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

The time-resolved photoluminescence in Rhodamine B dye embedded in aqueous suspensions of polystyrene spheres shows an anomalous fast nonexponential d ecay 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 relati ve intensity of the fast component increases while the decay rate remains c onstant at 15 ps. A further increase of the Volume fraction lengthens the l ifetime of this component to the order of 1 ns. The quantitative behavior o f the time dependence of the luminescence is explained well when we conside r that dye molecules are adsorbed two dimensionally upon spheres and that t he fast decay originates in the resonance energy transfer between the dye m olecules. (C) 1999 Optical Society of America [S0740-3224(99)03411-6].