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 Cr 2 O 3 -functionalized ZnO-branched SnO 2 NWs, inspired by their high surface area and numerous resistive points. These NWs were studied and compared with pristine SnO 2 NWs and ZnO-branched SnO 2 NWs. To prepare the functionalized NWs, ZnO-branched SnO 2 NWs were sputter-coated with a Cr layer and then annealed at 500 °C to produce isolated Cr 2 O 3 NPs on the ZnO branches. Results of X-ray diffraction, scanning electron microscopy, and lattice-resolved transmission electron microscopy collectively showed that Cr 2 O 3 -functionalized ZnO-branched SnO 2 NWs were successfully formed. Cr 2 O 3 functionalization was found to greatly improve the sensors’ response to NO 2 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 Cr 2 O 3 -functionalized ZnO-branched SnO 2 NWs reported herein are promising sensors for the highly sensitive and selective detection of NO 2 gas.