Abstract
The optical properties and the structure are investigated for phosphatidic acid (PA) Langmuir films adsorbing cyanine dyes from the aqueous solutlon at the air-water interface, and are also studied for PA LB films containing the dyes on substrates. H∗ aggregation of the dyes oriented perpendicular to the water surface is observed at pH5 of the subphase for the PA Langmuir films. The H∗ aggregation, however, is not observed after the LB films are deposited on the substrates, and J aggregate appears instead of it. Aggregation structures of the dyes in the PA Langmuim films and in the LB films are different from the structures of the dyes adsorbed in arachidic acid films, and the structures depend upon pH of the subphase. Furthermore, absorption peaks of the aggregates, calculated using an extended dipolar model, coincide with the experimental absorption spectra. The properties are of great interest for controlling characteristics of LB films adsorbing dyes and fabricating LB devices.
