Polyoxometalate-Based Nanozyme with Oxidase-Mimic Activity for Point-of-Care Perfluorooctane Sulfonate Detection with Colorimetry

Perfluorooctane sulfonate (PFOS) is a burgeoning organic pollutant, which has attracted increasing concern. Due to its high toxicity, bioaccumulation, and damage to physiological systems, an efficient PFOS detection method is required. This study develops a new point-of-care PFOS detection method based on nanozymes and smart mobile phone. Notably, [(CH₃)₂NH₂]V₃O₇, a polyoxometalate (POM) nanozyme is synthesized, which shows remarkable oxidase-mimic activity with K_m 0.105 mM and V_max 3.84 × 10⁻⁸ M s⁻¹. Mechanism study confirms ·OH and ·O₂⁻ contribute greatly in oxidase-mimic process. Density function theory (DFT) calculation illustrates the excellent oxidase-mimic activity originates the intensive adsorption toward O₂. POM nanozyme can prompt the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) and generates blue ox-TMB. The color of blue ox-TMB can be faded by PFOS. Based on this, a visible colorimetry is developed for PFOS detection with low limit of detection (LOD) 0.46 μM. When employed for PFOS detection in tap water, river water, and lake water, this colorimetry receives favorable results. The work not only opens a new platform for POM nanozymes but also develops an efficient technique for PFOS detection in real water samples.