Fabrication of plasmonic Au-Ag alloy nanostars for ultrasensitive SERS detection

In this paper, Au-Ag alloy nanostar (Au-Ag NSt) substrates were prepared by liquid-liquid three-phase self-assembly method, and the influence of preparation conditions on their Raman activity of the substrate was explored. By adjusting the gold-silver ratios of alloy seeds and the concentration of AgNO₃ in the growth solution, it was found that the LSPR peak can be adjusted. Under the conditions of Au₁-Ag₃ nanoparticles as seeds and 200 μL AgNO₃ solution (2 mM) as epitaxial growth solution, the prepared Au₁-Ag₃ NSt substrate exhibits excellent SERS activity. The substrate can detect R6G and CV probe molecules with detection limits as low as 10^-11 M and 10^-10 M, respectively. Experiments have confirmed that the substrate has the characteristics of high sensitivity, good uniformity and strong stability. In addition, the substrate can detect APM molecules far below the safety standard, which further proves that the structure has excellent practical application potential as a SERS substrate.