A novel composite film derived from cysteic acid and PDDA-functionalized graphene: Enhanced sensing material for electrochemical determination of metronidazole

► Facile microwave-heating procedure for preparing PDDA-functionalized graphene. ► Cysteic acid/PDDA-functionalized graphene composite film as a new electrode material. ► High electrocatalytic activity for metronidazole reduction. ► Wide linear range, low detection limit for the determination of metronidazole. ► Application in practical samples with satisfactory results.