Target-tunable colorimetric sensor array based with mixed-valence cerium-centered metal-organic framework nanozyme for on-site sensitive detection of pyridaphenthion bioaccumulation in crops

Pyridaphenthion, as a broad-spectrum insecticide, warrants attention regarding its residue in crops and toxicity. Herein, a mixed-valence cerium-based metal-organic framework (CeMOF) nanozyme was synthesized via in-situ partial oxidation. The reversible Ce(IV)/Ce(III) nodes in CeMOF employed as the tunable catalytic switch. The nodes endowed the nanozyme with peroxidase-like activity for oxidizing colorimetric substrate with blue signals. The acid phosphatase (ACP) reduced the Ce(IV)/Ce(III) ratio and suppressed the peroxidase-like activity. Combined with the inhibiting activity of pyridaphenthion against ACP, the catalytic activity of CeMOF could be aroused by pyridaphenthion target. This mechanism facilitated the highly sensitive detection of pyridaphenthion through natural and artificial cascade catalysis. By convenient colorimetric analysis and visual instrument-free-based on-site approach compatible with smartphone, the array achieved the pyridaphenthion bioaccumulation determination with a detection limit of 0.099 ng mL−1. This presented cascade catalysis sensing array not only lighted up the way for dedicated design of nanozyme with target-triggered switch, but also provided an intelligent and efficient solution for on-site pesticide residue monitoring.