Pressure-area isotherms and fluorescence behaviour of 12-(1-pyrenyl)dodecanoic acid at the air-aqueous solution interface

Abstract

Surface pressure-area (π-A) isotherms of 12-(1-pyrenyl)dodecanoic acid (PDA), alone, and in mixed films with eicosanol, on pure water and basic subphases, were measured concomitantly with the emission spectra of the film at various stages of compression. On a pure water subphase certain portions of the π-A curves could be clearly correlated with the formation of aggregates, primarily composed by PDA molecules. The main driving force for aggregate formation we attribute to hydrogen bonding between the carboxylic moieties of the PDA. Adjustment of the subphase pH such that the carboxylic groups are ionised leads to a large reduction in the degree of PDA aggregation which is seen by a distinct ..