Studies of phase transitions in Langmuir monolayers by fluorescence microscopy

Abstract

The liquid–gas transition in monolayers of stearic acid on water has been investigated by fluorescence microscopy. The monolayer texture is made visible by the addition of stearic acid molecules labelled at the 12-position with methyl amino NBD [N-methyl-(7-nitro-2,1,3-benzoxadiazol-4-yl)]. The film texture and its evolution with time after changes have been made in the film density can be observed at areas up to 100 Ų per molecule. In the two-phase region we observe a structure similar to a two-dimensional soap foam. Preliminary analyses have been made of the cell-side distribution and the average linear cell dimension as a function of time.