Scalable Fabrication of Highly Ordered Au/Ag Composite Nanoshell Array for Ultrasensitive SERS Detection of Trace Pesticides.

Surface-enhanced Raman scattering is highly promising for trace molecular detection but requires substrates with both ultrahigh sensitivity and macroscopic uniformity. Current bimetallic nanostructures struggle to achieve large-area structural reproducibility and high-density "hot spots" due to the lack of precise spatial control over nanoparticle arrangement and the random distribution of nanogaps, which severely limits their quantitative reliability in realistic applications. Here, we developed a simple and scalable method to fabricate a highly ordered Au/Ag composite nanoshell array via combining the gas-liquid interface self-assembly and ion sputtering. This prepared substrate is featured by abundant nanoscale openings, crevices, and interfacial junctions. The Au/Ag composite nanoshell array achieves an ultra-low limit of 10-11 M for the standard probe Rhodamine 6G. The highly ordered array also ensures advanced large-area signal reproducibility with a relative standard deviation of 6.1%. This work successfully balances the large-area uniformity and high sensitivity in SERS detection. It also provides a robust and reliable plasmonic platform for practical food safety analysis and environmental monitoring.