Single-step Preparation And SERS Properties Of Porous Silicon Composite Gold Nano-Dendrite Structure

The optical detection technology based on the Surface-Enhanced Raman Scattering(SERS)of the substrate material is widely used in chemical analysis,biological sensing and other fields.However,as the limit of detection continues to decrease,higher requirements are placed on the surface enhanced Raman scattering performance of the substrate material.In recent years,porous silicon and its composite materials with large specific surface area,easy to adjust pore size and biocompatibility are considered to be one of the most competitive substrates for SERS biological activity detection.This paper innovatively proposed a single-step rapid preparation method of porous silicon-gold nano-dendritic SERS active substrate,which can be used to detect the low-concentration(10^-7 mol/L)of Hg(?).The main contents of the paper are as follows:First,using the finite element analysis method,the surface plasmon effect model of the double gold nanospheres was established in the COMSOL software,and the influence of different gold nanostructure shapes and size parameters on the near-field enhancement was studied.The results showed that the smaller the gap between nanospheres,the higher the electric field enhancement.When the incident wavelength was 532 nm,the distance of the nano gap was 2 nm,and the radius of nanospheres was100 nm,the bimetallic gold nanospheres can obtain the maximum electric field intensity E_max=33 V/m,the enhancement factor was about 1.18×10⁶.At the same time,in order to simulate the SERS enhancement of the micro-nano structure of gold dendrite,a simplified model of the nuclear-satellite gold nanostructure assembly was established.The results showed that the maximum electric field intensity E_max=43.6 V/m can be obtained at the same incident wavelength,the enhancement factor was about3.6×10⁶,demonstrating the gold nano-dendritic structure has better SERS activity.Secondly,based on the electrochemical etching method,the chloroauric acid solution was added into the etching solution to realize the one-step rapid preparation of the porous silicon-gold dendritic SERS substrate.The effect of the concentration of chloroauric acid solution in the electrolyte on the morphology of the gold nanostructures was studied.The results showed that the SERS activity of the gold nano-dendritic structure was higher than that of the gold nanoparticles.When the concentration of the chloroauric acid solution was 0.03 mol/L,SERS activity was the highest.Using Rhodamine 6G as the probe molecule,it was found that when the concentration was as low as 10^-7mol/L,clear and obvious Raman characteristic peaks can still be observed.At the same time,a large number of repeatability and aging verifications were performed on the substrate,which proved that the SERS substrate had good stability and reproducibility.Finally,the porous silicon-gold dendrite composite structure was used as the SERS substrate to detect low concentrations of Hg(?).After Hg(?)replaced Rhodamine 6G molecules on the surface of gold dendrites,the Raman signal intensity decreased,and its change was a function of the Hg(?)concentration.According to the test,it was found that the substrate had a good response to mercury ions with a linear concentration range of 1?50 ppb,and can be used as a SERS detection method for low-concentration mercury ions.Studies have proved that porous silicon-gold dendrites can be used as a high-performance SERS active substrate and have broad application prospects.This study not only conducted a systematic study on the design,preparation and SERS performance of porous silicon-gold dendritic composite nanostructures,but also carried out a numerical study on the SERS enhancement mechanism of composite nanostructures,and clarified its SERS enhancement mechanism.At the same time,a theoretical basis and design means was provided for the preparation of porous silicon-based composite substrate materials with high SERS performance.