Synthesis and gas-sensing properties of ZnO@NiCo2O4 core@shell nanofibers

In this paper, 1D ZnO nanofibers were selected as the backbones, which were prepared by a hydrothermal route. Afterward, porous NiCo2O4 nanosheets with large surface area were further grown on the surface of single crystal ZnO nanofibers via a chemical bath deposition. The structures and compositions of the as-prepared gas sensing materials were characterized. It was found that uniform porous NiCo2O4 nanosheets were anchored on the surface of ZnO nanofibers backbones with a low lattice mismatch at the interface of heterostructures. Gas sensing tests showed that this novel ZnO-core@NiCo2O4-shell nanocomposite exhibited improved gas-sensing performances towards methanol, such as high response, low detection limit and excellent stability. The response to 5 ppm methanol was about 1.96 (R-g/R-a), whereas pristine NiCo2O4 and ZnO showed negligible response. The enhanced gas-sensing properties were attributed to the unique core-shell heterojunctions between NiCo2O4 nanosheets and ZnO nanofibers resulting in an improved receptor function as well as transducer function.