1：Experimental Design and Method Selection:

The method involves laser remelting of Al-Si cast alloy to create a dendritic microstructure, followed by dealloying to remove Al and form a 3D porous Si substrate, and then sputter-coating with Au film to create the SERS platform. The rationale is to leverage laser-induced rapid solidification and dealloying for hierarchical pore structure formation, enhancing SERS activity through electromagnetic field enhancement.

2：Sample Selection and Data Sources:

An Al-20Si (20 wt.% Si) cast alloy plate (10 cm×5 cm×1 cm) was used as the precursor. R6G (Rhodamine 6G) solutions at concentrations from 10^-3 M to 10^-15 M were used as analytes for SERS testing.

3：List of Experimental Equipment and Materials:

Equipment includes a continuous fiber laser (IPG, YLS-6000, wavelength 1064 nm, beam diameter 6 mm), vacuum magnetron sputter-coater (QUORUM, Q150T), optical microscopy (OLYMPUS GX51), scanning electron microscopy (HITACHI S-3400N), transmission electron microscopy (JEM-2100F), atomic force microscopy (BRUKER MultiMode8), X-ray diffractometer (BRUKER D8), and laser micro-Raman spectrometer (Renishaw, 785 nm excitation). Materials include Al-20Si alloy, NaOH solution (75%), HCl solution (3M), argon gas, and R6G.

4：6G. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The Al-20Si plate was cleaned with NaOH, then laser-remelted with specific parameters (power 5000 W, velocity 15 mm/s, argon protection). The treated layer was cut and dealloyed in HCl to form porous Si. Au was sputtered onto the porous Si with varying times (60 s, 300 s, 600 s, 900 s). SERS measurements were performed by dropping R6G solution on the sample, drying, and collecting spectra.

5：Data Analysis Methods:

SERS spectra were analyzed for intensity and peak identification. Enhancement factor (AEF) was calculated using a reference spectrum from a flat glass surface. Relative standard deviation (RSD) was computed from multiple measurements. Electromagnetic field simulations were performed using CST Microwave Studio.