Asymptotic structure of charged colloids between two and three dimensions: the influence of salt

We present theoretical, computer simulation and experimental results for the structural length scales characterizing bulk and confined charged colloidal suspensions. The target quantities are the bulk pair correlation functions on the one hand, and the oscillatory solvation forces of the colloids in films of various thicknesses on the other. Recently we have shown, for a system with very low salt concentration, that these quantities are characterized by the same wavelength in the asymptotic limit, in agreement with predictions from density functional theory. Here we consider systems with larger ionic strengths of added salt. Our results indicate that the wavelength remains essentially unaffected, whereas the correlation length and the amplitude depend significantly on the amount of added salt. Indeed, already at ionic salt strengths as low as 10(-3) mol l(-1) the force oscillations essentially disappear.