Energy transfer of dyes in Langmuir-Blodgett monolayers studied by picosecond time-resolved fluorimetry

Abstract

Energy transfer via dipole-dipole interaction between chromophores in Langmuir-Blodgett monolayer assemblies is investigated by standard continuous wave (c.w.) and picosecond time-resolved fluorescence measurements. The dependence of the fluorescence decay function on the chromophore density in the monolayer is studied, together with the effects of adding non-fluorescing acceptors to the same layer and to a separate layer. Comparison of the resulting non-exponential decays with calculated model functions shows that the different cases can be distinguished by their degree of fit to a decay function valid for Förster-type energy transfer. For c.w. laser irradiation over a long period, different bleaching behaviour for chromophore densities corresponding to weak and strong energy transfer suggests that dye monomers and dye aggregates in the monolayer differ in their photochemical damage probability.