Biomolecule Detection in High Ionic Strength With Enhanced Sensitivity Using Graphene Nanogrid FET Immunosensor

Abstract

Detecting charges in high ionic strength solutions is a challenge due to the inherent problem of ionic screening in small Debye length. There have been some efforts to improve the sensing in high ionic strength buffer but the sensitivity and detection limit is poor. To address this challenge, we report high frequency sensing using smooth graphene nanogrid FET immunosensor. These sensors have certain intrinsic advantages: firstly, in the nanopores, the biomolecules usually reside within a distance shorter than the original pore radius which statistically raises the charge transfer probability between the biomolecules and the surface even at high ionic strength of the buffer and secondly, such a graphene nanostructure has a size dependent effective energy gap which increases the transconductance of the device. These features coupled with high frequency sensing have enabled detection down to 0.1 fMHep-B in a high ionic strength buffer (150mM) at 8 MHz with a sensitivity as high as 445.45%. This is an enhancement by more than 18 times compared to the existing reports.