Doctor of Philosophy (PhD)
Materials incorporating fluorescent π-electron conjugated molecular species for sensing and imaging are advantageous over other detection or identification methods such as colorimetric reporters. Fluorescent materials offer easy recognition of binding events due to the highly sensitive nature of fluorescence techniques down to the single molecule level. The properties of fluorescent molecules allow for rapid attenuation of observable readout due to the facile transport of excited state energy via both inter- and intramolecular pathways. This dissertation primarily focused on the development and study of a general platform for ratiometric fluorescent chemosensing using surface-immobilized oligomers, as well as in depth explorations of the unique properties of the chemosensors utilizing this platform. It encompasses bichromophoric fluorescent energy transfer cassettes consisting of a mono-disperse conjugated oligomer and a red-shifted energy transfer acceptor that is specifically reactive on the presence of a chosen analyte. Molecular organization of these cassettes into a surface- immobilized monolayer lends excellent and advantageous properties to the devices for sensing purposes primarily due to enhanced efficiency of intermolecular energy transfer within the monolayer. Several intriguing properties of this class of sensing devices are described, as well as how these properties, such as the effect of exciton delocalization and spatial control of energy transfer efficiency can be harnessed to generate practical chemosensing films that undergo significant emission wavelength (color) shift upon analyte exposure. The fundamental properties of this strategy toward ratiometric fluorescent chemosensing are described as applied to the measurements of acidity (pH) and fluoride ion concentration as practical examples. A smaller project that is part of this dissertation involves the synthesis of a semi- napthofluorescein fluorescent dye with a reactive handle for bioconjugation. This new dye exhibits an unusually large Stokes shift due to its broad absorption spectrum, and also shows highly bathochromically-shifted emission. The properties of this dye compound were studied and fully characterized and included as a chapter of this dissertation.
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Imsick, Brian Gerard, "Fluorescent Materials for Chemical Sensing" (2013). LSU Doctoral Dissertations. 228.