Self-assembled monolayers (SAMs) of crown ether adsorbates on gold reversibly bind metal ions from aqueous solutions. The resulting changes of the electrochemical properties of the monolayers were monitored by impedance spectroscopy. The increased dielectric constant of the layer due to the complexation of ions results in an increase of the monolayer capacitance (C ML). Analysis of the response curves with a Langmuir isotherm enables ...