Porous NiO nanosheets self-grown on alumina tube using a novel flash synthesis and their gas sensing properties

Abstract

Porous NiO nanosheets were self-grown on an alumina tube with a pair of Au electrodes connected by platinum wires via a simple solution combustion synthesis. A cubic NiO phase was obtained by a mixed solution of an oxidizer of nickel nitrate and a fuel of ethylene glycol (EG) at 400 °C. The phases and the morphologies of the materials self-grown on an alumina tube were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that the alumina tube was entirely covered by NiO nanosheets with several micrometers in thickness. The NiO nanosheets on the surface of the tube were assembled by a large number of nanoparticles of irregular shapes and pores with different sizes. The electronic and gas-sensing characteristics of the self-grown porous NiO nanosheets for volatile organic compound (VOC) vapours (ethanol, acetone, methanol, and formaldehyde) were investigated. The resistance of the sensor directly based on the self-grown NiO dramatically drops from 100–240 °C, and then slightly decreases with further increasing temperature to about 28 kΩ at 400 °C. The sensor based on the self-grown NiO exhibits low detection limit, fast response and recovery and wide dynamic range detection to VOC vapours, especially ethanol, at the respectively optimal operating temperatures.