UREA SENSITIVE FIELD-EFFECT TRANSISTORS BASED ON DITHIO GROUP-CONTAINING LANGMUIR-BLODGETT MEMBRANES

2-(Octadecyldithio)pyridine (1) and 5-(octadecyldithio)-2-nitrobenzoic acid (2) were synthesized in order to prepare Langmuir-Blodgett (LB) membranes which possess reactive dithio groups on the surface for further modification with enzymes. The monolayer membrane, composed of 1 or 2, was deposited successfully on an ion-sensitive field effect transistor, and the membrane surface was modified with urease covalently by a thiol-disulfide exchange reaction. The LB membrane-based sensor 2 showed a better potentiometric response to urea than that of the membrane-based sensor 1. The results are discussed on the basis of the reactivity of the dithio groups to urease at the membrane surface.