Langmuir–Blodgett films of some fluorescent dichroic dyes as studied by optical spectroscopy methods

Langmuir and Langmuir–Blodgett (LB) films of some dichroic dyes, namely derivatives of naphthalenebicarboxylic acid and of naphthoylenebenzimidazole, have been studied. On the basis of the surface pressure–mean molecular area isotherms of Langmuir films, the alignment of the molecules on the air–water interface has been estimated. The Langmuir films were transferred onto the quartz plates at surface pressures below the collapse point. The absorption and fluorescence spectra of LB films by using unpolarized and linearly polarized light have been recorded. The results obtained have allowed conclusions to be drawn about the arrangement of the dyes molecules on the air-solid substrate interface. Moreover, the spectral investigations of the dyes in LB films have revealed the formation of self-aggregates in monomolecular layers.