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) WS2 nanodomes (WS2-NDs) enabled by enhanced dipole-dipole interaction at van der Waals (vdW) interfaces in AuNP/WS2-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/WS2-ND/graphene over that of reference graphene sample, in contrast to 4.0- and 5.3-fold, respectively, on AuNP/graphene and on WS2-ND/graphene. Furthermore, Raman spectra of probe molecules of fluorescent Rhodamine 6G (R6G) were hired to quantify the enhanced SERS on AuNP/WS2-ND/graphene SERS substrates. At the R6G concentration of 5 x 10(-5) M, enhancement factors of similar to 2.0 and 2.4 based on the R6G 613 cm(-1) peak intensity are detected on the AuNP/WS2-ND/graphene with respect to that on WS2-ND/graphene and AuNP/graphene, respectively. The benefit of the superposition of the LSPR effects from the WS2-NDs and AuNPs results in high SERS sensitivity up to 1 x 10(-12) M on AuNP/WS2-ND/graphene, which is about an order of magnitude better than what's on WS2-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/WS2-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.