Description of excitation energy transfer (EET) in large multichromophoric systems of nanoscale size is often inconsistent with the classical Förster model. In this work, kinetics of the EET between J-aggregates of donor thiamonomethinecyanine dye (D) and acceptor thiamonomethinecyanine dye (A) was studied in solutions of the dye mixtures. Inter-aggregate EET of high efficiency close to 100% was found in the DA mixture, due to the tight overlap of the photoluminescence emission band of the donor J-aggregate and absorption band of the acceptor J-aggregate. This process was found to compete with inter-aggregate excimer formation which was clearly observed in both D and A solutions as a result of interaction of the excited J-aggregate and a ground-state guest dimer with some delay due to the exciton migration within the mother J-aggregate towards the excimer-forming site . The above efficient EET was found to have only a marginal contribution from the direct dipole-dipole resonant energy transfer component, whereas the major contribution originated from excitons which delayed due to diffusion to the EET sites and then trappedby the guest acceptor aggregate. The result of the above mechanism of EET was the delayed D-A energy transfer with a negligible change in the emission lifetime of the donor J-aggregate in the presence of the acceptor and increased rise time of the acceptor emission, respectively.
DimitrievO.P., PiryatinskiYu.P., Slominskii Yu.L.Excimer emission in J-aggregates//J Phys Chem Lett. -2018.- 9.-P. 2138–2143.