DEVELOPMENT OF DURABLE K-SELECTIVE CHEMICALLY-MODIFIED FIELD-EFFECT TRANSISTORS WITH FUNCTIONALIZED POLYSILOXANE MEMBRANES()

Durable K+-selective chemically modified field effect transistors (CHE MFETs) with functionalized polysiloxane membranes have been developed. Polysiloxane membranes of different polarity, i.e., with different am ounts of (cyanopropyl) siloxane groups, incorporating a free or covale ntly bound hemispherand as the ionophore and free or covalently bound tetraphenylborate anions as ionic sites, were investigated for their p erformance as sensing membranes. The CHEMFETs based on polysiloxane wi th both ionophore and anionic site covalently attached to the membrane matrix showed K+ responses with an almost Nerstian slope in the range of concentration 10(-4)-10(-1) M in the presence of 0.1 M Na+ (log k( K,Na)(pot) = -3.2. Durability tests showed that these sensors respond satisfactorily in the desired range of potassium concentrations even a fter 10 months of continuous exposure to washing in a stream of tap wa ter.