Flexible, Scalable SERS Substrate with High Sensitivity and Stability for On-Site Detection and Wearable Applications

A key challenge in the commercialization of surface-enhanced Raman scattering (SERS) technology is the scalable and controllable preparation of substrates that simultaneously achieve high sensitivity, uniform signal distribution, excellent reproducibility, and long-term stability. In this study, we report a flexible SERS substrate based on a porous, high-surface-energy nanofilm, designed to serve as a spatially confined template for the uniform growth of silver nanoparticles (AgNPs). This substrate exhibits outstanding SERS performance with an enhancement factor (EF) of 2.05 × 10¹⁰ and a detection limit (DL) as low as 1.74 × 10^-15 M for rhodamine 6G (R6G). The preparation process is mild, highly reproducible (RSD = 8.53% over 60 consecutive batches), and scalable to 25 cm² areas. Moreover, the substrate maintains its SERS activity for over three months within a vacuum bag at room temperature. Owing to its excellent adhesion and good flexibility, the substrate can adhere effectively to complex surfaces. The substrate was successfully applied to sensitive in situ detection of trace thiram residues on grape surfaces, achieving a detection limit (DL) of 8.51 × 10^-10 g cm^-2. Additionally, a wearable sensor was developed based on the substrate and used for the noninvasive monitoring of uric acid levels in human sweat, with a DL of 2.95 × 10^-7 M. This work provides a practical strategy for constructing high-performance, scalable, and flexible SERS substrates, advancing their potential for real-time, on-site analysis.