UC Riverside

Fluorescence is a radiative-deactivation phenomenon of broad importance for opticalimaging and sensing. Fluorescence also can serve as a signal for characterizing excited-state dynamics and the kinetics of other parallel processes such as energy transfer and charge transfer (CT). The importance of CT cannot be overstated. In addition to sustaining life on earth in photosynthesis, cellular respiration and redox enzymatic conversions, CT ensures the modern ways of living possible as a part of electronics photonics and energy conversion. My work focuses on developing methods for characterizing fluorescent chromophores and redox species that can undergo CT. The viscosity of the microenvironment can have a huge impact on the fluorescence properties of photoprobes of biological importance. After a brief introduction, the second chapter of my dissertation describes the development of methodology for utilizing a thermoset transparent polymer as a room-temperature solid solvent for spectroscopy applications. With ultimately large viscosity, this solid-state media shows significant effects on suppressing non-radiative pathways of deactivation and enhancing the fluorescence quantum yields of certain dyes by orders of magnitude. The third chapter describes a method for expanding the applicability of cyclic voltammetry (CV), which is the most widely used technique in electrochemical analysis. My work demonstrates how to obtain useful information, in terms of standard electrochemical potentials, from voltammograms showing irreversible behavior. Such information is essential for characterizing electron donors and acceptors for CT systems. The fourth chapter demonstrates the utility of spectroscopic and electrochemical studies for CT. Fundamental scientific studies show the importance of hydrogen bonding for transferring holes and electrons in peptide conjugates. Deciphering structure-function relationships also demonstrates how hydrogen-bonding propensity of fluorescent probes, which can act as electron donors and acceptors, can induce well-defined folds in oligopeptides that are as short as four residues. These fundamental-science studies set an important foundation for electronics, photonics and bioinspired engineering.