Iron/phosphorus co-doped carbon nanozyme for colorimetric sensing of organophosphorus pesticides in food

In this work, a peroxidase-like (POD-like) nanozyme of Fe/P-NC was synthesized by doping phosphorus (P) and nitrogen (N) to manipulate iron (Fe) activity centers, which showed catalytic activity and kinetics comparable to those of natural HRP. Based on the efficient POD-like activity of the Fe/P-NC nanozyme and cascaded catalytic reactions with acetylcholinesterase (AChE), we constructed a colorimetric, affordable and sensitive sensing platform to detect organophosphorus pesticides (OPs). In the presence of AChE, the POD-like activity of the prepared Fe/P-NC was suppressed, which weakened the Fe/P-NC-catalyzed oxidation of TMB. After the introduction of OPs, the catalytic activity of the Fe/P-NC nanozyme was restored, resulting in efficient oxidation of TMB and an increasing blue color. By monitoring the variation in UV-vis absorbance, OPs could be quantitatively analyzed. The proposed colorimetric method exhibited superior analytical performance, with a wide detection range of 0.5-100 ng mL^-1 and a low detection limit of 0.13 ng mL^-1 for OPs. The assay was successfully employed to detect methyl parathion in fruit and vegetable samples. This work provides new insights into the design of new efficient nanozymes for the rapid and low-cost detection of OPs in real samples.