Spectroscopic and Computational Investigation of Polymer Coatings and Analyte Systems for Use with Guided Shear Horizontal Surface Acoustic Wave (SH-SAW) Sensors for Liquid Phase Detection
Date of Award
Dissertation - Restricted
Doctor of Philosophy (PhD)
In recent years, there has been considerable interest in the development of advanced sensor technology. With growing concerns of the effect of various chemical contaminants and environmental toxins on human health and the ever-present threat of (bio-)chemical terrorism, there exists a need for sensor devices which can detect hazardous agents present in the environment. The goal of this work is to explore technology related to the design of field-portable, real-time sensors for detection of hazardous compounds in liquid environments-specifically the design and function of chemically sensitive polymers as coating materials for guided shear horizontal surface acoustic wave (SH-SAW) sensor devices in liquid phase detection. Through fundamental investigation of the interactions of polymer coatings with model analytes, and the effects of physical properties of coating materials on sensor response, insight is gained which may be applied toward the development or selection of coatings that target specific toxins or classes of toxins. Chapter 1 gives a general introduction to the motivation for the research as well as the background for the methodologies which are employed in this work. In Chapter 2, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to study the partitioning of analytes from water into a series of polymer coatings. The trends observed in this study were compared with the response of polymer coated guided SH-SAW sensor devices and calculated partition coefficients. The physical properties of a coating can have significant effect on the overall sensor response of the guided SH-SAW sensor. Results are presented from experiment and ·theoretical predictions in Chapter 3, which demonstrate the effect that changes in polymer viscoelasticity upon exposure to analyte molecules may have on sensor response. ATRFTIR spectroscopy was also used as a tool to investigate the fundamental interactions of analyte molecules with their local environment. This technique, in addition to UVVisible spectroscopy and computational chemistry calculations, was used to study the solvent effect on key vibrational modes of a series of nitroaromatic molecules. This approach provides insight into the strength of intermolecular interactions between the coating and analyte, which may be exploited in future studies to tailor sensor coatings that are specific to targeted analytes. Results of this study are presented in Chapter 4.