▎ 摘　　要

Ultrasonication is an inherent part of the major routes for preparation of reduced graphene. It is used to exfoliate graphite oxide to graphene oxide with consequent reduction to reduced graphenes. Metallic impurities in graphenes, originating from the starting material, graphite, have a profound influence on many properties of graphene, such as the electrochemical, catalytic and electronic properties. We show here that ultrasonication greatly enhances the redox availability of metallic impurities within reduced graphenes. Such findings will have a dramatic influence on future graphene processing methodology and applications of graphene.