Improvement in long-term stability of field effect transistor biosensor in aqueous environments using a combination of silane and reduced graphene oxide coating

A field-effect transistor (FET) biosensor that can directly detect target molecules is a promising diagnostic tool for healthcare and medical applications. However, the immersion of FET sensors in aqueous physiological environments for the long-term stability might damage the insulating layer of silicon dioxide, resulting in the degradation of the sensor response reproducibility. In this study, to improve the durability of the sensor response for long-term immersion in aqueous solution, we examined the effectiveness of reduced graphene oxide (rGO) coating on the gate insulator of FET sensors. The rGO coating was applied to the gate surface of the FET biosensor modified with an amino-terminated self-assembled monolayer by two steps: deposition of graphene oxide (GO) dispersion onto the monolayer-modified surface and subsequent thermal reduction of GO. The transconductance of both GO-coated and rGO-coated FETs remained unchanged after incubation under physiological conditions, suggesting that graphene prevents cations in the electrolytes from invading the gate insulator of the FET. Furthermore, functionalizing the rGO-coated FET surface enabled specific detection of target molecule.