Core-shell structure N-doped graphene quantum dots Fe 3 O 4 /Co 3 O 4 nanoparticles for colorimetric detection of H 2 O 2

Hydrogen peroxide (H2O2) is an environmentally friendly intermediate in the environmental field and also plays an important role in human metabolism, but the production and accumulation of excessive H2O2 will cause harm to the human body, resulting in serious damage to cells. Therefore, N-doped graphene quantum dots Fe3O4/ Co3O4 nanoparticles with core-shell structure were prepared by in-situ synthesis and precipitation. The experimental results show that the prepared Co3O4 nanoparticles have more efficient peroxidase activity than Co3O4 nanoparticles alone. It can catalyze the oxidation of 3, 3, 5, 5-tetramethylbenzidine (TMB) to produce a blue product (TMBox) in the presence of H2O2. In addition, Co3O4 with negative charge in the shell can produce a strong electrostatic driving coordination effect with positively charged TMB, which enhances the affinity between the nanoparticles and the substrate, and selectively catalyzes H2O2 oxidation of colorless TMB to turn it blue. Based on these experimental results, a simple, low-cost, and efficient colorimetric method for H2O2 detection was established, which showed a sensitive response to H2O2 in the range of 0.02-2.5 mu M with a detection limit of 2.3 nM. In addition, due to the magnetic properties of the prepared nanoparticles, they could be easily recovered by applying a magnetic field. This research provides a viable approach for magnetic nanomaterials with encouraging prospects for environmental monitoring, biosensing, and more.