Abstract <p>A method for producing nanocrystalline SnO₂ by direct chemical precipitation from a solution containing tin(II) chloride using hydrogen peroxide to oxidize the intermediate compound was studied. The effect of annealing at 300 and 500°C on the chemical composition and crystal structure of the synthesized powders was analyzed. It was found that, at a H₂O₂ concentration of 6 mol/L in the reaction system, a solid phase with a tetragonal crystal lattice typical of SnO₂ is formed. According to X-ray diffraction data, the size of the coherent scattering region increases with increasing temperature from 2.3 ± 0.2 (50°C) to 3.3 ± 0.3 (300°C) and 7.9 ± 0.3 nm (500°C). According to transmission electron microscopy, individual oxide nanoparticles are mainly single crystals, the average particle size after drying at 50°C is 1.9 ± 0.5 nm, and heat treatment at 500°C leads to its increase to 9.0 ± 1.8 nm. Scanning electron microscopy indicates the formation of agglomerates ranging in size from 28 ± 7 nm (50°C) to 32 ± 5 nm (500°C), which is caused by sintering of particles during high-temperature heat treatment. Using Kelvin probe force microscopy, the work function of electrons from the surface of the materials was estimated and it was determined that heat treatment leads to a decrease in this value from 4.9 eV (for the sample dried at 50°C) to 4.5 eV (500°C), which correlates with an increase in the electrical conductivity of the materials. The powder annealed at 500°C was used to form a film using microextrusion printing to study the chemosensory properties of the coating. The maximum response (2.0–29.7) was recorded for 100 ppm ethanol, with a maximum at 275°C. A significant sensory response was also observed for C₃H₆O (11.1 at 300°C), CO (7.1 at 275°C), and H₂ (8.9 at 250°C).</p>