Lotus leaf inspired dual-functional SERS substrate: Ag NIs-decorated PDMS micropillar/wrinkle hierarchical structure for on-site detection of pesticides on fruit surface and in environmental water

The development of versatile surface-enhanced Raman scattering (SERS) platforms facilitates the rapid identification of contaminants in diverse application scenarios. Herein, a dual-functional SERS substrate comprising silver nanoislands-decorated micropillar/wrinkle hierarchical structure (Ag NIs@PWHS) on a polydimethylsiloxane (PDMS) film was fabricated through an amalgamation of fabrication techniques: soft lithography, surface wrinkling, and magnetron sputtering. The PDMS hierarchical architecture was constructed by replicating mastoid structures of lotus leaves through a two-step molding process, followed by the formation of periodic wrinkles via oxygen plasma treatment. This hierarchical design integrating micropillars and wrinkles not only provided a multiscale surface architecture conducive to the formation of three-dimensional (3D) hot spots, but also conferred hydrophobicity and bending insensitivity on the SERS substrate. The optimal Ag NIs@PWHS substrate had an analytical enhancement factor of 1.99 × 10 6 , outstanding signal uniformity (relative standard deviation, RSD = 2.98 %) and reproducibility (RSD = 4.54 %), and robust mechanical stability. Furthermore, the Ag NIs@PWHS substrate enabled the rapid detection of thiram on pear surface and malachite green in lake water, with a detection sensitivity of 10 −7 M for both pesticides. Thus, the developed Ag NIs@PWHS SERS substrate holds significant potential for utilization in realms of food safety assessments and water pollution surveillance.