Characterization of sensing properties of a C/ZnO hierarchical nanostructure

An integration of zinc oxide (ZnO) nanowires (NWs) onto carbon micro-fibers (C) using electrochemical deposition and thermal oxidation approach is developed and used as a versatile resistive (oxidizing and reducing) gas sensor. This architecture is attractive because it permits to achieve mechanical flexibility, low cost and large-area fabrication. Being structured at both microscale and nanoscale, the ZnO-C sensor possesses a higher surface area, giving rise to a strong and very fast response/ recovery time. Additionally, the ZnO nanowires-carbon microfiber sensor is very simple to be manufactured, has a very low power consumption (less than 0.6?W) and is prepared without any litographic process. The sensor also exhibits excellent oxygen (~39ppm) and hydrogen (~120ppm of H2) sensing characteristics, showing a fast response on gas exposure (less than 10s), very good reproducibility and stability. Furthermore, the C-microfiber is as flexible as a fabric is, thus, the ZnO-C sensor could also be used in applications where flexibility is required. This architecture can also be expanded to other nanowire materials (CuO, Fe2O3, etc) widening the range of detected gases. We therefore believe that the integration of nanowires with carbon microfibers has the potential for being the next generation of simple and low cost sensor devices. This work was financially supported by the Fondazione CARITRO Project ODINO.