Layer-by-layer self-assembly of polyelectrolyte and the divalent salt of fluorescein

Smooth organic thin films have been obtained by repeated surface complexation between a polycation and fluorescein di-sodium, a divalent organic anion, in a layer-by-layer (LbL) fashion. UV-Vis and thickness measurements show a linear growth of the multilayer as a function of deposition cycles, and indicate that the dye is in a J-aggregate state in the multilayer. The dynamical properties of the multilayer, which are assessed by time-dependent UV spectroscopy, indicate the existence of two relaxation processes. The faster one is due to slow drying and thermal equilibration of the film. The slower process results from spatial rearrangement of dyes in the multilayer, leading to a lower aggregation rate.