Plasmonic array at liquid-liquid interface for trace microplastics detection

Microplastics (MPs) pollution has become a focal point of global concern, as the widespread distribution of MPs in the environment poses a potential threat to ecosystems and human health. Despite surface-enhanced Raman scattering (SERS) being one of the most promising detection techniques, the “coffee ring effect” of MPs and their unique size scale make effective contact with SERS substrates challenging. Here, we propose a novel strategy for MPs detection by constructing a plasmonic metasurface at the liquid-liquid interface (LLI). The fluidic properties of LLI provide more flexibility for the uniform dispersion of MPs and the assembly of plasmonic arrays. MPs are captured and assembled on an atomic-level metasurface in a core-shell structure (AuNPs@MPs), providing abundant “hot spots” and additional volume-enhanced Raman effects. This results in enhanced electromagnetic field around MPs and increased enhancement factors, demonstrating high SERS sensitivity and uniformity. This sensing platform provides a new approach for trace detection of MPs and has been validated in practical matrix.