Synthesis of SnO2 nanoparticles for gas sensing applications

SnO₂ nanoparticles were synthesized using a hydrothermal method in the presence of the surfactant hydrazine at 100°C for 12 h. X-ray diffraction, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (DRS) were employed to characterize the product. The X-ray diffraction (XRD) pattern of the as-prepared sample is indexed to the tetragonal structure of SnO₂ and the particle size is 22.4 nm, which is further confirmed by TEM. Analysis of the DRS spectrum showed the band gap of the synthesized SnO₂ to be 3.6 eV. The anionic surfactant hydrazine plays a key role in the formation of the SnO₂ nanostructures. A probable reaction for the formation of SnO₂ nanoparticles is proposed. Gas-sensing properties of the sensor element were tested to various gases, as a function of operating temperature and concentrations of the test gases. The nanocrystalline SnO₂ exhibited high response towards H₂S gas at an operating temperature 150°C. The selectivity of the sensor elements for H₂S against different reducing gases was studied. The results on response and recovery time were also discussed.