Silicon dioxide layer thickness-dependent Au nanocube @mSiO 2 @Ag with surface enhanced Raman scattering for trace detection of harmful substances

Au_nanocube@mSiO₂@Ag nanocomposites were synthesized by layer-by-layer assembly with an Au nanocube core, an Ag shell, and mesoporous silica as a spacer. The thickness of the mesoporous silica layer was controlled simply by changing the amount of silica precursor. The SERS activity of the nanocomposites varied with the thickness of the SiO₂ spacer layer, and the strongest SERS effect was observed when the optimized silica layer thickness was about 6 nm. The sensitivity of the synthesized nanocomposites was tested using typical representatives of organic dyes and pesticides (rhodamine 6G, crystal violet, and thiram) as probes, which have very low detection limits of 10^-12, 10^-11 and 10^-9 M, respectively, and good stability was observed. The SERS performance of Au_nanocube@mSiO₂@Ag changed with the change of the thickness of SiO₂, and Au_nanocube@mSiO₂@Ag with appropriate SiO₂ thickness showed excellent SERS performance. When the thickness of the SiO₂ layer is 6.0 nm, the SERS signal is strongest. It has the advantages of a fast response speed, simple operation, low detection limit and good pollutant detection ability.