Graphene and Graphene Oxide Applications for SERS Sensing and Imaging. 
Surface Enhanced Raman Spectroscopy (SERS) has a long history as an ultrasensitive platform for the detection of biological species from small aromatic molecules to complex biological systems as circulating tumor cells.  Thanks to unique properties of graphene, the range of SERS applications has largely expanded.  Graphene is efficient fluorescence quencher improving quality of Raman spectra.  It contributes also to the SERS enhancement factor through the chemical mechanism.  In turn, the chemical flexibility of reduced graphene oxide (RGO) enables tunable adsorption of molecules or cells on SERS active surfaces.  Graphene oxide composites with SERS active nanoparticles have been also applied for Raman imaging of cells.  This review presents a survey of SERS assays employing graphene or RGO emphasizing the improvement of SERS enhancement brought by graphene or RGO.  The structure and physical properties of graphene and RGO will be discussed too.