Electrochemical mechanism of ion-ionophore recognition at plasticized polymer membrane/water interfaces

Ryoichi Ishimatsu, Anahita Izadyar, Benjamin Kabagambe, Yushin Kim, Jiyeon Kim, Shigeru Amemiya

    Research output: Contribution to journalArticlepeer-review

    62 Citations (Scopus)


    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 Pb 2+ transfers facilitated by highly selective ionophores are measured and analyzed numerically using the E mechanism to obtain standard IT rate constants in the range of 10-2 to 10-3 cm/s at both plasticized poly(vinyl chloride) membrane/water and 1,2-dichloroethane/water interfaces. We demonstrate that these strongly facilitated IT processes are too fast to be ascribed to the EC mechanism. Moreover, the little effect of the viscosity of nonaqueous media on the IT kinetics excludes the EC mechanism, where the kinetics of simple IT is viscosity-dependent. Finally, we employ molecular level models for the E mechanism to propose three-dimensional ion-ionophore complexation at the two-dimensional interface as the unique kinetic requirement for the thermodynamically facilitated IT.

    Original languageEnglish
    Pages (from-to)16300-16308
    Number of pages9
    JournalJournal of the American Chemical Society
    Issue number40
    Publication statusPublished - Oct 12 2011

    All Science Journal Classification (ASJC) codes

    • Catalysis
    • General Chemistry
    • Biochemistry
    • Colloid and Surface Chemistry


    Dive into the research topics of 'Electrochemical mechanism of ion-ionophore recognition at plasticized polymer membrane/water interfaces'. Together they form a unique fingerprint.

    Cite this