Ion pair and larger ion cluster formation in water interfacial regions: An atomic force microscopy study

Abstract

Interfacial regions attached to hydrophobic and hydrophilic surfaces have very low relative permittivities (ε ∼ 3–5), and these low values induce the formation of ion pairs. A detailed description of ion pairing will be possible only after the development of adequate experimental probing methods. The scheme described in this work detects the ion pair (or multistage ion association) formation in water solutions in the interfacial region. Forces acting on the tip when immersed in the interfacial region attached to hydrophilic substrates, such as mica where ε 7) intercalated in between attractive regions (ε < 7).