Objective To develop a method capable of real-time,rapid,and visual detection of MEs,providing a powerful tool for early diagnosis and assessment of diseases.Methods In this study,flake graphene oxide(2D GO)with excellent peroxidase-like activity(POD-like)was prepared by a modified Hummers'method,and a sensing strategy for the rapid visual detection of MEs was constructed by integrating colorimetry with a smartphone.Results 2D GO can catalyse the decomposition of hydrogen peroxide(H2O2)to produce highly oxidative hydroxyl radicals(·OH),which oxidize the colourless 3,3',5,5'-tetramethylbenzidine(TMB)into blue ox-TMB.The strong reducing effect of MEs on the"2D GO+TMB+H2O2"colorimetric sensing system enables rapid visual detection of MEs.Conclusion The colorimetric platform constructed based on 2D GO has a wide linear detection range(10-1 000 μmol/L)and a good detection limit(LOD<7 μM),and was successfully used for the determination of MEs in foetal bovine serum samples,with satisfactory recovery rates.