Colorimetric detection of organophosphorus pesticides based on Nb₂CT_x MXene self-reducing PdPt nanozyme integrated with hydrogel and smartphone

The extensive usage of organophosphate pesticides (OPs) has posed severe harm to human health and environmental system, but achieving highly effective and on-site detection is still a great challenge. In this work, a novel nanozyme Nb₂CT_x MXene/bimetallic PdPt (Nb₂CT_x@PdPt) was synthesized firstly through a simple self-reduction method, and the results show that the as-prepared Nb₂CT_x@PdPt nanozyme exhibits outstanding peroxidase-like activity. Interestingly, the nanozyme activity of Nb₂CT_x@PdPt is restrained remarkably in the presence of acetylcholine chloride and acetylcholinesterase while it can be restored through the addition of OPs (selecting glyphosate as a model). Based on this phenomenon, a sensitive colorimetric assay coupled with hydrogel and smartphone for OPs was then constructed. After optimizing various conditions, the designed sensing platform can achieve stable, rapid, and sensitive on-site detection for OPs, showing superior sensing performances: a wide linearity of 1.0 ng mL⁻¹–1.0 µg mL⁻¹ and low detection limit of 0.419 ng mL⁻¹.