Electrochemical Mechanism of Ion–Ionophore Recognition at Plasticized Polymer Membrane/Water Interfaces

Here, we report on the first electrochemical study that reveals the kinetics and molecular level mechanism of heterogeneous ion–ionophore recognition at plasticized polymer membrane/water interfaces. The new kinetic data provide greater understanding of this important ion-transfer (IT) process, which determines various dynamic characteristics of the current technologies that enable highly selective ion sensing and separation. The theoretical assessment of the reliable voltammetric data confirms that the dynamics of the ionophore-facilitated IT follows the one-step electrochemical (E) mechanism controlled by ion–ionophore complexation at the very interface in contrast to the thermodynamically equivalent two-step electrochemical–chemical (EC) mechanism based on the simple transfer of an aqueous ion followed by its complexation in the bulk membrane. Specifically, cyclic voltammograms of Ag+, K+, Ca2+, Ba2+, and Pb2+ transfers facilitated by highly selective ionophores are measured and analyzed numerically us...