1：Experimental Design and Method Selection:

The study involved synthesizing Si nanowires (SiNWs) via metal-assisted chemical etching (MACE), followed by Au sputtering and ZnO shell formation through thermal evaporation of Zn powders and oxidation. The design aimed to create p-Si/n-ZnO core-shell heterojunctions with Au nanoparticles to enhance H2S sensing.

2：Sample Selection and Data Sources:

Si pieces cut from wafers (2x2 cm2) were used as substrates. Gas sensing tests were performed with H2S, ethanol, acetone, and NO2 gases at concentrations ranging from 5 to 50 ppm.

3：List of Experimental Equipment and Materials:

Equipment included a turbo sputter coater (Emitech K575X) for Au deposition, a vertical furnace for ZnO deposition, scanning electron microscopy (FESEM, JSM-6700, JEOL), transmission electron microscopy (TEM, JEOL JEM-2010), energy dispersive X-ray spectrometer (EDS), mass flow controllers (MFCs), and a horizontal tube furnace for gas sensing tests. Materials included Si wafers, AgNO3, HF, H2O2, HNO3, Zn powders, Au, and Ti.

4：Experimental Procedures and Operational Workflow:

SiNWs were synthesized by cleaning Si pieces, Ag deposition, etching in HF/H2O2 solution, Ag removal with HNO3, detachment in ethanol, and spraying onto quartz substrates. Au was sputtered (3 nm thick), and ZnO was deposited by heating Zn powders at 500°C. Gas sensing involved depositing Au/Ti electrodes, controlling gas flow with MFCs, and measuring resistance changes at 300°C.

5：Data Analysis Methods:

Sensor response was calculated as Rg/Ra for oxidizing gases (e.g., NO2) and Ra/Rg for reducing gases (e.g., H2S). Response and recovery times were determined as time to reach 90% resistance change. Data were analyzed for sensitivity, selectivity, and stability.