Flexible electrospun microcone-array SERS swab for rapid on-site detection of saffron adulteration

Surface-enhanced Raman scattering (SERS) has attracted increasing attention in food authenticity testing due to its high sensitivity toward dyes and trace molecular contaminants. However, its practical application to filament-type herbal materials such as saffron remains challenging, largely because their irregular surfaces hinder efficient sampling and lead to poor hotspot uniformity. Here, we report a template-assisted electrospun fiber membrane with well-ordered microcone arrays (EFM-OMA) as a flexible 3D SERS platform for rapid detection of saffron adulteration. The well-ordered microcone architecture provides a highly repeatable nanoscale enhancement environment, enabling dense and uniform AgNPs-based hotspots across the entire substrate. This structure not only enhances electromagnetic coupling but also significantly improves molecular collection efficiency during swabbing of irregular solid samples. Benefiting from its high sensitivity and uniformity, the EFM-OMA SERS swab achieves an enhancement factor of 3.7 × 10¹¹, a detection limit down to 10^-14 M, and excellent signal reproducibility with an RSD of 7.86%. The stable full-spectrum fingerprints obtained from the swab can be reliably analyzed using a Random Forest classifier, enabling accurate identification of dye-adulterated saffron. This work demonstrates a scalable strategy that integrates a flexible 3D SERS substrate with machine-learning-assisted spectral analysis, offering an effective route for on-site, rapid authentication of solid herbal materials.