Spectral properties of some fluorescent dyes in two-dimensional films formed by means of Langmuir-Blodgett technique

Langmuir and Langmuir-Blodgett (LB) films formed of some fluorescent dyes, namely three derivatives of naphthalenebicarboxylic acid and one derivative of naphthoylenebenzimidazole as well as of their mixtures with arachid acid and liquid crystal 4-octyl-4'-cyanobiphenyl (8CB) have been studied. Surface pressure and surface potential versus mean molecular area isotherms for Langmuir films were recorded and information about intermolecular interactions at the aireliquid interface were obtained. Absorption spectra in situ for Langmuir films and both absorption and fluorescence spectra for LB films were recorded. Additionally, in order to analyze the spectra in wide range of a dye concentration some absorption and fluorescence measurements of dyes dissolved in 8CB were performed in sandwich cells. The results obtained from spectroscopic studies have led to conclusions about the formation of self-aggregates by dye molecules.