Lateral conduction at a monolayer-water interface

Abstract

Measurements are reported of the lateral conductance and surface potential of stearic acid and phospholipid monolayers at the air-water interface. Both quantities show a rapid increase and strong dependence on packing density, once the monolayer has been compressed below a critical area per molecule. It is argued that these effects are likely to arise from the formation of a hydrogen-bonded network between the monolayer head group and nearest-neighbour water molecules. The concomitant decrease in local permittivity would contribute to the increase in surface potential while photon transport would be facilitated along the interface, leading to the enhanced conductance observed.