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|Title:||Electronic Excitation Energy Transport and Trapping in Dispersions of Dye Molecules in Rigid Media|
|Author(s):||Meunier, David Mark|
|Doctoral Committee Chair(s):||Faulkner, Larry R.|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||This research involves electronic excitation energy (exciton) transport and trapping in dispersions of dye molecules in films of polymer and protein. Excitonic diffusion coefficients and effective concentrations of self-traps were evaluated by comparing luminescence decay curves to theoretical curves predicted by the YT-Pade model.
Exciton motion in dispersions of SR101 in PVOH films was found to be nondiffusive, but it appeared to approach diffusive behavior for high (SR101). A three-dimensional excitonic diffusion length of 250 A was calculated for (SR101) = 23.2 mM. A monotonic increase in the effective concentration of self-traps was observed for (SR101) $>$ 5 mM.
In an effort to reduce the concentration of undesirable self-traps, the protein bovine serum albumin (BSA) was chosen as a possible matrix for spatial isolation of SR101. The binding interaction between SR101 and BSA was qualitatively addressed in a Stern-Volmer quenching analysis, which revealed a significant decrease in the quenching rate constant when BSA was present relative to when BSA was absent. The quantitative details of binding were determined using fluorescence polarization and equilibrium dialysis techniques. BSA was found to contain 10 binding sites for SR101. The association constants for binding at these sites were found to range from 8 $\times$ 10$\sp5$ M for the first site to 8 $\times$ 10$\sp4$ M for the tenth site.
Exciton mobility in dispersions of SR101 in BSA films was found to be poorer than that in the PVOH matrix. Exciton migration was found to be diffusive. The effective concentrations of self-traps were found to be much larger than those observed in the PVOH matrix.
A model for diffusive quenching of excitons at a planar boundary was developed. The final form of this model predicts that the severity of quenching depends on the magnitude of the diffusion length and the film thickness. Luminescence decay curves were collected for films containing SR101 molecules. The quenching boundary was a 50 A overcoating of metal-free phthalocyanine. Diffusion coefficients evaluated by comparison of the experimental curves to curves predicted by the above mentioned model were roughly one order of magnitude larger than those evaluated from homogeneous trapping experiments.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.
|Date Available in IDEALS:||2014-12-15|