Semi-Embedded Liquid Metal Nanoparticles on Co-Electrospun Nanofibers for Scalable and High-Sensitivity Flexible Surface-Enhanced Raman Scattering Platform

Flexible surface-enhanced Raman scattering (SERS) substrates are essential for conformal on-site molecular detection, yet typically face a trade-off between sensitivity, uniformity, and mechanical robustness. In this work, we report a high-performance flexible SERS featuring liquid metal nanoparticles spatially confined within electrospun polyimide nanofibers. Via co-electrospinning, we engineered a unique "semi-embedded" structure where liquid metal nanoparticles are partially exposed on fiber surfaces. The optimized substrate achieves an ultralow detection limit (LOD) of 10-8 M for Rhodamine 6G with outstanding signal uniformity and excellent mechanical durability (72.5% signal retention after 500 bending cycles), compared to existing flexible platforms. Furthermore, the platform enables sensitive and differentiated SERS detection of thiol-containing molecules, with preferential trace detection of 4-aminothiophenol (LOD 10-9 M). Its practical utility is further demonstrated by the simultaneous monitoring of mixed acetamiprid and thiram residues in apple juice. Finite-element simulations suggest that the superior SERS enhancement under near‑infrared excitation is largely consistent with synergistic electromagnetic coupling between the sputtered Au nanoparticles and the highly conductive liquid metal cores, with possible additional chemical enhancement from the oxide-rich surface. This study presents a cost-effective and scalable strategy for fabricating high-performance SERS substrates while offering critical insights into the synergistic coupling between liquid metals and conventional plasmonic materials.