STUDIES OF COLLOIDAL INTERACTIONS USING TOTAL INTERNAL-REFLECTION MICROSCOPY

Total internal reflection microscopy has been used to study the intera ctions between a single colloidal particle and a solid surface in an a queous environment. The effects upon the interaction of various concen trations of 1:1 electrolyte were in good accord with expectation, exce pt at distances less than 100-150 nm, where an additional attractive i nteraction of presently unknown origin appeared. In the presence of an electric held normal to the surface, the interactions were modified i n a manner which accorded well with electro-kinetic theory, allowance being made for the hindered diffusion near a wall. Addition of adsorbi ng polymer (polyethylene oxide) above a threshold concentration inhibi ted irreversible bonding of the particle to the wall. The observed int eraction of an oil-in-water emulsion droplet with the solid surface sh owed no effects of drop deformation. These results are discussed in th e light of recent studies. (C) 1998 Elsevier Science B.V.