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Enhanced Raman spectroscopy: Gas analysis using a new type of multi-pass optical waveguide and surface -enhanced Raman spectroscopy of biologically relevant molecules

Posted on:2008-06-06Degree:Ph.DType:Dissertation
University:University of South CarolinaCandidate:Pearman, William FrederickFull Text:PDF
The work presented illustrates two separate techniques for increasing the overall sensitivity of Raman Spectroscopy; Multipass Capillary Cell (MCC) and Surface Enhanced Raman Spectroscopy. Initial results using silver coated quartz capillary tubing for the enhanced measurement of ambient-pressure gases using a fiber optic probe coupled to the MCC is presented. The use of a fiber optic bundle coupled to the MCC improved the detected Raman signal, both rotational and vibrational, by up to 30-fold. Expanding on these initial studies with the MCC, experiments to quantify its performance are presented. These quantification experiments resulted in the determination of the limits of detection for two separate gasses; CO2 and CH4.;The focus of this work then shifts to Surface Enhanced Raman Spectroscopy (SERS) with the analysis of biologically significant molecules. First, N-acyl-homoserine lactones, signaling molecules used in bacterial communication, are studied using SERS. The SERS spectra of seven different molecules within the AHL class were recorded for the first time at environmentally relevant concentrations using silver nano-particles. In other environmentally related work, SERS of saxitoxin, a highly lethal toxin produced by bacteria which are found in both fresh and salt water systems, is presented and discussed. SERS spectra are shown for STX at concentrations as low as 30 nM.;As a result of the presented work, the capability and applicability of Raman Spectroscopy as a tool for analytical spectroscopy is further advanced. Increasing the sensitivity of the Raman measurement of gases using the MCC presents opportunities for the remote detection and/or monitoring of diatomic gases in a closed system. SERS of the N-acyl-homoserine lactones provides an alternative path for the advancement of our understanding of the intricacies of inter-cellular bacterial communication. Finally, the SERS studies of saxitoxin provides a new capability for the rapid, on-site detection of this deadly toxin.
Keywords/Search Tags:Raman spectroscopy, SERS, MCC, Using, Presented, Surface, Molecules, Work
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