Solid state concentration quenching of organic fluorophores in PMMA

In this study the concentration quenching phenomenon is explored for seven organic singlet emitters (Rhodamine 6G, Pyridine 2, Lumogen F Red 305, Perylene, Coumarin 102, DCM and DCJTB) in an inert host of poly(methyl methacrylate) (PMMA). Combining fluorescence lifetime and quantum yield measurements on samples of different molecular separation allows a deep decay rate analysis to be performed yielding, for each fluorophore, a monomial power law that indicates the strength and type of interaction. The fluorophores studied exhibit interactions in between that of FRET-like dipole-dipole (R(-6)) and surface-surface (R(-2)) with many lying close to that expected for surface-dipole (R(-3)) interactions. With no observed dependence on molecular structure it is concluded that the concentration quenching rate in singlet emitters follows a power law as kCQ = aR(-3.1±0.7) with aggregation expected to increase the magnitude of the observed power.