Controlled preparation and gas sensitive properties of two-dimensional and cubic structure ZnSnO₃

Two-dimensional (2D) ZnSnO₃ is a promising candidate for future gas sensors due to its high chemical response and excellent electronic properties. However, the preparation of 2D ZnSnO₃ nanosheets by utilizing soluble inorganic salts and nonorganic solvents remains a challenge. In this work, 2D ZnSnO₃ was synthesized via a facile graphene oxide (GO)-assisted co-precipitation method, in which inorganic salts in the aqueous phase replaced metal organic salts in a non-aqueous system. Meanwhile, a "dissolution and recrystallization" mechanism was proposed to explain the transformation from 3D nanocubes to 2D nanosheets. In comparison, the 2D ZnSnO₃ nanosheets showed a higher response to formaldehyde (HCHO) at low operating temperature (100 °C). The response (R_a/R_g) of the 2D ZnSnO₃ sensor to 10 ppm HCHO was as high as 57, which was approximately 5 times the response of the ZnSnO₃ nanocubes sensor. However, the ZnSnO₃ nanocubes sensor showed better gas sensing performance to ethanol at high temperature (200 °C). Different gas-sensitive properties were attributed to the different gas diffusion and adsorption processes caused by the morphology and nanostructure. Moreover, both sensors could detect either 0.1 ppm HCHO or ethanol at their optimum operating temperature. This work presents a relatively economical method to prepare 2D compound metal oxides, provides a novel "dissolution and recrystallization" mechanism for 2D multi-metal oxide preparation, and sheds light on the great potential of high-efficiency HCHO and/or ethanol gas sensors.