Enhancement of gas sensing properties by the functionalization of ZnO-branched SnO2 nanowires with Cr2O3 nanoparticles

Complex metal oxides such as functionalized branched nanowires (NWs) are a new category of nanocomposites with unique properties for gas sensing applications. In the present work, we studied the gas sensing properties of Cr2O3-functionalized ZnO-branched SnO2 NWs, inspired by their high surface area and numerous resistive points. These NWs were studied and compared with pristine SnO2 NWs and ZnO-branched SnO2 NWs. To prepare the functionalized NWs, ZnO-branched SnO2 NWs were sputter coated with a Cr layer and then annealed at 500 degrees C to produce isolated Cr2O3 NPs on the ZnO branches. Results of X-ray diffraction, scanning electron microscopy, and lattice-resolved transmission electron microscopy collectively showed that Cr2O3-functionalized ZnO-branched SnO2 NWs were successfully formed. Cr2O3 functionalization was found to greatly improve the sensors' response to NO2 gas. Furthermore, the sensors' good selectivity was demonstrated by testing them in the presence of various interfering gases. The underlying gas sensing mechanisms are discussed herein in detail. We believe that the Cr2O3-functionalized ZnO-branched SnO2 NWs reported herein are promising sensors for the highly sensitive and selective detection of NO2 gas. (C) 2017 Elsevier B.V. All rights reserved.