Electrical Detection of Dna Hybridization Using Transistors Based on Cvd-grown Graphene Sheets

The interface between biosystems and nanomaterials is emerging for detection of various biomolecules and subtle cellular activities. Graphitic nanocarbon materials, such as carbon nanotubes, graphene oxide and graphene layers, have been employed as biosensors because they are biocompatible, extraordinarily sensitive and promising for large-area detection. In particular, the development of cost-effective and sequence-selective DNA detection is urgent for diagnosis of genetic or pathogenic diseases. The label-free electrical detection of the presence of biomolecules such as DNAs[1-2] and dynamic secretion of biomolecules such as ATP[3] and catecholamines[4] from living cells have been realized using carbon nanotube-based transistors. Graphene is another promising materials for these purposes. Comparing to onedimensional carbon nanotubes, graphene is expected to excel carbon nanotubes because it offers large detection area, biocompatibility, and exceptional and unique electronic properties such as ultra-high mobility and ambipolar fieldeffect. The developing of graphene-based biosensors becomes practical with the recent advent of chemical vapor deposition (CVD) of large-sized graphene film (up to wafer size)[5-7]. Here, we fabricate long-channel and large-sized graphene transistors by transferring the as-grown CVD graphene films from Ni to arbitrary substrates. We show that these devices show well-defined ambipolar transfer characteristics. They are able to electrically detect the hybridization of target DNAs to the probe-DNAs pre-immobilized on graphene with detection sensitivity of 0.01 nM. These devices are capable of distinguishing the single-base mismatch. The detection mechanism is attributed to the electronic–doping (n-doping) introduced by target DNAs, which is in clear contrast to the electrostatic gating mechanism used by graphene oxide based sensors[8].