Plasmonic Coupling of AgNPs near Graphene Edges: A Cross-Section Strategy for High-Performance SERS Sensing

Fully exploiting plasmonic coupling of nanostructured metals is an effective method to promote surface-enhanced Raman scattering (SERS) performance for trace detection of molecules. Herein, we propose a cross-section strategy to maximize plasmonic coupling of silver nanoparticles (AgNPs) in a graphene-based membrane. Specifically, AgNPs are isolated by water-dispersible graphene (W-Gr) and enriched in the vicinity of W-Gr edges when assembling into a macroscopic membrane, thus affording AgNPs on the cross section with uniform and proper gaps in the vertical plane to generate maximal plasmon coupling. Moreover, the superior sensitivity (5 × 10–13 M for R6G) to most reported graphene–metal structures and the long-term stability against aerobic oxidation jointly make the cross-section of the AgNPs/W-Gr membrane a potential SERS substrate for trace-molecule detection. The revealed mechanism for AgNPs enrichment near edges highlights the importance of the flow-directed assembly process of W-Gr. This work provides new insight into the interpretation and utilization of two-dimensional materials as building blocks in high-performance SERS sensing.