Studies Of Graphene And Molybdenum Disulphide On Preparation, And Applications In Optoelectronics

Two-dimensional layered nanomaterials have attracted much attention in the scientific community,due to the unique structure,properties and wide application.Graphene and molybdenum disulfide are typical two-dimensional nanomaterials.Graphene,asan atom-thick nanomaterial,hasbecomeone ofthe most exciting research topics since it was first obtained by mechanical exfoliation in 2004.With a large number of excellent properties of graphene were excavated,the application researches about graphene have been triggered in both experimental and theoretical communities.Excellent electrical conductivity,optical transmittance and high mechanical strength enable graphene to be widely applied in flexible electronics,optics,and stretchable sensors.In particular,Benefiting from large specific surface area,good biocompatibility,and excellent affinity for biological molecules,graphene exhibit bright application prospect in the field of surface Raman enhancement and others.In recent years,the research about integration of two-dimensional graphene sheets into macroscopic 3D structures application of graphene has greatly expanded the application of grapheme,which has attracted wide attention.The monolayer of molybdenum disulfide,as one of transition metal molybdenum sulfide,is hexagonal crystalline nanomaterials composed of three layers of atoms.As graphene analogue,molybdenum disulfide possesses many excellent properties similar to graphene,so it displays great application potential in the field of surface Raman enhancement and optoelectronics.In addition,molybdenum disulfide possesses the band gap structure and is very suitable as optoelectronic device.Based on these studies,a series of work has been carried out around the realization and application of assembly of 2D graphene into macroscopic structures,as well as preparation and application of large-area molybdenum disulfide.In this study,we fabricated a 3D graphene macroscopic structure with a foam-like network on the foam nickel substrate,using template-directed CVD.Stretchable sensor applications were achieved by compositing foam grapheme with metal nanomaterials.Natural mica,was used as an ideal substrate for van der Waals epitaxy of MoS₂ belonging to hexagonal system,and large-area,high-quality three-layer molybdenum disulfide films was prepared by thermal decomposition of ammonium thiomolybdate.The applications of MoS₂ as saturable absorbers and SERS substrate were investigated.The main works was as follows:（1）We fabricated a 3D graphene macroscopic structure with a foam-like network on the foam nickel substrate,using template-directed CVD.In situ growth method was used to realize the composite of 3D foam graphene with silver nanoparticles,and flexible 3D AgNPs/G@Ni hybrid foam structure was fabricated.Using R6G molecules as a probe,3D AgNPs/G@Ni foam structures display excellent SERS performance.Importantly,3D AgNPs/G@Ni foam showed excellent flexibility and could be used to swab arbitrary curvilinear surfaces to achieve molecules concentration effect in the practical applicability.（2）We proposed a high-performance stretchable sensors based on the 3D Gr@NiP peasecod structure.An imaginative stamp transfer process was developed to achieve the combination of 3D Gr@NiP with elastomer.By controlling the thickness of growth time of graphene and etching time,a strain sensor with perfect sensitivity,stretchability,low detection limit,and excellent linearity was obtained.In addition,depending on the unique microstructure of 3D Gr@NiP,3D silver nanoflowers were synthesized by in-situ growth.Such AgNFs@Gr@NiP substrates demonstrated excellent Raman enhancement performance by the combined advantages of electromagnetic enhancement and the chemical enhancement.（3）We prepared large-area,high-quality three-layer MoS₂ thin layers on the mica substrate by thermal decomposition of ammonium thiomolybdate.The as-grown MoS₂ samples were demonstrated to be suitable as SERS substrates.Excellent SERS performance in terms of sensitivity was demonstrated by detecting R6G molecules,which would expand the application of MoS₂.（4）We realized the direct preparation of MoS₂ film on insulating substrate using thermal decomposition technology.Without complicated transfer process,by directly inserting MoS₂/mica in the laser cavity,a stable passively Q-switched mode-locked laser operation was obtained in a diode pumped Nd:GdVO₄ laser,which is achieved for the first time as far as we know.The results suggested that MoS₂ is a promising saturable absorber material.（5）We developed a stretchable 3D Au NPs@MoS₂@GF hybrid structure.Such stretchable SERS substrates displayed well stretchability.SERS performances are consistent undergoing different deformation.3D AuNPs@MoS₂@GF substrates could be used as cut-paste SERS substrates to achieve highly sensitive in-situ detection for MB molecules on the surface of tiddlers.