Spectroscopic properties of an amphiphilic styryl pyridinium dye in Langmuir-Blodgett films

Surface pressure-molecular area and surface potential-molecular area isotherms of the recently synthesized amphiphilic dye 1 indicate that it forms monolayers on distilled water. A shift of the fluorescence maximum from 505 up to 570 nm was measured upon increasing the surface pressure applied during the Langmuir-Blodgett transfer from 7 up to 20 mN/m, and a slight red shift in the absorption. The increase of the surface pressure also produces a new blue-shifted band only present in the p-polarized component of the absorption spectra under oblique incidence of light. The results were interpreted as reorientation and association of the chromophores in the monolayer, according to the extended dipole model.