Comparison of CVD-grown and exfoliated graphene for biosensing applications

During recent years, graphene has attracted growing interest for application in biology, particularly in the biosensing field for sensitivity enhancement. For the biosensing purpose, the graphene layers have to be uniform and have an accurately controlled thickness. Graphene quality may vary depending on the method of its production. Using Raman spectroscopy, an assessment was made of the quality and suitability of the use of CVD and exfoliated graphene for biosensors. The Raman spectra of graphene obtained by the chemical vapor deposition method were measured before and after transferring. We found that CVD graphene with single and bi-layer thickness has a uniform structure with lager area and a small number of defects. But the number of defects increases with an increase of the number of layers. Also, we found that for some samples with CVD graphene, sometimes it is difficult to determine the number of layers since the specific shape of the 2D peak is not always explicitly expressed. Furthermore, it was shown that the exfoliated graphene, although having fewer defects, have non-uniform structure, with smaller areas of monolayer graphene.