Colloidal Interactions—DLVO Theory and Beyond

The long-range approximation of the DLVO theory fails to predict the surface forces at distances below the Debye length or in highly concentrated electrolytes. Previous studies have revealed the contribution of non-DLVO hydration and structural forces to the overall interaction. However, the physical behaviour of charged sufaces separated by near molecular distances in solution is not well understood yet. In order to further explore structural details of the electrostatic double layer, the accuracy of the extended Surface Force Apparatus was used to directly measure the surface forces between two atomically flat mica surfaces in monovalent nitrate solutions. This chapter summarizes the discovered fine structure in highly confined double layers. The precise quantification of structural components allows classification of previously reported oscillatory non-DLVO surface forces into distinct structural or dehydration transitions involving different ion species and a wide range of concentrations.