INVESTIGATION OF THE STRUCTURAL AND OPTICAL PROPERTIES OF XANTHENE DYES FOR ANALYTE DETECTION AND THIN FILM SENSOR DEVELOPMENT

Chapter 1 Abstract: The effect of structure on the photophysical properties of six xanthene dye thin films: Rh560, Rh19, Rh6G, RhB, Rh3B, and Rh640 is investigated. The absorption spectra of all six dyes exhibit bathochromic shifts as the thickness of the thin film is increased. Bathochromic shifts are also seen in the emission spectra of the thin films with increased thickness. These shifts are attributed to the formation of J-dimers as the concentration of the casting solution increases. The quantum yields of the thin films are greatly reduced compared to the quantum yield values in aqueous solutions. Chapter 2 Abstract: Detection of diethylamine and hydrogen peroxide via rhodamine dye fluorophores was determined. Rh640 showed little response to either analyte while Rh700 showed response to both hydrogen peroxide and diethylamine, and Rh800 showed strong response to diethylamine but little response to hydrogen peroxide. Rh700 and Rh800 both show promise as “turn-off” sensors for the detection of analytes. The enhanced responsiveness of the Rh700 and Rh800 dyes when compared to the Rh640 dye is attributed to the increased reactivity of the lower substituent group on the xanthene dye backbone of the fluorophore. Chapter 3 Abstract: The application of a three-layer sensor to the detection of hydrogen peroxide, acetone, isopropyl alcohol, ethylamine, propylamine, butylamine, diethylamine, and triethylamine is investigated. Post exposure to analyte all three xanthene dyes used in the sensor creation (Rh640, Rh700, and Rh800) showed strong response to amine analytes in both absorbance and emission spectra. Rh700 and Rh800 showed stronger response to analytes than did Rh640. In the presence of primary amines Rh800 sensors exhibited the formation of new peaks in absorbance and emission spectra accompanied by the loss of the Rh800 fluorophore peak associated with the conversion of the carbon 9 group from a nitrile to a secondary amine