Comparison of atomic force microscopy and zeta potential derived surface charge density

Surface charge density can be derived from atomic force microscopy (AFM) by using Derjaguin, Landau, Vervey and Overbeek (DLVO) theory. The sub-micrometer data allows observation of local differences in charge density and changes with time or solution composition, which has interesting applications in crystal growth and inhibition, bone formation and colloid behavior. To calibrate this type of AFM data and verify DLVO assumptions, it has to be correlated with an established technique. We successfully matched AFM derived surface charge densities with zeta potential measurements on a mica surface within one order of magnitude. A reproducible difference between surface charge of the mica substrate exposed to solutions cations with monovalent and divalent charge was also observed. The results provide confidence that the AFM method is valid for obtaining local surface charge information.