Dual-Gate Enhancement of the Sensitivity of miRNA Detection of a Solution-Gated Field-Effect Transistor Featuring a Graphene Oxide/Graphene Layered Structure

We prepared a solution-gated graphene transistor (SGGT) incorporating a graphene oxide/graphene (GO/G) layered structure as the active material for the sensitive and specific detection of miRNA without labeling. The GO/G layered structure was formed through atomic layer oxidation of bilayer graphene, where the top layer of graphene was exclusively oxidized, while the characteristics of the bottom layer of graphene were preserved. The top layer of GO served as a functionalized graphene for the covalent immobilization of DNA probe units on the surface of the active material, and the bottom layer of graphene served as a transducer, with the Dirac point in the transfer curve shifting during the detection of miRNA. We observed a good linear electrical response in the Dirac point shift toward miRNA-21 at concentrations in the range from 10 fM to 100 pM. The sensitivity of the GO/G-based SGGT having only one solution gate was 19.26 mV/decade; it greatly improved to 33.65 mV/decade when applying a dual gate due to the gate-controlled doping achieved by the back gate. The biosensor also demonstrated good selectivity for the detection of miRNA-21 over a four-base-mismatched miRNA and good specificity when measured in human serum albumin.