Rationally Designed Graphene/Bilayer Silver/Cu HybridStructure with Improved Sensitivity and Stability for Highly Efficient SERS Sensing

摘要

A simple and cost-effective strategy was rationally designed to fabricate a special sandwich structure consisting of graphene, bilayer silver, and a copper plate, which was used as a surface-enhanced Raman scattering (SERS) substrate for highly efficient SERS sensing and detection of trace molecules. Silver dendrite (AgD) nanostructures were subsequently grown on a silver nanosphere (AgNS)/Cu surface to form a bilayer silver/Cu structure, which showed a 1.5-fold Raman enhancement compared to that of the AgNS/Cu substrate. After depositing graphene on the bilayer silver/Cu substrate to obtain a sandwich structure, a higher SERS enhancement and better durability were enabled. The SERS performances, measured by a portable Raman instrument, showed that the optimized sandwich structure substrate exhibited high SERS sensitivity to crystal violet (CV) and rhodamine 6G (R6G) with low limit of detection of 10^–9 and 10^–8 M, respectively. Such a sandwich-structured substrate exhibited good reproducibility across the entire detection areas with an average relative standard deviation less than 5.9%, which permits its reliablequantitative detection of CV and R6G molecules. In addition, grapheneboth effectively improved the SERS performances and protected Ag nanocrystalsfrom oxidation, which endowed the sandwich structure a long-term stabilitywith deviation of characteristic peaks’ intensity lower than3.6% after 25 days. This study indicates that the graphene/bilayersilver/Cu sandwich structure as a SERS substrate has a great potentialin detecting environmental pollutants.