Physical Chemistry Commons^™

Investigating The Dynamics And Fragmentation Of Nitroaromatic Radical Cations Through Femtosecond Time-Resolved Mass Spectrometry And Computational Chemistry, Hugo Andres Lopez Pena

Theses and Dissertations

Chemists have sought to control molecular dissociation with lasers for decades. Effective control of unimolecular dissociation was only achieved with the development of high-intensity ultrashort pulsed lasers and coherent control techniques that operate on timescales faster than vibrational energy redistribution. In view of this, our lab has specialized in the study of polyatomic radical cations using femtosecond time-resolved mass spectrometry (FTRMS). The interest in radical cations stems from the fact that they are highly reactive species that contribute to many physical, chemical, and biological processes. For instance, radical cations participate in shock initiation of detonated energetic materials used as explosives …

Using Superatomic Clusters And Charge Transfer Ligands To Control Electronic Characteristics Of Phosphorene Nanoribbons And Phosphorene Monolayer, Ryan Lambert

Theses and Dissertations

Phosphorene is a two-dimensional electron poor p-type semiconductor with high carrier mobility and great promise for applications in electronics and optoelectronics. As the main theme in this dissertation, the following work represents different investigations of various electronic properties associated with phosphorene. Most notable are the findings on charge transfer doping with metal-chalcogenide superatoms which displays novel control of the two most important properties of a semiconductor – the band gap energy and the nature of carriers. By tuning the width of the gap and p-/n-type character of conduction, we gain control over a material’s capacity to play a certain role …

Developing Novel Femtosecond Time-Resolved Mass Spectrometry Techniques For Analysis Of Energetic Materials, Shane L. Mcpherson

Theses and Dissertations

Energetic materials and the unimolecular dissociation dynamics attributed to their initiation and subsequent bimolecular detonation have been a subject of interest for defense agencies such as the Department of Defense (DoD) for decades. The timescale in which these initial dynamics exist ranges from several picoseconds to dozens of femtoseconds, necessitating equally fast time-resolved experiments to capture and characterize these events. Our lab specializes in one such laser-based technique: femtosecond time-resolved mass spectrometry (FTRMS). FTRMS is an essentially nondiscriminatory pump-probe laser technique with nearly infinite modifications via pulse shaping, intensity, and wavelength modulation that can readily examine previously undefined dissociation pathways …

Translating Chemistry, Structure, And Processing To The Solid-State Morphology And Function Of Organic Semiconductors Through Computational Modeling And Simulations, Chamikara D. Karunasena

Theses and Dissertations--Chemistry

The immense synthetic design space and material versatility have driven the exploration and development of organic semiconductors (OSC) over several decades. While many OSC designs focus on the chemistries of the molecular or polymer building blocks, a priori, multiscale control over the solid-state morphology is required for effective application of the active layer in a given technology. However, molecular assembly during solid-state formation is a complex function interconnecting the building block chemistry and the processing environment. Insufficient knowledge as to how these aspects engage, especially at the atomistic and molecular scales, has so far limited the ability to predict …

Developing And Deploying Data-Driven Tools For Accelerated Design Of Organic Semiconductors, Vinayak Bhat

Theses and Dissertations--Chemistry

Organic semiconductors have gained widespread attention due to their potential applications in flexible, low-cost, lightweight electronics, energy storage and generation technologies, and sensing applications. However, developing new organic semiconductors with improved performance remains a significant challenge due to the vast chemical space of possible molecular and materials structures. Furthermore, the high cost and time-consuming nature of experimental synthesis and characterization hinder the rapid discovery of new materials. To overcome these challenges, this dissertation presents a data-driven approach to organic semiconductor discovery. The primary focus of this work is the development of data-driven tools, namely machine learning models, to predict critical …

Surface Modification Of Carbon-Based Electrodes For Electrochemical Conversion Processes: Oxygen Reduction Reaction And Bicarbonate Conversion, Udari Shyamika Kodithuwakku Arachchige

Theses and Dissertations--Chemistry

Oxygen reduction reaction (ORR) and conversion of bicarbonate into value-added chemicals are two significant electrochemical processes for energy storage and conversion. ORR is an important electrochemical reaction in fuel cells and metal-air batteries that provide power conversion and storage capacity, respectively, for portable electronics, and electric vehicles. However, the performance of catalysts (e.g., platinum-based) is critically limited by slow kinetics, inefficient four-electron pathway, and surface deactivation. This limited performance of platinum-based catalysts, the scarcity of platinum, and vulnerable supply chains for critical minerals require the development of alternative electrocatalysts now more than ever. Carbon-based materials possess several key properties that …

Water-Soluble Palladium, Copper, And Nickel Catalysts And Their Formation In Ligand-Free Suzuki-Miyaura Cross-Coupling Reactions, Priya Karna

