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 s odium dodecyl sulfate (SDS)/bovine serum albumin (BSA) and SDS/poly(ethylen e oxide) (PEO) solutions was studied by steady-state and time-resolved fluo rescence methods to determine the effect of viscosity. The viscosity-depend ent ratio between intramolecular excimer and monomer fluorescence intensiti es of 1,10-bis(1-pyrene)decane was obtained by steady-state fluorescence me asurements. The results show that in micelle-like clusters formed in SDS/BS A 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 empir ical parameter depending on viscosity.