Advances in Luminescence Sensors, Techniques, and Instruments
Payne, Sarah Jeanne McPeak, Department of Chemistry, University of Virginia
Demas, James N., Department of Chemistry, University of Virginia
Luminescence technology is rapidly advancing and finds wide use in various sensor applications. There is an increasing need for accurate, sensitive, and rapid ways to observe properties, which are addressed in this work. Historical context is also important: toward this end there is an extensive historical discussion about the development of phase-shift lifetime instrumentation. Commonly phase-shift measurements are used to measure luminescent lifetimes. Variations on previous methods were developed to make multiple-frequency measurements in one adaptable, self-contained experiment. Complex lifetimes were observed by combining select frequencies into one signal. Devices utilizing these excitation waveforms were developed. One an analog instrument, and the second device, derived from the former, has a digital detection system allowing transients with shorter lifetimes. These new devices allowed deeper investigation into complicated luminescent decays, as well as investigation into the effects of various excitation waveforms. Phosphorescent molecules and their spectra are often used in sensing applications. Instrumentation was developed to separate phosphorescence and fluorescence. This instrument takes a unique approach using optical rather than mechanical methods. Instrument versatility is demonstrated using various luminaphores. Lifetimes are often used as analysis tools for luminescent systems. Since decays in analytical systems are frequently complex rather than single exponentials, apparent lifetime methods based on the rapid lifetime determination method or single frequency phase-shift measurements are frequently used to reduce cost and simplify analysis. It is demonstrated here that these methods can produce large errors under certain conditions. Both can give atypical Stern-Volmer quenching plots (SVQPs) in twocomponent systems. These behaviors include bimodal quenching and ‘anti-quenching’ curves. These peculiar phenomena are exacerbated by small fractions of long unquenched components. Heterogeneity in luminescent sensors embedded in polymers has been an issue for quite some time causing downward curved SVQPs. Here we try to make these systems simpler by making the systems homogeneous. A system in which a ruthenium complex is synthetically attached to the polymer is studied in an attempt to eliminate the heterogeneity of the polymer system. Systems and theory were developed to improve luminescence instrumentation. These methods have also given insight into new phosphorescent systems and nonexponential decays.
PHD (Doctor of Philosophy)
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