Nanofilms assembled from Au–Ag alloy hollow nanoparticles of different sizes as SERS substrates

Precious metal alloys can serve as surface-enhanced Raman scattering (SERS) substrates, significantly improving the sensitivity of Raman detection for trace molecules. Herein, we prepared nanomembrane substrates with different sizes of Au-Ag alloy hollow nanoparticles (HNPs) by a self-assembly method. The substrate exhibits uniformly distributed hot spots and excellent reproducibility when using the crystal violet (CV) solution as a Raman reporter, with a detection limit of approximately 10-9 M and an RSD of 6.61%. Additionally, it can detect thiram pesticides at concentrations as low as 0.01 ppb. Finite-difference time-domain (FDTD) simulations demonstrate that the SERS enhancement of the substrate results from the synergistic effect of the localized surface plasmon resonance (LSPR) effect of the Au-Ag HNPs and the abundant and uniformly distributed ‘hot spots’ within the nanofilm. These prove that our Au-Ag HNPs nanomembranes are promising for pesticide detection applications.