title: Interfacial binding of divalent cations to calixarene-based Langmuir monolayers.
abstract: The interactions of Langmuir monolayers produced through the self-assembly of an amphiphilic p-carboxycalix[4]arene (1) with a series of divalent, fourth-period transition metals, at the air-water interface, were investigated. Changes in the interfacial behavior of 1 in response to the presence of CuCl2, CoCl2, MnCl2, and NiCl2 were studied by means of Langmuir compression isotherms and Brewster angle microscopy (BAM). The measurements revealed that the self-assembly properties of 1 are significantly affected by Cu(2+) ions. The interactions of 1-based monolayers with Co(2+) and Cu(2+) ions were further investigated by means of synchrotron radiation-based X-ray reflectivity (XRR), X-ray near-total-reflection fluorescence (XNTRF), and grazing incidence X-ray diffraction (GIXD). XNTRF and XRR analyses revealed that the monolayer of 1 binds more strongly to Cu(2+) than Co(2+) ions. In the presence of relatively high concentrations of Cu(2+) ions in the subphase (1.4 × 10(-3) M), XNTRF exhibited anomalous depth profile behavior and GIXD measurements showed considerably strong diffuse scattering. Both measurements suggest the formation of Cu(2+) clusters contiguous to the monolayer of 1.
authors.affiliation: Institute of Chemistry and Bioanalytics, School of Life Science, University of Applied Sciences and Arts Northwestern Switzerland , Muttenz, Switzerland.
authors.forename: Ludovico G
authors.initials: LG
authors.lastname: Tulli
authors.forename: Wenjie
authors.initials: W
authors.lastname: Wang
authors.forename: William R
authors.initials: WR
authors.lastname: Lindemann
authors.forename: Ivan
authors.initials: I
authors.lastname: Kuzmenko
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Meier
authors.forename: David
authors.initials: D
authors.lastname: Vaknin
authors.forename: Patrick
authors.initials: P
authors.lastname: Shahgaldian