1：Experimental Design and Method Selection:

A simple interface self-assembly method was used to fabricate Au monolayer films at the hexane/water interface using ethanol as an inducer, without specific molecular cross-linkers. The films were calcined to remove surfactants and enhance SERS performance. SERS was employed for monitoring chemical reactions due to its high sensitivity and chemical specificity.

2：Sample Selection and Data Sources:

Gold and platinum colloids were prepared using HAuCl4·3H2O, HPtCl4·3H2O, CTAB, and NaBH4. p-Nitrophenol and rhodamine 6G (R6G) were used as model molecules. SERS spectra were collected using an HR 800 Raman spectroscope.

3：p-Nitrophenol and rhodamine 6G (R6G) were used as model molecules. SERS spectra were collected using an HR 800 Raman spectroscope. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Transmission electron microscope (TEM, Tecnai G2 F20), AFM system (Multimode V, Veeco, Bruker), HR 800 Raman spectroscope (J Y, France) with a 633 nm He-Ne laser, Mufe furnace for calcination. Reagents included sodium borohydride, CTAB, p-nitrophenol, n-hexane, ethanol, HAuCl4·3H2O, HPtCl4·3H2O.

4：2O. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Au colloid was prepared and assembled into a monolayer film at the hexane/water interface using ethanol. The film was transferred to a Si wafer, calcined at 400°C, and used as a SERS substrate. For monitoring, Pt colloid, p-nitrophenol, and NaBH4 were mixed, and SERS signals were collected per minute interval.

5：Data Analysis Methods:

SERS spectra were analyzed for vibrational features (e.g., nitryl C-N stretching at 1330 cm-1) to monitor reaction progress. Line-mapping mode with 1 μm increments was used for reproducibility assessment.