Single-walled carbon nanotube field-effect transistors with graphene oxide passivation for fast, sensitive, and selective protein detection.

We report a novel technique to design an insulating membrane with attachment sites on top of single-walled carbon nanotubes (SWNTs) for achieving high sensitivity and selectivity in an SWNT field-effect transistor (FET) biosensor. Because electronic properties of SWNTs are extremely sensitive to the surface state, direct immobilization of proteins or DNAs onto SWNTs will generate surface defects through chemical reactions or physical adsorption, resulting in degradation of performance and instability of SWNT-FET biosensor devices. Here we demonstrate fabrication of novel FET biosensor devices using SWNTs as semiconducting channels, and a monolayer of graphene oxide (GO) membrane covered on the SWNTs as a passivating layer to avoid direct attachment of biomaterials on SWNTs, thereby preserving intrinsic electrical properties of SWNTs. Gold nanoparticles (Au NPs) are decorated on the GO layer for the covalent attachment of biotin, which is then used to selectively detect the target avidin. The passivation with GO layers can effectively lead to enhanced sensitivity of biosensor devices through increasing the on/off ratio of FET sensors.