1：Experimental Design and Method Selection:

The study involved the fabrication of Au@AgNAs using spherical Au nanocrystals as seeds and ascorbic acid as the reductant. The thickness of the Ag shell was tuned by varying the amount of AgNO3 precursor.

2：Sample Selection and Data Sources:

Au seeds with an average diameter of about 32 nm were prepared. The core-shell Au@Ag nanoparticles aggregates with several shell thicknesses were synthesized by a seed-mediated growth process.

3：List of Experimental Equipment and Materials:

Equipment included a UV-1800 spectrophotometer, transmission electron microscope (JEOL JEM-1400 Plus), high-resolution transmission electron microscope (JEOL JEM-2100F), and a laser confocal Raman microscope system (LabRAM HR). Materials included chloroauric acid hydrate, silver nitrate, trisodium citrate, ascorbic acid, Rhodamine 6G (R6G), and thiram pesticide.

4：Experimental Procedures and Operational Workflow:

The synthesis involved the reduction of AuCl3·HCl·4H2O using trisodium citrate to prepare Au seeds, followed by the deposition of Ag shell onto Au seeds using ascorbic acid and AgNO3. The SERS performance was evaluated using R6G as the probe molecule.

5：The SERS performance was evaluated using R6G as the probe molecule. Data Analysis Methods:

5. Data Analysis Methods: UV-visible spectra, TEM images, HRTEM measurements, HAADF-STEM analysis, EDS elemental mappings, and XRD patterns were used for characterization. SERS spectra were acquired to evaluate the performance of the Au@AgNAs substrate.