A Pt/au@MnO2 Nanozyme-based colorimetric platform for discriminating and quantifying neonicotinoids in real samples

Neonicotinoids (NEOs) pose significant threats to environmental safety and the food chain. To overcome the limitations of conventional nanozymes in achieving simultaneous pesticide discrimination and ultrasensitive quantification, a tunable platinum/gold@manganese dioxide (Pt/Au@MnO 2 ) nanozyme was developed. The material was engineered by synthesizing urchin-like Pt/Au nanoparticles via a two-step hydrothermal method, followed by electrostatic self-assembly onto MnO 2 nanosheets. By modulating the Pt/Au to β-MnO 2 ratio, the nanozyme's activity could be precisely switched between laccase-like (LAC) and peroxidase-like (POD) modes. The LAC mode enabled discriminative analysis of four NEOs through distinct colorimetric fingerprints analyzed by principal component analysis (PCA). For quantification, the POD mode was amplified by glutathione (GSH), which enhanced the signal through a nucleophilic reaction, resulting in a visible color gradient from dark green to light yellow. This strategy achieved highly sensitive detection of imidacloprid with a wide linear range (10 −8 –10 −4  M), a low detection limit of 4.42 × 10 −9  M, and high accuracy in real samples (recoveries: 96.2–104.0%). This dual-mode platform offers a robust and practical strategy for on-site NEO monitoring in food safety and agricultural control.