Adsorption behaviour of alizarine violet molecules onto the Langmuir–Blodgett films of octadecylamine

Abstract

The monolayer properties of a long-chain amine were investigated at the air–water interface on addition of an anionic anthraquinone dye in the aqueous subphase. From the pressure–area isotherms at various pHs, hydroxide ions of NaOHaq and the sulfonate ions of Alizarine Violet (AV) in the subphase were found to interact competitively with the octadecylamine monolayer. The adsorbability of the cationic Langmuir–Blodgett (LB) films was investigated using AV as an adsorbate. Steady-state absorption and emission spectroscopy indicated the difference in order, arrangement and orientation of the AV molecule in the restricted geometry of the LB films depending upon the adsorption conditions. Structural characteristics of the LB films were realized by low-angle X-ray diffraction and FTIR spectroscopy. AFM images provided information on the topography of the film surface and rearrangement of the layer structure during the adsorption process.