A flexible ag/PDMS hemispherical array SERS for rapid "touch-and-wipe" sampling and quantitative screening of multi-class contaminants

This study developed a highly sensitive, reproducible, and flexible SERS sensing platform based on an ordered silver nanoparticle (Ag NPs)-coated polydimethylsiloxane (PDMS) hemispherical array. A dense and uniform Ag NPs film was fabricated via a Marangoni effect-driven interfacial self-assembly strategy and subsequently transferred onto a micro-replicated PDMS hemispherical array to create a hierarchical 3D plasmonic architecture. This design significantly increases the density of "hotspots" and the effective surface area compared to flat substrates, achieving a high analytical enhancement factor (AEF) of 2.89 × 105. The flexible nature of the Ag/PDMS substrate allows for efficient, direct "touch-and-wipe" sampling from irregular surfaces, such as fish skin, apple peels, and chili peppers. Furthermore, by coupling the substrate with a portable 1064 nm Raman spectrometer, fluorescence background from real-world samples was effectively suppressed, enabling reliable on-site quantification. The platform demonstrated excellent reproducibility with a relative standard deviation (RSD) of 8.52% and achieved low detection limits for crystal violet (CV), thiram, and rhodamine B (RhB) in the range of 10-9 M. Practical applications revealed robust linear correlations for contaminant detection on diverse food surfaces. These results highlight the immense potential of this sensor for rapid, non-destructive, and quantitative food safety monitoring in field environments.