Fluorescent black phosphorus quantum dots as label-free sensing probes for evaluation of acetylcholinesterase activity

In this work, a fast, sensitive and label-free fluorescence sensing platform for evaluating the acetylcholinesterase (AChE) activity was developed based on the inner filter effect (IFE) between black phosphorus quantum dots (BP QDs) and 2-nitro-5-thiobenzoate anion (TNB). BP QDs were successfully synthesized from bulk BP through a facile top-down route by sonication-assisted solvothermal method. The as-prepared QDs exhibit green fluorescence with a relative high quantum yield, good photostability and relative pH resistance. 5,5′-Dithiobis-(2-nitrobenzoic acid) (DTNB), as a well-known Ellman's reagent, can react with thiol groups to form TNB. Based on the IFE between BP QDs and TNB, a sensitive and label-free sensing platform was developed for fluorescent measurement of thiols. As a proof-of-concept application, the platform was further applied in the evaluation of AChE activity by using acetylthiocholine as the substrate.