A dual-mode gold-inlaid Fe-MOFs nanoenzyme was constructed by SMILES for phoxim detection based on enzyme inhibition cascade and the construction of a smartphone colorimetric platform.

This study presents a novel method using a gold-inlaid iron-based nanoenzyme (Au@MIL-53(Fe)) to rapidly detect phoxim, a neurotoxic organophosphate pesticide, in animal feed. The porous structure of MIL-53(Fe) acts as small-molecular ionic isolation lattices (SMILES), creating a solid-matrix surface confinement induced fluorescence enhancement (SSCIFE) environment for gold nanoclusters (AuNCs), enabling stable fluorescence at 642 nm and 435 nm. Additionally, it catalyzes TMB oxidation by hydrogen peroxide for colorimetric detection. Ascorbic acid 2-phosphate (AAP) is hydrolyzed by acid phosphatase (ACP) to ascorbic acid (AA), altering fluorescence and color signals. Phoxim inhibits ACP, modulating these signals and restoring the TMB color shift. The detection limits are 1.10 ng/mL (fluorescence), 1.02 ng/mL (colorimetry), and 1.04 ng/mL (smartphone colorimetric platform), respectively. The recovery rate of this method in feed is 84% ∼ 116%. It offers a rapid, sensitive, and reliable solution for pesticide monitoring and food safety assurance.