“…In the mid-1980's, Izatt first investigated utilization of calixarenes (cyclic compounds constituted by four phenolic units linked by methylene groups, p-tert-butyl-calix [4]arene) for selectively separating cesium from other alkali cations [80,81]. In an effort to find better cesium extractants, a Commission of the European Communities study performed at Cadarache, France, looked at functionalized calixarenes and, particularly, dialkyl calyx [4]arenas-crowns [82][83][84].…”