A facile "off–on" fluorescence sensor for pentachlorophenol detection based on natural N and S co-doped carbon dots from crawfish shells.

[Display omitted] • Natural N and S co-doped carbon dots (NSCDs) were fabricated by hydrothermal method. • The prepared NSCDs exhibited a blue emission with a quantum yield up to 18.57%. • An "off–on" fluorescence sensor for pentachlorophenol (PCP) assessment has been successfully established. Natural N and S co-doped carbon dots (NSCDs) were synthesized via hydrothermal synthesis using food-derived crawfish shells as green precursors. The relationship between quantum yield (QY) and protein content of six crawfish shells treated with different alkalis was investigated. The synthesized NSCDs displayed a large QY of 18.57 %, which was higher than most of the chitin-derived CDs. Due to the oxidation of hydroxyl radicals, adding H 2 O 2 and horseradish peroxidase (HRP) quenched the fluorescence of NSCDs, resulting in a detection limit (LOD) of 1.25 μM for H 2 O 2. The addition of pentachlorophenol (PCP) was supposed to consume part of the hydroxyl radicals and protect NSCDs from being oxidized. Accordingly, a facile and rapid "off–on" fluorescence sensor was developed to detect PCP with a LOD of 2.30 μM. Further, the method described was successfully used to detect PCP in three real samples. [ABSTRACT FROM AUTHOR]