Energy transfer in monolayers with cyanine dye Sheibe aggregates

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Abstract
A monolayer of an oxacyanine dye organized in Scheibe aggregates is doped with a thiacyanine dye (e.g., one molecule of the guest per 104 molecules of the host). Strong energy transfer from the excited host to the guest takes place at room temperature, the efficiency decreasing with lowering temperature T. The rate of energy transfer is proportional to T. A simple model of the excited state is discussed based on a coherent exciton extending over a certain domain. The exciton moves over the aggregate, occasionally reaching the vicinity of an acceptor molecule. The domain size of the exciton is inversely proportional to the absolute temperature T. As a consequence, the lifetime of the exciton is proportional to T, and therefore the energy transfer efficiency is proportional to T