Microwave-assisted synthesis of SnO₂ nanorods for oxygen gas sensing at room temperature.

High-quality single-crystalline SnO₂ nanorods were synthesized using a microwave-assisted solution method. The nanorods were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), ultraviolet-visible and Raman spectroscopy, Brunauer-Emmett-Teller (BET), and electrical resistance measurements. The XRD pattern indicated the formation of single-phase SnO₂ nanorods with rutile structure. FE-SEM and TEM images revealed tetragonal nanorods of about 450-500 nm in length and 60-80 nm in diameter. The nanorods showed a higher BET surface area of 288 m²/g, much higher than that of previously reported work. The Raman scattering spectra indicated a typical rutile phase of the SnO₂. The absorption spectrum showed an absorption peak centered at 340 nm, and the band-gap value was found to be 3.64 eV. The gas-sensing properties of the SnO₂ nanorods for oxygen gas with different concentrations were measured at room temperature. It was found that the value of resistance increased with the increase in oxygen gas concentration in the test chamber. The SnO₂ nanorods exhibited high sensitivity and rapid response-recovery characteristics to oxygen gas, and could detect oxygen concentration as low as 1, 3, 5, and 10 ppm.