Surface-enhanced Raman spectroscopy for the detection of microplastics

Detection of microplastics is still challenging due to limitations of current methods, instrumentation, and particle size. In this work, surface-enhanced Raman spectroscopy (SERS) was used to detect polystyrene (PS, 350 nm) and polyethylene (PE, 1-4 mu m) particles in pure water. Gold nanoparticles (Au NPs) of four different sizes were synthesized, characterized, and used as SERS active substrate for microplastic detection. The Au NPs obtained had a spherical shape with diameters of 33.2, 67.5, and 93.7 nm and an elliptical shape with shorter and longer diameters (nanorods) of 23.5 and 35.5 nm, respectively. The optimal conditions (volume ratio of sample to gold colloid, aggregating agent and its concentration) were determined. The efficient and stable SERS signals were observed on the PS microparticles, while the PE signal was difficult to obtain. The developed SERS method allows the detection of polystyrene microparticles at concentrations as low as 6.5 mu g mL-1. The described method can be a useful tool for the detection of microplastic pollutants of this particular size.