Copper Ion-Induced Self-Assembled Aerogels of Carbon Dots as Peroxidase-Mimicking Nanozymes for Colorimetric Biosensing of Organophosphorus Pesticide

Establishing a rapid and sensitive biosensing method for organophosphorus pesticide (OP) is essential because of its pollution to the environment and potential harm to human health. In the report, copper ion-induced self-assembled aerogels of carbon dots are coupled with acetylcholinesterase and choline oxidase to construct a multienzyme cascade catalysis-based colorimetric biosensor for the detection of OP dichlorvos. The copper-carbon dot aerogels (Cu-CDs) are massively fabricated using copper as the metal binding sites and carbon dots derived from sodium tartrate and adenine as building units. The Cu-CDs are verified to possess high peroxidase-mimicking activity toward the hydrogen peroxide-oxidation of o-phenylenediamine. It is revealed that the generation of reactive oxygen species (ROS) including OH, O-2(-), and O-1(2) is involved in the peroxidase-mimicking process, and the high peroxidase-mimicking activity of Cu-CDs results from the synergistic effects of abundant ROS, fast Cu(II)/Cu(I) redox cycling, plentiful catalytically active metal sites, and three-dimensional porous structures. The dichlorvos biosensor achieves a linear range of 0.02-0.3 mu M with a limit of detection of 7.6 nM. The proposed sensor is successfully applied to detect dichlorvos in real samples, including cabbage, pakchoi, and lake water, and the results compare well with those from a reference gas chromatography method.