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

Durable K+-selective chemically modified field effect transistors (CHEMFETs) with functionalized polysiloxane membranes have been developed. Polysiloxane membranes of different polarity, i.e., with different amounts of (cyanopropyl) siloxane groups, incorporating a free or covalently bound hemispherand as the ionophore and free or covalently bound tetraphenylborate anions as ionic sites, were investigated for their performance as sensing membranes. The CHEMFETs based on polysiloxane with 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 after 10 months of continuous exposure to washing in a stream of tap water.