1：Experimental Design and Method Selection:

The study employs a two-step method: embedding gold nanoparticles in a polyvinyl alcohol (PVA) film on the substrate, followed by thermal annealing at high temperatures to deposit AuNPs via migration and coalescence. The rationale is to create clean AuNP surfaces by removing organic compounds through annealing.

2：Sample Selection and Data Sources:

Substrates used are bare glass and indium tin oxide (ITO) film coated glass strips (4.0 × 0.5 cm2). Gold colloid is synthesized by reducing HAuCl4 with sodium citrate, and PVA is used as the embedding matrix.

3：0 × 5 cm2). Gold colloid is synthesized by reducing HAuCl4 with sodium citrate, and PVA is used as the embedding matrix. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment includes a tubular furnace for annealing, FEI TECNAL 20 TEM, S-4700 SEM, Cary 60 UV-vis spectrometer, magnetic stirrer, three-necked flask, centrifuge, and bake oven. Materials include sodium citrate, HAuCl4, PVA, ITO glass, and purified water.

4：Experimental Procedures and Operational Workflow:

Clean substrates, prepare gold colloid, mix with PVA, drop-cast on substrate, dry at 130°C for 2 h, anneal in tubular furnace at 400-700°C for 0.5-10 h, cool to room temperature, and characterize using TEM, SEM, and UV-vis spectroscopy.

5：5-10 h, cool to room temperature, and characterize using TEM, SEM, and UV-vis spectroscopy. Data Analysis Methods:

5. Data Analysis Methods: Analyze UV-vis spectra for LSPR peak shifts and SEM images for nanoparticle size and morphology using size distribution measurements.