1：Experimental Design and Method Selection:

The study used chemical spray pyrolysis to deposit pure and Ti-doped CdO thin films on ITO substrates, chosen for its simplicity and cost-effectiveness. Theoretical models included XRD for crystal structure analysis, SEM/TEM for morphology, XPS for chemical composition, and electrochemical methods for sensing performance.

2：Sample Selection and Data Sources:

Films were deposited on ITO glass substrates (10 x 10 x 1 mm3). Precursor solutions were prepared using cadmium acetate dihydrate and titanium isopropoxide in ethanol and acetylacetone solvent.

3：3). Precursor solutions were prepared using cadmium acetate dihydrate and titanium isopropoxide in ethanol and acetylacetone solvent. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included a stylus profilometer, Philips X Pert PRO XRD, FEI Quanta FEG 200 SEM, PHILIPS CM 200 HRTEM, ESCA-3400 XPS, Shimadzu-UV 2450 spectrophotometer, photoluminescence spectrometer, and CHI-650D electrochemical analyzer. Materials included ITO substrates, chemicals from Merck, Alfa Aesar, and Sigma-Aldrich.

4：Experimental Procedures and Operational Workflow:

Precursor solutions were sprayed onto preheated substrates at 300°C with optimized parameters (distance 25 cm, angle 45°, spray time 3 s, interval 30 s, pressure 40 kg/cm2, flow rate 3 ml/min). Films were characterized structurally, morphologically, chemically, optically, and electrochemically.

5：Data Analysis Methods:

Data were analyzed using Scherer equation for crystallite size, Tauc plot for band gap, cyclic voltammetry, amperometry, and statistical methods for detection limit and sensitivity calculations.