CoO Nanotubes Loaded on Graphene and Modified with Porphyrin Moieties for Colorimetric Sensing of Dopamine

Abstract

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 •O2–). 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 μM) with a much lower LOD (0.1391 μM). The Por/CoO/GO-based colorimetric platform has been validated by determining DA in real serum samples.