Controllable self-assembled AuNRs array with dual signal amplification for SERS detection of 5-HMF in honey

5-Hydroxymethylfurfural (5-HMF) is a toxic compound formed during the improper processing or storage of honey, endangering human health. Thus, rapid and accurate detection of 5-HMF is essential. In this study, we fabricated uniform gold nanorod (AuNR) array surface-enhanced Raman spectroscopy (SERS) substrates with high-density plasmonic hot spots by optimizing the AuNR aspect ratio and employing a novel three-phase self-assembly technique, significantly enhancing detection sensitivity and reproducibility. The AuNR array (aspect ratio of 3.5) showed the strongest signals due to the close match between its 781 nm longitudinal LSPR wavelength and the 785 nm excitation laser wavelength, enabling efficient resonant coupling. Leveraging the dual-resonance of the AuNR arrays, tip-induced field focusing and nanogap-mediated plasmon coupling synergistically produced ultrahigh electromagnetic enhancement for SERS detection. Using AuNR array-3.5 as the SERS substrate, the signal intensity demonstrated a positive correlation with a concentration of 5-HMF in the range of 1-50 mg/L, with a limit of detection (LOD) as low as 0.093 mg/L. The substrate revealed excellent uniformity (relative standard deviation, RSD = 3.86%), reproducibility (inter-batch RSD = 2.51%), reusability (RSD = 13.2%) and stability (stored at 4 °C for 30 days). In spiked honey samples, this method achieved an LOD of 35.4 mg/kg, well below the international maximum residue limit (40 mg/kg), and recovery values ranging from 73.32% to 95.92%, confirming its high sensitivity and accuracy. This work provided a rapid, efficient approach for detection of 5-HMF in honey and highlights its application potential in SERS-based food safety monitoring technologies.