Methane gas sensing at relatively low operating temperature by hydrothermally prepared SnO₂ nanorods

Tin oxide (SnO₂) nanorods were prepared by surfactant-free hydrothermal method and their methane gas sensing characteristics were studied. These SnO₂ nanorods were characterized by XRD, SEM, TEM, EDS, EELS, UV–Visible, and Raman spectroscopies. The SnO₂ nanorods were single crystalline possessing tetragonal rutile structure. Average diameter of the nanorods was in the range from 8 to 48 nm with an average length of 174 nm. The diameter of the nanorod was found to increase with the increase of reaction time. The E_g and A_1g Raman modes showed a significant blue and red shift, respectively, and this was due to the contribution from the phonons with q ≠ 0 in the first Brillouin zone. Gas sensing measurements against methane gas showed a good sensitivity at an operating temperature of 100 °C, and the maximum gas sensitivity was observed at 175 °C. Our present experiments clearly demonstrate the sensitivity of methane up to 300 ppm at 100 °C, which is a lower operating temperature compared to the previously reported values. Hydrogen sensor was also fabricated with the same SnO₂ nanorods and its performance was compared with the methane gas sensor. These rods show better sensitivity toward methane gas than hydrogen gas.