On the intramolecular excimer formation of 1,10-bis(1-pyrene)decane in organized media

The formation of an intramolecular excimer of 1,10-bis(1-pyrene)decane in sodium dodecyl sulfate (SDS)/bovine serum albumin (BSA) and SDS/poly(ethylene oxide) (PEO) solutions was studied by steady-state and time-resolved fluorescence methods to determine the effect of viscosity. The viscosity-dependent ratio between intramolecular excimer and monomer fluorescence intensities of 1,10-bis(1-pyrene)decane was obtained by steady-state fluorescence measurements. The results show that in micelle-like clusters formed in SDS/BSA and SDS/PEO systems, the microviscosity is higher than in free micelles. It was found that Birks' kinetic model was not valid in this case, and the monomer and excimer fluorescence decays had to be fitted by a sum of three exponentials. The excimer formation kinetics in constrained systems is more complex than in homogeneous solutions, but it is possible to find an empirical parameter depending on viscosity.