Modulating the Linker Immobilization Density on Aptameric Graphene Field Effect Transistors Using an Electric Field.

Aptameric graphene-based field-effect transistors (A-GFETs) always employ linkers, which could immobilize on graphene through π-π stacking between contained pyrenyl groups and graphene, to anchor aptamers. Aptamer density is closely associated with the A-GFET sensitivity and determined by the linker density. Using known linker immobilization methods, the linker density is random, uncontrollable, and limited. In this work, we propose a novel linker immobilization method which can be used to effectively modulate the linker density using an electric field and further bridge the relationship between the linker density and the A-GFET sensitivity. Here, polar molecule 1-pyrenebutanoic acid succinimidyl ester (PASE) is used as a linker representative. In the electric field, PASE is arranged regularly with the electron-rich pyrenyl group forced toward graphene in the solution due to electrostatic repulsion, thereby making it possible to modulate the quantity of PASE molecules that could interact with graphene by tuning the electric field application and then realizing the regulation of the A-GFET sensitivity. Experimental results indicate that the limits of detection (LODs) of A-GFETs for detecting interleukin-6 (IL-6) and insulin can be significantly improved to be 618 and 766 fM, respectively, by applying an electric field at -0.3 V for 3 h during PASE immobilization.