1：Experimental Design and Method Selection:

A hydrothermal method was used with a complex surfactant mixture of SDS and PEG400 to synthesize ZnO nanorods. The method was chosen for its cost-effectiveness and control over morphology.

2：Sample Selection and Data Sources:

Zinc acetate dihydrate was used as the Zn source, with SDS and PEG400 as surfactants. All chemicals were of analytic purity from Sinopharm Chemical Reagent Co., Ltd.

3：List of Experimental Equipment and Materials:

Equipment included a magnetic stirrer, ultrasonicator, Teflon-lined stainless-steel autoclave, vacuum drying oven, tubular furnace, X-ray diffractometer (PAN Analytical X'Pert Pro), FESEM (ZEISS Ultra Plus), TEM (JEM2100), XPS (Thermo Scientific Escalab 250Xi), and gas sensing test system (WS-30A). Materials included Zn(Ac)2·2H2O, NaOH, SDS, PEG400, deionized water, ethanol, Al2O3 tube, Au electrodes, Pt wires, Ni-Cr alloy wire.

4：Experimental Procedures and Operational Workflow:

Zinc acetate was dissolved in water, NaOH added dropwise, SDS and PEG400 added, mixture stirred and ultrasonicated, transferred to autoclave and heated at 160 °C for 15 h, precipitates washed and dried, annealed at 400 °C for 4 h. For gas sensor fabrication, ZNRs were mixed with ethanol to form a paste, coated on Al2O3 tube, aged at 350 °C for 24 h, and tested with WS-30A system.

5：Data Analysis Methods:

XRD for crystal structure, FESEM and TEM for morphology, XPS for surface composition, gas sensing data analyzed for response, response/recovery times, and selectivity using defined equations.