Construction of flexible, transparent and mechanically robust SERS-active substrate with an efficient spin coating method for rapid in-situ target molecules detection

Flexible, transparent and mechanically robust surface enhanced Raman scattering (SERS)-active substrates is currently the most attractive research focus in the field of Raman detection, and also a powerful analysis and identification technique in the biological research. Herein, we introduced a low-cost and large-scale method to fabricate flexible and transparent AgNPs/WPU plasmonic metafilm with monolayer-island phase nanostructures based on silver nanoparticles (AgNPs) and waterborne polyurethane emulsion (WPU) film. The obtained AgNPs/WPU plasmonic metafilm demonstrated excellent SERS sensitivity, signal uniformity and reproducibility, and the SERS substrates could still maintain excellent stability even after being bent or stretched over 100 cycles. The detection concentration was as low as 10^–9 M with 4-Mercaptobenzoic acid (4-MBA) as probe molecule, and the enhancement factor was high to 2.2 × 10⁷. More importantly, the flexibility and adhesivity of AgNPs/WPU plasmonic metafilm could be directly conformal coverage on the apple surface for in situ detection of thiram residue, and the detection limit was as low as 9.0165 ng cm⁻². This versatile AgNPs/WPU plasmonic metalfilm would be a promising SERS substrate for the detection of pesticide residue in chemical and biological applications. (paper)