FLUORESCENCE SPECTROSCOPY FOR A CELLULOSE TRIOCTADECANOATE MONOLAYER AT THE AIR-WATER-INTERFACE

This paper describes an application of fluorescence spectroscopy for in situ studies of the structure of monolayer films spread at the air/water interface. Cellulose trioctadecanoate, morphologically well characterized by electron microscopy, was employed as the sample polymer. The alkyl side chains were partially replaced with a fluorescent probe, pyrenebutyryl group, and the emission properties of the pyrene units involving excimer formation were investigated as a function of surface pressure. The spectroscopic data were consistent with the film structures observed with an electron microscope. Decay curve measurements with a single photon counting technique revealed that the excited pyrenes in the monolayer are significantly quenched by oxygen in the air. This means that the molecules located just at the interface sensitively respond to the change of the atmosphere. Thus, the fluorescence technique can be a unique and powerful method to study surface films in situ. Some interesting photophysical characteristics of the surface films were disclosed.