Detection of uranium(VI) in aqueous solution by a calix[6]arene modified electrode

This work describes the attempts to develop a new type of modified electrode with high selectivity towards uranyl ions, UO22+. This goal has been addressed by binding derivatives of calix[6]arene, which is a macrocyclic molecule composed of six phenol units, known as “super uranophile”, to the electrode surface. Selective extraction of UO22+ onto the electrode surface, followed by a voltammetric measurement provides a quantitative uranyl analysis. Our initial approach to binding calix[6]arene molecules onto electrodes has involved an ionic derivative, 4-sulfonic-calix[6]arene, which was electrostatically attached to a positively-charged self-assembled monolayer of cysteamine (2-aminoethanethiol) on a gold electrode. The attachment of the 4-sulfonic-calix[6]arene to the cysteamine monolayer was verified by XPS, IR spectroscopy and capacitance measurements. Voltammetric experiments showed that uranyl ions can be preconcentrated and measured by these modified electrodes.