AuPd alloy nanozymes specifically boost peroxidase-like activity for accurate detection of acetylcholinesterase and organophosphorus pesticide.

To safeguard public health and ecosystem safety, precise and sensitive detection of acetylcholinesterase (AChE) activity and organophosphorus pesticides (OPs) is highly desired. Although nanozyme-enabled colorimetry is widely applied, the insufficient catalytic activity and selectivity of nanozymes hinder their performance. Herein, composition-tunable AuPd nanozymes with alloy-ratio-dependent peroxidase (POD)-like activity and specificity are prepared via a simple wet-chemical reduction. Experimental analyses reveal that AuPd alloy nanozymes with a mole ratio of 1:3 possess the highest POD-like activity, with maximum reaction velocities approximately 7-fold and 3.5-fold higher than those of AuPd and AuPd nanozymes, respectively. Moreover, the AuPd nanozyme shows negligible oxidase-like activity, effectively minimizing interference from dissolved oxygen and thereby enhancing the accuracy and sensitivity of colorimetric detection. Theoretical calculations reveal that AuPd nanozymes possess a high d-band center and are more likely to generate hydroxyl radicals (•OH), thus enhancing POD-like activity in the catalytic reaction. Leveraging the selective blocking of active sites by thiocholine, the resultant AuPd nanozyme-based colorimetric platform was developed to sensitively and selectively monitor AChE activity. Furthermore, by integrating AuPd with AChE in a cascade amplification strategy, OPs detection was achieved with high sensitivity, reaching a detection limit as low as 0.216 ng mL. Overall, this work presents an efficient approach for engineering nanozymes with elevated activity and selectivity, advancing the application of nanozyme-driven colorimetric biosensors.