Modified poly(vinyl chloride) matrix membranes for ion-selective field effect transistor sensors

Abstract

Various membrane compositions, in which a poly(vinyl chloride)(PVC)-poly(vinyl alcohol) copolymer (copolymer VAGH) and silicon tetrachloride were incorporated as additional components in the classical PVC matrix membrane composition for ion-selective electrodes, were studied for their adhesion characteristics to the gates of field effect transistor devices used for the construction of ion-selective field effect transistors (ISFETs). These studies were carried out on a potassium ion-sensing system based on valinomycin with dioctyl adipate as plasticising solvent mediator.The inclusion of 10–25%m/m copolymer VAGH and 1%m/m silicon tetrachloride in the membrane casting solution was found to increase the adhesion of the plastic membrane to the gate, reflected by an increase in ISFET functional lifetimes of 4–5 d over those which did not contain VAGH and by ca. 10 d over those which contained neither VAGH nor silicon tetrachloride. Leaching of membrane components is suggested as a factor limiting the ISFET lifetimes in adhesion studies.