peak at low collision energy and a sharp forward peak …

Electronic Excitations In Branched Conjugated Oligomers: A Quasiparticle View And Tight-Binding Models, Hao Li

Wayne State University Dissertations

This dissertation focuses on the theoretical understanding and simulation of the excited state electronic structures of organic conjugated molecules. The exciton scattering (ES) approach has been extended for efficient calculation of optical spectra of large branched conjugated oligomers. The methodology of tight-binding (lattice) model, originally developed in condensed matter theory, has been extended to the building block structure of conjugated molecules for explicit description of the electronic excitations.

Within the ES approach, the electronic excitations in quasi-1D molecular structures are attributed to standing waves that represent quantum quasiparticles (excitons) scattered at the molecular vertices. Excitation energies can be found by …

Laser-Assisted Single-Molecule Refolding, Rui Zhao

Wayne State University Dissertations

Non-coding RNAs must fold into precise secondary and tertiary structures in order to perform the biological functions. Due to the flexibility of RNA, the RNA folding energy landscape can be rugged and full of local minimum (kinetic trap). To provide a means to study kinetically trapped RNAs, we have developed a new technique combining single-molecule FRET detection with laser induced temperature jump. We have calibrated the magnitude of the temperature jump with 1˚C accuracy using gold micro-size sensor. The accuracy of temperature calibration was confirmed by close agreement between single-molecule and bulk DNA duplex melting experiments.

HIV 1 DIS RNAs …

Astrochemical Dynamics: Fundamental Studies Relevant To Titan's Atmosphere, Wilson Kamundia Gichuhi

Wayne State University Dissertations

This work presents results of primary fundamental photodissociation and state-specific ion-molecule dynamical studies that are relevant to understanding the formation and growth mechanisms of unsaturated hydrocarbon molecules, haze layers and aerosols in Titan's upper atmosphere. In the diacetylene dimer, it is shown, via laboratory studies combined with electronic structure calculations that the photodissociation of the dimer readily initiates atomic hydrogen (H) loss and atomic H transfer reactions forming two prototypes of resonantly stabilized free radicals, C8H3 and C4H3, respectively. In ethylamine cation, high-level ab initio calculations identify the complex dissociation pathways for the ground state CH3CH2NH2+ radical cation at 233.3 …

Photodissociation Dynamics In Titan's Atmosphere, Welvidanalage Ruchira Silva

Wayne State University Dissertations

Photodissociation dynamics of molecules relevant to understanding Titan's atmosphere (diacetylene, cyanoacetylene and heptane isomers) are carried out under collisionless condition using the DC slice imaging technique. In diacetylene photodissociation, two-photon processes dominate at 243 nm and 212 nm whereas at 121.6 nm, a one-photon dissociation process dominates. Direct measurement of the lifetime of metastable triplet diacetylene confirms sub-microsecond lifetimes. Photodissociation of cyanoacetylene at 193.3 nm proceeds on the S1 potential energy surface with an exit barrier. In heptane photodissociation, the dissociation occurs on the ground state or low-lying triplet states with nonradiative electronic relaxation. Time-of-flight mass spectroscopy studies in this …

Determination Of Size Distributions In Heterodisperse Systems Of Homogeneous, Non-Absorbing Spheres From Angular Light Scattering Extrema, Werner Bergman

Wayne State University Dissertations

No abstract provided.