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Capturing, enriching and detecting nanoplastics in water based on optical manipulation, surface-enhanced Raman scattering and microfluidics
Summary
Scientists built an optical manipulation and surface-enhanced Raman scattering system using gold nanoparticle stacks to simultaneously capture, enrich, and detect nanoplastics in natural water at concentrations as low as 150 ng/L for polystyrene, successfully quantifying nanoplastics across river, mariculture, and beach water samples. The technique fills a critical measurement gap for nanoplastics, enabling reliable concentration monitoring in environments where these particles are otherwise nearly impossible to detect and quantify.
Aqueous concentrations of nanoplastics are critical for their risk assessment. Here we developed an optical manipulation and surface-enhanced Raman scattering set-up to capture, enrich and detect nanoplastics in aquatic environments. A small-sized (20 µm) gold nanoparticle stack was used to design a gold nanoparticle stack/polylactic acid optical tweezer, and individual nanoplastics were precisely manipulated. A large-sized (80 µm) gold nanoparticle stack enabled massive enrichment of nanoplastics, and high enrichment recoveries (for example, 89.3–94.3% for polystyrene) and low limits of detection (for example, 150 ng l−1 for polystyrene) of nanoplastics were achieved. Moreover, interference from natural organic matter was eliminated by adding a cleaning step before detection. The nanoplastics in natural waters (required volume, ≤7.2 ml) were thus successfully enriched and analysed, with determined concentrations of polystyrene nanoplastics of 6.5–8.5, 1.4–1.8 and 0.7–1.0 μg l−1 for water samples from a river, a mariculture farm and a beach, respectively. This newly developed optical manipulation–surface-enhanced Raman scattering approach is able to simultaneously enrich and detect nanoplastics in natural waters. The use of an optical manipulation set-up combined with the high sensitivity of surface-enhanced Raman spectroscopy allows the simultaneous enrichment and detection of nanoplastics. This technique has great potential for the analysis of trace amounts of nanoplastics in natural waters.