▎ 摘　　要

We have fabricated graphene field-effect transistors (GFETs) to demonstrate highly sensitive electrical detection of sodium (Na) ions in electrolytes. Na ions in electrolytes affect the electrical potential of graphene channels, resulting in shifts toward a negative direction of the transfer curves in GFETs with increasing Na ion concentration. The transfer characteristics of GFETs indicated that Na ions in solutions were effectively detected over a wide range of concentrations from 1.0 nM to 1.0 mM. We also developed Na ion sensors based on GFETs to have a precise resolution of Na ion concentration to be utilized in the medical field. Time dependence measurement revealed that GFETs detected Na ions in real time. These results indicate that GFETs are potentially capable of being highly sensitive Na ion sensors. (C) 2011 The Japan Society of Applied Physics