1：Experimental Design and Method Selection:

A one-step chemical reduction method was used to synthesize Fe–Ag nanoparticles, avoiding hazardous materials like hydrazine hydrate. The method involved reducing FeCl2 with NaBH4 to form Fe nanoparticles, then adding AgNO3 solutions of different concentrations to achieve varying Fe:Ag ratios.

2：Sample Selection and Data Sources:

Nanoparticles were synthesized with different AgNO3 concentrations (

3：1 M, 01 M, 05 M) to obtain Fe:

Ag atomic ratios of 69:31, 58:42, and 45:55, as confirmed by EDX analysis.

4：List of Experimental Equipment and Materials:

Equipment included X-ray diffractometer (XRD; PANalytical X’Pert PRO), Transmission Electron Microscope (TEM; Helios NanoLab, FEI), Energy Dispersive X-ray spectrometer (EDX; Helios NanoLab, FEI), spectrophotometer (Hitachi-U3410), and Photoluminescence system (PL; Fluorolog, Jobin-Yvon, Horiba). Materials included FeCl2 (Merck), NaBH4 (Merck), AgNO3, de-ionized water, acetone, and isopropyl alcohol.

5：Experimental Procedures and Operational Workflow:

Fe nanoparticles were formed by mixing FeCl2 and NaBH4 solutions; AgNO3 was added to create bimetallic nanoparticles. The mixture was stirred, filtered magnetically, washed, dried, and characterized. For TEM/EDX, nanoparticles were dispersed in isopropyl alcohol and drop-casted on Cu mesh grids. UV-Vis absorption was measured from 300–600 nm, and PL was measured with excitation at 250 nm.

6：Data Analysis Methods:

Structural analysis used XRD and TEM/SAED for crystallinity and morphology. Composition was analyzed via EDX. Optical properties were analyzed from UV-Vis spectra for LSPR peaks and PL spectra for luminescence intensity, with interpretations based on effective medium approaches and comparisons to literature.