The growth behavior of brain-like SnO microspheres under a solvothermal reaction with tetrahydrofuran as a solvent and their gas sensitivity.

In this paper, the growth behavior of brain-like SnO microspheres synthesized by a tetrahydrofuran (THF) solvothermal method was studied. Unlike water or ethanol as the solvent, THF is a medium polar and aprotic solvent. Compared with other common polar solvents, the THF has no strong irregular effects on the growth process of SnO. In addition, the viscosity of THF also helps the SnO to form a regular microstructure. The growth behavior of the brain-like SnO microspheres is controlled by changing the synthesis temperature of the reaction. The SEM and TEM results reveal that the SnO forms particles first (125 °C/3 h), and then these nanoparticles connect to each other forming nanowires and microspheres (diameter ≈ 1-2 μm) at 135 °C for 3 h; finally the microspheres further aggregate to form double or multi-sphere structures at 180 °C for 3 h. In this paper, the brain-like SnO microspheres obtained at 125 °C for 3 h were selected as sensitive materials to test their gas sensing performance at different operating temperature (50 °C and 350 °C). The HS was tested at 50 °C which is the lowest operating temperature for the sensor. The combustible gas (H/CH/CO) was measured at 350 °C which is the highest temperature for the sensor. They all have extremely high sensitivity, but only HS has excellent selectivity.