Nitrogen dioxide (NO2) as one of the most serious air pollution is harmful to people's health, therefore high- performance gas sensors is critically needed. Here, Cu-modified carbon spheres/reduced graphene oxide (Cu@ CS/RGO) composite have been prepared as NO2 gas sensor material. Carbon sphere in the interlayer of RGO can increase the specific surface area of RGO. Copper nanoparticles decorated on the surface of CS can effectively enhance the adsorption activity of RGO as supplier of free electrons. The experimental results showed that its particular structure improved the gas sensitivity of RGO at different NO2 concentrations at room temperature. (C) 2018 Elsevier B. V. All rights reserved.