A novel urushi matrix sodium ion-selective field-effect transistor

Abstract

A durable sodium ion-selective field-effect transistor (ISFET) is proposed with Urushi as the membrane matrix. The sodium ion-sensing membrane is composed of sodium ionophore (ETH 227), di-2-ethylhexylphthalate, potassium tetrakis(p-chlorophenyl)borate and Urushi. The prepared Urushi matrix ISFET showed a linear response in the sodium ion activity range from 100 M to 10^−3.5 M and about 53 mV per decade change of sodium ion activity. The selectivity of the Urushi matrix ISFET was almost the same as that of the corresponding PVC matrix ion-selective electrode. The Urushi ISFET showed excellent stability with drift below 0.15 mV per hour and durability for over a month, because of strong adhesion of the membrane to the Si₃N₄ gate.