Controllable synthesis of functional nanocomposites: Covalently functionalize graphene sheets with biocompatible L-lysine

► The biocompatible L-lysine functionalized graphene sheets (Gs/Lys) were synthesized controllably using a novel method. ► The Gs/Lys nanocomposites are water-soluble, biocompatible and chiral. ► A chiral graphene derivative was proposed.