Mesoporous polycrystalline SnO2 framework synthesized by direct soft templating method for highly selective detection of NO2

SnO2 is one of the most studied oxide materials for gas sensing applications. Investigations have shown that SnO2 is sensitive to a wide range of gaseous compounds. However, its lack of selectivity remains an issue. Here, a mesoporous polycrystalline SnO2 framework was successfully synthesized using a soft templating method at ambient temperature and pressure. The prepared materials were characterized using x-ray diffraction analysis, high-resolution transmission electron microscopy, energy-dispersive x-ray spectroscopy, N-2 sorption tests, and x-ray photoelectron spectroscopy. Gas sensing analyses were performed on two batches of the material calcined at 400 degrees C and 500 degrees C. The resultant materials were highly conductive at relatively low operating temperatures. The thermal annealing and operating temperatures of the materials had significant effects on their gas sensing response and selectivity. The structure calcined at 400 degrees C showed a very selective response of 407 to 1 ppm NO2. The superior sensing performance of the obtained mesoporous SnO2 framework is attributed to its small crystal size of 4-5 nm-less than double the thickness of the critical electron depletion layer-as well as its high surface area of 89 m(2) g(-1) and high pore volume of 0.12 cm(3) g(-1).