Enhanced NO2 and SO2 sensor response under ambient conditions by polyol synthesized Ni doped SnO2 nanoparticles

Undoped and Ni doped SnO2 nanoparticles were synthesized by low temperature polyol route and systematically investigated for gas sensing applications. XRD, SEM and TEM studies confirmed the tetragonal rutile phase and the nanocrystalline nature of SnO2 particles. Doping of Ni and the formation of various defects/oxygen vacancies in SnO2 were supported by XPS, PL and UV–Vis spectroscopic measurements. For gas sensing studies, sensors were fabricated by drop casting of the nanoparticles on gold inter-digitated electrodes and tested at room temperature (∼25°C). It was found that 2 at% Ni doping has improved the sensor response towards SO2 (∼6 for 10 ppm) and NO2 (∼850 for 3 ppm) significantly. Excellent sensor response and selectivity of Ni doped SnO2 for NO2 could be attributed to the formation of preferred type oxygen vacancies, favourble adsorption sites and the surface hydroxyl groups due to optimum Ni doping. Since the Ni doped SnO2 sensor exhibited opposite response signal towards SO2 (decrease in resistance) and NO2 (increase in resistance), the same sensor can be used for the selective, sensitive and reversible detection of both SO2 and NO2, especially operating at room temperature.