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.

Plasmon-driven catalytic reaction (PDCR) as a part of photocatalysis has attracted immense attention. Due to the collective oscillation of free electrons at the surface of metallic nanostructures, the charge distributions store energy from the incident light that could transfer energy to molecules that promote photocatalysis. As an environment-friendly and green photocatalysis process, PDCR illustrates a brilliant future. In this study, the PDCR efficiency of photo-reducing 4-nitro-benzenthiol (4-NBT) dry film to p,p′-dimercaptoazobenzene (DMAB) in ambient conditions has been studied by using Ag nanodiscs (NDs) and Ag nanoparticles (NPs) as catalysts. The distribution of catalytic efficiency of 4-NBT to DMAB using an individual Ag ND catalyst has been illustrated using spatial Raman mapping. The result is direct evidence that the PDCR efficiency has a positive correlation with plasmon-induced electromagnetic field intensity. Additionally, time-dependent surface-enhanced Raman scattering (SERS) experiments reveal that the PDCR of 4-NBT to DMAB is reciprocal. The discovery in this research will aid to improve the PDCR performance and modulate the catalysis reaction for a high reduction of 4-NBT in industrial.

Surface-enhanced Raman scattering (SERS) as a label-free, non-contact, highly sensitive, and powerful technique has been widely applied in determining bio- and chemical molecules with fingerprint recognitions. 2-dimensional (2D) materials with layered structures, tunable optical properties, good chemical/physical stabilities, and strong charge–transfer interaction with molecules have attracted researchers’ interests. Two-D materials with a large and flat surface area, as well as good biocompatibility have been considered promising candidates in SERS and widely applied in chemical and bio-applications. It is well known that the noble metallic nanostructures with localized surface plasmon effects dominate the SERS performance. The combination of noble metallic nanostructure with 2D materials is becoming a new and attractive research domain. Until now, the SERS substrates combined with 2D materials, such as 2D graphene/metallic NPs, 2D materials@metallic core-shell structures, and metallic structure/2D materials/metallic structure are intensely studied. In this review, we introduce different kinds of fabrication strategies of 2D and 3D SERS substrates combing with 2D materials as well as their applications. We hope this review will help readers to figure out new ideas in designing and fabricating SERS substrates with high SERS performance that could enlarge the applicable domains of SERS.