Study Of Optical Properties And SERS Of MoS₂/Metal Nanocomposite Structures

Surface-enhanced Raman scattering（SERS）has been used as an emerging label-free analysis technology since its discovery,because it can provide more structural information of detection molecules as well as high sensitivity and high accuracy,in recent years,extensive research and development have been made in biosensors,biological imaging and environmental monitoring.The precious metal material has good SERS performance and is a common SERS base material,however,this material has weak adsorption ability to some of the detection molecules and is susceptible to the background fluorescence generated by the detection molecules,so that the Raman scattering signal is interfered,at the same time,it will also cause loss of the substrate and performance degradation.As a typical graphene-like semiconductor material,molybdenum disulfide（MoS₂）has been used in SERS research because of excellent adsorption capacity and fluorescence quenching,but the study found that the enhancement effect of a single MoS₂ material is only about two orders of magnitude,which seriously restricts the research and application of single MoS₂ material in SERS.Recent studies have shown that the metal/MoS₂ nanocomposite structure can adsorb more detection molecules and generate plasmon resonance effects and electron transfer effects,resulting in an increase in Raman intensity,therefore,it is necessary to improve the SERS performance of the metal/MoS₂ nanocomposite structure as the SERS substrate.This paper focuses on the following research around the following contert:（1）The MoS₂ nanoflowers were prepared by hydrothermal method,and the Au-MoS₂ nanoflower composite structure was prepared by hydrothermal method and thermal reduction method,the related physical properties、Raman characteristics、SERS performance and SERS mechanism were analyzed.The study shows that the Au-MoS₂nanoflower composite structure has obvious enhancement effect on Rhodamine 6G（R6G）and crystal violet（CV）,and the minimum detection concentration of the above two dye molecules can reach 1fM.It is concluded that the SERS enhancement mechanism of the metal/MoS₂ composite structure is amplified by the physical enhancement of the metal and the chemical enhancement of the MoS₂.Finally,the Au-MoS₂ nanoflower composite structure was used as the SERS substrate to realize the practical application of SERS for residual CV molecules in aquatic products,the test results are in line with the CV maximum residue standard of 2 ng/g in European Union act 2002/675/EC.（2）The structure of MoS₂ film was prepared by chemical vapor deposition,and the Au-MoS₂ nano-array composite structure was prepared by chemical vapor deposition and electron beam lithography,the physical properties、Raman analysis and SERS performance of the above two structures were studied.The research shows that the Au-MoS₂ nano-array composite structure has excellent SERS enhancement effect,and the lowest detection concentration of CV molecules can reach 1fM,the accuracy of the detection result is high due to the ordered array structure of the substrate.Finally,the Au-MoS₂ nano-array composite structure was used as the SERS substrate to detect the residual CV molecules in aquatic products,the test results are in compliance with the CV maximum residue standard of 2 ng/g in European Union act 2002/675/EC,at the same time,it is proved that the substrate has high detection accuracy in practical applications.