Synthesis and enhanced ethanol sensing characteristics ofα-Fe2O3/SnO2 core–shell nanorods

Abstract

α-Fe2O3/SnO2 core–shell nanorods are synthesized via a three-step process. X-ray diffraction (XRD),scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysesreveal that their diameters and lengths are respectively in the ranges 35–120 nm and0.35–1.2 µm, and the thickness of the shell composed of 3.5 nmSnO2 nanoparticles is about 10 nm. The core–shell nanostructures exhibit adramatic improvement in ethanol sensing characteristics compared to pureα-Fe2O3 nanorods. The sensor response is up to 19.6 under 10 ppm ethanol exposure at220 °C. Both the response time and the recovery time of the core–shell structures are less than 30 s. Basedon the space–charge layer model and semiconductor heterojunction theory, the small thickness of theSnO2 shell and the formation of heterojunctions contribute to the enhanced ethanolsensing characteristics. Our results demonstrate that one-dimensional metal oxidecore–shell nanostructures whose shell thickness is smaller than the Debye length arevery promising materials for fabricating gas sensors with good performances.