Highly sensitive and selective Gd2O3-doped SnO2 ethanol sensors synthesized by a high temperature and pressure solvothermal method in a microreactor

Gd2O3-doped SnO2 nanoparticles as highly sensitive and selective ethanol sensor materials with uniform size distributions were synthesized in ethylene glycol at 250 degrees C and 20 bar in a continuous tubular microreactor. The samples were characterized by DLS, XRD, SEM, EDX, TEM, FTIR, and BET surface area measurement techniques. As 5 wt% Gd(2)O(3)is added to SnO2, the average particle and crystallite sizes of the samples decrease from 22 and 11.9 nm to 10 and 3.8 nm, respectively. The responses of Gd2O3-doped SnO2 sensors containing 0-10.0 wt% Gd2O3 calcined at 450 degrees C were measured in presence of 300 ppm CO, 10-1000 ppm ethanol and 1.0 vol% of methane in air at 150-430 degrees C. The sensor containing 10 wt% Gd2O3 is highly sensitive and selective to ethanol in presence of CO, methane, and three volatile organic compounds, at 150 degrees C. At the same low temperature, as the Gd2O3 content of the sensor increases from 2.5 to 10%, its response to ethanol dramatically enhances by about 263 times and the resistance in air changes by more than 4 orders of magnitude. Relative humidities higher than 50% eliminate the 10% Gd2O3-SnO2 sensor responses to CO and CH4 and the sensor shows absolute selectivity to ethanol. (C) 2016 Elsevier B.V. All rights reserved.