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Full-Text Articles in Physical Sciences and Mathematics
Driving Piezochromism And Metallicity In Van Der Waals Materials Under Compression, Nathan Harms
Driving Piezochromism And Metallicity In Van Der Waals Materials Under Compression, Nathan Harms
Doctoral Dissertations
Complex chalcogenides provide an important platform to explore the interplay between structure, charge, and spin across pressure-induced phase transitions. Where much of the previous research has been focused on tuning these materials towards the single-layer limit, we instead explore the modification of bond lengths and bond angles under compression. In the first project we revealed piezochromism in MnPS3. We combined high pressure optical spectroscopy and first-principles calculations to analyze the dramatic color change (green → yellow → red → black) that takes place as the charge gap shifts across the visible and into the near infrared region, moving …
Monitoring Bacteria Cultures Using Near Infrared (Nir) Binary Spectronephelometry (Bsn), Raman Spectra And Principal Component Analysis (Pca), Steven Ortiz
Dissertations - ALL
Current noninvasive methods cannot continuously and simultaneously monitor the concentrations of cells and media components that define the state of native bacterial cultures, because of changing turbidity. A new technique, binary spectronephelometry (BSN) has the same or better sensitivity and precision for population monitoring as optical density at 600nm (OD600), while simultaneously measuring metabolic processes. The BSN algorithm uses laser induced emission to probe mildly turbid media i.e., propagation of light occurs in the single scattering regime. A BSN "training set" associates a grid of elastic emission measurements, comprising Rayleigh and Mie scattering, and inelastic emission measurements, comprising fluorescence and …
The Exploration Of Small Molecules, Lanthanide Complexes, And Catalysis Using Electronic Structure Theory, Dynamics, And Machine Learning, Gavin Mccarver
The Exploration Of Small Molecules, Lanthanide Complexes, And Catalysis Using Electronic Structure Theory, Dynamics, And Machine Learning, Gavin Mccarver
Doctoral Dissertations
With the ever increasing availability of computational resources, more challenging chemical systems can be studied. Among these challenges are the rotational and vibrational spectra of diatomic molecules within spectroscopic accuracy, the environmental perturbations induced on a rotating water molecule, the prediction of free binding energies of lanthanide complexes using machine learning, and the study of catalytic mechanisms through a theoretical framework. High levels of electronic structure theory were combined with a rigorous treatment of either the anharmonic vibrational wave functions to study diatomic molecules or the rotational wave functions to study H2O-pH2 interactions. The former was initially …
Approaches In Molecular Engineering To Optimize The Desired Properties Of Photoactive Molecules, Douglas Joseph Breen
Approaches In Molecular Engineering To Optimize The Desired Properties Of Photoactive Molecules, Douglas Joseph Breen
Chemistry and Chemical Biology ETDs
Within this dissertation, photochemical systems that bear significance to next-generation photonic materials and devices are explored. Notable advances in the design, synthesis, and characterization of three distinct groups of photoactive molecules are achieved through molecular design and spectroscopic analysis. First, novel ruthenium sulfoxide complexes bearing substituted phosphine ligands are found to provide extraordinary control over photoisomerization quantum yields. A comparison of these complexes reveals ground-state characteristics that are instrumental in this reactivity, while a novel spectroscopic technique provides rare structural evidence for an O-bonded metastable isomer. Ruthenium complexes bearing chelating carbene-sulfoxide ligands rapidly thermally revert from the O-bonded metastable isomer …
Infrared Investigation Of Lithium Ion Electrolytes: Characterization Of Structure And Dynamics Via Linear And Nonlinear Spectroscopy, Jeramie Christopher Rushing
Infrared Investigation Of Lithium Ion Electrolytes: Characterization Of Structure And Dynamics Via Linear And Nonlinear Spectroscopy, Jeramie Christopher Rushing
LSU Doctoral Dissertations
Lithium ion batteries are widely employed in energy storage, but the connection between the molecular interactions in their electrolytes and the macroscopic properties remains elusive. Across three vastly different electrolytes, speciation and dynamics were studied via linear and nonlinear infrared spectroscopy to shed light on this relationship. The impact of mixed solvation on ionic speciation was studied from the perspective of the anion, which revealed a significant energetic favorability for the formation of contact ion pairs in linear carbonate solvents over cyclic carbonates. Infrared spectroscopy and density functional theory calculations described a complete inversion of the speciation due to solvent …