Studying the sensitivity of graphene for biosensor applications

We have studied the response of graphene-film-based chips on SiC substrates (the relative change in the chip resistance) to coming into contact with fluorescein (С$_{20}$Н$_{12}$О$_{5}$) in a wide range of its concentrations in a phosphate-buffered saline solution: from 1 $\times$ 10$^{-3}$ to 1 $\times$ 10$^{4}$ ng/mL (seven orders of magnitude). Fluorescein detection seems to be a simple and cheap model experiment to study the sensory ability of graphene in the way of biochips manufacturing. It has been shown that chips with wide terraces on a surface with a step width of about 1000 nm and heights of up to 5 nm made it possible to construct the calibration dependences of chip response on fluorescein concentration.