Attachment of Co3O4 layer to SnO2 nanowires for enhanced gas sensing properties

We prepared nanocomposites of n-SnO2/p-CO3O4 for application in chemical sensors. In order to fabricate p-CO3O4-decorated n-SnO2 nanowires, we sputtered a Co layer and subsequently annealed the material in air ambient. Characterization revealed that crystalline cubic CO3O4 with a tubular-like structure was attached to the surface of SnO2 core nanowires. We carried out sensing tests at 573 K in at NO2 gas concentrations ranging between 2 and 10 ppm. The sensor response was increased both by adding the CO3O4 layer and also by decreasing the thickness of the CO3O4 layer from 19.2 to 6.4 nm. We proposed possible mechanisms to explain the enhanced sensor properties obtained by CO3O4-functionalization. CO3O4-functionalized SnO2 nanowires exhibited a higher sensor response than pristine nanowires, not only due to the heterostructure-induced depletion of n-SnO2 region but also due to the surface effects of CO3O4. The generation of hole-accumulated CO3O4 layer in case of thicker-layered nanowires will decrease the sensor response. We demonstrated that CO3O4-functionalized SnO2 nanowire sensors can be used as gas sensors at very low concentrations. (C) 2016 Elsevier B.V. All rights reserved.