Hydrothermal Synthesis of SnO₂ Nanoparticles and Their Gas-Sensing of Alcohol

Abstract

A hydrothermal method was used to synthesize nanocrystalline SnO2 particles with an average particle size of 3.0 ± 0.5 nm. Thermally treated SnO2 with an average diameter of 3.3 ± 0.6 nm was obtained by the annealing of the as-synthesized SnO2, which was treated at 300 °C for 1 h under 10% H2/Ar. An atomic ratio of 2.3/1 (O/Sn) was observed for the thermally treated SnO2 compared to 1.2/1 for the as-synthesized one. However, a smaller surface area of 92 m2/g was measured for the thermally treated SnO2 as compared with 130 m2/g for the as-synthesized SnO2. Due to the occupation of the chloride ions in the oxygen sites of the as-synthesized SnO2, the thermally treated SnO2 displayed better sensing performance for ethanol when compared with as-synthesized SnO2. The sensing performance of the as-synthesized SnO2 sensor can be greatly improved by simply heating it at 350 °C for 5 min to partly remove Cl- from SnO2 nanoparticles. The thermally treated SnO2 exhibited good sensitivity to alcohol, i.e., methanol, ethanol, and propanol. The concentration detection limit can be as low as 1.7 ppm. Furthermore, the increased sensor signal was found to depend on the carbon chain number of the alcohol.