Atomic force and scanning near-field optical microscopy study of carbocyanine dye J-aggregates

Atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM) imaging of fibrillar J-aggregates of carbocyanine dye 3,3′-bis(γ-sulfopropyl)-5,5′,6,6′-tetrachloro-1,1′-dioctylbenzimidacarbocyanine (C8S3) is performed on mica and glass substrates at room temperature. High resolution AFM imaging reveal that thick fibrils consist of narrow sub-fibrils. A model of an elementary fibril with a cross section 3 × 4 nm 2 in size is proposed. The SNOM measurements made in the contact mode indicate the high mechanical strength of the fibrillar J-aggregates.