Precursors for nanostructured SnO2 were synthesized via a microwave-assisted hydrothermal method under different conditions, using SnCI2.2H2 O, urea and citric acid as reactants. After calcination of the pre-cursors at 700 ℃ for 2 h, nanostructured SnO2 with different morphologies were obtained, and were then characterized using X-ray powder diffraction （XRD）, and field-emission scanning electron microscopy （FESEM）. The results show that synthesis temperature and time play an important role in the formation of the 3D hierarchical morphology of the nanostructured SnO2. Gas sensing experiments demonstrate that the synthesized SnO2 materials, especially those with a 3D network structure, exhibit superb sensitivity to alcohol vaoors at 240 ℃.
Liying ManJun ZhangJieqiang WangHongyan XuBingqiang Cao
Sn（OH）4 was prepared by the conventional solution precipitate method,followed by supercritical CO2 drying.The resultant Sn（OH）4 was divided into three aliquots and calcined at 400,600 and 800 °C,respectively,thus SnO2 nanoparticles with average crystallite sizes of 5,10 and 25 nm were obtained.Furthermore,three SnO2 thick film gas sensors（denoted as sensors S-400,S-600 and S-800） were fabricated from the above SnO2 nanoparticles.The adhesion of sensing materials on the surface of alumina tube is good.Compared to the sensors S-600 and S-800,sensor S-400 showed a much higher sensitivity to 1000 μL/L ethanol.On the other hand,sensor S-800 showed a much lower intrinsic resistance and improved selectivity to ethanol than sensors S-400 and S-600.X-Ray diffraction（XRD）,transmission electron microscopy（TEM） and selective area electron diffraction（SAED） measurements were used to characterize the SnO2 nanoparticles calcined at different temperatures.The differences in the gas sensing performance of these sensors were analyzed on the basis of scanning electron microscopy（SEM）.
