Nanostructured SnO2 thin films for NO2 gas sensing applications

We report the synthesis of nanostructured SnO₂ by a simple inexpensive sol–gel spin coating method using m-cresol as a solvent. This method facilitates rapid synthesis at comparatively lower temperature enabling formation of nanostructures suitable for gas-sensing applications. Various physicochemical techniques have been used for the characterization of SnO₂ thin films. X-ray diffraction analysis confirmed the single-phase formation of tetragonal SnO₂ having crystallite size 5–10 nm. SnO₂ showed highest response (19%) with 77.90% stability toward 100 ppm nitrogen dioxide (NO₂) at 200 °C. The response time of 7 s and recovery time of 20 min were also observed with the same operating parameters. The probable mechanism is proposed to explain the selective response toward nitrogen dioxide. Impedance spectroscopy studies showed that the response to nitrogen dioxide is mainly contributed by grain boundaries. The reproducibility and stability study of SnO₂ sensor confirmed its candidature for detection of NO₂ gas at low concentration (10–100 ppm) and lower operating temperature.