Tuning the SERS activity and plasmon-driven reduction of p-nitrothiophenol on a Ag@MoS₂ film

The combination of plasmonic metal nanostructures with semiconductors has been widely applied in plasmon-driven photocatalysis. Here, a uniform Ag@MoS₂ hybrid film is fabricated by depositing MoS₂ onto a thin Ag film via the pulsed laser deposition (PLD) technique. The thickness and crystallinity of MoS₂ can be adjusted by controlling the PLD deposition time and temperature, respectively. With the assistance of surface-enhanced Raman scattering (SERS) analysis, the Raman enhancement uniformity of the substrate and plasmon-driven reaction of p-nitrothiophenol (PNTP) dimerizing into p,p′-dimercaptobenzene (DMAB) are carefully studied on Ag@MoS₂ film substrates with different MoS₂ crystallinities. The Raman enhancement decreases with increased MoS₂ thickness, due to the weakened electromagnetic field enhancement as suggested by finite-difference time-domain (FDTD) simulations. The increased crystallinity of MoS₂ can efficiently accelerate the hot electron transfer process, resulting in the enhancement of SERS activity and the improved efficiency of the plasmon-driven reaction. This study may pave the way for the design of other uniform metal-semiconductor hybrids for use as SERS substrates and photocatalysts.