BEHAVIOR OF METHYLENE BLUE WITH ARACHIDIC ACID IN THE RESTRICTED GEOMETRY OF LANGMUIR–BLODGETT FILM

Anti-malarial methylene blue (MB) doped in arachidic acid (AA) have been incorporated in the Langmuir monolayer at the air–water interface and also in the Langmuir–Blodgett films deposited on quartz substrate. The pressure–area (π–A) isotherm studies at different concentrations of MB pointed out that pure MB could not form stable monolayer at the air–water interface and collapse readily at very low surface pressures. However, mixture of MB with AA formed stable monolayers and they could be transferred into solid quartz substrate to form mono/multi layered films of MB. The area per molecule of floating mixed monolayers was systematically decreased with the increasing concentrations of MB in the mixture. The pressure–time (π - t) isotherm study indicated the interaction kinetics between MB and AA. Higher the concentration of MB, higher is the increase in pressure. The spectroscopic characteristics of the mixed LB films have been compared with that of pure MB solution, microcrystal and layer-by-layer self assembled film with UV-Vis absorption spectroscopy. Surface morphology of the mixed LB and LbL film of MB was measured with atomic force microscopy (AFM).