Construction of a recyclable oxidase-mimicking Fe₃O₄@MnO_x-based colorimetric sensor array for quantifying and identifying chlorophenols

Chlorophenols (CPs) are known as a class of pollutants posing a great threat to the environment and human health because of their carcinogenesis and teratogenesis, and thus exploring convenient and efficient methods for their detection and identification becomes particularly important. Herein, we report a recyclable colorimetric sensor array according to the oxidase-mimicking catalytic characteristics of Fe₃O₄@MnO_x for the high-performance quantification and differentiation of typical CPs. The core-shell Fe₃O₄@MnO_x prepared by growing oxidase-like MnO_x nanoflakes on the surface of magnetic Fe₃O₄ particles via a hydrothermal process can exhibit excellent catalytic activity to trigger the color reaction of CPs and 4-aminoantipyrine with the participation of O₂. By utilizing the Fe₃O₄@MnO_x-catalyzed color reaction, high-sensitivity quantitative analysis of CPs, taking 2-chlorophenol as a model, was realized, providing a detection limit as low as 0.85 μM. Given different chlorine substitution places and numbers in CPs impact the reaction kinetics diversely, a new nanozyme-based colorimetric sensor array was further constructed for the successful differentiation of various CPs with the help of hierarchical cluster analysis and principal component analysis. Accurate double-blind identification of unknown samples using the proposed sensor array was also demonstrated, indicating its reliability for practical practice.