High performance surface-enhanced Raman scattering sensing based on Au nanoparticle-monolayer graphene-Ag nanostar array hybrid system

Abstract

The hybrid system combining graphene with plasmonic metal nanoparticles (NPs) has been of great interest owing to its excellent sensing capacity to be used as surface-enhanced Raman scattering (SERS) substrate. Here, we report an efficient SERS substrate by sandwiching monolayer graphene (1LG) between Au NPs and electron beam lithography-fabricated Ag nanostar arrays (NSAs). The design has integrated the orderness and strong plasmonic effect of Ag NSAs, the atomic thickness, mechanical flexibility and biological compatibility of graphene, as well as the chemical stability of Au. Calculations of finite element numerical simulations revealed that the Au NP-graphene-Ag NSA hybrid system generated high-density hot spots with strong electric field enhancement through the multi-dimensional couplings of plasmonic metal NPs. The fabricated Au NP-1LG-Ag NSA hybrid structure Exhibits 137-fold enhancement of the Raman response of graphene, and the limit of detection is 0.1 pM for rhodamine 6G molecules, which can be attributed to the extremely strong electric field enhancement and chemical enhancement of graphene. Furthermore, the Au NP-1LG-Ag NSA SERS substrate has achieved the simultaneous detection of rhodamine 6G and methylene blue. This work opens up an avenue for the rational design and fabrication of graphene-plasmonic hybrids for SERS sensing applications.