In this study, we prepared SnO2 containing various types of defects by changing the calcination atmosphere. Positron annihilation spectroscopy and electron-spin resonance show that oxygen vacancies (VO ••) are the predominant species after calcination in air, while triple VSn ⁗VO ••VSn ⁗ vacancy associates are predominant after calcination in helium. The sensing performance indicates that SnO2 nanoparticles calcined in air, helium, and oxygen exhibit excellent sensing performance for ethanol, formaldehyde, and acetone gases, respectively. On the basis of in situ IR spectroscopy, the sensitivity of SnO2 improves by reducing the objective gas to CO2. The relationship between the sensing selectivity and defect type was investigated. According to the results, the sensing mechanisms are discussed in terms of the selective effects of different defects based on combining band theory. The present study paves the way for the development of high-selectivity sensors.

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