Static properties of confined colloidal suspensions

The static structure of aqueous suspensions of polystyrene spheres, confined between two parallel glass plates, is measured by means of digital video microscopy. The concentration of colloidal particles is varied in a wide range within the liquid phase. The effective interparticle pair potential between the colloidal particles in this geometry is obtained from the measured static properties of the system via the two-dimensional version of the Omstein-Zernike equation. The effective pair potential obtained in this way is found to be of short range with a well defined attractive component, features that are qualitatively reproduced in the whole range of concentrations studied.