Mechanism of sensing NO in argon by nanocrystalline SnO2: electron paramagnetic resonance, Mِssbauer and electrical study

The mechanism of NO interaction with nanocrystalline (6–10 nm particle size) SnO2 powdered samples, obtained by sol–gel synthesis, was studied by electron paramagnetic resonance and Mössbauer spectroscopy. Resistance measurements on nanostructured (3 nm particle size) SnO2 thin films (80–160 nm), still obtained by sol–gel route, were coupled to spectral results. oscopic investigations demonstrated that the NO interaction involves electron injection to the oxide, formation of oxygen vacancies, and chemisorption of NO2− and NO3− anions. The amount of oxygen vacancies depends on the annealing atmosphere of SnO2. When it was previously annealed under inert (Ar) atmosphere, the NO interaction causes a great amount of oxygen defects as the lack of chemisorbed oxygen species forces NO to interact with lattice oxide anions; instead when annealed in air, NO also reacts with chemisorbed oxygen species giving NO2− and NO3− anions. ingly, the electrical response is higher in the case of predominant NO interaction with lattice oxide anions, because a great amount of NO electrons are transferred to SnO2.