Excitation energy transfer between J-aggregates in layer-by-layer alternate assemblies

The layer-by-layer alternate assemblies incorporating two kinds of cyanine dyes have been fabricated by the alternate adsorption technique. In order t o examine excitation energy transfer between J-aggregates, a thiacyanine dy e has been employed as the donor and thiacarbocyanine dyes as the acceptor. It is confirmed that these dye combinations form the mixed J-aggregate in the alternate assemblies. From steady-state fluorescence spectra of the mol ecular assemblies, the occurrence of efficient energy transfer from the don or J-aggregate to the acceptor J-aggregate has been demonstrated. The exper imentally obtained rate constant of energy transfer k(ET) in the Stern-Volm er kinetics of the order of 10(13) nm(2) molecules(-1) s(-1) is interpreted in terms of exciton migration and trapping in the mixed J-aggregate. The d ifference in k(ET) between various combinations of cyanine dyes is not inco nsistent with an exponential energy gap law. (C) 2001 Elsevier Science B.V. All rights reserved.