▎ 摘　　要

The development of electrochemical biosensors for the simultaneous detection of ascorbic acid (AA), dopamine (DA), uric acid (UA), tryptophan (Trp), and nitrite (NO2-) in human serum is reported in this work. Free-standing graphene nanosheets were fabricated on Ta wire using the chemical vapor deposition (CVD) method. CVD graphene, which here served as a sensing platform, provided a highly sensitive and selective option, with detection limits of AA, DA, UA, Trp, and NO2- of 1.58, 0.06, 0.09, 0.10, and 6.45 ae M (S/N = 3), respectively. The high selectivity of the electrode is here explained by a relationship between the bandgap energy of analyte and the Fermi level of graphene. The high sensitivity in the oxidation current was determined by analyzing the influence of the high surface area and chemical structure of free-standing graphene nanosheets on analyte adsorption capacity. This finding strongly indicates that the CVD graphene electrode can be used as a biosensor to detect five analytes in human serum.