Preparation And Plasmon Catalysis Study On MoS₂/Ag Composite SERS Substrate

In recent years,using semiconductors or two-dimensional materials to fabricate SERS substrates and study surface plasmon-catalyzed reactions have attracted much attention.However,the previous research works focused more on the reaction mechanism in the plasmon catalytic process,and the influence of the structural properties of SERS substrates on the reaction efficiency remains to be further studied.Here,single-particle Ag microspheres with a diameter of 2 ?m and Ag films with a thickness of about 16 nm were prepared by chemical reduction method and electron beam deposition respectively,and then MoS2 was covered on the substrates by pulsed laser deposition(PLD)technology to prepare new single-particle Ag@MoS2 and Ag@MoS2 film substrates.The thickness and crystallinity of MoS2 can be adjusted by controlling the time and temperature of PLD.Through XPS results,we determined that the SERS substrate covered with MoS2,SEM and TEM tests confirmed the size of the Ag particles and thickness of MoS2,Raman test methods confirmed that the crystallinity of MoS2 got better with the increase of PLD temperature.Single-particle experimental results revealed that thickness and crystallinity of MoS2 have a great influence on the SERS enhancement and surface plasmon catalytic reaction(4-NTP to DMAB)efficiency.The smaller thickness and the better crystallinity of MoS2,the stronger SERS effect of the substrate and the higher efficiency of the plasmon catalytic reaction.Conversely,when the thickness of molybdenum sulfide is greater,the worse the crystallinity,the worse the SERS effect of the substrate and the lower the efficiency of the plasmon catalytic reaction.When the thickness of MoS2 was smaller and the crystallinity was better,the stronger SERS effect and the higher efficient of plasmon catalytic reaction could be achieved on of the substrates.When the thickness of MoS2 was smaller and the crystallinity was better,on the contrary,the weaker SERS effect and the lower efficient of plasmon catalytic reaction could be achieved on of the substrates.The coverage of MoS2 weakened the electromagnetic enhancement of Ag microspheres.When the PLD time was 5 min,The efficiency of the reaction which on Ag@MoS2 substrate was larger than the efficiency was 1.8 on single Ag microsphere.It could be calculated by the ratio of product content to reactant content at equilibrium.The results of Ag@MoS2 film substrate experiments showed that the substrates had good uniformity.When the crystallinity of MoS2 was better,the stronger SERS effect and the higher efficient of plasmon catalytic reaction could be achieved on of the substrates.This rule was basically consistent with the results of single particle experiments.This study might open up a new way for surface plasmon catalysis and Raman enhancement.