Modification of aggregate formation in arachidic-acid–cyanine-dye complex Langmuir–Blodgett films by substituent groups

Abstract

Water‐soluble cyanine dye derivatives can be adsorbed from aqueous solution to an arachidic acid monolayer at the air‐water interface. Interface‐adsorbed complex Langmuir–Blodgett films of arachidic acid and four different derivatives of thiacarbocyanine dyes were fabricated using this method, and their optical properties were examined employing a linearly polarized incident. Clear differences in both spectral shape and in‐plane anisotropy were found among the films of different derivatives, each associated with an aggregate form characteristic of the substituent group. They can be classified as a dimer with Davydov splitting, a monomer, and a J aggregate. Estimation of the configuration of the molecules in the dimers and measurement of the photoluminescence spectrum for the J aggregate were performed to clarify the nature of aggregates. The results suggest the possibility of systematic control of aggregate formation in the system by introducing substituent groups for dyes.