CESIUM-SELECTIVE CHEMICALLY-MODIFIED FIELD-EFFECT TRANSISTORS WITH CALIX[4]ARENE-CROWN-6 DERIVATIVES

Calix[4]arene-crown-6 derivatives (1-3) in the 1,3-alternate conformat ion, incorporated in poly(vinylchloride) membranes of CHEMFETs, exhibi t good Cs+-selectivity and Nernstian behaviour. The Cs+-selectivity ov er Na+, i.e., log K-Cs,Na(pot) = -3.3, is slightly better than observe d for bis(18-crown-6) derivatives (log K-Cs,Na(pot) = -3.0). The CHEMF ETs respond sub-Nernstian in the presence of NH4+: and K+. Model calcu lations show that this can be explained by the small difference betwee n the stability constants of the Cs+- and K+-complexes and by the high partition coefficient of NH4+ in favour of the membrane phase, respec tively.