Analytical Sciences

Ion-channel Sensors Based on ETH 1001 Ionophore Embedded in Charged-alkanethiol Self-assembled Monolayers on Gold Electrode Surfaces

Hiroshi AOKI,* Yoshio UMEZAWA,* Alberto VERTOVA,** and Sandra RONDININI**

*Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
**Department of Physical Chemistry and Electrochemistry, University of Milan, via Golgi 19, 20133 Milan, Italy

An ion-channel sensor was demonstrated by immobilizing ETH 1001, an ionophore for ion-selective electrodes, on a gold electrode surface. The approach for preparing the sensor was to incorporate the ionophore into a mixed self-assembled monolayer of 10-mercaptodecanesulfonate and 11-hydroxy-1-undecanethiol formed on the surface. The voltammetric responses for the thus prepared sensor to the primary cation Ca²⁺ were observed by using [Fe(CN)₆]^3-/4- as an electroactive marker. The ionophore was stably immobilized on the electrode surface with the hydrophobic interaction between its alkyl chains and those of the alkanethiol. The introduction of a proper charge density to the electrode surface improved the sensor sensitivity with retaining the selective response to Ca²⁺ against Mg²⁺ with concentrations above 10^-4 M.

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