▎ 摘　　要

The formation of graphene-encapsulated copper nanoparticles was investigated through carbonizing a mixture of kraft lignin and copper sulfate pentahydrate at the temperature up to 500 degrees C. The abrupt conversion of copper ions into its atoms occurred at 300 degrees C. The formation of graphene layers surrounding copper nanoparticles started as early as the heating temperature reached 400 degrees C. Most copper nanoparticles were covered with less than five graphene layers when the temperature reached 500 degrees C. The average diameter of graphene-encapsulated copper nanoparticles was 12.75 and 11.62 nm for temperature at 400 and 500 degrees C, respectively. The heating temperature had no significant effect on the size of graphene-encapsulated copper nanoparticles in the evaluated temperature range. It is believed that the formation of graphene-layered shell surrounding copper nanoparticles is based on the mechanism of self-limiting theory with solid carbon as the carbon source. (C) 2016 Elsevier B.V. All rights reserved.