title: Self-assembled monolayer of a redox-active calix[4]arene: voltammetric recognition of the Ba2+ ion in aqueous media.
abstract: The Redox-active monolayer of a novel calix[4]arene recognizing redox-inactive ionic species by voltammetry is reported. Calix[4]arene-disulfide-diquinone, which is not only redox-active but is also a highly selective ionophore for the Ba2+ ion, spontaneously forms a stable and dense monolayer film on gold. The redox-active calixarene monolayer selectively recognizes Ba2+ ion in aqueous media, and the voltammetric signals are proportional to the ionic concentration. A new voltammetric peak can be detected by square-wave voltammetry upon adding a dilute solution containing Ba2+ ion having a concentration as low as 1.0 x 10(-6) M. The Langmuir plot (1/ip vs 1/[Ba2+]) shows a linear slope in the range from 1.0 x 10(-6) M to 1.0 x 10(-4) M. This modified electrode does not show any significant interference from alkali and alkaline earth metal ions except for Sr2+ and Ca2+. Only 100- and 500-fold concentrations of Sr2+ and Ca2+ ions, respectively, can lead to voltammetric responses comparable to that of Ba2+.
authors.affiliation: School of Chemistry and Molecular Engineering, Center for Molecular Catalysis, Seoul National University, Korea.
authors.forename: T D
authors.initials: TD
authors.lastname: Chung
authors.forename: J
authors.initials: J
authors.lastname: Park
authors.forename: J
authors.initials: J
authors.lastname: Kim
authors.forename: H
authors.initials: H
authors.lastname: Lim
authors.forename: M J
authors.initials: MJ
authors.lastname: Choi
authors.forename: J R
authors.initials: JR
authors.lastname: Kim
authors.forename: S K
authors.initials: SK
authors.lastname: Chang
authors.forename: H
authors.initials: H
authors.lastname: Kim