Researchers have demonstrated a surface-enhanced Raman spectroscopy (SERS) method capable of detecting polystyrene, polypropylene, and polyvinyl chloride microplastics at concentrations as low as 3 μg/mL in lake water and salt samples. The work combines a toluene-based dispersion step with an evaporation-induced self-assembly (EISA) process to create silver-nanoparticle filter-paper substrates, and uses thiophenol as a Raman reporter to quantify surface masking effects caused by microplastics.
The researchers prepared AgNP-coated filter papers using EISA and verified nanoparticle deposition via UV–vis spectroscopy and scanning electron microscopy. The SERS workflow relies on monitoring the 1066 cm⁻¹ thiophenol band, which decreases as microplastic concentration increases due to reduced plasmonic enhancement. Across polymers and particle sizes, the SERS intensity showed strong linear correlation with concentration.
To address the challenge of heterogeneous particle sizes, the study used toluene to disperse plastic fragments from 1 μm to several millimetres. The approach produced size-independent UV–vis and SERS responses for polystyrene ranging from 250 μm to 2.1 mm. Recovery tests in spiked lake water and salt yielded 90–110 percent recovery with no significant spectral interference from ions, organic pollutants, clay, algae, or bacteria.
The authors describe the protocol as a rapid, portable Raman-based approach that avoids more complex microplastic extraction workflows.
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