In this research, it reported a novel three-dimensional (3D) metallic hybrid system by introducing single-layer graphene (SLG) between silver nanoparticles (NPs) and silver nano-discs (NDs) arrays (Ag NPs/SLG/Ag NDs). By combining the plasmonic metallic nanostructures and the unique physical/chemical properties of graphene, Ag NPs/SLG/Ag NDs hybrid substrate was fabricated, and it exhibited extremely high surface-enhanced Raman scattering (SERS) performance. By tuning the diameter of Ag NDs, the SERS performance of Ag NPs/SLG/Ag NDs hybrid substrate has been systematically studied. The detection limit for rhodamine 6g (R6G) could reach the concentrations as low as 1 × 10^-12 mol/L, and the average enhancement factor (EF) of the Ag NPs/SLG/Ag NDs substrate could reach 5.65 × 10⁸. These advantages indicated that the Ag NPs/SLG/Ag NDs hybrid substrate could be regarded as a candidate for organic molecules detection under extremely low concentration. Besides, spatial Raman mapping of Ag NPs/SLG/Ag NDs with 2.5 μm diameter NDs showed the larger SERE signal existed around the rim of Ag NDs which was related to the localized surface plasmons. This phenomenon was contributed by a larger electromagnetic field which was tuned by Ag NPs and the edge of Ag NDs. This mechanism also has been confirmed by the electromagnetic simulation result.

In this paper, the study of using masks to directly generate large area, highly ordered and periodical nanostructure has been exhibited. Periodic Au nano-discs(NDs) arrays have been fabricated on top of graphene by using holey Si₃N₄ mask which is directly fixed on top of graphene and Au metal is deposited through the holes in mask by thermal evaporation method under vacuum condition. This fabrication method provides an easy, fast and cost efficiency way to generate periodical nanostructure. Also, Au nanoholes(NHs) structure has been studied by using holey Si₃N₄ as a template. The surface-enhanced Raman scattering (SERS) sensitivities of periodical Au NDs/graphene and graphene/Au NHs hybrid structures have been systematically studied. The internal mechanisms could be explained by chemical mechanism effect of graphene and electromagnetic mechanism effect of metallic nano-structures. The enhancement factors have been systematically investigated by varying the diameter and the thickness of Au discs and Au NHs. Raman mappings of Au NDs with 2.5 μm diameter illustrate that the larger SERS enhancements exist in the rim of NDs which has good agreement with the electric field simulation result. The SERE enhancement factors of fluorescein obtained from Au NDs/graphene substrates shows an improvement factor of 500% in comparison of graphene substrate. The calculated SERS enhancement factors of graphene/Au NHs achieve 1, 200% in comparison of graphene/planar Au film substrate.