Thiacalixarene Derivatives Incorporated in Optical-Sensing Membranes for Metal Ion Recognition

This work deals with the evaluation of different thiacalix4]arene derivatives included in polymeric PVC membranes for the optical sensing of metallic cations. Two ligands have been studied: thiacalix4]arene (ligand 4) and its p-tert-butyl-derivative (ligand 2). Membranes including ligand 4 were tested for different metals and better results were obtained for Cd²⁺, Ag⁺, and Pb²⁺. In the case of films incorporating the neutral ionophore, ligand 2, a pH sensitive dye (ETH 2439), and an anionic additive were also added. A selective response to Ag⁺ was achieved in acetate buffer at pH 5.