Electrospinning preparation of mesoporous spinel gallate (MGa2O4; MNi, Cu, Co) nanofibers and their M(II) ions-dependent gas sensing properties

Transition metal spinel semiconductors, with a general formula of AB2O4, have been shown as a promising group for gas sensor applications. This paper reports a simple and effective electrospinning method to systematically prepare mesoporous MGa2O4 (MNi, Cu, Co) nanofibers. It is found that gas sensing reaction process of the materials is decisively influenced by transition metal M(II)-ions. The gas response tends to decrease in the order of NiGa2O4 > CuGa2O4 > CoGa2O4. In addition, NiGa2O4 and CoGa2O4 show p-type behaviors, and CuGa2O4 shows an n-type behavior. Further analysis reveals that charge carrier hopping (e− hopping or h+ hopping) processes between different valent metal cations, which is mainly dominated by octahedral sites of spinel, are responsible for the conductivity type, the surface redox reaction and thereby the gas sensing properties.