Ellipsometric microscopy: Imaging monomolecular surfactant layers at the air-water interface

Abstract

It is shown that a slight modification of a conventional ellipsometer produces photomicrograph images with a high vertical sensitivity and a lateral resolution in the micrometer range. Images of various test samples in the monolayer region are presented to illustrate the resolution of this technique. Beside the recently developed Brewster angle microscopy, this method represents a valuable alternative to fluorescence microscopy for the investigation of surfactant monolayers at the air-water interface, because the images are of comparable quality and no fluorescence label is required that might affect the film properties. Furthermore, we present in this context a detailed analysis of whether these measurements allow the simultaneous determination of thickness and refractive index of a Langmuir monolayer on water.