Effect of chemical and structural feature of graphene on surface enhanced Raman scattering

Graphene nanomaterial has been reported as a chemical mechanism based surface-enhanced Raman scattering (SERS) substrate which has advantages of accuracy in the peak assignment with less peak shift and broader choice in the laser sources. Here we present a systematic study to investigate the effect of graphene oxide (GO), reduced graphene oxide (RGO), two- and three-dimensional (2D and 3D) graphene structure as well as their nanocomposites with gold nanoparticle (Au NP) as a SERS substrate to detect Rhodamine 6G (R6G) molecules. Compared with a glass substrate, the Raman signals were enhanced by 1.6 x 10(2) and 1.0 x 10(2)-fold in the 2D GO and 2D RGO, respectively, while 3D GO structure shows 2.2 x 10(2)-fold increase in the intensity over the glass substrate. These results imply that the GO is a better SERS substrate than the corresponding RGO, and the 3D structure of GO improves the sensitivity more than the 2D GO sheets by 1.4-fold due to the local electromagnetic effect derived from the oxygen-containing functional groups and the 3D morphology of GO. The Au NP composite with the 2D GO and 3D GO shows the increased Raman signal over the 2D GO and 3D GO by 5-fold and 3.8-fold, respectively, suggesting the synergistic effect of the Au NP on the graphene in the SERS measurements. These results imply that the optimization of the structural feature and chemical modification of the graphene is necessary to maximize the capability of graphene as a SERS substrate to detect various chemical and biomoleculs with high sensitivity.