Theses and Dissertations--Chemistry

Transition-metal catalyzed Suzuki-Miyaura (SM) cross coupling is a powerful synthetic method for constructing carbon-carbon and carbon-heteroatom bonds in designing organic compounds, agrochemicals, pharmaceuticals, and precursors for materials. However, the nature of catalysis and identity of the transition metal catalysts used in these reactions remain under debate or unknown. This dissertation reports the studies of three metals: Pd, Cu, and Ni. Pd-nanocluster catalysts and their formation in ligand-free SM reactions with Pd(II) nitrate as a precatalyst was investigated. The catalysts are water-soluble neutral Pd tetramer and trimer in their singlet electronic states as identified by UV-Vis absorption spectroscopy and are formed …

First Principles Calculations To Investigate Surface And Catalytic Properties Of Materials For Green Energy Generation, Keerthan Raghavendra Rao

Theses and Dissertations--Chemistry

Climate change due to greenhouse gas build up in the earth’s atmosphere is an existential threat to humanity. To mitigate climate change, a significant shift from fossil fuels is necessary. Over the years, several renewable energy sources like solar, wind, geothermal etc. have been explored with the aim providing carbon-free energy. In this work, we focus on using density functional theory (DFT) methods to investigate key functional properties of materials of interest for applications in solar cells and catalytic conversion for energy generation. We show geometric effects of carboxylic acid binding on a transition metal surface to impact the deoxygenation …

Outstanding Advantages, Current Drawbacks, And Significant Recent Developments In Mechanochemistry: A Perspective View, Silvina Pagola

Chemistry & Biochemistry Faculty Publications

Although known since antiquity, mechanochemistry has remained dormant for centuries. Nowadays, mechanochemistry is a flourishing research field at the simultaneous stages of gathering data and (often astonishing) observations, and scientific argumentation toward their analysis, for which the combination of interdisciplinary expertise is necessary. Mechanochemistry’s implementation as a synthetic method is constantly increasing, although it remains far from being fully exploited, or understood on the basis of fundamental principles. This review starts by describing many remarkable advantages of mechanochemical reactions, simplifying and “greening” chemistry in solutions. This description is followed by an overview of the current main weaknesses to be addressed …

More On The Demons Of Thermodynamics, Daniel P. Sheehan, Garret Moddel, James W. Lee

Chemistry & Biochemistry Faculty Publications

No abstract provided.

S-Type Stars: Line List For The A²Π-X²Σ⁺ Band System Of Lao, P. F. Bernath, R. Dodangodage, J. Liévin

Chemistry & Biochemistry Faculty Publications

LaO bands are found in the spectra of cool S-type stars. The bands of the A²Π–X²Σ⁺ transition with v' ⩽ 3 and v'' ≤ 4 are rotationally analyzed, providing spectroscopic constants for the A²Π state. Line strengths are calculated using an ab initio transition dipole moment function, and radiative lifetimes for the A²Π state have also been computed. A line list for the A²Π–X²Σ⁺ transition of LaO is provided and can be used to determine LaO stellar abundances.

Investigation Of Ch4 Adsorption And Activation On Modified Metalloporphyrin Graphene Sheets, Brianna Haase

Masters Theses

Finding a good catalyst for C-H bond breaking is important due to the rise of natural gas and crude oil emissions. From 2000-2006, CH4 emission concentrations stabilized, but in 2007, it sharply started increasing again. For example, atmospheric CH₄ levels were 1886.37 ppb in July 2021 but this rose to 1904.52 ppb in just one year. Precious metal catalysts, such as Ir systems, have been used for C-H bond breaking, but are not sustainability ideal as they are costly to produce and have a significant carbon footprint. Because of this, less expensive 3d metal catalysts have risen in investigative …

Fluorination Of Rubisco-Mimetic Co2 Capture Systems. Theoretical And Experimental Studies Of Ammonium Ion Acidity Depression And Carbamylation, Brian Michael Jameson

Doctoral Dissertations

"RuBisCO-inspired CO₂ capture and release (CCR) systems featuring amines have been developed for the purpose of reversable CO₂ capture from air. The enzyme active site consists of the tetrapeptide sequence Lys-Asp-Asp-Glu. The Lys sidechain amine undergoes carbamylation and an Mg²⁺ cation stabilizes the resulting carbamate. The N^a-acyl-lysinyl-aspratyl-aspartyl-glutamide (Lys-Asp-Asp-Glu, KDDE) peptide featured maximum capture at pH ≈ 10; a pH region too high for Mg²⁺ ions to remain in solution. This work aims to achieve pKa depression by introducing fluorine in the proximity of the lysine’s sidechain amine. A comparative analysis was made of butylamine, …

Temperature Dependence Of The Electronic Absorption Spectrum Of No2, Steve Ndengué, Ernesto Quintas Sánchez, Richard Dawes, Christopher C. Blackstone, David L. Osborn

Chemistry Faculty Research & Creative Works

The nitrogen dioxide (NO₂) radical is composed of the two most abundant elements in the atmosphere, where it can be formed in a variety of ways including combustion, detonation of energetic materials, and lightning. Relevant also to smog and ozone cycles, together these processes span a wide range of temperatures. Remarkably, high-resolution NO₂ electronic absorption spectra have only been reported in a narrow range below about 300 K. Previously, we reported [ J. Phys. Chem. A 2021, 125, 5519−5533 ] the construction of quasi-diabatic potential energy surfaces (PESs) for the lowest four electronic states (X̃, Ã, B̃, …

