Date of Award
Doctor of Philosophy
Walter S. Struve
Time-resolved fluorescence decay profiles are used to study excitation transport in 2- and 3-dimensional disordered systems. Time-correlated single photon counting detection is used to collect the fluorescence depolarization data. The high signal-to-noise ratios afforded by this technique makes it possible to critically examine current theories of excitation transport;Care has been taken to eliminate or account for the experimental artifacts common to this type of study. Solutions of 3,3[superscript]'-diethyloxadicarbocyanine iodide (DODCI) in glycerol serve as a randomly distributed array of energy donors in 3-dimensions. A very thin sample cell (~2 [mu]m) is used to minimize the effects of fluorescence self-absorption on the decay kinetics. Evidence of a dynamic shift of the fluorescence spectrum of DODCI in glycerol due to solvent reorganization is presented. The effects of excitation trapping on the decay profiles is minimized in the data analysis procedure. The 3-body theory of Gochanour, Andersen, and Fayer (GAF) and the far less complex 2-particle analytic theory of Huber, Hamilton, and Barnett yield indistinguishable fits to the data over the wide dynamic range of concentrations and decay times studied;Octadecylrhodamine B (ODRB) dispersed in the lipid dioleoylphosphatidylcholine (DOL) in a Langmuir-Blodgett (LB) film at an air-water interface provides a 2-dimensional array of donors with which to study excitation transport. Characteristics of the LB film make it possible to study a much wider dynamic range of donor concentrations than is possible in a system of dye molecules adsorbed onto an insulating surface. The data fitting model includes fluorescence depolarization due to the restricted rotational motion of the ODRB in the LB film. The excitation transport dynamics for reduced chromophore concentrations up to ~5.0 were described well by a 2-dimensional 2-particle theory developed by Baumann and Fayer. ftn[superscript]1DOE Report IS-T-1290. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
David Edward Hart
Hart, David Edward, "Picosecond excitation transport in disordered systems " (1987). Retrospective Theses and Dissertations. 8650.