Molecular layer-by-layer self-assembly of water-soluble perylene diimides through pi-pi and electrostatic interactions

A layer-by-layer deposition process has been carried out for two oppositely charged water-soluble perylene diimide dyes without the use of intervening polyelectrolyte layers. The strong pi-pi interactions between the perylene moieties help stabilize the layers and simultaneously diminish the fluorescence quantum yield of the array without strongly affecting the absorption or fluorescence spectra. There is an alternation of fluorescence intensity according to which perylene species is on the outer layer, which is interpreted as the effect of facile energy transfer between the perylenes.