<p>This study investigates the growth of tin dioxide (SnO₂) nanostructures for NO₂ gas sensing applications. SnO₂ nanoparticle seed layers were deposited upon glass substrates employing chemical spray pyrolysis, followed by the synthesis of various nanostructured films through the hydrothermal technique. The structural, electrical, optical, and sensing characteristics of the SnO₂ films were examined. The polycrystalline tetragonal SnO₂ phase was confirmed by X-Ray Diffraction (XRD) measurements. The Field Emission-Scanning Electron Microscope (FE-SEM) images revealed a transition in morphology as the pH increased from 3 to 11. At lower pH, the nanoparticles appeared spherical. With increasing pH, the morphology changed to cubic forms and finally to cauliflower-like aggregates. The optical energy gap values were found to be 3.13, 3.31, and 3.00&#xa0;eV, for pH 3, 9, and 11, respectively. Hall measurements confirmed the n-type conductivity for all films. Gas sensing tests were performed at different operating temperatures, and the sample prepared at pH 9 showed the highest NO₂ response at 150&#xa0;°C. These findings demonstrate that optimizing the pH and seed-assisted hydrothermal synthesis significantly enhances the structural behavior and the gas sensing performance of the SnO₂ films, making them promising candidates for low-cost NO₂ detection.</p>