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Ag-iPyramidSERS Enables Single-Particle Detectionof Sub-200 nm Nanoplastics in Real Samples
Summary
Scientists have developed a new silver-coated sensor that can detect and identify individual plastic particles smaller than 200 nanometers, far tinier than a human hair, in real-world samples like rainwater and food containers. This matters because these ultra-tiny nanoplastics are small enough to potentially slip past the body's natural defenses and enter cells, but until now they've been extremely hard to spot and measure accurately. This new tool could help researchers better track exactly how much of this smallest, most concerning plastic pollution is in our environment and food supply.
Abstract The detection of nanoplastics smaller than 200 nm is critical because of their potential to cross biological barriers, yet it remains a significant analytical challenge in complex environmental matrices due to weak signals and matrix interference. Here, we developed an ordered silver-coated inverted pyramid array, termed the Ag-iPyramid substrate, as a reproducible surface-enhanced Raman scattering (SERS) platform for high-fidelity single-particle analysis of sub-200 nm nanoplastics. Systematic comparisons showed that Ag-iPyramid produced substantially higher signal-to-noise ratios, apparent single-particle enhancement ratios, and spectral matching scores than Au- and Cu-coated counterparts. Finite-difference time-domain simulations further showed that Ag generated the strongest local electric-field confinement within the inverted-pyramid cavity, consistent with the experimental performance ranking of Ag > Au > Cu. Beyond SERS enhancement, the Ag-iPyramid platform enabled high-quality detection of individual 100 nm polystyrene (PS) nanoplastics. When applied to real samples, the platform identified PS nanoplastics released from disposable food containers with a minimum Feret diameter of ∼140 nm and topographical heights of ∼22–45 nm. In authentic rainwater, the platform further resolved a polyethylene (PE) particle, a nylon-like nanoplastic (∼188 nm), and polyethylene-like (PE-like) particles in the sub-150 nm size range. These results demonstrate that Ag-iPyramid provides a robust strategy for the single-particle characterization of sub-200 nm plastics, bridging a crucial gap in monitoring the smallest and potentially most hazardous fraction of plastic pollution.