The influence of Fe loading on the optical and gas sensing characteristics of SnO2/ZnO heterostructures

In the present study, SnO2/ZnO heterostructures and iron (Fe) loaded SnO2/ZnO heterostructures were prepared using a simple two-step hydrothermal route by varying the Fe loading concentration in the range of 0.02–1.00 wt%. The effect of loading different concentrations of Fe on the surface of the SnO2/ZnO heterostructure was analyzed and discussed. X-ray powder diffraction patterns revealed rutile tetragonal and hexagonal wurtzite crystal structures. Scanning electron microscopic images showed spherical nanospheres and hierarchical nanostructures with an average diameter of 22 and 20 nm, for the SnO2/ZnO and 0.02–0.8 wt%/Fe/SnO2/ZnO respectively. Nonetheless, a 1.0 wt% Fe/SnO2/ZnO displayed platelets-like structures surrounded by hierarchical nanostructures. The optical band gap of the SnO2/ZnO heterostructure reduced from 3.1 eV to 1.9 eV upon loading Fe content. The photoluminescence spectra showed that all the materials contained a higher amount of surface defects. The 1.0 wt% Fe/SnO2/ZnO heterostructure-based sensor displayed enhanced response toward 100 ppm xylene. This improvement could be linked to the porous behaviour observed in the heterostructure of 1.0 wt% Fe/SnO2/ZnO nanoplatelets, which allowed more xylene gas adsorption.