W₁₈O₄₉/Monolayer MoS₂ Heterojunction-Enhanced Raman Scattering

Abstract

Surface-enhanced Raman spectroscopy (SERS), a sensitive analytical technique that has single molecular sensitivity, has attracted continuous attention for both application and academic research. Semiconductor-based substrates with SERS activity present more practical applications, ranging from surface science to biological detection because of their lower cost and better biocompatibility compared with noble metals. However, the SERS performance of most semiconductor-based substrates is not significant. Herein, we propose the concept of semiconductor heterojunction-enhanced Raman scattering and design a vertical nanothickness heterojunction of W18O49/monolayer MoS2. As a result, the Raman signals of analyte Rhodamine 6G are detectable even with an ultralow concentration of 10–9 M on W18O49/monolayer MoS2 substrates. The enhancement factor is around 3.45 × 107. We confirmed from experiments and theory that the coupling of these two semiconductor materials could lead to dramatic enhancement of photoinduced charge-transfer processes, which enables giant heterojunction-enhanced Raman scattering.

A WS2-gold nanoparticle heterostructure-based novel SERS platform for the rapid identification of antibiotic-resistant pathogens

“…1F shows the absorption spectra of 2D-WS 2 , which shows some absorption at 400-650 nm and it is mainly due to the A1 and B1 excitonic transitions of WS 2 . 16,[20][21][22] The observed exitonic transition originates from the energy split of the valence-band and spin-orbital coupling, as reported before. 16,[20][21][22] In the next step we synthesized 0D-2D heterostructures using 2D-WS 2 and 0D-GNPs.…”

“…1D shows the powder XRD data from the heterostructure, which shows the presence of (002), (004), (006) and (008) reections for WS 2 , and (111), (200), (220) and (3111) reections for GNP. 17,[20][21][22]24 Fig. 1F shows the absorption spectra of the heterostructures which clearly indicate a broad plasmon band which is due to the aggregation of 0D-GNP on the surface of 2D-WS 2 as shown in the TEM images reported in Fig.…”

“…[13][14][15][16][17][18] 2D-WS 2 nanosheets were synthesized using a simple ultrasonication route from WS 2 powder. 16,[20][21][22] Briey, commercial WS 2 bulk powder was pelletised by a grinding miller for about 4 h, as shown in Scheme 1B. In the next step, WS 2 nanosheets were exfoliated through liquid exfoliation followed by intercalation.…”

“…[13][14][15][16][17][18][19][20] In the last two decades we and others have reported that extremely weak Raman signals can be enhanced signicantly using a proper design of the SERS substrate via the electromagnetic mechanism (EM) and chemical mechanism (CM). [16][17][18][19][20][21][22][23][24] Zero dimensional plasmonic nanoparticles such as gold and silver nanoparticles have been used extensively as SERS materials, where Raman intensity can be enhanced by $10 6 via EM & CM. [13][14][15][16][17][18][19][20] On the other hand, in the last few years SERS substrates based on two-dimensional (2D) transition-metal dichalcogenides (TMD) have been reported, where Raman intensity can be enhanced by $10 2 via CM as well as due to the resonance with near-and far-eld optical properties.…”

“…[13][14][15][16][17][18][19][20] On the other hand, in the last few years SERS substrates based on two-dimensional (2D) transition-metal dichalcogenides (TMD) have been reported, where Raman intensity can be enhanced by $10 2 via CM as well as due to the resonance with near-and far-eld optical properties. 11,16,[20][21][22][23][24] To take the advantages of the EM and CM effect from both types of materials, in the current manuscript we have reported the development of novel heterostructure material-based SERS using 2D WS 2 TMD and 0D plasmonic gold nanoparticles (GNPs). The reported data show a remarkably high SERS sensitivity of $10 À10 to 10 À11 M from the heterostructure.…”