Study Of The Surface Enhanced Raman Scattering Effect In Large-area ReS₂ Films

Surface-enhanced Raman scattering（SERS）,as a powerful molecular traceless detection technology,has attracted more and more attention from researchers in analysis applications.Two-dimensional（2D）transition metal dichalcogenides materials have recently been explored as possible SERS substrates.However,in comparison to the conventional noble-metal-based counterpart,most of the 2D materials have very small area for SERS measurement,which is a big limitation toward practical applications.Different from 2D materials,ReS₂ with low lattice symmetry as a SERS substrate endows more degree of freedom for exploring novel enhancement effects.In this thesis,we studied SERS of large-area continuous ReS₂ films on flexible mica substrate prepared by chemical vapor deposition.On this basis,we also tried to decorate Au NPs on the surface of ReS₂ film to prepare Au NPs/ReS₂ substrates to enhance SERS.The main contents of the study are as follows:1.Large-area continuous ReS₂ films with different thickness were prepared on mica substrate by chemical vapor deposition.Firstly,the SERS effect of the large-area ReS₂ film was proved by R6G probe molecule.The Raman enhancement effect of R6G molecule on the ReS₂ film with different thickness was studied,and the thickness-dependent SERS effect was confirmed.It was found that ReS₂ monolayer film shown the best SERS of R6G molecule with the detection limit of 10^-7M.2.The SERS of substrate-scale continuous ReS₂ monolayer films on flexible mica substrate was studied.The obvious Raman signal of R6G is detected on the monolayer ReS₂/mica with strong fluorescence quenching effect.It was found that the charge transfer between the target molecules and the atomically thin ReS₂can be modulated by the underlying substrate of ReS₂,resulting in greatly different suppressing level of FL background.Kelvin probe force microscopy revealed a large difference of surface potential between ReS₂/Si O₂ and ReS₂/mica,suggesting that the strong FL quenching of molecular on ReS₂/mica might be attributed to the inert surface of layered mica.The large-area ReS₂monolayer films on mica show a robust SERS performance after an exposure in air for one month and repeat bending for 1000times.3.The Au NPs/ReS₂ composite SERS substrate was prepared by using an ultra-thin anodic aluminum oxide（AAO）film through electron beam evaporation to prepare ordered Au nanoparticles（Au NPs）on the surface of the ReS₂ film.The SERS effect of R6G probe molecule on the substrate was studied.The lowest detection concentration of R6G probe molecule can reach 10^-7 M.Although it is not superior to the bare ReS₂ film substrate,it can enhance the Raman characteristic peak intensity of R6G molecule while effectively suppressing the fluorescent background.In addition,the influence of the thickness of the Au nanoparticles on the Raman enhancement was studied.The relative standard deviation of the measured Raman peak intensity on radom surface spot of the sample was calculated to be less than 10%,which means that Au NPs/ReS₂can be used as an effective SERS substrate for quantitative analysis and detection of test molecules.