Contact electrification induced by monolayer modification of a surface and relation to acid–base interactions

Abstract

ELECTRICAL charge separation following contact between two materials (contact electrification or the triboelectric effect) is well known to occur between different materials as a consequence of their different electronic structures^1,2. Here we show that the phenomenon occurs between two surfaces of the same material if one is coated with a single chemisorbed monolayer. We use the surface force apparatus³ to study contact electrification⁴ and adhesion between two silica surfaces, one coated with an amino-silane. The presence of this monolayer results in significantly enhanced adhesion between the surfaces, owing to electrostatic attraction following contact electrification, in accord with Derjaguin's electrostatic theory of adhesion⁵. At the same time, the observed increase in adhesion is consistent with Fowkes' acid–base model⁶ (in which acid–base interactions between surface groups are considered to be the predominant factor determining adhesion), as the monolayer converts the originally acidic silica surface to a basic (amine-terminated) one. These observations demonstrate a link between acid–base interactions and contact electrification.