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

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 Cu2+ , Ni2+ , Cd2+ , Co2+ , Zn2+ and the trivalent ion Fe3+ in the pH range 5.0–7.7. Linear response with respect to the pMn+ was observed over two decades of concentration. A Nernstian response was obtained toward Fe3+ ions at pH = 6.0, towards Cu2+ ions at pH = 7 and towards Ni2+ and Zn2+ ions at pH = 7.7.