Fabrication Of High Performance SERS Substrate Based On Self-assembly And Magnetron Sputtering And Its Property Study

Based on the elastic scattering of photons,Raman spectroscopy isusually used to identify various chemicals and biomolecules due to their unique fingerprint spectra.However,the traditional Raman spectra are limited by the small cross-section of the scattering,resulting in very small signal intensities and poor detection sensitivity.These shortcomings in a very long time hampered the development of Raman spectroscopy in real life applications.The discovery of Raman scattering（SERS）technology results in the increasing the sensitivity of Raman spectroscopy,even reaching the level of single molecule detection,which greatly promoted the application of Raman spectroscopy.This article focuses on the preparation of high-performance SERS substrates by fabrication and self-assembly of different nanoparticles as well as the combination of magnetron sputtering and displacement reaction method.SERS performance of different prepared substrates were evaluated for various probe molecules（including glycerol,Rhodamine 6G,5CB）as well as the reproducibility.The main contents of this paper are as follows:（1）Preparation of different sizes of gold and silver nanoparticles.Silver nanoparticles with different morphologies were prepared by reduction of silver nitrate and chloroauric acid by sodium citrate.By adjusting the concentration of reducing agent,the concentration of silver nitrate and chloroauric acid,the shape and size of the nanoparticles can be controlled.Spectroscopy and SEM are used to characterize the optimum experiment results:When the concentration of silver nitrate is 10^-3mol/L and the mass fraction of sodium citrate is 1%,the optimum amount of sodium citrate is 6-8ml.At this time,the particle size of silver nanoparticles is about 50nm and distribution is uniform.When the mass fraction of chloroauric acid is 0.01%and the mass fraction of sodium citrate is 1%,the adding amount of sodium citrate is 10ml,then the size of gold nanoparticles is about 30nm and the particles are almost all spherical as well as uniform.（2）Self-assembly of gold and silver nanoparticles.The surface of the cleaned silicon wafer was modified by silane coupling agent APTMS and the SERS substrate was fabricated by immersion in different concentrations of gold and silver colloidal sol.By SEM and AFM,it was found that self-assembled nanoparticles formed a neat arrangement on the surface of silicon wafer.SERS results showed that the detection limit of rhodamine was up to 10^-10 mol/L and the enhancement factor of glycerol was 10⁴ orders of magnitude.（3）Fabricated of high-performance SERS substrate by magnetron sputtering and metal replacement reaction method.The thin films of Zn and Ag-Zn were formed on the surface of glass slides by single-target sputtering and dual-target mixed sputtering,respectively,then the SERS active substrate with gold nanoparticles and gold-silver alloy nanoparticles was prepared by electrochemical substitution method.The experimental results show that the SERS substrate prepared by this composite method are homogeneous and reproducible and have significant enhanced effect on various probe molecules.