Adhesion forces between functionalized probes and hydrophilic silica surfaces

Adhesion forces between functionalized colloidal polymer spheres and a hydrophilic silica surface under different solution conditions were measured using an atomic force microscope (AFM). The measured force profiles show that the adhesion forces are sensitive to surface functional groups, pH, salt concentrations and the valency of cationic species. At pH below 8, the adhesion force between the surfaces of carboxylate functionality and hydrophilic silica wafer is about one order of magnitude greater than that between the surfaces of amine functionality and hydrophilic silica wafer. The strong adhesion interactions observed between the carboxylic-acid-functionalized probe and the hydrophilic silica surfaces are mainly attributed to hydrogen bonding between the surfaces. Our results suggest that hydrogen-bonding interactions can be mediated by the addition of divalent species as demonstrated by the addition of calcium ions at 0.1 and 1.0 mM concentration.