▎ 摘　　要

In this paper, CoO nanotubes loaded on the surface of graphene oxide (GO) have been first modified by 5,10,15,20-tetrakis(4-carboxyl phenyl)porphyrin (Por) by a hydrothermal method. Por/CoO/GO exhibits excellent peroxidase-like activity, which is evaluated by virtue of the chromogenic substrate 3,3,5,5-tetramethylbenzidine (TMB). In the presence of H2O2, Por/CoO/ GO nanoperoxidase can rapidly catalyze colorless TMB to be oxidized into blue oxTMB, which is distinguished visually in 1 min. The experimental data including fluorescence and electrochemistry data and radical scavengers confirm that the catalytic mechanism of Por/CoO/GO is ascribed to electron transfer between substrates, as well as produced active species (h(+) and center dot O-2(-)). Based on Por/CoO/GO nanoperoxidase, a fast colorimetric sensor for H2O2 has been established for a wide range of concentrations (0.1-3 mM) with a lower limit of detection (LOD = 0.2942 mM). Notably, the blue color of oxTMB can be gradually faded in the presence of dopamine (DA) with various concentrations. Thus, a fast, cheap, and convenient colorimetric sensor has been designed to monitor DA in a wide range (0.2-10 mu M) with a much lower LOD (0.1391 mu M). The Por/CoO/GO-based colorimetric platform has been validated by determining DA in real serum samples.