This work was supported by Peruvian government agencies CONCYTEC and FONDECYT/World Bank (contract 026-2019 FONDECYT-BM-INC.INV) and the Sao Paulo Research Foundation (FAPESP) through the fellowships granted to J. M. G. (FAPESP 2018/16896-7).

Gas sensors are fundamental for continuous online monitoring of volatile organic com-pounds. Gas sensors based on semiconductor materials have demonstrated to be highly competitive, but are generally made of expensive materials and operate at high temperatures, which are draw-backs of these technologies. Herein is described a novel ethanol sensor for room temperature (25◦C) measurements based on hematite (α-Fe2O3 )/silver nanoparticles. The AgNPs were shown to increase the oxide semiconductor charge carrier density, but especially to enhance the ethanol adsorption rate boosting the selectivity and sensitivity, thus allowing quantification of ethanol vapor in 2–35 mg L−1 range with an excellent linear relationship. In addition, the α-Fe2O3/Ag 3.0 wt% nanocomposite is cheap, and easy to make and process, imparting high perspectives for real applications in breath analyzers and/or s...