Applications of multifrequency phase and modulation fluorescence spectroscopy to the investigations of the microheterogeneity of organized media.

摘要

The subject of this thesis research is focused on the exploration of the mechanism of cyclodextrin inclusion complexation, and properties of the micellar assemblies (sodium dodecyl sulfate (SDS) micelles) by examining the local environment of the fluorescent probes.; The inclusion complexation of 2-anilinonaphthalene-6-sulfonic acid (2,6-ANS) and {dollar}beta{dollar}-cyclodextrin ({dollar}beta{dollar}-CD) was studied. Fluorescence lifetimes were determined in the presence of various concentrations of dynamic quenchers (Cu{dollar}sp{lcub}2+{rcub}{dollar}, acrylamide, and I{dollar}sp-{dollar}). Frequency-domain data were analyzed by a global analysis protocol linked by the Stern-Volmer equation. A unimodal Lorentzian distribution model was determined to be the best fit to the experimental data. This conclusion was also confirmed by measuring the lifetime of the inclusion complex (2,6-ANS-{dollar}beta{dollar}-CD) at different temperatures. The continuous fluorescence lifetime distribution is a indicative of the microheterogeneity of the microenvironments of 2,6-ANS sequestered inside the {dollar}beta{dollar}-CD cavity. The quenching constants are discussed for these three diverse quenchers in solutions of 2,6-ANS in water, ethanol, and {dollar}beta{dollar}-CD measured at temperatures ranging from 20 to 50{dollar}spcirc{dollar}C. The effects of different solutes on the inclusion complex formation constant are also reported.; The investigation is then extended to examine the effects of a variety of aliphatic alcohol co-solvents on the nature of inclusion complex formed between 2,6-ANS and {dollar}beta{dollar}-/{dollar}gamma{dollar}-CD. Evidence from emission peak intensity, center and width of the Lorentzian distribution, the molar fraction of lifetime components, as well as the average microviscosity estimated from the steady-state anisotropy indicates that alcohol modifiers have two distinct effects on the cyclodextrin inclusion complex. The extent of these two opposing effects appears to be regulated by the cavity size as well as the composition of the alcohols.; The microheterogeneity of SDS micelles was evaluated by two distinct fluorescent probes, 2,6-ANS and N-phenyl-naphthylamine (1-AN). The decay kinetics of 2,6-ANS, which probes the outer core region of SDS micelles, is characterized by a unimodal Lorentzian distribution. Fluorescence lifetimes of these probes are investigated also as functions of temperature, concentrations of counterions (Na{dollar}sp+{dollar} and Mg{dollar}sp{lcub}2+{rcub}{dollar}) and linear alcohols (n-BuOH, n-PeOH, n-HeOH, and n-HepOH). The collective results from these experiments confirm that the outer core region of SDS micelles is microheterogeneous and the inner core is essentially homogeneous. (Abstract shortened with permission of author.)