Highly reliable and selective ethanol sensor based on α-Fe2O3 nanorhombs working in realistic environments**Project supported by the Research Foundation of Hangzhou Dianzi University, China and 2011 Zhejiang Regional Collaborative Innovation Center for Smart City, China.

Abstract

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 °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 °C, respectively. Specifically, the α-Fe2O3 sensor exhibits a response shift less than 6% to ethanol at 280 °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.