Probing interaction forces in colloidal monolayers:: Inversion of structural data

The knowledge of the potential between interacting colloidal particles is essential to describe and control the aggregation processes in which they are involved. However, interaction forces also bring out spatial ordering phenomena, which has been used to obtain helpful information on them in three-dimensional dispersions. In this paper we look into this possibility for colloidal monolayers spread at the water-air interface. The radial distribution function has been determined for an assembly of negatively charged polystyrene particles at low concentration and without an additional electrolyte. A simple inversion scheme based on the HNC closure has been proved to give reliable information on u(r), providing that particles are not strongly correlated. Apart from the expected repulsive forces, the application of the inversion procedure suggests the possibility of a long-ranged attractive interaction. (C) 2001 American Institute of Physics.