Mechanistic Studies Of Co2 Electrochemical Reduction (Co2er) On Cu And Cuo Nanoparticles With In-Situ Atr-Ftir Spectroscopy, Jason Hsu

Theses and Dissertations (Comprehensive)

Global climate change is a major challenge facing the world in the 21st century. This environmental crisis originated from excess amounts of atmospheric carbon dioxide (CO2) released from burning fossil fuels. One promising remediation method to decrease atmospheric CO2 levels is called carbon dioxide electrochemical reduction (CO2ER). In CO2ER, the CO2 gas undergoes chemical reduction to other hydrocarbon fuels. For CO2ER to take place, an energy source and a catalyst are needed. In this thesis, three aspects of CO2ER were investigated using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy coupled with other surface sensitive characterization tools. First, we studied …

Phosphorus Release And Recovery From Simulated Ferric Wastewater Sludge, Aseel Alnimer

Theses and Dissertations (Comprehensive)

Phosphorus (P) is a fundamental element necessary for all life forms and a key component in the fertilizer industry. Meanwhile, the excessive load of P to water bodies due to human activities has the potential to promote eutrophication. Wastewater treatment plants remove P either biologically or chemically and produce P rich sludge which could be a potential renewable source for P. At present, commercial technologies exist for P recovery from biological wastewater sludge. However, P recovery from chemical sludge particularly iron(III)-phosphate (Fe-P) sludge generated in chemical P removal plants that use iron(III) salts remains a challenge.

This study explored, in …

Molecular Organic Photovoltaic Cells And Applications, Julie Liu

Theses and Dissertations

The absorption, light scattering, and anti-Stoke’s fluorescence of chlorophyll and closely related sodium copper chlorophyllin were examined in various solutions with a wide range of refractive index and permittivity. It was evident that radiative photo electron decay corresponded to low permittivity solvents, but not to solvent refractive index. Additionally, non-radiative decay was dominant in high permittivity solvents. The properties suggest evolution has provided plants with an ability to redirect light to the chlorophyll in the high permittivity (water) photosynthesis center. Exploratory solar cells exploiting lifetime switching were developed and tested, wherein strong photovoltaic response was exhibited, along with the unique …

Investigation Of Early Complex Formation Of Huntingtin Protein With And Without Lipids, Alyssa R. Stonebraker

Graduate Theses, Dissertations, and Problem Reports (ETD)

Huntington’s disease (HD) is a fatal neurodegenerative disease caused by the expansion of the polyglutamine (polyQ) domain of the huntingtin protein (htt). The expansion of the polyQ domain beyond a threshold of approximately 35 repeats triggers complex toxic aggregation mechanisms and results in altered interactions between htt and lipid membranes. Many factors modulate these processes. One such modulator includes sequences flanking the polyQ domain, most notably the first 17 amino acids at the N-terminus of the protein (Nt17), and environmental factors including the presence of membranous structures. Nt17 has the propensity to form an amphipathic a-helix in the presence of …

Application Of Computational Biophysics Techniques To Characterize Cell Membrane-Associated Events, Kyle Billings

Graduate Theses, Dissertations, and Problem Reports (ETD)

Cell membranes are crowded environments which can modulate protein structure-function relationships through interaction with lipids, other proteins, carbohydrate structures and so on. This work focuses the impact of the membrane environment on two varieties of peptides: Microbial rhodopsin proteins, and cyclic peptides.

Life on Earth is dependent on the ability of plants and microbes to harness sunlight for energy production. Their ability to transform light into carbohydrates requires tailor-made machinery, and for a wealth of microorganisms, microbial rhodopsin proteins (MR) are critical for maintaining the concentration gradients used to produce the energy molecule Adenosine triphosphate (ATP). The central retinal molecule …

Solid State Nmr Analysis Of Insect Wing Membranes, Samuel Eddy

Graduate Theses, Dissertations, and Problem Reports (ETD)

Solid State NMR is a powerful tool for analyzing the chemical composition of insects. Previous studies have used Solid State NMR to investigate the chemical composition and investigate the sclerotization (tanning) process of insect exoskeletons. Acquiring sufficient exoskeleton sample for analysis has been relatively simple. This is however not the case for other components of an insect’s physiology, particularly the wing membrane material. The wings of an insect only compose a small percentage of their overall body mass, and many hundreds to thousands of insects must be processed in order to achieve a few milligrams of wing membrane sample. The …

Impact Of Sample Conditions On Dna Phosphodiester Backbone Bi/Bii Conformational Equilibrium Dynamics, Autumn C. Pilarski

Graduate Theses/Dissertations

DNA damage, such as single base lesions and mismatches, is highly prevalent within cells. If these DNA damage events are not repaired, they could lead to mutations and thus disease and cancer. Intricate repair mechanisms are in place to fix these damage events, one such being Base Excision Repair (BER) and associated enzyme: Thymine DNA Glycosylase (TDG). The first step of this repair process, recognition of the lesion by TDG, is not well understood. The following thesis presents results to better understand the fundamental biophysical question of how a DNA lesion within a mismatch context is recognized in a million …