Attractions between charged colloids at water interfaces
  The effective potential between charged colloids trapped at water interfaces is analyzed. It consists of a repulsive electrostatic and an attractive capillary part which asymptotically both show dipole--like behavior. For sufficiently large colloid charges, the capillary attraction dominates at large separations.   The total effective potential exhibits a minimum at intermediate separations if the Debye screening length of water and the colloid radius are of comparable size. 
M. Oettel, A. Dominguez, and S. Dietrich