Double Ag nanowires on a WS₂ /graphene Heterostructure for surface enhanced Raman scattering

Developing high-performance surface-enhanced Raman scattering (SERS) substrates is essential for ultra-sensitive chemical sensing. In this study, a novel hybrid SERS platform was fabricated by integrating double-aligned silver nanowires (ag NWs) onto vertical heterostructures comprising triangular monolayer tungsten disulfide (WS₂) and graphene. By employing rhodamine 6G (R6G) as a probe molecule, the SERS comparisons in two groups of ML graphene versus WS₂/graphene heterostructure and ag/graphene versus ag/WS₂/graphene heterostructure reveal that the WS₂/graphene vertical heterostructure exhibits to be a better SERS performance than monolayer graphene. The enhancement factor and the limit of detection of the R6G for the ag/WS₂ /graphene were 6.055×10⁷and 1.0 × 10^-8 M, respectively. Notably, the Raman intensity of the R6G at the 1651 cm^-1 characteristic peak for the ag/WS₂ /graphene heterostructure is 2.8 and 10.9 times that of the ag/graphene and WS₂/graphene substrates, respectively. Moreover, the role of the WS₂ /graphene heterostructure in the SERS was investigated based on the density functional theory calculations. The remarkable SERS enhancement of the ag/WS₂ /graphene heterostructure stems from the synergistic coupling between ag NW-induced localized electromagnetic enhancement and WS₂/graphene-mediated charge-transfer enhancement. All the results were conducted in micro-scale on the same sample consisted of two aligned ag NWs with half on a WS₂ /graphene heterostructure and the other half on ML graphene. Additionally, the polarization dependence of the SERS of ag NWs-WS₂ /graphene heterostructure was also investigated.