Nanostructured Raman substrates for the sensitive detection of submicrometer-sized plastic pollutants in water

We prepared novel Raman substrates for the sensitive detection of submicron-sized plastic spheres in water. Anisotropic nanostar dimer-embedded nanopore substrates were prepared for the efficient identification of submicron-sized plastic spheres by providing internal hot spots of electromagnetic fiel d enhancements at the tips of nanoparticles. Silver-coated gold nanostars (AuNSs@Ag) were inserted into anodized aluminu m oxide (AAO) nanopores for enhanced microplastic (MP) detection. We found that surface-enhanced Raman scattering (SERS) substrates of AuNSs@Ag@AAO yielded stronger signals at the same weight percentages for polystyrene MP particles with diameters as smal l as 0.4 mu m, whereas such behaviors could not be observed for larger MPs (diameters of 0.8 mu m, 2.3 mu m, and 4.8 mu m). The detection limit of the submicrometer-sized 0.4 mu m in ou r Raman measurements were estimated to be 0.005% (similar to 0.05 mg/g =50 ppm) along with a fast detection time of only a few min without any sample pretreatments. Ou r nano-sized dimensional matching substrates may provide a usef u l tool for the application of SERS substrates for submicrometer MP pollutants in water.