Design of Hydrothermally Derived FeO Rods with Enhanced Dual Functionality Via Sputtering Decoration of a Thin ZnO Coverage Layer.

The FeO-ZnO composite rods were successfully synthesized by combining hydrothermal growth of FeO rods and sputtering deposition of a thin ZnO coverage layer. Two types of the FeO rods with round and rectangular cross-sectional morphologies grown via control of the urea content in hydrothermal growth processes were used as rod templates to fabricate the FeO-ZnO composite rods. The FeO-ZnO composite rods exhibited an improved photoelectric conversion efficiency in the FeO rods via a construction of a heterogeneous structure. The photocatalytic degradation performance of rhodamine B dyes with FeO rods was substantially increased via sputtering decoration of a thin ZnO coverage layer on the FeO rods. Moreover, the FeO-ZnO composite rods exhibited superior acetone vapor-sensing responses than the pristine FeO rods herein. The extended optical absorption ability together with the enhanced photoinduced charge separation efficiency via construction of the FeO-ZnO heterogeneous system explained the improved photoactivity of the composite rods. Furthermore, the formation of a heterojunction between the FeO and ZnO increased the interfacial potential barrier height and enhanced the sensor resistance variation size upon exposure to the acetone vapor. This accounted for the improved gas-sensing performance of the FeO-ZnO composite rods. The experimental results herein provide a promising approach to design FeO-based composite rods with desirable photocatalytic and gas-sensing functionalities.