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Browsing Theses and Dissertations by Subject "2D IR spectroscopy"

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    Exploring nanoaggregate structures of model asphaltenes using two dimensional infrared spectroscopy
    (Colorado State University. Libraries, 2015) Cyran, Jenée D., author; Krummel, Amber T., advisor; Bernstein, Elliot, committee member; Levinger, Nancy, committee member; Borch, Thomas, committee member; Kreidenweis, Sonia, committee member
    Asphaltenes have been an enigma in the scientific community; studies on the molecular masses have differed by orders of magnitude and structures have been debated between island or archipelago structures. Thus, the asphaltene community defines asphaltenes by their solubility. Asphaltenes are n-heptane-insoluble and toluene-soluble. The known nanoaggregation of asphaltenes at different timescales and concentrations causes issues to determine the molecular weight and structure of asphaltene molecules. This thesis is the first step to using two dimensional infrared (2D IR) spectroscopy to study the nanoaggregate structure of model asphaltenes. 2D IR spectroscopy is a vibrational spectroscopy that is advantageous over linear IR absorption due to the ability to spread the spectral information over two axes. The 2D IR spectra give rise to structurally sensitive cross-peaks, affording the ability to probe the structure of the nanoaggregates. The model asphaltenes used in this work are violanthrone-79 and lumogen orange, a perylene derivative. These model asphaltenes consist mostly of polycyclic aromatic hydrocarbons (PAHs), similar to asphaltenes. Violanthrone-79 and lumogen orange also have carbonyl functional groups, which provide vibrational probes. The carbonyl stretching and ring breathing vibrations are used to probe the stacked structure of the nanoaggregates. A quinone series of one, two and three ring systems was used to first study the coupling between the carbonyl stretching and ring breathing vibrational modes. The quinone series provided the foundation for the larger ring systems that emulate asphaltenes. The data from studying the stacked structure of nanoaggregate model asphaltenes can be used to reveal properties of nanoaggregate asphaltenes. This work will allow for continued study of the kinetics of nanoaggregation using 2D IR waiting time experiments for dynamic information. Thus, this work demonstrates the use of 2D IR spectroscopy, which offers femtosecond time resolution, as a viable technique for studying nanoaggregation.
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    ItemOpen Access
    Visualizing dynamics using 100 kHz 2D IR spectroscopy and microscopy
    (Colorado State University. Libraries, 2018) Tracy, Kathryn Marie, author; Krummel, Amber T., advisor; Levinger, Nancy E., committee member; Szamel, Grzegorz, committee member; Krueger, David A., committee member; Fisk, John D., committee member
    2D IR spectroscopy is a nonlinear optical method with the ability to characterize condensed phase chemical systems. It offers information regarding structure and dynamics of chemical systems. Recent efforts have been made to resolve spatially the molecular structure and dynamics of heterogeneous samples, which shows the feasibility of ultrafast 2D IR microscopy. To image more efficiently, we have moved away from the Ti:sapphire based laser systems and OPA systems that operate at one to several kHz typically used in 2D IR spectroscopy. Instead, for the first time we have demonstrated higher repetition rate, 2D IR spectroscopy at 100 kHz. Achieving this higher repetition rate was accomplished by utilizing advances in diode pumped ytterbium oscillators and amplifiers, and is based on an OPCPA utilizing Mg:PPLN followed by DFG in ZGP. Using this system, we have for the first time, demonstrated the interfacing of IR compatible microfluidics with 2D IR spectroscopy to examine the solvatochromic pseudo-halide anion, cyanate in cosolvent environments. This high repetition rate source also provided a path to 2D IR microscopy experiments that explore the dynamics of complex, heterogeneous, chemical systems. We have shown the chemical dynamics in a room temperature ionic liquid microdroplet. Spatially resolved time-dependent 2D IR signals reveal three regions with different chemical dynamics—the bulk, the interface, and a region between the bulk and interface. This demonstration provides proof-of-concept to use 2D IR microscopy on a wide array of additional chemical systems.