Covalent Functionalization of Graphene with Polysaccharides

Stable aqueous suspension of graphenes was fabricated from chemical reduction of graphene oxide with the assistance of hydroxypropyl cellulose or chitosan covalently grafted on the graphenes. First, pristine graphite was oxidized using a two-step method (H2SO4 + HNO3 followed by KMnO4). The oxidation-introduced carboxyl groups in graphene oxide were then converted into acyl chloride with thionyl chloride. Subsequently, hydroxypropyl cellulose or chitosan was covalently grafted onto the activated graphene oxide through esterification reactions. Finally, the functionalized graphene oxide was chemically reduced to graphene nanosheets with hydrazine.