POLYSILOXANE BASED CHEMFETS FOR THE DETECTION OF HEAVY-METAL IONS

The development of polysiloxane based chemically modified field effect transistors (CHEMFETs) for heavy metal ions is described, Different p olar siloxane copolymers have been synthesized via an anionic copolyme rization of hexamethylcyclotrisiloxane, 3-(methacryloxy)propyl]pentame thylcyclotrisiloxane and pentamethylcyclotrisiloxanes with a pendant p olar group, e.g. ester, ether, amide, keto or cyano group, Well-struct ured monomodal molecular weight polymers were obtained with molecular weight distributions from 1.3 to 1.7. The siloxane copolymers were use d as sensing membranes for Ag+, Cd2+ and Pb2+ selective CHEMFETs, The intrinsic elastomeric properties of the polysiloxane membrane makes th e use of a plasticizer superfluous, which should have a favourable eff ect on the durability of these CHEMFETs, Siloxane copolymers with 3-cy anopropyl side groups are already intrinsically selective for Ag+ ions and this can be further enhanced by the addition of an Ag+ selective ionophore 1, Good Cd2+ selectivity was obtained for CHEMFETs with 3-ac etoxypropyl functionalized siloxane membranes in which the Cd2+ select ive ionophore 2 was incorporated; CHEMFETs with a [3-(p-acetylphenoxy) propyl]polysiloxane membrane containing the Pb2+ selective ionophore 3 showed good selective responses towards Pb2+.