From Poisoning to Signal Transduction: d-Band Modulated Au@RuPt Nanozyme for Oxygen Reduction Reaction...

The widespread use of organophosphate pesticides (OPs) critically endangers food safety and environmental health, necessitating highly sensitive detection strategies. Herein, we report a d-band modulated Au@RuPt core-shell nanozyme for ultrasensitive OP detection via an oxygen reduction reaction (ORR) inhibition mechanism. The Au@RuPt nanodots (RuPt shell ∼1.02 nm on Au core ∼3.08 nm) exhibit enhanced ORR activity (Tafel slope: 49.89 mV dec^-1) with a dominant four-electron pathway. Mechanistic studies reveal that Ru incorporation upshifts the d-band center, promoting thiocholine (TCh) chemisorption and consequent ORR poisoning. The biosensing mechanism relies on TCh-induced ORR inhibition and its recovery upon OP-mediated acetylcholinesterase inactivation, enabling a "signal-on" readout. The sensor exhibits a detection limit of 0.0264 ng mL^-1 toward phoxim, alongside excellent specificity, reproducibility (RSD < 1.62%), stability (>94.6% after 30 days), and real-sample recoveries (96.3-104.6%). It also enables in situ pesticide monitoring on plant leaves and AChE activity evaluation with IC₅₀ quantification for multiple OPs. This work establishes an alloy nanozyme platform for ORR-based electrochemical biosensing, opening new avenues for point-of-need applications in agricultural safety, toxicology, and clinical diagnostics.