Graphene sandwiched platform for surface-enhanced Raman scattering

The graphene-plasmonic metal nanoparticle (NP) hybrid system has attracted much attention for its potential capacity to be used as surface-enhanced Raman scattering (SERS) substrate. Here, we fabricated a SERS substrate by sandwiching monolayer graphene (1LG) between gold (Au) NPs and silver (Ag) nanoarrays (NAs). With modulation of the structural parameters, we have obtained Ag NAs with a gap between the flower-shaped Ag particles as small as 14 nm. Finite element numerical simulations revealed that the Au NP-graphene-Ag NA structure generates high-density hot spots with strong electric field enhancement through the couplings of plasmonic metal NPs. Benefit from the strong electric field enhancement and chemical enhancement, the prepared Au NP-1LG-Ag NA hybrid structure exhibited excellent SERS activity of high sensitivity with the detection limit as low as 0.1 pM for Rhodamine 6G. Moreover, we has achieved the simultaneous detection for both methylene blue and Rhodamine 6G molecules by using the as-prepared Au NP-1LG-Ag NA structure. These results may render the graphene-sandwiched hybrid system to function as a promising tool for SERS sensing applications.