Raman spectroscopy and surface enhanced Raman spectroscopy of catalysts, physiological analytes and cancer drugs
This thesis describes experimental Raman and Surface Enhanced Raman (SERS) studies as well as theoretical Raman calculations of various analytes, designed to gain a greater chemical understanding of their associated systems. Propylene epoxidation gold/titania catalysts are examined first. These catalysts are thought to be able to directly convert propylene to propylene oxide in one step, with high selectivity and reactivity. After catalyst synthesis and characterization, adsorbate probe molecules are utilized in order to determine whether SERS can be used to probe chemical interactions between the catalysts and the gases of interest: propylene, oxygen and hydrogen. An enhancement effect is observed for benzenethiol but oxygen- and hydrogen-related peaks are too weak to be of use. Five physiological fluids are then examined with SERS using colloids in order to be able to detect their presence in urine. Silver and gold colloids are synthesized and combined in varying ratios with the individual analytes and the aggregating agent spermine. This molecular-assembly system allows for detection of the fluids on the order of 10−4 M. Lastly, cancer drugs and their precursors are examined with Raman spectroscopy to promote further understanding of how they conform and interact with their aqueous environments. Drug solutions were deposited on steel substrates and allowed to evaporate to solidified residues. Detection limits of these deposits were on the order of 10−6 M. Quantum mechanical calculations of two of the analytes were also performed at the Hartree-Fock level, resulting in a high level of agreement with the experimentally derived spectra.
Ben-Amotz, Purdue University.
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