Theses and Dissertations
ORCID
https://orcid.org/0000-0001-6790-4846
Issuing Body
Mississippi State University
Advisor
Zhang, Dongmao
Committee Member
Wipf, David O.
Committee Member
Mlsna, Todd E.
Committee Member
Stokes, Sean L.
Committee Member
Gwaltney, Steven R.
Date of Degree
12-13-2024
Original embargo terms
Complete embargo 2 years
Document Type
Dissertation - Open Access
Major
Chemistry
Degree Name
Doctor of Philosophy (Ph.D.)
College
College of Arts and Sciences
Department
Department of Chemistry
Abstract
Optical spectroscopic techniques are critical for quantifying and characterizing diverse chemical compounds, from small molecules to macromolecules. Their versatility and cost-effectiveness have led to widespread use in fields such as medical diagnostics, industrial quality control, environmental monitoring, and chemical analysis. However, UV-vis spectrophotometry and fluorescence spectroscopy face significant challenges due to the complexity of light-matter interactions. These interactions often occur simultaneously and at overlapping wavelengths, complicating the accurate separation and quantification of absorption, scattering, and emission, particularly in complex samples. A fundamental issue with conventional UV-vis spectrophotometry is the interference from light scattering in turbid samples. Both scattering and absorption contribute to overall light extinction, and conventional instruments cannot quantitatively separate these two components. To address this, we developed an integrating-sphere-assisted resonance synchronous (ISARS) spectroscopy method using readily available spectrofluorometers equipped with integrating-sphere accessories. After calibration, this method can reliably decouple UV-vis extinction into its scattering and absorption spectra, allowing for accurate measurement of each component in complex samples. We also explored the effects of self-absorption, known as the inner-filter effect (IFE), on solution samples. The traditional model for IFE correction often fails, even in simple cases. To solve this, we derived a first-principles model to link the fluorescence measured by a spectrofluorometer with the UV-vis absorbance recorded by a conventional spectrophotometer. We applied this model with total photoluminescence spectroscopy to examine temperature effects on photoluminescent materials. In doing so, we could quantify quantum yield changes under different stimuli using a conventional spectrofluorometer for the first time. Finally, building on the insights from these studies, we developed a new instrument to address limitations in commercial instrumentation. The custom instrument integrates a thermoelectric-cooled CCD that can reach -90°C, significantly improving sensitivity and reducing noise. The advantages of this high-quality, low-temperature CCD are substantial, greatly enhancing the versatility, speed, and wavelength range of detection, not only refining current optical spectroscopic techniques but also enabling the development of new methodologies, thanks to its ability to acquire multiple spectra simultaneously, addressing many of the limitations of traditional instruments and paving the way for the development of new, customizable methodologies.
Recommended Citation
Wamsley, Max Christian, "Instrument and methodology development for expanding the capabilities of optical spectroscopic techniques" (2024). Theses and Dissertations. 6407.
https://scholarsjunction.msstate.edu/td/6407