Fabrication of AAO-based 3D particle-in-cavity nanostructures for ultrasensitive SERS detection

Surface-enhanced Raman scattering (SERS) has emerged as a powerful tool for food safety analysis. We present a three-dimensional particle-in-cavity substrate that utilizes plasmonic cavity resonances for highly sensitive detection. Fabricated by a convenient transfer of AuNPs onto an anodic aluminum oxide (AAO) template, this design facilitates scalable production. The synergistic cavity-particle interplay yields a 4.24-fold SERS enhancement over a conventional flat Si substrate. The substrate demonstrated high sensitivity with a Rh6G enhancement factor of 1.77 × 10⁹, excellent uniformity showcasing relative standard deviations of 9.17% for Rh6G and 8.54% for crystal violet, and strong log-concentration linearity with correlation coefficients reaching 0.988 for Rh6G and 0.989 for Crystal Violet. It maintained 60% of its initial signal intensity after 30 days of storage and achieved an aspartame detection limit as low as 0.0078 g/L, demonstrating its excellent detection capability.