Grafting of anion exchanging groups on SiO2/Si structures for anion detection in waters

Here, we report results of anion exchanger film, based on quaternary ammonium, obtained by grafting EPTMAC (glycidyltrimethyl-ammonium chloride) on silica transducer using AEAPTS (3-(2-aminoethyl-amino)propyltrimethoxysilane) coupling agent. The grafting product was characterized by H-1, C-13, Si-29 solid state NMR spectroscopy. Anion exchange on grafted SiO2/Si structures was monitored by impedance measurements: studying the flat band potential shift and the variation of capacitance in accumulation mode versus concentration of anionic species in solution. The grafted membrane exhibits a good affinity for different anions like CO32-, F-, I-, dye-SO3- with a detection limit of 10(-7) M. Applying site-binding model, the affinity constant of the anion species towards quaternary ammonium group is found to be 10(7) M-1. The size of the anion limits the sensitivity of the grafted SiO2/Si structures. (C) 2003 Elsevier B.V. All rights reserved.