Covalent attachment of streptavidin to two dimensional magnetic nanocomposite enhances surface enhancement Raman spectroscopic signal.

In this work, we report that covalently attached protein to graphene oxide/magnetite (rGO-Fe3O4) nanocomposites can act as a substrate for surface-enhanced Raman spectroscopic studies. The substrate rGO-Fe3O4 synthesized by hydrothermal process was modified with a fluorescently labeled protein, streptavidin (Strp), using silane chemistry. The modification was confirmed by confocal fluorescence microscopy and Fourier-transform infrared spectroscopy, where the fluorescence of the conjugated protein and the presence of the additional peaks were visualized, respectively. The transmission electron microscopy demonstrated a wide distribution of Fe3O4 nanoparticles on rGO sheets. In addition, when the Raman peaks of these bio-nanocomposites (rGO-Fe3O4-Strp) were compared with the GO-Strp sheets and Fe3O4-Strp nanoparticles, an active substrate-mediated surface enhancement Raman spectroscopic effect was observed. It suggests that covalently attached protein on rGO-Fe3O4 nanocomposite substrates acts as a better platform for biosensing application than bare GO sheets or Fe3O4 nanoparticles. [ABSTRACT FROM AUTHOR]