Surface-enhanced Raman spectroscopy for size-resolved microplastic detection in real-world samples using thiophenol labeling

Abstract

The widespread presence of plastic contamination in the environment presents a severe threat to human and animal health. This study introduces a toluene dispersion strategy for detecting microplastics of different sizes using surface-enhanced Raman spectroscopy (SERS). The evaporation-induced self-assembly (EISA) method was employed to prepare SERS substrates by incubating silver nanoparticles (AgNPs) of ∼40–60 nm with a microplastic solution containing polystyrene (250 μm, 2.1 mm), polypropylene (10–50 μm), and polyvinyl chloride (1–5 μm). SEM images and Raman spectroscopy confirmed the uniform decoration of AgNPs on filter paper substrates, with a relative standard deviation (RSD) of 8.22%. Thiophenol was used as a Raman reporter to monitor surface changes, showing a strong correlation (R² = 0.986–0.995) between its SERS signal and microplastic concentration in aqueous and real samples. This is the first time a toluene dispersion strategy has been integrated with EISA to achieve highly sensitive microplastic detection, reaching a limit of 0.001 mg mL⁻¹. The method was validated in real-world matrices, including lake water and salt samples, in the presence of interferents such as organic pollutants, inorganic ions, colloids, bio-organisms, and bisphenol A. This approach enables rapid detection of diverse microplastics in complex environmental samples.