ANION-SENSITIVE FIELD-EFFECT TRANSISTORS BASED ON POLYION COMPLEX BILAYERS

Polyion complex bilayers made of dioctadecyldimethylammonium poly(styrene sulphonate) were tested for their usefulness as anion-sensing membranes of ion-sensitive field effect transistors (ISFETs). Doping of the polyion complex with the corresponding quaternary ammonium chloride enhanced the sensitivity of the anion ISFET. Anion ISFETs based on the ammonium-doped polyion complex showed a near-Nernstian response in the Cl- activity range 0.1-1 x 10(-4) M. Annealing of bilayer membranes at a temperature higher than its crystal-to-liquid crystal transition temperature improved to some extent the selectivity for Cl- with respect to other anions. Doping of the polyion complex with the corresponding quaternary ammonium perchlorate also afforded ClO4--sensitive membranes for ISFETs.