Ag@SnO2 core–shell material for use in fast-response ethanol sensor at room operating temperature

A nano-composite core–shell Ag@SnO2 material was synthesized by chemical reduction and characterized by temperature-programmed reduction (TPR), UV–visible reflective spectroscopy, high-resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray spectroscopy (EDS). SnO2, Ag/SnO2 and Ag@SnO2 were used to sense ethanol (C2H5OH) in an ethanol gas detection system. The SnO2 material under 200 ppm ethanol gas exhibited a sensor response (S = Rair/Rethanol = (resistance of sensor signal of air)/(resistance of sensor signal of ethanol gas)), response time (t90) and recovery time (tR90) were 1.54, 54 s and 85 s, respectively. Ag@SnO2 materials had an improved sensor response of 2.24, with a shortened response time (t90) and recovery time (tR90) of 34 s and 68 s, respectively. The bond strength between ethanol gas and the Ag@SnO2 on which was adsorbed, determined by van der Waalʹs forces, and was calculated for a case in which more than 20 molecules were adsorbed. The mechanism of the sensing of ethanol gas, based on its adsorption, its reaction on the surface and its desorption is presented.