1：Experimental Design and Method Selection:

A layer-by-layer (LbL) approach was used to synthesize Au@SiO2 nanoparticle multilayers on glass substrates and inside glass capillaries. UV-Vis spectroscopy and SEM were employed for characterization.

2：Sample Selection and Data Sources:

Glass substrates and capillaries were used; organic vapors like toluene and cyclohexanone were tested.

3：List of Experimental Equipment and Materials:

Equipment includes FESEM (Hitachi S-4100), UV-Vis spectrometer (Maya2000 Pro, Ocean Optics), mass flow controllers, solenoid valves, optical fiber (Ocean Optics), light source (DH2000, Ocean Optics), GC (Agilent 6890), capillary column (DB-5), six-port valve (Valco Instruments), sample loop (Supelco). Materials include HAuCl4, sodium citrate, TEOS, APTMS, organic solvents, Piranha solution, silver mirror coating reagents.

4：Experimental Procedures and Operational Workflow:

Clean glass with Piranha, modify with APTMS, bind Au nanoparticles, coat with SiO2 using TEOS, repeat for multilayers. For GC detector, synthesize multilayer inside capillary, coat with silver mirror, assemble with optical fiber and spectrometer. Test vapor responses and GC performance.

5：Data Analysis Methods:

Total Absorbance Difference (TAD) calculation for LSPR spectrum changes, calibration curves for VOC detection, LOD calculation based on 3σ.