Reduced graphene oxide functionalized with Cu nanoparticles: Fabrication, structure, and sensing properties

• We fabricated NO2 gas sensors by using RGOs functionalized with Cu nanoparticles.
• The sensitivity was significantly enhanced by the Cu functionalization.
• We examined changes in response and recovery times by the Cu functionalization.

We have fabricated the NO2 gas sensors by using reduced graphene oxide (RGO) functionalized with copper (Cu) nanoparticles, revealing that the sensitivity was significantly enhanced by the Cu functionalization. Transmission electron microscopy indicated that the nanoparticles with a cubic Cu phase were attached on the surface of RGO. Raman spectra revealed that the structural disorder of RGO was increased by the Cu-functionalization. We performed the NO2 gas sensing test, revealing that the sensor response of RGOs was increased by 326% by means of the Cu-functionalization. We have discussed the associated mechanisms. In addition, we have ascribed the functionalization-induced changes of response and recovery times to the increase of low-energy binding sites.