Carbon dots co-doped with nitrogen and chlorine for “off-on” fluorometric determination of the activity of acetylcholinesterase and for quantification of organophosphate pesticides


Nitrogen and chlorine dually-doped carbon dots (N,Cl-CDs) were hydrothermally prepared starting from 4-chloro-1,2-diaminobenzene and dopamine. The N,Cl-CDs exhibit strong orange fluorescence, with excitation/emission maxima at 420/570 nm and a relative high quantum yield (15%). The N,Cl-CDs were employed to detect acetylcholinesterase (AChE) activity and organophosphate pesticides (OPs) which are enzyme inhibitors. Acetylthiocholine is enzymatically split by AChE to produce thiocholine which triggers the decomposition of Ellmans’s reagent to form a yellow colored product (2-nitro-5-thiobenzoate anion). The product causes an inner filter effect (IEF) on the fluorescence of the N,Cl-CDs. Fluorescence decreases linearly in the 0.017 to 5.0 Unit·L−1 AChE activity range, and the detection limit is 2 mUnit·L−1. If organophosphates are present, the activity of AChE becomes increasingly blocked, and this leads to a less expressed IFE and an increasing recovery of fluorescence. This was used for the quantification of OPs. Response is linear in the 0.3–1000 μg·L−1 OP concentration range with a 30 ng·L−1 detection limit.

Schematic representation of the synthesis of nitrogen and chlorine dually-doped carbon dots (N,Cl-CDs) and the recognition of organophosphate pesticides by N,Cl-CDs.

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This work was financially supported by National Natural Science Foundation of China (21707030) and Wuhan Youth Science and technology plan (2016070204010133).

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Correspondence to Yu He.

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Yang, M., Liu, M., Wu, Z. et al. Carbon dots co-doped with nitrogen and chlorine for “off-on” fluorometric determination of the activity of acetylcholinesterase and for quantification of organophosphate pesticides. Microchim Acta 186, 585 (2019).

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  • Nitrogen and chlorine co-doped carbon dots
  • Acetylcholinesterase activity
  • Organophosphate pesticides
  • Inner filter effect
  • Ellmans’s reagent