Graphene coated nanoporous silicon immunosensor for food toxin detection

In this paper, we report a graphene based nanoporous silicon immunosensor for detection of aflatoxin B1 (AFB1). The binding density of antibodies on graphene coated nanoporous silicon is estimated by standard optical density method and compared with the conventionally silanized nanoporous silicon substrate. It is observed that the binding capability of antibody on graphene based substrate is nearly 1.5 times higher than that on the conventional substrates. With the application of different concentration of AFB1 in the range of 1 fg/ml-1 pg/ml the impedance response of this biosensor is experimentally verified. It is observed that the impedance decreases with frequency as reported for only nanoporous silicon sub-strate. However the sensitivity exhibits the presence of both minima and maxima with frequency unlike the previous report. Further the maximum value of sensitivity for AFB1 detection is 1.3 times more than that compared to the ordinary silicon substrate. Thus graphene coated nanoporous silicon substrate is capable of detecting toxin even in sub-femtomolar concentration with distinct frequency characteristics.