Finally, the paraffin reinforcement layer was removed by immersing the grid for two hours in three consecutive heptane baths and dried in the fume hood overnight. Subsequently, the graphene on TEM grid was floated on the Zn(NO3)2 aqueous solution (18 ml, 6.94 mM) in a petri dish, followed by the addition of a bim aqueous solution (2 ml, 0.06 M) for 10 min. After that, the grid was taken out to stop the reaction.