Functionalization for Graphene-based Field Effect Transistor Biosensors

Graphene-based field effect transistors exhibit an excellent ability to detect bio-materials at extremely low concentration. These sensors utilize electronic properties of both graphene and semiconductor interfaces to obtain biodetection with high-sensitivity. In this study, we use hemoglobin protein to couple electrically with graphene and detect electrical signals in these devices. To fabricate these sensors, biochemical functionalization has been employed to ensure a high response from the deposition of the proteins on the surface. This process involves immobilizing anchor molecules to graphene through covalent bonding, then forming amide bonds between the anchors and bioreceptor molecules with high affinity to the bioanalyte. However, molecules with biochemical functionalization also interact with contaminated molecules in the protein solutions, producing unwanted electrical signals. We propose a combined method of electrical and optical techniques, which utilizes absorption properties of the proteins, biochemical functionalization, and optoelectronic properties of graphene field effect transistors to produce a high electrical response when light is illuminated on the surface of the biosensor-bioanalyte system. With this process, we find a high response which is specific to the proteins and depends on both the incident wavelength and concentration of the molecules.