A single-atom nanozyme-enabled strategy for rapid, visual, and real-time detection of polystyrene nanoplastics in water

Polystyrene nanoplastics (PSNPs) in water environment have become a critical issue to ecosystems and human health due to their small sizes, easier diffusion and higher hazard. It is an urgent need to develop an efficient, rapid, and on-site detection strategy for PSNPs. A single-atom nanozyme of zeolitic imidazolate framework (ZIF-FeSAN) was prepared using hemoglobin as template and Fe-source. ZIF-FeSAN possessed porous structure, a high surface area (994.91 m2/g), and maximumly exposed Fe atoms, resulting in a high peroxidase (POD)-like activity. ZIF-FeSAN exhibited excellent adsorption capability (83.46 mg/g, 10 min) for PSNPs via the electrostatic and π-π interactions. After adsorption of PSNPs, the active centers of Fe atom were shielded with a great decreasing of POD-like activity. Given the ‘on-off’ effect of POD-like activity, a ZIF-FeSAN colorimetric sensor was developed for PSNPs (20, 30, 50, 100, and 150 nm) detection. The limit of detection (LOD) was 0.212, 4.544, 7.624, 16.955, and 24.171 mg/L for 20, 30, 50, 100, and 150 nm, respectively. Meanwhile, a smartphone-assisted ZIF-FeSAN platform was designed to rapid, on-site, and visual detection of PSNPs, and the corresponding LODs were 0.851, 17.564, 34.554, 67.254, and 76.124 mg/L, respectively. The ZIF-FeSAN-based strategies have practical application in water samples due to high satisfactory recoveries (91.47–108.12 %) and good selectivity. This proof-of-concept study paves the way toward the on-site, rapid, and visual quantitative detection of PSNPs in water environment with avoiding the use of large and expensive instruments. [Display omitted] •A single-atom nanozyme (ZIF-FeSAN) was prepared by loading of Hb into ZIF-8.•ZIF-FeSAN showed excellent POD-like activity and adsorption capability for PSNPs.•Multiscale PSNPs can be detected using ZIF-FeSAN as a colorimetric sensor.•A smartphone-assisted ZIF-FeSAN platform was developed for PSNPs detection.