Superquenching and its applications in J-aggregated cyanine polymers

We report the observation of a "superquenching" for water-soluble poly-l-ly sine derivatives containing an appended cationic cyanine dye on each repeat unit. The formally nonconjugated cyanine dye chromophores strongly associa te in a "J" aggregate structure characterized by a sharp red-shifted absorp tion (compared to the monomer) and a similarly sharp red-shifted fluorescen ce. Superquenching is manifested by very large "Stern-Volmer" constants for fluorescence quenching by oppositely charged electron accepters or energy transfer dyes; substantial quenching is observed at levels of quencher corr esponding to one to four molecules per polymer chain. The quenching observe d for these polymers is equivalent or greater to that previously observed f or conjugated polyelectrolytes. We have been able to exploit the superquenc hing of the "J" aggregate polymer fluorescence in a competitive bioassay.