Surfactant-induced changes of morphology of J-aggregates:: Superhelix-to-tubule transformation

The morphology of the J-aggregates formed after the addition of ionic surfactants into solutions of the 3,3'-bis(3-carboxypropyl)-5,5',6,6'-tetrachloro-1,1-diocylbenzimidacarbocyanine dye (C803) was characterized by absorption and circular dichroism spectroscopy, cryogenic temperature transmission electron microscopy, scanning force microscopy, and small-angle neutron scattering. The optical activity of the C803 J-aggregates, existing in aqueous solution as superhelices composed of tubular single strands, disappears upon addition of both cationic and anionic surfactants. This is accompanied by distinct spectral changes in the visible region as well as changes of the aggregates' morphology. The anionic surfactant sodium dodecyl sulfate induces the formation of single-walled tubules of 15 nm diameter and 300-600 nm length, which completely transform after several days into thick multilamellar tubes of micrometer length. The cationic surfactant trimethyltetradecylammonium bromide first produces vesicles that later transform again into tubular aggregates of nanometer thickness and micrometer length.