Sensing behavior to ethanol of tin oxide nanoparticles prepared by microwave synthesis with different irradiation time

Crystalline tin oxide nanoparticles were successfully synthesized by microwave-assisted technique without any post annealing process. The morphology, microstructure and phase composition of the products obtained applying microwave irradiation for different time intervals were examined by XRD, FT-IR, SEM-EDX, TEM and HRTEM. Characterization results indicated that microwave irradiated products are composed of crystalline SnO2 nanoparticles which exhibit the cassiterite-type tetragonal crystal structure.The sensing properties of as-prepared SnO2 nanoparticles towards ethanol at low operating temperature were investigated. Such sensor devices exhibited good response to low concentrations of ethanol at temperature below 100 °C. An abnormal sensing behavior was registered, that is the sensor resistance increases in the presence of ethanol maintaining, at the same time, the usual n-type behavior with other reducing gases such as CO. In contrast, after annealing the SnO2 nanoparticles at 400 °C, the sensors show the expected regular behavior in all range of operating temperature investigated. A plausible mechanism, linked to a specific interaction between the surface of SnO2 and ethanol molecule through its hydroxyl group, was suggested in order to describe the unusual sensing behavior observed.