Sensing behavior to ppm-level gases and synergistic sensing mechanism in metal-functionalized rGO-loaded ZnO nanofibers

Noble metal-functionalized, reduced graphene oxide (rGO)-loaded metal oxides are a new class of ternary composites that combine the advantages of each component, resulting in exceptional materials. But, there are few reports on their use as gas sensors. This paper reports the gas sensing behavior of Au or Pd-functionalized rGO-loaded ZnO nanofibers (NFs) synthesized by using a combination of facile, cost-effective sol-gel and electrospinning methods. An examination of the gas sensing properties revealed that Au-functionalized NFs have a very high response to CO gas. In particular, the gas response (Ra/Rg) to 1 ppm of CO was as high as 23.5, whereas Pd-functionalized NFs showed a high response to C6H6 gas (11.8 to 1 ppm C6H6). The presence of rGO/ZnO heterointerfaces, the catalytic effect of Au and Pd nanoparticles (NPs), and the high surface area of NFs were the main factors that contributed to the strong response of the Au or Pd-functionalized rGO-loaded ZnO NFs sensors. These results show that the combination of noble metals, such as Au or Pd NPs, with rGO and ZnO can impart new gas sensing functionality that is potentially useful for CO or C6H6 sensing applications, respectively.