Chemical and biological sensing applications based on graphene field-effect transistors

Chemical and biological sensors based on graphene field-effect transistors (G-FETs) were investigated. A single-layer of graphene was prepared by mechanical cleavage of natural graphite. The G-FETs were driven by a reference-gate operating in buffer solution, and exhibited very good transport characteristics. The G-FETs detected the pH value of the solution with high precision. The Dirac point shifted in the positive direction with increasing pH of the solution. The detection limit (signal/noise = 3) for measuring changes in the pH of the solution was estimated to be 0.025, indicating the high sensitivity of the G-FETs. Moreover, the devices electrically detected proteins with different charge types. The drain current decreased (increased) when positively (negatively) charged proteins were added to the solution. These results indicate that the G-FETs are among the most suitable candidates for FET-based chemical and biological sensors.