Atomic Force and Scanning Near-Field Optical Microscopy Study of Carbocyanine Dye J-aggregates
V.V. Prokhorov, M.G. Petrova, N.N. Kovaleva and E.I. Demikhov
Affiliation: Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31 Leninsky pr., Moscow, 119991 Russia.
Keywords: Carbocyanine dye, elementary fibril, high-resolution atomic force microscopy, J-aggregate, probe microscopy,
scanning near-field optical microscopy.
Atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM) imaging of fibrillar
J-aggregates of carbocyanine dye 3,3’-bis(2-sulfopropyl)-5,5’,6,6’-tetrachloro-1,1’- dioctylbenzimidacarbocyanine
(C8S3) have been conducted on mica and glass substrates at a room temperature. High resolution AFM imaging reveals that
thick fibrils consist of narrow subfibrils with the cross diameter in the nanometer range. A model of the "elementary fibril"
with the cross-dimension of 3x4 nm2 was proposed as the aggregate of two J-ladders oriented face-to-face by their
hydrophobic sides while the dye molecules are oriented normaly to the long fibril axis. The SNOM measurements have
been conducted in the contact mode indicating the large mechanical strength on the fibrillar J-aggregate morphology.
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