Iron single-atom nanozyme with dual enzyme-like activities for detection of environmental pollutants and colorimetric sensing array to identification of phenolic species.

Organophosphorus pesticides (OPs) and phenolic compounds are widely residual in the environment, and it is necessary to construct simple and effective detection methods. Herein, iron single-atom (Fe-N/C) nanozyme with double mimetic enzyme catalytic properties was designed and prepared through a controlled pyrolysis strategy of Fe-ZIF-8 precursors. The double enzyme-like activities of Fe-N/C were discussed in depth. The oxidase-like (OXD) activity refers to Fe-N/C acting as an oxidase mimetic to generate singlet oxygen (1O2) with the assistance of O2, thereby enabling the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). The laccase-like (LAC) activity involves Fe-N/C catalyzing the oxidation of phenolic substances, and the chromatic reaction occurs between the resulting products and 4-aminophenazone (4-AP). The colorimetric sensor for parathion methyl was proposed based on OXD-like activity with a detection limit of 0.14 ng/mL, while the sensing system for 2,4-dichlorophenol (2,4-DP) was established based on LAC-like activity with a detection limit of 0.052 μg/mL. Furthermore, a fingerprint recognition model design for phenolic compounds was integrated with multi-signal sensing arrays responsive to both enzymatic activities and principal component analysis (PCA), enabling precise identification and differentiation of five structural phenolic substances including catechol (CC), resorcinol (RES), hydroquinone (HQ), m-aminophenol (m-AP), and 2,4-DP. This study provides a novel strategy for rapid screening and multi-dimensional sensing analysis of organic pollutants in real environmental water samples.