Light-activated nanozymes (adenosine monophosphate-Ce3+-fluorescein) for colorimetric detection of carbaryl by breaking a pH limitation

The convenient monitoring of carbaryl is necessary because of its serious threat to environment and public health. In enzyme inhibition-based colorimetric detection, the oxidation of colorimetric substrate (3,3 ',5,5 '-tet-ramethyl benzidine) only proceeds at pH below 5, while most enzymes only work efficiently at neutral pH. Here fluorescein was doped in coordination polymers to serve as novel nanozymes for efficient light-activated oxidation. The long triplet state lifetime of Ce3+ made the substrate oxidize at neutral pH to overcome a pH limitation. Furthermore, one interesting light-activated biosensing system was developed based on the carbaryl's unique toxicity towards acetylcholinesterase. It can sensitively detect carbaryl at neutral pH with a limit of detection 1.53 mu g/L, which is much lower than the maximum residue limit (50 mu g/L) in European Union data-base. It also enjoys a good selectivity for carbaryl detection over other pesticides or endocrine disruptors. Besides, the biosensing system showed a satisfied performance to detect carbaryl in both water and food samples.

Automated summary

In this study, fluorescein-doped coordination polymers were used as nanozymes to efficiently oxidize carbaryl at neutral pH. A light-activated biosensing system was developed based on the unique toxicity of carbaryl towards acetylcholinesterase, enabling sensitive detection at neutral pH with good selectivity.