Thin sensitive organic membranes on selective iron-ion sensors

The organic supramolecular compound synthesized from pyrochatechol units bound in the α-position of a linear dicarboxylic acid (AE6) previously used as a stable chelate iron(III) in solution is applied in this work as an ionophoric reagent on ion-sensitive field-effect transistor (ISFET) and electrolyte—insulator—semiconductor (EIS) structures for iron detection. The surface gate oxide (SiO2) sensitization of sensors was performed, using three deposition methods: chemical grafting to obtain an AE6 monolayer, deposition by vacuum sublimation of an AE6 thin film and incorporation in a polysiloxane gel membrane. Classical electrochemical measurements were made to test the sensitivity towards iron of the AE6 membranes, in EIS and ISFET structures. A Nernstian sensitivity, a good selectivity and a long lifetime were obtained for the evaporated layer and the gel membranes.