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 degrees 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 degrees 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. (C) 2013 Elsevier B. V. All rights reserved.