A non-water-soluble modified β-cyclodextrin for sensitive electrode

Partially benzylated β-cyclodextrins (β-CDs) are deposited with no coupling agent on the silica surface of a wafer which was used as an electrolyte–insulator–semiconductor (EIS) heterostructure to detect cations in aqueous solution. The sensitivity of the EIS devices has been tested for Ca2+, Cu2+, K+ and heavy metal cations Pb2+ and Cd2+. The results showed a Nernstian response towards Pb2+ as found with β-cyclodextrins incorporated in gel membrane, with good selectivity. The benzylation of the β-cyclodextrins did not affect the complexation properties of the molecule. However, a considerable capacitive effect should be taken into account. The results were compared to a previous work where the β-CD molecules were fixed onto silica insulator surfaces obtained by means of either one of these two ways: chemically grafted to polymethyl-hydrosiloxanes (PMHS) chains, or physically entrapped in plasticized poly(vinyl chloride) (PVC).