High-performance broad-spectrum response flexible SERS sensor based on a hybrid gold nanostars-nanoparticles system for detection of pesticide residues

The rapid and sensitive detection of trace contaminants in food, particularly pesticide residues and migrating packaging additives, remains a critical challenge in food safety monitoring. This has prompted the development of an innovative flexible surface-enhanced Raman scattering (SERS) substrate that overcomes conventional limitations, such as poor enhancement performance, insufficient stability, and narrow spectral response ranges. To address these challenges, this work proposes the strategic assembly of gold nanostars (AuNSs) and gold nanoparticles (AuNPs) on expanded graphite (EG)-modified filter paper to engineer a sandwich-structured SERS-active platform with exceptional broad-spectrum response capabilities, achieving optimal plasmonic coupling. At a 4:1 AuNSs/AuNPs ratio, the substrate generates high-density ‘hot spots’ with a remarkable enhancement factor (4.7 × 10 6 for R6G) and detection limits reaching 10 −9  M, coupled with outstanding thermal stability (20–100 °C) and long-term performance (30 days), while demonstrating practical detection of thiram residues (0.24 ppm, 20 × below US safety limits) and DMSO (1 % v/v), thereby providing fundamental insights into hybrid plasmonic nanostructures while delivering a field-deployable solution for comprehensive food safety monitoring from farm to table.