Aggregate Formation of Pyrene-1-Carboxylic Acid in an Ion-complexed Langmuir-Blodgett Film Induced by Contact with HCl Gas

Ion-complexation between a cationic amphiphile and pyrene-1-carboxylate (PyCOO−) dispersed the PyCOO− anions homogeneously in a Langmuir-Blodgett monolayer film. By bringing the film into contact with HCl gas, formation of fluorescent spots in the monolayer was observed by fluorescence microscopy. With an atomic force microscope, the spots were found to be topographically much higher than the monolayer level, and concluded to be aggregates formed by lateral diffusion of neutralized pyrene-1-carboxylic acid (PyCOOH) molecules in the monolayer.