In situ surface-enhanced Raman spectroscopy for detecting microplastics and nanoplastics in aquatic environments

The detection of microplastics and nanoplastics in the environment, especially plastic particles in aquatic environments in situ, still faces challenges due to the limitations of current methods, instruments and size of plastic particles. This paper evaluates the potential of surface-enhanced Raman spectroscopy for the analysis of microplastics and nanoplastics. The condition of different tests including the volume ratio of sample to silver colloid, the concentrations of NaCl, and the concentrations of the samples, are assessed for the study of microplastics and nanoplastics (polystyrene (PS), polyethylene (PE) and polypropylene (PP)) in pure water and seawater. A method based on SERS, that uses silver colloid as the active substrate, is developed for the qualitative analysis of microplastics and nanoplastics in aquatic environments. The particle sizes of microplastics and nanoplastics include 100 nm, 500 nm and 10 μm. The Raman signals of microplastics and nanoplastics in pure water and seawater both show good enhancement efficiency. The optimal enhancement factor is 4 × 10⁴. The SERS-based detection method overcomes the limitations of microplastics and nanoplastics in liquids and can detect 100 nm plastics down to 40 μg/mL. It provides more possibility for the rapid detection of microplastics and nanoplastics in aquatic environments in the future.