Plasmonic Au Nanoparticles on 2D MoS₂/Graphene van der Waals Heterostructures for High-Sensitivity Surface-Enhanced Raman Spectroscopy

Abstract

A novel substrate consisting of a 2D MoS2/graphene van der Waals (vdW) heterostructure decorated with Au nanoparticles (AuNPs) was developed for surface-enhanced Raman spectroscopy (SERS). A transfer-free chemical vapor deposition process was employed for layer-by-layer fabrication of graphene, followed with MoS2 directly on wafers of SiO2/Si without any metal catalyst. AuNPs were deposited on the MoS2/graphene via in situ electron-beam evaporation of Au at an elevated temperature in the range of 300–350 °C under high vacuum. Rhodamine 6G (R6G) was used as an SERS probe molecule with a SERS sensitivity of 5 × 10–8 M using a nonresonance 633 nm laser, which is an order of magnitude higher than that reported on the AuNPs/graphene substrate using the same excitation. A higher SERS sensitivity of 5 × 10–10 M was obtained using resonance 532 nm laser excitation. The observed SERS sensitivity enhancement can be attributed to the combination of the electromagnetic mechanism of the plasmonic AuNPs and the chemical mechanism of the AuNPs/MoS2/graphene vdW heterostructure via enhanced interface dipole–dipole interaction as compared to graphene or MoS2 only as suggested by a density functional theory calculation. Therefore, this AuNPs/MoS2/graphene vdW heterostructure is advantageous to practical applications in optoelectronics and biosensing.

Enhancing light‐matter interaction in 2D materials by optical micro/nano architectures for high‐performance optoelectronic devices

“…Plasmonic metallic structures hybridized with other 2D materials, such as MoS 2 , GaTe, MXene, and 2D heterostructures also exhibit good SERS effects in terms of sensitivity, stability, and signal uniformity. [94][95][96][97] SPR sensors have been widely adopted for investigating molecular interactions and clinical application by monitoring the change in refractive index on the chip surface (usually Au film). 98 However, their sensitivity is limited owing to the poor adsorption of analytes on the Au surface.…”

“…This is particularly important for the detection of specific molecules that do not adsorb effectively on bare Au. Plasmonic metallic structures hybridized with other 2D materials, such as MoS 2 , GaTe, MXene, and 2D heterostructures also exhibit good SERS effects in terms of sensitivity, stability, and signal uniformity 94‐97 …”

Molybdenum disulfide–graphene van der Waals heterostructures as stable and sensitive electrochemical sensing platforms

“…Vertical interfacing of dissimilar atomic layers to form van der Waals (vdWs) structures has received enormous potential from the recent past, and a variety of synergetic effects due to charge redistribution and structural changes have been observed from such structures [25][26][27]. Such structures stabilized in sub-nanometre separation have sharp electronic boundaries [28] and it leads to inter-layer charge transfer within the layers of different work functions [29].…”

Hybrid Plasmonics and Two-Dimensional Materials: Theory and Applications

“…R6G in a concentration of 5 Â 10 À10 was detected when using 532 nm laser in resonance with the nanoparticles. 150 MoS 2 nanosheets chemically exfoliated using NaK metal alloy also provide a possible platform for SERS detection. The hybrid NaK-MoS 2 plasmonic-2D structure allows the detection of R6G down to the concentration of 10 À9 M. 151…”