Resonance energy transfer in dye molecules adsorbed two dimensionally upon aqueous suspensions of polystyrene spheres

The time-resolved photoluminescence in Rhodamine B dye embedded in aqueous suspensions of polystyrene spheres shows an anomalous fast nonexponential decay in addition to the dow decay that is intrinsic to dye molecules. When the volume fraction of spheres is increased to a critical value, the relative intensity of the fast component increases while the decay rate remains constant at 15 ps. A further increase of the Volume fraction lengthens the lifetime of this component to the order of 1 ns. The quantitative behavior of the time dependence of the luminescence is explained well when we consider that dye molecules are adsorbed two dimensionally upon spheres and that the fast decay originates in the resonance energy transfer between the dye molecules. (C) 1999 Optical Society of America [S0740-3224(99)03411-6].