Dual-mode local enrichment and detection of small hazardous molecules and PS nanoplastics using a flexible AgNW SERS platform

초록

Surface-enhanced Raman scattering (SERS) holds great promise for point-of-sample diagnostics. However, its real-world application is hindered by diffusion limits and disparate physical scales of target analytes. In this study, we present a flexible Ag nanowire (AgNW)-based SERS platform comprising two independently prepared, target-specific surface variants for the detection of small hazardous molecules and polystyrene (PS) particles ranging from 100 nm to 1 μm. These scale-dependent limitations were addressed by combining target-specific surface engineering with localized physical enrichment. For small-molecule detection, sodium borohydride (NaBH4) treatment removed the polyvinylpyrrolidone (PVP) barrier and improved analyte access to the AgNW surface. Coupled with localized evaporation, this approach enabled detection of trinitrotoluene (TNT) and thiram down to the lowest tested concentrations of 4 × 10−10 M and 10−9 M, respectively. For PS nanoplastic detection, KI-based ligand exchange was applied to a separate AgNW membrane to form an iodide-modified surface with a low Raman background in the PS fingerprint region. Cross-condition measurements confirmed that the two surface treatments were not interchangeable: NaBH4 treatment was more effective for small-molecule SERS detection, whereas potassium iodide (KI) modification provided a more suitable spectroscopic environment for PS detection. Localized vacuum filtration increased PS confinement, and laser-induced photothermal softening/deformation enhanced contact between PS particles and the AgNW network. The platform enabled portable Raman measurements of molecular contaminants on solid surfaces and PS nanoplastics spiked into freshwater matrices. These results demonstrate a receptor-free, field-compatible strategy for localized enrichment and Raman detection of molecular and particulate contaminants using a common flexible AgNW platform. Copyright © 2026. Published by Elsevier B.V.

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