1：Experimental Design and Method Selection:

The method combines solution combustion synthesis and ultrasonic spray pyrolysis (UNSPACM) to deposit SnO2 nanoparticles decorated RGO sheets in a single step, exploiting exothermicity for better exfoliation and deposition.

2：Sample Selection and Data Sources:

Graphite oxide (GO) was synthesized using Hummer's method, dispersed in water (1 mg/ml), and mixed with a combustion mixture of tin nitrate and urea in aqueous medium at concentrations of

3：5, 0, and 0 mM. List of Experimental Equipment and Materials:

Equipment includes an ultrasonic spray pyrolysis setup with a carrier gas (N2) flow system, deposition at 600°C, XRD (PANanalytical X'Pert PRO with CuKα radiation), Raman spectroscopy (Jobin-yvon LabRam HR system with 530 nm laser), TEM (JEOL2100F at 200 kV), AFM (APE Research AFM A100 in non-contact mode), and an in-house built gas sensor setup. Materials include graphite oxide, tin oxalate (Aldrich, USA), conc. HNO3, urea, and water.

4：Experimental Procedures and Operational Workflow:

GO was sonicated for 10 minutes, mixed with combustion mixture solutions, and sprayed onto substrates at 600°C with N2 flow. Films were characterized without further heat treatment. Gas sensing was performed at room temperature for NO2 concentrations, with sensitivity calculated using (Ra - Rg)/Ra *

5：Data Analysis Methods:

1 XRD for crystallite size (Scherrer formula), Raman for D and G band ratios, TEM for particle size and distribution, AFM for roughness, and empirical relations for gas sensitivity analysis (S = A * C^β).