Preparation Of Silver Nanoparticles And Surface Enhanced Raman Scattering Study

The high-performance SERS(Surface Enhanced Raman Spectroscopy,SERS)active substrate can avoid the interference of fluorescent background and improve the sensitivity of biochemical analysis.Therefore,it has broad application prospects in biochemistry,biophysics and molecular biology.In this thesis,a combination of magnetron sputtering and rapid thermal processing was used to prepare Ag spherical coronal nanoparticles with single Gaussian distribution and double Gaussian distribution on the surface of single crystal silicon,and their morphology at different annealing temperatures was studied.Evolution process,nucleation mechanism and its application in SERS substrates.The main results are as follows:1.Coronal Ag nanoparticles with different particle size and surface coverage were prepared by a combination of magnetron sputtering and rapid thermal annealing.Theoretical calculations and experimental results show that when the spherical coronal Ag nanoparticles have an average particle size of 45.2 nm and a surface coverage of 35.6%,the G peak as a SERS substrate has a 50-fold enhancement compared to the bare Si substrate.The preparation method is simple and easy to perform and has high repeatability.2.The mechanism of the formation of spherical coronal silver nanoparticles under the condition of rapid thermal annealing of silver nanofilm was explained.Due to the stress of Ag nano-film,the nucleation of each nano-particle can be calculated according to the change of free energy of the system in the thermodynamic analysis of film nucleation.The study found that when the nucleation work is the lowest,the surface diffusion is easy to proceed,and the spherical crown particles will spontaneously take precedence.In the FDTD simulation calculation,when the saturation angle is in the range of 90-180°,the local field of the contact surface of the spherical crown silver nanoparticles with the 145° immersion angle radius of 30 nm and the Si substrate is up to 23.3 V/m,and the theoretical enhancement factor can reach 2.94 × 105.3.Metal films with different thicknesses were prepared twice,and spherical S-shaped silver nanoparticle SERS substrzites with high repeatability and topographical double Gaussian curve distribution were obtained.By adjusting the order of the thickness of the metal nanofilm and the annealing process,the two deposited Ag nanofilms can be grown again on the basis of the first grown Ag nanoparticles.The localized field of nanoparticle coupling is enhanced by generating new particles and reducing the interstitial speice.Comparing the test samples,the experimental and simulation results show that the SERS effect of the particles deposited on the 2 nm SERS substrate after 3.5 nm deposition is the strongest.As a composite SERS substrate,it has 467 times Si surface enhancement as the SERS substrate G peak.Raman scattering ability and high repeatability.4.The relationship between the size and spacing of Ag particles and the local field distribution was simulated by FDTD solution software.It is found that when the particle size of small particles is 12 nm,the size of large nanoparticles is 36 nm,and the particle spacing is 6 nm,the SERS of the double-layer Ag particle substrate is significantly enhanced compared with the single-layer Ag particle substrate,and enhanced by 2.7 times.