Detecting a transition-metal ammine at tailored surfaces

Abstract

The fabrication of surfaces by forming Langmuir films, which incorporate amphiphiles containing hydrophilic 18-crown-6 (18C6) derivatives, at a gas/water interface is described. These Langmuir films can be transferred to a hydrophobised quartz crystal microbalance (QCM), using the Langmuir–Blodgett technique. The QCM response has been measured in aqueous solution as a function of the concentration of the transition metal complex [Co(NH ₃ ) ₆ ]Cl ₃ which was injected into a vial in which the film-coated QCM had been immersed. By comparing various surfaces covered with hydrophilic polyether and hydroxy functions and hydrophobic methyl groups, and by varying the composition of the films so as to increase the separation between the 18C6 macrocycles, it has been demonstrated that surfaces can be tailored that will enhance the binding of the [Co(NH ₃ ) ₆ ] ³⁺ trications.