Investigation of β-Cyclodextrin Immobilized at Silica Surfaces by Fluorescence Spectroscopy

Steady-state and frequency-domain fluorescence spectroscopy are used to study the inclusion complexation of six anilinonaphthalene sulfonates (ANSs) with silica-immobilized beta-cyclodextrin (βCD). To fit the experimental data, we compared several modified Lorentzian lifetime distribution models. However, in all cases studied, a simple unimodal Lorentzian distribution best fit the fluorescence decay kinetics. The recovered distribution shapes did not change substantially as the surface was titrated with ANS; however, subtle trends suggest that silica-immobilized βCDs in more hydrophobic environments complex first. Furthermore, the recovered distribution widths (a measure of the environmental heterogeneity) for the silica-immobilized βCD-ANS complexes are always broader than those for ANS-βCD complexes in bulk solution.