Potassium Ion-Selective Field Effect Transistor with Urushi as the Membrane Matrix

Abstract

A durable potassium ion-selective field effect transistor (ISFET) with an Urushi matrix membrane was fabricated. The potassium ion-sensing membrane is composed of valinomycin, di-2-ethylhexylphthalate, potassium tetrakis-(p-chlorophenyl)borate and Urushi. The best composition for the potassium ion-sensing membrane was determined with the results of electrochemical characteristics of Urushi ion selective electrodes. The optimal Urushi mixture was coated onto the gate region of the device, which was fabricated from a silicon-on-sapphire (SOS) wafer. The Urushi SOS/ISFET showed a linear response in the potassium ion activity range from 10⁰mol dm^-3 to 10^-4mol dm^-3 and about 50mV per decade in potassium ion activity. The prepared Urushi SOS/ISFET has good durability, for over a month, because of the strong adhesion of the Urushi membrane to the Si₃N₄ gate.