Effect of pH on the Detection of Metal Ions Using a ISFET Sensor Modified with a Polysiloxane Film Substituted by Naphtyl-Cyclam

摘要

The cyclam ion-complexing molecule bound to poly(methylhydrosiloxane) was immobilized on the ISFET (Ion-Sensitive-Field-Effect-Transistor) surface using dip-coating technique, in order to make those potentiometric devices sensitive to transition metal cations. The wettability and morphology of the thin layers deposited at the transducer surface were characterized and an electrochemical assessment of the sensitivity to various cations was carried out at various pH. Potentiometric measurements show the binding of bivalent ions Cu~(2+), Ni~(2+), Cd~(2+), Co~(2+), Zn~(2+) and the trivalent ion Fe~(3+) in the pH range 5.0-7.7. Linear response with respect to the pM~(n+) was observed over two decades of concentration. A Nernstian response was obtained toward Fe~(3+) ions at pH = 6.0, towards Cu~(2+) ions at pH = 7 and towards Ni~(2+) and Zn~(2+) ions at pH = 7.7.