Hydrolysis enabled specific colorimetric assay of carbosulfan with sensitivity manipulation via metal-doped or metal-free carbon nanozyme

Precise determination of the carbamate pesticide carbosulfan is crucial for assessing the associated risks in food and environment. Due to the strong interaction between carbosulfan and target enzyme, current methods primarily depend on the acetylcholinesterase (AChE) inhibition strategy, which generally lacks selectivity. In this study, we propose a nanozyme colorimetric sensor for the specific carbosulfan detection, based on its distinctive hydrolysis property. In contrast to other pesticides, carbosulfan can be hydrolyzed to produce the reductive sulfide compound by the cleavage of N-S bond under acidic condition, thereby significantly hindering the nanozyme-mediated chromogenic reaction. Consequently, the absorbance is significantly correlated with carbosulfan concentration. Furthermore, the influence of nanozyme type is disclosed, and two oxidase-like carbon nanozymes were formulated, namely metal-free NC and metal-based CeO2@NC. However, the distinct active sites significantly impact the proposed sensor. For CeO2@NC-based sensor, the produced sulfide compounds not only poison Ce active site, but also consume the reactive oxygen species, thereby, exhibiting high sensitivity with low detection limit of 3.3 nM. By contrast, the metal-free nature of NC allows the assay to remain unaffected by coordination effects, exhibiting superior anti-interference capability. This work not only offers an efficient alternative to the conventional method for detecting carbosulfan specifically, but also shed light on the role of metal-based or metal-free nanozyme among analytical applications.