Preparation And Study Of Molybdenum Disulphide Application In Surface Raman Enhancement And Laser Mode-Locked

As a typical transition metal sulfide,molybdenum disulphide（MoS₂）has six-square layer structure.Compared to graphene,which is a two-dimensional（2D）material,molybdenum disulphide has a 2D layer structure and the band gap can be adjusted.A single layer of molybdenum disulfide is a direct band gap,the band gap of 1.9 eV,and the multilayer of molybdenum disulfide is an indirect band gap,the band gap of 1.3 eV.All of these features are absent from graphene.Not only that,the advantage of molybdenum disulfide in physics,materials,optical device and so on many aspects are shown in the past 2D materials do not have,in such aspects as new type of inorganic functional materials application has important significance.Because of its high sensitivity,fast response and specificity of detection,surface enhanced Raman scattering（SERS）as a powerful inspection tool is widely used in chemical and biological analysis,which has attracted widespread attention in recent years.Molybdenum disulphide has high phototransmission,chemical stability,biomolecular affinity and its ability to synthesize at low temperature.It is undoubtedly used as the ideal material for SERS detection.As the surface enhancement Raman scattering effect of molybdenum disulphide has been discovered by scientists,the study of molybdenum disulphide as the surface Raman enhancement substrate has entered a new field.In recent years,a series of progress have been made in the study of molybdenum disulphide as the surface enhancement Raman scattering substrate,but most of these studies are based on two-dimensional space.Compared with traditional two-dimensional substrates,three-dimensional molybdenum disulfide substrates with nano porous structures and higher specific surface area,can effectively increase the number of"hot spots",and can be used to improve the SERS signal sensitivity.And for this purpose,we prepared a new type of three-dimensional molybdenum disulfide/gold nanoparticle compound Raman enhancement substrate using thermal decomposition method.The size of the gold nanoparticles can be controlled by changing the concentration of the chloroauric acid solution.By using rhodamine 6G,fluorescein and gallic acid as the probe molecules,we tested the SERS properties of the composite substrate.The experimental results shown that the composite substrate of the gold nanoparticles with three-dimensional disulfide exhibited excellent detection performance.Using of finite difference time domain method,we have established the electric field theory model of three dimensional molybdenum disulfide composite gold nanoparticles.Through the theoretical simulation calculation,SERS characteristics of the compound substrate was further verified.In addition,molybdenum disulfide has the advantages of ultra-fast nonlinear optical response and excellent saturation absorption characteristics,and is widely used in the preparation of saturable absorbers.However,the thermal conductivity of the saturable absorptive prepared by molybdenum disulphide is poor,and the threshold value of the anti-light injury is low,which reduces the service life of the saturable absorber.The high resistance of light injury threshold and thermal conductivity of the saturable absorber prepared by graphene can effectively compensate the deficiency of the saturable absorber of molybdenum disulfide,but the saturable absorber has low absorption of light.In this paper,graphene and molybdenum disulphide were combined to prepared a saturable absorber which has graphene/disulfide heterostructure.This kind of compound can be used for the study of laser mode-locking,which has the advantages of simple preparation process and controllable layer number of graphene and molybdenum disulfide.