ELECTRON-MICROSCOPIC OBSERVATION OF THE SURFACE-FILM STRUCTURE ON AN AIR-WATER-INTERFACE

The structure of a surface film on an air-water interface, the so called Langmuir film, was observed with high contrast by dark-field electron microscopy imaging. The stearic acid film was not homogeneous but heterogeneous and included many small holes, contrary to the currently accepted concept of a Langmuir film. These holes cannot be attributed to defects at the molecular level because they were several nanometers in diameter. Electron cryo-microscopic studies strongly suggest that the intact structure of the films on the water surface has many holes, and that the shape of the holes reflects the crystal habit of stearic acid. It was demonstrated that the transfer of the Langmuir film to a specimen grid was complete. The pi-A curve, which is generally used to investigate the structure of LB films, inevitably includes a deviation due to the heterogeneity of the surface structure on the air-water interface.