  This communication reports the formation and characterization of self
assembled films of a low molecular weight anionic dye amaranth and polycation
Poly (allylamine hydrochloride) (PAH) by electrostatic alternating
Layer-by-Layer (LBL) adsorption. It was observed that there was almost no
material loss occurred during adsorption process. The UV-Vis absorption and
fluorescence spectra of amaranth solution reveal that with the increase in
amaranth concentration in solution, the aggregated species starts to dominate
over the monomeric species. New aggregated band at 600 nm was observed in
amaranth-PAH mixture solution absorption spectrum. A new broad low intense band
at the longer wavelength region, in the amaranth-PAH mixture solution
fluorescence spectrum was observed due to the closer association of amaranth
molecule while tagged into the polymer backbone of PAH and consequent formation
of aggregates. The broad band system in the 650-750 nm region in the
fluorescence spectra of different layered LBL films changes in intensity
distribution among various bands within itself, with changing layer number and
at 10 bilayer LBL films the longer wavelength band at 710 nm becomes prominent.
Existence of dimeric or higher order n-meric species in the LBL films was
confirmed by excitation spectroscopic studies. Almost 45 minute was required to
complete the interaction between amaranth and PAH molecules in the 1-bilayer
LBL film.
