Methods for the preparation and characterisation of a selenocyanate ion-sensitive field effect transistor with Urushi as the membrane matrix

Abstract

A selenocyanate ion-sensitive field effect transistor (ISFET) was fabricated from a silicon wafer with Urushi (natural lacquer) as the membrane matrix. The proposed ion sensor has excellent durability for over 2 months. The ISFET can be characterised by the relationship between the square root of the drain current and the logarithm of the ion activity in the saturation region of the ISFET. It was found that the linear response range of the Urushi ISFET was from 10^–5 to 10^–1M selenocyanate ion activity and the selectivity coefficients were almost the same as those of the Urushi ion-selective electrode.