Graphene Nanoporous FET Biosensor: Influence of Pore Dimension on Sensing Performance in Complex Analyte

Recently, there have been efforts to realize ultra-sensitive electrical biosensors on 3-D graphene nanostructures like nanowalls or nanopores which can enhance the surface area to volume ratio. But, the signal generated from the nanowall/nanopore structures for low concentration of biomolecules is often insufficient for current measurements and might not be reliable, especially for complex physiological analyte. This is the major drawback with respect to practical deployment of such sensors. In this paper, we have explored the impact of pore morphology on the sensing performance of label free, non-faradaic graphene nanoporous field effect biosensor with a view to achieve sub-femtomolar detection limit with an appreciable signal-to-noise ratio (SNR) in serum. Nine different pore geometries have been fabricated and the sensors have been experimented with Hep-B and Hep-C as specific and non-specific antigen, respectively. It has been observed that the graphene sensor with pore diameter of 35 nm and length of 160 nm has the maximum SNR in serum, in spite of not having the highest surface area to volume ratio and hence in nanoporous graphene structure, design of pore morphology should not be inclined towards increasing the surface area alone. The detection limit obtained with the optimized geometry is 0.1-fM Hep-B in a complex mixture of serum containing 1nM Hep-C as non-specific antigen.