J. Phys. Chem. 1996, 100, 13701-13715
13701
Global Analysis of the Fluorescence Decays of N,N′-Dioctadecyl Rhodamine B in Langmuir-Blodgett Films of Diacylphosphatidic Acids P. Ballet, M. Van der Auweraer,* and F. C. De Schryver Laboratory for Molecular Dynamics and Spectroscopy, Chemistry Department, K. U. LeuVen, Celestijnenlaan 200F, 3001 HeVerlee, Belgium
H. Lemmetyinen and E. Vuorimaa Institute of Materials Chemistry, Tampere UniVersity of Technology, P.O. Box 589, 33101 Tampere, Finland ReceiVed: January 29, 1996; In Final Form: May 9, 1996X
Langmuir-Blodgett multilayer films were prepared from N,N′-dioctadecyl rhodamine B (RB18) diluted in dioleoylphosphatidic acid (DOPA) or dipalmitoylphosphatidic acid (DPPA) with various mixing ratios. Surface pressure-area isotherms of monolayers of the two matrices were recorded. Absorption and fluorescence spectra and fluorescence decays of the multilayer samples of RB18 were further examined. The fluorescence decay curves of RB18 in the multilayer assemblies, determined using time-correlated single photon counting, were analyzed in the framework of several models leading to nonexponential decays: (1) multiexponential decay; (2) Gaussian distribution of rate constants; (3) stretched-exponential decay, characteristic of Fo¨rster energy transfer in self-similar fractal-like structures with a fractal dimensionality of
