Luminous polystyrene upconverted nanoparticles to visualize the traces of nanoplastics in a vegetable plant†

In light of the growing use of plastics, assessing their impact on edible plants is essential for environmental preservation and food security. Researchers have employed various traditional fluorescence labeling methods to visualize nanoplastic traces in plants. However, these techniques are hindered by various limitations, such as shallow penetration depth, high background noise, and interference from autofluorescence, which compromise their accuracy and applicability in studying nanoplastic behavior in plant systems. This study utilized luminous upconverted labeled polystyrene nanoparticles (PS@NaYF₄:Yb⁺³/Er⁺³) to visualize nanoparticle uptake and accumulation in komatsuna (Brassica rapa var. perviridis) under a 980 nm near-infrared laser. Results from stereomicroscopy, scanning electron microscopy, Z-depth coding, and three-dimensional visualization confirm the accumulation of polystyrene nanoparticles (PS-NPs) in the plant, not only in the roots but also in edible parts. This accumulation led to a 33.18% reduction in fresh yield and a 19.05% reduction in dry yield. Our findings highlight that labeling PS-NPs with α-NaYF₄:Yb⁺³/Er⁺³ offers an innovative approach for studying nanoplastic uptake and translocation behavior in plants. Their high emission efficiency under near-infrared excitation and resistance to background fluorescence make them an excellent tool for tracking nanoplastics in complex biological and environmental systems, mitigating the drawbacks associated with traditional fluorescence methods.