Hierarchically enrichment-enhanced ultra-sensitive SERS detection via bioinspired printing patterned heterogeneous nanoparticles

Surface-enhanced Raman scattering (SERS) holds transformative potential for molecular detection in food safety, yet its effectiveness in complex matrices is hindered by limited enrichment efficiency and sensitivity. Herein, we propose a cactus-inspired hierarchical enrichment platform that synergistically integrates nanoscale electromagnetic focusing with microscale fluidic manipulation to overcome these challenges. Above all, heterogeneous AgNPs@ZIF-8 nanoparticles with ultrahigh surface areas are engineered to concentrate target molecules into electromagnetic hotspots, achieving a about 3-fold SERS enhancement over conventional AgNPs and enabling quantitative melamine detection from 10⁻³ to 10⁻⁸ M (R² = 0.995). Besides, a bionic nanofiber film featuring programmable hydrophilic-hydrophobic patterns is developed to directionally confine analytes into micron regions via capillary-driven flow, achieving local concentrations with enhancement factor up to 4.97 × 10⁷. Our platform, employing a dual-scale strategy, achieves a record-low detection limit of 10⁻¹⁰ M for melamine in milk (RSD = 7.22 %), surpassing previously reported MOF-based SERS sensors. The hierarchical enrichment mechanism relies on nanoconfinement within ZIF-8 and a bionic patterned surface, enabling localized plasmonic enhancement and fluidic-driven molecular trapping for ultra-sensitive detection, with direct implications for food safety and environmental monitoring.