Defect-rich ultrathin Sn2O3 nanosheets with dominant polar (100) facets for efficient gas and humidity sensor applications

Defect-rich ultrathin heterovalent tin oxide (Sn2O3) nanosheets with dominant polar (100) facets were synthesized via a facile hydrothermal method for the first time. The structure, morphology, chemical state, bandgap, defects, and specific surface area of these Sn2O3 nanosheets were characterized by XRD, FE-SEM, TEM, XPS, UV–Vis, PL, N2-adsorption, respectively. Taking inspiration from the morphology, defects, and exposed facets that facilitate adsorption-interaction of molecules on the surface, gas and humidity sensors were fabricated based on Sn2O3 nanosheets. The gas sensor response to 200 ppm ethanol at 200 °C is as high as 70.1, and response and recovery times are only 6 s and 3 s, respectively. At room temperature, the humidity sensor exhibits a response up to 2.76 × 103 with a small humidity hysteresis of 1.95%, and the response and recovery times are divided into 27 s and 124 s, respectively. Additionally, both gas and humidity sensors demonstrate excellent repeatability and stability. Finally, gas and humidity sensing mechanisms of the Sn2O3 sensor have been discussed. This work provides a practical candidate for gas and humidity sensors and further develops a new promising application for heterovalent metal oxides in electrical sensory devices.