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

Surface-enhanced Raman scattering (SERS) has emerged as a powerful analytical tool for ultrasensitive trace molecule detection. Herein, we report the fabrication of uniform nanofilm substrates composed of Au–Ag alloy hollow nanoparticles (HNPs) with tunable sizes, demonstrating exceptional performance as SERS platforms. Using crystal violet (CV) as a Raman probe, the substrates exhibit densely and uniformly distributed “hot spots” across the nanofilm surface, enabling a detection limit as low as 10[Formula: see text] M for CV with excellent signal reproducibility (relative standard deviation, RSD [Formula: see text] 6.61%). Notably, the substrates achieve quantitative detection of thiram pesticides at ultratrace concentrations (0.01 ppb). Finite-difference time-domain (FDTD) simulations elucidate that the observed SERS enhancement originates from the synergistic contribution of two factors: (1) the localized surface plasmon resonance (LSPR) effects mediated by the Au–Ag HNPs and (2) the formation of abundant, spatially homogeneous “hot spots” within the nanofilm architecture. This study highlights the potential of size-engineered Au–Ag HNP nanofilms as robust, and high-performance SERS substrates for environmental and analytical applications.