One-step synthesis of V/Fe bimetallic nanozymes with synergistic activity for dual-mode detection of organophosphorus pesticides.

Current Prussian blue analogue (PBA)-based nanozyme suffers from poor catalytic activity, limiting their analytical performance. Nevertheless, current efforts focus on preparation of metal-doped PBA to enhance catalytic performance via a single synergistic enhancement mechanism. Moreover, current synthesis of metal-doped PBA suffers from strict conditions and complex procedures. Herein, a novel V-doped PBA nanozyme (V-PBA@V2C) with a binding site for organophosphorus pesticides (OPs) was rationally designed via a "contrarian strategy". During the assembly, acid-unstable V2C was innovatively employed as a carrier, reductant, and V source, transforming its inherent acid-instability into a functional advantage for one-step synthesis of V-PBA@V2C. The peroxidase-like activity and photothermal property of V-PBA@V2C were significantly higher than the sum of their individual counterparts, exerting dual synergistic enhancement effects. This synergy originated from V-Fe pairs (V4+/V5+ and Fe2+/Fe3+) present in both V2C and V-PBA as well as within V-PBA structure. Density functional theory calculations revealed that the enhanced catalytic activity of V-PBA@V2C stemmed from low energy barriers for •OH generation. Additionally, its V site exhibited strong binding ability toward OPs, avoiding the need for biological enzymes. In the presence of trichlorfon (TCF, a typical OPs), it would be rapidly captured by V-PBA@V2C and form a V-O-P bond, thereby reducing the affinity of V-PBA@V2C for H2O2. Compared with previous methods, the developed method achieved lower detection limits of 0.0528 ng mL-1 (colorimetric) and 0.612 ng mL-1 (photothermal), respectively. The present study provides novel inspiration for constructing a multifunctional probe for binding response and ultrasensitive detection of OPs.