Adsorption of nanolatex particles to mineral surfaces of variable surface charge

The adsorption of 25-nm-diameter latex particles to flat sapphire (alpha-Al2O3) and cerium oxide (CeO2) substrates was studied as a function of pH by direct imaging and force measurement. The adsorption density was highest for latex dispersions at low pH and decreased as the pH increased. For the CeO2 substrate, no adsorption of latex was evidenced above the point of zero charge (PZC) of the substrate, In the framework of classical electrostatic interactions, a model was used to describe the adsorption density by taking into account the balance between the surface attraction and the repulsion caused by existing adsorbed particles. On the other hand, classical electrostatic arguments could not account entirely for the adsorption of the latex to the sapphire substrate, because significant adsorption occurred above its PZC. For both substrates, the possibility of lateral migration of the adsorbed particles was examined. Finally, direct force measurements between adsorbed layers of nanolatex particles were performed to quantify the encapsulation layer strength.