Biosensing beyond Debye screening length using epitaxial graphene field-effect transistors on SiC substrate

We demonstrated the antigen detection beyond Debye screening length using antibody-modified epitaxial graphene field-effect transistors (FETs), which have been considered to be impossible because of the Debye screening length. The transfer characteristics of the graphene FETs with a single crystal epitaxial graphene film showed no concentration dependence of buffer solutions. The capacitance measurements in an epitaxial graphene FET also showed no concentration dependence, indicating that the solution-gate capacitance of the epitaxial graphene FET was independent on the Debye screening length. In addition, the minimum capacitance values were also almost independent for the concentration change. Since the Debye screening length depends on the ionic strength of the solution, which is proportional to the buffer solution concentration, the electrical characteristics of solution-gated epitaxial graphene FETs are almost independent on the Debye screening length owing to their small quantum capacitance. The antibody-modified epitaxial graphene FETs indeed detected the antigen, indicating that the epitaxial graphene FETs can detect the target beyond the Debye screening length without any complicated device fabrication processes and other desalted apparatuses.