Size-Resolved SERS Detection of Trace Polystyrene\nNanoplastics via Selective Electrosorption

Microplastics\nand nanoplastics are emerging contaminants that pose\na threat to the environment and human. Spectroscopic technologies\nare advantageous in analyzing nanoplastics, but it is challenging\nto selectively detect nanoplastics with different size thresholds.\nIn this work, the hyphenated method of electrosorption and surface-enhanced\nRaman spectroscopy (ES-SERS) was developed for the simple, rapid,\nand size-resolved analysis of trace polystyrene (PS) nanoplastics\nfrom 20 to 300 nm. A rough silver was used as both the working electrode\nfor electrosorption and the substrate for the SERS response. By applying\na positive electric potential to the rough silver, the PS nanoplastics\naccelerated toward the silver surface and were adsorbed tightly at\nthe SERS “hot spot” inside the rough silver nanostructure.\nThe proposed ES-SERS method achieved a detection limit of 100 ng/L\nfor 300 and 100 nm PS, 50 ng/L for 50 nm PS, and 30 ng/L for 20 nm\nPS nanoplastics. It is worth noting that smaller nanoplastics typically\nexhibit larger analytical enhancement factor values in ES-SERS. According\nto the difference in electromigration behavior of PS in various sizes,\nPS nanoplastics under a certain size can be selectively enriched and\ndetected by controlling the electrosorption time. The ES-SERS method\nwas successfully demonstrated for detecting nanoplastics released\nfrom the lids of disposable beverage cups. This work opens up new\npossibilities for size-resolved analysis of nanoplastics.