The 3D crystal morphologies of NiO gas sensor and constantly improved sensing properties to ethanol.

We successfully synthesized three kinds of NiO microspheres with solid, porous and hollow nanostructure via one-step hydrothermal method. The results indicated that the gas sensing performances of the porous sphere and hollow sphere are better than that of the solid sphere, which was attributed to the high specific surface area and the small size of Debye length. We find that the ethanol molecules can enter the interior of the NiO hollow sphere to have completed gas-sensing reactions because of enough response time, which lead to abundant effective gas diffusion and sufficient contact between with NiO, and it means more atoms can directly react with the gas to increase sensitivity. In this way, this article provides some suggestions and ideas for the development of gas sensor in the future. [ABSTRACT FROM AUTHOR]