2D Au NPs Film-MoS₂ Hybrid And Its Optical Properties

MoS2,together with other Transition Metal Dichalcogenides(TMDs)have been drawing much attention for their extraordinary properties.Among these properties,the direct bandgap of monolayer MoS2(1.88eV)makes it possible for this material to maintain high photoluminescence(PL),which is important for diverse devices.However,restricted by the lack in portrait size,2-dimensional(2D)MoS2 gets limited light absorption,which further weaken the PL strength of 2D MoS2.Hence,many approaches have been taken to solve the problem,among which combining 2D MoS2 with localized surface plasmon resonance(LSPR)materials,like noble metal nanomaterials became a promising one.In this thesis,we first synthesized 2D MoS2 and single layered self-assembled Au nanoparticles(NPs)film.A simple method was utilized to construct 2D composite by two nanomaterials mentioned above.Then,a series of characterization,including PL spectra were taken to detect the 2D composite.Besides,the PL quenching and its reason were also analyzed.The major results are:(1)Influence of substrate on CVD grown MoS2 NSs was studied.Chemical vapor deposition(CVD)was used to synthesis MoS2 NSs.After a series of parameters with good repeatability was discovered,we chose Si with 300nm SiO2 layer(Si/SiO2),Si/SiO2,Si,quartz glass,Indium tin oxide(ITO)glass and mica for comparison in MoS2 NSs growth process.It turns out that when other factors in CVD process keep the same,Si/SiO2 is better for MoS2 NSs to form large lateral size and less atomic layers.(2)Synthesis of MoS2 nanosheets(NSs),self-assembled Au NPs film and their 2D composites.MoS2 NSs was prepared by chemical vapor deposition(CVD),with dozens of micrometers in lateral size and two atomic layers in vertical scales.Single layered self-assembled Au NPs film with 7nm thickness was prepared via solvent evaporation method.Then,the Au NPs film was directly fished out and covered onto MoS2 NSs to form a composite.(3)PL spectrum,Raman spectrum and reflection spectrum were carried out for both MoS2 NSs and Au NPs film-MoS2 composites.A strong PL quenching occurred in the composite compared with MoS2 NSs.By decomposing PL spectrum into different Lorentzian peaks and further reflection spectrum investigation,we believe there are two main reasons for the PL quenching in the composite:(a)electron transfer between Au and MoS2,which is caused by difference in bandgap structure between Au and MoS2;(b)compact Au NPs film caused absorption and reflection towards incident light and emission light.