Highly reliable and selective ethanol sensor based on α-Fe2O3 nanorhombs working in realistic environments

A highly reliable and selective ethanol gas sensor working in realistic environments based on alpha-Fe2O3 (alpha-Fe2O3) nanorhombs is developed. The sensor is fabricated by integrating alpha-Fe2O3 nanorhombs onto a low power microheater based on micro-electro-mechanical systems (MEMS) technology. The alpha-Fe2O3 nanorhombs, prepared via a solvothermal method, is characterized by transmission electron microscopy (TEM), Raman spectroscopy, x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). The sensing performances of the alpha-Fe2O3 sensor to various toxic gases are investigated. The optimum sensing temperature is found to be about 280 degrees C. The sensor shows excellent selectivity to ethanol. For various ethanol concentrations (1 ppm-20 ppm), the response and recovery times are around 3 s and 15 s at the working temperature of 280 degrees C, respectively. Specifically, the alpha-Fe2O3 sensor exhibits a response shift less than 6% to ethanol at 280 degrees C when the relative humidity (RH) increases from 30% to 70%. The good tolerance to humidity variation makes the sensor suitable for reliable applications in Internet of Things (IoT) in realistic environments. In addition, the sensor shows great long-term repeatability and stability towards ethanol. A possible gas sensing mechanism is proposed.