p-N heterostructural sensor with SnO-SnO2 for fast NO2 sensing response properties at room temperature

The p-n heterostructures materials are currently used in photoluminescence, electro-chromic devices, photocatalysts and gas sensors due to increasement of the material defect sites at the interface. In this report, we successfully obtain the SnO-SnO2p-N (Egp < Egn) heterostructures by a facile hydrothermal strategy and annealing condition (500 °C). With the as synthesized samples present a morphology of nanosheet n-type SnO2 crystals dispersed on the edge of similar square p-type SnO crystals. This p-N heterostructural sensor exhibits excellent performances for NO2 sensing at room temperature in terms of fast response time, relative sensing selectivity, high sensitivity, and low LOD (the limit of detection) (0.1 ppm) by a stable and repeatable response pattern. The superior sensing properties can be attributed to three aspects that the heterojunction valence band offsets (ΔEV = 3.31 eV) is narrow, unique structure, and the intrinsic 'O' vacancies creating defect states close to the conduction band minimum. Further, the plausible formation growth and gas sensing mechanism of the novel SnO-SnO2p-N heterostructures are discussed, providing a considerable margin for employing them in gas sensors.