Designing SnO₂ Nanostructure-Based Sensors with Tailored Selectivity toward Propanol and Ethanol Vapors

The application of metal oxide-based sensors for the detection of volatile organic compounds is restricted because of their high operating temperatures and poor gas sensing selectivity. Driven by this fact, we report the low operating temperature and high performance of C₃H₇OH and C₂H₅OH sensors. The sensors comprising SnO₂ hollow spheres, nanoparticles, nanorods, and fishbones with tunable morphologies were synthesized with a simple hydrothermal one-pot method. The SnO₂ hollow spheres demonstrated the highest sensing response (resistance ratio of 20) toward C₃H₇OH at low operating temperatures (75 °C) compared to other tested interference vapors and gases, such as C₃H₅O, C₂H₅OH, CO, NH₃, CH₄, and NO₂. This improved response can be associated with the higher surface area and intrinsic point defects. At a higher operating temperature of 150 °C, a response of 28 was witnessed for SnO₂ nanorods. A response of 59 was observed for SnO₂ nanoparticle-based sensor toward C₂H₅OH at 150 °C. This variation in the optimal temperature with respect to variations in the sensor morphology implies that the vapor selectivity and sensitivity are morphology-dependent. The relation between the intrinsic sensing performance and vapor selectivity originated from the nonstoichiometry of SnO₂, which resulted in excess oxygen vacancies (V_O) and higher surface areas. This characteristic played a vital role in the enhancement of the target gas absorptivity and the charge transfer capability of SnO₂ hollow sphere-based sensor.