Au Nanoparticle/WS2 Nanodome/Graphene van der Waals Heterostructure Substrates for Surface-Enhanced Raman Spectroscopy

This work explores superposition of the localized surface plasmonic resonance (LSPR) effect of Au nanoparticles (AuNPs) with that on transition metal dichalcogenide (TMD) WS 2 nanodomes (WS 2 –NDs) enabled by enhanced dipole–dipole interaction at van der Waals (vdW) interfaces in AuNP/WS 2 –ND/graphene heterostructures for surface-enhanced Raman spectroscopy (SERS) with high-sensitivity, The confirmation of such a superposition is first demonstrated in the enhanced graphene Raman signatures, such as the G-peak intensity by approximately 7.8 fold on the AuNP/WS 2 –ND/graphene over that of reference graphene sample, in contrast to 4.0- and 5.3-fold, respectively, on AuNP/graphene and on WS 2 –ND/graphene. Furthermore, Raman spectra of probe molecules of fluorescent Rhodamine 6G (R6G) were hired to quantify the enhanced SERS on AuNP/WS 2 –ND/graphene SERS substrates. At the R6G concentration of 5 × 10 –5 M, enhancement factors of ∼2.0 and 2.4 based on the R6G 613 cm –1 peak intensity are detected on the AuNP/WS 2 –ND/graphene with respect to that on WS 2 –ND/graphene and AuNP/graphene, respectively. The benefit of the superposition of the LSPR effects from the WS 2 –NDs and AuNPs results in high SERS sensitivity up to 1 × 10 –12 M on AuNP/WS 2 –ND/graphene, which is about an order of magnitude better than what’s on WS 2 –ND/graphene, and several orders of magnitude better than that on the AuNP/graphene and metal nanostructure/TMD (continuous layer) substrates. This result reveals the advantage of superposition of the LSPR effects from different nanostructures through design of vdW heterostructures. In addition, considering the AuNP/WS 2 –ND/graphene vdW heterostructures can be fabricated in the layer-by-layer growth developed in this work, the high-sensitivity SERS substrates are scalable and low cost for marketable devices in optoelectronics and biosensing.