Preparation And Application Of Silver Composite Surface-enhanced Raman Scattering Substrate

Surface-enhanced Raman scattering（SERS）is a non-destructive technology,with the ability to directly and ultra-sensitively identify trace molecules,as well as broad development prospects in the field of environmental detection,but noble metal structures with nano-scale rough surfaces can produce significant SERS effects.In this thesis,two kinds of surface-enhanced Raman substrates were prepared by different methods,and they were used as SERS substrate for detection and application.The main research conclusions are as follows:（1）Ag@C and 30 nm Ag nanoparticles were successfully prepared by low-temperature heating and self-assembly methods.Polyethyleneimine（PEI）,a positively charged polymer,assembles negatively charged 30 nm Ag particles on the surface of negatively charged Ag@C particles to obtain an Ag@C@Ag surface enhanced Raman substrate.This method is simple,convenient and easy to operate.Then,the Raman probe molecule Rhodamine 6G（R6G）was used to investigate the surface-enhanced Raman properties of the prepared substrate material,and then the application detection of the substrate was further conducted.After experimental investigation,it was found that the surface-enhanced Raman substrate of Ag@C@Ag prepared can detect a minimum of 10^-10M for R6G(LOD was close to 5.3×10^-11 M),and 10^-7 M for pesticide methyl parathion.The detectable concentration of folic acid in water was as low as 10^-8 M,and the LOD was close to 6.8×10^-9 M.In order to further understand the enhancement mechanism,finite difference time domain（FDTD）method was used to simulate the electric field enhancement intensity and explain the resulting mechanism.The simulation results were consistent with the experimental results.The Raman enhanced performance of Ag@C@Ag was higher than both of the Ag@C and 30 nm Ag nanoparticles.（2）A polyamide（PA）membrane was successfully prepared using electrostatic spinning technology,the method is simple to operate,the prepared spinning membrane is complete,continuous and compact,and has a layered structure.The PA/Ag composite membrane was obtained by immersing in solution containing silver nanoparticles of different particle sizes.The prepared surface was enhanced with a Raman substrate.The probe molecule Rhodamine 6G（R6G）was used to investigate the Raman properties of the substrate,and further tested with methyl parathion and folic acid.It was found that the prepared PA/Ag composite SERS substrate can detect R6G at a concentration of 10^-9 M,the 10^-7 M for methyl parathion,and 10^-8 M for folic acid.