Date of Award

Fall 2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

R. Graham Cooks

Committee Chair

R. Graham Cooks

Committee Member 1

Mary J. Wirth

Committee Member 2

Chittaranjan Das

Committee Member 3

Peter T. Kissinger

Abstract

Various aspects of the interaction of low-temperature plasma (LTP) ambient ionization with organic molecules and surfaces are discussed. As an application, LTP-MS has been used for the analysis of pesticides directly from fruits and vegetables revealing low parts per billion limits of detection (LODs). Due to low power and gas requirements, a battery-operated and handheld LTP probe was developed for the point-and-shoot MS analyses. Handheld LTP was compared with large-scale LTP on a benchtop and miniature MS revealing similar LODs for both. Long-distance ion transport up to one meter was also demonstrated with flexible tubing for non-proximate sample interrogation. Fundamentals of LTP-sample interaction were examined through spectroscopy and MS analysis. Spectroscopic studies have provided insights into reagent ion formation, with new evidence that He2+ acts as a charge carrier in the plasma. In addition, monochromatic and time-resolved 2D images of LTP emission from plasma bullet propagation to open air and various sample substrates were acquired. MS analyses revealed chemical sputtering from alkyl halides and organic salts. Chemical sputtering that occurs in the LTP environment appears to be a reductive cleavage process and has resulted in two interesting reactions. More specifically, imidazolium-based ionic liquids have been found to selectively lose one of the two side chains as a function of the counter anion, and a partially fluorinated polymer was broken down into tetrafluoroethylene monomers which immediately polymerized to form perfluorinated alkyl chains.

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