A fluorescence resonance energy transfer sensor based on quaternized carbon dots and Ellman's test for ultrasensitive detection of dichlorvos

Here we first reported an ultrasensitive fluorescence resonance energy transfer (FRET) biosensor of dichlorvos based on carbon dots and the traditionally colorimetric Ellman's test. In Ellman's test, the absorption intensity of 5-thio-2-nitrobenzoic acid anion (TNB−) at 412 nm can be used for the determination of acetylcholinesterase (AChE) and its inhibitor. We chose TNB− as energy acceptors to construct a FRET sensing system of AChE and its inhibitor. Quaternized carbon dots (Q-CDs) were chosen as energy donors to form an effective FRET system. By a two-step synthetic method, the Q-CDs with high quantum yield (34.2%) were successfully prepared. Experimental results showed TNB− can quench the fluorescence of Q-CDs to a large extent, which indicated an effective FRET between Q-CDs and TNB− was successfully established. As the inhibitor of AChE and common organophosphorus insecticide, dichlorvos can be detected using this sensing system. Under optimal conditions, the linear range of dichlorvos was 5.0 × 10−11-1.0 × 10−7 M. Owing to the high sensitivity and green fluorescent material with high quantum yield, this FRET sensing system was adaptable for automated analyzers using in the rapid determination of a great quantity of samples.