Space and Time Resolved Spectroscopy of Two-Dimensional Molecular Assemblies

Abstract

The fluorescence decays of several amphiphilic dyes incorporated in Langmuir-Blodgett films were determined and analyzed globally over different dye concentrations and/or emission wavelengths The highly non-exponential character of the fluorescence decay could be analyzed in a model based on two-dimensional energy transfer from the excited monomers to dimers of the dye Depending upon the miscibility of the dye and the matrix, homogeneous and two-phase multilayers were distinguished This distinction could be confirmed by the spatial distribution of the fluorescence as revealed by confocal fluorescence microscopy and near-field scanning optical microscopy For chromophores with important internal rotation (amphiphilic crystal violet) the fluorescence decay at low concentrations is determined by a distribution of free volumes rather than by energy transfer to dimers The homogeneous distribution assumed for an amphiphilic crystal violet in cadmium arachidate could be confirmed by the global analysis of the fluorescence decay of an amphiphilic pyronine in the presence of the amphiphilic crystal violet.