Different siloxane copolymers have been used as membrane materials for Ca2+ selective chemically modified field effect transistors (CHEMFETs). CHEMFETs with 3-benzoylaminopropyl-functionalized polysiloxane membranes and 1 wt% borate anions are intrinsically selective for Ca2+ ions. This selectivity can be further enhanced by the incorporation of a Ca2+ selective 1,3 alternate calixarene which is functionalized with four amido groups. The highest Ca2+ selectivities were obtained with CHEMFETs containing this calixarene ionophore in 3-cyanopropyl-functionalized polysiloxane membranes.
Lugtenberg, R. J. W., Egberink, R. J. M., Engbersen, J. F. J., & Reinhoudt, D. N. (1997). Polysiloxane based CHEMFETs for selective detection of Ca2+ ions. Analytica Chimica Acta, 357(3), 225–229. https://doi.org/10.1016/S0003-2670(97)00571-0