Ivan Medvedev, Ph.D. (Advisor); Brent Foy, Ph.D. (Committee Member); Jason Deibel, Ph.D. (Committee Member)
Master of Science (MS)
A recently constructed novel analytical tabletop terahertz (THz) chemical sensor capable of detecting a wide range of gases with high sensitivity and specificity was characterized to assess its performance over a range of operational parameters. The sensor was designed with an objective of quantifying composition of exhaled human breath, where target concentrations span part per trillion (ppt) to part per billion (ppb) level of dilutions. The sensor utilizes terahertz rotational spectroscopy of sampled gases for quantification of dilutions. The sensor occupies a volume of ~ 2 ft3 and incorporates a coiled absorption cell, thermal desorption tubes, and all necessary electronic components necessary for autonomous operation. Coiled absorption cell minimizes the sensor footprint while maintaining a large path length for sensitive spectral measurements. Preconcentration aides the detection of compounds by removing the background gases which would negatively affect the absorption signal if present during spectral analysis. Spectral parameters of the sensor were studied to optimize its sensitivity. Efficiencies of preconcentration over a range of gas sampling parameters were determined by comparing concentrations measured by the sensor to concentrations of a reference gas mixture. The sensor was characterized in its ability to detect acetaldehyde, acetone, ethanol, isoprene, and methanol – all known breath analytes. These gases were chosen for their range of volatility and absorption strength. Minimum detectable sample concentrations are well suited for breath sampling making this sensor a valuable new tool for environmental sensing and biosensing.
Department or Program
Department of Physics
Year Degree Awarded
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