Influence of temperature-induced aggregation on energy transfer from a surfactant to micellized perylene

Forster energy transfer from excited surfactant species was used to monitor their association with micellized perylene at different temperatures. Fluorescence from the perylene acceptor was obtained through sensitization by surfactant monomers and aggregates, the latter being identified as, spectroscopic rather than physical. Surfactant monomer fluorescence was subject to a strong inner filter effect inside the micelles, indicating an abundance of spectroscopically monomeric species there. Temperature increases caused reductions in native surfactant fluorescence through thermal quenching, but sensitized fluorescence intensities generally increased with temperature. This was ascribed to a temperature-induced approach between the perylene acceptor and both monomeric and aggregated surfactant donors. Clouding of the solutions showed little evidence of organizational changes at the micellar level.