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A highly reliable and selective ethanol gas sensor working in realistic environments based on alpha-Fe2O3 (α-Fe2O3) nanorhombs is developed.The sensor is fabricated by integrating α-Fe2O3 nanorhombs onto a low power microheater based on micro-electro-mechanical systems (MEMS) technology.The α-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 α-Fe2O3 sensor to various toxic gases are investigated.The optimum sensing temperature is found to be about 280 ℃.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 ℃,respectively.Specifically,the α-Fe2O3 sensor exhibits a response shift less than 6% to ethanol at 280 ℃ when the relative humidity (RH) increases from 30% to 70%.The good tolerance to humidity variation makes the sensor suitable for reliable applications in Inteet 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.