Investigation of the Gas-Sensing Performance of Electrospun TiO 2 Nanofiber-Based Sensors for Ethanol Sensing

This paper presents an investigation on the sensitivity toward ethanol of a gas sensor based on TiO 2 nanofibers deposited by electrospinning between interdigitated Pt electrodes. Morphological/structural characterizations by SEM/TEM show the formation of fibers, having a length up to hundreds of $\mu \text{m}$ and a diameter of about 60 nm, constituted of TiO 2 nanograins in the brookite phase. The sensitivity was evaluated by measuring, under constant polarization, the electrical current of the oxide nanofibers network at different ethanol concentrations (50, 100, and 150 ppm) and different operating temperatures (350 °C, 400 °C, and 450 °C). The experimental results show that the response increases linearly with increasing both the ethanol concentrations and the operating temperature. In particular, the best performance of the device toward the ethanol sensing is obtained when it works at 450 °C. An equivalent circuit, modeling the electrical behavior in relation with the material microstructure, was proposed by carrying out ac impedance spectroscopy investigation during gas sensing tests.