Pt–VS₂–MXene nanozyme for on-site pesticide and H₂O₂ sensing: Bridging computational insights and experiment

The excessive use of chlorpyrifos (CPS), a widely applied organophosphate pesticide, has caused serious environmental and food contamination, necessitating rapid and selective detection. Likewise, sensitive detection of H₂O₂ in living cells is crucial given its role in reactive oxygen species-mediated signalling, cell growth, and apoptosis. In this study, we synthesized peroxidase-mimetic nanozyme, Pt nanoparticles on edge-defect V₂C MXene decorated with VS₂ (VS₂–MXene) via chemical reduction and solvothermal processes for ultrasensitive CPS and H₂O₂ detection. The defect-engineered Pt–VS₂–MXene nanozyme exhibits markedly enhanced peroxidase-like activity (90.6 U mg⁻¹), exceeding Pt–VS₂ (40.5 U mg⁻¹), Pt–MXene (64.9 U mg⁻¹), and VS₂–MXene (26.8 U mg⁻¹), and substantially outperforming conventional nanozymes. Taking into account the ability of CPS to inhibit the peroxidase-like activity of Pt–VS₂–MXene and suppressing its catalytic oxidation of chromogenic 3,3′,5,5′-tetramethylbenzidine (TMB), we constructed a smartphone-integrated paper-based analytical device (PAD) for real-time CPS detection. The PAD sensor enables ultrafast (∼3 min), visual, and on-site CPS quantification, achieving a detection limit of 0.64 nM with a broad linear range of 10–140 nM, and excellent recovery of 105.2 %–108.2 % in real wastewater samples. Additionally, Pt–VS₂–MXene exhibits exceptional catalytic activity, with a strong affinity for TMB (Kₘ = 0.0231 mM, Vₘₐₓ = 0.169 µM s⁻¹), enabling ultra-sensitive H₂O₂ detection (LOD = 0.08 nM) with the wide linear range of 10–900 nM and real-time monitoring of H₂O₂ secretion from HeLa cells. This work creates sensitive PADs that can be used in biosensing, environmental monitoring, and medical diagnostics.