Surface functional composition and sensor properties of ZnO, Fe$_2$O$_3$, and ZnFe$_2$O$_4$

Zinc and iron oxide (ZnO, Fe$_2$O$_3$) and zinc ferrite (ZnFe$_2$O$_4$) nanopowders are obtained by chemical co-precipitation. The gas-sensitive properties of materials upon exposure to acetone and ethanol vapors are analyzed. It is found that the sensitivity of ZnFe$_2$O$_4$ to ethanol and acetone is better than the sensitivity of simple oxides by one and two orders of magnitude, respectively. Analysis of the surface of the materials under study shows that the observed differences in their gas sensitivity are caused by a high concentration of Brönsted acid centers on the ZnFe$_2$O$_4$ surface, which can be involved in redox reactions and facilitate the selective adsorption of ethanol.