Nitrogen Plasma-Driven Oxygen Vacancy Modulation in Tin Dioxide Nanosheets Enables Sub-Parts-per-Billion Nitrogen Dioxide Detection at Low Operating Temperature

Metal oxide semiconductor (MOS) materials have been widely used in gas sensing. However, they generally face challenges such as high operating temperatures and limited sensitivity/selectivity, which hinder their applications in areas like medical diagnosis based on human exhaled breath and ultralow concentration gas detection in harsh environments. Developing general strategies to enhance the sensing performance of MOS materials is both challenging and highly desired. Herein, we demonstrate nitrogen plasma-driven oxygen vacancy modulation in tin dioxide nanosheets (SnO₂ NSs) that enables sub-parts-per-billion-level nitrogen dioxide (NO₂) detection at low temperatures. SnO₂ NSs, oriented predominantly along the (110) crystal facet, are synthesized using graphene oxide templates and treated with nitrogen plasma, which can generate abundant oxygen vacancies. The oxygen vacancy-rich SnO₂ NSs exhibit exceptional NO₂ sensing performance, with a theoretical detection limit of 0.154 ppb and a response that is 3.4 times higher than that of the untreated SnO₂ NSs at 80 °C. Mechanism studies reveal that the improved sensitivity is attributed to the large surface area, favorable crystal orientation, and oxygen vacancies introduced by nitrogen plasma treatment. This work not only provides a promising strategy for modulating the oxygen vacancies in MOS materials, but also offers valuable insights for the development of high-performance MOS-based gas sensors.