Selective ion sensors based on ionophore-modified graphene field-effect transistors

Electrolyte-gated graphene field-effect transistors (FETs) were fabricated to demonstrate highly sensitive electrical detection of K or Na ions in a solution. Moreover, selective K ion sensors were fabricated by modifying graphene FETs with valinomycin, a selective K ionophore. The valinomycin-modified graphene FETs demonstrated highly sensitive, selective electrical detection of K ions in electrolytes. The K ions bound to the valinomycin in the graphene channel and affected the electrical potential of the channel. The transfer curves were shifted in a negative direction as the K ion concentration increased, indicating that K ions in solution were effectively detected over a wide concentration range, from 10 nM to 1.0 mM. The addition of Na ions did not cause any change in the transfer characteristics. We have thus demonstrated the potential utility of graphene FETs as highly sensitive, selective K ion sensors.