Study on surface-enhanced Raman scattering substrates structured with hybrid Ag nanoparticles and few-layer graphene

We synthesized a set of surface-enhanced Raman scattering (SERS) substrates with hybrid-structures including Ag nanoparticles (AgNPs), AgNPs on top of few-layer graphene (AgNPs-FLG), AgNPs underneath few-layer graphene (FLG-AgNPs), sandwich structure (FLG-AgNPs-FLG) and few-layer graphene (FLG). The experimental results indicate that FLG can effectively protect AgNPs against aerobic oxidation (up to 60 days) and the sandwich structure achieved the best stability (the Raman intensity decreased by only 22.6% at ∼1363 cm−1, compared to a 94.03% decrease in the substrate of AgNPs). Besides, the defects of FLG caused the agglomeration of AgNPs and reduced the internal electric field of AgNPs, which ultimately led to a slight increase in the relative standard deviation (RSD) value and a minor decrease in the enhancement factor (EF). By studying local electric field properties of AgNPs and FLG, the principles of the interaction between AgNPs and FLG and also the change of the field and Raman intensity were analyzed theoretically and simulated. Through experiments and theoretical analyses, the hybrid structure of AgNPs and FLG is a potentially valuable and effective way to improve the performance of SERS substrates.