Solution-Gated Epitaxial Graphene as pH Sensor

A solution-gate field effect transistor (SGFET) has been fabricated on few-layer graphene (FLG). The ideally polarizable graphene/aqueous interface allows the capacitive charging of the surface by hydroxyl (OH-) and hydroxonium ions (H3O+). The conductivity versus gate potential curve exhibits ''V'' shaped ambipolar transfer characteristics of graphene, with hole and electron mobilities of 3600 cm(2)/Vs and 2100 cm(2)/Vs, respectively. The shift of the negative gate potential with pH shows a supra-Nernstian response of 99 meV/pH. Our work points to the potential application of graphene in ultrafast and ultralow noise chemical or biological sensors.