Nanostructured In2O3 has attracted extensive attention due to its promising chemical stability and excellent gas-sensing properties. In this work, Mg-doped In2O3 nanotubes (Mg-In2O3 NTs) have been prepared by calcination of precursor fibers derived from a facile electrospinning method. All samples are characterized by X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy, which clearly show the Mg dopants in In2O3 NTs. Despite the role of substitutional Mg in In2O3 as an acceptor, the Mg-In2O3 NTs have shown n-type conductivity in H2S and ethanol, respectively. As is expected, the sensor using Mg-In2O3 NTs exhibits a high sensitivity and selectivity toward H2S at a low operating temperature of 150 degrees C, and it maintains a relatively high response toward ethanol at 250-300 degrees C, which presents a significant increase in the sensor response compared to the sensor based on primary In2O3 NTs. Furthermore, a possible enhancement mechanism in Mg-In2O3 NT-based sensors is proposed from the oxygen vacancies and the kinetics of gas adsorption-desorption processes. (C) 2014 Elsevier B.V. All rights reserved.