Non-enzymatic colorimetric strategy for malathion detection based on Pt nanoparticles decorated porphyrin Zr metal-organic framework spheres.

The presence of malathion (Mal) residues in food and water environment have garnered widespread public concern. Here, we developed PCN-224-supported Pt nanozymes through an in-situ reduction method, where the porous porphyrin framework and Pt sites jointly promote electron transfer and provide more active centers, leading to drastically enhanced oxidase (OXD)-mimicking activity. The obtained PCN-224@Pt can directly oxidize colorless TMB to blue oxTMB without H2O2, while the specific adsorption of Mal on the nanozyme surface will shield active sites and inhibit the catalytic reaction. Accordingly, a colorimetric sensor was then established to achieve sensitive determination of Mal in a linear detection range from 0.01 to 2.5 μg/mL with a low detection limit (LOD) of 6.62 ng/mL. Moreover, this platform displayed high selectivity and stability in food and water samples, with satisfactory recoveries of 90.1 %-107.7 % (RSDs < 9.31 %). This strategy provides a new attempt to construct nanozyme probes for direct detection of Mal, suitable for visual analysis in food and water environments.